CVT杂散电容对谐波传输特性影响研究

Research on the Influence of CVT Stray Capacitance on Harmonic Transmission Characteristics

在含有谐波分量系统中,杂散电容是电容式电压互感器(Capacitor Voltage Transformers,CVT)计量谐波准确性的重要影响因素,CVT等效电路中存在的分布电容和杂散电容导致测量结果有较大误差,无法正确反映电网中实际谐波水平。在MATLAB/Simulink环境中建立CVT传输特性仿真模型,采用施加谐波源法对互感器一次和二次侧电压进行采集信号并作快速傅里叶变换分析,求取各次谐波含有率并得出CVT传输特性曲线,分析杂散电容对CVT传输特性的影响。研究结果表明,CVT中间变压器一次侧绕组对地杂散电容对CVT传输特性有较大影响,而中间变压器二次侧绕组对地杂散电容造成的影响较小,可忽略不计。研究结果可为CVT准确监测谐波电压提供参考。

In a system with harmonic components,stray capacitance is an important factor impacting the accuracy of harmonic measurement by capacitor voltage transformers(CVT).The distributed capacitance and stray capacitance existing in the CVT equivalent circuit cause a large error in the measurement result,which cannot accurately reflect the actual harmonic level in the power grid.To analyze the impact of stray capacitance on the transmission characteristics of CVT,in this paper,a simulation model of CVT transmission characteristics is established through MATLAB/Simulink,and the harmonic source method is used to collect signals from the primary and secondary voltages of the transformer,the FFT analysis mothed is used to obtain the harmonic content rate of each order and the CVT transmission characteristic curve.The research results show that the stray capacitance of the primary winding of the CVT intermediate transformer to the ground has a greater impact on the transmission characteristics of the CVT,while the stray capacitance of the secondary winding of the intermediate transformer has a smaller impact and can be ignored.It provides a reference basis for CVT to accurately monitor the harmonic voltage.