混合型模块化多电平换流器解析建模与功率运行区间分析

混合型模块化多电平换流器(MMC)在远距离大容量架空线输电领域具有十分广阔的应用前景。为定量研究混合型换流器的运行特性,文中提出了混合型MMC动态解析模型和稳态解析模型的建模方法。通过稳态解析模型求解与换流器内部电气量和控制量有关的非线性方程组,实现了在任意直流电压和功率运行点下换流器运行特性的完全解析求解。对比了不同直流电压水平下,电磁暂态模型仿真结果和稳态解析模型的计算结果,验证了稳态解析模型的精确性。研究了考虑多种运行约束条件时混合型MMC的功率运行区间计算方法,尤其考虑了半桥子模块的均压约束。计算了不同直流电压水平下的功率运行区间,分析了各约束条件以及子模块电容、桥臂电抗器、桥臂子模块比例等参数对功率运行区间的影响。

Analysis on analytical Modeling and Power Operating Zone of Hybrid Modular Multilevel Converter

Hybrid modular multilevel converter(MMC)has a broad prospect in long-distance, bulk-power high voltage direct current(HVDC)transmission with overhead lines. To analytically investigate the operating characteristics of converters, the dynamic and static analytical models of hybrid MMC are proposed. By solving the nonlinear equations regarding the internal electric quantities and control quantities though the static analytical model, the operating region of the converter under certain DC voltage and power is analytically obtained. The simulation results from electromagnetic model and the calculation results from the static analytical model regarding the internal quantities of the converter under different DC voltage levels are compared, which verifies the correctness of the static analytical model. A calculation method for the power operating zone of hybrid MMC is presented with multiple operating constraints considered, especially the constraint about feasible balancing of half-bridge sub-modules. The operating zones under different DC voltages are calculated, and the impact of various operating constraints and converter parameters like sub-module capacitor, arm inductance and full-bridge sub-module ratio on the operating zones are studied. The proposed analytical models provide the foundation for parameter design, steady-state analysis and small-signal modeling of hybrid MMC.