Research On Multi-Objective Optimal Predictive Control Strategy For Three-phase Four-wire Active Power Filter

Harmonic suppression plays an key role in improving power quality and ensuring the safe and stable operation of power supply equipment.Reactive power is not only very important to the power supply system,but also has an indelible value for the normal operation of the load.With the rapid development of power semiconductor switching devices,numerous nonlinear loads emerge in the power system,the resulting harmonic pollution and reactive power problems become increasingly serious.In such a premise,the active power filter,which can suppress the harmonics and compensate the reactive power,is favored by the domestic and foreign scholars.The main circuit topology of active power filter is the most basic part of the system.From this point of view,this paper discusses the structural features and basic principles of each main circuit.The harmonic detection methods commonly used in active power filters are briefly introduced,and their advantages and disadvantages are compared.The improved ip-iq method based on instantaneous reactive power is highlighted in this paper.Aiming at the problem of poor tracking dynamic performance of harmonic signal and single control target in the traditional current control strategy,a predictive control strategy of multi-objective optimization model is proposed in the three-phase four-wire asymmetric load system.Firstly,the discrete mathematical model of four-arm active power filter(FAPF)based on the ??? coordinate system is established to realize natural decoupling control.Secondly,two-step prediction of the predicted current is performed to compensate for the delay effect.Set the current tracking bias and switching frequency as the objective function,quantify the control objectives and pre-assess the control state of the switch effect.Thirdly,the switching state of the converter is determined by the evaluation results and the PWM modulation is omitted.The influence of sampling frequency and weight coefficient on switching frequency and current distortion is discussed.Finally,the simulation results show that the proposed strategy harmonic current has good tracking performance and can effectively reduce the switching frequency.