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Session 5 - Grid Connected Inverter.pptx
1. The World Bank – SBI Grid Connected Rooftop Solar PV
TA Program
Session V : Grid Connected Inverter
Presented by
The World Bank SBI GRPV TA Program
1
2. 2
Content
• Function of the inverter in Solar PV Rooftop systems
• Types of inverter – standalone, grid connected and multi-mode
• Classification of grid connected inverter
• Inverter efficiency
• Selection of grid connected inverter
3. Function of the Inverter in Solar PV Rooftop Systems
Convert DC to AC (Energy transformation)
Synchronises voltage to the grid
Finding Maximum Power Point (MPPT)
Monitoring Centre for Solar PV Rooftop system
Provide protection functions (AC and DC side protections)
Be safe, efficient and reliable in operation
Provide power quality i.e. no bad effects caused by inverter operation (Power
regulation / Reactive power mode etc.)
4. Standalone Inverter
Stand-alone inverters are typically
manufactured to operate from a
specific nominal battery voltage e.g.
12V, 24V, 48V or 120V DC
The system controller includes voltage
regulator and MPPT
5. Grid Connected Inverter
A grid-connected inverter is directly connected to the PV array
If the AC grid is not present, the inverter will simply not function
IEC 62116 -: “Anti Islanding function ”
7. Classification of Grid Connected Inverter
Grid Connected
Inverter
Based on use of
Transformer
Isolated
Non Isolated
Based on interface
with SPVRT Array
Micro Inverter
String Inverter
Multi String Inverter
Central Inverter
8. Classification of Grid Connected Inverter – Isolated v/s Non Isolated
Where there is at
least simple
separation
between the input
and output circuits
(e.g. by means of a
transformer with
separate windings)
it is categorized as
an isolated inverter
(IEC 62548)
Isolated
Inverter
Also known as
Transformer less
inverter
Inverter that does
not have at least
simple separation
between the input
and output circuits,
is categorized as
non-isolated
inverter
(IEC 62548)
Non Isolated
Inverter
9. Micro Inverter
Each module connected one micro
inverter
Connected in parallel
Power: 100W – 350W
Input: 20-40V DC
Output: 230V AC
Single phase
Higher cost in comparison to string
inverter
Must comply with IEC 62109-2
Micro Inverters
Grid
10. String Inverter
Single or multiple strings connected to
a single MPPT inverter
Power: 1kW – 30kW
Input: 150-350V DC
Output: 230V-415V AC
1- phase or 3-phase
Higher cost in comparison to central
inverter
Must comply with IEC 62109-2
Single & multiple MPPT inverter
11. Central Inverter
Multiple strings are connected to
normally single MPPTs
Power: 30kW – 2MW
Input: 300-800V DC
Output: 400V AC
3-phase
Lower per W cost in comparison to
string inverter
Must comply with IEC 62109-2
Central Inverter
Grid
12. Market Segmentation –
Grid Tie Inverter (Capacity & Applications)
Grid Tie Inverter
(Capacity &
Applictions)
Central Inverters
Conventional & proven technology
Solution for large PV projects
Focus – centralized bulk power generation under central & state initiatives
E.g. Multi Mega Watt Projects
String Inverters
Well established technology
Solution for medium ground mounted and rooftop projects
Focus – captive consumption & net metering
E.g. Private Residential / Commercial / SMEs
Micro Inverters
Newly developed technology
Solution for small & medium sized PV plants
Focus – captive consumption at small scale
E.g. Small systems, Rooftop Commercial Systems etc.
13. Power Quality of Grid Connected Inverter
Central Electrical Authority of India (Technical Standards for Connectivity to the Grid)
Regulators, 2007 specifies that the generating sources located near the load centers
must have a power factor between 0.95 leading and 0.85 lagging
For sources located far from the load centers, the power factor should be
maintained between 0.95 leading and 0.90 lagging
However many inverters have a power factor of 1
Central Electrical Authority of India (Technical Standards for Connectivity of the
Distributed Generation Resources) Draft Regulations, 2012 specifies that the total
harmonic distortion must not exceed 5% as specified in IEEE 519
15. Inverter Efficiency – Effect of DC Voltage &
Temperature
Lower DC string voltage leads to reduction in efficiency
Higher working temperatures reduces overall performance
16. Inverter Efficiency – Various Scenarios
IEC 61683 – Photovoltaic Systems – Power Conditioners – Procedure for measuring
efficiency
Maximum efficiency @ rated output
Weighted average value of Efficiency
Efficiency MPPT at all times
Part loading – Efficiency @ rated output
17. Selection of Grid Connected Inverter
Supply & Logistics
Balance of
Systems (BoS)
Requirements
Ease in Design,
Installation,
Performance,
Supervision &
Control
System Reliability
& Other Technical
Aspects
18. Why is Assessment of PV Inverters most Essential
Inverters are the most complex
Crucial for PV plant performance
Accounts to approximately 8-14% of the overall installation cost
Other cost associated with technology selection
Selection significantly affects RoI
Installation requirements
Supply and logistics - Special infrastructural requirements
Safety of personnel and product
PV plant configuration
Site conditions are not same
Balance of System (BoS) composition changes with technology
Control & monitoring philosophy depends on technology limitations
19. Why is Assessment of PV Inverters most Essential
Design flexibilities
Ease in design thus installation
Performance monitoring & supervision
System reliability – Depends on the Product Quality
Life of the product – Project life of 25 years (?)
Maintenance requirement - Skill labor requirement
Failure rate and replacement time – What is the warranty?
Spare part requirements
Actual cost of maintenance?
Overall impact on energy generation and RoI
21. INPUT DATA Fronius Symo 20.0-3-M
Max. input current
(Idc max1 / Idc max2)
33.0 A / 27.0 A
Max. usable input current total
(Idc max1 + Idc max2)
51.0 A
Max.array short circuit current (MPP1 / MPP2) 49.5 A / 40.5 A
Min. input voltage (Udc min) 200 V
Feed-in start voltage (Udc start) 200 V
Nominal input voltage (Udc,r) 600 V
Max. input voltage
(Udc max)
1,000 V
MPP voltage range
(Umpp min - Umpp max)
420 - 800 V
Number of MPP trackers 2
Number of DC connections 3 + 3
Max. PV generator output (Pdc max) 30.0 kWpeak
OUTPUT DATA
AC nominal output (Pac,r) 20,000 W
Max. output power 20,000 VA
AC output current (Iac nom) 28.9 A
Grid connection (voltage range) 3~NPE 400 V / 230 V or 3~NPE 380 V / 220 V (+20 % / -30 %)
Frequency (frequency range) 50 Hz / 60 Hz (45 - 65 Hz)
Total harmonic distortion 1.3 %
Power factor (cos φac,r) 0 - 1 ind. / cap.
22. GENERAL DATA
Dimensions
(height x width x depth)
725 x 510 x 225 mm
Weight 43.4 kg
Degree of protection IP 66
Protection class 1
Overvoltage category (DC / AC)1) 1 + 2 / 3
Night time consumption < 1 W
Inverter design Transformerless
Cooling Regulated air cooling
Installation Indoor and outdoor installation
Ambient temperature range -40°C to +60°C
Permitted humidity 0 % to 100 %
Max. altitude 2,000 m / 3,400 m (unrestricted / restricted voltage range)
DC connection technology 6x DC+ and 6x DC- screw terminals 2.5 mm² - 16 mm²
AC connection technology 5-pin AC screw terminals 2.5 mm² - 16 mm²
* Exclusive technical details
23. 23
Dr Amit Jain
Renewable Energy Specialist
Email: amitjain@worldbank.org
Acknowledgment and Disclaimer:
This training material is made possible by the support of the American
People through the United States Agency for International Development
(USAID). The contents of this material are the sole responsibility of Nexant
Inc. and do not necessarily reflect the views of USAID or the United States
Government. This material was prepared under Contract Number AID-386-
C-12-00001. The images shown here are taken from the Internet for
education purpose only. Further the training material has been modified
and updated as necessary by The World Bank – SBI GRPV TA Program