Research On Predictive Control Strategy Of Three Phase Four Switch For PMSM

Permanent magnet synchronous motor(PMSM)has attracted more and more attention because of its close structure and high power density.In the mean time,with the improvement of the computing power of the processor,the predictive control algorithm has attracted more and more attention,and researchers have been paying attention to the reliability of inverters.In this context,the application of predictive control for permanent magnet synchronous motor(PMSM)speed control system fed by four-switch three-phase inventer(FSTPI)is studied in this paper.Improvements to the traditional predictive control algorithm of FSTPI are mainly proposed in this paper.Aiming at the inherent problem of imbalance of capacitor midpoint voltage in the FSTPI,a voltage term to the cost function needs to be added in the traditional model predictive control(MPC)algorithm to control it,which inevitably leads to the need to adjust the weight coefficient of the voltage term.An improved prediction algorithm without weight coefficients is proposed in this paper for this problem.Reference values of d and q axis currents of the motor can be recalculated and adjusted by adding the appropriate DC component.In this way,the setting of the weight coefficient of the voltage term in the cost function can be omitted.The small number of finite sets of model predictive control for traditional single vector leads to poor control performance,and the multi-vector control is relatively complicated in the calculation process.Pulse sequence predictive control is proposed in this paper to solve the problem.Different constructed pulse sequences are optimized and the calculation method of current pulse width is given in this method.In this way,the midpoint voltage is controlled and the control quality of the system is also improved.Aiming at the problem that MPC depends on the accuracy of model parameters,a predictive control method with error feedback self-correction is proposed this paper.Through the analysis of the prediction error caused by the model mismatch,the prediction error at the current time and the error caused by different output voltages are used to calculate the prediction error at the next time.The impact of model mismatch is reduced by adding the calculated error back to the current prediction stage.At last,the MATLAB simulation software and the permanent magnet synchronous motor in the experiment center are used to verify the algorithm proposed in this paper.Through experiments’ results,it is verified that the improved algorithm proposed in this paper can well meet the operation requirements and can effectively control the midpoint voltage of the capacitor;At the same time,the prediction error caused by model mismatch also can be reduced by error feedback self-correction algorithm.The control effect of the system is improved.