Abstract: Permanent magnet synchronous motor（PMSM）has become the development direction of the new

generation of rail transit traction system due to its characteristics of high efficiency and high power density. Among

them，the research on the identification method of the initial position and frequency of the motor rotor in coasting

condition is an important part of the position sensorless control technology of PMSM. Therefore，the zero voltage

vector single pulse method and double pulse method were firstly studied. When the PMSM was in coasting

condition，one or two pulses were short-circuited by all the lower bridge arms of three-phase inverter，and the initial position and frequency of rotor were obtained according to the short-circuit response current. On this basis，a method of short circuit time selection of zero voltage vector pulse method and a zero voltage vector compound pulse method were proposed to ensure that PMSM can stably restart at different coasting frequency. Through Matlab/Simulink simulation and the test conducted in the test center of CRRC Dalian Electric Traction R&D Center Co.，Ltd.，the results show that PMSM under different frequencies can stably restart，the frequency identification error is less than 0.6 Hz，the rotor position identification error is less than 5°.

      Key words: permanent magnet synchronous motor（PMSM）；coasting condition；zero voltage vector pulse

method；initial rotor position and frequency identification