Commutation Failure Control Strategy of UHVDC Transmission Considering Initial Fault Angle

[Purposes] Commutation failure (CF) is one of the common faults in the line-commutated converter-based Ultra-high Voltage Direct Current (LCC-UHVDC). In order to reduce the probability of CF in DC transmission, a lot of research on CF control strategies have been carried out. At present, the CF prevention control (CFPREV) strategy is widely used. It is found that this control strategy is easily affected by the initial fault angle, so that the trigger angle cannot be triggered in time under certain fault conditions, which leads to CF. [Methods] On the basis of CFPREV, a CF prevention and control strategy for UHVDC transmission considering initial fault angle was proposed. Pearson coefficient was used to reflect the change of dissipated energy waveform before and after fault in real time, which can improve the starting speed of CFPREV and avoid CF to a certain extent. [Results] The effectiveness of the suggested suppression strategy has been confirmed by the simulation results of a UHVDC transmission system constructed in MATLAB/SIMULINK.