Research On Predictive Control Of Dual PWM Converter Based On Power Feedforward Compensation

Due to the advantages of stable DC bus voltage,low current harmonic,unit power factor operation,and bidirectional energy flow,the dual PWM converter has been widely used in low-power AC speed regulation systems.In the control of dual PWM converters,the voltage control of the rectifier side mostly uses a cascade structure based on a PI controller.The dynamics and robustness of the system are greatly affected by the parameters,which are prone to problems such as poor dynamic performance and overshoot.The use of electrolytic capacitors on the DC side increases the size and cost of the system,reduces the safety and reliability of the system.In order to improve the performance of the DC side voltage and the power density of the dual PWM converter,this paper takes the permanent magnet synchronous motor as the controlled object and makes an in-depth study on the control strategy of the dual PWM converter.The continuous mathematical model and discrete mathematical model of PWM rectifier are established,the cost function with power deviation as the core is constructed,and the Model Predictive Direct Power Control(MDPC)of PWM rectifier is realized.In view of the shortcomings of the MDPC voltage loop PI controller,this paper designs a Cascade-Free Model Predictive Direct Power Control(CFMDPC)suitable for three-phase two-level voltage rectifier PWM rectifier.Adopt the dynamic given scheme to realize DC side voltage tracking,through the energy flow model,the active power reference value including static and dynamic components is constructed,and the cost function with power and voltage as inputs is constructed,which improves the dynamic performance of the system.In order to further improve the control performance and reduce the impact of sampling and calculation delay,delay compensation control is adopted to improve the prediction accuracy of power.Aiming at the problem of the dual PWM converter independently controls that poor DC dynamics and robustness when the load is disturbed,a load estimation model for permanent magnet synchronous motors based on Deadbeat Current Predictive Control is established,feed-forward the load to the rectifier side to reduce the fluctuation of the DC bus voltage when the load changes suddenly,so as to achieve the purpose of improving the robustness and dynamics of the DC side voltage.The CFMDPC strategy and dual PWM feed-forward strategy of the PWM converter mentioned in this paper are simulated and experimentally verified.The results show that,compared with the MDPC control strategy,the CFMDPC control strategy adopted in this paper improves the dynamic performance and robustness of the DC side voltage;compared with independent control,feed-forward control can improve the dynamics of the DC bus voltage and reduce voltage fluctuations when the load speed and torque change suddenly.