Research on Emergency Frequency Control of Urban Local Power Grid Off-grid Process Based on Frequency Response Reduction Model Under Extreme Events

Extreme events may lead to the disconnection of urban local grids from the superior grid, entering an island mode. The significant active power deficit at the moment of disconnection poses a challenge in maintaining the frequency safety of the urban local grid. This paper proposes an emergency frequency control method for the disconnection of urban local grids under extreme events based on a reduced-order frequency response model. Firstly, based on the balanced truncation reduction method, a reduced-order frequency response model of the urban local grid, considering the aggregation of distributed resources, is established by extracting key features of frequency response. Then, a two-stage decision-making method for emergency frequency control during the disconnection process of urban local grids is proposed. The first stage solves the control amount of rapid power control resources to ensure that the frequency does not exceed the limit, and the second stage rapidly decomposes the overall power command value of the distributed resource aggregation based on the priority sorting of resource reliability. Finally, a typical urban local grid case study verifies the accuracy and effectiveness of the proposed model and method.