Research On Anti-saturation Repetitive Control Strategy Of Shunt Active Power Filter

As the power quality of power grid is becoming more and more widely concerned,Active Power Filter(APF),as an effective power quality integrated management device,can effectively suppress harmonic and compensate reactive power.Compared with the traditional passive compensation device,APF has the characteristics of high compensation accuracy and fast dynamic response.It plays an important role in improving the quality of power grid.For APF,the key factors that affect its performance are: main circuit parameters,harmonic detection and current loop control.Current loop control is widely concerned as one of its key technologies.In current loop control algorithms used in APF,repetitive control has become a research hotspot because of its high precision compensation ability.However,repetitive controller is a method based on internal model principle.It has high gain and low response speed.The phenomenon of output saturation is easy to appear in the case of sudden change of the system operating conditions.Therefore,this paper focuses on the anti saturation strategy of repetitive controller to improve the stability of the system with APF as the research object,and the following work should be completed:Firstly,the basic principle of the three-phase three wire APF is introduced.The equivalent model of the continuous domain in the ABC stationary coordinate system,?? stationary coordinate system and the dq synchronous rotating coordinate system is established by the equivalent circuit model of the APF.In view of the effect of the hysteresis on the performance of the continuous domain model in the digital process.It is concluded that the lagging one beat control will introduce the phase angle lag to the control object.Then,a APF current loop control algorithm based on PI+ repetitive control is designed.Firstly,the basic principle of repetitive control is introduced,then the parameters of the PI controller are designed by indirect design method.Secondly,the parameters of the repetitive controller are designed in the discrete domain and the stability is verified.Then,the active damping method based on the capacitance current feedback is designed to suppress the resonant peak of the LCL filter model.In order to control the performance of the traditional repetitive control under the frequency fluctuation of the power grid,a kind of adaptive repetitive control algorithm for the frequency wide range of the power grid is adopted.Simulation and experimental results show that the current loop control method based on PI+ repetitive control has high harmonic compensation accuracy,the fractional-order repetitive controller designed still have good compensation effect when the grid frequency fluctuates.Finally,aiming at the problem of output saturation of repetitive controller under the condition of sudden change of system operation condition,three different anti saturation strategies are put forward to restrain the influence of saturation phenomenon on system performance.Firstly,the three kinds of anti-windup strategies are designed.and the parameters of the anti-windup compensator are designed.Then,the simulation and experimental verification are carried out under the 2 mutation conditions of the compensation 50% load current and the increase of the grid voltage 10%.The saturation performance of the three different anti saturation strategies is compared by comparing the magnitude of the saturation error signal and the saturation time.It is verified that the effectiveness of applying anti-saturation repetitive control strategies to APF.