An Improved Grid-Forming Control Strategy for Three-Phase Four-Wire Converter with Unbalanced Load

With the increasing diversification of microgrid load types, grid-forming (GFM) converters face growing challenges in managing unbalanced loads, which degrade system stability and power quality. This paper investigates the harmonic characteristics of the output voltage in three-phase four-wire converters to elucidate their impact on errors in sequence component separation. To address these challenges, a novel unbalance load compensation strategy is proposed, implemented in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d q 0$</tex> coordinate system and leveraging a dual second-order generalized integrator (D-SOGI) filter. Compared to conventional approaches, the proposed strategy significantly enhances the accuracy of positive- and negative-sequence separation, mitigating the effects of harmonic distortions and improving the balance of the three-phase output voltage after compensation. The effectiveness of the proposed strategy is validated through simulation and experimental results, demonstrating superior performance in enhancing microgrid stability and load adaptability under unbalanced conditions.