Abstract：A grid-forming control strategy for hybrid topology modular multilevel converter (MMC) in dc distribution network is proposed to improve the reliability of dc distribution network. Firstly, the proportional control structure between the equivalent capacitor energy storage of the hybrid MMC power module and the angular frequency increment of the AC voltage vector on the converter side is proposed, which is as an autonomous control outer loop of the converter. It can use the sub-module capacitance of the converter to buffer power fluctuations. Compared with the first-order inertial link used in the outer control loop of the traditional virtual synchronous machine, the dynamic response speed is improved. Secondly, the overall control structure is designed including the grid forming control outer loop and the inner current loop. The outer loop provides system inertia, and the inner one achieves current tracking control and suppresses transient fault current effectively. Further, the small signal model of the hybrid MMC grid forming control is established. The influence of main control parameters such as inertia on the distribution of eigenvalues and stability of the system is analyzed. Finally, a hybrid MMC simulation model for DC distribution grid is built to simulate the isolated island operation, grid-connected operation mode and transient fault respectively, which verifies the proposed grid forming control strategy.
吴杰, 李传江, 周鸣, 茅红伟. 柔性直流配电网混合拓扑变流器的自治控制[J]. 电工技术学报, 2020, 35(24): 5175-5186.
Wu Jie, Li Chuanjiang, Zhou Ming, Mao Hongwei. Grid Forming Control of Hybrid Topology Converter for Flexible DC Distribution System. Transactions of China Electrotechnical Society, 2020, 35(24): 5175-5186.
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2020, Vol. 35 
