A HARDWARE GRID SIMULATOR TO TEST
GRID-CONNECTED INVERTER SYSTEMS
ARUN KARUPPASWAMY B
DR.VINOD JOHN
Power Electronics Group
Department of Electrical Engineering
Indian Institute of Science, Bangalore
June 11, 2010
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GRID SIMULATOR – AN INTRODUCTION
What?
Grid simulator is a high power inverter controlled to simulate the effects
(voltage sag, voltage swell, frequency variation and the like) generally
observed in a grid.
Why?
 To test grid connected systems developed in the lab – under actual grid
conditions
 Variable voltage sources do not help as they do not include the line
impedance
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A LITTLE MORE DETAIL
A Typical Grid Disturbance
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GRID SIMULATOR HARDWARE SETUP
FEC
Grid
Impedance
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DC Bus
From Grid
C
L
INVERTER
L
C
To Load
L
L
The system is controlled to
imitate the grid along with
its line impedance. Various
grid disturbances can be
emulated to test systems
that are connected to the
grid.
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EMULATION OF IMPEDANCES
Reference Voltage for Inverter:
v ref (t )  vgrid (t )  vdrop (t )
Resistance Drop:
vdrop (t )  R  i (t )
Inductance Drop:
di (t )
vdrop (t )  L 
dt
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EMULATION OF INDUCTANCE
Low Pass Filter Approach:
vdrop ( s)
i( s)

  Ls
s 
State Estimation Approach:
isensed
v
+-
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Controller
1
L
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
i
6
IMPLEMENTATION METHODOLOGY
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DSP RESULT – A THREE PHASE VOLTAGE SAG
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DSP RESULT – POINT OF WAVE EVENT
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DSP RESULT – EMULATION OF INDUCTANCE
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DSP RESULT – BANDWIDTH OF EMULATION
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CONCLUSION
1. The grid simulator is a useful and essential hardware that is required for projects on
grid-connected systems.
2. The grid simulator can be useful to study the impact of events such as sags and
swells, frequency variations and system faults on grid interactive converters such as
STATCOM.
3. Issues in the development of the grid simulator would be the emulation of
inductance and the hardware issues that might arise when testing the equipment
under test like over currents leading to tripping of the Grid Simulator.
4. In this paper, impedance emulation has been discussed. Resistive and inductive
impedances that characterizes the power system has been emulated in the DSP.
5. The same is in the process of being implemented using the 50kVA inverter that is
being constructed.
6. The study on the DSP controller indicates that it is feasible to implement such a
system.
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REFERENCES
1.
IEEE Standard 1547.1, “IEEE Standard Conformance Test Procedures for
Equipment Interconnecting Distributed Resources with Electric Power Systems”,
IEEE, 2005.
2.
Richard Zhang, Mark Cardinal, Paul Szczesny and Mark Dame, “A Grid
Simulator with Control of Single-Phase Power Converters in D-Q Rotating
Frame”, IEEE, 2002, pp 1431-1436
3.
National Renewable Energy Laboratory, Distributed Energy Resources Test
Facility, http://www.nrel.gov/eis/test_facility_vtour.html
4.
Gene F. Franklin, Michael L. Workman and David Powell, “Digital Control of
Dynamic Systems”, 3rd Ed., Addison-Wesley Longman Publishing Co., Inc.
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DISCUSSION
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