中文摘要：

对模块化多电平换流器（MMC）在正弦脉宽调制方式下子模块上下管开关器件的投入概率进行分析。结合上下管开关器件的投入概率,导出上下管开关器件等效电流的表达式。以子模块电容器在一个基频周期内的电压变化量是零为基础,推导出子模块电容器电压与电容器电容、负载功率因数、调制比及阀侧交流电流峰值之间的关系,并解析出上下管开关器件的平均电流与有效电流。利用开关器件制造厂商提供的损耗相关参数,对厦门柔性直流示范工程MMC在整流状态和逆变状态下的损耗和结温进行计算。计算结果表明,损耗计算和结温估算模型能为MMC冷却系统的配置提供参考。

英文摘要：

The active probability of upper and lower controllable switches of a modular multilevel converter （MMC） is analyzed under sinusoidal pulse width modulation. By referring to the active probability, the equivalent current of the upper or lower controllable switch can be derived. Then, based on voltage variation of the submodule capacitor in each fundamental period being zero, the voltage of the submodule capacitor can be obtained according to the capacitance of the capacitor, power factor, modulation ratio, AC current peak on valve side, and so on. And based on the equivalent current of the upper or lower controllable switch, the average current and effective current can be derived, respectively. Using the related parameters of the power losses of the controllable switch provided by the manufacturer, the power losses and junction temperatures of the controllable switch of Xiamen voltage source converter based high voltage direct current （VSC-HVDC） demonstration project are calculated under rectification operation and inverter operation conditions of the MMC, respectively. The results of the loss evaluatiou model and junction temperature evaluation model show that the evaluation models are able to provide the MMC cooling system configuration with reference.