Research On Single-Phase Hybrid Power Filter System For Electric Traction Substation

With the development of electrified railway, electric traction loads increase quickly. As a large power single phase rectified load, the electric traction load has many disadvantages such as heavy distortion, acute fluctuation and severe asymmetry. The safe and economic operation of power systems and of other users in points of common coupling is badly influenced. Therefore, the research on harmonic elimination scheme for electric traction load is becoming a hot subject in recent years. Firstly, the compensation characteristics of series hybrid power filter system (SHPFS) are analyzed in this paper. The influence of series resistance K produced by series active power filter (SAPF) on amplitude-frequency of source current is expatiated. The effect of SAPF on the filtering performance of passive power filter (PPF) is testified through digital simulation results. Secondly, in order to solve the time delay problem existing in harmonic detection for rapid time-varying loads, a predictive real-time harmonic current detection method is presented in this paper. The time delay produced in harmonic detection and control process is decreased by this method, and the track ability of SAPF is enhanced. The influence of the error of phase lock loop on the harmonic current detection is studied. Then it is firstly found and proved by the author, that the harmonic detection precision is not affected by the steady error of phase lock loop. Thirdly, on the basis of analyzing the control process of space vector PWM (SVPWM), the paper proposes SVPWM applied to APF control. Compared with adaptive PWM, SVPWM has better control precision and little switch loss. The controllability of APF's voltage based on single phase SVPWM is studied. The detailed implement scheme of SVPWM used in single phase SAPF is presented and used in SHPFS laboratory equipment successfully. According to the harmonic characteristics of electric locomotive typed SS4 under typical operating situations, the current module of harmonic source is proposed. The simulation modules considering SHPFS and hannnic sources in distributionsystems are set up on the basis of PSCAD/EMTDC, and detailed researches onfiltering characteristics of SHPFS are cOmPleted.The main circuit of the single phase SAPF is designed, its detection and controlsystem is also comPleted based on the digital signal PrOcessor chip TMS320C50, andthe single phase SHPFS laboratory equPmnt is set uP. Some teSts about SHPFS aremade under different PPF resonance and background hannnic voltages, the resultsindicate that SAPF alWays improves the filtering ability of PPF, and SHPFS hasbetter hannonic filtering ability and gOod aPPlication prospects.