Feasibility Analysis Of Application Of Superconducting Fault Current Limiters In Renewable Energy Power Grid

At present,the proportion of renewable energy in electric energy sources is increasing.At the same time,an important feature of the development of "smart grid" is the widespread introduction of renewable energy sources,which have multiple power points,single-unit power generation,and multiple parallel power branches using a common bus to supply power to the transmission grid.However,when large-scale renewable energy is utilized,one of the major difficulties faced by power generation and grid connection is that when a power generation branch or transmission line is short-circuited,the voltage of the shared busbar connected to it is drastically reduced,and thus the power supply device loses power supply capability.that is,low voltage ride through.In addition,The rapid development of DC grids provides favorable conditions for a large number of distributed renewable energy power generation to be integrated into regional backbone grids.However,the DC grid has a small damping.Once a shortcircuit fault occurs,it will generate dozens of times of rapidly rising fault current,which will greatly impact the safety of the DC grid.The superconducting current limiter,utilizing the excellent characteristics of superconducting materials,has a low impedance during normal operation,rapidly becomes a high impedance during faults,limits fault current,and matches the grid.It has the characteristics of an ideal current limiter and provides solutions to the grid connection problems of renewable energy.In this paper,the feasibility of the superconducting current limiter in the grid connection of renewable energy will be discussed in three aspects,including analysis of the application of superconducting fault current limiter in renewable energy grid,connecting magnetic shielding type superconducting fault current limiter to the wind in the DFIG to solve low voltage low ride-through and the application of renewable energy into the DC grid with superconducting DC current fault limiter.First,this paper will introduce the types and working principles of superconducting current limiters,the research status of domestic and foreign applications and the prospective application of superconducting current limiters in renewable energy grids.Analysis will show that the superconducting current limiter can effectively prevent the voltage of the grid connected to the renewable energy from falling and the fault current raising.Second,a magnetically shielded superconducting current limiter is proposed to solve the DFIG’s low voltage ride-through problem of grid-connected wind power.The simulation platform was built by MATLAB/Simulink,and the effectiveness of the current limiter to suppress the voltage drop of the terminal and prevent the rotor current from being excessive and so on is verified.Third,it analyzes the application of renewable energy into the DC grid with superconducting DC fault current limiter.Through the analysis of the two-pole short-circuit fault and the performance requirements of the voltage source converter high voltage DC(VSC-HVDC)grid for the current limiter,a solution using magnetic shielded superconducting DC current limiter is proposed.We find that it can effectively suppress the DC fault current rise rate,and can also convert the DC voltage transient process from the underdamped state to the overdamped state to protect the VSC converter.Based on the above research results,a magnetic shielding type superconducting current limiter experimental prototype was designed and fabricated,and a series of experiments were carried out.The experiment proved its limiting effectiveness on the fault current,and it can also reduce the breaking capacity requirement of the DC circuit breaker and provide a certain breaking time margin for DC circuit breaker.