Four-switch inverter fed PMSM DTC with SVM approach for fault tolerant operation

In this paper, the direct torque control (DTC) scheme of a four-switch inverter fed Permanent magnet synchronous motor (PMSM) is discussed by analyzing the voltage vectors to obtain an inverter fault tolerant drive system. A symmetric space vector modulation (SVM) approach is introduced to the DTC system for the purpose of improving the static performance. Calculation of the desired voltage vector in the PMSM drive system is analyzed, an optimal voltage vector sequence and timing plan for SVM is designed to synthesize the desired voltage vector and to compensate the remaining time in each sampling period effectively. Simulation and experimental results verify that the four-switch inverter fed PMSM system is able to operate steadily under the classic DTC scheme, and with significantly improved steady state performance under the proposed SVM-DTC approach.