Design And Research Of Control System In Three Phase Shunt Active Power Filter

With the rapid development of the Power electronics, kinds of power electronic equipments have been widely used in power grid nowadays, With the increasing of nonlinear loads in power system, serious harmonic current pollution has threaten the running of power system and affected the use of electrical equipments. Active power filter (APF) has been the main method to solve harmonic pollution in power system and to improve the power quality because of its good compensation performance.Firstly, the thesis introduces the concept of harmonic, the harm of harmonic and the method for harnessing harmonic. And then, the thesis introduces the characteristics, development and future prospect of APF. Classifies of APF, shunt APF's structure and operating principle are introduced.Real-time, accuracy in harmonic current detection are critical to the compensation performance of the active power filter. This thesis introduces the p-q method and ip-iq method based on the instantaneous reactive power theory and makes performance research on ip-iq method, do some improvements to the method. A sliding-window LPF is applied in the computation to detect the harmonic which improves the real-time, tracing performances with less computation. The results of the simulation proves it. In addition, the FBD algorithm based on Fryze's power theory for the three phase harmonic current detection is analyzed. Based on the research of the FBD algorithm process, the reason of the delay error and the mathematical model of theoretical evaluation is given in this thesis, and then does some improvement that can improve the the dynamic performance and reduce computation. According to time delay problem of APF system that is less studied, through the establishment of simple delay model APF system, this thesis makes the corresponding analysis.The thesis analyzes the current control and voltage control strategy of active power filter and uses fuzzy adaptive PI control strategy in DC side voltage control. Finally, grid connection problem is analysed and two solutions are proposed to suppress the large inrush current. The simulation proves the validation of the solutions.In order to verify the correctness of the harmonic detection methods and control strategies, this thesis structures the three phases and three wires shunt APF system in MATLAB/Simulink, and does comparative analysis by simulation for the proposed harmonic detection methods and control strategies.Finally, on the base of the theoretical analysis and simulated research, the harmonic detection hardware circuit is designed in this thesis, the software scheme of shunt active power filter system based on DSP-TMS320F2812 has been designed, software's structure and function are described in detail. The digital LPF design method based on TI Filter library is given.