Interaction Analysis Among PMSG-Based Wind Turbines And VSC-HVDC

In order to solve the problems of environmental pollution and energy depletion caused by fossil energy consumption,wind power generation and voltage source converter-high voltage direct current(VSC-HVDC)transmission have been widely used.With the increase of the proportion of wind power,the analysis of oscillation mechanism and the location of oscillation source will be more complicated.In addition,the dynamic interaction between wind turbines(WTs)and VSC-HVDC is closely related to the energy exchange and accumulation between DC capacitors.For the small signal stability problem dominated by DC capacitance and related control in power system,this paper calls it the DC voltage control(DVC)scale dynamic stability problem.For describing the dynamic interaction between different equipment in power system more clearly and accurately,the specific research contents of this paper are as follows to explain the mechanism of the system sub-synchronous oscillation(SSO):(1)The typical control methods and principles of the PMSG-based WT and VSC-HVDC are introduced.And the overall control scheme of the research object is determined.The small signal models of the converter station system with N PMSG-based WTs interconnected and four PMSG-based WTs connected to the VSC-HVDC are established under DVC scale.(2)The concept of self-/en-stabilizing is defined,and an interaction analysis method based on self-/en-stabilizing functions is proposed.The general expressions of self-/en-stabilizing functions though different paths are calculated for N PMSG-based WTs systems.In addition,the corresponding system stability criteria are given,and the parameter sensitivity based on this method is also proposed.Taking five PMSG-based WTs connected to infinite power supply as an example,by comparing the eigenvalues of the eigenvalue method and the proposed method.The effects of DVC,PLL control parameters and system parameters on the system stability are discussed.Finally,the simulation results in time domain are given,and the correctness of the proposed method is verified.(3)Take four PMSG-based WTs connected to VSC-HVDC as an example.Based on the established small signal model of the corresponding system,the expressions of the self-/en-stabilizing functions are derived.Comparing the eigenvalues obtained by the eigenvalue method with the results obtained by the method,the stability criterion and the parameter sensitivity method are also given.The influences of DVC,PLL,TVC control parameters and system parameters on system stability are discussed.Finally,the extensibility of the proposed method are verified by time domain simulation results.