Research On TRV Transient Characteristics Of Controllable Series Compensation Lines Equipped With Compound FCL

In recent years,in order to solve the problem of limited transmission capacity of transmission channels in large energy bases in China,series compensation devices are widely used in EHV lines.However,with the increase of series compensation capacitance reactance and line transmission capacity,the electromagnetic transient process excited by EHV series compensation line when fault occurs and clears becomes more intense,and the harm of electromagnetic transient problems such as overvoltage rises.With the development of electrical technology,multifunctional compound fault current limiter(FCL)provides a new idea to solve the problem of series compensation.In case of line fault,the composite FCL quickly switches the current limiting mode based on the action characteristics of fast switch,suppresses the peak value of short-circuit current and reduces the residual voltage of series compensation capacitor.Based on the 500 k V Dehong-Boshan-Mojiang AC transmission line,the action characteristics of the circuit breaker are analyzed when the series compensation line fails,and establishes the simulation model of controllable series compensation device and composite FCL based on PSCAD.The influence of hybrid multiplexing of TCSC and fixed series compensation(FSC)on transient recovery voltage(TRV)is studied.In order to solve the problem of TRV amplitude increase caused by capacitor residual voltage after TCSC is installed on the line,the suppression scheme of optimizing series compensation configuration and composite FCL instead of FSC is proposed.Aiming at the most severe working condition of TRV,the TRV suppression effect of opening resistance on the secondary disconnection of circuit breaker caused by permanent fault of series compensation line is studied,so as to provide a technical scheme for the reliable disconnection of circuit breaker in the application scenario of EHV TCSC.The main research work and innovative achievements are as follows:(1)Based on the EHV demonstration project line,the equivalent mathematical model of TCSC is constructed.Based on the thyristor pulse trigger principle,the steady-state power frequency characteristics of TCR branch are analyzed,and the influence of TCR Dynamic Characteristics on TCSC under steady-state operation conditions is studied.According to the actual action characteristics of fast switch,the equivalent mathematical model of compound FCL is established,and the variation trend of TRV peak in five stages of TCSC under FCL series harmonic mode is analyzed.(2)Based on the limiting factors of line operation,the configuration of series compensation is determined,and the generation mechanism of TRV of EHV series compensation line is revealed.The influence of fault parameters on the electromagnetic transient of circuit breaker is studied,the macro distribution characteristics of TRV peak are summarized,and the influence mechanism of capacitor residual voltage on TRV peak in case of single-phase grounding fault at the back of series compensation station is analyzed.The influence of hybrid multiplexing of TCSC and FSC on TRV peak value is studied,and the variation characteristics of TRV,RRRV and short-circuit current under different series compensation are studied according to practical engineering application.(3)The generation mechanism of circuit breaker TRV under composite FCL series compensation mode is analyzed.Based on the fast switching action after line fault,the action characteristics of composite FCL to improve line impedance are analyzed,and the effects of installation position and fast switching action time on TRV and RRRV are studied.The simulation research scheme of composite FCL replacing FSC is proposed to statistically study the distribution characteristics of TRV and RRRV when the series compensation is different,and verify the feasibility of FCL replacing fixed series compensation.(4)The electromagnetic transient characteristics of the circuit breaker are studied when a permanent fault occurs in the controllable series compensation line with FCL,and after the secondary disconnection of EHV series compensation line,the inhibition mechanism of opening resistance on TRV is revealed.Based on the changes of circuit breaker twice action time and reclosing time,the change trend of TRV peak value is analyzed,the influence of opening resistance on reclosing time setting and TRV is evaluated,and the installation scheme of opening resistance which can effectively suppress TRV peak value is proposed.