Approximation-Based Optimization of Distribution Network Operation Considering Coupled Voltage Stability

With the growing penetration of distributed generation (DG), the uncertainty of power output, frequent multi-node disturbances, and evolving network topology have increased the risk of voltage instability in distribution networks. To address this issue from the perspective of voltage stability, this paper proposes an approximation-based improved optimization method for distribution network operation considering coupled voltage stability. First, a Node-Coupled Voltage Stability Index (NCVSI) is introduced to quantitatively characterize the voltage stability of distribution networks under multi-disturbance coupling scenarios. Then, the stochastic characteristics of power flow input variables are modeled using a Gaussian Mixture Model (GMM), and the Unscented Transform (UT) is employed to derive the probability density function of the coupled voltage stability index. Based on this, a tractable joint chance-constrained model for voltage stability is established. Finally, the proposed method is validated on the IEEE 123-bus distribution system. The simulation results demonstrate the effectiveness of the approximation-based coupled voltage stability optimization approach.