Study On Bridge Type Superconducting Fault Current Limiter

With the expansion of the power system scale and capacity,capacity of short circuit and short-circuit current level is also rising,the demand of limiting the short circuit current is becoming more and more urgent.Because of the huge advantages,superconducting fault current limiter become the forefront of current limiting technology research in many countries in recent years.saturated iron-core type high temperature superconducting fault current limiter has the advantages of small size,light weight,fast response and easy to match with the auto-recloser,which has a very wide range of applications.Firstly,the research status of superconducting material and superconducting fault current limiter are discussed in this paper.The basic physical properties of superconducting materials are introduced,the topology and operating principle of various types of superconducting fault current limiter are studied.The advantages and disadvantages of each type of superconducting fault current limiter are analyzed,and the evaluation index of superconducting fault current limiter is presented.In most of the time,the power system is in a state of normal operation,in a short time will be in short circuit state,that is,HTSFCL bias power supply will be in most of the time in the state of power supply.To solve the above problems,this paper presents a new type of saturated iron core type high temperature superconducting fault current limiter,the core of the device for four column type structure,the effective length of the reduced magnetic circuit,compared with the same level of short-circuit capacity HTSFCL,can effectively reduce the size of the bias current.The capability of HTSFCL is determined by the magnitude of the bias current.When the power grid short-circuits fault current limiter,the bias coil will be induced even frequency reverse electromotive force,the bias current is no longer a simple DC,but DC and even harmonic component of the superposition of harmonic Reverse electromotive force generated will affect the precision of current control.To ensure the accuracy of the bias current control system,the design of saturated iron core fault hysteresis control and BP neural network control limiter control system based on the bias current,has the advantages of high precision,good flexibility,strong applicability,applied to the saturated core fault current limiter nonlinearity time-varying system can obtain good control effect.Finally,this paper has designed the experimental platform based on DSP of TMS320F28335,including the signal acquisition circuit,conditioning circuit,IGBT drive circuit,lower machine software and upper moniter software,and then the control effect of bias current and the current limiting performance of current limiter are studied in the paper.In this paper,the theoretical study and mathematical modeling of the bias current limiting for HTSFCL are presented.Through the MATLAB simulation analysis and experimental research,this paper puts forward the improvement scheme for the bias current of the current limiter,which provides some reference value for the further study of the HTSFCL.