Case Analysis of Emergency Control Negative Effect in Frequency-Angle Coupling Problem

An AC fault in the vicinity of a UHVDC cluster within same sending and receiving ends may trigger simultaneous blockings of these multiple UHVDC lines. Implementing emergency control measures such as nearby generator shedding are necessary to address the substantial power surplus in the sending grid of UHVDC. However, prevailing control strategies are formulated with a primary focus on the mitigation of imbalance active power and frequency regulation objectives. However, the potential negative effect of control actions on angle stability has been neglected. With a focus on a specific actual power grid in China, the mechanism of negative effects on angle stability of generator shedding after multi-UHVDC locking faults is analyzed by applying EEAC theory. Building upon this analysis, a strategy for identifying appropriate emergency control measures is proposed based on the ratio of active power output to inertia of generators as a guiding metric.