Research On Model Predictive Control And Fault-tolerant Control Of Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor(PMSM)is characterized by high efficiency,high torque inertia ratio,high power density and simplicity.Therefore,it has been widely applied in various fields such as radar,computer numerical control machine tools,electric steering gear,locomotives,and robots.At present,the VSI(Voltage Source Inverter)of a drive motor control system mainly includes a two-level inverter and a three-level NPC inverter.Compared with traditional two-level inverter,the three-level NPC inverter has the characteristics of less power tube withstand voltage stress and electromagnetic interference,lower voltage total harmonic distortion and switching losses.However,the number of switching devices in a three-level NPC inverter is increase,which will lead to decrease in the reliability of the inverter.A short or open circuit fault of the bridge arm of the three-level NPC inverter may lead to no working of motor control system,and even it may affect the operational safety of the entire system and cause incalculable economic losses.In some high performance AC control systems,the three-level NPC inverter is the weak link in control system.Therefore,in order to improve the reliability of the control system,the fault-tolerant control of the three-level NPC inverter in PMSM system is of great significance.After years of research,different the topology of fault-tolerant structures of the three-level NPC inverter has been proposed.The scheme,Three-Phase Eight-Switch Inverter(TPESI)will be applied as the topology of fault-tolerant control for three-level NPC inverter,which has the merits of simple structure,low cost and strong load capacity.Two of most widespread control methods for high-performance PMSM systems are FOC(Field Oriental Control)and DTC(Direct Torque Control).FCS-MPC(Finite Control Set Model Predictive Control)is an optimization control method in recent years.It has received significant attention by some domestic and foreign Scholars.Compared with FOC and DTC strategies,FCS-MPC can increase the dynamic performance of the drive system,that can effectively reduce the system's electromagnetic torque ripple and THD(Total Harmonic Distortion)value of stator currents,and It has strong ability to cope with system constraints.Therefore,this thesis adopts FCS-MPC strategies to control PMSM system driven by the three-phase eight-point fault-tolerant inverter.The main research content of this thesis are listed as follows:(1)Firstly,the mathematical models of three-phase eight-switch inverter and Permanent Magnet Synchronous Motor(PMSM)are established by the operating mode of a driving system and analysis of causes of voltage unbalance in DC side bus capacitors.Secondly,an ESO(Extended State Observer)based on the inverse hyperbolic sine function is designed to reduce the calculation of back-EMF.An ESO based MPCC(Model Prediction Current Control)strategy is proposed for PMSM system driven by TPESFTI(Three-Phase Eight-switch FaultTolerant Inverter).(2)Considering the large computational complexity and complexity of the traditional FCS-MPC strategy,a novel Finite Control Set Model Predictive Control(FCS-MPC)strategy with fast vector selection is proposed for the drive PMSM system based on Three-Phase Eight-Switch Fault-Tolerant Inverter(TPESFTI).In the meanwhile,an adaptive sliding mode speed controller with ESO is designed,which is improve the dynamic performance and robustness of the control system.And so as to realize speed sensorless control of the drive PMSM system,a speed ESO with the inverse hyperbolic sine function is constructed.(3)In order to solve the chattering phenomenon of traditional sliding mode control,the fractional-order sliding-mode observer is designed based on the advantages of sliding mode control theory and fractional calculus technique,the stator current and voltage in the dq0 rotating coordinate system are used as input signals.In the meanwhile,It provides rapid and accurate real-time observation of the back-EMF and speed of the PMSM system.(4)Based on three-phase eight-switch inverter,an observer of speed,torque and flux observer in the ??0 two-phase stationary coordinate system is proposed for the Permanent Magnet Synchronous Motor(PMSM)drive system with fractional-order sliding-mode observer.At the same time considering,the unbalanced voltage in the model predictive torque control,it is sufficient to create an optimal minimum performance objective function.