High-Frequency High Step-Up Inductive Power Transfer-Based Capacitor Charger in Active Injection DC Circuit Breakers

This article investigates the application of inductive power transfer (IPT) based converters as capacitor chargers for dc circuit breakers (DCCBs) including active injection circuits (AIC). AIC generates resonant countercurrent pulses to achieve transient current commutation. There are three main contributions. First, a high-frequency and high step-up wireless inductive series-parallel (WISP) converter is applied to charge the injection capacitor of AIC, which achieves reliable voltage isolation and constant voltage output with a simple structure. Second, WISP converter is optimized for DCCBs with three objectives: 1) reducing transient time, 2) reducing transient and steady-state power loss, and 3) enhancing compactness. Four parameters impacting the transient are analyzed through LTspice simulations and experiments, namely the input dc voltage, voltage step-up ratio, quality factor, and the injection capacitor. Third, a burst switching mode control is proposed to reduce steady-state power loss. An optimized WISP converter operating at 1 MHz with a voltage gain of 8.33 is implemented and applied to a 380 V/50 A/5.2 μs AIC SSCB. Based on the experimental results, a 10 μF load capacitor is charged to 80 V in 2.37 ms and 90 V in 2.9 ms. It presents 66.7% efficiency during transient and 99.6% energy saving during steady-state while keeping the output voltage ripple within 2%.