Small Signal Impedance Model Of Vehicle-Grid Electrical Coupling System And Compensation Device Based On Harmonic State-Space

As electrified high-speed railway develops rapidly,the number of electric multiple units(EMUs)has increased significantly.However,high-density EMUs may trigger lowfrequency oscillations(LFO)in the vehicle-grid electrical coupling system.Some suppression methods against LFOs have been proposed,but none of them can analyze the suppression mechanism in detail.This thesis is the first to propose small-signal impedance modeling for vehicle-grid electrical coupling systems and compensation devices based on harmonic state-space(HSS).Here,a small signal impedance model of China railway highspeed 5(CRH5)EMUs based on HSS is deduced,the impedance stability analysis method is applied into the analysis of LFOs mechanism,and factors of LFOs are analyzed.A smallsignal impedance model of the Cascaded H-Bridge Static Synchronous Compensator(CHBSTATCOM)based on HSS is built,and the impedance stability of CHB-STATCOMaccessed vehicle-grid electrical coupling system is also analyzed.Firstly,a small-signal impedance model of the vehicle-grid electrical coupling system based on HSS is deduced.A small-signal impedance model of CRH5 based on HSS is deduced and then verified via Matlab / Simulink platform and Star Sim semi-physical platform.The analysis of the LFOs mechanism and impact of the number of EMUs and gridside parameters on the stability of vehicle-grid electrical coupling system is made.Secondly,a small-signal impedance model of the single-phase compensation device based on HSS is deduced.A single-phase CHB-STATCOM that fits vehicle-grid electrical coupling system is used.Small-signal impedance models of the CHB-STATCOM based on HSS under open-loop control and close-loop control are deduced and then verified via the Matlab / Simulink platform and Star Sim semi-physical platform.Finally,the impact of the compensation device on the stability of vehicle-grid electrical coupling system is analyzed on the basis of small-signal impedance models of vehicle-grid electrical coupling system and compensation device based on HSS.The suppression mechanism of CHB-STATCOM against LFOs and impact of CHB-STATCOM on the stability of the vehicle-grid electrical coupling system are both analyzed.The results of stability analysis are verified via Matlab / Simulink platform.