4/9/2015
DFIG based Wind Turbine Modeling in the Real Time Digital Simulator
Rishabh Jain, Dr. Herbert L. Hess, Dr. Brian K. Johnson
•Better Interconnectivity
What has changed??
•Smarter Grid Operation
•Better and more robust controls
•More communication based approaches
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4/9/2015
•Inflation
•Environmental concerns
What else changed??
•Better support for Renewable
Generation
•Increasing contribution of Distributed generation (mostly PV, Wind, Geothermal).
• 1990s – Wind Turbines were required to disconnect from Grid during faults
Grid Code is changing too!
Induction Generators consume VARs
Worsen voltage sags during faults
More time needed to recover
• 2010s – Wind turbines need to stay
connected and support the Grid during
faults
• Better Power electronic control can supply
VARs
• Islanding is discouraged in current standards
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Wind Turbine Types
• SCIG (Squirrel Cage Induction Generator) tied to a Wind Turbine
• No variable speed control
Type 1
• Capacitor banks required for reactive compensation
• Generates power only near rated wind speeds
Wind Turbine Types
• SCIG tied to a Wind Turbine
Type 2
• Narrow range of variable speed generation due to rotor resistance control
• Capacitor banks required for Reactive compensation
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4/9/2015
Wind Turbine Types
• Doublyy Fed Induction Generator ((DFIG) tied
)
to a Wind Turbine
• +/‐ 30% variable wind speed operation
Type 3
• Back‐to‐back VSCs – rated at 30%
• Power extracted from Rotor and stator in Super‐sync mode
Wind Turbine Types
Type 4
• Synchronous Generator tied to a Wind Turbine via back‐to back VSCs
• Can generate power for very low wind speeds
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Controller Design
 Exports the power generated by Rotor at Super‐synchronous speeds
 Imports power for the Rotor at Sub‐
synchronous speeds
Grid side Controller
 Tracking the System Frequency very important
 Implemented using Phase locked loop
Controller Design
Grid side Controller
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4/9/2015
Controller Design
 Artificially excites Rotor at lower wind speeds by increasing the current to get the same flux linkage
 Extracts power from Rotor at super‐
synchronous wind speeds
Rotor side Controller
 Needs to know rotor current frequency at all times
 Needs to regulate the Rotor current for maximum power point tracking
Assumptions
Vdc is constant
I am NOT!!
I can help!
Vdc is constant
DC Regulator
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Controller Design
 Many implementations – Here, it is a PI controller
 Regulates the DC voltage
DC Voltage Regulator
 Regulates the power imported/exported by the G id side
Grid
id controller
ll based
b d on requirements
i
of f the Rotor side.
Controller Design
DC Voltage Regulator
Linearize the controller
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Controller Design
Grid side Controller
Controller Design
Phase Locked Loop (Stator)
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Controller Design

Phase Locked Loop (Rotor)
• The RTDS: The Real Time Digital Simulator
What is the RTDS?
• Hardware in the loop configuration
• Possible to simulate a system in real time
• Export signals to relays and test their response
Courtesy: RTDS technologies
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Model Validation
Torque‐Speed
Torq
e Speed
Characteristics
Characteristics are similar to a conventional Induction Machine Library Machine Model is valid!
Model Validation
Operational Characteristics
Operational Characteristics are similar to the Type 3 based Wind Turbines
Below rated Wind Speed: Prot < 0, Pstat > 0
Above rated Wind Speed: Prot > 0, Pstat > 0
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Model Validation
Source
 Benchmark ‐ IEEE PSRC Report on "Fault Current Contributions from Wind Plants"
 Fault Type ‐ Double Line to Ground (B‐C‐G)
Fault Fa
lt Characteristics
 Results:
 Closely matched to Aggregated Wind Farm Model
Figure: B‐C Fault from Aggregated RTDS Model
Figure: B‐C Fault from reference [1]
They are SIMILAR!!
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4/9/2015
Model Validation
Comparision
p
with Switching Model
Figure: Stator and Rotor Current outputs from the Switching Model
Model Validation
Comparision
p
with Switching Model
Figure: Stator and Rotor Current outputs from the Averaged Model
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Operation Plots
DC Link Regulator
Operation Plots
DC Link Regulator
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Operation Plots
Output Current Tracking
(Rotor and Stator)
Operation Plots
Speed and Torque plots v/s time in steady state
d
in Super‐sync mode
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 A Type 3 Wind generation model established which utilizes the capabilities of hardware‐in‐the‐loop systems (the RTDS for our case) for protection system analysis in real time.
 Aggregation of Wind turbines validated
 Controllers largely based on the design in [2].
C
ll l
l b d h d i i [ ]
 Details and results of modeling controllers for a back‐to‐back VSC for a Type‐3 Wind generation system. T
Conclusions
 The controller design is implemented in RSCAD and validated from other publications.  Real time interaction with system possible using the Run‐time interface
 Type 3 WT systems’ behavior analysis for multiple operating and fault conditions.
 Can be connected as a block to another test networks, and test their fault response.
References
1. Jeff Barsch, George Bartok, Gabriel BenmouyaI, Oscar Bolado, Brian Boysen, Sukumar Brahma, Stephan Brettschneider, Zeeky Bukhala, and Jeff Burnworth. Fault current contributions from wind plants Technical report
plants. Technical report.
2. Yazdani, Amirnaser, and Reza Iravani. Voltage‐
sourced converters in power systems: modeling, control, and applications. John Wiley & Sons, 2010.
3. Phase Locked Loop (atan2 Type), Application Note in Real Time Digital Simulator Controls Library Manual (RSCAD Version), Winnipeg, MB: RTDS T h l i Technologies, 2014.
4. Jain, Rishabh. Grid Integrated Type 3 Wind Systems ‐
Modeling, and Line Protection Performance Analysis using the RTDS, Masters Thesis. August 2014
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