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.