Dynamic Equivalence And Parameter Identification For The Doubly-fed Wind Farm

In recent years, large scale of wind turbines escape from the grid frequently, attracting the attention of scholars. It needs to establish an effective wind farm dynamic equivalence model for large-scale power system calculations. In this paper, the doubly fed induction generator(DFIG) system is the object for the study,with depth study of the dynamic equivalence and parameter identification and other related issues. The main work are as follows:(1) Using the modal analysis method, the dynamic model of DFIG is analysed.By the modal analysis of 15 order wind turbine model, operating states, reduction, control parameter changes and other factors is discussed. Dynamic model is proposed for doubly-fed wind farms to meet the stability analysis and simulation needs time.(2)With the analysis multiple factors on DFIG transient performance, dynamic equivalence strategies of wind farms considering a combination of factors is proposed.For the clustering and dynamic equivalence problem of doubly-fed wind farm units, a comprehensive discuss of the impact of the wake, terrain, control strategy, the initial operating point, the voltage drop size and other factors on the double-fed wind turbine clustering and dynamic equivalent is presented. And a reasonable grouping criterion is proposed. Compared with traditional equivalent methods, the criterion can more accurately approximate the wind turbines responsing with triggering different control strategies, and quite different steady-state operating points.(3)Based on the theory of DFIG parameter identification, the equivalent controller parameters of doubly-fed wind farm are obtianed.The effects of single and dual mass model of double-fed wind turbine drive system on parameter identification are compared. The effects on the resistances and inductances identification of the 2nd order and 4th order generator model are discussed. The method of obtaining the equivalent controller parameters of doubly-fed wind farm is presented, and the parameter identification of doubly-fed wind farm is achieved.(4)Analyze the characteristics of the DFIG equivalent inertia time constant.Analogous to the synchronous generator inertia time constant, the concept of the variable equivalent inertia time constant of DFIG is proposed. The impact of the operating state, the degree of fault, the control parameters and other factors on the equivalent inertia time constant is analyze. The results show that the equivalent inertia time constant is much smaller than the rotor time constant.