换流站高压电容器组不平衡电流测量方法及装置研发

换流站高压电容器组不平衡电流现场测试受复杂电磁场干扰比较严重，而且试验过程中不平衡电流很小，难以直接准确测量。提出一种全新的测量方法，将高频低压交流信号施加于电容器组，通过采集桥臂不平衡电压并采用二阶高通滤波器滤除工频干扰，根据电容器组等效阻抗，计算出不平衡电流值。给出测量装置的实现原理并从电源纹波干扰、工频干扰、放电干扰、器件热噪声干扰等方面采取措施，实现精准测试。现场测试结果表明，新方法理论思路正确，不平衡电流值测量准确。

Research on Method and Device for Measuring Unbalanced Current of High Voltage Capacitor Bank in Converter Station

Complex electromagnetic field in converter station poses a serious interference to the field test of unbalanced current of high voltage capacitor bank, and the unbalanced current is too small to be accurately measured directly during the test. This paper proposes a new measurement method that the high frequency low voltage AC signal is applied to the capacitor bank, and the power frequency interference is removed through collecting the unbalanced voltage between the bridge arms and by use of the second-order high-pass filter, and then the unbalanced current value is calculated based on the equivalent impedance of the capacitor bank. The paper also presents the principle for developing measuring devices, and the measures taken for removing such interferences as power ripple interference, power frequency interference, discharge interference, thermal noise of the devices so as to achieve accurate testing results. The field test results show that the new method is correct in theoretical thinking and accurate in measuring the unbalance current.