Research On Topology And Application Of DC Solid State Fault Current Limiter

With the rapid development of power electronics technology,DC transmission and distribution technology has attracted increasing attention.The protection technology in the DC system is one of the key technologies of the DC transmission and distribution system.At present,the protection measures on the DC side of the DC system usually use DC circuit breakers to suppress the fault current,but with the development of DC technology,the fault current is getting worse and worse,which puts forward higher requirements on the shielding capacity of the DC circuit breake r,and the manufacturing cost it is getting higher and higher.Therefore,in order to reduce the manufacturing cost of the circuit breaker and improve the reliability of the DC system,a DC current limiting technology is urgently needed to isolate the fault current with the circuit breaker.This paper presents a topology of DC solidstate current limiters based on thyristors,according to its structural characteristics,it is improved to realize the functions of bidirectional current limiting,self-bypass of reactor and adaptive current limiting,etc.and verify its current limiting effect in the DC system.Firstly,this thesis proposes a DC solid-state fault current limiter based on thyristors,analysis of the operation principle and operation mode of the current limiter is given and performs simulation verification on the operation principle of the current limiter and simulation analysis of the current limiting effect;On this basis,the adaptive current limiting of the current limiter is proposed,and the influence of the adaptive current limiting on the current limiter is simulated and analyzed.Secondly,according to the characteristics of DC system,the current limiter is improved to have the function of bidirectional current limiting and s elf bypass of current limiting reactor,and the realization methods of various functions are analyzed theoretically,and the adaptive current limiting method of the improved current limiter is explained.Various functions are simulated and verified,and th e influence of different current limiting devices on the current limiting effect is simulated and analyzed;for the peak value of fault current,the current limiting resistor is used to enhance the suppression of the peak value of fault current by the current limiting resistor,and the influence of current limiting resistor on the current limiting effect and on the key closing device of the current limiting device is simulated and analyzed.Then,the short-circuit fault of the two terminal 10 k V flexible DC transmission and distribution system is analyzed theoretically.Through the theoretical analysis and simulation verification of the system fault,the fault type of the current limiter application is determined.Finally,the application of current limiter in DC distribution system is theoretically analyzed and simulated by studying the topology of current limiter and fault characteristics of DC system.This paper validates the bidirectional c urrent limiting,reactor self bypass and self-adaptive functions of the current limiter in the system,and theoretically analyzes and simulates the current limiting effect of the current limiter and its influence on the circuit breaker in the DC system,wh ich provides theoretical support for the feasibility and effectiveness of the application of the current limiter in the system.