Single-DC Reactor-Type Transient Limiter for Reducing Three-Phase Power Capacitor Switching Transients

This paper presents a new application of the single-dc reactor-type fault current limiter to suppress the three-phase low-voltage capacitor switching transients. The proposed limiter is composed of a three-phase coupling transformer, a three-phase bridge rectifier, a dc reactor, and a dc-bias voltage source. The dc reactor is connected in the three-phase coupling transformer's secondary winding and can automatically provide high impedance at the instant of energization, thus restraining the energizing transients of the three-phase capacitor. In the steady state, the bias voltage causes all rectifier diodes to conduct simultaneously, and the limiter freewheels. Therefore, the voltage across the coupling transformer's secondary side is nearly zero, and the transformer's primary side acts as a short circuit. The limiter will not result in a voltage rise at the capacitor's terminals or a distortion of the capacitor's current waveform in the steady state. Due to the freewheeling effect in the limiter, no transient overvoltage appears across the switching device at the instant of de-energization. Analytical equations to describe the performance of the system have been developed. Finally, a 2.7-kVAR three-phase capacitor is used for demonstration, and simulation and experimental results are carried out to verify the feasibility of the proposed limiter.