Abstract: Hysteresis circle current control method with variable circle width of the shunt active power filter not only ensures the tracking accuracy of reference current,but controls the switching frequency of inverters effectively through adjusting hysteresis circle width in real-time according to current amplitude.Traditional hysteresis circle current control method with variable circle width is improved by adding an amplitude limiting element and a frequency feedback PI control method,which limits the abnormal current fluctuations and controls the frequency of the PWM series accurately.The Matlab simulation results show that the total harmonic distortion of the system when harmonic current is tracked and compensated by the improved method is less than the value by the traditional method.

Key words: active power filter;harmonic;variable circle width;hysteresis circle current control