模块化多电平换流器子模块均压电阻参数优化策略

Parameter optimization strategy of sub-module balancing resistor in MMC

子模块的均压电阻在模块化多电平换流器(MMC)启动过程中起均压作用,同时在停运过程中作为电容的放电电阻,但目前缺乏均压电阻参数设计的理论依据和优化策略。通过优化子模块仿真模型引入均压电阻和取能电源相关参数;分析了均压电阻参数在MMC启动过程中对子模块电容均压的影响,阐明了均压电阻过大时电容均压效果劣化的机理;同时修正了MMC停运后子模块电容放电时间的计算方法;最后提出满足电容均压、放电时间和功率要求的均压电阻参数优化策略和具体设计步骤。依托厦门柔性直流输电工程给出均压电阻参数设计实例并进行相关试验,试验结果验证了所提均压电阻参数优化策略的有效性。

The balancing resistor of sub-module balances the voltage in the start-up process of MMC（Modular Multilevel Converter） and works as discharge resistor in the shutdown process,but there is a lack of the theoretical basis and optimization strategy of parameter design for the balancing resistor.Relative parameters of balancing resistor and draw-out power supply are introduced by optimizing the simulation model of sub-module. The influences of balancing resistor parameter on voltage-balancing of sub-module capacitor in the start-up process of MMC are analyzed,and the mechanism that voltagebalancing effectiveness is degraded with a too large balancing resistor is clarified. The calculation method of sub-module capacitor＇s discharge time after outage of MMC is corrected. The parameter optimization strategy and detailed design process are proposed for balancing resistor,which meet the requirements of capacitor voltage-balancing,discharge time and power. A design example of Xiamen HVDC flexible project is given and related tests are conducted. Testing results verify the feasibility of the proposed parameter optimization strategy of balancing resistor.