Reduced Order Modeling of DFIG based on Singular Perturbation Theory

With a large number of renewable energy connected, the penetration rate of grid connected inverter increases rapidly, and the interaction between converter and power grid and between converter and converter becomes more and more intense. The assumption that power grid is regarded as infinite power supply is no longer tenable. And a large number of new energy resource will change the transient instability mode of the power system and increase the risk of security and stability. In the process of simulation, how to establish a reduced order aggregate equivalent model of converter suitable for transient stability simulation becomes an urgent problem to be solved in the research of new energy resource connected. In this paper, based on singular perturbation theory, the reduced order modeling of DFIG (Doubly fed induction generator) converter is carried out. Firstly, according to the typical triggering criteria of DFIG relay protection action in transient stability problem, the modeling principles of relay protection and low voltage ride through behavior are analyzed, so as to accurately simulate the transient instability behavior of generator tripping. Secondly, a combined system of synchronous generator and DFIG wind turbine model is built. Different instability modes are classified by the time period and time scale of instability, and the influence of DFIG power supply on grid voltage instability is analyzed.