Sensorless DTSMC of a three-level VSI fed PMSM drive

This study proposes a novel sliding mode control (SMC) structure for a three-level voltage source inverter (VSI). The proposed controller is implemented in discrete time and is applied for the closed-loop speed control of permanent magnet synchronous motor (PMSM) drive powered from a three-level cascaded H-bridge VSI. The proposed discrete time SMC (DTSMC) has the distinct advantages of control over maximum switching frequency and relatively lower total harmonic distortion compared to that of a conventional hysteresis modulation (HM) control. Unlike HM, the proposed DTSMC relates the maximum switching frequency to sampling time, resulting in better utilisation of the bandwidth of the VSI. Additionally, a procedure to combine the DTSMC with a sliding mode observer to achieve sensor-less operation of the PMSM drive is presented. Verification of the proposed DTSMC is conducted using simulation and experimental tests. The simulation and experimental results are presented.