A Flying Restart Strategy for Position Sensorless PMSM Driven by Quasi-Z-Source Inverter

The accurate estimation of rotor position and speed before flying restart is of great significance to improve the operation reliability of permanent magnet synchronous motor systems. The traditional multizero vector short-circuit method can improve the estimation accuracy of speed and rotor position, but the increased number of short-circuits reduces the electromagnetic torque response speed after the power supply recovers. In order to accurately estimate the initial speed and rotor position before the flying restart and effectively improve the electromagnetic torque response speed, a shoot-through zero vector short-circuit method based on quasi-Z-source inverter (qZSI) is proposed. This method breaks the limitation of regulating DC link voltage under the normal operation of the motor in the conventional methods, and puts forward a new idea of advancing the regulation of the DC link voltage to the stage of abnormal operation before the motor restarts. By designing the insertion mode of the mixed vectors and analyzing the action time of each vector before the flying restart, the accurate estimation of position and speed is realized and, meanwhile, the boost of the qZSI’s DC link voltage is achieved, thus giving the sensorless flying restart method a faster torque response speed for the PMSM system driven by qZSIs.