基于谐波注入法的差分式非接触电压测量

Differential Non-contact Voltage Measurement Based on Harmonic Injection

当前基于电容耦合的传感器尚无有效、便捷的耦合电容动态校准方法,影响测量精度。因此,提出了基于谐波注入的差分式非接触电压测量方法,首先,利用感应探头与跨阻运算放大器将基频信号引入测量系统;其次,通过屏蔽罩,减小外界杂散电容变化带来的干扰,改进探头并引入差分式电路结构,消除运放输入电容的影响;再次,对测量电路注入谐波,并利用离散傅里叶变换(discrete Fourier transformation,DFT)实现对响应信号中基波信号与谐波信号的提取,通过计算谐波源与谐波响应信号的比值,求解出耦合电容参数,实现其动态校准;最后,将校准的电容参数代入基波方程,实现基波电压信号的测量。通过仿真结果表明,所提的测量方法可在10 kV的应用场景中满足对变化的耦合电容校正要求,且最大的电压测量误差小于0.4%。

At present,there is no effective and convenient dynamic calibration method for coupling capacitors based on capacitive coupling sensors,which affects the measurement accuracy.Therefore,a differential non-contact voltage measurement method based on harmonic injection was proposed.Firstly,the fundamental frequency signal was introduced into the measurement system using a sensing probe and an I-V converter.Secondly,the interference caused by external stray capacitance changes was reduced through a shield,and the probe was improved and a differential circuit structure was introduced to eliminate the influence of the op-amp input capacitance.Then,the harmonics were injected into the measurement circuit.After that,the measurement circuit was injected with harmonics,and the fundamental and harmonic signals in the response signal were extracted by discrete Fourier transformation(DFT),and the coupling capacitance parameter was solved by the ratio of the harmonic source to the harmonic response signal,and its dynamic calibration was achieved.Finally,the fundamental voltage signal was then measured by substituting the calibrated capacitance parameters into the fundamental equation.The proposed measurement method was shown by simulation results to meet the requirements for varying coupling capacitance correction in a 10 kV application scenario with a maximum voltage measurement error of less than 0.4%.