Research On Optimization Of Model Predictive Control Strategy For Three-phase PWM Rectifier

Traditional Finite Control Set Model Predictive Control(FCS-MPC)is a nonlinear predictive control strategy,which has the advantages of intuitive modeling,simple control constraints and wide application range.It has become a research hotspot in the field of converter predictive control.At the same time,the traditional FCS-MPC also has some shortcomings,such as large operation amount in its optimization process and large output current harmonics.Therefore,this paper takes three-phase two-level voltage-type PWM rectifier circuit as the research object,builds a system simulation and experiment platform on the basis of studying its working principle and mathematical model,and conducts the following optimization research on the existing problems of traditional FCS-MPC:1)Aiming at the problem of large computation in the traditional FCS-MPC optimization process,this paper proposes an Optimized Single-vector Model Predictive Control(OPT SMPC),which simplifies the 8-vector traversal optimization process of FCS-MPC by the sector optimization method.First,the working principle and theoretical derivation process of OPT SMPC are described in detail.And then,the simulation and experimental verification are carried out.The results show that compared with the traditional FCS-MPC,the operation amount of OPT SMPC is reduced by 75%,while the system control effect is basically unchanged.2)In view of the traditional FCS-MPC control system problem of large current harmonic,this paper puts forward Optimized Double-vector Model Predictive Control(OPT DMPC),Conbined-vector Model Predictive ControlⅠ(CMB MPC1),Conbined-vector Model Predictive ControlⅡ(CMB MPC2)and Conbined-vector Model Predictive Control Ⅲ(CMB MPC3)of four kinds of optimized control strategy.(1)Aiming at the limitation of only single-vector output in each control period of FCS-MPC,which leads to large system current harmonics,this paper proposes an Optimized Double-vector Model Predictive Control strategy which combines dual voltage vectors in the control period,and effectively reduces the current harmonics.First,the working principle and theoretical derivation process of OPT DMPC are described in detail.And then,the simulation and experimental verification are carried out.The results turn out that compared with the system harmonics and computation under the traditional FCS-MPC control,the system current harmonics under the OPT DMPC control are reduced by 0.9%,and the computation is decreased by 69%.(2)To simplify the control algorithm of double-vector combination control,this paper innovatively replace vector combination with conbined-vector,and then put forward CMB MPC1,which could reduce computational complexity to some extent and maintain the OPT DMPC control effect.First,the equivalence between conbined-vector method and double-vector combination method is verified.And then,the same control effect is verified by simulation and experiment.Finally,the calculation amount of CMB MPC1 is measured to be 13% lower than that of OPT DMPC,which verifies its optimization effect.(3)CMB MPC2 is put forward which further introduces specific conbined-vector including double-vector.In this paper,the working principle of CMB MPC2 and theoretical algorithm deduction are described in detail,and verified by simulation and experiment.It is found that the system current harmonic under CMB MPC2 control is reduced by 2.3% compared with that under the traditional FCS-MPC control,and its computation is also decreased by 72%.(4)In order to minimize the system harmonic current,CMB MPC3 is put forward,which uses multi-voltage vector combination to track the reference value in real time.This paper introduces CMB MPC3 control principle,expounds the various vector selection and the action time of calculation.The simulation and experiment results show that compared with traditional FCS-MPC,CMB MPC3 reduces the operation amount by 28%,and the system current harmonics is decreased by 3.63%,which achieves significant system harmonics optimization.At the end of the paper,a hardware experimental system is built to further verify the proposed optimized control strategy.