A Novel Robust Current Control Approach Using Adaptive Line Enhancer for Three-Phase Current Source Active Power Filter

Abstract

An effective system control method is presented for applying a three-phase current-source PWM converter with a deadbeat controller to active power filters (APFs). In the shunt-type configuration, the APF is controlled such that the current drawn by the APF from the utility is equal to the current harmonics and reactive current required for the load. To attain the time-optimal response of the APF supply current, a two-dimensional deadbeat control scheme is applied to APF current control. Further more, in order to cancel both the delay in the two-dimensional deadbeat control scheme and the delay in DSP control strategy, an adaptive Line Enhancer (ALE) is introduced in order to predict the desired value of three sampling periods ahead. ALE has another function of bringing the robustness to the deadbeat control system. Due to the ALE, settling time is made short in a transient state. On the other hand, total harmonic distortion (THD) of source currents can be reduced as much as possible compared to the case that ideal identification of controlled system could be made. The experimental results obtained from the DSP-based APF are also reported. The compensating ability of this APF is very high in accuracy and responsiveness although the modulation frequency is rather low.