W

ABB

review
ABB is at the forefront of photovoltaics 6
Maintaining the balance of the grid 20
Automation for solar 38
Solar pumps in irrigation 50

Solar power

2 | 15en

The corporate
technical journal

From being an experimental technology just some years ago,solar energy has gone through a stunning learning curve andis now able to compete without subsidies in an increasing
number of markets. Solar panels have become a common sighton buildings and ground installations such as the Totana plantnear Murcia (Spain) shown on the front cover of this edition of
ABB Review. This installation was delivered by ABB andproduces 2.2 GWh/year.
At the time of press, the world’s first solar-powered airplane,
Solar Impulse 2, was attempting to fly around the world.
The plane is shown here and on page 5, and the project ispresented in “A soaring vision” on page 16.

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ABB review 2|15

Contents

The solar
challenge

Technologies
for solar

Trends andsolutions6

From source to socket
ABB is at the forefront of photovoltaics

10

A place in the sun
Challenges and perspectives for the future of solar

16

A soaring vision
Propelled only by the sun’s energy, the airplane Solar Impulse
2 demonstrates the promise of alternatives to fossil fuel20

Balancing act
Microgrid optimization control stabilizes production in solar
and hybrid microgrids

27

A bright future
Energy storage transforms the solar paradigm

33

Evolving solutions
Technology trends and design targets for next-generation
photovoltaic inverters

38

Life-cycle automation and services
A holistic approach to photovoltaic plant automation,and operation and maintenance

43

Putting it all together
Integrating distributed renewable energies into the grid50

A growing need
Affordable irrigation with ABB’s solar pump drive

53

Transforming revenue
ABB’s technology cuts transformer losses

58

Next-generation components
Advanced low-voltage components for next-generation
1,500 V DC utility-scale PV solar applications

60

Self generation
Photovoltaics play an essential role in ABB’s Active Site­t echnology

64

Steady as a rock
Two PCS100 AVC products now designed for different
applications

68

Safe and powerful
Dry transformers for subtransmission

Contents­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3

Editorial

ABB and solar energy

Dear Reader,
In September 2014, ABB presented its Next
Level Strategy, charting the company’s plansfor growth for the period 2015 to 2020. An
important part of this strategy is a commitment to ecologically sustainable technologies.

Claes Rytoft

Sustainability can be approached fromnumerous angles, ranging from choice ofmaterials across energy efficiency to humansafety. ABB’s R&D activities are working on
all of these aspects. The present issue of
ABB Review, however, focusses on one
particular and highly visible contribution tosustainability in energy: photovoltaics.
Photovoltaics is a rapidly growing part of the
global energy mix. It is inherently scalable,
clean, and is under favorable conditions
already able to compete without subsidies.
Although ABB does not manufacture theactual photovoltaic panels, the company
offers all other parts of the value chain
ranging across inverters, transformers,
protection and control and is proud to be theonly company able to supply this complete
range. ABB’s position was further consolidated by the acquisition of the company,
Power One, in 2013.

chain. Besides the more mainstream articles
looking at different contributions to andaspects of grid connectivity, some moreunorthodox applications are also covered,such as irrigation using solar powered
pumps. The least orthodox of photovoltaic
applications is an airplane. ABB is proud tobe part of the Solar Impulse team, whose
experimental plane is at the time of writing
making a journey around the world powered
entirely by solar-generated electricity.
Photovoltaics has come a long way from thelargely experimental technology it was only
some years ago. I trust that this edition of
ABB Review will present you with insights andfood for thought on this exciting source ofenergy and how it can be harnessed, connected to the grid and integrated with otherforms of generation.
I would like to use this opportunity to remind
you that besides the print version, ABB
Review is available electronically, both as a
pdf and as an app for tablet devices. Please
visit www.abb.com/abbreview for more
information.
Enjoy your readingThis issue of ABB Review features an interview with Michael Liebreich, chairman andfounder of Bloomberg New Energy andleading expert on photovoltaics, who thoughtprovokingly presents his vision of the futureof the technology and what it will take to
get there.
The subsequent articles look at a selection of
the numerous products and technologies
ABB offers to support the photovoltaic value­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4

ABB review 2|15

Claes Rytoft
Chief Technology Officer andGroup Senior Vice President
ABB GroupEditorial­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5

Fromsource tosocket
ABB is at the forefront of photovoltaics
ALEX LEVRAN – Over the past 10 years, global photovoltaic capacity has grown

at a steady double-digit rate. The worldwide installed base has expanded
more than tenfold from approximately 15 GW in 2008 to above 170 GW at theend of 2014. In 2014, total annual investment exceeded $ 83 billion. And thistrend is set to continue: ABB expects that in the next three years the worldwide installed base of solar power systems will surpass 400 GW.

Title picture
An ABB field service engineer at the Apex Nevada
Solar facility, near Las Vegas, NV, United States.

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From source to socket­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7

1 The PV market continues to experience solid growth with a shift in drivers.

Total global PV installed capacity

450 GW

More thandoubleHistorical drivers– Direct incentives– Renewable energy targets– Environmental concerns
180 GW
More thantenfold
increase
15 GW
2008

CAGR
(compoundaverage growthrate) from 2014
to 2018 at 25
percent
2014

Current drivers– Increasing power
demand in emerging
economies– Balanced energy mix– Preservation of fossil
fuels for export– Energy independence– Access to electricity– Grid parity– Economic viability

2018

Sources: IEA, Bloomberg New Energy Finance, European PV Industry AssociationIn its early years, expansion of the photovoltaic market was fueled by government incentives and subsidies, particularly in Europe where governments
set renewable energy targets as a percentage of the total generated energy.
The targets were designed to enablenon-carbon-emitting sources to displacecarbon-emitting generation from the energy supply, thus reducing overall carbon
emissions ➔ 1.

Market maturity
With the market now maturing, government incentives will increasingly be displaced by the technology’s inherent competitiveness as the prime driver of thesector’s continuing growth. Over the past
five years, the cost of installed solar power systems has declined by over 70 percent. The leveled cost of energy (LCOE)
for solar electric power in many parts of
the world has fallen to at least so-called
grid parity 1 levels, if not further.
Europe was the first region to witness alarge-scale emergence of photovoltaic
power, thanks to feed-in tariffs (FIT) combined with subsidies to support the fledgling technology.
In the past few years, markets havegrown very quickly in the United States,
China, Japan, India and Australia. Indus-­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­8

ABB review 2|15

try expectations are that in the near­future, market expansion will also occur
in emerging countries in the Middle East,
Africa and South America. The global­solar market is now well established in
the domain of residential, commercial
roof-top, and utility-scale ground-installed applications.

more than 1.2 GW of solar power in 14
different countries. ABB has over 350 MWof solar power under full operation andmaintenance (O&M) contracts at 55 different sites. With the additional acquisition of Powercorp, the company is deliv-

Over the past five years, thecost of installed solar powersystems has declined by over
70 per­c ent.

Although steep priceerosion has been
adversely impacting profitability, there
are clear signs thatthe industry is migrating toward profitable growth throughglobal expansion.

ABB’s commitment to this sector aligns
with the vision of its group CEO, Ulrich
Spiesshofer: “We need to run the world
without consuming the earth.”
A complete range
Thanks to the 2013 acquisition of PowerOne, the world’s second largest inverter
manufacturer, ABB now has an installedbase of over 18.5 GW of solar energy
supplied by over 1.5 million photovoltaic
inverters. In addition, the company has
installed 66 full power plants delivering

Footnote
1 Grid parity is understood as the equivalent priceper unit of electricity that could be bought fromthe local utility.

ering leading edge technology for the
integration of renewable energy into
micro­grids.
ABB is the only company that provides acomplete range of electrical components
connecting photovoltaic panels to thegrid. The company has a broad portfolio
of products, solutions and services that
support all three market segments: residential, commercial and utility on a global
scale.
For residential and commercial markets,
ABB has developed a global low-voltage
product portfolio that includes combiner
boxes, AC and DC switches andbreakers, contactors, fuse disconnects,
current sensing, surge protection devices
and rapid shutdown, as well as energy
meters. The company has a global offering of single-phase and three-phase in-ABB is the only
company that provides a complete
range of electricalcomponents
connecting photovoltaic panels to
the grid.

2 ABB offers the most comprehensive value proposition in the solar industry.

Remote control and monitoring
Global sales and service

Grid connection and integration
Distribution
automation

EV charging

Solar pumpHybrid microgrids

Home & building
automation

Residential

Microgrid andoffgrid solutions

verters as well as a wide range of monitoring systems. ABB’s portfolio includes
storage platforms for the fulfillment ofhousehold energy self-sufficiency andinde­pendency.
For global utility markets, ABB offers solar inverters; medium- and high-voltage
transformers; medium- and high-voltage
switchgear with medium-voltage reclosers and vacuum circuit breakers; andsubstations. The company also offers
high-voltage direct current (HVDC) transmission systems for the efficient transmission of power over long distances,and flexible AC transmission systems(FACTS) for reactive power support andactive power control. ABB offers a fullrange of battery energy storage solutions
from 25 kW to 70 MW and active voltage
regulation devices for medium- and highvoltage applications. In addition to the
products and components, the company
also delivers full engineering system design, electrical balance of plant and simulation capabilities.
ABB’s comprehensive monitoring systems include distribution grid automation, forecasting, load and demand planning solutions. The company offers total
life-cycle support at every stage for any
solar installation that includes tailoredservice contracts covering all equipment
and solutions. ABB strives to help customers achieve a maximum return on
investment through improved capacity,­
efficiency and reliability.

Battery energy
storage

Commercial

Utility

Grid-connected
solutions

ABB is also well positioned to address
the challenges posed by solar energy as
its penetration in energy systems continues to grow. The expanding installedbase of distributed generation in theworldwide solar market creates challenges for utilities to maintain stability of thegrid. The industry is seeing continued demand to upgrade grid connectivity standards. In addition, improving the stabilityof grid storage – both at distributed andcentralized levels – will become a very
important element in the near future.
The company is providing solutions andservices that will allow the solar industry
to continue to grow and flourish as ABB
expands its global reach  ➔ 2.

Alex LevranSolar Industry Segment Initiative
Camarillo, CA, United States
alex.levran@us.abb.com

From source to socket­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­9

A place inthe sunChallenges andperspectives for the
future of solar­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 0

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Michael Liebreich, Chairman of the advisory board and founderof Bloomberg New Energy Finance, discusses solar energy withABB Review.

This progress is not going to stop. Solar
power is now seeing costs in the 6 to
8 cents/kWh range for good projects,
before any subsidies. The cheapest we
have seen is 5.84 cents/kWh on a project
announced this year in Dubai. Solar electricity has moved from the era of
50 cents/kWh to 30 cents, to 20  cents,
to 10 cents and now below even that.

that one-third of the world’s energy
comes from coal, and yet the writing isabsolutely on the wall for the coal sector.
In the developed world we are seeing asurge of coal plant retirements, and in thedeveloping world the build rate is dropping away. By 2030 we think we will
be seeing net removal of coal generating
capacity, rather than additions.

Just to put those prices into perspective,
what are the comparable prices for nonrenewable sources?

Will the cost of solar power continue tofall, and if so, what are the implications?

Let us consider, for example, the UnitedStates. The price of electricity from natural gas there is low, around 6 cents/kWh;so at 8 cents/kWh, solar is not quite
competitive without subsidies. But apply
the investment tax credit and solar cancome down to 5 cents/kWh. Solar canalso help to manage the demand peakbecause it is almost ideally timed to meetthe needs of air conditioning. But of

ABB Review: The concept of deriving
electricity from sunlight has been aroundsince Becquerel, but only in the last decade or so has it taken a significant andgrowing share of the overall energy market. Is this just the beginning? What is
driving the ongoing changes?
Michael Liebreich: I started New Energy
Finance 11 years ago because I wasconvinced we were on the brink of aclean energy revolution. One of the main
reasons for my confidence was that wasthat I have an almost religious belief inexperience curves. The key clean energy
technologies – wind, solar, electric vehicle batteries – are all benefitting fromsteep experience curves, while conventional energy is limited by resource availability and environmental limits.
Another important game changer has
been the very low cost of controls andsoftware. Even if you go back 15 or 20
years, trying to manage a solar farm – oreven worse, a set of distributed solar
panels on rooftops – would have beenhugely expensive. You would have been
writing customized communication software and renting dedicated phone lines.
Now, of course, all that is Internet basedand costs next to nothing.

Experience curves
have been a massive driving force inadvancing clean
energies.
course you still need to meet your nighttime demand, as well as demand when
the weather is bad or during the winter.
Although we are talking about solar, it isalso worth noting that wind energy isseeing unsubsidized prices in the UnitedStates at 4 cents/kWh – so cheaper eventhan gas-produced electricity.
This poses a real challenge for coal. If
you’ve got a fully depreciated coal-fired
power station, and you allow it to chuckout whatever pollutants it wants, then
you can produce at prices of 3 or 4 cents/
kWh. But as soon as you tighten that up,
even if you just get rid of the SOx andNOx, coal can be 5 to 8 cents/kWh, andthat is before you take into account any
climate costs. But then, if you include thecosts of asthma caused by coal dust andparticulates, the cost of mercury, the costof damage to roads from coal trucks andso on, coal is completely uncompetitive.
It’s a very bizarre and unstable situation

The 6 to 8 cents/kWh of today will continue to fall to even lower levels as theindustry expands – we think it will hit
4 cents/kWh between 2030 and 2040,
but it could be sooner – until we exponentially approach almost free power at
the point of generation.
Of course you then have to get all thatcheap, clean power to the user – at theexact time it is needed. On a system level there will have to be major changes
when you look at the architecture required to integrate wind and solar power.
This includes demand management, interconnections and storage. We are seeing the emergence of a completely different type of electricity system, built
around flexibility. Frankly it plays to thestrength of ABB to build those systems.
In terms of the total solar power that we
can commercially harness, is there an
upper limit?
It is very early to talk about hitting a limit
as we’re still at a very low penetration ofsolar, less than 1 percent of global electricity. Additionally electricity is only a minority of overall power consumed. Thereis also transportation and heat, whether
in homes, commercial property or industrial processes. Of course electricity as awhole is penetrating these other areas,
but it still only accounts for less than
one-third of total energy demand. So weare far from any sort of saturation interms of what the system can absorb.
As the percentage of variable renewable
power grows, my working hypothesis isthat engineers are incredibly brilliant andthere is no fundamental upper limit. If wekeep on investing in storage, interconnection between systems and demand
management, we can continue adding
capacity. For example, everybody is very

A place in the sun­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 1

1 Lithium-ion EV battery experience curve compared with solar PV experience curve
100

Historical price ($/W, $/Wh)

The driver for solar
investment can nolonger be idealism
about the environment and the tools
to achieve it canno longer be subsidies.

1976

m = 24.3%
Crystalline Si PV
module101998

m = 21.6%

2004

1988

2008

2010
1

2014
H1 2014
Li-ion EV battery
pack

0.1
1

10

100

1,000

10,000100,000

1,000,000

10,000,000

Cumulative production (MW, MWh)

Sources: Bloomberg New Energy Finance Note, Maycock, Battery University, MIIT

excited about the concept of storage.
They’ve all discovered that the sun
doesn’t shine at night and therefore weneed batteries. Batteries will go throughthe same experience curve that solar has
seen, but right now they are still costly ➔ 1. So is that bad news for solar?
Well, first of all, there is a lot more electricity demand during the day than during
the night. You can match a huge amountof solar power to daytime demand, andin most markets that means building out
solar for many more years without having
to worry about nighttime. Then, before
having to add day-night storage, you canshift demand around, using demand
management strategies or even thermal
storage. For example, you could chill
your freezers and refrigerators during the
day when the sun is shining and let themcoast through at night.
From the ABB perspective, when looking
at cost reductions, there is so much potential that can be unlocked throughlooking at the whole electricity delivery
chain as a system rather than as a collection of individual products. ABB is in
the unique position to be able to offer theentire value chain.
Where do you see the major challenges andchanges to face solar power in the next
­decade (both technological and policy)?
The driver can no longer be green idealism and the tools to achieve it can nolonger be subsidies. The motivationneeds to be improved system performance, in terms of cost, pollution andresilience, and the means have to be­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 2

ABB review 2|15

more nuanced. The transition to a greater usage of solar electricity has to be acceptable to the pockets of consumers
and of industry ➔ 2.
If you look, for example, at the German
feed-in tariffs, they sent a very clear signal and were very effective in advancing
solar. The problem was that they removed price signals from the electricity
market, and thus removed price as adriver of competition for developers andtechnology providers. What happens insuch situations is that people focus on
lobbying and winning business throughmechanisms other than price competition. And unsurprisingly, that’s not an efficient way to do it. Ultimately it costs toomuch and something has to change. In
Spain the reaction to this caused retroactive changes that stopped the market
dead in its tracks. Even Germany is shifting to reverse auctions after it became
clear high power costs were affecting
Germany’s competitiveness. Everybody
is still very committed to Energiewende(Energy Transition), but the initial feed-in
structures are being replaced by something more economically efficient. In the
United Kingdom we are introducing acontract for difference (CFD) system requiring reverse auctions – which has already proven to bring the price down.
So government subsidy and support isgood at the start-up stage, but should
be reduced later?
Absolutely. When solar is less than one
percent of the electricity market – and I
hate to say this – but if you share thatextra cost over the rest of the electricity

market, then it doesn’t hurt much and it
doesn’t matter. But if solar advances to3, 5 or even 12 percent, which is easily
achievable in sunny countries, then you
can no longer afford that level of waste.
As for industry, even if you are in a market with excessive subsidy levels, it’s­always better to be a low-cost provider:
It is the only way you can really control
your destiny and not be at the mercy ofpolicy changes.
If governments should not subsidize,what role should they be playing?
Their primary role should be concernedwith energy security – making sure thatthe system doesn’t fall over – whether
that’s because of technical instability or
because of geopolitics. After that governments must support where necessary
but not beyond. They shouldn’t try toforce the incumbent energy providers tolead the transition to clean energy (butshould let them do it if they want to).
They should open up the market to new
players and new business models. If you
look at Germany, where solar has progressed most rapidly, the big utilities
own 80 or 90 percent of gas, coal andnuclear, but only 5 to 10 percent of renewable energy. Why? Because incumbents didn’t have the incentive to go in
and do it. You see the same in California.
The utilities are responding and trying tocatch up, but they are only doing it because there is a competitive threat fromnew players. So governments need toensure new players have access to themarket. An example is the capacity market. If you put into place a capacity mar-

Solar is betterand cheaper thankerosene and cancharge your phone
as well as giving
you light.

2 Investment in solar power80$ (billion)

60
40
20
0
2011

2012

Asset
finance2013
Publicmarkets

2014
Venture &equitySources: Bloomberg New Energy Finance Note
Source: Bloomberg New Energy Financeket, you need to ensure you are notkeeping out new players or solutions,which is very hard.
Are the main challenges facing the solar
industry largely universal, or are there
significant differences between countries
and continents?
Solar is moving beyond its traditionalcore markets such as Germany, Japanand the United States and into places
such as Chile, South Africa, North Africa
and Thailand. Solar is now really happening all around the world. As prices
are coming down, we are seeing a lot ofplaces – especially in developing countries – that traditionally have high prices

One of these is electricity subsidies. In
places like India you are looking at artificially depressed electricity prices of 3, 4
or 5 cents. At that level, you can’t recover the costs of building capacity. Anotherbarrier is regulatory, protecting incumbent energy providers and their businessmodels. A third barrier is about the physical limitations on the grid. Are we going
to produce too much electricity when it’ssunny and not enough when it isn’t?
Where do you see the future of solar PV?
In distributed rooftop installations, or inlarge ground-mounted PV power plants?
The answer is both. I don’t think we needto prioritize one over the other.
We will get to thepoint that we will
have a very highpenetration of rooftop installations at
grid parity. But willthat cover all electricity demand? No. The area of solar
rooftops is too small to meet all power
demand. There will always be a wholesalemarket for electricity.

Governments must support
where necessary but notbeyond.
for electricity and low supply reliability.
Solar is suddenly becoming very attractive and competitive in such markets.
This is where the energy access piececomes in. You can easily install solar inlocations that were previously off-grid.
Solar is better and cheaper than kerosene and can charge your phone as wellas giving you light. Solar is an enabler ofrural development, especially in countries that were traditionally forced to import fossil fuels using expensive foreign
currencies ➔ 3.
What are the main remaining barriers to
the further spread of solar energy?

With rooftop generation growing nevertheless, we sometimes hear such terms
as grid defection – meaning people willseek to become autonomous in terms ofenergy and remove their grid connection.
Is grid defection a threat to utilities?
I’m not a big believer in grid defection. It
will happen in some very niche situations
such as very remote locations in the Australian Outback or libertarians who wantto live by themselves. There are a number of reasons why most users will want
to stay connected to the grid.
The first is, I have solar panels on myown roof, but when I put the dishwasher
and kettle on at the same time, I’ve got
to source that power from somewhere.
Retaining the connection to the grid enables me to meet those peaks – as wellas those days when there is no sun –more cheaply than investing in hugeamounts of storage.
Second, if I have correctly sized the installation to meet my needs during themost demanding time of year, I’m going
to be generating a big surplus during therest of the year. Why not sell it? But forthat I still need a wire. Third, what happens if my system fails? The grid canprovide backup.
Finally, if you go off grid, your systemneeds to be a completely self-managed
mini-grid, and that’s not easy. I want myutility to help me manage it, to tell me
when I need to clean my solar panels ormaintain my fuel cell, and so on. So evenfor a well-designed system there aremany services ranging from maintenanceto supply security that a utility can provide. The utility can charge clients forthese services, but not for bulk electricity.
So what we are going to see is load defection, meaning the user buys less power from the utility, both because of energy efficiency and because he or she
self-generates power. Utilities will change
their business model from charging forelectricity to charging for services. If they

A place in the sun­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 3

3 PV new build per annum

70

70

Rest of world
61.0

India

60

China

China

30

WesternEurope

20

18.2

6.6

7.7

2008

2009

28.4

45.0

Japan

40.3

40

East Europe

30

WesternEurope

20

18.2

GW

East Europe

GW

40

United States

50

45.0

Japan

69.7

61.4

India

60

United States

50

10

61.3

55.5

67.9

Rest of world

30.7

10

0

6.6

7.7

2008

2009

40.3

28.4

30.7

0
2010

2011

2012

2013

2014

2015

2016

2017

3a PV new build by year, historical and forecast to 2017 (conservative)

2010

2011

2012

2013

2014

2015

2016

2017

3b PV new build by year, historical and forecast to 2017 (optimistic)

Source: Bloomberg New Energy FinanceNote: A conservative and optimistic forecast has been developed for each country. It is unlikely that all countries will come in at the conservative or optimistic end, so for the global forecast,conservative is the sum of conservative country forecasts + 25% of the sum of optimistic-conservative forecasts. Global optimistic forecast is the sum of conservative country forecasts + 75%
of the sum of optimistic-conservative forecasts.

don’t do this, then yes, you’ll see grid
defection.
Looking beyond the scope of solar for a
moment and considering other renewable energies, be they wind, hydro, biomass, geothermal or even some of themore experimental forms such as wave
and tidal power, do you see these ascompetitors or partners of solar?
They are very much partners. We need torecognize the value of electricity in termsof when it can be delivered. Solar is fairly
readily available during the day, but leaves
an important supply gap in the evening,
meaning you’ve got to look at what demand it can best meet. Hydro is dispatchable. You might even be able to use
pumped storage, but even if you can’t,
you can collect water in a reservoir during
the day and use it during the night, or during a few weeks when there’s a wind lull.
Geothermal power is very interesting
where you can do it. Biogas is working
quite well. Tidal power is very predictable, though expensive. Wave power is
at a much earlier stage of its development. I’m skeptical about the ability todrive costs down to levels anywhereclose to what we see with solar andwind. You have to put an enormous
amount of concrete and steel into thesea for a relatively modest power yield.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 4

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Where do you see the main strengthsof ABB in serving and advancing solar
energy?
It is all about ABB’s extraordinary
strength in engineering. So first of all weare talking about leading-edge components, ranging from photovoltaic inver-Utilities will change
their business model from charging forelectricity to charging for services.
tors and low-voltage products to highvoltage direct current (HVDC) andcommunication equipment. ABB has
huge technological competence at the
product level.
Secondly, I see ABB’s competence at thesystem level. Whether you’re talking
about load balancing, designing a minigrid or providing other system-level services, there are relatively few players out
there who are really able to deliver that.
For example, startups might be very
good at providing one component but
will find it very difficult to provide a higher
level of knowledge, reassurance and­d istributed services across a city, grid or
multiple grids.

The third element lies in the company’s
reputation. One of the challenges is thatthe mainstream – be it the businessreader of the Financial Times or the energy ministries of medium-sized countries – is not, on the whole, up-to-dateabout the technology and its costs.
There is a knowledge lag. ABB has an
exceptional role to play in reassuring policy makers and decision makers thatclean energy is no longer about high-risk
pioneering technology, but about robust,
resilient, proven solutions.
Which is exactly what ABB Review isabout and why we are producing this­issue dedicated to solar.
To move on to a less mainstream topic,
ABB is supporting Solar Impulse 2, a solar-powered plane attempting to fly aroundthe world. Obviously aviation is not one ofthe primary fields of application of solar
energy, but do you think we will ever see acommercial solar-powered flight?
Obviously solar planes are not going to bea major target market for solar technology
any time soon. Solar Impulse is really an
exercise in pushing the boundaries oftechnology and also the boundaries of human thinking by saying to people, “Look,
this is possible.” And it is doing a great job.
Can it ever work as a commercial offering? Solar Impulse 2 is very slow. It is taking something like 15 hours to fly acrossEvery generation
had to win its
energy supply andwe had a period
where we almost
forgot that.
the Gulf of Arabia, 6 days to cross the
Pacific. But who knows? Maybe commercial freight flights, possibly configured asa drone or a blimp could take the entire
fuel costs out of the shipping equation.
Probably a better way to use solar to
power flights would be to use it to create
synthetic fuel, either through direct catalysis or from solar-powered electricity.
But who knows? Had you looked at­telecom companies in 1975, you wouldn ever have forecast Facebook, Skype­and so on. So I’ll rule nothing out.
Another form of transportation in whichsolar has a more direct part to play iselectric vehicles.
I’m very bullish about electric vehicles.
As I said earlier, I am a strong believer inthe experience curve. Electric-vehicle
batteries are seeing the same sort ofcost curve as photovoltaics. But having
said that, I don’t think we’re going to beseeing equally rapid penetration in all
segments and countries where we now
see combustion vehicles. The batteries
are a major cost factor and this favors
adoption in the sectors seeing the highest annual mileage, but range is an issue. So someone with a long daily commute is going to be a more attractive
target than someone using their car
e ither occasionally or for long random­
journeys to places where you don’t know
if you can get your battery charged.
Let us conclude this interview with something more philosophical: One interesting
consequence of solar power is that normal people are choosing to add PV panels
to their own houses and offices. Electricity
generation is no longer something that
happens in remote locations, of which we
as consumers have only a vague awareness, but has become something tangible. Do you think this is changing the way
we think about and value energy?

Absolutely. We easily take energy for
granted, but actually it has to be won,has to be converted, has to be delivered.
Each generation has to secure its energy
supply. It looks like as if are coming out
of a period in which we could almost forget that fact; everything was so easy.
The new technologies are making us
look afresh at how we win our energy,
look afresh at our rooftops, our garbage,
our insulation and so on. Energy is moving out of our deserts and ports, and into
our homes and our communities. I met
a chap in India who was selling solar­e nergy to local stalls in a village market.
Stallholders could for a few Rupees get
an LED lightbulb and a wire back to thischap’s battery, which he was recharging
every day with his solar panels. The stallholders were happy and the guy had created a good business. It was a fantastic
service provision and a fantastic innovation. But actually all he had done wasreinvent the electric utility.
It is also accelerating because the newtechnologies are building on each other.
This Indian entrepreneur could only create his business because of the interaction of LED and solar. If he had tried to
do it with a filament lightbulb, the solar
panel would have been so huge that hewouldn’t have fit on his roof. The revolution of solar technology is going to drive
the emergence of super-efficient appliances and vice versa. The Clean Energy
Ministerial launched the Global Lighting
and Energy Access Partnership prize(Global LEAP) for highly efficient appliances, and one of the first winners was a
television set that runs on just 6 W. That’s
less than a lightbulb.
Marshall McLuhan, the philosopher whocoined the phrase “the medium is themessage,” also said “the ‘message’ of
any medium or technology is the changeof scale or pace or pattern that it introduces into human affairs.” Well, it looks
like solar power and these other new
technologies carry an incredibly important message for us all.
Thank you for this interview and sharing
your enthusiasm with us.

Michael LiebreichMichael Liebreich is chairman of the advisoryboard and founder of Bloomberg New Energy
Finance, the world’s leading provider of
information on clean energy to investors,
energy companies and governments. He
leads a team of about 200 around the world,
just under half of them in London, comprising
journalists, researchers, analysts and sales
and marketing departments. Michael founded
the company as New Energy Finance in
2004, selling it to Bloomberg in 2009.
Michael is a frequent commentator in thepress, on TV and on radio on issues ofenergy, development and economics. He
serves on the UN Secretary General’sHigh-Level Group on Sustainable Energy for
All and formerly on the World Economic
Forum’s Global Agenda Council for the New
Energy Architecture. He is a Visiting Professor
at Imperial College London, Board Member ofTransport for London and Chairman of a
Medical Charity funding research oncolorectal illness.
Michael earned his MA in engineering from
Cambridge University, winning the Riccardo
Prize for Thermodynamics, and an MBA from
Harvard Graduate School of Business, where
he was a Harkness Fellow and Baker Scholar.
Michael Liebreich– Founder and Chairman of the Advisory 		
Board, Bloomberg New Energy Finance– Advisory Board Member, UN Sustainable
Energy for All– Founder, Finance for Resilience– Board Member, Transport for London– Visiting Professor, Imperial College Energy
Futures Lab– Chairman, St Mark’s Hospital Foundation

This interview was conducted for ABB Review by Erika
Velazquez, Alex Levran and Andreas Moglestue. For
inquiries please contact erika.velazquez@ch.abb.com

A place in the sun­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 5

A soaring vision
Propelled only by the sun’s energy, the airplane Solar Impulse 2
sets out to demonstrate the promise of alternatives to fossil fuel
ERIKA VELAZQUEZ – The attempted around-the-world journeyof a solar-powered plane is pushing the boundaries of energy
management and conversion. To demonstrate the enormous
potential of renewable energy and pioneering spirit, Swissaviators Bertrand Piccard and André Borschberg have built
the first-ever aircraft capable of using only solar energy to fly
both day and night, thus able to cross continents and oceans.
As a global leader for supplying technologies to enableenergy efficiency, sustainable transportation and renewable­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 6

ABB review 2|15

energy, ABB was a natural choice to form an innovationand technology alliance with the Solar Impulse project.
ABB brings its technical expertise to this attempted flightaround the world, which uses only energy supplied by aplane’s solar panels and onboard battery systems. ABB
engineers have overseen a multitude of technical challenges
that include improving control systems for ground operations,component testing, enhancing the battery systems andtroubleshooting throughout the journey.

© Solar Impulse | Anna Pizzolante | Rezo.ch
See more from ABB Review
Additional pictures and videos
from this article are available in
the ABB Review app.

A

BB and Solar Impulse formed
their alliance to advance ashared vision of decoupling
economic growth from environmental impact by increasing the useof renewable energy.
Borschberg and Piccard have been flying
increasingly ambitious solar-powered
missions to draw attention to the possibilities for clean energy. In 2013, they
made a record-setting journey acrossthe United States, from California to New
York, using their first ultralight aircraft
Solar Impulse 1. The plane, which had acruising speed of about 53 km/h, also
completed a 26-hour overnight flight in
2010, and flew from Switzerland to­M orocco in 2012.

Title picture
Solar Impulse 2 flying over Switzerland during
a test flight

The pilots unveiled Solar Impulse 2 inApril 2014. On its debut flight in Switzer-

During the day the solar cells recharge
four lithium batteries, thus assuring a
steady stream of
power for nonstop
flight day and night.

The cooperation andexchange of exper­t ise andexperience between ABB’s
engi­n eers and the Solar
Impulse team has enableda unique opportunity toshow­c ase renewable energy.
land in June 2014, the plane reached amaximum altitude of 1,680 m and flew at
an average ground speed of 55.6 km/h.

The latest journey
Solar Impulse 2began its attempted
35,000 km journeyaround the world
in March 2015 in
Abu Dhabi. By thetime the mission is
set to conclude in
Abu Dhabi in July
2015, the plane will
have made 12 stops – in Oman, India,
Myanmar, China, the United States, andeither North Africa or Europe ➔ 3.

The new carbon-fiber plane is covered in
17,248 solar cells that provide clean energy
to the aircraft’s four electric motors ➔ 1 – 2.

Flying at speeds between 50 and
100 km/h, the journey is anticipated totake 500 hours flight time, over the

A soaring vision­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 7

1 Solar Impulse 2 at a glance
The plane’s external dimensions feature a lengthof 21.85 m, a height of 6.4 m and a wingspan of
72 m. The wingspan, wider than a Boeing 747
jumbo jet, minimizes induced drag and provides
a maximum surface area for solar cells.
The frame of Solar Impulse 2 is constructed withlightweight, thin materials, such as carbon fiberand honeycomb sandwich panels that reduce theweight of a carbon layer from 80 g/m² to 25 g/m²,
only one-third as much as a sheet of printerpaper.
The plane’s upper wing surface is covered withhigh-efficiency solar cells and the lower surface
is constructed with a high-strength, flexible skin,an innovation borrowed from techniquesdeveloped by sail makers for racing boats
competing for the America’s Cup. The 140
carbon-fiber ribs are spaced at 50 cm intervals

course of five months, crossing four continents and two oceans.
Engineering
ABB’s engineers were able to bring specific know-how to the project in areas
such as testing procedures and protocols as well as specific knowledge ofpower electronics and cooling. Component testing was done for functionality,
temperature and pressure performance.
One responsibility of the ABB engineers
on the project was to improve the control
system for Solar Impulse’s balloon-likemobile hangar, which is used to housethe plane during unscheduled landings
or if a local airport cannot host the plane.
The mobile hangar is an inflatable structure made specifically for the plane, consisting of several modules that are thenconnected together and dragged overthe plane ➔ 4. Each module has a double
layer of fabric with ABB fans in between
that inflate the hangar.
Increased reliability was achieved by incorporating ABB relays and circuit breakers
into the existing system. The system wasmade redundant with a switchover unitthat is connected to an alternative power
supply. An upgrade was made in current
measuring relays that activate an alarm in
the event of a failure of any of the fans.
The ABB engineers also developed the
cockpit battery charger that is used tocharge an additional small lithium battery
located behind the pilot. The cockpit­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 8

ABB review 2|15

to give the wing its aerodynamic cross section
and also maintain its rigidity. The aircraft features
17,248 monocrystalline silicon solar cells, each
135 µm thick and mounted on the wings,
fuselage and horizontal tailplane, providing thebest compromise between lightness, flexibility
and efficiency.
Energy gained from the solar cells is stored inlithium polymer batteries optimized to have adensity of 260 Wh/kg.
The batteries are insulated by high-density foam
and mounted in the four engine nacelles, with asystem to control charging thresholds and temperature. Their total mass amounts to 633 kg or
just over one-quarter of the aircraft’s all-up weight.
The aircraft is equipped with four brushless,sensorless motors, each generating 13 kW

battery is used as an emergency power
supply for the plane’s avionics and powers the essential electronic devices (navigation, communication, etc.) in case ofelectric power loss in the plane. This important battery is also charged exclusively with sun power as well, before andduring the flight, and kept at a 100 per-Increased reliability
was achieved byincor­p orating ABBrelays and circuit
breakers into theexisting system.
cent charge over the long flight segments. If the plane is ever left without
solar power for the motors, the cockpit
battery enables communication and navigation, and all the electronics that help
fly the plane, as the plane can glide for along time after the engines are disabled.
ABB engineers were also involved in testing the plane’s electrical system, including certain aspects of the plane’s battery
management system and maximum power point tracking (MPPT) devices thatreap as much power as possible regardless of atmospheric conditions from thecollection of solar cells forming a solar
skin over the plane’s wings.

(17.4 hp), mounted below the wings and fittedwith a reduction gear limiting the rotation speedof a 4 m diameter, two-bladed propeller to
525 rpm. The entire system is 94 percent
efficient, setting a record for energy efficiency.
The plane climbs to 8,500 m during the day togather as much sun energy as possible, anddescends to 1,500 m at night in order to con­serve energy, coasting more like a glider, andtherefore using much less stored energy fromthe batteries than it would if it would keep a
constant altitude.
The aircraft flies at an average speed of 70 km/h,
with a takeoff speed of 44 km/h and has amaximum cruising altitude of 8,500 m. Minimum
speed is 36 km/h at sea level and 57 km/h at
maximum altitude. Maximum speed is 90 km/h at
sea level and 140 km/h at maximum altitude.

The plane’s eight MPPT devices are critical, since failure of just one during certain legs of the flight – for example, thefive-day, nonstop flight between China
and Hawaii – would make it impossible
to charge batteries enough during daylight while running the motors sufficiently
to reach maximum altitude.
Functional component testing to ensurethat all devices are fully operational before installation was a crucial aspect of
the ABB engineers’ involvement. For example, the plane’s warning panel, whichmonitors all devices for faults and triggers the annunciator panel and enables
the alarms to warn the pilot when there is
an issue with an onboard device, is madeup of over 1,000 components.
Initial testing showed that the board was
too sensitive to the relays’ mechanicalbounces. Follow-up debugging of the circuit required four days of work on the annunciator panel (from the entire electricaland propulsion team). Only after a stable
solution was designed, manufactured,and retested was the device mounted on
the plane. A working alarm system isabsolutely critical because it needs to­alert the pilot, who then might have only
10 seconds to react to save either his lifeor the mission. Testing was also conducted on the pilot monitoring devices thatmeasure pulse and oxygen level.
The last project undertaken was designing a media system that enhanced the
direct recording from the onboard cam-© Solar Impulse | Ackermann| Rezo.ch

2 Solar Impulse 2 is equipped with four brushless, sensorless motors mounted below the wings.

Southern Europe
or Northern Africa

Pacific
crossing

Pacific
crossing

Atlantic
crossing
Phoenix,
USA
Hawaii,USA

Nanjing,
China

New York,
USA

Chongqing,
China

Mid-USA
Abu Dhabi,
UAE
Muscat,Oman

4 Solar Impulse 2’s mobile hangar can be used to house the plane
during unscheduled landings.
© Solar Impulse | Stefatou| Rezo.ch

3 Flight plan of Solar Impulse 2’s intended around-the-world
journey

Varanasi,
India
Ahmedabad,India

era to high-quality 1080p. This projectrequired the integration and interfacingof a number of components as well as
cooling the media system adequately.

Mandalay,
Myanmarcated deep under the sea, Solar Impulse
is literally a flying ambassador for technological innovation and its potential to
improve the world.”

A true partnership
The cooperation and exchange of expertise and experience between ABB’s engineers and the Solar Impulse team hasenabled a unique opportunity to showcase renewable energy.
“The flight will test technology and human ingenuity to the limit, and that’s another important reason why ABB is partof this adventure – because we are constantly pushing the boundaries of technology and ingenuity to serve our customers while minimizing environmental
impact,” says Ulrich Spiesshofer, ABB’s
CEO. “While our groundbreaking innovations and technologies tend to be hidden
behind walls, buried underground, or lo-

Erika Velazquez
Solar Industry Segment Initiative
Zurich, Switzerlanderika.velazquez@ch.abb.com

A soaring vision­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­1 9

Balancing act
Microgrid optimization
control stabilizes
production in solar andhybrid microgrids­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 0

ABB review 2|15

CELINE MAHIEUX, ALEXANDRE OUDALOV – Traditionally, remote, off-gridmicrogrids have relied on diesel generators to produce electricity.
Diesel oil is usually delivered by conventional land or sea transport,
which results in transportation costs and a higher cost of electricity forend consumers. But with the environmental benefits and increasing
cost-competitiveness of renewable energy, it is now more and morecommon to find solar photovoltaic and wind power integrated withdiesel generators to form a hybrid microgrid. Energy storage devices
such as flywheels and lithium-ion battery systems may also be included.
Accommodating fluctuations in photovoltaic production and coordinating the operation of the diesel generators, feeder loads, energy storage
and grid stabilization devices in response to these fluctuations is a tricky
task that requires an advanced control system.

1 What is a microgrid?

I

t is becoming increasingly common
for traditional off-grid microgrid generators – usually powered by diesel
oil – to be supplemented by one ormore solar power plants and a numberof wind turbines ➔ 1– 2. The microgrid
might also include energy storage devices like flywheels and lithium-ion battery systems. Flywheels can provide instantaneous power to the microgrid tocounteract variations in output causedby passing clouds or sudden changes inwind speed. Battery systems store energy in larger amounts and over longer
periods to handle energy time shifts.
They can store solar energy produced
during the day when demand is low andrelease it in the evening when demandis high.
The challenge of integrating solar photovoltaics (PV) with diesel generators has
two aspects: handling fluctuations in thephotovoltaic production level, and coordinating the operation of the diesel gen-Title picture
Microgrids may comprise a mixture of diesel
generators, solar power, wind turbines, battery or
flywheel storage units and the electrical devices toconnect them all together. How can such a
disparate collection of equipment be effectively
controlled and coordinated? Shown are the PV
panels, and diesel and flywheel containers at
Marble Bar, Western Australia.

A microgrid is a smaller version of a larger(macro) power grid. It is a collection of power
generation sources, loads and energy storage
devices that operate as a single unit and are
kept in balance by a control system. Some
types of microgrids are connected to thesurrounding power (macro) grid; in addition to
generating their own power, microgrids canalso receive power from, or transfer power to,
the main grid. Other types of microgrids are
self-sufficient – they are “off grid” or “islanded”
and have to generate their own power.

Microgrids are suitable for a wide variety ofdifferent applications. They are the obvious
solution for islands like the Azores or Canaries
and for communities in remote locations like theAustralian outback, as well as for researchstations in far-off places like the Antarctic.
Military bases, university campuses, mines,
onshore oil and gas fields, theme parks andtourist resorts are other typical applications, as
are rural electrification programs in countries
lacking power.

erators, feeder loads, energy storage
and grid stabilization devices in responseto these fluctuations. This requires anadvanced control system that can connect and disconnect generators andloads, provide set points to generatorsand charge or discharge the flywheel orbattery system. By doing this, the control
system will maintain maximum PV penetration, reduce operating costs and keep
the microgrid stable.

highest level of power quality, grid stability and reliability of power supply.

ABB microgrid solution
ABB’s Microgrid Plus System™ is a distributed control platform that automatesand manages microgrids that consist offossil-fueled generators and renewable energy generation from one ormore sources. It
also integrates othermicro- grid components such as energy storage andgridstabilization
systems, and distribution feeders. Further, it connects
and communicateswith the adjoining
power grid, if there
is one ➔ 3 – 4.

ABB’s MGC600 controllers are the building blocks of the Microgrid Plus System.
They enable communication between all
the electrical devices in the microgrid
and use the data communicated by thedevices to make local decisions thatwork cohesively for the benefit of thewhole microgrid. The range of MGC600
controllers is comprehensive in scope
and uses a common hardware platformthat runs different types of firmware according to the electrical device concerned ➔ 5.

It is becoming increasingly
common for traditional offgrid microgrid generators tobe supplemented by solar
power plants, wind turbinesand energy storage devices
like flywheels and lithium-ion
battery systems.

The Microgrid Plus System is designed
to work with ABB’s other microgrid product – the PowerStore™ flywheel-basedor battery-based grid stabilization andenergy storage system. Together, these
two technologies calculate the mosteconomical microgrid configuration that
achieves a proper balance of supply anddemand – one that maximizes renewablepenetration (up to 100 percent), reduces
the operating cost and maintains the

These firmware packages contain thecore control logic of the MGC600. They
work in harmony with one another within
the Microgrid Plus System. For instance,
the PV control and monitoring system(MGC600-P) schedules and controls thePV plant in conjunction with the controllers that control the diesel generators(MGC600-G) and energy storage system(MGC600-E).

Balancing act­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 1

2 A typical microgrid

Solar PV power
Loads

Wind power

Diesel generation

Comprehensive functionality
The MGC600 has a number of uniquefeatures and benefits that improve theavailability of the microgrid and reduce
its consumption of fossil fuel by maximizing the penetration of renewable energy
generation:– Automatic starting and stopping of
the PV generator– Active power limitation based on thegenerator’s optimal load
– Active power limitation based on
system step load
– PV generator control for islanded
mode or grid connection– Active power limitation sharing
between multiple PV generators
The MGC600-P monitors and controls
the PV generator either with a PV plant
controller or with an inverter. It provides
manufacturer-independent control andmonitoring to allow different makes of inverters and plant controllers to be integrated into the microgrid system. For
low- and medium-penetration systems(ie, those without storage and stabilization devices), the MGC600-P monitors
the power output of the fossil fuel generators via an MGC600-G controller.
Based on the load levels of the fossil fuelgenerators, the MGC600-P determines
whether the power limitation set pointof the PV plant should be increased or­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 2

ABB review 2|15

decreased. This enables the fossil fuelgenerators to run at their optimal load,
while ensuring that the maximum amountof renewable energy is utilized.
Control strategy examples
The Microgrid Plus System has a long andsuccessful record of operating in various
types of microgrids. The following twotheoretical case studies illustrate how different levels of solar PV penetration requiredifferent control strategies. These, in turn,necessitate a control system that has theflexibility and functionality to accommodate different control strategies andto integrate varying
levels of renewableenergy.

nature, the diesel generator must run inparallel to the PV plant to provide systemfrequency and voltage references. In thisparticular case the increased generationof solar PV could drive diesel generator
output to a very low level. Diesel generator suppliers usually advise that the generator should not operate below 20 to30 percent of its nominal capacity formore than a few hours, as doing so
may damage the engine. Load sharing
coordination between the solar PV system and diesel generator is, therefore,
necessary.

An advanced control systemthat can connect and disconnect generators and loads,
provide set points to generators and charge or discharge
the flywheel or battery system
is needed.

In the first casestudy, the micro­
grid owner wants
to reduce exposure to diesel pricevolatility and thehigh cost of running the microgrid
on fossil fuel. A PV
power plant has been integrated into themicrogrid; it has the capacity to cover­a lmost 100 percent of instantaneous grid
demand at maximum production. However, because solar PV is intermittent in

In a Microgrid Plus solution, both the PV
system and the diesel generator are
equipped with MGC600 controllers: theMGC600-P for the PV system and the
MGC600-G for the generator. These two3 The Microgrid Plus System with MGC controllers operations and PowerStore example

Residential
Wind turbines
MGC600-W

PV plant
MGC600-P

M+ operations – local
and remote

Distribution feeder
MGC600-F

Communication network

Industrial andcommercial

Diesel generator
MGC600-G
Grid stabilizing
system
MGC600-E

Distribution feeder
MGC600-F

Grid connection
MGC600-N

sets of controllers exchange information
with each other in real time. Based on
the load levels of the fossil fuel generators, the MGC600-P automatically adjusts the set point and enables the generators to run at their optimal load, while
ensuring the maximum amount of renewable energy is utilized by the microgrid.
If the microgrid connects to a larger power grid, the grid operator may not accept
reverse power flow, ie, not allow powerfrom the microgrid to be transferred into
the transmission or distribution network.
In this case the microgrid will most probably run with the diesel generator
switched off. The MGC600-P controllerthat controls the solar PV plant will coordinate a power infeed from the main power grid with an MGC600-N controller at
the point of common coupling.
In the second case study, the production
capacity of solar PV in the microgrid issubstantial and exceeds demand during
the peak production hours. However, solar PV peak production and local load
peaks do not always occur at the sametime. The evening peak, when demand isusually the highest, does not coincidewith PV production, which occurs during
daylight. The solution to this quandary is
to store some of the PV energy produced
during the day for use during the evening

when the PV plant has stopped production. This can be done with a lithium-ion
battery system. The cost of these has
fallen significantly in recent years andmany different studies and manufacturers’ data forecast further cost reductionsin the near future.
The addition of an energy storage system
to the microgrid means that the microgrid
control system now has an additional
component to manage. This is not a difficulty for the distributed control concept of
the Microgrid Plus System: It is easy toinstall a dedicated MGC600-E controller
for the energy storage system that exchanges information with the other controllers in the Microgrid Plus System. The
MGC600-E controller continuously informs the other controllers about its status and the battery state of charge andstate of health, while receiving critical operational information from the diesel generator, solar PV and network controllers.

ABB’s Microgrid
Plus System is a
distributed control
platform that automates and manages microgridsthat consist of fossil-fueled generators and renewableenergy generationfrom one or more
sources.

Stable operation with PowerStore
ABB’s PowerStore is a compact and versatile flywheel-based stabilizing generator that reduces instabilities in microgrids
or weak grids due to fluctuations in solar
PV power output caused by passing
clouds. It is able to operate in a grid support mode for large networks or in virtual
generator mode for isolated microgrids.

Balancing act­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 3

The Microgrid Plus
System also integrates energy storage and grid stabilization systems,
and distribution
feeders. Further,it can connect
and communicate
with the adjoining
power grid.

4 ABB’s microgrid expertise
ABB offers turnkey solutions for, and has
references for, all types of microgrid requirements: Greenfield hybrid power plants
consisting of renewable and diesel power
generation; the integration of renewable energy
generation with an existing fuel-based
microgrid; optimizing the performance of an
unstable microgrid that combines renewableenergy and fossil fuel generation; stabilizing the

Firmware/controller

Description

Diesel generator (MGC600-G)

Controls, monitors and interfaces with diesel generators

Distribution feeder (MGC600-F)

Controls, monitors and interfaces with feeders and their protection relays

Photovoltaic solar (MGC600-P)

Controls, monitors and interfaces with solar array inverters

Single/multiple load (MGC600-L)

Controls, monitors and interfaces with large loads like crushers, boilers, etc.

Energy storage system (MGC600-E)

Controls, monitors and interfaces with battery-based ABB PowerStore

Network connection of microgrid(MGC600-N)

Controls, monitors and interfaces with other microgrids or larger grids

Wind turbine (MGC600-W)

Controls, monitors and interfaces with wind turbines

ensured by a quick power injection andthe efficient absorption capability ofPowerStore. The power fluctuations arecaused by variations in solar PV generator output due to passing clouds. Twodiesel generators (“Gen 2” and “Gen 4”)
are involved in power balancing but the
speed of the solar PV output variation
causes stress to their prime movers,
which results in faster wearing and more
maintenance. PowerStore intervenes
precisely during these short variations
and helps the diesel generators ramp up
and down in a sparing mode.
In addition, ➔ 6 illustrates how MGC600
controllers coordinate their actions. For
instance, Gen 2 is switched on and off by
the MGC600-G controller in accordancewith PowerStore’s state of charge andpower output, which is reported by the
MGC600-P. In other words, when repetitive solar PV fluctuations are detected
and PowerStore’s state of charge is getting low after assisting Gen 4 (green
curve), Gen 2 is switched on. Then bothgenerators share the power balancing
control while PowerStore is recharging.

ABB review 2|15

ABB has 25 years of experience developing
microgrid technologies and has delivered morethan 80 microgrid solutions worldwide – morethan any other supplier.

5 The MGC600 controller range uses a common hardware platform that runs different typesof firmware according to the electrical device concerned.

➔ 6 shows how stable power output is­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 4

connection of an existing renewable energy
plant to a weak power grid; and power gridstabilization.

Advanced control functions
Several advanced control functions areincluded in ABB’s microgrid optimization
products.
Cloud tracking

In order to guarantee the stable and economic operation of a microgrid with ahigh penetration of solar PV, ABB has
developed algorithms that track the
movement of clouds in the vicinity of the
microgrid. The algorithms predict thetime of arrival and duration of cloud cover
over the PV plant, and calculate the expected fall and subsequent rise in output(ramp rates). Very large ramp rates of solar PV can cause instability if they exceed
the ramp rate capability of the diesel
generator. Accurate short-term prediction of solar PV ramp rates will allow a
proactive control action and reduce theeffects of disturbance. If there is notenough energy stored in the battery system to cover the shortfall in PV production, a single generator or several generators can be scheduled in advance forstart-up. If production shortfalls are long,then an optimal amount of energy could
even be purchased from the market (forgrid-tied microgrids) during low-cost tariff hours, stored in the battery system

6 Power generation profiles in an isolated microgrid

300

200

100

0

26-Oct-11 10:16

26-Oct-11 13:03

Gen 2 power

Gen 4 power

26-Oct-11 15:50

PowerStore
power

26-Oct-11 18:36

PV powerPower
outputPowerStore is acompact andversatile stabilizing
generator that
reduces instabilities in microgrids
or weak grids due
to fluctuations insolar PV power
output caused bypassing clouds.

7 ABB’s low-cost and low-complexity control concept to save fuel in
PV/diesel microgrids
MGC600-G
RS485

Generator 1

MV busGenerator 2Generator 3

Ethernet

Generator 4

Generator 5

Solar PV string

TRIO 27.6 kW

Solar PV string

TRIO 27.6 kW

RS485

MGC600-P

MGC600 controllers are the building blocks of theMicrogrid Plus
System.
and then released during the day to meet
contracted quotas.
Hybrid energy storage

A hybrid energy storage system made up
of various energy storage technologies
with different characteristics (cycle life,

response speed, efficiency, cost and soon) can potentially help integrate largerscale solar PV at a lower total cost thanif the technologies were deployed separately. ABB is analyzing the advantages
and disadvantages of such a system andis developing control solutions for it.
Diesel fuel-saving solution

ABB is developing a low-cost and lowcomplexity control solution to save fuelin PV/diesel microgrids with a capacity
ranging from a few hundred kilowatts
up to a couple of megawatts. One
MGC600-G controller will coordinate
several small-scale diesel generators
and a single MGC600-P controller will
manage several small-scale solar PV­i nverters ➔ 7.

Alexandre Oudalov
ABB Corporate Research
Baden-Dättwil, Switzerland
alexandre.oudalov@ch.abb.com
Celine Mahieux
ABB Power Generation
Zurich, Switzerland
celine.mahieux@ch.abb.com

Balancing act­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 5­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 6

ABB review 2|15

A bright
futureEnergy storage transforms thesolar paradigm

PAOLO CASINI, DARIO CICIO – The amount of solar radiation that reaches the

Earth’s surface is more than enough to supply the world’s total energy needs.
However, matching the intermittent availability of this energy source with demand
can present a challenge, especially in the early morning and evening hours whensolar energy sources do not produce enough power to meet demand. This
challenge can be overcome by energy storage: Coupling solar energy sources
with energy storage can eliminate the unpredictable nature of solar power,transforming it into a highly controllable and easily dispatchable source of power.
From distributed storage systems to large centralized solutions, ABB has thedomain know-how and energy storage solutions needed to enable precise control
and connection of solar power installations.

Title picture
The energy the Earth receives from the sun is morethan enough to meet the world’s power needs. But
how can this energy be stored so power needs canbe met when the sun is not shining?

A bright future­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 7

1 Frequency regulation mode
Absorb power

Supply power

50.02
f (Hz)

50.00
49.98

Energy stored in ESS

Placing energy
storage adjacentto the solar PV
systems enablesprecise control
over when andhow much power
will dispatched on
to the network.

ChargeDischarge

Time (s)proves power quality for the end users.
Further, an ESS allows for more efficientuse of the power generated from the distributed solar plants.

S

trategically placed, local solar
power generators not only reduce greenhouse gas emissions, but they also enhance
grid reliability and security: Placing
smaller, distributed generation sources
close to the load makes the grid more
resilient against outages and power
quality disruptions, which benefits both
local utilities and end users. There are
economic benefits to be had too if theconsumer can generate and consume
his own power
and thus avoid
utility charges.

PV energy storage helps save even moreby making the solar PV plant a reliable
source of power when the customer’s­usage is at its highest. At these times,
energy that was stored by the ESS during
low demand periods can be used, thus
avoiding hefty peak demand charges.
ABB’s community storage solutions aredesigned for all these cases and can beused in applications ranging from 25 kW
to multi-megawatts. For example, ABB’s
integrated energy storage module (ESM)

Coupling energy storage withutility-scale solar PV allows
the unpredictable and variable
solar plant to become an easily controllable resource thatcan be dispatched to provide
second-by-second frequency
regulation in real time.

However, in order to fully realize the potential
and value of­solar power, its
intermittent nature must somehow be overcome. One major
tool for doing
this is the energy storage system (ESS). Placing energy storage adjacent to the solar photovoltaic (PV) systems
enables precise control over when andhow much power will be dispatched on
to the network. Energy storage can alsoenable smooth power output, which im-­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 8

ABB review 2|15

comprises a transformer, low- and medium-voltage switchgear, and automationequipment such as inverters. This uniquedesign provides a quick, simple installation with a high level of safety for theequipment and operators. The choice of2 Capacity firming mode

3 Load-shifting mode
Absorb power

Renewable generated power (absorbed)

Supply power

Load
ChargeDischarge

Energy stored in ESS

Energy stored in ESS

PowerSupply power

ChargeTime (s > min)which lithium-ion battery technology touse in a particular ESM is based on theapplication’s specific requirements.
Utility-scale solar energy
The increasing demand for power sources that emit less carbon and are moresustainable is driving utility-scale solar
power generation growth at an unprecedented rate. However, the electrical grid
was designed to deliver a planned andstable supply of power from centrally­located power sources, via the transmission and distribution lines, to end users.
Engineers carefully plan and constantly
recalibrate the grid to ensure that poweris available where it is needed at the precise moment it is needed. Adding energy
sources that are variable, intermittent
and distributed throughout the transmission and distribution network requires
significant additional control and precision to make sure demand and supply
are aligned.
ESS for frequency regulation
System operators often use large-scale
generation facilities to not only provide
bulk power to the end users, but also toprovide the ancillary services needed tomaintain the integrity of the electricalgrid. One of the more pertinent of these
services is real-time frequency regulation. Around the world, the electrical gridneeds to operate at either 50 or 60 Hz inorder to ensure the facilities and criticalequipment used in manufacturing areproperly powered. This requires instantand continuous balancing of electricity
supply with demand. This is difficult

Discharge

Time (h)enough to do with traditional, predictableand easily dispatchable generators, but
the task becomes extremely complex
i ndeed when solar sources, with their­­inherent variability, are added to the mix.
Further, as more utility-scale solar plants
are brought online and more coal-based
plants shut down, the easily controllable
resources that provide such grid services
become fewer. However, coupling energy storage with utility-scale PV allows
the unpredictable and variable solar
plant to also become a more easily controllable resource that can be dispatched
to provide second-by-second frequency
regulation in real time. When used in
combination with solar, the ESS ischarged or discharged in response to anincrease or decrease of grid frequency ➔ 1. This approach to frequency regulation is a particularly attractive option
due to its rapid response time and emission-free operation.

By quickly absorbing or injecting
power in response
to grid control signals, the ESS canensure that thecorrect frequency
and voltage levels
are maintained.

ESS for capacity firming and ramping
supportIn order to maintain the integrity of theelectrical grid and ensure power quality,
voltage and frequency must constantly
be kept at specified levels. However, withutility-scale PV plants, the ability to maintain these levels can be quickly compromised by the passing of clouds, an abruptchange in the weather or a crack in a solar PV panel. These variations can cause
rapid fluctuation of the PV power output– resulting in deviations in frequency andvoltage. Even a second of cloud coverage can cause the voltage to drop, de-A bright future­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­2 9

4 ABB’s EssPro PCS container and cabinet enclosure configurations

stabilizing the local network. The sudden
drop in voltage and power can also cause

where energy storage can help the system operator maintain grid integrity throughload-shifting capabilities. By coupling solar powerwith energy storage, the ESS cancharge when generation is higher
than demand anddischarge
when
demand begins tospike, yet the sun
is setting ➔ 3.

By coupling solar power withenergy storage, the ESS cancharge when generation ishigher than demand and discharge when demand begins
to spike, yet the sun is setting.
deviations in frequency levels, disrupting
the overall operating characteristics ofthe grid. By quickly absorbing or injecting
power in response to grid control signals,
the ESS can ensure that the correct frequency and voltage levels are maintained ➔ 2. Not only can energy storage
provide this capacity firming for the PV
system, but it can also make sure that
the PV power output increases and decreases at a rate specified by the grid
operators to ensure that the PV plant­abides by local grid codes.
ESS helps network reliability throughload shifting
In areas with a high penetration of solar
generation, the local utility network issusceptible to resource adequacy issues
when demand and PV generation are outof balance – specifically, in the earlymorning and evening hours when demand begins to increase but solar sources are not producing enough power toaccommodate this demand. This is­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 0

ABB review 2|15

ESS for utility-scale solar performance improvement
Strategically placed ESSs can increase
operational performance and grid reliability, and better integrate utility-scale solar
generation. From power conversion systems (PCSs) to fully integrated and turnkey battery ESSs, ABB’s EssPro™ energy
storage solutions help to ensure the highperformance of solar plants and to maintain grid reliability and efficiency ➔ 4.
ABB’s EssPro PCS links the ESS’s battery to the electrical grid and converts
the stored energy from DC to AC that iscompatible with the utility network. In
addition to the conversion technology,
the system also provides the controls
needed to help maximize the PV plant’s
operational performance.
ABB’s EssPro Grid integrated, turnkey
ESSs are available for power requirements ranging from hundreds of kilowatts to tens of megawatts and are5 Example of a 1 MW, 15-minute layout of ABB’s EssPro Grid

6 Residential PV demand and supply match
poorly.
Solar power generation profile

Battery container

Household’s energy consumption

Power converter

Transformer

Medium-voltage
equipment

Control room

Sunriseready for connection to medium- or highvoltage grids ➔ 5. Based on ABB’s broad
experience in electrical utility grids andin-depth knowledge of battery technologies, the EssPro Grid combines advanced controls and algorithms with thestorage technology best suited for theapplication to maximize the performanceof the ESS.
Residential-scale solar energy
storage
The record growth experienced by thesolar market worldwide since 2004 wasinitiated by the introduction of the feed-in
tariff (FIT) scheme in Germany. For years,
the FIT ensured remuneration for every
solar kWh injected into the grid at a tariff
substantially higher than the retail electricity price – without the necessity of amatch between what was injected andthe actual demand of the household,­e ither in terms of energy balance or interms of power equivalence at any given

Sunsetbating associated grid instability issues;
the approaching parity of self-generation
costs and retail energy costs; and thediminution of incentives.
The new solar energy keywords are selfconsumption (the consumption by thehousehold of locally produced solar energy) and self-sufficiency (the capability
to autonomously meet the energy demand of the household). To achievethese two aims, the misalignment between the daily solar power profile andthe household demand must be overcome ➔ 6. This is achieved by the addition of an energy storage capability to
the traditional PV system.
REACT
Practicality and cost make electrochemical batteries the best way to store excess solar energy. But the unplanned addition of batteries to a PV plant – even if
it could bring self-sufficiency – would
most likely result ina very doubtful financial return. An
economically sustainable residential
PV/storage solution is, instead, theresult of a compromise between thesize of the installedbattery bank andthe levels of selfconsumption andself-sufficiency the household canachieve with the addition of a tailored energy management strategy.

The misalignment between
the daily solar power profileand the household demand isovercome by the addition ofan energy storage capability
to the traditional PV system.
time. But this landscape is now changing, driven by the increased penetrationof distributed generation further exacer-

A bright future­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 1

7 ABB’s REACT has battery storage in the left compartment andelectronics in the right.

8 A typical REACT layout: A dedicated energy meter delivers
real-time feedback on self-consumption and self-sufficiency.

MPPT1

DC/AC

MPPT2

Energymanager

REACT
energymeter

Battery
chargerAC
gridHousehold
loads

REACT

ABB’s residential energy storage system
REACT (renewable energy accumulator
and conversion technology) ➔ 7 is designed to realize this trade-off in the best
possible way. A REACT system comprises a grid-tied PV inverter (up to 5 kW) fed
from a DC link – to which the maximum
power point tracking (MPPT) trackers(connected to the PV array) and a bidirectional battery charger are connected ➔ 8. Though its integrated DC-link architecture is the best cost solution for
new installations, it can also be used toretrofit existing PV plants as an AC-linkbattery charger by simply not connecting
the PV array to its input.

terms of dispatchability, stability, controllability, etc. The continued developmentof storage technology is essential to
speed the journey toward self-consumption, self-sufficiency and the flawless integration of solar sources into electrical
power grids worldwide.

The new solar
energy keywords
are self-consumption and selfsufficiency.

The energy storage section of a REACT
system is made of lithium-ion batteries
with a modular architecture that allows
the system to expand from its native
2 kWh up to 6 kWh (field upgradable). An
onboard load management system allows
interaction with selected loads/appliances, thus boosting the energy independence of the household by up to 60 percent in the basic system configuration.
The choice of lithium-ion batteries is driven by their favorable expected cost profile in coming years, size/capacity performance, charge/discharge power rating,efficiency and longevity (more than twicethat of other current technologies).

Paolo Casini
ABB Discrete Automation and Motion,
Power Conversion
Terranuova Bracciolini, Italy

The future is bright
The addition of an energy storage capability to a PV installation, no matter whatsize, helps overcome the intermittent nature of solar power and brings it into linewith more traditional energy sources in­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 2

ABB review 2|15

paolo.casini@it.abb.com
Dario Cicio
ABB Battery Energy Storage Systems
Baden, Switzerland
dario.cicio@ch.abb.com

Evolving solutions
Technology trends and design targets for next-generation
photovoltaic inverters
JUHA HUUSARI, PAOLO CASINI – Photovoltaic power conversion
is a relatively new application area in the world of powerelectronics. Early photovoltaic conversion technologies werebased on motor drives and only recently has the industry
seen solutions developed solely for photovoltaic conversion.
To maintain a strong presence in today’s photovoltaic
busi­ness, companies must be able to adapt to a constantly

evolving market and also be visionary, focusing on key
technologies to ensure cutting-edge designs for tomorrow’s
needs. ABB, with its strong background in power electronics,
is not only a leading supplier of photovoltaic products, butalso a forerunner in next-generation photovoltaic conversion
technology.

Evolving solutions­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 3

1 Characteristic behavior of a photovoltaic power source

1.2
Current
Power

PV current (p.u.) and power (p.u.)

1.0

0.8

0.6

0.4

0.2

0
0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

PV voltage (p.u.)W

idely adopted feed-in tariffs and other incentives
that helped lower the costof photovoltaic (PV) modules led to a boom in the PV industry­between 2006 and 2011, particularly inEurope [1]. However, the sharp reductionof financial incentives has forced themarket to adapt – meaning cost has
become a key target for new product­launches. Research, too, has had to
adapt. ABB has been vigorously investigating new developments for PV applications, particularly in PV power conversion systems.
PV power conversion
PV power conversion essentially means
efficient and controlled delivery of theelectrical energy from the PV modules
into the load of the system (in smallscale residential applications, such asheating or lighting) or into the transmission grid (in larger-scale applications).
The sun’s radiated energy reaching theface of the Earth is captured by thesemiconductor junction within a PV cellthat generates charge carriers, ie, elec-

Title picture
A 181-kWp PV installation on the roof of ABB
factory in Helsinki, Finland.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 4

ABB review 2|15

trical current, into the system. By its­n ature the PV cell is intuitively seen as
a current source, unlike most electric
power sources, which have voltagesource characteristics. This, in turn, requires appropriate measures to reliably
control the power generation. Early converters intended for PV applications
i nherently provided suboptimal per­­formance and even the scientific community struggled to accept the paradigm change with PV conversion control
principles [2]. Such performance flaws
have since been eliminated.
Due to its nonlinear semiconductor nature, the PV generator yields its maximum
output power only
when the generator
is forced to operate
at a specific voltage level ➔ 1. Furthermore, environmental conditions,such as the temperature of the PV
cells within thegenerator as wellas the intensity of
the arriving irradiation drastically change
the electrical properties and the generated power of the PV generator. The
generated power increases as a functionof decreasing cell temperature and increasing irradiation intensity. Therefore,
in regions like northern Europe a PV generator may produce peak power duringcold, early spring mornings.

The intermittent behavior of the PV generator is supervised by the power electronic
converter processing the generated powerof the PV generator. Through a feature
known as maximum power point tracking(MPPT), the converter monitors the output
power of the generator, adjusting it constantly to the desired level by changing thevoltage level of the generator.
The basic building block of a PV generator is the PV cell, roughly 15 cm × 15 cm,
with a thickness on the order of 100 µm.
A single PV cell typically generates acouple of watts at voltages below a single volt, depending on the size and technology used. Most of the cells are silicon

By its nature the PV cell is
intuitively seen as a current
source, un­like most electric
power sources, which havevoltage-source characteristics.
(Si) based, but the entire family comprises other conventional semiconductormaterials, such as gallium-nitride (GaN),
indium-phosphide (InP) and copper-indium-gallium-diselenide (CIGS), as well as
more exotic – namely, organic and dyesensitized – materials.

2 Conceptual photovoltaic power processing converters

DC
DC

DC

DC
AC

DC
AC

DC
AC

AC

N
L1
L2
L3
Module-integrated
inverterSingle-phase string
inverter

Individual cells are joined in a series­a rrangement to create a PV module (alsoreferred to as PV panel), comprising two
to 96 PV cells. This is done because
power processing is more feasible withhigher voltage levels. PV modules typically range from 5 to 350 W; the largescale systems are realized with larger,
high-power modules. The PV modules
are connected in series to form the fundamental unit, a PV string. Due to safety
regulations, the maximum voltage of
the PV string versus Earth is limited(1,000 V/1,500 V in the European Union;
600 V in the United States), which in turndefines the string’s maximum power.
One PV string rated for 1,000 V usuallyprovides a nominal DC power of 5 kW.
Thus, commercial PV inverters for multiple strings are typically rated for multiples of 5 kW.
The power converters processing thegenerated power are typically categorized as follows: micro-inverters, generally interfacing one to four PV modules
into the AC grid; string inverters, 1- to
3-phase inverters interfacing one to
20 PV strings; and, finally, 3-phasec entral inverters usually rated above­
100 kVA ➔ 2. In addition, there is a nichegroup of power optimizers that are
a dd-on, low-power DC-DC converters­
intended to fine-tune the generated
power in existing PV strings. Excluding
power optimizers, ABB provides converters and solutions for all of these­a pplication areas.

Three-phase string
inverter

Plant-level features
Traditionally, PV installations were realized with the highest possible inverter
rating relative to installation size: Small
installations with micro-inverters and,
respectively, larger systems with high­power inverter stations. This concept ischanging as the industry experiences atrend of high-power systems being builtwith string inverters. The factors driving
this include higher power output as distributed inverters perform fine-granularmaximum-power extraction as well as
lower installation costs. In addition, during inverter failures only a restricted partof the installation stops producing power. As a result, the importance of string
inverters is increasing.
Another interesting development emerging in PV applications for larger systems
is the inclusion of environmental measurement data to enhance near-future
prediction and power output. Throughmonitoring, eg, the cloud movement
near the PV power plant, the centralized
controller can, in advance, guide theinverter(s) within the plant to adjust theiroperation, ie, to improve the MPPT operation. Additionally, this information canbe used to predict the available shortterm power, benefitting the grid operator.

Three-phase central
inverterPower
optimizers

Through monitoring, eg, the cloudmove­m ent near the
PV power plant,
the cen­t ralized
controller can, in
advance, guide theinverter(s) within
the plant to adjust
their operation, ie,
to improve the
MPPT operation.

A modern-day feature that has emergedin PV applications is the connection tovarious distributed data services, in which
the inverter contains a connection to theinformation network to store and share

Evolving solutions­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 5

3 Evolution of power density in wall-mountable, transformerless PV inverters
Three-phase string inverters
1100

900
Inverter power per weight (VA/kg)

The heart of a
PV inverter is thebridge of fastswitching semiconductor devices
that, together with
passive energystor­a ge elements,
enable power­processing.

700

500

300

100
2002

2004

2006

2008

2010

2012

2014

2016

Launch year

relevant information, such as historicalenergy output. Again, such information
aids the grid operator in dealing with demand-power balancing.
Emerging semiconductor devices
The heart of a PV inverter is the bridgeof fast-switching semiconductor devices that, together with passive energystorage elements, enable power processing. While the clear majority of PV
inverters utilize Si devices, lately the industry has seen the emergence of silicon carbide (SiC) devices. Able to withstand higher voltages and temperatures
and to switch faster than Si counterparts, the SiC device enables morecompact and more efficient power processing converters [3]. However, SiC
technology is expensive and the longterm reliability of SiC components remains an open question. These drawbacks notwithstanding, SiC devices canbe seen as an integral part of PV inverters in the coming years, as demonstrated through ABB’s research [4] as well as
products utilizing SiC technology.
The benefits of GaN technology compared with SiC are still being debatedwithin the industry. It is claimed that GaN
devices enable ultrafast switching action,
thereby providing greater benefits in efficiency and power density. However,practical demonstrators validating theseclaims are yet to be announced.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 6

ABB review 2|15

While SiC devices are already technologically mature, GaN devices are not. At
present, there are only a handful of GaN
products on the market and, furthermore, no high-current power modules
are available. This is also due to theproperty of the lateral GaN semiconductor junction, which makes parallelingmany GaN chips difficult, thus hindering
the production of high-current modules.
With single-packaged GaN chips it ispossible to reach power levels of roughly
20 to 30 kW; at higher power levels modules are required.
Power density in string inverters
Over the past 10 years, the design targets for PV string inverters have beenchanging dramatically. The first-generation designs targeted high energy yieldwith multiple isolated MPPT converters.
The second-generation designs maximized conversion efficiency, followed bythird-generation single-stage systems.
Current design targets are now lower
cost and higher power density. Each ofthese posed different challenges to power electronics designers.
The power density concerns arise fromvarious needs: For safety reasons, the industry has adopted a weight limit of 75 kg
for each cabinet to be carried by two people. For wall mounting, there are also
limits regarding the weight capacity of­the mounting structure and the wall
itself. Another driver is the lower transportation cost per installed Watt.

The evolution of the power density ofcommercial wall-mountable, transformerless three-phase PV string inverters
weighing less than 75 kg shows thati nverter manufacturers are putting in­creasing effort into maximizing the power density ➔ 3.
The power density of PV string inverters
has definite limitations. Typically the passive filtering elements make up a significant part of the system weight, but theheat transfer solution, the enclosure itself
and various protection devices also add
considerable weight. Many of these restrictions cannot be changed – for example, the enclosure thickness and theuse of certain protective means are defined in standards (eg, in IEC 62109).
The higher the power level, the bulkier
the protection means becomes, thus resulting in a heavier enclosure to support

A modern-day
feature that has
emerged in PV
applications is theconnection to various cloud services.
the weight and to provide an adequate
ingress protection (IP) rating.
The challenge of reaching a higher power
density will push designers to look formore innovative system solutions andfoster the use of next-generation semiconductor components.
Utility-scale PV solutions
Although technological developments
have been seen throughout the entire PV
industry, the utility segment has had themost impressive pace of innovation.
Since the early stages of the modern PV
market the evolution of utility-scale PV
inverters has been driven by the optimization of the PV plant’s production efficiency and total cost of ownership (TCO),
that is, the summation of the initial capital expenditure (capex) and the operational expenditures (opex) sustained during the life of the plant.

Most of the efforts by the inverter industry in the past 10 years have been aimed
at improving the inverter’s power conversion performance, which has resulted inincreased efficiency values up to 98 percent weighted and 99 percent peak. But
the unavoidable asymptotical efficiency
trend and the modest incremental gain of
the financial return in relation to the added cost of better-performing topologies
and control techniques has gradually
brought attention to the reduction of the
TCO.

An additional benefit of smarter packaging and cooling technologies is increased
power density, which results in reduced
logistics and installation costs. This isparticularly important as utility demand
shifts to emerging markets, where installations are needed in remote areas.

Innovation at the inverter level is seen asa means to drive down the cost of thebalance of system (BOS), which represents 60 percent of the cost of a utility
PV plant, compared with less than 10
percent of the cost incidence of the inverter itself. A few years ago the progressive adoption of the 1,000 V system
voltage from the 600 V system voltage
allowed a 25 percent reduction of the DC
BOS. The PV industry is today on theverge of a similar change with the upcoming 1,500 V module technology,
which will revolutionize the utility inverter
offering by requiring a significant reviewof the electronic and electromechanicalcomponents and topologies deployed in
PV inverters.
The other component of the TCO is operation cost. The typical annual operationand maintenance cost of a PV plant isroughly equal to 1.5 percent of its initial
capex cost and a significant part of it isrepresented by the maintenance requiredby traditional air-cooled PV inverters, especially when installed in remote andhostile conditions. Throughout the 20
years of expected field life the opex becomes a major contributor to the cost of
the plant. Combining the need to reduce
maintenance costs with reduced logistic
costs and ease of installation creates another driver for the evolution of utilityscale inverters’ mechanical packaging.
The sudden switch to outdoor inverter
enclosures in several utility portfolios was
the initial move in this direction that willcontinue with the development of innovative, low-cost maintenance cooling solutions. The traditional air cooling of IP20
inverters, with their periodic maintenanceto clean air filters and decontaminate
electronics exposed to the direct air flow,
is gradually moving to sealed-enclosure
solutions IP54 or IP65 rated with liquid or
2-phase cooling solutions.

Juha Huusari
ABB Corporate Research
Baden-Dättwil, Switzerlandjuha.huusari@fi.abb.com
Paolo Casini
ABB Discrete Automation and Motion,
Power Conversion
Terranuova Bracciolini, Italy
paolo.casini@it.abb.com

References[1] “Global market outlook for photovoltaics
2014–2018,” European Photovoltaic Industry
Association.
[2] L. Nousiainen et al., “Photovoltaic generator as
an input source for power electronic converter,”IEEE Transactions on Power Electronics,
vol. 28, no. 6, pp. 3028–3038, June, 2013.
[3] C. Weizer et al., “Silicon carbide high powerdevices,” IEEE Transactions on Electron
Devices, vol. 43, no. 10, pp. 1732–1741,
Oct. 1996.
[4] C. Ho et al., “A comparative performance studyof an interleaved boost converter using
commercial Si and SiC diodes for PV applications,” IEEE Transactions on Power Electronics,
vol. 28, no. 1, pp. 289–299, May 2012.

Evolving solutions­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 7

Life-cycle automationand services
A holistic approach to
photovoltaic plant
automation, operationand maintenance­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 8

ABB review 2|15

ADRIAN TIMBUS, MARC ANTOINE, LUIS DOMINGUEZ – The photovoltaic

power industry is rapidly growing, with worldwide installations expected to grow by 60 to 66 GW in 2017 [1]. ABB is deeply involved in thisgrowth, applying a holistic approach to photovoltaic generation
projects that encompass the entire plant life cycle as well as the twostages of photovoltaic generation projects. The first stage is to design
the solution, select the equipment and build the plant. The second isto ensure that the plant produces the maximum amount of power, andthat its equipment is managed efficiently to minimize operation andmaintenance costs. This holistic approach is a culmination of ABB’s
expertise in providing technologies for solar power applications andthe company’s vast service and maintenance resources.

1 ABB’s photovoltaic power plant offeringA

BB’s technologies for photovoltaic (PV) power plants aredesigned to maximize plant
performance and provide
owners with a rapid return on investment
and long plant operating life. From electrical balance of plant (EBoP), to control
systems and power management, toproduction forecasting and remote monitoring and services, ABB’s PV power
generation technologies seek to ensure
maximum power production at minimal
cost ➔ 1.
World-leading plant automation
systemSymphony® Plus for Solar, ABB’s automation system for PV power plants, is aversatile and scalable monitoring andcontrol system. As its name suggests, it
is part of ABB’s Symphony Plus platform,
the total plant automation solution forthe power and water industries. Symphony Plus is the latest generation of theSymphony family of distributed control
systems which, with more than 6,500
operating installations, is one of the mostwidely used plant automation platforms
in the world.
Symphony Plus for Solar monitors andcollects data from the critical components of the plant. These include thepanel strings, transformation centers

As a leading provider of photovoltaic (PV)power plant technologies, ABB partners withand guides owners and investors. ABB
performs feasibility studies and analyzes the
project’s profitability; designs, engineers andoptimizes plants; provides project management; and supplies electrical and automation
systems. Through its comprehensive operationand maintenance (O&M) offering, which
includes an advanced remote monitoring andservice concept, ABB ensures that each plant
maximizes production while protecting its
assets.

ABB’s scalable power and automation solutions
for PV power plants are designed for rapid
deployment. They are pre-assembled,
factory-tested and containerized to enable
short lead times and easy installation. With the
exception of the solar panels, which ABB does
not manufacture, the solutions consist entirelyof ABB products, designed specifically for PV
applications. These are seamlessly integrated
to deliver the highest levels of reliability andefficiency and the lowest levels of plant energy
consumption. ABB has delivered more than
100 integrated electrical and automation
solutions for PV power plants, with a combined
generating capacity of around 1,000 MW.

(each of which contains inverters, transformers, medium-voltage switchgear
and low-voltage switchboards), the gridconnection and the meteorological stations. The system supports a broad
range of communication protocols, enabling it to connect and exchange datawith all of the components. Equipped

Power management
Power management functionality is key
to faciliting the grid connection of PV
plants. Symphony Plus’ high-performance controller connects to all relevant
actuators (inverters, tracking systems
and – if applicable – capacitor banks,
STATCOMs 1 or energy storage), and­performs real-time
calculations
toregulate the plant’s
power productionin accordance withthe specifications.
Accessing all relevant plant information, it dispatches
set points to theinverters. It also ensures that plant management and control is in accordancewith the local grid code requirements,
controls the production ramp rate, andprovides power factor and voltage control at the point of connection to the grid.

Symphony Plus for Solar
improves the return on investment with comprehensive
O&M services.
with a real-time database and historian,it acquires and stores all relevant plantdata, either on-site or at an ABB remote
service center.
Using the IEC 61850 communication
protocol, Symphony Plus for Solar monitors and controls substation equipment
and integrates generation and electricalcomponents into a single information
system.
One of the main differentiators of theSymphony Plus platform is that it is designed to last the operating life of theplant. Through ABB’s “evolution without
obsolescence” life-cycle policy, eachgeneration of the Symphony Plus family
builds on and enhances its predecessor,
adding new technologies and new functionalities to meet the evolving performance objectives of its users. An investment in Symphony Plus hardware andsoftware is thus protected throughout
the life cycle of the plant.

Production forecasting
As PV plants grow larger, the ability toforecast power production has become
an increasingly important factor in plant
profitability. ABB provides a flexible production forecasting solution that uses
data from the panels, strings and invert-

Title picture
Operation and maintenance services are one of the
key components of ABB’s photovoltaic offering,allowing plant operators to minimize operation andmaintenance costs.

Footnote
1 Static synchronous compensators

Life-cycle automation and services­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­3 9

ABB provides aflexible pro­duction
forecasting solution
to predict plant
output.

2 Architecture of Symphony Plus for Solar

Customer

Customer

CustomerField technician

Plant diagnostics

Powermanagement

Power and priceforecasting

Remote PV
services

Real-time monitoring
systemSet points for each plantServiceGate

Plant
automation

ServiceGate

Plant data, alarms, notifications

Plant
automation

ServiceGate

Plant
automation

3 Alarms and notifications in the remote portal

ers, as well as historical production andmeteorological information, to predictplant output. The forecasting horizon
spans from hours ahead (typically 6 hahead, with a time resolution of 15 min)to days ahead (typically one week, withhourly resolution).
ABB has also developed algorithms thattrack the movement of clouds in the vicinity of the PV plant. Using advanced
image processing and computer vision
techniques as well as optical and physical models, the algorithms predict thetime of arrival and duration of cloud cover over the plant, and calculate the expected drop in output power. If the plant
is equipped with an energy storage system, optimization of power balancing isachieved by using the accurate short-­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 0

ABB review 2|15

term prediction of power fluctuations
caused by cloud coverage.
Remote monitoring and control
Plant owners need to minimize operationand maintenance (O&M) costs by being
able to quickly identify underperforming
components. They require predictive
maintenance to reduce downtime, extend equipment life cycles and evaluate
the impact of equipment failure. They
also expect quick access to service engineers and product experts.
ABB’s remote monitoring, operations
and service platform for PV power plants
delivers on all these fronts. Symphony
Plus for Solar comprises three main
components: a remote-enabled interface
called Symphony Plus ServiceGate,Symphony Plus for
Solar comprises
three main components: a remoteenabled interface,a remote service
center and a dedicated Web portal.

4 Overview display using maps

5 KPI dashboard

ServiceGate provides a high-speed andsecure data transmission connection between the plant automation systems andan ABB remote service center. It supports
system configuration, health checks andsystem diagnostics, as well as remote­operations of plant equipment.

played in the dedicated Web portal.
­U nlike other monitoring systems on themarket, ABB’s system enables real-time
plant operations through an ergonomic
human-machine interface (HMI). Moreover, an optimized power management
function is also available at the fleet levelto control the production of the entire
fleet at the best economic running point.
The service center is manned 24 hours
a day by accredited engineers, ready toreact at all times to any field problems.

The data from ServiceGate is received
by, and stored at, ABB’s remote service
center, which is equipped with a dedicated hardware platform and configurable software. It runs the processing
and monitoring software and advanced
applications, and stores the results dis-

The Web portal has a dedicated interface
through which the PV plant communicates with the external world. All plants inthe fleet can be managed through thesame Web portal, which can be accessedby authorized users anytime, anywhere
using a PC or mobile device. The log-in

ABB’s remote service center, and a dedicated Web portal ➔ 2. The platform canbe used for a single plant or a fleet of PV
or other renewable energy plants.

provides different levels of authorization
based on roles defined in IEC 62351.
Key features of the Web portal include
alarms and notifications, dynamic presentation of collected data, predictive maintenance, production forecasting, production
and performance cockpits, a reporting andticketing system, and health checks.
Alarms and notifications

Besides receiving standard alarms fromthe plant such as faulty inverters andplant equipment, users can generate
their own alarms for situations like “lowKPI value.” When an alarm is activatedthe platform conducts a preliminary diagnosis of possible operating failures andimmediately notifies the responsible personnel by SMS or email ➔ 3.

Life-cycle automation and services­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 1

ABB is currently
using the remote
service platform
to monitor andcontrol more than
50 PV power
plants worldwide.

6 Plant performance report

Maps with dynamic data

Reporting and ticketing system

Maps show the geographical location of
the fleet plants with icons. An adjoining
frame contains a list of the plants in the
fleet and uses dynamic traffic lights andicons to show the status of contractual
KPIs, the presence of open maintenancetickets and the status of the plant’s connection to ServiceGate ➔ 4.

The remote service platform stores datafrom the PV plants, and the Web portal
uses the data to, for example, automatically generate: reports on production,interventions and actions by operators;
an O&M log book that collects tickets relating to O&M activities and tracks operators’ actions; and executive-level reports with information necessary to
manage the plants ➔ 6.

Predictive maintenance

The remote service platform contains a
set of tools to detect and correct themost common reasons for underperforming assets. The tools analyze theplant in small sections (typically individual strings) to pinpoint local problems at
an early stage before they develop intolarger production problems. They detectsoiling (dust accumulation on the modules); total and partial shading of strings;
and aging, which analyzes the efficiencyof the PV modules over time to determine the loss in performance caused bydegradation.

Health checks

The remote service platform also performs equipment health checks. These
consist of fingerprint diagnostics, whichmonitor and assess equipment performance and identify reliability issues. They
are available for plant assets, including
the automation system (hardware andsoftware), cyber security settings, andelectrical process equipment. The fingerprints are used to start a continuous optimization process by identifying necessary improvements and a schedule for
their implementation.

Production and performance cockpits

Other applications that monitor and analyze plant production include performance ratio monitoring, which is a realtime cockpit for monitoring plant
production and KPIs (based on QlikView
technology) ➔ 5; equipment condition
trending that monitors the performanceof critical plant equipment in real time;and fleet analysis, which provides a historical data dashboard for comparing
and analyzing fleet performance.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 2

ABB review 2|15

Adrian Timbus
Marc Antoine
ABB Power Systems, Power Generation
Baden, Switzerland

ABB is currently using the remote service
platform to monitor and control morethan 50 PV power plants worldwide.
These plants range in size from less than
1 MW to more than 100 MW, and include
single plants and entire fleets. High customer satisfaction and a large number ofrenewal contracts indicate that ABB’s
holistic approach to PV power production is producing real benefits and measurable value for customers.

adrian.timbus@ch.abb.com
marc.antoine@ch.abb.com
Luis Dominguez
ABB Corporate Research
Baden-Dättwil, Switzerlandluis.dominguez@ch.abb.com

Reference[1] Bloomberg New Energy FinancePutting it all together
Integrating distributed renewable energies into the grid
JOCHEN KREUSEL – More than ten years ago the new renew-

able sources of electric energy – sun and wind – began tomake their way into the electric power supply system. At thattime, they were seen as two additional primary energy
sources that could be connected to the existing systems
without making any fundamental changes. Today, these newrenewable energies have, in some countries, become thelargest generation subsector. In light of the significant cost
reductions of the past years further acceleration of thisgrowth is expected. But the approach of connecting renewable energies to the existing systems is too shortsighted.

Instead, electric power supply systems must be further
developed to integrate new sources on a larger scale.
With its high scalability, photovoltaics is the strongest driverof this change, affecting all areas of supply and utilization
along the electric energy value chain. ABB’s in-depth knowledge of renewable power generation technologies andcomprehensive experience with grid codes and utility
practices in use around the world enables it to provide thefull range of products, systems, solutions, services andconsultant capabilities to serve the renewable energy
industry.

Putting it all together­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 3

1 Wind and solar energy – top five countries in terms of installed and new capacity in 2013
40

GW

GW

100

50

0

20

0
China

USA

Germany Spain

India

1a Wind: installed capacity, 2013

Germany China

Italy

Japan

USA

1b PV: installed capacity, 2013

20

15

GW

GW

10
10

5

0

0
China Germany

UK

India

Canada1c Wind: new capacity, 2013

S

ince the end of the 20th century, an increasing number ofcountries have been promoting
the use of wind and solar energy. Denmark has been a pioneer in thisfield, and by 2011, was supplying morethan 40 percent of its electric energy demand with renewable sources – threequarters of which was wind energy. Germany is also being watched closely as
the first large industrial country attempting to transform its electricity supply witha strict focus on new renewable sources.

➔ 1 shows the five leading countries in

the world in terms of installed capacityand new wind and solar capacity in2013. Countries from all regions are active, and some of the early pioneers –recognizable by their high installed capacities – have been overtaken by othercountries. Today, the new renewable energies are a global reality, no longer dependent on the support from individual
countries.

Title picture
The shift to renewable power sources makes thereliable delivery of power a bigger challenge thanever before. ABB’s comprehensive wind and solar
power offering is helping to meet this challenge.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 4

ABB review 2|15

China

Japan

USA Germany Italy

1d PV: new capacity, 2013

Sources: Wind: Bundesverband Windenergie e.V., Deutschland; Photovoltaics: IEA-PVPS, IDAE, PV News, BSW, IWR

The strongest driver of this change isphotovoltaics, which – after the significant cost reductions at the end of thelast decade – has reached or fallen below grid parity in a number of countries.
That is, photovoltaics has achieved competitive end-consumer prices in low-voltage grids. ➔ 2  shows the developmentof the generation
costs of photovoltaic (PV) power compared withhousehold electricity prices inGermany. Photovoltaics is an economical option for
meeting the demand of individual households, provided
that the grid usage fee is largely energybased. This makes it independent fromdirect subsidiaries for a large scope of
applications as long as it reduces theowner’s own demand.

Remote generation

The share of remote generation of renewable energy is much higher than withpower plant systems in which a regionalbalance of generation and demand ispreferred for both economic and technical reasons. This development is mainly
driven by the heavily location-dependent

Remote generation, distributed genera­t ion and volatility
affect all areas of elec­t ric
power supply and utilization.

New renewable energy sources andsystem integration
New renewable energies have three mainfeatures that fundamentally change theelectric power supply system: remote
generation, distributed generation andvolatility.

sources of wind and water and can leadto very large generation units or clusters.
Distributed generation

The growth of distributed generation is
primarily driven by photovoltaics andcombined heat and power generation(CHP). For photovoltaics, this is mainly
due to the relatively low economies ofscale in terms of costs combined witheconomic performance, relative to theend-consumer prices in a low-voltage
grid. CHP must be distributed in order toprovide the heat close to the consumer.

The rising share of
renewable energies
is influencing theoperation of conventional power
plants.

2 PV generation costs* compared with household consumer prices in Germany

70
Cost of PV generation

euro cents/kWh60

Cost of electricity, German households

50
40
30
20
10
0
2000

2005

2010

2015

2020

Year
* 1 euro is equal to about $1.05.
Source: www.solarwirtschaft.de, Federal Ministry for the Environment, Nature Conservation, Building and Nuclear
Safety of Germany (Leitstudie 2010), BSW Solar (PV-Roadmap)

Very small PV systems in particular canlead to a considerable share of the generation being covered by a very large
number of smaller units feeding energy
into the distribution networks.

costs, they will always be placed at thelower end of the merit order in an energyonly market. This means they displace
conventional generation, reducing the utilization of conventional power plants andmaking fixed-cost coverage more difficult.

Volatility

Volatility is mainly introduced to the electric
power supply system by wind and solar
energy, both of which lead to faster, larger
and, especially in the case of wind energy,
less predictable fluctuations than before.
Remote generation, distributed generation and volatility affect all areas of electric power supply and utilization. An
overview of these areas, including theinfluence of new loads as drivers forchange, is given in ➔ 3.
Conventional provision of electricpower
The rising share of renewable energies isinfluencing the operation of conventional
power plants. The increased frequent
use of power plants originally intended
as base-load plants for loads following
operation with steep power output gradients poses a great technical challenge.
Using Germany as an example, the­e ffects of this change were investigatedin detail in [1]. The study concluded that
already in 2015 power gradients of up to
15 GW/h are expected for the conventional power generation park.
Another factor influencing the operationof conventional power plants is that, as
wind and solar energy have no variable

These economic effects mean that building and operating conventional power
plants is no longer attractive. But as conventional generating capacity is indispensable both as backup for periods oflow renewable power output and for
power system control, suitable adaptations of the market design are now being
discussed. ABB is deeply involved in thediscussions and is helping to shape themodern electric power supply system.
Transmission level
In transmission networks, remote generation leads to increased capacity requirements. Additionally, the volatility of
the generation – particularly in combination with the low number of full-loadhours of the renewable energies – increases transmission requirements. Expanding the interconnected power system represents the most cost-efficient
option to match volatile generation andconsumption [2].
The benefit of regional expansion for the
integration of a very high share of renewable energies into the electric power
supply is illustrated in ➔ 4, using the expansion of the European interconnected
power system to North Africa and the
Middle East as an example.

Putting it all together­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 5

The increasing
variety of operating
conditions in the
distribution networks increases
the information
requirements.

3 Effects of the main drivers for change on different parts of the electric energy supply andutilization value chain
Driver

System affected
Conventional
generation

Remotegeneration

Transmission– Long-distancetransmission– FACTS1– Overlay grid/
HVDC

Distributed
generation

Volatile
generation

Distribution– Part-load
capability– Flexibility– Trans-regional
leveling– Overlay grid/
HVDC– Bulk storage

New loads (eg,e-mobility)

Systemoperation

Application– Stabilization
with FACTS1– Automation– Voltage
regulation– Communication– Control– Virtual power
plants– Distributed
storage– Loadmanagement– Virtual power
plants– PMU/WAMS2– Charging
infrastructure– Demand
response– Storage (inapplications)– Demand
response

1 FACTS: flexible alternating current transmission systems
2 PMU/WAMS: phasor measurement unit/wide-area monitoring systems➔ 4 shows the costs for an additional
MWh generated from renewable sourcesin Europe, provided that the European
energy-political goals are met and thatfurther cost reductions for the plants areused. The cost advantage is a result ofsignificantly more ideal locations in North
Africa and the Middle East comparedwith Europe. The costs for the additional
required transmission capacity are taken
into account. This cost advantage directly benefits the plant operators, andrequires no special support apart fromreliable framework conditions. The othercost advantage shown in ➔ 4 is basedon a better balance of renewable energy
supply and demand resulting from thecomplementary seasonal variations ofwind and consumption in Europe andthe regions south of the Mediterranean
Sea. This cost reduction requires suitable consideration in the market design.

The transmission systems required under the circumstances described in ➔ 4will presumably be different from those of
the past. Considering the large transmission distances combined with the often
fundamentally changing load flow situations due to the high infeed peaks fromthe renewable sources, a superimposedtransmission level (overlay grid) based onhigh-voltage direct current (HVDC) transmission technology appears sensible.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 6

ABB review 2|15

A key component for this is the HVDC
circuit breaker developed by ABB [4].
Distribution level
The changes occurring in the distribution
networks are manifold. In many cases,
an increase in distributed generation requires a reinforcement of the grids. However, especially in rural grids with relatively long transmission lines, voltage
support problems occur first. As this is
not caused by the one load situation the
network has been designed for, but by
the multitude of operating conditions between feeding and extracting power, thetraditional solution of manually adapting
the transformation ratio of the local distribution transformer is no longer sufficient ➔ 5. In such cases, the often significantly more expensive grid reinforcement
can be postponed or even entirely avoided by installing a voltage regulator suchas a voltage-controlled distribution transformer (see, eg, [5,6]).
The increasing variety of operating conditions in the distribution networks increases the information requirements.
This leads to an at least partial automation of the distribution substations, which
thus far have been minimally monitoredor remotely controlled. Distributed generation as well as e-mobility (due to themobile nature of the consumers) will lead

4 Reducing the costs* for renewable energy by integrating the power supply systems ofEurope, North Africa and the Middle East [3]

75

73

15

30

euros/MWh

58

15

50
Generation andtransmission

25

0
Avg. direct costadvantage fordesert power

Avg. cost per
MWh of additional
generation in
EuropeAvg. cost per
MWh of additional
import from
MENA

Market price, directly
addressable by investors/
industry

Avg. systemsynergies (eg, lesscurtailment, fewer
peak load power
plants)Avg. total savings
per MWh imported

Ex­p anding theinterconnected
power systemrepresents themost cost-efficient
option to match
volatile generationand consumption.

System effects, must be
reflected by regulators/
governments* 1 euro is equal to about $1.05.
Note: cost of MENA (Middle East and North Africa) exports arriving in Europe includes cost of transmission losses
Source: Dii, Fraunhofer ISI

Due to the volatile
power output
associ­a ted withrenewable energies, the shortterm demand
response is gaining
in im­p ortance.
to an insufficient capacity of distribution
networks in some situations. This meansthat measurement and control will be required – and as every technical system,
including measurements, can be faulty,
the solution will be to transfer well-known
approaches from the transmission networks, such as state estimation, to the
distribution level and into the secondary
distribution systems.
If the grid is unable to offer sufficient capacity for all situations, possible congestion must be proactively detected
and resolved – a task that is not new inthe electric power supply domain. In
fact, it is common practice in the coordination between (large-scale) power

plants and system operators. Hence,the solutions for this electric power supply area must be largely standardized
and automated. An example of predictive distribution network operation,
which also takes the requirements ofthe deregulated market into account,has been developed and successfully
taken into operation within the scope ofthe MeRegio E-energy project in Germany [7].
Consumption
Due to the volatile power output associated with renewable energies, the shortterm demand response is gaining in importance. Demand-response measures,
particularly those involving loads with inherent storage, may contribute to this.
The requirements associated with thebalancing of loads and generation for different time domains, the solutions commonly used today and the solutions expected in the future are shown in ➔ 6.
This clearly shows that demand response
can make an important contribution especially in the first 15 min. This is an important period because it is sufficiently
long enough to ramp up power plants
with fast startup capability when generation capacity is suddenly lacking. Whether demand response can help in the very
short time frame in which the rotating
mass of power plants has a stabilizing

Putting it all together­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 7

Voltage (kV)

5 Change of the voltage support task in distribution networks with increasing distributed
generation (schematically)

Voltage (kV)A holistic approachconsidering the
supply of electricenergy as well asof heating andcooling is essential
for the utilizationof demand-side
flexibility options.

5a Past: Distribution; voltage is decreasingalong the LV lines and voltage band can be
guaranteed by a fixed setting of the
distribution transformer

5b Now and in the future: Distribution andfeed-in, resulting in a broader variation ofvoltage at the end of the line, possibly
requiring on-load voltage adjustments

effect today depends on whether an autonomous reaction of the load to imbalances between generation and consumption can be achieved. After 15 min
the use of demand response is only realistic for selected applications.

Future conventional generation will require plants that can be operated economically even at low loads and inf requently and fast-changing load­s ituations. The transmission networks­
will have to take over more long-distance transmission tasks with strongly
varying load flow situations comparedwith the past. To compensate for thevolatility of the new renewable sources,
wide-area interconnected systems suchas those proposed for the region­E urope-North Africa-Middle East within
the scope of the Desertec concept canbe an option.

Demand response is particularly suitablefor heating and cooling applications asthermal energy storage can in most cases
be implemented at a relatively low cost.
Hence, a holistic approach considering the
supply of electric energy as well as of heating and cooling is essential for the utilization of demand-side flexibility options.
Storage options
Storage is anotherimportant building
block for the integration of renewable energies. But
due to the variety
of applications andavailable solutions
it is a highly complex topic, which
requires a separate
discussion. Energy
storage is exploredin more detail in “A bright future” onpage 27 of this edition of ABB Review.

The transition from an electricity supply based on thermal power plants to a supply
using new renewable energies
as its main source will leadto a fundamental redesign ofpower systems.

The road ahead
The transition from an electricity supply
based on thermal power plants to a supply using new renewable energies as its
main source has technical implications in
all areas of electric power supply and utilization and will lead to a fundamental
redesign of power systems.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 8

ABB review 2|15

The consequences of the integration of
distributed generation into the distribution
networks will be particularly far-reaching,both quantitatively and qualitatively. Firstof all, an increase of grid capacity will be
inevitable in many cases. As the combination of extracting power from and feeding
power into the grid leads to a larger range
of operating conditions, additional voltage
monitoring and regulation will often be required. And finally it will no longer be sensible to design the distribution networks

6 Requirements for balancing generation and demand in different time domains and possible
solutions today and in the futureTime domain

Task

Traditional solutions

New solutions for the future<30 s

Instantaneous reserve,balancing of short-term
variations– Rotating mass of thepower plants– Battery storage–	Renewable energy resources
and load management may
also contribute<15 min

Minute reserve, balancingof short-term variations– Hydropower plants– Power plants on the grid
– Fast start-up power plants– Load management– Battery storage

1-3 dBalancing of diurnal variationsof the residual load

– Pumped storage– Power plants (fuel storage)– Pumped storage– Load management(selected applications)Weeks
to months

Balancing of annual variationsof the residual load

– Power plants (fuel storage)– Water reservoir(natural inflow)– Water reservoir(natural inflow)– Expansion of interconnected
power system

for rare extreme situations – this is mainly
due to the low number of full-load hours
associated with solar energy and becauseof e-mobility. Thus monitoring and control
down to the secondary distribution level
will be necessary.
Balancing loads and generation will become more difficult in systems with astrongly varying primary energy supply
that is not storable. Besides the proven,but landscape-profile-dependent pumped
storage plants, battery storage facilities
can contribute in the short term, eg, forfrequency stabilization and peak shaving. In the long term, ie, mainly for thecompensation of seasonal variations, thesystem boundaries will likely be expanded by extending the interconnected systems or interconnecting other systems
such as heat and gas supply.
The most significant changes in the system management will be the integrationof a very large number of distributed
units on both the generation and theconsumption side, as well as achieving
frequency control with a decreasing
number of rotating masses acting as­s tabilizing elements.
The greatest challenges in the necessary
further development of the systems are– from a more organizational perspective– the coordination of the required measures in all system areas and – from atechnical perspective – the developmentof suitable storage, the operation of thesystem without rotating masses and theintegration of large numbers of distributed units into the system management.
With its commitment to innovation, ABB

One of the mostsignificant changes
in the sys­t em management will be theintegration of avery large numberof distributed units,
both on the generation and theconsumption side.

continues to drive the growth of renewables, paving the way for the new electric power supply system.

Jochen Kreusel
ABB Smart Grids
Mannheim, Germany
jochen.kreusel@de.abb.com

References[1] VDE/ETG, “Erneuerbare Energie braucht flexible
Kraftwerke,” The Power Engineering Society(ETG) in the Association for Electrical, Electronic& Information Technologies (VDE), VDE-Verlag,
Frankfurt/Main, Germany, 2012.
[2] VDE/ETG, “Energiespeicher in Stromversorgungssystemen mit hohem Anteil erneuerbarer
Energieträger,” The Power Engineering Society(ETG) in the Association for Electrical, Electronic& Information Technologies (VDE), VDE-Verlag,
Frankfurt/Main, Germany, 2008.
[3] F. Zickfeld, A. Wieland, “Desert Power 2050,”
Dii GmbH, Munich, Germany, 2012.
[4] J. Häfner, B. Jacobson, “Proactive hybrid HVDC
breakers – a key innovation for reliable HVDC
grids,” presented at the CIGRE International
Symposium on the Electric Power System of the
Future, Bologna, Italy, 2011.
[5] ABB Ltd. (2013). Smart-R-Trafo Voltage
Regulation Solution for Distribution Transformers. Available: https://library.e.abb.com/public/
0803e28840f64334802c7c7c686b730a/
Smart-R-Trafo_leaflet_EN.pdf?filename=
Smart-R-Trafo_leaflet_EN.pdf[6] T. Hammerschmidt, et al., “Innovative concepts
for efficient electrical distribution grids,”
presented at CIRED 2011, paper 0447,
Frankfurt/Main, Germany, 2011.
[7] C. Franke, et al., “On the necessary informationex¬change and coordination in distribution
smart grids experience from the MeRegio pilot,”
Proceedings of the CIGRE International
Symposium on the Electric Power System of the
Future, Bologna, 2011.

Putting it all together­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­4 9

A growing need
Affordable irrigation with ABB’s solar pump drive
FILIPPO PAGANI – It is no secret that the world’s thirst for waterand energy continues to rise dramatically. But did you knowthat half of the world’s energy is used to operate pumps?
With agriculture’s reliance on irrigation, which depends onwater pumps, it is no wonder that so much energy is dedicated to this field. But plugging into a reliable or affordable
local power grid to operate a water pump is not always an­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 0

ABB review 2|15

option in many parts of the world. And so, ABB has turned tothe sun to develop an innovative solution that uses solar
power as a reliable energy source for pumping water. The
ABB solar pump drive, designed to use maximum power
point tracking and conventional drive technologies, enables
water pumps to run at maximum power proportional to theavailable solar power.

1 ABB’s solar pump drive system includes either an ACS355 drive or an ACSM1 drive.

S

olar pumping systems are increasingly being adopted foruse in a variety of applications.
For example, the systems arebeing used in community water supplies,
fish farming and agriculture, forestry, andwastewater treatment engineering. Thesesystems are also more frequently being
used for municipal engineering, city parks,
resorts, and even fountains in residential
areas – and, of course, for irrigation.
In some countries many small- and medium-sized farms are either off-grid or
receive only a few hours of electricity
each day. Often, the farmers’ only alternative is to run irrigation pumps withdiesel generators, which are costly tooperate – especially as water demandrises during the growing season, causing fuel prices to spike. Now, solar energy is playing an important role in theirrigation sector for agriculture aroundthe world.

Title picture
An Indian pump supplier has incorporated ABB’s
ACS355 solar pump drive into its pump technology,
enabling independence from the electricity grid andfrom diesel fuel.

1a ACS355 general machinery drive

1b ACSM1

Solar pump drive
In 2011, ABB developed a solution thatcombines ABB drives with solar panels
and a maximum power point tracking(MPPT) system that controls the pumpthrough solar radiation. Pump operators,
such as farmers, can then benefit fromthe maximum amount of pump output
over the course of the day. Comparedwith diesel generator pumps, the ABB solar pump drive is environmentally friendly
and has a long lifetime and low maintenance costs. It is independent from thegrid and produces no pollution or noise.

The complete system consists of four
components: a photovoltaic (PV) panel,a drive, a motor and a pump. The ABB
solar pump drive system uses a PV panel
as its power source, which is connectedto the direct-current (DC) connectors ofan ACS355 or an ACSM1 drive ➔ 1. The
drive is connected to the motor that runs
the pump ➔ 2.

The power range for the solar pumpdrive was recently extended from 0.37 to
18.5 kW up to 45 kW. This increased
power range enables the use of the solar

Maximum power with dual supply
The ABB drives provide uninterrupted
flow, even during drastic changes in irradiation, thanks to the MPPT algorithm.
Built-in MPPT functionality is also important for reliability when the equipment is installed at remote sites where
maintenance is minimal. Users canmonitor the pump remotely, from anywhere.
Embedded, pump-specific features suchas dry-run detection and sensorless flow calculation are used toprotect and monitor the pumping
station. The drive
is designed to­a utomatically shut
down to prevent equipment damage
from running the pump dry. Sensorlessflow measurement gives a direct indica-

In some countries manysmall- and me­d ium-sized
farms are either off-grid or
receive only a few hoursof electricity each day.
pump drives in larger pump applications
such as high-power pumps in agriculture
and solar desalination.

A growing need­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 1

In 2011, ABB
developed a solution that combines
ABB drives withsolar panels andan MPPT systemthat controls thepump throughsolar radiation.

2 The ABB solar pump driveDCACtion of the performance, allowing theend user to measure system performance based on flow rather than onelectrical parameters.
After dawn, when the sunlight is sufficiently intense to power up the drive, thedrive automatically starts the motor andruns the pump to draw water. At sunset,
the drive turns off the motor and the water flow ceases. When equipped with achangeover switch, it is possible to run
the drive from the grid – for example,
during the night or when maximum flowis required and not enough solar poweris available.
Compact and beneficial
The solar pump drive is preprogrammed
for specific pump applications with minimal parameter settings required. Other
benefits include: long pump life, elimination of restarting during DC voltage variations, and automatic fault-reset anda uto-start. The solution is also free of­other restrictions that can impact productivity, such as load shedding, electricity supply cuts and increased energy
prices, as well as burnt motors oftencaused by voltage fluctuations.

In some Indian states the government
funds as much as 86 percent of the costof solar pumps as a long-term investmentin the country’s agricultural output andsustainability.
There is demand for the solution in, forexample, Asia, South America and Africa
as well: Only around 6 percent of cultivated land in sub-Saharan Africa is currently equipped for irrigation. Even incountries that do not subsidize renewables, a number of financing alternatives
including rental programs, cooperatives
with shared ownership and micro-loans
are making solar water pumps economical for smaller off-grid farms.
With the world’s growing demand forboth water and energy, and environmental pressures showing no signs of easing,solar pumping is a viable short-term as
well as long-term solution. ABB is paving
the way for increased use of renewableenergy sources around the world.

A number of ABB’s low-voltage components such as relays, terminal blocks andcontactors are also used in the solution,
including PV-S miniature circuit breakers,
which are specially designed to safely
extinguish dangerous DC arcs in PV­a pplications.
Driving success
The ABB solar pump drive has been a
success in India, where ABB already has
thousands of installations.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 2

ABB review 2|15

Filippo Pagani
ABB Discrete Automation and Motion, Solar Pumps
Sesto San Giovanni, Italy
filippo.pagani@it.abb.com

Transforming
revenue
ABB’s technology cuts transformer losses
PATRICK ROHAN, TERO KALLIOMAA – Although transformers

have a high efficiency – typically above 99 percent – theindustry-wide energy losses from transformers are significant
simply due to the huge number installed. This is one reason
why environmental performance legislation is increasingly
regulating transformer performance. Just as important is thecost of these losses to operators: In a utility-scale solar

power installation, every Watt of power lost is one thatcannot be sold. Indeed, during the hours of darkness,
energy often has to be purchased to keep the transformer
energized, unless it can be disconnected from the network.
The obvious question then arises: How can operators reduce
losses and maximize the return on investment from theirtransformer fleet?

Transforming revenue­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 3

1 Most solar farms operate significantly below their peak output most of the time.
Example data for a solar plant at latitude 45.3 ºN.
4,500

4,205

4,000

Hours at % load

3,500
3,000
2,500
2,000
1,489

1,500
1,000

701

788

788

60 – 80

40 – 60788

500
080 – 100

20 – 40> 0 – 20

0

Hours (%)

T

he European Union Ecodesign
Directive, effective July 2015,
provides consistent EU-wide
rules for improving the environmental performance of energy-related
products. A transformer is one suchproduct and the directive requires alltransformers placed on the market tocomply with strict new design specifications that explicitly address transformer
losses. This trend toward the regulationof transformer losses is making owners
and developers of solar plants pay closer
attention to the overall costs of transformers – especially the factthat while thecapital costs of
the lower-loss
transformers
that are required to meet
new efficiency
directives may
be slightly higher than those of “standard” transformers, the lifetime costs arelower. The lifetime cost should take into
consideration not only the purchaseprice, installation costs, maintenancecosts, etc. but also the future revenue
not realized because of losses – a revenue loss that will be greater than the­initial purchase price.

Transformer losses
Transformer efficiency is impacted by the
inverter output: As the load increases, sodoes the transformer load loss. However,losses also arise when there is no load
as energy is consumed when voltage isapplied to magnetize the iron core. These
losses are independent of the load andwill be present as long as the transformer
remains energized.
The collector network of a utility-scalesolar plant, which includes transformers,
is sized to the peak inverter output. But,
averaged over a year, outputs usually do
not exceed 20 to 30 percent of the peakvalue ➔ 1. Geographical location and thetechnology employed – eg, tracking systems – cause production variation fromsite to site, therefore it is important toknow what the average of the inverter
output is so that transformer manufac-

It makes financial sense to use
lower-loss transformers: They
cost slightly more to purchase,
but increase lifetime revenues.

Title picture
Even though they are generally very efficient,
the sheer number of transformers in the field meansthat a substantial amount of energy is being lost.
How can operators reduce these losses andget more from their fleet investments? Pictured isa solar MV station including a low-loss transformer
and switchgear.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 4

ABB review 2|15

turers can customize their designs tominimize whichever loss component has
the greatest impact. In the case of solar
plants, no-load losses become a significant proportion of total losses becauseof the lower average output.
Comparing the cost of losses
Solar farm owners seek to maximize theirreturn on investment by operating as

2 Example data for a transformer capital cost and performance (transformer prices are forillustration purposes only)
Transformer options
TransformerkVA

Voltage(V)

No-load loss
(W)

Load loss(W)

Purchase price($)

1: Regular grain-oriented steel

2,500

20,000/400

2,782

23,682

21,6002: High-permeability steel

2,500

20,000/400

1,747

21,86125,7003 Energy comparison: The low-loss transformer results in increased annual revenue

Losses also arise
when there is noload as energy isconsumed whenvoltage is applied
to magnetize theiron core.

Energy sales for both transformers
Transformer 1

Loadfactor
(%)

Hours

100

  701

80

Energy sales(MWh)Transformer 2

Price($/MWh)Energysales ($)

1,733

130

225,349

1,735

130

225,609

  788

1,563

130

203,138

1,564

130

203,363

60

  788

1,174

130

152,565

1,175

130

152,739

40

  788

783

130

101,800

784

130

101,937

20

1,489

739

130

96,037740

13096,253

0

4,205

-12

-65

-760

-7

-65

-477

Total

close to capacity as possible, while minimizing losses across the collector network. Capital investment aimed at lowering losses and increasing efficiency isdecided upon depending on the calculated return. As an example of such anevaluation, two liquid-filled transformers
can be compared: One using a grainoriented steel that exhibits “standard”
losses and a low-loss unit, using a highquality, high-permeability steel that conforms to the new EU directive. The costof future losses based on the loading
profile shown earlier can be calculated
for these two, assuming:– The average price of energy sold is$130/MWh.
– The average price of the (nighttime)energy purchased is 50 percent of
average selling price.
➔ 2 – 3 compare the net energy sales forthese two transformer types. Transformer 1 is the standard unit and has a cumulative total of 5,960 MWh available to sell,
which would yield a revenue of $778,128.
Transformer 2, which has lower losses
and uses Hi-B core steel, has 5,992 MWhavailable to sell, resulting in a revenueof $779,424. Therefore, the lower-loss
transformer increases revenue by $1,296

778,128

Energy sales
(MWh)

Price
($/MWh)Energysales ($)

779,424

per year. This illustration is for a 2.5 MW
installation, however the saving can bescaled up linearly for larger installations.
Note the negative energy sales during
times of zero inverter output, indicating
the solar site is purchasing power fromthe grid to energize the transformer andcollector network ➔ 3. This represents
the no-load or core losses that are­a lways present when the transformer isenergized.
After the revenue calculation, the next
step is to calculate if the additional purchase price for the lower-loss transformer is worth the investment. The calculation incorporates the initial purchasecost of the transformers and the increased annual revenue that can beachieved with the increased efficiency ofthe lower-loss transformer over its lifetime (assumed to be 20 years).
The financial argument for using lowerloss transformers can be examined
more closely by calculating the NPV (netpresent value) and the IRR (internal rateof return), using an interest rate of 8
percent. The power purchase agreement (PPA) price sensitivity graph in ➔ 4Transforming revenue­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 5

4 The PPA price sensitivity graph shows an IRR and NPV of the additional investment atvarying PPA prices.

12,00050
45

10,000

40

30
6,000

25
20

4,000

IRR (%)

35

8,000
NPV ($)

Depending on thesite’s geographic
location and theprice paid fornighttime energy,
it can also be
worthwhile to­c onsider switching
the transformer
out of the circuit
altogether to savethe nighttime­e nergy cost.

15
10

2,000
NPV

5

IRR

0

0
100

110

120

130

140

150

160

Power purchase agreement price ($/MWh)shows an IRR and NPV of the additional
investment at varying PPA prices. A$130/MWh PPA would yield an IRR of
39 percent and an NPV of $8,726. Thismeans the additional cost for the lowerloss transformer is indeed a good investment.
Switching out to save
Depending on the site’s geographic location and the price paid for nighttime­e nergy, it can also be worthwhile to consider switching the transformer out of
the circuit altogether to save the nighttime energy cost. This can be donewith the help of medium-voltage (MV)switchgear.

In utility-scale solar plants, there isswitchgear on the MV side of each of thetransformers to protect them and the MV
network from harm. The switchgear is­either directly beside the transformer orfurther away in a collection station or gridconnection substation, depending on thesize and the design of the power plant. In
order to break the current, the switchgear is equipped either with a fuse switch
or a circuit breaker. While motorized fuseswitches can be operated up to 1,000
times, the circuit breaker can be operated several thousand times.
Equipping switchgear with motorized circuit breakers and remotely controlled
protection relays
allows automatic,or remotely operated, opening andclosing schemes
to de-energize thetransformers. The
additional investment required depends on the plantdesign and can involve simply changing fuses to circuit
breakers, motorizing existing circuit
breakers or adding motorized circuit
breakers. The protection relays may alsoneed to be changed or have communication equipment added to enable remote control of the circuit breaker.

Equipping switchgear withmotorized circuit breakers andremotely controlled protection
relays allows automatic, or
remotely operated, opening
and closing schemes tode-energize the transformers.
ABB has a wide selection of switchgear
suitable for application in solar installations – for example, SafeRing/SafePlus
or UniSec secondary switchgear. ABB’s
green policy ensures a focus on environmental factors during the manufacture and over the life span of the switchgears.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 6

ABB review 2|15

The savings achieved by doing this depends on the length of time each day thepanels are not producing electricity and5 Energy purchase price sensitivity of the additional investment for switchgear on NPV and IRR for the
regular grain-oriented steel transformer, for the case where the existing circuit breaker is motorized
7,000

140
130

6,000

120
110
100

4,000

90
3,000

80

2,000

70

IRR (%)NPV ($)

5,000

60
1,000

NPV

50

IRR

40

0
30

40

50

60

70

80

90

Nighttime energy purchase price ($/MWh)how many mechanical operations thecircuit breakers can withstand. Obviously, in solar power plants, no electricity is
produced at nighttime and to de-energize a transformer every night and reenergize it every morning over a 20-year
lifetime, each circuit breaker would haveto be operated 14,600 times. This posesa challenge because the circuit breakers
in secondary switchgear are usually limited to a maximum of 10,000 mechanicaloperations.

$580 per year of energy savings, assuming energy costs of 65 $/MWh and thatthe transformer was de-energized during
winter when the nights are longest andsolar irradiation lowest. This adds up to
3,226 hours and 9 MWh energy savings
annually in the case of Transformer 1(compare with ➔ 3). The return on the
additional investment would be a 97 percent IRR and $4,750 NPV. Therefore, theadditional investment in motorized circuit
breakers would be worthwhile ➔ 5.

In smaller power plants (under 10 MW),the solution is to either replace the circuit
breaker after 10,000 operations or simply
limit the number of operations to this figure over the transformer lifetime. In larger
solar power plants, which utilize primaryswitchgear either in the collection stations or in the grid connection substation,
it may be viable to invest in motor-operated circuit breakers that are capable of
30,000 mechanical operations. While
more expensive, the number of circuit
breakers required would be fewer because the primary switchgear in collection substations and grid connection
substations is connected to several MV
stations within the facility.

Savings are heavily dependent on plantdesign: If circuit breakers were alreadyplanned for, simply motorizing themwould enable the operator to de-energize the transformers. In installations
with smaller transformers in which thefuse-switch option is viable, changing
them to motorized circuit breakers may
also be a good investment – dependingon the energy costs.

For example, ABB’s UniSec secondary
switchgear can be fitted with a circuit
breaker capable of 10,000 operations at
up to a 24 kV voltage level. A UniSec
switchgear with a motorized vacuum circuit breaker could cost the site developer as little as $ 600 more than a nonmotorized option. However, the savings
from de-energizing the transformers
overnight would generate an additional

Savings are heavily
dependent on facility design: If circuit
breakers werealready planned
for, simply motorizing them would
enable the operator to de-energize
the transformers.

ABB can offer support in both the internal power plant network design and theselection of the appropriate products toreach the most optimal solution fromboth the original investment and total
cost of ownership point of view.

Patrick Rohan
ABB Power Products, Transformers
Waterford, Ireland
patrick.rohan@ie.abb.com
Tero Kalliomaa
ABB Power Products, Medium Voltage Products
Vaasa, Finland
tero.kalliomaa@fi.abb.com

Transforming revenue­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 7

Nextgeneration
components

1 Example of photovoltaic applications: commercial 20g

Advanced low-voltage components
for next-generation 1,500 V DC
utility-scale PV solar applications
ALLEN AUSTIN, FEDERICO MAI – Solar photovoltaics is the fastest growing

renewable energy source in the world and ABB, a leading industry
supplier, is committed to meeting the needs of this rapidly developing
industry by providing a complete portfolio of products, systems andsolutions for photovoltaics applications. To date it has met the challengeof the next-generation advanced component design by introducing a
new line of 1,500 V DC low-voltage components that ensures safe
processing of 1,500 V DC power, including reduced power losses,
reduced number of poles, visible blade technology, integrated heatdissipating and advanced arc extinguishing technologies.

As the solar photovoltaic (PV) industry continues to become anincreasingly important share of
the energy mix, the balance ofsystem component technology is continually evolving to help lower the cost ofenergy production. In the past few years,
the industry has seen a tremendous
jump from 600 V DC inputs to 1,000 V
DC inputs, which represent the majorityof utility-scale solar PV installations. The
next step in this trend is systems with1,500 V DC inputs, which, by increasing
the voltage level, enable higher power
output capability by up to 50 percent –thus decreasing system losses and balance-of-plant costs.
ABB has developed 1,500 V DC low-voltage components in order to process thisnew power. These components include
switches, molded-case circuit breakers,
contactors, surge protection devices­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 8

ABB review 2|15

and voltage/current sensors. Some components are rated up to 3,000 A / 1,500 V
DC and carry various certifications, UL
and IEC included.
Adapting to the solar market
Clearly 1,500 V DC is not new – for instance it is used in rail applications – butadapting it to the solar market hasbrought certain challenges.
A major challenge has been the issue ofhigher voltage requirements affecting thedesign of the system and insulation requirements. Temperature is an additional
aspect that has to be addressed withcomponents in the PV plant having tooperate at higher temperatures, often
reaching 70° C. Additionally, components for the 1,500 V DC PV utility-scaleinstallations may have to be designed forbidirectional current flow.

t

f

c

s

The new products also ensure safe processing of 1,500 V DC power, as well as
reduced power losses, reduced numberof poles, visible blade technology, integrated heat dissipating and advanced
arc extinguishing technologies.
In addition to the increased voltage, thenew products can also handle more current – up to 6,000 A depending on thedevice. This allows for utility-scale PV
combiner boxes and inverters to handle
more power. Some of the new products
can handle two 1,500 V DC inputs simultaneously.

to 1,000 kW
x

b

v

w

u

r

l

k

Id

c

d

h

kWh

kWh

ID+GPD

q

h

p
e

j

k

n
m

i

o
kWh

Id

kWh

ID

a

Low-voltage productsa – Contactors: GAF series, IOR bar contactors
b – DC string boxes:
		 Switchboards: Gemini series,
		 Consumer units: Europa seriesc – Fuse disconnectors: E 90 PV; Fuses: E 9F PV
d – Surge protective devices: OVR PV
e – Fuse disconnectors: E 90
f – Switches: OTDC series,
		 Miniature circuit-breaker disconnectors: S800 PV-M
g – Miniature circuit breakers: S800 PV-S
		 Miniature circuit breakers: S200 M UC Z
h – Switch disconnectors: Tmax PV

Already a leading supplier for all photovoltaic applications, ABB can now also provide advanced solar components to its
customers that will allow them to begin
their own next-generation 1,500 V DC PV
utility-scale designs, thus enabling them
to benefit from higher efficiency and­reduced costs for their systems  ➔ 1.

i – 	M olded-case circuit breakers: Tmaxj – 	S urge protective devices: OVR T1 / T2
k – 	C ontactors: A and AF seriesl – 	Insulation monitoring devices: CM-IWN
m – Power suppliesn – 	E nergy meters: EQ meterso – 	Residual current device blocks: DDA 200 B
Residual current devices: F202 PV B and F204 B
Miniature circuit breakers: S 200
p – CM-UFD.M22
q – ArTu switchboards

Solar invertersr – Central inverters: PVS 800
		 Remote monitoring portal
String monitorings – 	P LC AC500
t – 	C urrent Measurement System (CMS)
Medium-voltage productsu – 	S econdary switchgearv – 	D ry-type transformers
w – Liquid-type (oil-filled) transformers
x – 	C ompact secondary substations

Allen Austin
ABB Low Voltage Products
Houston, TX, United Statesallen.austin@us.abb.com
Federico Mai
ABB Low Voltage Products
Sesto San Giovanni, Italy
federico.mai@it.abb.com

Next-generation components­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­5 9

Self generation
Photovoltaics play an essential role in
ABB’s Active Site technology
LEONARDO BOTTI, PHILIP JUNEAU – What is the best way to connect rooftop photovoltaic panels, and how can users

deploy them optimally? Photovoltaic technology has undergone a rapid transformation, both in terms of performanceand cost, and is reaching the brink of competitiveness with conventional generation. Its installation is already viablewithout recourse to subsidies and incentives, and even with subsidy protection being decreased or abolished in many
countries, the sector is continuing to see strong growth. However, the shift from conventional generation to solar
generation is not just about replacing one source of power with another. It is also about a shift from centralized to
distributed generation. With commercial, communal and industrial sites consuming and generating electricity as wellas possibly having on-site storage, these sites are increasingly developing into microgrids. These microgrids need to
be optimally managed and connected to the macrogrid. This is the role of ABB’s Active Site technology.1 This technology provides broad and comprehensive support for the emerging needs of the market. ABB provides an ideal solution
for connecting and managing on-site photovoltaics (PV) using a broad range of state-of-the-art three-phase string
inverters, including compact and outdoor devices and fast responding maximum power point tracking (MPPT).

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 0

ABB review 2|15

1 Annual installed unsubsidized commercial and industrial PV

20,000MW

15,00010,000

5,000

0
2015

2016

2017

2018

2019

2020

Year
Source: IHS, BNEF

S

ubsidies for photovoltaics (PV)in the main European markets
have become unviable and arebeing scaled down. Other mature markets will soon be seeing the same
trend. But this is not bad news for solar
energy generation. Significant cost reductions and rising retail tariffs have turned
PV from a heavily subsidized and marginaltechnology into a mainstream and competitive source of power. Not only commercial users, but also residential households, are installing solar generation
systems on their roofs to reduce theirelectrical bills. The self-consumption
model, enabling residents to become“pro-sumers,” means they can use energy generated on the premises, while also
being able to either sell surplus or buy additional power as needed. Presently, such

installations can be achieved without subsidies and can attain an IRR (internal rateof return) of more than 6 percent anda payback period of under 10 years (withan equipment life span double this). The
figures are evenmore encouraging
for commercial build­ings and industrial
complexes where
the IRR can rise
above 10 percent
and the payback
time fall below seven years – making
them the best candidates to implement Active Site technology. Active Site
can control and optimize the microgrid
and its interface to the macrogrid, ensuring an optimization of energy usage andcosts while permitting the microgrid tofully participate in the smart grid.

including the major utilities, whose role
will shift from being energy providers tocomprehensive energy service companies ➔ 2. Their ability to make this transition will be a key market success factor.

Presently, photovoltaic
systems can be built
without subsidies and cangenerate an IRR of morethan 6 percent.

Title picture
Hospitals, campuses and factories, rather thanbeing pure consumers of electricity, are increasingly
also generating it. This picture of ABB’s inverter
factory in Helsinki, Finland shows the company is
no exception. ABB’s Active Site technology canhelp manage such sites and connect them to thegrid.

In mature markets such as Europe andthe United States the self-consumption
model appears to work well, being financially viable and overall self-sustainable.
Many analysis and research studies forecast that over 20 percent of electricity
demand will be replaced by self-produced solar power by 2020 in thesecountries, thanks to over 60 GW of unsubsidized roof installations planned tooccur within this timeframe ➔ 1.

Footnote
1 For more information regarding ABB’s Active Sitetechnology, please refer to “Active Site” onpage 34 in ABB Review 4/2014.

In this scenario, with customer needs
reaching a higher complexity level thanever before, competitiveness will be evenmore challenging for all energy providers,

Enabling factors will be:– Smart distribution capabilities (ability
to master the technological complexity of the evolving grid)– Expertise in energy management(experience in grid management aswell as the necessary hardware andsoftware tools)– Technical prowess (expertise, professionalism and experience as well as
recognition by customers and end
users)
Distributed generation with PV
An electricity bill is an important expense
at all consumption levels, from a single
apartment to a large industrial complex.
Being able to manage and control energy
consumption is an important factor incost control. On a commercial or industrial campus there are many different
load profiles, characterized by individual
buildings and objects. These profiles are

Self generation­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 1

2 Energy services environment presenting the greatest potential for utilities
Ancillary services

Transmission
Distribution

Tech support

Power generation
using small andflexible modules
within the electrical
grid is crucial toachieving a truly
decentralized­e lectrical system.

Dataexchangeheavily influenced by factors such as theweather, hourly usage profiles, etc. To
manage this users must first implement a
process to measure, analyze and determine the demand and consumption profiles on an equipment or asset level. Thisis possible by harnessing the plethora ofenergy meters, sensors and other measurement components within the building automation system.

cluded) of 17 cents/kWh (0,156 EUR/kWh),results in a substantial savings of over
$150,000/year (140.000 EUR/year) witha payback of slightly more than six years
and an IRR of 11.5 percent. ABB’s solution to achieving this goal is combining
24 units of TRIO-27.6-S2X and a single
VSN-700-05 monitoring system, alongwith environmental sensors, low-voltage
breakers and ancillary protections.

Combining this data can not only provide
a detailed and precise overview of present load profiles, but also help better
forecast future ones. With this detailed
data available, and combined with otherpertinent information about the site,­d etermining the best on-site generation
capability is a relatively small next step.

Local intelligence and virtual power
plantsPower generation using small and flexible
modules within the electrical grid is crucial to achieving a truly decentralized
electrical system. An Active Site featuring
distributed solar generation is the mosteffective way to attain this goal. Undercertain conditions, such installations canbecome virtual power plants (VPPs), featuring a continuous exchange of data between microsites and the grid. VPPs enable the provision of system services inthe transmission and distribution network(eg, control power in the so called “minutereserve capacity”) configured by combining loads from end-use equipment withemergency generating units and distributed generation. The VPP aggregates theelectrical output from a multitude of objects and makes this supply available tothe distribution system. When requested,
the VPP controls the immediate dispatchof electrical output to the connected
plants, contributing to grid stability.

To use a real-life example, a small industrial plant in Italy is evaluated ➔ 3. The
plant, which manufactures plastic enclosures, was seeking to improve its energy
performance by installing a PV installation on its roof. Following a detailed analysis of the electricity demand and consumption, with over 10.6 GWh annual
power expenditure, a profile was deter­
mined ➔ 3b.
The shape of the curve is a good representation of the load activation time andperfectly matches solar availability ➔ 3a.
Through simulations and analysis of all
the different variables, ABB determinedthat the most effective solution was a
700 kW PV installation. This solution permits the site to consume 1.1 GWh/year
and, assuming an electricity rate (taxes in­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 2

ABB review 2|15

ABB’s three-phase string inverters fitted
in industrial campuses as well as in commercial buildings play a crucial role in800,000

800,000

700,000

700,000
Consumption profile (Wh)Energy balancing (Wh)3 Real world example: factory in Italy

600,000
500,000
400,000
300,000
200,000

600,000
500,000
400,000
300,000
200,000
100,000

100,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time (h)Time (h)PV self-consumption

Buy from grid

Machines

Lighting

Electric consumption

PV energy

HVAC

Other

3a Daily energy balancing at site with local PV

bringing these Active Sites to the VPPlevel. Thanks to their multiple maximum
power point tracking (MPPT), these inverters can maximize site production.
Looking at grid requirements in detail,the ABB inverter product lines PVI,TRIO and PRO provide a wide range ofreactive power and fault ride throughfunctions. Coupled with frequency/
voltage management control, they
make an important contribution to network stability. The benefits of VPPs forenergy providers include:– The option of “trimming” electricaldemand peaks, thus securing a higher
stability level for the energy production facilities. This indirectly provides

3b Daily consumption profile for the site

– Avoids replacement of old and/or
obsolete power plants with new
power generation facilities (capex
avoidance). This is a critical item inmany countries where massive
investments are the main alternative.
– Reduces expenses on legacy grids byleveraging the Internet of Things withthe use of applications (apps) via
smart tablets and smartphones. Such
end-user apps will help reduce
general and administrative efforts.
– Extraordinary ability to perform
real-time diagnostics when faults
occur with the opportunity to perform
effective preemptive interventions,thus saving on maintenance expenses(opex).
Communications
Optimizing a site’sself-consumption
is the way to makethe most of solarbased electricity,
but to do so requires a continuous and reliableexchange of data
between the different participants inthe decentralized electrical system, namely
generators, loads and the grid. ABB’s
Active Site architecture bases its communication on multiple protocols to ensurethat all possible inputs are analyzed andmanaged by the Active Site control system.
The system’s communication connects
loads, switches, sensors and meters anddistributed solar generators. Algorithms

and operating schemes provided by thegrid operators balance the energy operation of the site with the aim of minimizing
wastage and meeting network fluctuations. ABB solar inverters can communicate using a range of protocols including
ModBus, TCP/IP and RS 485 as well as
open gateways. They are fully integrated
into the building automation system andcan exchange data continuously with theoverall Active Site energy management
system.
PV installations are a vital part of ABB’s
Active Site concept. Coupled with acompany’s energy storage and building
automation technologies, the PV installations have a vital part to play in energy
independence and sustainability.

Algorithms and operating
schemes provided by the grid
operators balance the energy
operation of the site with theaim of minimizing wastage andmeeting network fluctuations.
consistent savings in terms of theadditional costs otherwise required tomeet higher peaks for short periods.
– Reduces the need for backup
systems due to the lower consumption and the better energy flow
management achieved. This allows
closing legacy generation plants(capex reduction).

Leonardo Botti
ABB Discrete Automation and Motion,
Power Conversion
Terranuova Bracciolini, Italy
leonardo.botti@it.abb.com
Philip Juneau
ABB Low Voltage Products, Building Automation
Zurich, Switzerland
philip.juneau@ch.abb.com

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Steady as a rock
Two PCS100 AVC products now designed
for different applications
DARIO ROZMAN – Even developed countries equipped withmodern power networks are not immune to voltage problems.
While outages may be rare, the voltage problems caused byweather, network faults or “digger-through-the-power-cable”
type events are ever-present. With modern industry employing more and more automation, the sensitivity of processes tosuch power quality events is increasing. Even an event lasting
less than a few cycles can cause processes to unexpectedly
stop – potentially resulting in product damage, wastage and­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 4

ABB review 2|15

production shortages. In developing countries, or regionswith a weak power supply, the main problem is poorly
regulated voltage. Without the correct voltage, the reliable
process operation may not be possible. If the voltage is low
or imbalanced then the overheating of motors is a particularconcern. ABB’s PCS100 AVC products are designed toprotect industry from voltage events, allowing companies
to get on with what they do best.

1 PCS100 AVC-40 schematic

Utility voltage

PCS100 AVC-40
compensating voltage

Input
circuitbreaker

Load voltage

Injectiontransformer

PCS100 AVC-40

Three-phaseutility supply

Auxiliarycircuitbreaker

Autotransformer(220 V models only)

Three-phase
protected load

Inverter &bypass

Rectifierpower – ABB’s PCS100 Active Voltage
Conditioner (AVC).

O

ften, industrial sites are located close together – for example, in an industrial park or
in a particular area of a city. If
one user in this cluster disrupts the utility
voltage – by starting a large motor, forexample – the others can be affected bypower supply sag or fluctuation. Weather
events or faults in other parts of the utility network can also cause the voltage to
sag well below its nominal value and staythere for many cycles.
Such voltage variations can cause sensitive production equipment to stop. If a
production line stops, it has to be restarted and this can be a complicatedand very expensive exercise. Equipment
damage caused by power quality events
can be even more costly. Further, equipment can be very dependent on a stable
power supply to deliver a good-quality
end product.
It is best, then, for companies exposedto the risk of an uncertain power supply
to invest in equipment that ensures aconstant supply of clean, high-quality

Title picture
ABB’s PCS100 AVC corrects voltage sags orfluctuations and ensures a supply of high-quality
power to critical loads.

The PCS100 AVC product
ABB has a variety of power protection
products and the PCS100 AVC is uniqueamong these. Specifically designed forindustrial and large commercial applications, the PCS100 AVC is able to re-current required to make up the correction voltage from the utility supply. Without the ongoing maintenance costs typically associated with batteries, the costof ownership of PCS100 AVC systems isvery low.
Furthermore, the PCS100 AVC contains
a bypass system that, in the event of a
fault within the
PCS100 AVC, ensures that the load
continues to besupplied from theutility.

The PCS100 AVC-40 responds
to voltage sags or swells
within several milliseconds
and can inject up to 40 percent voltage correction.
spond instantly to voltage sags andsurges, correct for voltage imbalancesand remove voltage flicker.
The PCS100 AVC consists of two converters that are not in the current path
between the load and the utility. Instead,the corrective voltage injection isachieved by means of a transformer
winding placed between the utility andthe sensitive load ➔ 1 – 2. This configuration delivers a very efficient and effective
voltage correction.
The PCS100 AVC does not require battery storage as it draws the additional

The PCS100 AVC
is available withratings from 150 kVA
to 3.6 MVA and isrealized in a lowvoltage switchgear cabinet ➔ 3. It offers
precise online voltage control, a provenand dependable converter platform, sophisticated control software and an efficiency of 99 percent. The PCS100 AVC
product portfolio now has two products
designed for different applications:– The PCS100 AVC-40 – designed forcustomers who have a stable network, but one which may be susceptible to voltage sags caused byexternal factors such as weather, etc.
– The PCS100 AVC-20 for continuous
voltage regulation. This product isideal for customers whose network is
weak and unstable.

Steady as a rock­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 5

The PCS100 AVC
does not needbatteries as it
draws the additional current
required to makeup the correction
voltage from theutility supply.

2 The PCS100 AVC

Each product is specifically engineered
to fix different types of common utility
power supply problems.
PCS100 AVC-40 Active Voltage
Conditioner for sag correction
The PCS100 AVC-40 responds to voltage sags or swells within several milliseconds and can inject a voltage correction of up to 40 percent. For example, if
a facility was faced with a voltage thatsagged to 60 percent of its nominal value, the PCS100 AVC-40 would boost thevoltage back to 100 percent. No lights

The PCS100 AVC
contains an internal bypass systemthat, in the eventof a fault with the
AVC, ensures thatthe load is continually supplied fromthe utility.
would dim and no equipment would trip
– business would go on as usual. This
example applies to three-phase power;
performance is even better for singlephase sags (the most common type):­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 6

ABB review 2|15

voltage sags down to 45 percent of thenominal voltage are fully corrected.
For three-phase sag events, the PCS100
AVC-40 can restore voltage that hassagged to 50 percent back to the 90
percent level, thus guaranteeing continued plant operation. The AVC can sustain this correction for 10 seconds. This
performance amply covers the sag durations experienced by customers. Thus,
plant operation is well protected against
the two main aspects of voltage sags –depth and duration.
For single phase, the PCS100 AVC-40
can correct sags of up to 30 percent
remaining voltage back to 90 percent,­guaranteeing continued plant operation.
The AVC can perform this correction for
10 seconds at this voltage level. Again
this is more than covering the sag durations experienced by customers.
In addition, the PCS100 AVC-40 is able
to continuously correct voltage fluctuations of ±10 percent in the mains voltage
and even remove imbalances from the
supply voltage.
The product is rated from 150 kVA to
3.6 MVA and is available for 220 V, 400 V
and 480 V. Special voltages and powers
up to several MVA are available as customized designs.

3 PCS100 AVC-20 schematic

Utility voltage

PCS100 AVC-20
compensating voltage

Input
circuitbreaker

Load voltage

Injectiontransformer

PCS100 AVC-20

Three-phaseutility supply

AuxiliarycircuitbreakerThree-phase
protected load

Inverter &bypass

Rectifier

PCS100 AVC-20 Active Voltage
Conditioner for voltage regulation
Rated at up to 3 MVA, the PCS100 AVC20 ensures continuous voltage regulation to 100 percent for voltage fluctuations of ±20 percent of the mains voltage.
The PCS100 AVC-20 also removes any
imbalances from the supply voltage ➔ 3.

The PCS100 AVC-40 and AVC-20 products both feature a large touch-screen
LCD, through which the device can be
operated and detailed event logs accessed. An integrated Web server allows
remote access and emails can be sent tothose concerned when a power quality
event occurs.

If the voltage fluctuations are even higher, the PCS100 AVC-20 will undertake apartial correction, with a voltage injectionof up to 20 percent. For example, withmains voltage drops of 30 percent, it
corrects to 90 percent of the nominal
voltage – keeping voltage levels inside
standard specifications of most electricalequipment.

Modern factories with sophisticatedequipment face continuous threats frompower utility network events such assags and surges. By installing ABB’s
PCS100 AVC they are equipping themselves with a sophisticated layer of protection that improves their bottom line bydramatically reducing downtime, scrap
material, poor product quality, lost production time and reduced plant maintenance.

Common features
The PCS100 AVC has several advantages
over competitors’ devices:– Small dimensions: Space is often an
issue in industrial environments andthe compact dimensions of the
PCS100 AVC allow it to be installedin small spaces.
– High reliability: An integrated bypass,
and industrial-grade overload andfault capacity contribute to the highreliability.
– Lowest total cost of ownership:
The absence of energy storage(batteries), low maintenance and highefficiency mean running costs are low.

Rated at up to
3 MVA, thePCS100 AVC-20
ensures continuous
voltage regulation
to 100 percent forvoltage fluctuationsof ±20 percent of
the mains voltage.
It also removes any
imbalances fromthe supply voltage.

Dario Rozman
ABB Discrete Automation and Motion
Napier, New Zealanddario.rozman@nz.abb.com

Steady as a rock­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 7

Safe andpowerful
Dry transformers for subtransmission
MARTIN CARLEN, MARIANO BERROGAIN – ABB’s recent innovative power transformer,
the HiDry72, is now in operation in a number of substations around the globe.
With HiDry72, ABB has paved the way for dry-type transformer use to move from
distribution applications into the subtransmission voltage range. The very capableand very safe oil-free technology behind this power transformer now allows
substations to be easily integrated into any building, with full peace of mind.
HiDry72 is particularly beneficial for substations located in cities and busy publicvenues with hefty power requirements.

Title picture
Salvador da Bahia in Brazil, with the Arena Fonte
Nova stadium, which contains a 69 kV substation,equipped with 69 kV / 25 MVA dry-type transformers. Photo credit: World Cup Portal.

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ABB review 2|15

Safe and powerful­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­6 9

nounced the launch of a dry-type powertransformer for the 72.5 kV voltage class– HiDry72 [1]. HiDry stands for “high-voltage dry”; the superscript “72” indicatesthe 72.5 kV voltage class.
Those responsible for the project were
intrigued by the idea that fire- and explosion-proof dry transformer technology
could now be used not only for mediumvoltage (MV) applications, but also forhigh-voltage (HV). It also became clearthat dry transformers allowed the moststraightforward design and layout, provided the most cost-efficient solution
and that their use would remove any
safety concerns about integrating thesubstation into the stadium. Safety is a
primary aspect in a venue attended bytens of thousands of spectators.

A

number of new stadiums
were erected for the 2014
FIFA World Cup in Brazil. Oneof the stadiums is the Arena
Fonte Nova in Salvador da Bahia, a cityof 2.7 million, located on the Atlantic
coast in central Brazil. The stadium has
55,000 seats and is located in the centerof the city ➔ title picture.
Electric power is supplied to this part ofthe city by a 69 kV subtransmission cableline. With the demolition of the old stadium and construction of the new one, anearby outdoor substation had to be­replaced. The substation site was on aplanned recreational space, so the local

Dry transformer technology
In contrast to oil-insulated transformers,
dry transformers are air-insulated. Thishas pros and cons: The dielectricstrength of oil is about eight times that ofair, so the dimensions of an oil-immersed
transformer core and coils are smaller
than the air-insulated equivalent. On theother hand, dry transformers need nobushings and oil spills cannot occur.
Their major advantage, though, is thelack of inflammable oil and other combustible materials. While a typical powertransformer contains several thousand
liters of inflammable oil, the insulationmaterials used in fire class F1 dry transformers are self-extinguishing. Dry transformers also provide an alternative togas-insulated transformers and are safer
to handle.
There are a number of different technologies used for dry transformers – likev acuum cast coil­
(VCC), RESIBLOC®
and Open Wound– with each offering different special features. ➔ 1shows the main
components of a
VCC transformer.

Dry transformers need nobushings and oil spills cannot
occur. Their major advantage,
though, is the lack of inflammable oil and other combustible materials.
energy provider came up with the idea of
integrating the new substation into thestadium under construction. Fortuitously,
this was at the same time that ABB an-­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7 0

ABB review 2|15

Between the primary and secondary coil of a VCC
transformer is an air duct. Since the­dielectric constant of the solid insulationmaterial around the winding is higher thanthat of air, the electric field is mainly taken1 Dry transformer

2 HiDry72 characteristics
Primary voltage

Up to 72.5 kV

Rated power

Up to 63 MVA

h

Lightning impulse
voltage

325 kV for IEC
350 kV for ANSI/IEEEc

Short-duration ACwithstand voltage

140 kV for IEC
140 kV for ANSI/IEEE

Secondary voltage

Up to 36 kV

Connection group

Y or D

Partial discharge<10pC

Insulation classF (155°C) or H (180°C)

Environmental class

E2

Climatic class

C2

Fire class

F1

Cooling

AN, ANAF, AFAF, AFWF
A: air
W: water
N: natural convection
F: forced convection

Tapping and OLTC

17 positions (± 8 x 1.25%)

EnclosureNo enclosure, or IP and
NEMA (National Electrical
Manufacturers Association)indoor or outdoor enclosure
according to requirements

g

b

a

e

f

a – Primary coil (HV)b – Secondary coil (LV, inside)c – HV coil terminal (top)d – HV coil terminal (bottom)e – Delta connecting bars
f – Taps
g – Transformer coreh – Core clamps
i – Entry of cold cooling air

diup by the air in the duct. The size of the
air duct needs to be large enough to withstand lightning impulse testing. Eachtransformer is tested for partial discharge(a partial discharge level below 10 pC is
required). This guarantees that the solid
insulation is of high enough quality and is
free from voids.
The same air duct also provides a flow ofcooling air, which enters at the bottom
and creates a self-sustaining flow thanks
to the chimney effect. This provides anautomatic regeneration of the insulating
air. Additional air ducts are located between the low-voltage (LV) coils and corelegs. The HV coils are also cooled on theirouter surface. For transformers with highpower ratings, additional air ducts can be
introduced into the LV and HV coils.
The windings can be made from an aluminum or copper conductor, depending
on customer preference. Incoming cables or open busbars are directly connected to the HV coils.
Globally, there is a significant trend toward using more dry transformers. The
market potential is large: While for LV ap-

plications dry transformer technology already strongly dominates, in MV applications oil-immersed units are still the mostprominent. For HV applications, besides
a few units using SF 6 gas insulation, oilimmersed types predominate as well.
HiDry72 transformers are the first series
air-insulated transformers for the 72.5 kV
voltage class.
HiDry characteristics and technology
HiDry 72 is available for power ratings up
to 63 MVA in either three-phase or single-phase solutions. It offers the samefunctionality as an oil-immersed powertransformer [2, 3] – including on-load voltage regulation using a dry-type on-load
tap changer (OLTC). The OLTC offers aregulation range of ±10 percent ➔ 2.

While a typicalpower transformer
contains several
thousand liters ofinflammable oil,fire class F1 dry
transformers are
self-extinguishing.

HiDry72 transformers use the same basetechnology as is used for MV applications and is available in ABB’s VCC andRESIBLOC dry transformer implementations. But the demands placed on transformers for subtransmission voltage levels are much higher than those placedon distribution transformers: The higher
voltage, higher rated power and increased range for voltage regulation

Safe and powerful­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7 1

3 The dielectric behavior of air is a critical factor in the transformer design.

Streamer
propagation

Streamerinception

Leaderpropagation

2.6 kV/mm

Voltage (a.u.)

0.1-0.2 kV/mm

0.5 kV/mmdDistance d between electrodes (a.u.)

3a The green curve represents the withstand voltage for a sphere-plane 		arrangement [1].

3b Evaluation of prospective discharge path by dielectric simulations

4 HiDry72 69 kV substation in Arena Fonte Nova, Salvador da Bahia, Brazil, with transformer and GIS installation
Access to arena
Transformer

Globally, there is asignificant trend
toward using more
dry transformers
and the potential
market is large.

PASSr­equire complex dielectric, thermal andmechanical problems to be solved.

for which HiDry72 is ideally suited due toits excellent fire-safety properties.

In particular, when going beyond the
36 kV voltage class a thorough understanding of gas breakdown physics isrequired in order to minimize dielectric
distances in air ➔ 3. Distances are minimized by introducing shielding rings in
the windings, shielding core parts, andapplying multiple-barrier concepts andbarrier arrangements. These techniques
influence the local electric field distribution and determine discharge paths.

HiDry 72 transformers use an epoxy resin
for the casting of the coils. Epoxy resin isa thermosetting polymer that – in contrast to thermoplastic polymers – does
not melt at elevated temperatures. The
resin is filled with a large amount of noncombustible silica – either small sandparticles or glass fiber – which, in case offire, takes up heat and reduces the combustion temperature. When subjected tohigh temperatures, the epoxy does not
spontaneously ignite but, rather, degrades and starts to degas and oxidize.
Once the external input of heat stops oran external fire extinguishes, this process ceases. Thus, the HiDry72 transformer never poses a flammability risk.

Fire safety – decisive for indoor andunderground substations
HV substations in city centers are mostly
located in special buildings, mainly because of transformer fire and explosion
risk. However, growing use of HV in inner-city settings and decreasing space
availability makes the integration of HV
substations into public or private buildings very desirable – a market situation­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7 2

ABB review 2|15

Seats

Flammability testing

Transformers of fire class F1 (which isbased on the IEC 60076-11:2004 standard) have restricted flammability and the5 HiDry72 69 kV/25 MVA transformer at the Arena Fonte Nova

5a With dry OLTC (on the left)

5b PASS M00 72.5 kV SF6 /air hybrid switchgear

ABB’s experienceof dry transformers
with internal failures is that they
do not explode oreject parts. Normally the coils
crack, local arcing
and carbonization
occurs, and somesmoke is generated. Depending on
the fault, the system protection will
thendisconnect
the transformer or the temperature sensor will detect a tripping temperature [4].

HiDry transformers offer
the same functionality as oilimmersed power transformers– including on-load voltage
regulation using a dry-type
OLTC.
72

emission of toxic substances and opaquesmokes is minimized. The F1 fire behavior
test is performed with one complete
phase of a transformer – comprising HVand LV coils, the core leg and insulation
components. A container filled with ethyl
alcohol is placed below the coil and thealcohol is ignited. An electrical heating
panel, representing an additional external
heat source, is placed along one side of
the HV coil, irradiating it with 24 kW. The
test is performed in a standardized test
chamber and the temperature and opticaltransmission properties of the exhaustgas are measured.
It is very important that the exhaust gases are not of poisonous or of a highly
corrosive nature since they can flow into
other parts of the building or be distributed via the ventilation system and may
affect a large number of people. Hightransparency of the smoke allows people
to orient themselves and find emergency
exits.

Arena Fonte Nova substation, Brazil
The 69 kV substation installation in the
Arena Fonte Nova stadium has a redundant configuration of two transformers
and two sets of HV switchgear ➔ 4. The
transformers are placed below the access area of the stadium, very close to
the grandstand. Open busbars fixed tothe ceiling of the electric room connect
switchgear and transformers. The substation was put into operation in spring
2013, well in time for hosting 2013 FIFA
Confederations Cup games.
The 25 MVA transformers connect on thesecondary side to the MV switchgear ➔ 5.
They have a secondary voltage thatis switchable between 11.95 kV and
13.8 kV. The transformer coils are madewith VCC technology, which provides robust windings (E2 environmental class)and good protection from environmental
Safe and powerful­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7 3

6 HiDry72 31.5 MVA / 66 kV dry power transformer at CESI test lab forshort-circuit testing

pollution and humidity. The transformer
is cooled by natural convection. It is tested
for a lightning impulse voltage of 350 kV.
The dry-type OLTC is installed in front of
the transformer, with each phase having
its own unit. The OLTC uses vacuum interrupters for switching. It is configured
to provide a regulation range of +4/-12
percent in 1.25 percent steps. Bothtransformer and OLTC are fenced off inorder to avoid unintentional personnel
contact, but no enclosure is required.
Seville inner-city substation, Spain
There are now many HiDry72 transformers installed around the world. In Seville,
Spain, for example, Endesa, the largest
electrical utility in the country, decided
to replace the existing oil-filled powertransformers in two substations with
HiDry72 transformers in order to eliminate
any related risk for the neighborhood.
Each substation has two transformers.
One of the 31.5 MVA, 66/22 kV, OLTC(±8 x 1.25 percent) transformers was successfully short-circuit tested at the CESI
independent testing facility in Italy,
against the relevant requirements of
IEC 60076-5 ➔ 6. The OLTC was mounted on the transformer. This was the largest power rating of a dry transformer
ever tested at CESI.
Similarly, the utility in Ulricehamn, Sweden needed to replace an outdoor oilimmersed transformer in a forest. The
utility decided to install a 45/11 kV,
16 MVA HiDry transformer and OLTC,
thus reducing the environmental risk to­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­7 4

ABB review 2|15

7 16 MVA / 45 kV dry transformer with OLTC and enclosure for
installation in an outdoor substation in Sweden

zero ➔ 7. The RESIBLOC coils are qualified for temperatures down to -60°C.
Future substations
Combining gas-insulated switchgear
with HiDry72 transformers allows very
compact substations to be constructed
and easily integrated into any building.
HiDry 72 transformers can deliver higher
voltages and more power to urban areas
without the need to build additional substations. The very positive experienceachieved so far with the 72.5 kV dry
power transformer suggests that theportfolio of dry transformers should be
extended to the next-higher voltage
class.

Martin Carlen
ABB Power Products, Transformers
Zurich, Switzerland
martin.carlen@ch.abb.com
Mariano Berrogain
ABB Power Products, Transformers
Zaragoza, Spainmariano.berrogain@es.abb.com

References[1] M. Carlen et al., “Transformer innovation:
Dry-type transformers for the 72.5 kV voltage
class – safe and ecological,” Advanced
Research Workshop on Transformers, Santiago
de Compostela, Spain, 2010, pp. 8–13.
[2] M. Carlen and M. Berrogain, “Dry-typetransformers for the subtransmission voltage
level,” presented at the EEA 2014 Conference,
Auckland, New Zealand, 2014.
[3] A. Pedersen et al., “Streamer inception andpropagation models for designing air insulated
power devices,” IEEE Conference on ElectricalInsulation and Dielectric Phenomena, Virginia
Beach, VA, 2009.
[4] M. Carlen et al., “Dry-type subtransmission
transformer: Compact and safe indoor
substations,” paper A2-304, presented at the2014 CIGRE Session, Paris, 2014.

Editorial Board
Claes Rytoft
Chief Technology Officer
Group R&D and Technology
Ron Popper
Head of Corporate Responsibility
Christoph Sieder
Head of Corporate Communications
Ernst Scholtz
R&D Strategy Manager
Group R&D and Technology
Andreas Moglestue
Chief Editor, ABB Review
andreas.moglestue@ch.abb.com
Publisher
ABB Review is published by ABB Group R&D andTechnology.
ABB Technology Ltd.
ABB Review
Affolternstrasse 44
CH-8050 Zurich
Switzerland
abb.review@ch.abb.com
ABB Review is published four times a year
in English, French, German and Spanish.
ABB Review is free of charge to those with aninterest in ABB’s technology and objectives.
For a s­ ub­scription, please contact your nearest
ABB representative or subscribe online atwww.abb.com/abbreview
Partial reprints or reproductions are per­m itted
subject to full acknowledgement. ­C omplete reprints
require the publisher’s written consent.
Publisher and copyright ©2015
ABB Technology Ltd.
Zurich/Switzerland
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LayoutDAVILLA AG
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Disclaimer
The information contained herein reflects the viewsof the authors and is for informational purposes
only. Readers should not act upon the information
contained herein without seeking professional
advice. We make publications available with theunderstanding that the authors are not rendering
technical or other professional advice or opinions
on specific facts or matters and assume no ­liability whatsoever in connection with their use.
The companies of the ABB Group do not make any
warranty or guarantee, or promise, expressed or
implied, concerning the content or accuracy of theviews expressed herein.
ISSN: 1013-3119

Preview 3 |15

Aspects of productivity
ABB’s vision, “Power and productivity for a better world,” is proudly
displayed alongside the company logo on advertisements, products andpublications such as ABB Review. Following on from the present issue
with its strong focus on solar power, the upcoming edition will look at thecompany’s technology from a productivity perspective.
Topics covered will include the dual-armed Yumi robot, which is set to
expand not only the scope of robot applications, but also to redefine
the way humans and robots will interact in future.
Productivity is not just about what new products can do, but is also
about making sure the existing installed base is operating optimally.
ABB’s Asset Health CenterTM is one example of ABB supporting
customers in this respect.
Focusing on ABB’s R&D expertise, the upcoming issue will feature thefirst of a series of articles on research on oscillations, an often underestimated field that has repercussions for virtually all technical systems.

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