Research On Model Predictive Control For Permanent Magnet Synchronous Motor Systems Fed By Fault-tolerant Inverters

Permanent magnet synchronous motor(PMSM) is known as high power density and high efficiency. Therefore, it has been widely applied in industry, transportation, military, aviation and other important fields. As the common three-phase six-switch VSI(Voltage Source Inverter) is the weak link in motor control system. A short or open circuit fault of VSI may lead to open circuit of motor winding. Then large torque output and big mechanical noise will occur in motor system under such condition. The overall performance of the system is greatly reduced, and even unable to work. Therefore, the fault-tolerant control of VSI in motor drive system is of great significance. After years of research, different fault-tolerant structures of VSI have been proposed. The scheme, that transforming three-phase six-switch VSI to three-phase four-switch VSI after the VSI fault happened, has the merits of low cost and strong load capacity.Two of most widespread control methods for motor system are VC(Vector Control) and DTC(Direct Torque Control). VC is based on stator current control. However, the system response of VC is slow because of the existence of inherent inner current loop. The system response of DTC is fast, but it generates large torque ripple. FCS-MPC(Finite Control Set Model Predictive Control) is an emerging control concept in recent years. It has received significant attention from electrical drive community. FCS-MPC has strong ability to cope with system constraints. The dynamic response of FCS-MPC is faster than that of VC, the torque ripple and THD(Total Harmonic Distortion) value of stator currents in FCS-MPC system are smaller than that in DTC system. Therefore, this thesis adopts FCS-MPC strategy to control PMSM system driven by three-phase four-switch inverter.The main works in this thesis are listed as follows:(1) For the reason that permanent magnet flux linkage is varied with temperature, while the value of permanent magnet flux linkage is one of the important parameters that controllers need. A MRAS(Model Reference Adaptive System) observer is designed to identify permanent magnet flux linkage online. A MRAS observer based model predictive current control(MPCC) strategy is proposed for PMSM system driven by three-phase four-switch inverter.(2) In order to improve the robustness of conventional FCS- MPC strategy, based on sliding mode control method, a finite-control-set model predictive control(FCS-MPC) strategy is proposed for permanent magnet synchronous motor(PMSM) driven by Three-phase four-switch inverter. In the meanwhile, a sliding mode speed regulator is designed, which have no chattering and monotone convergence.(3) An active disturbance rejection controller(ADRC), acting as speed regulator, is designed to realize disturbance estimation and disturbance compensation for the purpose of enhancing system robustness. Compared with PI-based FCS-MPC strategy, the ADRC based one enables PMSM to possess better command-following characteristic and stronger robustness in the presence of load torque variation. In the meanwhile, so as to realize speed sensorless control of PMSM system, a speed ESO(Extended State Obsever) is constructed to realize rapid and accurate speed identification.