Research On Model Self-correction Fixed Frequency Direct Power Control Strategy Of Active Power Filter

Finite control set model predictive direct power control(FCS-MP-DPC)is widely used in motor speed control systems,grid-connected inverters and many other occasions due to its simple control structure and superior dynamic performance.In this paper,FCS-MP-DPC is applied to two-level three-bridge shunt active power filter(APF),and the defects of traditional FCS-MP-DPC are studied.This paper aims to solve the problems of traditional finite control set model predictive direct power control(FCS-MP-DPC)with large tracking error,high sampling frequency,unfixed switching frequency and strong dependence on the model.It mainly studies the control algorithm principle,control delay compensation,tracking error generation mechanism,fixed frequency control strategy,model parameter mismatch,and self-correcting control strategy,etc.The specific work is as follows:Firstly,starting from the basic principles of APF model prediction direct power control,the mathematical model of FCS-MP-DPC is established,the selection method of value function and the estimation method of related variables are analyzed,and the realization process is given.Aiming at the control delay introduced by the data sampling and program execution in the APF system,the mechanism of its influence on the compensation performance of the system was analyzed,and a delay compensation method of one beat ahead was selected,and its effectiveness was verified by theory and simulation.Aiming at the problem of large tracking error of FCS-MP-DPC,the mechanism of tracking error generation is discussed,and a model predictive direct power control with fixed switching frequency(FSF-MP-DPC)was proposed.This control strategy achieves precise control by reasonably allocating multiple vectors in one control cycle,which not only greatly improves the control accuracy of the system,but also fixes the switching frequency and reduces the sampling frequency.By comparing the control performance of FCS-MP-DPC and FSF-MP-DPC,the feasibility of the proposed control strategy is verified.Aiming at the problem that FCS-MP-DPC is greatly affected by model parameters,the mechanism of prediction error generation is discussed.Starting from the characteristics of inductor materials,the sensitivity of predictive power control algorithms to different line parameter deviations is studied.Through the analysis,it is found that the resistance parameter mismatch has little effect on the compensation effect of APF;the inductance parameter mismatch will have a serious impact on the compensation effect of APF,especially when the model value overestimates the actual value,the impact on the compensation effect is less significant when it is underestimated.In this paper,a model self-correcting fixed-frequency direct power control algorithm was proposed.This control strategy modifies the power prediction model in real time in the form of prediction deviation increment,which solves the problem of prediction deviation caused by parameter mismatch and improves the robustness of APF system.The effectiveness of the proposed control strategy is verified by simulation.Finally,based on the two-level APF experimental platform,the model selfcorrecting fixed-frequency direct power control algorithm is experimentally verified.The experimental results show that the proposed control strategy can achieve fixedfrequency control of active power filters at lower sampling frequencies;it can effectively reduce the tracking error,improve the control accuracy,improve the compensation performance of APF;it can overcome the influence caused by the mismatch of model parameters and improve the robustness of the system.There are 93 figures,6 tables and 93 references in this thesis.