Novel Bridge-Type FCL Based on Self-Turnoff Devices for Three-Phase Power Systems

In this paper, a novel bridge-type fault current limiter (FCL) based on self-turnoff devices for three-phase power systems is proposed. Compared with the SCR-based bridge type FCL, the new one is smaller in size, better in dynamic performance, and simpler in control method and control circuitry. The novel FCL is composed of a rectifier bridge-a dc-limiting reactor and one/three bypass reactor/reactors-for a single-phase/three-phase structure. The increasing speed of the fault current just after the occurrence of a fault is limited by a dc-limiting reactor, whose inductance is designed according to the response speed of the control circuit. The bypass reactors are designed in terms of the requirements of the coordination of protective relays. The source currents during limiting events are sinusoidal and do not have any harmful effects on the overall protection schemes, impedance relays, and conventional current and voltage transformers. The topologies of the proposed FCL for three-phase four-wire and three-phase three-wire power systems are investigated, respectively, in detail. Parameter design and optimization are presented. The fault and fault-mode judgment method is described briefly. Simulations and experimental results prove the feasibility of the new FCL.