Solar PV Rooftop Training Entrepreneurship Development Grid Connected Inverters

1. Partnership To Advance Clean Energy-Deployment (PACE-D)
Technical Assistance Program
Presented by
USAID PACE-D TA Program
Apr-18
Solar PV Rooftop Training Program For Entrepreneurs
Session:
Grid Connected Inverter

2. Contents
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 ”

6. CLASSIFICATION OF GRID CONNECTED INVERTER

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

14. Inverter Efficiency – Effect of Input Power

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

20. GRID CONNECTED INVERTER SPECIFICATIONS & DATA SHEET

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
Anurag Mishra
Senior Clean Energy Specialist
USAID/India
Email: amishra@usaid.gov
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.