10th Carnegie Mellon Conference on
The Electricity Industry
Testbed for Mitigation of Power Fluctuation on
Micro-Grid
Presented by Xin Zhao
UC San Diego
April 1, 2015
Acknowledgements
The project was sponsored by the California Energy Commission.
UC San Diego Team
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Xin Zhao
Raymond de Callafon
Maurice van de Ven
William Torre
Chuck Wells
System Identification and Control Laboratory, UC San Diego
System Identification and Control Laboratory, UC San Diego
Eindhoven University of Technology
Center for Energy Research, UC San Diego
Center for Excellence, OSIsoft
OCC Team
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Greg Smedley
Tong Chen
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One-Cycle Control Inc.
One-Cycle Control Inc.
Outline
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Introduction
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Testbed for mitigation of power fluctuation
– Overview
– “Portable” cabinet
– Controller
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Preliminary tests on the testbed
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Future work
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Introduction
Introduction
Motivation for mitigation of power fluctuation
• Power fluctuation occurs
intermittently on micro-grid.
• Conventional generation tends to
stabilize and maintain synchronous
operation of the system by the inertia
in the form of spinning rotational
mass.
• As more renewable energy
generation is added to the utility grid,
it could result in instability and poorly
damped oscillations in AC frequency
and power on micro-grid.
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Introduction
Objectives of building a testbed
• Simulate a power fluctuation
– Motor load
– Oscillatory circuitry
• Detection of instantaneous fluctuations
– Phasor Measurement Unit (PMU)
– Instantaneous power sensor
• Verification of data-based dynamic modeling (system identification) techniques
• Damping controller design and implementation
– Embedded devices
• Capability of real-time control of an inverter
– An inverter with real-time active/reactive power control
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Testbed
Testbed – Overview
System diagram
Controller with implementation of instantaneous
power calculation and damping control
Inverter with
real-time control
Sensors
Controller
PV
System
V
V
V
L1
EMI
Filter
Grid-Tied
Inverter
A
A
L2
A
L3
Auxiliary
Relay
R-L-C Load Circuit
Overload
Protection
Contactor
Oscillatory circuitry acting
as a power fluctuation
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Switch
Circuit
Breaker
GRID
Testbed – Key Components
“Portable” cabinet
Grid-Tied Inverter
Controller Cabin
Oscillatory R-L-C circuitry
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Testbed – Key Components
Controller
Manufacturer: National Instruments
Model: NI myRIO-1900
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Processor:
Memory:
Wireless:
Analog Input:
Analog Output:
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Xilinx Z-7010 (Duo Core, 667MHz)
(ROM) 256MB
(DDR3) 512MB
IEEE 802.11 b,g,n
12 bits – 500 kS/s
12 bits – 345 kS/s
Preliminary Tests
Preliminary Tests
Test of simulating power fluctuation
• For safety consideration, a programmable DC
power supply is installed for testing.
• The power fluctuation generated by the
oscillatory circuitry is measured and modeled as
follows:
100
System Measurement
Model Simulation
80
3-phase Real Power
60
40
20
0
-20
-40
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1
1.2
1.4
1.6
1.8
2
2.2
Time [sec]
2.4
2.6
2.8
3
Preliminary Tests
Four-quadrant grid-tied inverter (GTI)
Manufacturer: One-Cycle Control (OCC)
Model: GTI3100A6208/3652IR-PQ
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Max. Power:
AC Voltage Range:
Rated DC Voltage:
Max. AC/DC Current:
Weight:
Size:
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36kW
208V ±10%
365VDC
100Arms / 100A
65lb
23in×17.5in×5.25in
Preliminary Tests
Capability test of real-time active/reactive power control
• Dynamic response of the OCC-GTI is tested with a step control input.
• The OCC-GTI is capable to be controlled in real time.
40
30
10
1
0
0
-10
-20
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4
4.2
4.4
4.6
4.8
5
5.2
Time (sec)
5.4
5.6
5.8
6
Step Input to GTI
Real Power
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Preliminary Tests
Verification of data-based system identification on the GTI output
• Based on the measured data obtained by previous tests, a low-order model built
within Prediction Error (PE) framework is capable to capture the dynamics.
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Measured Result
Simulated Result
3-phase Real Power
30
20
10
0
-10
-20
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4
4.2
4.4
4.6
4.8
5
5.2
Time [sec]
5.4
5.6
5.8
6
Preliminary Tests
Verification of data-based system identification on the disturbance
• Dynamic response of the oscillatory circuitry is tested.
• A low-order model built by Step-Based Realization (SBR) method is capable to
capture the dynamics well.
100
Measured Result
Simulated Result
80
3-phase Real Power
60
40
20
0
-20
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0
0.2
0.4
0.6
0.8
1
1.2
Time [sec]
1.4
1.6
1.8
2
Preliminary Tests
Damping control algorithm design and implementation
• A preliminary damping control algorithm is designed based on modeling of the
system described previously.
• The control algorithm is implemented in the controller.
Control Algorithm Design
Control Algorithm Implementation
120
100
Open-Loop Simulation
Closed-Loop Simulation
80
No Control
With Feedback Control
100
80
60
3-Phase Real Power
3-Phase Real Power
60
40
20
40
20
0
-20
0
-40
-20
-60
-40
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1
1.2
1.4
1.6
1.8
2
2.2
Time [sec]
2.4
2.6
2.8
3
-80
0
0.2
0.4
0.6
0.8
1
1.2
Time [sec]
1.4
1.6
1.8
2
Preliminary Tests
Conclusions
• The oscillatory circuitry in the testbed is able to simulate a power fluctuation.
• The grid-tied inverter provided by One-Cycle Control is capable to be controlled
in real time.
• The controller is able to process the instantaneous power calculation and realtime control.
• The designed control algorithm is able to dampen the oscillation generated by
the oscillatory circuitry.
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Future Work
Future Work
Large-scale integration tests
• Integration with Phasor Measurement Unit (PMU)
• Integration with photovoltaic (PV) systems
• Large-scale tests on UCSD micro-grid
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Thank you