Research on Balancing Control Technology of Series Dual Valve Groups in Hybrid Multi-terminal UHVDC Transmission System

The balancing control technology of series dual valve groups in hybrid multi-terminal UHVDC transmission system is studied in this paper. Firstly, the reason for the imbalance of the two valve groups is analyzed. It is shown that for the fixed-power control MMC converter station of the series double-valve structure, it is highly probable that the double-valve group will be unbalanced during the operation, so it is necessary to add the corresponding control strategy. Then, a voltage balance control strategy based on voltage-power deviation between series two-valve groups and PI control is designed. Correcting the power setting value of the two valve groups due to the voltage deviation can effectively improve the equalization of the series double valve group. Finally, a simulation model is established in PSCAD to verily the feasibility and effectiveness of the proposed control strategy.