Parameter Sensitivity Analysis for Sub-Synchronous Oscillations in Wind-Integrated Power Systems

Transcription

1 LOGO Parameter Sensitivity Analysis for Sub-Synchronous Oscillations in Wind-Integrated Power Systems Meng Wu 1, Rongfu Sun 2, Lin Cheng 3, and Le Xie 1 1: Texas A&M University, 2: China Jibei Power Grid, 3: Tsinghua University

2 Wind Farm SSO Events in Real World Wind Farm SSO in Real World In Oct. 29, ERCOT reported a SSO in wind-integrated system, triggered by a single line-to-ground fault. A NREL report in 213 presents several SSO incidents recorded by wind power plants of Oklahoma Gas & Electric Company. China Jibei Power Grid also encounters SSO induced by wind power integration. 2 Y. H. Wan, Synchronized phasor data for analyzing wind power plant dynamic behavior and model validation, 213. P. Belkin, Event of , in CREZ Technical Conference, 21.

3 Basic Characteristics of Wind Farm SSO Characteristics of Wind Farm SSO Electrical oscillation typically in the frequency range of 2 5 Hz. Caused by interactions among wind generators, controllers of power electronic devices, and series compensated network. Can be difficult to filter since the oscillation frequency may be close to synchronous frequency. DFIG-based wind turbine are most sensitive to SSO among all kinds of wind turbines. 3 Garth Irwin, Sub-synchronous control interaction studies related to the CREZ project, 21

4 How to Deal With Wind Farm SSO? Wind Farm SSO Phenomenon Identify Root Cause Identify Critical Parameters& Inputs Small-signal instability induced by certain parameter settings and input conditions Eigenvalue sensitivities with respect to system parameters & input conditions Wind Farm SSO Can Be Eliminated Effectively Verification Through Simulation Sensitivity-Based Mitigation Control Sensitivity-based optimal parameter adjustment for wind farm SSO mitigation 4

5 Wind Farm SSO vs Parameters & Inputs System Nonlinear Model System Linearized Model Small-Signal Stability Study eigenvalues of A matrix: negative real part -> stable positive real part -> unstable A matrix of the linearized system can be expressed as function of ONLY system parameters & inputs Linearized State Matrix 5 Wind SSO Stability Small Signal stability of Wind Farm SSO is determined by ONLY system parameters & inputs

6 How to Deal With Wind Farm SSO? Wind Farm SSO Phenomenon Identify Root Cause Identify Critical Parameters& Inputs Small-signal instability induced by certain parameter settings and input conditions Eigenvalue sensitivities with respect to system parameters & input conditions Wind Farm SSO Can Be Eliminated Effectively Verification Through Simulation Sensitivity-Based Mitigation Control Sensitivity-based optimal parameter adjustment for wind farm SSO mitigation 6

7 Eigenvalue Analysis Low Wind Speed System Condition Steady-State Infinite Bus V = 1 pu Steady-State Infinite Bus θ = rad Steady-State DFIG P out = 1 pu Steady-State DFIG Power Factor =.9 Wind Speed = 4 m/s Series Compensation Level = 52.38% 5 oscillation modes in total: 3 sub-synchronous and 2 super-synchronous 22.6 Hz sub-synchronous mode is unstable in low wind speed condition. The other two sub-synchronous modes are stable with small damping compared with supersynchronous modes. 7

8 Sensitivity Analysis for SSO Modes.1 Eigenvalue Sensitivities for 22.6 Hz Mode D K Jw Jg Xls Xm Xlr Rs Rr Rnt Lnt Cnt Xxf Kte Tte Kiqr Tiqr Kqs Tqs Kidr Tidr Kqg Tqg KiqgTiqg Kdc Tdc KidgTidg Cdc System Parameters -1 Wr Pe Qe Eq Ed Vdc Operating Conditions.1 Eigenvalue Sensitivities for 8.9 Hz Mode D K Jw Jg Xls Xm Xlr Rs Rr -.1 Rnt Lnt Cnt Xxf Kte Tte Kiqr Tiqr Kqs Tqs Kidr Tidr Kqg Tqg KiqgTiqg Kdc Tdc KidgTidg Cdc System Parameters Wr Pe Qe Eq Ed Vdc Operating Conditions.1 Eigenvalue Sensitivities for 1.27 Hz Mode 4 x D K Jw Jg Xls Xm Xlr Rs Rr Rnt Lnt Cnt Xxf Kte Tte Kiqr Tiqr Kqs Tqs Kidr Tidr Kqg Tqg KiqgTiqg Kdc Tdc KidgTidg Cdc System Parameters -4 Wr Pe Qe Eq Ed Vdc Operating Conditions Torsional System DFIG System Network System Controller System Operating Conditions 8

9 Sensitivity Analysis for SSO Modes 22.6 Hz mode is sensitive to network parameters and DFIG converter controller parameters. 8.9 Hz mode is sensitive to DFIG parameters and network parameters Hz mode is sensitive to torsional system parameters, network parameters and controller parameters. Network inductor and capacitor values are of high sensitivities in all three sub-synchronous modes. Parameters in current control loops of converter controllers have higher sensitivities over torque control loops. DFIG rotor speed (determined by wind speed) has significant influence on all three modes DFIG Rotor Speed (rad/s) DFIG Rotor Speed at Different Wind Speed System Synchronous Speed Wind Speed (m/s) 9

10 How to Deal With Wind Farm SSO? Wind Farm SSO Phenomenon Identify Root Cause Identify Critical Parameters& Inputs Small-signal instability induced by certain parameter settings and input conditions Eigenvalue sensitivities with respect to system parameters & input conditions Wind Farm SSO Can Be Eliminated Effectively Verification Through Simulation Sensitivity-Based Mitigation Control Sensitivity-based optimal parameter adjustment for wind farm SSO mitigation 1

11 Simulation Results Before Parameter Adjustment.3 T ransmission Line Current (pu).12 FFT Analysis of Line Current Time (s) Frequency (Hz) Oscillation frequency of transmission line current: Hz.1 DFIG Electrical T orque (pu) FFT Analysis of DFIG Electrical T orque.1.8 Oscillation frequency of DFIG electrical torque: Hz Time (s) Frequency (Hz)

12 Simulation Results Before Parameter Adjustment.2 T ransmission Line Current (pu).12 FFT Analysis of Line Current Gain of GSC current control loop (K iqg ) is tuned for SSO mitigation from 1. to Time (s) Frequency (Hz) DFIG Electrical T orque (pu) FFT Analysis of DFIG Electrical Torque (p.1 Sensitive gains of converter controller are adjusted. Unstable eigenvalues are moved left effectively Frequency (Hz)

13 Conclusions Conclusions What Happened: Sub-synchronous oscillation happens in windintegrated power system. Why It Occurred: Inappropriate operating conditions, seriescompensated network parameters as well as DFIG converter controller parameters. How To Eliminate: Eigenvalue adjustment based on sensitivity analysis and parameter tuning (including DFIG converter controller gains and network compensation level). Future Work Extend sensitivity analysis to multi-machine systems. Design optimal mitigation control strategies for wind farm SSO. 13

14 References References [1] Y. H. Wan, Synchronized phasor data for analyzing wind power plant dynamic behavior and model validation, National Renewable Energy Laboratory, CO, Tech. Rep. NREL/TP , Jan 213. [2] P. Belkin, Event of , in CREZ Technical Conference, Jan 21. [3] Z. Lubosny, Wind Turbine Operation in Electric Power Systems: Advanced Modeling. Berlin, Germany: Springer-Verlag, 23. [4] P. C. Krause, O. Wasynczuk, and S. D. Sudhoff, Analysis of Electric Machinery. NY: IEEE Press, [5] P. M. Anderson, B. L. Agrawal, and J. E. Van Ness, Subsynchronous Resonance in Power Systems. NY: IEEE Press, 199. [6] M. Wu, R. Sun, L. Cheng, and L. Xie, Parameter sensitivity analysis for sub-synchronous control interactions in wind-integrated power systems, submitted to CIGRE Grid of the Future Symposium, 214, Houston, TX, Oct

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