Study On The Stability Of Power Grid With Large-scale Wind Farms

In recent years, with the development of wind power, the wind power penetration is increasing rapidly, the impact of wind power on the grid stability is becoming more and more prominent, combined with the dynamic characteristics and control technology of wind turbines are very different with conventional synchronous generators. Therefore, this paper will study on the stability of the grid connected with large-scale wind farm. The main research content includes both voltage stability and power angle stability, summary of work are as follows:(1) The mathematical model of doubly-fed wind power generator system is introduced in this paper, mainly including air power system model, shaft model, doubly-fed induction generator model, the converter control model and pitch angle control model;The principle of active and reactive power decoupling control of doubly-fed wind power generator is derived and the corresponding control model is established;The control model of doubly-fed wind power generation system is built in DIgsilent/PowerFactory.(2) To solve the impact of wind power on power system voltage stability, a reactive power and voltage coordinated control strategy can enhance the operation safety of doubly-fed wind farm is put forward, on the basis of the analysis of the typical radial collector system voltage distribution characteristics. The control strategy can equalize voltage reserves and increase the dynamic reactive power reserve capacity of wind farm in steady state, which can prevent wind turbines chain off network effectively and improve the safety of wind farm during the power grid voltage disturbance or failure. The control strategy can improve the low voltage ride through ability of doubly-fed wind farm power during failure by dynamic reactive power compensation. The simulation of a practical example verifies the effectiveness and feasibility of the proposed control strategy.(3) To solve the impact of wind power on grid power angle stability, a dynamic stability control strategy of grid connected with wind farms based on oscillation energy consumption is put forward. Firstly, the relationship between oscillation energy and transient energy is studied on the basis of energy conservation law. Further, based on the main line of oscillation energy, a dynamic stability control strategy aimed at oscillation energy consumption is presented. Finally, by the simulation we can see that, the control strategy storages can dissipate transient energy by making use of the DFIG fast active and reactive power regulation characteristic, improving the dynamic response of the system.