Capacitor voltage transformer (CVT) is widely applied to electric power system.It is beneficial to acquire the accurate transfer function of CVT for the protection and the monitoring of power system.At present, the reaserches about CVT are based on its typical equivalent circuit, however, due to the different internal parameters of CVT under different operating conditions, the transfer functions are different, which leads to inaccurate research results before.A square-wave pulse is applied to CVT when the internal structure parameters are not clear, then, the recursion method and the least square method are applied to caculate the impulse response of CVT based on convolution theorem, and Laplace transform is used to obtain the frequency transfer characteristics.The correctness of the theory and the reliability of the algorithm are verified by building the simulation circuit in PSCAD.Furthermore, the noise is added in the output signal, the anti-noise ability and noise impact factor of these two algorithms are analyzed in their algorithm structure.It is found that when noise is added, the anti-noise ability of the recursive method and the least square method are influenced by the length of convolution, both methods can get accurate results when the signal to noise ratio is larger than 40 dB.%电容式电压互感器(capacitor voltage transformer,CVT)在电力系统中应用广泛,获取CVT准确的传递特性有利于电力系统的保护和监测.目前关于CVT的研究一般基于其典型的等效电路,然而由于不同工况下的CVT内部参数不同,其传递函数各不相同,导致以往的研究结果不够准确.在未知CVT内部结构参数的情况下,对CVT注入方波脉冲,并基于卷积定理分别采用递推法和最小二乘法计算单位冲激响应,将其进行拉氏变换求得CVT频率传递特性.通过在PSCAD中建立仿真电路分析验证了该反卷积算法的可靠性.进一步在输出上叠加噪声,从算法结构上分析了上述两种算法的抗噪能力.研究发现,在加入噪声干扰时,递推法和最小二乘法的抗噪能力与所计算的反卷积长度有关;在噪声信噪比高于40 dB后,两种方法都能得到较准确的结果.
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