Fault location method for hybrid MTDC system based on LCC signal injection strategy

A fault location method based on line commutation converter (LCC) signal injection strategy for hybrid multi-terminal direct current (MTDC) system is proposed to deter-mine the fault location after the permanent fault occurs and facilitate the line inspection and maintenance by the staff. Firstly, using the fault control ability of LCC, the additional control strategy is applied to the trigger angle of LCC to realize signal injection. The frequency, duration and amplitude of the injection signal are analyzed and determined, and a signal injection strategy based on LCC is proposed. Secondly, In the injection signal mode, the fault location equations for pole to ground fault and pole to pole fault in the distributed parameter model are derived respectively. The hyperbolic function in the fault location equation is replaced by Taylor series, and the multi order fault location equation is written. Using Ferrari method to solve the analytical solution of fault location equation to realize fault location. PSCAD/EMTDC simulation results show that the proposed fault location method only uses single terminal data, the location error is less than 1%, has high location accuracy. It can withstand 400 Ω fault resistance and 40 dB noise interference, and does not have the problem of iterative convergence.