Selective compensation of power quality problems with a three-phase four-leg shunt active filter

This paper presents a selective compensation strategy for the three-phase four-leg shunt active filter (AF) to enhance the flexibility of compensation objectives. Due to nonlinear and unbalanced loads in a three-phase four-wire power system, power quality problems including harmonics, neutral current, unbalanced power and reactive current are introduced. It is desirable to make the AF versatile to compensate these problems. The synchronous reference frame (SRF) method is adopted to decompose the load current for current reference generation. An adaptive linear element (Adaline) based low pass filter (LPF) is proposed to improve the time delay caused by the SRF method under steady and dynamic load conditions. Selective compensation of power quality problems is realized by combining the decomposed currents with corresponding priority coefficients. Simulation results are given to verify the feasibility and effectiveness of the proposed strategy under steady and dynamic operating conditions.