Study On Low Loss Design Method Of Three-phase Four-wire APF

With the electronization of electrical equipment,the problem of harmonic pollution is becoming more and more serious.Active power filter(APF),as an effective means to control harmonic pollution and improve power quality of power network.It has made great progress in recent ten years and has been widely used in medium and low voltage distribution networks.With the determination of the national dual-carbon energy strategy and the vigorous promotion of energy conservation and emission reduction,APF operation efficiency has become an important indicator to measure the APF performance.In this paper,the loss reduction of APF is studied from two aspects of system design and control strategy to reduce the operating loss of APF.On the basis of describing the structure of APF,the main components of APF loss are expounded.The loss models of AC filter reactor,power electronic switching device and DC support capacitor are analyzed and established.The low loss selection method of AC reactor and DC container is given from the design.Based on the working principle of APF,the equation of state mathematical model and control system structure of APF are established.The switching vector and model predictive current control method of three-phase four-arm APF are studied.An improved model predictive voltage control strategy is proposed,which can reduce the workload of model predictive calculation and shorten the time of control calculation.Based on switching loss and switching frequency is appropriate conclusions,combined with model predictive control can realize the characteristics of multi-objective optimization,minimum error objectives on the basis of introducing the current state of switch the least assisted the optimization goal,and studies the reasonable choice of the double target weight coefficient,effectively reduce the switching loss of power electronic device.Based on the characteristics that the switching loss of power electronic devices and the dielectric loss of DC support capacitor are positively correlated with the DC side voltage of APF,and considering the normal deviation of grid voltage,a DC voltage follow up control strategy is studied,in which the DC voltage changes with the deviation of grid voltage.When the grid voltage is low,the DC voltage is correspondently reduced.The power consumption of APF can be further reduced on the premise of ensuring the current performance on the network side.The thermal simulation model of APF is built based on PLECS simulation software,and the simulation results verify the effectiveness of the proposed loss reduction method.Finally,the Rapid Control Prototype experimental platform of three-phase four-bridge APF is built based on RT-BOX real-time emulator.The results show that compared with the traditional model predictive control with single objective and constant DC side voltage,the model predictive control with switching state switching as the auxiliary optimization objective can achieve lower power consumption,and the power consumption of APF can be further reduced by adopting the follow-up control strategy with DC voltage varying with network voltage.