Multivariable Grid-Forming Converters With Direct States Control

This paper presents an improved multi-input multi-output based grid-forming (MIMO-GFM) converter control method using multivariable feedback control. Although the original MIMO-GFM control is proven to be superior and robust using only low-order controllers, it is easily affected by high-frequency components, particularly for the converter without inner cascaded voltage and current loops and when it is connected into a strong grid. The proposed method selects frequency and internal voltage as state variables to be directly controlled while effectively eliminating the impact of high-frequency components without increasing system complexity. The H∞ synthesis is used to tune the parameters to obtain an optimized performance. Experimental results and system-level simulations verify the effectiveness of the proposed method.