Research On Harmonic Current Detecting And Controlling Of Shunt APF

The wider use of non-linear load and power electronic devices make the power system harmonic and reactive current pollution serious. Therefore, the suppression of harmful current and improve power quality become an important task in the field of power systems. The active power filter (APF) is a new type of power electronic devices for dynamic harmonic suppression and reactive power compensation. Its advantages are respond quickly, can achieve dynamic compensation and the effects are good, so it has a broad prospects for development.In this paper, based on the active power filter circuit topology, working principles and working characteristics are analyzed, and the research emphasis two key techniques:current detection and tracking control.In the aspect of current detection, it has conducted an in-depth comparative study in symmetric and asymmetric three-phase voltage system with two current detecting methods, which are ip-iq method based on three-phase instantaneous reactive power theory and method based on the active current separation. The simulation results show that, the method based on the active current separation not need for complex matrix transformations, compared with the ip-iq method, decreases the computing amount, simplifies circuits, detects accurately in symmetric and asymmetric three-phase voltage, and extends single-phase system detection. In this paper, the method based on the active current separation is chosen, which considered to system precision, and detection system is designed. Optimum parameters are obtained by the optimized low-pass filter link in the system.In the aspect of tracking control, in this paper, a recursive integral PI controller has been designed, and better results are obtained. In order to solve the difficulty in tuning PI parameters, a fuzzy recursive integral PI control method has been used. According to the characteristics of the system, design the fuzzy inference rules, online adjustment of PI parameters was achieved. Simulation studies show that the control strategy can improve dynamic and static tracking performance of the APF system.Finally, an APF simulation model was built, the simulation results show that the design of the APF in this paper can effectively inhibit harmonic and compensate reactive power. In addition, the simulation algorithms can be directly used to achieve digital signal processor, laying a good foundation for further use of DSP digital control.