Leading technologies for renewables energies applications

solarContents

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Solar energy
Solar power infrastructure
LEM solution for string inverters
LEM solution for centralized inverters

Leading the world inelectrical measurement
A leading company in electricalmeasurement, LEM engineers
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our customers’ systems areoptimized, reliable and safe.
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to a sustainable future.

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SolarSolar energy
Convert solar energy directly into electricity, is one of theproducts of modern science and technology progress. At
the same time, as a kind of favorite clean and green energy,
it will significantly reduce the carbon emissions producedby traditional energy consumption which will have anegative impact on the natural environment. By 2050, thegenerated power by solar will occupy 25% in the global
power system to make resisting the most serious
catastrophic warming be possible. LEM actively dedicatesto the construction of solar generated power stations, bysupplying very high technology sensors and solutions tomake the solar inverter and related appliances working
more efficient, reliable, more affordable, and smarter.
Technological innovation
Technological innovation will accelerate the arrival of the grid-parity andreduce the overall cost of PV system. LEM has already identified thechallenge on cost pressure and prepares cost-effective solutions ready tohelp customers to deal with in all kinds of application.
Rapid development of residential solar market will make everyone use clean
energy, and benefit from it. LEM has already accelerated its productdevelopment to help inverter suppliers succeeded in the intense market
competition.

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Solar Power Infrastructure
Solar Panel

DC to AC
Conversion

DC to DC
Conversion

AC Current
Measurment

DC LinkLN

Single Phase
AC Grid

Analog Device DSP

String vs Centralized PV systems
Two major types of PV system are dominant on the market, String inverter forsmall and medium power and Centralized inverter for big power
String inverter
String inverter can be directly connected to PV string(s) and used for indoor
and outdoor hanging installation, is able to deliver a power to a single-phaseor three-phase grid between a few kilowatts and hundreds of kilowatts
String inverters have the following features:• High protection grade design, more for IP65
• Combiner box is NOT needed• Wide input dc voltage range• MPPT control is more sophisticated• High efficiency• Flexible configuration to adapt various application scenarios
Centralized inverter
Centralized inverter has a direct current (dc) from photovoltaic combiner box
and converts into alternative current (ac) with single power stage. Therefore,
the centralized inverter power is relatively large, typically no less than
500kW for single unit, can also be applied to the application for large groundpower station and large commercial roof
Centralized inverters have the following features:• Facilitate maintenance and energy management• Power density is high while the cost is low• High-level security for power station• Capable of power factor adjustment and low voltage ride through function
5Solar

LEM solution for string inverters

Typical three phase string inverter structure
DC Switch+
DC1

MPPT-

L1EMI Filter+
DC12-LC Filter

AC Relay

EMI Filter

L2L3MPPTPE

DC/DCString Current
Measurement

DC LINK

DC/AC

Possibility to install sensor

String inverter normally measures the current infour places to secure the normal operation:
Four places:• PV array current measurement• MPPT (Maximum Power Point Tracking) circuit current measurement• Inverter output alternative current measurement• Inverter residual current measurement

PV array current measurement is aimed to monitor
each array current status during its operation tocheck whether PV array is working normally or notFeatures for PV array current measurement:• Multi-channels current to be measured, typically string inverters has
2,4,8,16 or 24-channels• High precise current sensor is not needed• Current range for each array typically is less than 30Adc
Inverter residual current measurement

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To use MPPT control to ensure the systemrunning at maximum power output condition
Measurable current range for DC/DC boost circuit(MPPT circuit) is 10-30A RMS for each MPPT unit,
in which will be best choice with open loop
current sensor
Sensors specifications
Sensor

HLSR

GOHMSR

Technology

Hall O/LHall O/LHall O/L

ASIC Inside

Yes, HG2Yes, HG2 Orion

Yes, HG2 Orion

Integrated Primary

Yes

Yes

Yes

Footprint

DIP

SMD, SOIC 8&SOIC 16

SMD, Compatible with SOIC 16

1500Vdc PV Application

Yes

NoYes

Withstand surge current capability

10kA 8/20us

10kA,8/20us

20kA.8/20us

OCD function

N/A

Yes (SOIC 16 only)

Yes

Measurable range+/-300Apk+/-75Apk+/- 75Apk

The core control in solar inverter is to generate apure sinewave current to flow into the grid, whichis regards as high-quality energy feed to the grid.
Therefore, the current measurement solution inAC side shall be capable of these features:Features:• High precise measurement: less than 1%• Fast response time: less than 1us• Low offset voltage and current• Good performance on the temperature drift

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SolarLZSR family
Closed Loop Hall technology enlarges
measuring range on PCB mounting with +5 V
single supplyFeatures• 3 proposed ranges 100 – 150 – 200A Nominal• +5 V single supply• PCB mounting• Various integrated options: Reference, Aperture and/or integrated
primary conductor, OCD output• Measuring peak current up to 3 times the nominal value• Very low offset drift up to 3ppm/K of VREF
• Offset drift 7 times better than previous generation of C/L Hall effectcurrent transducers working with traditional Hall effect chip
• Internal reference voltage provided on a dedicated pin• Total error at +85°C: 1.4 %• High performance with a Hall ASIC for closed loop working principle

Sensors specifications
Product Family

LH

CASR/CKSRLESR/LKSR

LZSRTechnology

Hall C/L

FluxGate

Hall C/LHall C/LPower supply±12…±15V+5V+5V+5V

Output Type

Current source

Voltage source

Voltage source

Voltage source

Accuracy@50A 25C

0.2%

0.8%

0.5%

0.6%

Response time

0.2us@90% IPN

0.3us@90% IPN

0.3us@90% IPN

2.2us@80% IPN

Offset voltage/current@50A±0.06 mA

±0.7 mV±0.725 mV

N/A

Offset voltage/current@100A

N/A

N/A

N/A

±0.75 mV

TCG

±30ppm/K±40ppm/K±40ppm/K±45ppm/K

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LEM leakage current measurement
for your safety
In fact, residual current is called common mode current caused by parasitic capacitor between
the PV panel(s) and power earth, while there has a loop existing between the parasitic capacitor
and grid through the PV system during the inverter operates, the common mode voltage comingfrom high switching of IGBTs will occur a common mode current on the parasitic capacitor andwill flow into the grid.
If there is no electrical isolation (including high frequency isolation and low frequencytransformer isolation), the common mode current will become large due to the low
resistance in the system loop, which will have a safety risk and thus impact the wholesystem
According to the norms: if the continuous residual current exceeds the following limit,
the inverter should stop running and disconnect from the grid within 300ms duration.
• For less than or equal 30kVA inverter, the maximum allowed residual current limit is
300mArms• For 30kVA above inverter, the maximum allowed residual current limit is 10mA/kVA• Should use a current sensor which complies with Type B standard to guarantee
residual current measurement.
The LDSR is a small residual current sensor, allowing small inverter manufacturers tofulfill IEC62109.

DCPV
parasiticcapacitor

DCDCAC

icom 1
icom 2

icom

icom~LDSR 0.3-TP/SP1 & LDSR 0.3-NP Features:• IPN = 300 mA RMS• 2 or 4 primary bars options• 5% accuracy• 20 turns test winding• 35 A max on each primary• 2 kHz bandwidth• Small footprint (70% smaller than CTSR)• Optimized for EN 62109

LDSR inside AC inverters
1-ph inverter~9Solar

LEM solution for centralized
inverters
Comparing to string inverter, centralized
inverter measures current both in DC and AC
side more easily, a large range of current sensor
can solve all the power measurement problems,
become safer and more reliable.

DC Switch+DCL1-

DC EMI
FilterLC Filter

L2L3+DCAC EMI
Filter-DC/AC

10Solar

LF 10 Family

Closed Loop with Hall elements integrated into the latest
designed LEM ASIC (Cygnus) providing useful additional
functions and patented techniques

Features:• Five series at 200 - 300 - 500 - 1000 – 2000 A nominal• Compact sizes/variety of mounting topologies (flat or vertical)• Fully compatible & same technology (Closed Loop Hall) as previous
generation LF x05 series• Higher immunity (510-1010)• Higher accuracy & response• -40 to +85°C operation

Sensors specifications
Product Family

LF210/310/510

LF1010

LF2010TechnologyC/L Hall cell

C/L Hall cell

C/L Hall cell

Current range

100-500A

1000A

2000A

Insulation

3.5kV

6kV

10kV

Global error @25°C

0.2%

0.2%

0.2%

Overall accuracy (over T°C)

0.2%

0.4%

0.3%

Linearity error

0.05%

0.15%

0.1%

Bandwidth

100 kHz200 kHz150 kHz

Delay time (us)

0.5

0.5

0.5

Electrical Offset (mA)

0.15

0.2

0.2

Consumption (mA)

35 + IS49 + IS85 + IS

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