Quasi-Z Source Inverter-Permanent Magnet Synchronous Motor Drive System Model Predictive Control

The two-stage control method is usually applied in quasi-Z source inverter-permanent magnet synchronous motor(qZSI-PMSM)drive system,that is,the quasi-Z source inverter and the motor are respectively controlled by two independent controllers.The switch state required by the inverter is then generated by a modulator.In this two-stage control method,the inverter modulation index and the shoot-through duty cycle may conflict during the dynamic adjustment process of system,resulting in control failure and system reliability degradation.Focus on this problem,this paper has carried out related research work.Combining with finite set model predictive control can realize the multiple control target optimization,this paper aim at designing a unified predictive control method for qZSI-PMSM drive system.To this end,the qZSI and PMSM predictive control are studied separately,and the design method of the two predictive controllers is analyzed.Based on the small-signal model and prediction model of qZSI,by using the inductor current as the basis for judging whether the shoot-through vector is the optimal vector,the influence of the qZSI undershoot phenomenon on the finite-set model predictive control of qZSI-PMSM is avoided.This method not only can reduce the computational burden of the controller,but also can ensure that the DC bus voltage amplitude reaches its reference.Since system losses are easily affected by factors such as temperature and motor operating conditions,which are difficult to calculate accurately,this paper proposes a power compensation strategy.By designing the closed loop of capacitor voltage to approximate the system losses,and then the inductor current reference is obtained to complete the design of the predictive controller of the qZSI-PMSM.By selecting the appropriate control variables,the unified predictive control of the qZSI-PMSM system is realized.Experimental researches on two control algorithms have been carried out on a qZSI-PMSM system.The steady-state and dynamic experimental results verify that the finite set model predictive control method proposed in this paper can not only realize the unified control of qZSI-PMSM,but also can ensure that the control performance of both sides meet the control targets.The experimental results of input voltage drop prove that the proposed method can avoid the conflict in the traditional two-stage control.Besides,compared with traditional two-stage control method,the proposed method has quicker response speed and stronger anti-disturbance ability.