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8/9/2019 Analysis of SSR in DFIG Based Wind Farms - A Toturial
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Presenter:
Hossein A. Mohammadpour
February 2014Grid-Connected
AdvancedPower ElectronicsSystems GRAPES
Supervised by :
Prof. Enrico Santi
mailto:[email protected]:[email protected]:[email protected]:[email protected]8/9/2019 Analysis of SSR in DFIG Based Wind Farms - A Toturial
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1. H. A. Mohammadpour , E. Santi, Modeling and control of gate - controlled series capacitor interfaced with aDFIG- based wind farm, IEEE Transactions on Industrial Electronics, DOI:10.1109 /TIE.2014.2347007, Availableon-line: 12 August 2014.
2. H. A. Mohammadpour , E. Santi, Sub -synchronous resonance analysis in DFIG-based wind farms: definitionsand problem identification - Part I, IEEE Energy Conversion Congress and Exposition (ECCE) 2014, pp. 1 - 8,14 - 18 September, Pittsburgh, PA , USA.
3. H. A. Mohammadpour , E. Santi, Sub -synchronous resonance analysis in DFIG-based wind farms: mitigationmethods - TCSC, GCSC, and DFIG controllers - Part II, IEEE Energy Conversion Congress and Exposition (ECCE),pp. 1 - 8, 14 - 18 September, Pittsburgh, PA , USA.
4. H. A. Mohammadpour, Y. J. Shin, E. Santi,SSR analysis of a DFIG-based wind farm interfaced with a gate-controlled series capacitor, IEEE Twenty -Ninth Annual Applied Power Electronics Conference and Exposition(APEC) 2014, pp. 3110 - 3117, 16 - 20 March, Fort Worth, TX, USA.
5. H. A. Mohammadpour , E. Santi, Sub -synchronous resonance mitigation in wind farms using gate-controlledseries capacitor, IEEE 4th International Symposium on Power Electronics for Distributed Generation Systems(PEDG) 2013, pp. 1 - 6, 8 - 11 July, Rogers, AR, USA.
Please ask for full paper at [email protected] , if you do not have
access to the paper.s Please do not hesitate to ask any questionregarding this presentation.Thanks you.Hossein
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Offshorewind farm
Long HVACtransmission line Inf. bus
Fixed series capacitor
Maximum transmittable power is reduced by transmission line reactance.Indeed, the longer the line, the less maximum transmittable power.
Series compensation is the most economical way to increase maximumtransmissible power of a transmission line.
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Fixed series capacitor
Sub-synchronous resonance(SSR) may appears in thesystem and make the systemunstable.
But:
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ControlSeries FACTS
A well-designed FACTScontroller can damp the SSRand stabilize the wind farm.
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Gate-controlledseries capacitor (GCSC)
1. A SSR damping controller is used to stabilize the wind farm.2. Eigenvalue analysis approach is used to design the SSRDC.3. Residue-based analysis is used to find the optimum input control signal (ICS)
to SSRDC.4. Root-locus approach is used to compute SSRDC gain.5. PSCAD /EMTDC is used to validate the approach.
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Introduction to Wind FarmsSeries Compensation Basics and FACTS Devices
Modeling of Series Compensated DFIG Studied Power System Basics: Small-Signal Stability and abc to dq Transformation Mathematical Modeling and Implementation in Matlab/Simulink
Sub-Synchronous Resonance (SSR) Definition and Basics Eigenvalue Analysis of DFIG Detailed Time-Domain Simulation in PSCAD/EMTDC
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Gate-Controlled Series Capacitor (GCSC) Basic Structure Power Scheduling Controller (PSC) SSR Damping Controller (SSRDC)
SSR Damping Controller (SSRDC) Design Residue-Based Analysis for Optimal Input Selection to SSRDC Rotor speed, line current, and voltage across GCSC Root-Locus Diagram for Computing SSRDC Gain
Detailed Time-Domain Simulation in PSCADConclusion and Future Work
8USC & DOE
8/9/2019 Analysis of SSR in DFIG Based Wind Farms - A Toturial
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Introduction to Wind FarmsSeries Compensation Basics and FACTS Devices
Modeling of Series Compensated DFIG Studied Power System Basics: Small-Signal Stability and abc to dq Transformation Mathematical Modeling and Implementation in Matlab/Simulink
Sub-Synchronous Resonance (SSR) Definition and Basics Eigenvalue Analysis of DFIG Detailed Time-Domain Simulation in PSCAD/EMTDC
9USC & DOE
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Advantages :No air pollutionNo greenhouse gassesDoes not pollute water with mercury
No water needed for operations
Disadvantages:Intermittent source of power
Only when the wind blows (night? day?)Transmission constraints Offshore wind farms are far away from customers Need long transmission lines
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Offshore Wind Farms vs Onshore Wind Farms:Much biggerFurther distance from customersRequire a reliable transmission lines with high voltage
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Studies show that HVAC option is technically feasible for distances larger
than 250 km provided that capacitive series compensation is used.
Transmission Line Options:High voltage DC (HVDC)
High voltage AC (HVAC)
Expensive
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Type A: ConventionalInduction
Generator (fixed speed)
Type B: Wound-Rotor InductionGenerator w/variable Rotor
Resistance
Type C: Doubly-Fed InductionGenerator (variable speed)
Type D: Full-Converter Interface
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Introduction to Wind Farms
Series Compensation Basics and FACTS Devices
Modeling of Series Compensated DFIG Studied Power System Basics: Small-Signal Stability and abc to dq Transformation Mathematical Modeling and Implementation in Matlab/Simulink
Sub-Synchronous Resonance (SSR) Definition and Basics Eigenvalue Analysis of DFIG Detailed Time-Domain Simulation in PSCAD/EMTDC
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The most economical way to increase the transmittable powerDisadvantage:
It can increase the risk of sub-synchronous resonance (SSR)
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Definition:Alternating current transmission systems incorporating powerelectronics-based and other static controllers to enhancecontrollability and increase power transfer capability.
Advantages of FACTS DevicesTransient stability improvementInter-area oscillation damping
Greater flexibility in power networkDeliver the optimum power
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Sub-synchronous resonance mitigation
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Static VARCompensator - SVC
Thyristor ControlledSeries Compensator - TCSC
Gate ControlledSeries Compensator - TCSC
Unified Power FlowController (UPFC)
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Solid State SeriesCompensator - SSSC
Static SynchronousCompensator - StatCom
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Introduction to Wind Farms
Series Compensation Basics and FACTS Devices
Modeling of Series Compensated DFIG Studied Power System Basics: Small-Signal Stability and abc to dq Transformation Mathematical Modeling and Implementation in Matlab/Simulink
Sub-Synchronous Resonance (SSR)
Definition and Basics Eigenvalue Analysis of DFIG Detailed Time-Domain Simulation in PSCAD/EMTDC
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100 MW wind farm is aggregation of 2 MW x 50 DFIG wind turbines
Wind turbine aerodynamicsand a 3rd order two-mass
shaft system
A 4th order series compensatedtransmission line model6th order induction
generator model
An 8th order rotor andgenerator side converter
controllers
A 1st order DC link model
The entire system is of 22nd order
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Any dynamic system can be expressed by a set of n first
order nonlinear ordinary differential equations
For small disturbances, the differential equations can be
linearized around operating points and can be expressed in
state-space form.
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Stationary circuit variables referred to a synchronously rotating reference frame.
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Typical abc-to-dq transformation
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RSC real power
GSC real power
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Matlab/Simulink Model
A first order DC-link model
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Maximum Power Point Tracking (MPPT)
The aim of the GSC and RSC are to enable theDFIG to work on the MPPT curve.
Rotor-side converter (RSC) controllers
Grid-side converter (GSC) controllers
MPPT is used in order to achieve highefficiency in the DFIG wind farm.
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Matlab/Simulink Model
A 6 th order induction generator model
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24USC & DOE
Matlab/Simulink Model
A 4 th order transmission line model
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Matlab/Simulink Model
A 3 rd order mechanical system model
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Introduction to Wind FarmsSeries Compensation Basics and FACTS Devices
Modeling of Series Compensated DFIG Studied Power System Basics: Small-Signal Stability and abc to dq Transformation Mathematical Modeling and Implementation in Matlab/Simulink
Sub-Synchronous Resonance (SSR) Definition and Basics Eigenvalue Analysis of DFIG Detailed Time-Domain Simulation in PSCAD/EMTDC
26USC & DOE
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Equivalent circuit of system under sub-synchronous frequency
= + + : The entire reactance seen from
infinite bus : Frequency corresponding to rotorspeed
andIf
sum of resistancesof the armatureand the network
< 0
>
Then there will be a negativeresistance at the sub-synchronous
frequency, and the sub-synchronouscurrent will increase with time.
This phenomenon is called induction generator effect (IGE).IGE is the major problem in wind farms.
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Wind
speed
( / )
Mode 1
SSR Mode Mode 2
Sup-SR Mode Mode 3
Shaft Mode
Mode 4
Elec. Mech. Mode
7 . . 5.3126 640.1460 1.0405 5.9975 18.4753 95.5005
8 0.7958 106.4835 6.1834 642.3497 1.5952 5.7523 7.3302 64.5295
9 4.0322 107.0110 7.1346 645.3255 3.2322 4.6631 2.4978 31.2250
( ) Mode 1
SSR Mode Mode 2
Sup-SR Mode Mode 3
Shaft Mode Mode 4
Elec. Mech. Mode
50 5.3908 179.2258 4.9224 572.6882 0.9432 6.0249 4.8676 97.6290
75 . . 5.2066 617.1976 0.9221 5.9992 9.9111 99.9693
90 . . 5.3126 640.1460 1.0405 5.9975 18.4753 95.5005
I. High series compensation, e.g. 90 , and different wind speeds
II. Low wind speed, e.g. 7 m/s, and different series compensation levels
IGE-SSR in DFIG is affected by:Wind speed
Series compensation level30USC & DOE
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At lower wind speed, i.e. 7 m/s, even at a very realistic compensation level, i.e. 75%,the DFIG wind farm is unstable due to SSR Mode.
Time-domain simulation confirms the eigenvalue analysis.
Electric Torque
Rotor Speed
Terminal Voltage
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At higher wind speed, i.e. 9 m/s, even at a very high compensation level, i.e. 90%, theDFIG wind farm is still stable
Electric Torque
Rotor Speed
Terminal Voltage
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Gate-Controlled Series Capacitor (GCSC) Basic Structure Power Scheduling Controller (PSC) SSR Damping Controller (SSRDC)
SSR Damping Controller (SSRDC) Design Residue-Based Analysis for Optimal Input Selection to SSRDC Rotor speed, line current, and voltage across GCSC Root-Locus Diagram for Computing SSRDC Gain
Detailed Time-Domain Simulation in PSCADConclusion and Future Work
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Considered signals:
a) Rotor speedb) Line currentc) Voltage across GCSC
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For a complex root , the residue is a complex number, which can beconsidered as a vector having a certain direction.
, Right and left eigenvectors
In a root locus diagram, is representation of the direction and magnitudeof the closed loop eigenvalue , which leaves the pole .
Basics:
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The above equations show that residue influences closed-loop systemroot, by determining the direction and magnitude of it.
Suppose dynamics of all eigenvalues are ignored, except one specific eigenvalue, .
If the magnitude of the residue is large enough, then a smaller gain isneeded for the feedback control system
= =
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This will increase the difficulty of thecontroller design.
The reason is that a simpleproportional controller chosen toincrease damping of the SSR mode willdecrease the damping of the SupSRmode.
The residue magnitude ofthe SSR mode is small.
A larger gain is needed forthe feedback control.
The residues of the SSR andSupSR modes are in an opposite direction.
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However, since the residues of the SSRand SupSR modes in this case point inopposite directions, stabilizing the SSRmode via a feedback gain will decreasethe SupSR mode damping.
The residue magnitude ofthe SSR mode is large.
A smaller gain is needed forthe feedback control.
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The SSR and SupSR modes are in the same
directions. This make the design of thefeedback control simple so that a smallgain will be enough to force both the SSRand SupSR modes to move to the left andmake the system stable.
The residue magnitude of
the SSR mode is large.
A smaller gain is needed forthe feedback control.
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Destabilizing the SupSR mode, while stabilizing the SSR mode.
SSR Mode
SupSR Mode
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All system modes could be stabilized using GCSC voltage as ICS.
SSR Mode
SupSR Mode
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Gate-Controlled Series Capacitor (GCSC) Basic Structure Power Scheduling Controller (PSC) SSR Damping Controller (SSRDC)
SSR Damping Controller (SSRDC) Design Residue-Based Analysis for Optimal Input Selection to SSRDC Rotor speed, line current, and voltage across GCSC Root-Locus Diagram for Computing SSRDC Gain
Detailed Time-Domain Simulation in PSCADConclusion and Future Work
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Super-synchronous oscillations
Electric Torque Terminal Voltage
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1. Time-domain simulation verifies the designed controller.2. A well-designed GCSC can damp the oscillation.3. Voltage across the GCSC is an optimal input control signal to SSRDC.
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The GCSC can stabilize the SSR mode.
A control system design procedure is presented for GCSC.
Rotor speed, line current, and cap. Voltage tested as ICS to SSRDC block.
The best signal as ICS to SSRDC block is voltage across series capacitor.
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Supported by NSF I/U CRC forGrid-Connected Advanced Power Electronics Systems
(GRAPES)
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