Optimized Design On Practical Prototype Of 220kV Novel Solid-state Fault Current Limiter

Among all kinds of faults in power system,the short circuit fault is the most likely to happen and causes the biggest damage to system operation and power equipment.In order to prevent the damage of short circuit current to the power equipment,and to enhance reliability and stability of power system,it becomes a hot spot in research to develop effective fault current limiting technologies and fault current limiting device.This paper is set to design and produce a novel solid state fault current limiting practical device applied in the 220kv/1.5kA power system.Aim at the current limiting requirements of the power system and practical application,this paper optimized the design of the main electrical devices and control and protection system of the novel solid-state current limiter.First,this paper introduced three types of solid-state current limiter currently:magnetic saturation-type's,resonant-type's and bridge type solid-state fault current limiter's topologies in detail.It also analyzed the advantages and disadvantages of each type of SSFCL and finally made the saturated autotransformer coupling bridge type solid-state current limiter as the prototype of the novel practical solid-state current limiter.It analyzed the working principle of the novel SSFCL and laid the foundation for the design of parameters of the prototype device by establishing the mathematical model of SSFCL under different status.In addition,this paper introduces the combination of the novel SSFCL and the flexible AC transmission technology.For the example of Unified power flow controller with FCL,this paper analyzed its impact on the transient stability of the power system in view of the current limiter modules.And it made a simulation in the standard 220kV three generators nine nodes system.The simulation results show that UPFC-FCL can reduce imbalance between the input and output of generators and the amplitude and duration of generators' angle oscillations after faults.Even in the case of fault continuing,it can also ensure system angle stable and at the same time reduce the value of the voltage drop after the fault to improve the transient stability of the system.Secondly,this paper optimized the design of main equipments of 220kV SSFCL practical prototype device,including the design of saturated autotransformer,the selection of thyristors,the selection of voltage-limiting valve,the design of DC current limiting reactance,the selection of cooling circulatory system,current and voltage sensor and the bypass isolating switch and circuit breaker.It established Saturated autotransformer coupling bridge type solid-state current limiter circuit model in ANSOFT/SIMPLORER and made simulations of normal working condition and short circuit working condition.It compared the fault current level with and without SSFCL in the system.The simulation results indicated that the design of main equipment satisfy the requirement of current limiting.In addition,it designed the layout of SSFCL.Finally,the control and protection system of the novel SSFCL practical prototype was designed,including hardware design and software implementation.The hardware of control and protection system is based on the high performance real-time control system hardware platform produced by NI companies from the United States,mainly composed of PC(the human-computer interaction system),the core controller,input/output module,signal processing module and photovoltaic conversion module.The software of control and protection system is mainly composed of six state processing modules.Each module has a clear division of responsibilities and is independent with each other.A low voltage SSFCL prototype model was developed and short circuit current limiting experiment was carried out.Through the analysis of its operating conditions,it verified and optimized the design of the control and protection system.Based on the control system of the new bridge-type solid-state fault current limiter(SSFCL),this article compared and analysed three fault current cut methods after the short-circuit:freewheeling interruption mode?invert interruption mode and invert freewheeling hybrid interruption mode.In addition,low voltage SSFCL model machine is built to verify the analysis results.It shows that the invert freewheeling hybrid interruption mode is a compromise proposal combined with the advantages of the other two control modes,which makes the control strategy relatively simple and easy to implement,and improves the fault current cut speed,and reduces the pressure of freewheeling thyristors.