A Simple Double-Line-Frequency Pulsating Power Mitigation for Grid-Forming Converters Under Imbalanced Grids

Traditional grid-forming (GFM) converters based on the quasi steady-state power control are sensitive to negative sequence grid voltage disturbances, causing significant double-line-frequency power oscillations. Traditional power oscillation suppression methods are mainly based on complex sequence decomposition, with complex algorithms and large amount of calculation. In this article, a simple pulsating power mitigation approach is proposed for GFM converters, without using any sequence decomposition of converter line current nor grid voltage. The proposed system is implemented by only adding a simple pulsating active power mitigation loop to produce an adjustable factor that multiplies with the instantaneous converter voltage. Based on the adjustable factor, the compensation voltage can be easily extracted and added to the original reference voltage from GFM power controller. With this slight modification, the pulsating active power can be effectively suppressed in various voltage imbalance conditions and power operation points. Extensive analysis and experimental results have been obtained to validate the correctness of the proposed approach.