A Study On New Detection And Control Approaches Of Distortion Currents For Active Power Filters

The detection and control methods of distortion currents for active power filters are key factors affecting not only the compensation performance of APF, but also the extension application. This thesis studies new detection and control approaches of distortion currents for active power filters to satisfy the diverse requirements for APF to apply in the modern power system.In this thesis, firstly, a new distortion current detection theory and approach based on the least compensation current (LCC) is presented, and an APF using the new LCC detection method is investigated. Two schemes to realize the new detection approach and according APF are accomplished and verified. (1) The LCC detection method using a feed-forward multilayer ANN to realize the adjustment of LCC. (2) The LCC detection method using analog hardware circuits to realize the adjustment of LCC. The APFs using according detection method are investigated and developed by simulating and experimenting to demonstrate the performance of the proposed detection method and APF. Secondly, a nonlinear, large signal control theory-one cycle control, which was presented in the 90's and suitable especially for switch power converter,was investigated. The integration reset control and extension applications,which was developed based on one cycle control theory, was emphatically studied. Based on them, in this thesis, the one cycle control theory was successfully applied to the detection and control of APF for the first time. An APF using a novel unified constant-frequency integration control method was presented. The method employs an integrator with reset as its core component to achieve the detection and control of distortion current for APF at the same time. The control equation for APF power switches was derived, and the steady state model of APF power stage was set up. The mathematical model of the APF with proposed control method was found, and the according circuit was constituted. Design example is given using a two-level ac-dc boost topology. A prototype of 500W was developed to demonstrate the performance of the APF with new control method. All findings are supported by experiments and simulation.Finally, the control method is generalized to control a family of converters that are suitable for APF applications. Especially a DC-APF was found that resembles PFC in function but needs lower processing power and has higher efficiency.