Improvement Method of Commutation Failure Predictive Control Based on Voltage Waveform Fitting

Commutation failure is one of the common faults in HVDC transmission system. Out of the purpose of suppress the commutation failure of HVDC transmission system, the commutation failure predictive control (CFPREV) is adopted in HVDC control system. However, there is a lack of theoretical basis for setting the starting value of this link in DC projects. In some cases, the detection method has the problem of slow fault identification, which can not meet the requirements of system adjustment. Based on CFPREV, an improved commutation failure predictive control method based on voltage waveform fitting is proposed in this paper. Firstly, the method calculates the maximum value of zero sequence voltage by using the three-point method of voltage waveform fitting and three-phase voltage after Clark transformation in the first period under the fault to determine the severity of the DC system fault; Secondly, the voltage amplitude in the first period after the fault is taken as the reference and multiplied by a certain coefficient as the starting value of the predictive control of commutation failure, which is used to realize the adaptive setting of the starting value of the predictive control of commutation failure in different fault scenarios; Finally, based on CIGRE standard test model, the improved method is verified in PSCAD. The results show that the improved method can quickly respond to the commutation failure and restrain the initial commutation failure at a certain level.