A controller based on resonant filters for a series active filter used to compensate current harmonics and voltage unbalance

In this paper we present an adaptive controller for the series active filter used to guarantee a balanced voltage on the load side while compensating selected current load harmonics. These objectives are accomplished despite unbalance and harmonic distortion in both the source voltage and current load. To achieve current harmonics compensation, a bank of (passive) band-pass filters is connected in shunt to the load, where each one is tuned at the harmonic concerned. The series active filter then injects voltage harmonic components at the same frequency as the current harmonics and, as a result, it imposes a high impedance on the line path, thus forcing the load current harmonics to flow into the bank of (passive) band-pass filters. The controller also computes the required voltage to be injected by the series active filter to compensate for unbalance and most of the distortion in the source voltage.