Study On DC-Link Voltage Control And Soft Start-up For Active Power Filter

The switch action from nonlinear and time variable electronic device widely used can inject reactive power and harmonic current which can’t be ignored, causing serious power quality problems. As an effective device for reactive power compensation and harmonic suppression, the Active Power Filter (APF) has become research focus of power quality governance at present.At first, the paper introduces the present situation, development trends, classification, basic structure and principle of APF, then harmonic current detecting algorithm, control algorithm, selection of switching device and main circuit parameters of shunt APF are studied; in harmonic detecting portion, p-q and ip-iq harmonic current detecting are detailed and compared. Finally it is the ip-iq harmonic current detecting that is selected. Through the study and analysis of the shunt APF adopting hysteresis control, the functional relationship of mutual restriction among the parameters of main circuit is obtained. The simulation model of shunt APF is built with PSIM. The parameters of DC-link capacitance and inductance on the AC side are determined.The energy exchange between the DC-link and AC-side is discussed. The fluctuation of DC-link voltage in three-phase three-wire shunt APF is analyzed. The simulation model of shunt APF is built with MATLAB. On the basis of conventional PI control method for DC-link voltage, a novel control method is brought forward, which has integrated the fuzzy control with PI control. This method combines the merits of fuzzy control and PI control, which is proved effective through theoretical analysis and experiment study.Soft start-up is taken measures to erase the influence of over current and DC-link voltage overshoot, which can make APF start safely and steadily. The similarities and differences between software method and hardware method which realize soft start-up are analyzed. The parameter of current-limiting resistance is reasonably selected through PSIM simulation experiment. Finally, the results of the dissertation are summarized and some suggestions for the further research are put forward.