Generator Dynamic Response During Total and Partial De-blocking of a Bipolar MTDC System

This paper analysed the operational issues associated with MTDC systems incorporated in an AC network. It presents the dynamic modelling of a line-commutated converter based bipolar multiterminal direct current (LCC MTDC) system combined with the dynamic response of a synchronous generator during a dc converter fault. The converter controller design for both rectifiers and the inverters system was modelled for a realistic active power and extinction angle (γ) control with consideration to the VI characteristics of all the converter stations. An overall current (Idc) sharing coordination was modelled for both converter pole. Two operational scenarios of converter fault were investigated using PSCAD. The active power transfer at the rectifier station was decreased during the fault condition to allow minimum rated power across the link. After the fault, the synchronous speed of the generator during the total deblocking stage recorded a continuous increase while the result during partial converter deblocking showed a reduced converter oscillation and a stable post-fault condition.