Research On Solid State Transfer Switch And Design For Control And Protection System

With the development of modern industry and technological advances,a large number of nonlinear loads have being used in the grid and at the same time they bring serious pollution to the power quality of power system.Meanwhile a variety of sensitive loads propose higher requirements on the power quality,such as precise medical devices、high-performance office supplies、 automatic control equipments in the continous production and so on.Effective management of transient power quality has become a hot research topic at home and abroad.In this paper,Solid State Transfer Switch (SSTS) system is been proposed which consists of rapid vacuum circuit breaker in parallel with thyristor. Solid State Transfer Switch combines the advantages of high-power power electronics、 microprocessor、optical fiber communication and digital signal processing to supply uninterrupted power for sensitive loads.It can reduce the affect of voltage dips、instantaneous power failure on sensitive loads so as to improve the reliability of electricity supply.This paper introduces the basic principle of Solid State Transfer Switch from the respect of basic structure and the switching process、qualitatively analyses the current commutation process between the rapid vacuum circuit breaker and thyristor、analyses two ways of current commutation between thyristor and thyristor and then proposes two switch control strategies for SSTS,which are zero-crossing switch and forced switch.This paper does simulation study for the two switch control strategies.The paper introduces control and protection system from both hardware and software design.Finally the low-voltage test verified the reliability of switching control strategy and control and protection system.