Design of a novel bridge-type FCL and its application in UPFC

Aiming at the problem of short-circuit protection, a novel bridge-type topology of fault current limiting (FCL) is established based on resonant characteristics. It is equivalent to a piece of wire during the normal operating state. When short-circuit fault occurs, the dc limiting reactor inserts automatically and rapidly under the joint action of the capacitor, limiting the increasing speed and amplitude of fault current, therefore protects the security of the equipment. Compared with the original topologies, the novel topology proposed reduces the number of controllable devices, simplifies the control system, and reduces the design value and size of the dc limiting reactor, which makes it has the advantages of high reliability, low cost, and minimum maintenance requirements. The structure and working principle of the FCL proposed are elaborated in detail. Meanwhile, a topology of its application in unified power flow controller (UPFC) is proposed to verify its function. Simulations prove the feasibility of the new FCL.