A Novel Controller Design For Active Power Filter With Low Switching Loss

Active power filter is an effective means of power quality management. Because of its good dynamic compensation performance and operating stability, it has great advantages on power quality management.This paper first describes the sources, hazards and control measures of power system harmonics, and analyzes the development, basic principles, fundamental structure, major harmonic detection methods and control strategies of active power filter.This paper focuses on hysteresis control method and harmonic detection method based on instantaneous reactive power theory. The instantaneous reactive power theory of harmonic detection methods and the effects on harmonic compensation results caused by its time delay are discussed. And a new method is proposed to significantly reduce the delay time of harmonic detection. The relationship between hysteresis width, switching frequency and switching losses of hysteresis control is analyzed, and a new hysteresis control which adjusting hysteresis bands of each phase is used to reduce switching losses.This paper designs an active power filter control system with dual 2812DSP signal processor as its core, and analyses the design process of the main module controller's hardware, containing the phase-locked loop module, conditioning circuit module, A-D conversion module, double port RAM module and fault detection circuit module. Based on the designed hardware circuit, the Analog to Digital Conversion program, the harmonic detection program and hysteretic control procedures are designed, and the time it takes to run the program is analyzed.Finally, this paper makes some simulations about the traditional fixed hysteresis width, the phase transition hysteresis width and digital phase transition hysteresis width control methods. The results show that the loss of the method involving the phase transition hysteresis width is less than that of the traditional fixed hysteresis width under the premise of little change in the control accuracy. It also turns out that the switching frequency and switching losses of the control method referring digital phase transition hysteresis width are almost the same as those of the one referring analogous phase transition hysteresis width, equally effective in reducing the switching losses. Therefore, the low-loss active power filter controller designed in this paper is proved to be effective.