Research And Simulation Of Sub-Synchronous Oscillation With Large-Scale Wind Power Transmission System

The distribution characteristics of our nation’s wind energy resources and power load determine that series capacitor compensation is widely used in long-distance wind power transmission and brings severe sub-synchronous oscillation(SSO) problem to large-scale wind power plants. Therefore, studying the sub-synchronous oscillation problem in large-scale wind power transmission system thoroughly has fundamental practical significance to the development of our nation’s power utility. This paper takes DFIG-based wind plant with series capacitor compensated transmission system as study object, and studies the sub-synchronous oscillation problem in large-scale wind power transmission system.Firstly in this paper, a detailed modeling of doubly fed induction generator(DFIG) system is conducted, including wind turbine, drive train, induction generator, back-to-back converter, active power control, reactive power control, pitch angle control and phase lock loop. Then by changing wind speed and reactive power reference separately, the model’s capability of decoupling control of active power and reactive power is verified, thus the foundation of following sub-synchronous oscillation study is established.Secondly, based on the mathematical model of DFIG derived above, the electromagnetic transient model of DFIG-based wind plant with series capacitor compensated transmission system is conducted on PSCAD/EMTDC platform, the sub-synchronous oscillation phenomenon after system disturbance is simulated, and the influences of series capacitor compensation device, wind speed and series compensation degree on system SSO characteristics are analyzed, then frequency analysis of simulation results are conducted. Research results indicate that series capacitor compensation device and wind speed have evident impacts on system SSO characteristics, while series compensation degree has little impact.Finally, the influence of DFIG control parameters on system SSO characteristics is analyzed. Research results indicate that phase lock loop control parameters, rotor side converter inner ring proportion coefficient and grid side converter outer ring proportion coefficient have evident impacts on system SSO characteristics, while converter integral coefficients have little impact.