[Background Reasons Why Hybrid Power Generation is Required]As the electrification rate is low in colored areas in the global map in Figure 1, where the population
is dispersed across a vast tract of land, the conventional electrification by national grid is difficult in
those areas.

Figure 1. Areas where electrification is difficult

In those areas, people live without electricity or on a very fragile power infrastructure with solar
lanterns and uncontrolled solar power generation, enabling them no more than to charge cell phones.

Against such a backdrop, governments of countries concerned have made attempts for electrificationby using small diesel power generators, which is the easiest way, out of necessity, but it has become
difficult to maintain them due to inability to finance high fuel and maintenance costs. Those
governments are calling for technological and financial assistance for hybrid power generation using
renewable energy from Japan and other countries with advanced energy infrastructure.
According to a document by JICA, 1.4 billion people live in those areas where electrification isdifficult, and those people want energy infrastructure that suits actual local situations, such as hybrid
power generation combining natural energy.

1[Issues with Technological Assistance in the Area of Energy]
Electrification of areas where national gridcannot be used including remote islands andareas starts with an easy microgrid whereby
small diesel power generators are directly
connected to the electricity grid, as shown by
the black line in Figure 2.
This method, however, incurs high fuel andmaintenance costs, making it difficult tomaintain the system as resulting highelectricity prices ranging from 50 to 100
yen/kWh, inconceivable in Japan, hinder
economic activities.

Figure 2. Conventional hybridization by a microgrid

If renewable energy is introduced, partly because of the needs of the times, under assistance fromJapan and other countries, power from solar panel generation and wind power generation will beconverted by power line conditioners (PLC) and transmitted to the grid in the form of alternating
current, as shown by the red line in Figure 2. This is the same method normally used in introducing
renewable energy in mainland Japan.
As power from renewable energy has recently been refused to be received even by the grid of a large
electric power company in mainland Japan, a small grid powered by a single diesel generator in aremote island is easily overflown, forcing the disconnection of renewable power sources.

In response to this, numerous demonstration tests have been conducted in Japanese and Oceanianislands for shaving the peak of renewable energy power generation by adding a very expensive
inverter with EMS and a battery, as shown by the blue line in Figure 2. A power line conditioner,
which is a generation device ancillary to the main power supply device such as a diesel generator,
cannot be the main power supply device, however. If the main power supply device halts, a powerline conditioner will also halt.

Since, even if there is sufficient natural energy providing surplus power, under the conventional
hybridization of a microgrid shown in Figure 2, a diesel power generator has to be kept operating to
an extent that prevents low load operation, it is impossible to operate the microgrid 100% by naturalenergy.

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[Mechanism of an Inverter]
While an inverter is normally used as a device to drive a motor, it is used as a power supply device
in Tamaden Industry’s hybrid power generation system.
How an inverter operates is illustrated by using the schematic diagram of a three phase inverter shownin Figure 3.

Three-phase inverter
DCL P

Alternating current
Direct current
Pseude alternathing current

R
Three-phase AC input Sfilter
OFLCTM

Three-phase motor, etc.

Nconverter

inverter

DC intermediate

DC/AC Converter

AC/DC Converter

Figure 3. Schematic Diagram of a Three Phase Inverter
Converter circuit: A converter circuit rectifies three phase alternating current into direct current.
DC intermediate circuit: The DC part of an inverter is called DC intermediate circuit.
A DC intermediate circuit can be connected in parallel with that of another inverter
just like a battery.
This enables the construction of a variety of power conversion devices.
Inverter circuit: An inverter circuit generates pseudo three phase alternating current by the PWM
method using a three-phase H-bridge.
Switches are turned on and off in synchrony with the carrier frequency to modulate
the pulse width of the output from the H-bridge to generate an AC waveform inaccordance with effective output values.
Although the wave form of an inverter output is a PWM waveform (square waves
with different pulse widths), an inverter output can drive a motor.
The addition of an output filter circuit to an inverter enables it to generate a cleansine wave, and the inverter can then be used as a power supply with frequency andvoltage adjustment.
PWM: Pulse Width Modulation
It is a modulation method that produces a variable output by varying the pulse width (duty ratio).
An inverter controls the pulse width togenerate a sine wave in accordance witheffective values of its output.
An output is controlled by varying the pulse width (duty ratio).
Figure 4. PWM Control

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[Tamaden Industry’s Hybrid Power Generation]
The greatest challenge for hybrid power generation is to aim for zero fossil fuel consumption byoptimizing the energy mix composed of multiple energy sources including solar power generation,wind power generation, and diesel power generators and by improving the proportion of natural energy.
It derives stable powerfrom multiple energy sources

Hybrid power generation control unit
solar panel

Power generation

Water intake

Alternating current
Direct current
Pseude alternathing current

AC / DC
Converter

DC / AC
Converter
inverterG
1
Turbine generator

battery
Collective
交流/直流

DC Linkbus voltage

controlapparatus
変換部

AC / DC
Converter

AC / DC
Converter

Connection ①Wind-power

DC / AC
Converter
inverter

Diesel generator

HereEnergygatherGDC / ACConverter
invertergeneration

2Customer

filterAC output

3

Diesel generator
Connection ① and connection ② are also
possible

Connection ②Electricity demand

Diesel generator

Figure 5. Schematic Diagram of Hybrid Power Generation Demonstration Unit
The schematic diagram of the hybrid power generation demonstration unit constructed by Tamaden
Industry in Kojimayuga, Kurashiki-shi, Okayama prefecture, is shown in Figure 5.
It is an standalone power plant with the rated output of 75 kW which uses inverters as its main
power supply devices and to which solar panels, wind turbine equivalents, batteries, diesel power
generators, etc. are connected.
This hybrid power generation system using inverters can completely halt diesel power generators if
there is a sufficient amount of power generated from renewable energy sources, and one of its
advantages is its ability to reduce the fuel and maintenance costs of diesel engines significantly byoperating 100% on renewable energy sources.
In addition, in connecting a diesel power generator, you can choose the connection method (1) via
inverters or the connection method (2) for synchronous parallel operation.
Elements in green in the schematic diagram of the demonstration unit represent the DC intermediate
circuit of an inverter.
Since the DC intermediate circuit is a DC circuit, an energy mix of multiple energy sources can beeasily created by connecting multiple inverters, solar panels, and batteries in parallel just as dry
batteries can be connected in parallel.

4Since renewable energy sources from which to compose an energy mix can be chosen at will, a simple
hybrid power generation system created by connecting solar panels to an existing diesel power generator,
as shown in Figure 6, is possible depending on the conditions of the area in which the system is installed.
solar panel

Direct current
Alternating current
Pseude alternathing current

Collective
交流/直流Electricity demandbattery
DC Linkbus voltage

controlapparatus
変換部

AC/DC

DC/AC

Converter

Converter

CustomerfilterAC output

inverterConnection ②

Existing diesel power generator

Figure 6 Example of a hybrid power generation system for a remote island

Besides the demonstration unit in Kojimayuga, Kurashiki-shi, our overseas hybrid power generation
business is also underway (in Maldives) by utilizing the subsidy from the Ministry of Environment.
While solar power generation is in saturation in Japan, in areas where electrification is difficult
described in the beginning, there is limitless demand for power infrastructure suiting real life such as
a combination of solar panels and a diesel power generator illustrated in Figure 6.
Furthermore, even in Japan, hybrid power generation combining natural energy sources can contributeto energy saving and decarbonization in environments with a special power supply such as
construction ships and construction sites in mountains where power is supplied by in-house powergeneration.
We have been promoting our hybrid power generation system based on the idea that it can be a pillarof power infrastructure in areas where electrification by national grid is difficult, including sparsely
populated areas and remote islands, and create a new trend in solar power generation.

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