Static Voltage Stability Domain and Power Margin for Multi-Infeed DC System During Recovery Process

During the recovery of multi-infeed DC system after blackout, utilizing DC transmission to support the load recovery of receiving AC system can largely speed up the recovery process, but it will increase the challenges of voltage collapse at the same time because of the impactful reactive power consumption of DC. In order to avoid voltage collapse and give the power margin for recovery, this paper proposed the static voltage stability domain method to study the static voltage stability of DC participating in recovery. First, the impact of DC power is taken into account by adding DC power as variable parameters to the continuous power flow algorithm. Second, voltage collapse points are calculated using the improved continuous power flow algorithm to shape the static voltage stability domain. Then, the AC/DC power margin is defined as the shortest distance between operating point of system and the boundary of static voltage stability domain. Finally, the AC/DC power margin is calculated by using the normal of the boundary of static voltage stability domain to amend the power growth direction. The proposed AC/DC power margin can not only evaluate the voltage stability margin of multi-infeed DC system, but also guide the power recovery control. The effectiveness of this proposed method is validated in the test system.