Single Phase to Ground Fault Current in Three Phase Inverter with Balanced & Unbalanced Load

1. Single Phase to Ground Fault
Current in Three Phase Inverter with
Balanced and Unbalanced Load
Presented By
Jaydeep Satyajit Sathe & Vi Binh Quang Le
ELE-791 Control of Distributed Generation
Syracuse University
April 19, 2017

2. Outline
Introduction
Technical Background of Inverters
Inverters Applications
Advantages and Disadvantages of Inverters
Inverter for Current Ground Fault
Simulation and Results
Conclusions and Future Research
References
Vi Binh Quang Le & Jaydeep Satyajit Sathe 24/19/2017

3. Introduction
Inverter is an electronic device, which
converts direct current (DC) input to
alternating current (AC) output and
also known as DC-AC converter.
Due to the problem of dependent on
nonrenewable fossil fuels, a demand
of a development of renewable
energy (clean power) is significant.
Thus, inverters are used as interface
between power generators (wind,
solar, hydro, etc.) and the distribution
grid to maintain the stability,
reliability, controllability, and
efficiency of the grid. [1]
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4. Technical Background of Inverter
Inverter technology was initially
found by Toshiba Corporation in
1980s, and the technology is still
applied widely in industries,
especially to the renewable
energy filed.
Basic structure of inverter
device consists of multiple
transistors as displayed in the
figure on the side.
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5. Technical Background of Inverter (Cont.)
Single Phase Inverter : this inverter
circuit consists of two transistors Q1
and Q2 and two diodes connected as
on the diagram. Q1 and Q2 are in
turn on and off to generate a voltage
Vo = Vs/2 cross the load. This is also
known as Half Bridge Inverter. [2]
Application: H-bridge inverter is used
to convert 12 Vdc into a 120 Vac
square wave using a transformer with
a 10:1 turns ratio [7]
Vi Binh Quang Le & Jaydeep Satyajit Sathe 54/19/2017

6. Technical Background of Inverter (Cont.)
Three phase inverter: it is used
for energy processing of PV and
wind power.
A three-phase inverter has three
legs, one for each phase. Each
inverter leg operates as a single-
phase inverter.
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7. Inverter Applications
Solar power
Fuel cell (FC) plants
Wind turbines and microturbines
Power-hydro
Variable-frequencies drives
Uninterruptible power supplies
Electronic ballasts and induction heater
Storage devices as local energy sources
Vi Binh Quang Le & Jaydeep Satyajit Sathe 74/19/2017

8. Advantages and Disadvantages of Inverters in
Solar Energy
String Inverters
Advantages
 Lower cost
 Easier to install and maintain
Disadvantages
 Problem if one panel fail, the
entire string fail
 Difficult to fix
 Occupy more space
Vi Binh Quang Le & Jaydeep Satyajit Sathe 84/19/2017

9. Advantages and Disadvantages of Inverters in
Solar Energy (Cont.)
Micro Inverter
Advantages
 All panels are independent, failure
of one panel will not impact other
 Easy to fix and maintain
 Occupy less space
Disadvantages
 High cost
 Difficult to install and maintain
Vi Binh Quang Le & Jaydeep Satyajit Sathe 94/19/2017

10. Inverters for Ground Fault Current in
Microgrid
What is the inverters for ground fault current in microgrid?
 Ground fault current in microgrid is technically abnormal current. This could
be one or all the currents in the single or three phase of the inverter in the
distributed grid (also known as a short circuit).
 In order to protect the components devices in the grid systems, inverters are
required to limit their fault current capability. This is accomplished through
reduction in the internal voltage during faults. [6]
Possibility methods of controlling the ground fault current
 Fault behavior of an inverter is determined by its control, which in turn is
based on the inverter topology (three phase three wire, three phase four
wire, single phase) and topology of the network to which the inverter is
connected as balanced or unbalanced load).
Vi Binh Quang Le & Jaydeep Satyajit Sathe 104/19/2017

11. Inverters for Ground Fault Current in
Microgrid (Cont.)
Techniques used to control in single phase and three phase inverters
can be broadly divided into the following three categories [6]:
• Control in synchronously rotating dq0 reference frame
• Control in stationary frame
• Control in natural reference frame
Control in rotating reference frame is the most popular approach where
measured output voltages and currents are transformed into their equivalent
by rotating frame dq0 of reference [6]
 In this presentation, observing the effects on the inverter output
current due to a single phase to ground fault with balanced and
unbalanced loads will be analyzed
Vi Binh Quang Le & Jaydeep Satyajit Sathe 114/19/2017

12. Inverters for Ground Fault Current in
Microgrid (Cont.)
A single phase ground to fault in the three phase inverter with
balanced load
• In this stage, the inverter is implement with parameters described in the
gain.m file (which was attached to the research report)
A single phase ground to fault in the three phase inverter with
unbalanced load. In this case, the parameters used in the simulation
have been chosen as follows:
• Current limit is set to 110% of the inverter peak current limit
• Three unbalanced loads:
o Phase A : 50 kVA
o Phase B : 20 kVA
o Phase C : 5 kVA
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13. Simulations & Results
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14. Our results have 3 partsPart 1
We observe the effects of a single phase fault in phase A (short
circuited to ground) for two cases – with balanced load and with
unbalanced load. Here we set inverter current limit to be constant at
300%, and Rsc (short-circuit resistance) to be constant at 1%.
Part 2
We change the inverter current limit to 110%, 300% and 562% and
observe the effects of the single phase fault on the inverter current. We
do this for balanced and unbalanced loads. We set Rsc to be constant
at 1%.
Part 3
We change the values of Rsc to 1%, 7.5% and 15% and observe its
effects on the inverter currents and voltages. We do this for balanced
load, and we set current limit to be constant at 300%.
Vi Binh Quang Le & Jaydeep Satyajit Sathe 144/19/2017

15. Part 1(A) – Balanced load, Phase A fault
Iinv: Phase A, B, C load = 80 KVA
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16. Vinv:
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17. Iload:
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18. Vload:
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19. Part 1(B) – Unbalanced load, Phase A Fault
Phase A load: 50 KVA, Phase B load = 20 KVA, Phase C load = 5 KVA
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 194/19/2017

20. Vinv
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21. Iload:
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22. Vload:
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23. Part 1 Conclusion
The waveforms observed are as expected, and the main difference
between Part 1(A) and Part 1(B) is the balanced and unbalanced loads.
In both cases, when phase A is shorted with the ground:
The I inv current for phases B and C increases and reaches the inverter
current limit, but that for phase A remains the same.
The V inv voltage for phase C decreases, but that for phases A and C
remains almost the same.
The I load for phase A increases, but that for phases B and C remains the
same.
 The V load voltage for phase A decreases significantly, but that for phases
B and C increases slightly.
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24. Part 2 – Changing Inverter Current Limits
For I limit = 110% = 293.2722 A, Balanced load
Iinv:
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25. I limit = 110% = 293.2722 A, Unbalanced load
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 254/19/2017

26. I limit = 300% = 799.8334 A, Balanced load
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 264/19/2017

27. I limit = 300% = 799.8334 A, Unbalanced load
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 274/19/2017

28. I limit = 562% = 1500 A, Balanced load
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 284/19/2017

29. I limit = 562% = 1500 A, Unbalanced load
Iinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 294/19/2017

30. Part 2 Conclusion
From Part 2, we observe that if phase A is shorted with the ground:
The Iinv for phase A remains almost the same (except for the effect of
harmonics), but the Iinv for phases B and C reach the inverter current
limit.
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31. Part 3 – Changing Rsc valuesRsc = 1% = 0.01
V inv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 314/19/2017

32. I load
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33. V load:
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34. Rsc = 7.5% = 0.075
V inv:
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35. I load:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 354/19/2017

36. V load:
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37. Rsc = 15% = 0.15
Vinv:
Vi Binh Quang Le & Jaydeep Satyajit Sathe 374/19/2017

38. I load:
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39. V load:
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40. Part 3 Conclusion
From Part 3, we observe that when Rsc is increased:
The V inv voltage for phase C increases, but that for phases A and C
remains the same.
The I load for phase A decreases, but that for phases B and C remains
the same.
 The V load voltage for phase A increases, but that for phases B and C
remains the same.
Vi Binh Quang Le & Jaydeep Satyajit Sathe 404/19/2017

41. Future Work
 Based on the simulation results, appropriate fault models and
protection systems for such microgrid will be developed and tested.
Vi Binh Quang Le & Jaydeep Satyajit Sathe 414/19/2017

42. References
[1] Ali Keyhani, Mohammad N. Marwali, Min Dai, “ Integration of
Green and Renewable Energy in Electric Power Systems,” 2010 by
John Wiley & Sons, Inc. pg 1-4
[2] Manoj Kumar Swami, “ Inverter,” www.slideshare.net
[3] Eric Glover, Studen Member, IEEE, Chung-Ching Chang, Student
Member, IEEE, Dimitry Gorinevsky*, Fellow, IEEE, and Sanjay Lall,
Senior Member, IEEE, “Frequency Stability for Distribued
Generation Connected through Grid-Tie Inverter,” IEEE International
Conference on Power System Technology (POWERCON), 2012
[4] P. Bhanu Teja, “Advancements in Inverter Technology,” National
Institute of Technology Calicut, www.slideshare.net
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43. References (Cont.)
[5] Dr. Tomislav Bujanovic, “ELE 791 Control of Distributed
Generation,” Modeling of Power Converter, Department of
Electrical Engineering and Computer Science, Syracuse University
[6] S.P. Plkharel, Satish Ranade, “Modeling and Simulation of Three
Phase Inverter for Fault Study of Microgrids,” Conference Paper,
September 2012
[7] Jim Dunlop Solar, “Inverter,” Definitions and Terminology∙Types and
Applications ∙ Functions and Features ∙ Selection and Sizing
∙Monitoring and Communications, 2012
[8] “History of Inverter Technology,” Mitsubishi, Heavy Industries, LTD.
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