| The transformation of energy source in the modern power grid and the rapid development of electronic technology make the whole power system more complex and changeable.In addition,the large-scale integration of all kinds of distributed generators and the expansion of transmission and distribution network lead to the growth of fault currents,which gradually approaches or even exceeds the interrupting capacity of the existing circuit breakers,posing a serious threat to the safe operation of the power system and the electrical equipment.Therefore,it is necessary to take corresponding measures to limit the short-circuit currents.And the superconducting fault current limiter(SFCL)presents rather low impedance in the normal operation and quickly turns into high impedance to effectively suppress the current in the event of short-circuit fault.Based on the above characteristics,SFCLs are concerned by many scientific researchers.With its economic barriers gradually being broken,the SFCL will be recognized for its advanced technology and engineering practicality,which is significant to limit shortcircuit currents and guarantee the reliable operation of the power grid.In this paper,working principles of various types of SFCLs are firstly illustrated in detail.Then,the researches,applications and developing trends of SFCLs are also introduced.In the background of applications of SFCLs in the power grid,the improved particle swarm optimization(PSO)algorithm based on the Pareto optimal principle is proposed to discuss the placement of SFCLs in the power system,which provides many feasible allocation schemes of SFCLs for power designers.Meanwhile,compared with conventional current-limiting air core reactor,an economic analysis on the application of the SFCL with the net present value(NPV)index method is carried out,involving the total cost of the current-limiting equipment and the whole electrical network power losses.And the 39-node New England power transmission system based on the MATLAB simulation platform is built and simulated to prove that SFCLs are economic in saving the network power losses,which shows great promises of a wider application of the SFCL in future electrical power transmission systems.Actually,the integration of SFCLs in the power grid will affect the transient stability of the power system.The SFCL is able to rapidly react and present high impedance in the fault time,but it must take a certain time to become superconducting again.The state transitions will definitely change the transient process of the power system.According to the operation and recovery characteristics of SFCLs,this paper discussed the influences of different types of SFCLs on the transient stability of the power system,and then put forward corresponding solving method,that is selecting proper current-limiting impedance value or improving the recovery speed of the SFCL,to protect the safe operation of the power system,which provides a reference for the application of the SFCL in the power system.Moreover,the integration of inductive SFCLs in the high-voltage transmission line will lead to the increase in the rising rate of the transient recovery voltage(TRV)of circuit breakers,which causes that circuit breakers could not extinguish AC arc during fault removing process.This will result in the failure of the fault isolation and seriously threat the safe operation of the power system and the equipment.So this paper also analyzed the influences of inductive SFCLs on the TRV of the circuit breaker in a highvoltage transmission line,and then the solutions to TRV-related problems induced by inductive SFCLs are seriously proposed to satisfy the standards,which also offers a reference for the design and application of SFCLs in the high-voltage power system. |
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