Analysis of Reactive Power Output Increment Characteristics of the Condenser in UHVDC Converter Station

Condensers are installed in the UHVDC converter station to avoid commutation failure. When a short-circuit fault occurs in the system, the condenser will emit a large amount of instantaneous reactive power and raise the voltage of the bus voltage on the inverter side, which helps avoid continuous commutation failure. Therefore, it is very important to estimate the instantaneous reactive power capability of the condenser. Firstly, the calculation equation of the reactive power output increment of the condenser is derived. Compared with the general instantaneous reactive power formula, the equation given in this paper contains the initial operating state of the condenser, the short-circuit ratio (SCR) of the AC / DC system, and the electromagnetic parameters of both condenser and transformer. Secondly, the influence of the parameters of the AC/DC system and the condenser on the reactive power output increment is analyzed. Finally, through the analysis of the reactive power output increment capacity of the condenser, a scheme to maximize the support capacity of the condenser to the power grid is obtained.