Study Of Short Circuit Fault Limiter Based On The Natural Current Conversion Of Rectified Capacitor Current

With the expansion of the power grid,the short-circuit current value is also increasing.It may cause switch equipment can't open normally.So how to limit short circuit current becomes the problem that the society needs to solve urgently.Although the current limiting measures can reduce the short-circuit current value varying degrees,it can also bring about other negative effects.With the rapid development of science and technology,fault current limiter(FCL)becomes the research focus of the researchers at home and abroad because of its superior current limiting characteristics,the future will be very promising.The current limiting principle of various limiters is briefly introduced.On the basis of summarizing the previous research experience,this paper puts forward a kind of short circuit fault limiter based on the natural current conversion of rectified capacitor current.The FCL makes the fast switch,current-limiting reactor and full-bridge rectifier capacitor charging circuit connecting in parallel.When the power grid is running normally,the fast switch is in closing,and FCL is equivalent to short circuit,which has no effect on the safe operation of the power grid.When short circuit fault occurs,the fast switch opens rapidly,and the FCL quickly appears in a high impedance state to limit flow.Firstly,the topological structure of short circuit fault limiter is established and the feasibility is estimated by theoretical analysis.And then,the current limiting process is analyzed by derivation of equations in detail.With the basis of above theory,the simulation experiments were carried out of verifying the current-limiting performance by MATLAB/SIMULINK.The results show that the current limiting effect is excellent and there is less harmonic,etc.A new calculation method and design flow for a new kind of forward thrust is proposed for the fast mechanical switch based on electromagnetic repulsion principle.And Jointly simulating by that large finite element simulation software Ansoft Maxwell and its own Maxwell Circuit Editor.The experimental results show that the design method can meet the requirement of fast switching in the FCL.The effect of the new FCL on the breaking performance of circuit breaker in power system is studied.The effect of the new FCL on the breaking performance of circuit breaker in power system is studied.Firstly,the general formula of the transient recovery voltage(RRRV)of the circuit breaker for terminal fault and short-line fault is derived.Then to verify the results by MATLAB/SIMULINK.The results show that the limit ratio,stray capacitance and fault segment line distance can affect RRRV in different degree.In order to verify the accuracy of the previous simulation results,a small capacity prototype experiment was designed for the new FCL,and the short-circuit process was simulated by LC oscillation.The results show that the experimental results are consistent with the simulation results,and the feasibility of the new FCL is verified.