模块化多电平柔性直流换流阀寄生电容提取及分布特性研究

Research on Extraction and Distribution Characteristic of Parasitic Capacitance in MMC-HVDC Flexible Valve

模块化多电平柔性直流换流阀的寄生电容是构成换流阀宽频等效电路模型的重要参数,影响换流阀内部瞬态电压分布是否均匀。为此,需要准确提取出换流阀的寄生电容。该文提出寄生电容的提取方法,并验证方法准确性;此方法结合换流阀的结构对称性,简化离散电容矩阵,详细给出基于有限元理论的电容容值计算公式。以国内某±420kV/1250MW模块化多电平柔性直流换流阀为例,对换流阀的寄生电容进行详细分类和计算,并给出其典型的电容值;获得换流阀的均压环和子模块自身及相互之间、以及对阀厅的电容分布特性。结果表明同层同阀段相邻子模块之间的电容值最大,约为100pF。

Parasitic capacitance in MMC-HVDC flexible valve is the important parameter of the wide-band equivalent circuit model of converter valve, and is one influencing factor for uneven distribution of transient voltage in converter valve. Therefore, it is necessary to accurately extract parasitic capacitances in MMC-HVDC flexible valve. An extraction method of parasitic capacitance was proposed in this paper, and its accuracy was verified, combining with structural symmetry of MMC-HVDC flexible valve, capacitance matrix was simplified and discretized. These capacitance calculation formulas based on FEM were given detailedly. Took a domestic ＋420kV/1250MW MMC-HVDC flexible valve as an example, parasitic capacitances of converter valve were classified and calculated in detail, and their typical capacitance values were given. Capacitance distribution characteristics of grading ring-valve hall, sub module-valve hall, grading ring-sub module, grading ring-grading ring, sub module-sub module in converter valve were obtained, the results show that the capacitance value of adjacent sub module in a valve segment is the largest, and the value is 100pF.