Extreme Survival Method of Urban Distribution System under Extreme Event Considering Frequency Security Constraints

The urban grid has a high proportion of external power recipients, and the connectivity failure of the urban upper grid transmission channel due to extreme events may trigger a major power outage. In this extreme scenario, this paper proposes an extreme survival method for strong urban distribution system considering dynamic frequency security, which can achieve the extreme survival of important loads. However, the microgrid has large transient frequency fluctuations under sudden power shortage, which directly affects the success or failure of self-organised operation to preserve supply. Firstly, a frequency response model of urban distribution system considering the frequency response characteristics of asynchronous motor is established to describe the frequency dynamic characteristics of urban local grid under large disturbances; then, an optimization decision model for extreme survival of urban local grid is constructed, with the objective of minimizing the cost of load control, and the constraints include the dynamic frequency safety constraints in the process of extreme survival and the steady-state operation constraints after entering the islanding operation. The emergency frequency control strategy and asynchronous motor cut-off states are obtained by solving a mixed-integer linear programming model to coordinate multiple FM resources and minimise load-shedding while ensuring frequency security, which can be efficiently solved using a mature commercial solver. Finally, the effectiveness of the proposed emergency frequency control strategy for urban distribution system is verified by case simulation analysis.