A Novel Method for CVT Transient Transform Characteristics Improvement Integrated With Digital Filter Suppressing Voltage Oscillation

Capacitive voltage transformer (CVT) transient transform characteristics destroy the linear relationship between output voltage and input voltage, leading to a sharp increase in measurement error. To address this issue, this article proposed an indirect method to design an infinite impulse response (IIR) filter to suppress the voltage oscillation amplitude caused by the CVT transient transformation characteristics. The method derives the CVT transfer function using the cascade form. Determining the compensating reactor frequency response curve, the intermediate transformer frequency response curve, and the oscillatory components below 50 Hz caused by ferromagnetic resonance as the design targets, IIR filters were designed to suppress the voltage oscillation amplitude. The proposed method’s effectiveness is verified by simulation in suppressing the voltage oscillation amplitude when transient response and ferromagnetic resonance occur. The simulation results show that the output voltage amplitude can be suppressed below 0.5 V after 0.48 s in the transient response, and the voltage oscillation amplitude caused by ferromagnetic resonance can be suppressed well under different short-circuit durations. This method also reduces the output voltage oscillation time and improves the CVT voltage measurement accuracy.