Research On Compound Repetitive Control Strategy For Active Power Filter

In the terminal power consumption,more than 50%of power is used by power electronic transform devices.Due to the nonlinear features of power electronic devices,these devices can meet the different needs of power transform,but they can also cause serious harmonic pollution,which leads to poor power quality of power grid.Low-voltage active power filter(APF)has many advantages,such as good filtering performance,strong adaptability to the power grid,small volume and so on.It has been widely used in low-voltage power grid.This paper focused on the compound repetitive control strategy of three-phase four-wire low-voltage active power filter.Aiming at the circuit topology of three-phase four-wire active power filter that combined by three single-phase,we analyzed the working principle of the circuit,established the mathematical model of APF,and gived the design method of circuit parameters.Harmonic current detection is the basis of active power filter,for three-phase four-wire circuit topology,this paper used single-phase harmonic current detection method based on digital phase shifting 90°,which is an independent,high precision and real-time harmonic current detection method of three-phase loads.Control strategy plays an important role in the compensation performance of active power filter.Through comparison and analysis,this paper used repetitive control strategy which has a good steady-state performance,described its basic principle,implementation and control parameters design method.In order to improve the dynamic response speed of repetitive control,we can combine repetitive control with deadbeat control to form a compound repetitive controller.According to the characteristics of odd h armonics in power system,this paper proposed the odd-harmonic repetitive controller which can only eliminate odd harmonics.In this way,the response speed of control system is further improved.A simulation model of APF is established in PSIM simulation environment to verify the effectiveness of the harmonic current detection and the compound repetitive control strategy.We built a 380V/100A three-phase four wire active power filter experimental platform,compiled the DSP control program and ’carried out the comparative experiment.The experimental results showed that the compound repetitive control strategy has a good steady-state compensation effect,and the odd-harmonic compound repetitive control strategy has a faster dynamic response speed.