Bi-Objective Reactive Power Reserve Optimization to Coordinate Long- and Short-Term Voltage Stability

Reactive power reserve (RPR) management is a critical issue to power system voltage stability. Two RPR definitions are first proposed in this paper to evaluate the levels of RPR and improve voltage stability, namely long-term voltage stability-related RPR (LVRPR) and short-term voltage stability-related RPR (SVRPR). Both definitions consider two factors: 1) the RPR of each online generator and 2) the relative contribution of the RPR to voltage stability varying with location and scenario. For LVRPR, the generator participation factor is used to describe the contributions of RPR. For SVRPR, an voltage support coefficient considering the generator's dynamics is proposed to evaluate the RPR's contribution. In normal condition, short-term voltage stability is expected to be improved by the optimization of SVRPR, ensuring enough longterm voltage stability margin. A bi-objective optimization model that coordinates LVRPR and SVRPR is formulated to enhance longand short-term voltage stabilities simultaneously. The proposed model is solved using the normal boundary intersection technique. The proposed method is performed using an IEEE39-bus system, and the results show that the optimal solution improves both longand short-term voltage stabilities by optimizing the trade-off between LVRPR and SVRPR.