A HEM-Based Sensitivity Analysis Method for Fast Voltage Stability Assessment in Distribution Power Network

The increased penetration of distributed energy resource and power electronics-based loads cause rapid voltage fluctuations in distribution power networks, affecting secure operation of the grid and threatening high-quality power delivery to customers. It is of great importance to conduct fast and accurate voltage stability assessment for better understanding operational risks and providing effective and timely controls for mitigating the identified risks. Traditionally, Jacobian matrix-based sensitivity analysis methods are used to evaluate voltage stability, however they suffer from ill-conditioned load flow problem caused by numerical stability. To effectively resolve this issue, this paper presents a novel Holomorphic embedding method (HEM)-based approach that can effectively capture sensitivity information for stressed operating conditions when the load flow calculation becomes ill-conditioned. An effective criterion is also proposed to approximate voltage instability point using structural and partial sensitivity information with different orders. The effectiveness of the proposed method is verified via numerical simulations conducted on the IEEE 33-bus and 69-bus test systems.