Coordination Control of Multi-Port Solid-State Transformer Based on Mode-Switching and Adaptive Parameter Optimization Against Disturbances

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This paper presents a coordination control strategy for a multi-port solid-state transformer (MPSST) that utilizes mode switching and adaptive parameter optimization to address disturbances. First, the mathematical modeling and characteristic analysis of the MPSST is conducted, focusing on the effects of DC bus voltage and grid fault on the stability of the MPSST. Then, a multi-loop switching control that includes constant-voltage and voltage-power droop control is applied for the high-voltage stage, while the isolation stage employs a multi-voltage loop switching control, and the low-voltage stage utilizes a hierarchical control for the PV generation, battery energy storage (BES), and power loads. Furthermore, the mode switching criteria of different stages in the MPSST are outlined, and a coordination parameter optimization using the adaptive firefly algorithm-particle swarm optimization (FA-PSO) is designed. Finally, a detailed digital model of the MPSST is created using MATLAB, and simulations under various disturbances as well as comparative verification in hardware-in-the-loop (HIL) test, are carried out to validate the effectiveness of the coordination control. The findings confirm that this approach can sufficiently address the grid fault and continuous source-load disturbances, and visibly ensure the stability of the MPSST during grid-connected operations.