Research On Control Strategy For Three-phase Three-Wire Active Power Filter

With the development of the intelligent and modern power grid.More and more electrical equipment with low power factor,nonlinear and unbalanced characteristics are connected to the power grid,which make the problems such as transient impact,high harmonic and three-phase unbalance become more and more serious.Therefore,it is necessary to manage the power quality effectively.Active power filter(APF)is an effective equipment for improving the quality of electric power with fast dynamic response,high compensation precision and not easy resonance which has aroused extensive concern.This paper has studied the key technologies of the harmonic current detection method,the current loop control strategy and DC side voltage control strategy.Fast and accurate detection of harmonic current is the guarantee to ensure the fantasic compensation performance of APF.Based on the summarize of the traditional FBD harmonic algorithm,This paper pointing out the internal relationship between FBD algorithm and instantaneous reactive power theory.Through analysis the deficiency of traditional FBD algorithm,an improved FBD detection algorithm is proposed,This method utilizes the generalized integrator to extract the positive sequence fundamental voltage components,and the moving average filter is used to replace the traditional low pass filter.This method not only can improve the execution speed and detection accuracy but also reduce the detection delay.The simulation results confirm that this improved method is effective.The current loop compensation of active power filter requires that the compensation current can track the command current signal quickly and accurately,an improved repetitive control method based on general internal model is proposed for pk±1 harmonics,which can selectively suppress the harmonics according to the state of the load.Traditional PI control is difficult to realize steady-state error track,the parallel PI compound control strategy is used to realize the tracking of the command current.The deadbeat control depends on the accurate modeling of the system,the deadbeat control combine with repetitive control are utilized to realize precise control of current loop.The simulation verified the rationality and feasibility of two methods.The magnitude of the DC link voltage has an effect on the compensative ability of APF,a voltage follower is proposed to change the voltage of the DC side with the fluctuation of the voltage change,so as to improve the compensation performance of APF.This paper constructed three-phase three-wire APF experiment platform,the effectiveness of the proposed control strategies based on the universal internal are verified by experiments.