A Solid-State Current limiting Switch for the Application of DC Power Network

When designing a large distributed dc power network, special attention must be placed on the electrical stability, control of the systems, and individual load on the systems. In order to prevent the fault propagation, provide protection against overload and fault, and isolate the faulty load and equipment in a dc power network, an overcurrent protection device must be applied to the switch gear for the electric power management and control of the systems [1]. Overcurrent protection devices such as circuit breakers in the primary and secondary distribution systems protect all branch circuits on the load side of the discharge bus. A circuit breaker is electromechanical devices that may be reset and reused after an overload or low-value short circuit, but most manufactures recommend replacement if the device ever interrupts a short circuit with a fault current close to its interrupt rating. Furthermore, circuit breaker has the conflicting of time delay characteristics that trip delays must be long enough to open the circuit when a real fault exists [4]. A solid state type of power switching circuit has been developed as a new power protection technique for dc power network instead of electromechanical circuit breaker. The candidate for these switching devices should be Si Power MOSFET, IGBT, and SiC MOSFET. As an example of an electromechanical circuit breaker delay curve application, consider a 50 A circuit breaker and fault that draws 200 A (400% of circuit breaker rating).The opening mechanism in circuit breaker will not completely open until as much as 0.2 s has elapsed [1]. While on the other hand, solid-state current limiting switch will open within 20 μs and this elapsed time and current rating can be adjusted freely [2]. From the stand point of the dc network stability, when the transient over current caused by fault and or short circuit will be observed, a solid-state current limiting switch will act as over current suppression as a secondary role in the dc power network. In this paper, we describe the performance of these solid state type of power switching circuit in DC power network and result of stability analysis using Power Electronics Circuit Simulator, PSIM.