Research on high-speed operation of hybrid-inverter fed open winding permanent magnet synchronous motor

This paper introduces a modified direct torque control (DTC) strategy for hybrid-inverter fed open winding permanent magnet synchronous motor (PMSM). The hybrid-inverter drive system is composed of a main inverter (MI) powered by a DC voltage source and a conditioning inverter (CI) connected to a capacitor. A reference torque and stator flux linkage calculating method for DTC incorporating flux weakening (FW) is proposed by utilizing the mathematical model in the reference frame synchronized to the stator flux linkage. A strategy for decomposing the reference voltage into active and reactive parts for the hybrid-inverter is presented, and control of capacitor voltage is also discussed. The analysis and simulation results show that the proposed strategy is able to delay the starting point of FW region and improve the power/torque capacity of the system. The proposed strategy is suitable for the high-speed operation of open winding PMSM.