Research On Direct Torque Model Predictive Control Of Permanent Magnet Synchronous In-wheel Motor For Electric Vehicle

Due to the oil crisis and environmental pollution,electric vehicles have become one of the main directions for the future development of automobiles.Permanent magnet synchronous in-wheel motors have been widely used in electric vehicles due to their small size,light weight,high power density,and wide speed range.The electric vehicle controller calculates the driving torque based on the information such as driver demand and road driving conditions.This torque command is transmitted to the permanent magnet synchronous in-wheel motor drive system.Therefore,the control objective of the permanent magnet synchronous in-wheel motor drive system is to quickly and accurately track the torque commands issued by the vehicle controller while ensuring economical efficiency.Compared with the field oriented control,the direct torque control abandons the decoupling idea and eliminates the rotation coordinate transformation.The dynamic response speed is fast.Therefore,this paper selects the direct torque control method.At the same time,a direct torque model predictive control scheme for permanent magnet synchronous motor based on switch combination optimization of three-phase inverter is designed for the problem of large torque ripple and switching loss in the direct torque control system.In order to solve the control delay problem of switch selection,the model predictive control method is used to select the optimal switch at the current moment according to the current state of the prediction.At the same time,this paper designs an objective function to replace the hysteresis comparator,sector judgment,switch selection table and other modules to select the optimal switch combination.This can avoid the torque fluctuation problem caused by the hysteresis comparator.In addition,the switching signal acts directly on the three-phase inverter.The control of the motor usually just models the motor.This will ignore the role of the three-phase inverter.In fact,the inverter is also a key component.Therefore,this paper designs a switch combination optimization control method to select the optimal switching signal combination for the inverter.The three-phase inverter and the permanent magnet synchronous motor are integrally modeled to calculate the predicted torque and flux linkage.Finally,a permanent magnet synchronous motor control system model is built in Matlab/Simulink.The off-line simulation comparison test is performed under different conditions to verify the effectiveness of the direct torque model predictive control algorithm.The main content and innovation:1.In order to better control the permanent magnet synchronous motor,a switch combination optimization method is designed to select the optimal switch combination.This method is designed from the perspective of voltage vector tracking control of a three-phase inverter.At the same time,the permanent magnet synchronous motor and the three-phase inverter are modeled as a whole.This will make the prediction model more complete.2.Taking the switching signal of the three-phase inverter as the connection point,a direct torque model predictive control system based on switch combination optimization for permanent magnet synchronous motor is designed.This method combines the advantages of fast response speed in direct torque control and multi-objective optimization in model predictive control.This method avoids the problem of upper and lower limit pulsation about torque and flux of the hysteresis comparator.This method also solves the control delay problem of switch selection in the traditional direct torque control.The control structure is simple and easy to implement.