柔性直流输电功率模块电容的在线监测

对于柔性直流工程所用的薄膜电容来说,其容量的衰减程度是电容老化和健康状态的重要指标。在回顾典型的电容容量估算方法的前提上,针对模块化多电平拓扑的柔性直流换流阀分析了实际工程中的测量数据所遇到的两种主要误差:采样噪声和同步误差。在此基础上,考虑了最近电平调制的特点,计算了功率模块在每个切除状态下的电容电压平均值和每个投入状态下的桥臂电流积分,利用最小二乘法设计了在线电容容量估算的方案。与其他两种方案的仿真对比表明,所提方法对采样噪声和同步误差敏感度低,算法简单计算量小,适用于实际工程。

Online Monitoring of Power Module Capacitance in VSC-HVDC Transmission

For the thin film capacitance used in voltage source converter based HVDC(VSC-HVDC)projects,the capacitance attenuation is the major criteria of capacitor aging and health.By overviewing the typical capacitance estimation method,two main errors of measurement data in practical engineering are analyzed focusing on the modular-multi-level(MMC)HVDC valve:the AD noise of capacitor voltage and arm current feedback,and the synchronization error between arm current and power cell status.Based on the measurement error analysis,a new online capacitance estimation method is presented using least square method,which takes into account the switching states of Nearest Level Modulation.The average capacitor voltage is calculated when the power cell is switched out,and the arm current is integrated when the power cell is switched in,so that the impacts of AD noise and synchronization error are minimized.The results of simulation comparison with the other two methods verify its accuracy and low sensitivity to measurement error,and it is suitable for industrial projects due to its simplicity and low computational efforts.