Research on three-phase four-wire shunt active power filter for harmonic and reactive compensation

The conventional harmonic and reactive control strategy based on the instantaneous reactive power theory strategy reveals poor performance under distorted and/or unbalanced conditions. In order to overcome this problem, a novel control strategy based on the decoupled double synchronous reference frame (DDSRF) PLL is proposed in this paper. The DDSRF-PLL uses a dual synchronous reference frame and a decoupling network to effectively extract the positive-sequence voltage components in a fast and accurate way, which enables the superior harmonic and reactive compensation for active power filters in the non-ideal conditions. Results obtained by simulations with Matlab /Simulink show that the proposed approach is an effective approach for compensating reactive power and harmonic currents of the load, even if the source voltages are severely distorted and unbalanced.