Research On Control And Fault Tolerant Controllability Of Nine-Phase Flux-Switching Permanent Magnet Machine

With the development of motor control theory, power electronic and microelectronic technique, multiphase motor drive system has been a promising form for increasing the power level and ensuring high-reliability, when compared with traditional three-phase drive system. Hence, motors with higher number of phases are widely applied for high power applications in ship propulsion, aerospace and electric vehicles. In this thesis, a nine-phase flux-switching permanent magnet motor drive system is deeply and systematically investigated, including motor features, PWM-based vector control strategies, multiphase multi-level technology, model predictive control, harmonic-current-injection based fault-tolerant control and active phase-deficient control, providing theoretical guidance and practical value in the multiphase drive system.The fruits of this thesis are as follows:1. The basic work principle, static performance, and the mechanism of harmonic magnetic-motive force are introduced. With the vector space decomposition concept, the fully-decoupled mathematical model is completely built according to the phase variable model of the nine-phase FSPM motor.2. Advanced control strategies based on stator-flux-oriented control for nine-phase FSPM motor are proposed, including hysteresis PWM based vector control, space vector PWM based vector control and duty-direct-solution based vector control, both simulation and experimental results are conducted to validate these studies. By comparison, the strategy with closed-loop harmonic current control shows better performance in the unbalanced load and nonlinear condition. In addition, two kinds of carrier-based PWM methods are analyzed in the control of a nine-phase FSPM motor supplied by a three-level NPC inverter.3. To overcome the limited bandwidth and difficulty to tune eight proportional-integrals (Pis) well for optimum response to every dynamic scenario, a finite-control-set model predictive current control used for the nine-phase FSPM motor drive system is proposed. The fist objective is comprehensive and detailed description of precise modeling of the nine-phase FSPM motor, where the cross-effect of the d-q quantities is considered; the second objective is the attempt to reduce the computational burden in the MPC algorithm. The third objective is to investigate the impact of the variation of electrical parameter on the drive performance. Both simulation and experimental results are presented to validate the effectiveness of the robustness and high dynamic performance of the nine-phase FSPM motor drive.4. Investigations of open-circuit fault condition for vector-controlled nine-phase FSPM motor with single and three neutral points are done. In order to achieve the invariant in the torque-producing current and minimum stator copper loss, three approaches to fault-tolerant control based on harmonic current injection are proposed to achieve the disturbance-free operation. The fault-tolerant currents can be online calculated by deducing the third, the fifth and seventh harmonic currents in the copper loss optimization process. For the three neutral points topology, post-fault operations with non-control (dual three-phase) and fault-tolerant control are investigated, comparisons are conducted in the torque pulsation and copper loss. Based on the harmonic-current-injection-based fault tolerant control, the post-fault operations for the nine-phase FSPM motor under severe five open-phase fault are presented. The effect of the reconstructed harmonic current components on the machine phase currents is investigated, and the machine drive derating is theoretically quantified.5. Based on the operation efficiency, losses in the nine-phase FSPM motor drive system are investigated under various active phase-deficient operations. Then, an active phase-deficient control is proposed to enhance the operation efficiency at light load. Both simulation and experimental results are presented, verifying the proposed control strategy.6. Based on the real-time dSPACE1005, a digital drive and control experimental platform of nine-phase FSPM motor drive system is built. Experimental results verify the effectiveness of the proposed control algorithms, providing theoretical and technical basis for further study in the multiphase FSPM motor drive system.