Current Limiter Based On The New Bridge Short Circuit Turn-off Devices

With the increasement of the scale and capacity of the electric power system of China, the short-circuit fault currents are getting higher and higher. The damages caused by a short-circuit fault are becoming more and more serious. As a result, Fault Current Limiters (FCL) is being more and more concerned.The reliability and cost of a FCL are two most important specifications because of its high voltage and great capacity. For a high reliability, the topologies and the control strategies of the FCLs must be optimum, the number of power semiconductor devices involved must be as small as possible. So the minimization of the volume, weight and cost of the FCLs is the main task of its design all along.Based on a great deal of readings, this paper outlined the concepts, methods and development of almost all kinds of FCLs and discussed in detail their advantages and disadvantages. The SCR-based bridge-type FCLs and their merits and demerits are emphasized. In order to overcome the shortcoming of half a cycle uncontrollable time of SCR-based FCL, we proposed new kinds of FCLs based on self-turn-off devices such as IGCT, GTO and IGBT. By shortening of the uncontrollable time of the rectifier bridge from half a cycle to the delay time of the measuring circuits, the volume, weight and cost of the DC reactor concerned can be decreased greatly. So the volume, weight and cost of the new FCLs can be decreased greatly.This paper researched the topologies, control strategies of the self-turn-off device based on bridge type FCLs for single phase, three-phase three-wire and three-phase four-wire power systems. By analyzing the control process of the full controllable bridge-type FCLs, new kinds of half-controllable FCLs based on self-turn-off devices are proposed. The new FCLs have fewer power semiconductors and simpler control method and control circuit. The cost of main circuits and control circuits of the new FCLs is decreased, and their reliability is increased. Simulations and experiments of the new FCLs are carried out which proved their validity and practicability.