Design And Study On Shunt Hybrid Active Power Filter

In recent years, as users have higher and higher requirement of power quality, harmonic is more and more attention. The existence of harmonic, not only polluted grid power quality, but also become the biggest obstacle of the development of power electronic technology. Because hybrid active power filter(HAPF) which colligates advantages of passive filter and active power filter can change combination mode of passive filter(PF) and active power filter(APF) according to requirements of different occasions, and has some characteristics of flexible structure, good dynamic performance, so it has attracted enough concern. Based on two-level three-leg shunt HAPF, the thesis researched parameters design of main circuit, modulation algorithm of converter, method of dead-time compensation, control strategy of current loop.In the thesis, the characteristics of HAPF topology were summarized, mathematical models were established, and the influence of different LC filter parameters on each cuttent of system was analyzed. According to the characteristics of system harmonic source and different parameters of LC filter, the thesis used vector trajectory method to analyze DC voltage of HAPF. According to theoretical analysis, the proper parameters of main circuit were designed which comprehensively considered DC voltage of system in order to reduce compensation capacity of converter.Modulation process of traditional Space vector pulse width modulation need to tranform coordinate, judge sector, calculate effect time of voltage vector and switching state of each leg. The process is very complicated, and calculation of controller is too much. Based on traditional SVPWM, the thesis which combined with classification algorithm derived simplified algorithm of PWM. The simplified algorithm directly judged the sector in which reference voltage was located and got devices switching state. The simplified algorithm greatly decreased calculation and was digital realized easily. Meanwhile, the influence of dead-time on output voltage of converter was analyzed. A dead-time compensation method based on pulse-tuning which adjusted switching time of each leg was used to inhibit harmful influence of dead-time effects. The simulation proved that simplified algorithm of PWM and dead-time compensation method are effective.Because command current of HAPF is various of frequency sine signals, so the thesis used an improved proportional resonant(PR) controller to track command current without any error. On the basis of analyzing the effects of PR controller parameters on the control performance, the debugging methods of PR controller was summarized. Combined with the mathematical models of HAPF, open-loop transfer function of control system was got. The thesis used frequency characteristic analysis to discuss filterring characteristics of HAPF based on improved PR control. The simulation proved that HAPF has good filterring performance on basis of PR control. According to the particularity of HAPF topology, the thesis researched the influence of two methods which were current loop controlling DC voltage and diode rectifier circuit controlling DC voltage on system. The thesis contrasted the characteristics of HAPF each current on different simulation models. Combined with the demand of HAPF system, the proper method of controlling DC voltage was selected.Based on two-level three-leg SHAPF ecperimental platform, the thesis verified research content. The experimental results proved that the simplified algorithm of PWM, dead-time compensation method, improved PR control strategy are correct and parameters design of LC filter are effective. HAPF has good filterring performance.