Advanced control and pulse-width-modulation techniques for high-speed permanent magnet synchronous machine drives

• Main Author: Dai, Shangjian
• Format: Dissertation
• Language: English
• Published: University of Sheffield 2020

Due to the limited switching frequency of semiconductor switches, high-speed permanent magnet synchronous machine (PMSM) drives which have high fundamental frequency usually feature low switching-to-fundamental frequency ratios (SFRs). The low SFR could deteriorate both the dynamic response and the steady-state performance of high-speed PMSM drives. Therefore, advanced control and optimal pulse width modulation (PWM) methods for high-speed PMSM drives have been investigated in this thesis. Firstly, this thesis proposes a novel deadbeat predictive current control (DBPCC) method for high-speed PMSM drives. The proposed method realises deadbeat control of dq axis currents by tracking the associated stator flux vector in the stationary frame and considers the delay and rotor movement effects explicitly. Consequently, the proposed DBPCC exhibits excellent dynamic response at high speeds even with very low SFRs. Moreover, the influences of parametric mismatch and inverter nonlinearity on the proposed DBPCC are derived analytically and verified both by extensive simulations and experiments. Secondly, three novel methods, i.e. adaptive reference correcting current injection (ARCCI), adaptive harmonic reference correcting current injection (AHRCCI) and transient identification of inductance are proposed to improve the steady-state control accuracy, current harmonic distortion and dynamic response of high-speed PMSM drives with the proposed DBPCC, respectively. By these proposed methods, the near-ideal deadbeat current control of high-speed PMSM drives can be achieved even with inaccurate machine parameters inverter nonlinearity and other non-ideal factors such as back EMF harmonics. Thirdly, synchronous optimal PMW (SOPWM) with minimised current THD is investigated for high-speed PMSM drives. To derive the optimal pulse patterns and evaluate the resultant current THD of SOPWM efficiently, a computationally efficient optimization algorithm and current THD prediction method are proposed. Moreover, to avoid the overshoot current during mode transition, a fast and smooth SOPWM mode transition scheme is developed as well. Finally, this thesis proposes a fast dynamic current control with SOPWM for highspeed PMSM drives. The proposed method can achieve current distortions similar to SOPWM in steady states and fast current response in transients as well.