1.Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology, Ministry of Education (Northeast Electric Power University), Jilin 132012, China;2.State Grid Electric Power Research Institute (NARI Group Corporation), Nanjing 211106, China

The major power outages abroad show that a large number of different renewable energy sources may experience coexistence scenarios of low voltage ride-through (LVRT) and off-grid after disturbance, presenting complex nonlinear dynamic changes in the overall power impact on the system, and making transient frequency trajectory prediction increasingly difficult. The existing frequency trajectory prediction and analysis methods usually only consider single disturbance such as LVRT or off-grid, and lack practical and feasible engineering application schemes, making it difficult to carry out early warning or pre-control for frequency insecure scenarios. Therefore, this paper firstly analyzes the mechanism of the difference in active power restoration caused by the distribution characteristics of wind power output during the LVRT process and its impact on the system power shock. Secondly, considering various forms of power disturbances such as step and non-step, a power grid frequency response model that takes into account the coexistence of LVRT complex restoration and off-grid of wind power is proposed. Then, an engineering application scheme based on “offline grading modeling, online fast prediction, and critical additional verification” is proposed. Finally, the effectiveness and practicality of the proposed model and method are verified through the New England 10-machine 39-bus test system and an actual power grid case simulation.