Active power filter(APF) usually appears unstable and it is quite difficult to determine its exact mathematical model , when the load and parameters are changing. In order to treat this problem, fuzzy proportional-integral(PI) controller and Lyapunov-based stability theory were introduced into the direct current(DC) side voltage control and current control of APF to guarantee the precision and stability of APF. Through fuzzification, fuzzy inference and defuzzifier, fuzzy PI controller adjusted the parameters of the PI controller according to the error and error varying rate of the DC side voltage. After testing on four different control methods with Matlab/Simulink, the distinctive effectiveness of the proposed method was therefore confirmed. The results showed that, when the load and parameter change abruptly, compared with PI and hysteresis controllers, the total harmonic distortion(THD) of source current after applying the proposed method is decreased obviously.When the load is time-varying and parameter changes abruptly, both the THD of source current and overshoot of the DC capacitor voltage are much smaller in the proposed method, while the APF runs unsteadily after applying PI and hysteresis controllers.
