PERFORMANCE IMPROVEMENT OF LOW AND MEDIUM SPEED OPERATION OF PMSM DRIVES

Abstract

Abstract The Inverter's Dead Time along with the inverter nonlinearities referred to in this thesis as the inverter non-idealities are known to produce distorted output voltage. This results into unacceptable performance for inverter driven motors at medium and low speeds. This thesis will first carry out a detailed survey of the inverter non-idealities effects, analysis and mitigation techniques previously discussed in the literature. The thesis will then focus mainly on studying the inverter non-ideality effects on sensor and sensorless permanent magnet synchronous motor (PMSM) closed loop drives. As it will be shown in this thesis, the PMSM with speed sensor is affected in a different manner by the inverter non-idealities than the induction machine (IM). This fact resulted into proposing a new simple and effective solution tailored especially to deal with the PMSM field oriented drive with speed sensor. The solution is based on high bandwidth current controller design with both strong regulation and tracking performance. The proposed solution is verified analytically and experimentally to show its effectiveness The thesis also addresses the analysis of sensorless PMSM drives behavior under distorted output voltage resulting from the inverter non-idealities. A new algorithm is proposed based on adapting a feedforward compensation voltage to mitigate the sixth harmonic feedback in the voltage and hence reduce the inverter's non-ideal behavior even at low speeds. The technique relies on mathematical analysis and linear control design unlike many proposed techniques in the literature that relies on empirically tuned controllers. The technique is investigated experimentally on a sensorless sliding mode based PMSM drive and is compared to other well-known techniques in the literature. Index Terms—Dead Time, inverter non-idealities, permanent magnet synchronous motor, sensorless control, Sliding mode observer, sixth harmonic feedback