Research On The Impact Of H-SSSC On Wind Power System Stability And Distance Protection

With the gradually increasing installed capacity of wind power,the problem of sub-synchronous oscillation(SSO)when large-scale wind farms transmit power through fixed series compensation cannot be ignored.In order to alleviate SSO caused by fixed series compensation,the doubly-fed induction generator(DFIG)is connected to the grid by hybrid series compensator(HSC)device composed of H-bridge cascaded static synchronous series compensator(H-SSSC)and fixed series compensation(FSC)in this paper.For doubly-fed induction generator transmitted through the HSC device transmission system,the theoretical study of its stability is rarely reported in the literature.In addition,H-SSSC,as a new series compensation device,its integration is bound to have an impact on the distance protection on the line.At present,there are few studies on new distance protection schemes containing H-SSSC lines.H-SSSC device and doubly-fed induction generator transmitted through the HSC device transmission system is the main research object in this paper.The stability problem of each system is analyzed,and for the integration of H-SSSC,a new distance protection scheme to eliminate its impact is proposed.The content is as follows.In this paper,a small-signal model is firstly established based on the modular modeling method for the H-SSSC device,and the accuracy of the model is verified by comparison with the step response curve of the PSCAD/EMTDC time domain simulation model,which lays the theoretical foundation for subsequent research.Secondly,the eigenvalue analysis method is used to reveal the influence of H-SSSC decoupling controller and voltage equalization controller parameters on its stability.Finally,the theoretical analysis was verified by using PSCAD/EMTDC time domain simulation model.The eigenvalue analysis of doubly-fed induction generator transmitted through the HSC device transmission system is applied,the impact of the integration of H-SSSC on the system stability is studied in detail.The main influencing factors include the proportion of H-SSSC in the HSC device,the voltage outer-loop and current inner-loop controller parameters in decoupling control.The analysis results show that the system stability is enhanced as the proportion of H-SSSC in HSC device and the parameters of the voltage outer-loop controller in decoupling control increase,while the parameters of the current inner-loop controller have less effect on the stability of the system.Aiming at the problems caused by H-SSSC for line relay protection,This paper focuses on the analysis of the impact of H-SSSC on distance protection under different compensation methods and different series compensation;a new distance protectionscheme is proposed based on single-ended electrical quantities,the distance protection zone I of this scheme uses the percentage of the fault distance and its standard deviation as the criterion,which can eliminate the impact of H-SSSC on distance protection;combined with the time-domain simulation model,the feasibility of this scheme is verified under different fault conditions.