DC-Link Zero Power Fluctuation of Grid-Tied Inverters: Implementation With Two-Phase Virtual Phase-Current Regulation

Unbalanced grid conditions caused by asymmetrical faults or voltage distortions extremely deteriorate the grid reliability, resulting in power fluctuation of three-phase grid-tied inverters at dc link. A virtual phase-current regulation (VPCR) method is introduced in previous research to solve the power quality problem depending on controller feedback current regulation. With VPCR, the dc-link power fluctuation can be suppressed, whereas cannot be completely removed. To fulfill this gap, a novel two-phase VPCR method is proposed in this article, in which an additional virtual phase current gain in the non-fault phase has been introduced into the current loop. Since more VPCR parameter adjustments can be realized, a complete smoothing of dc-link power fluctuation is achieved by the proposed method. Accordingly, based on the particle swarm optimization (PSO) algorithm, a parameter tuning method of two-phase VPCR is designed to achieve a fast and convenient parameter optimization. The proposed two-phase VPCR method as an emerging tool of dc-link power quality governance is verified by simulation and experiment.