Transient Stability Analysis Of Wind-thermal Bundled System

Wind-thermal bundled system is an effective way to solve the "bottleneck" of power dissipation in "three north" areas.However,large-scale wind and thermal power transmission by "wind-fire bundled" has changed the transient stability characteristics of the system to a certain extent.In recent years,wind turbines gradually require inertia support capability,and the application of virtual inertia additional control is gradually popularized,which undoubtedly makes it possible,that transient stability of "wind-fire bundled" system will be more complex.Therefore,it is particularly important to study the wind-fire ratio and virtual inertia additional control for the transient stability of the " wind-fire bundled " delivery system,which will help to improve the wind power absorption capacity of the system and reduce the rate of wind abandonment.In order to study the transient stability of the "wind-fire bundling" delivery system,this paper studies the wind-fire ratio and the virtual inertia additional control respectively.The main work is as follows:Firstly,the typical wind-fire bundled system is modeled in this paper.Doubly-fed wind turbines are considered as wind turbines.The stator flux transient is neglected in the generator model,but only the rotor flux transient is considered.The fifth-order practical model is adopted for synchronous generators.The model can accurately simulate the response characteristics of the system during the fault,and reduce the order of the model as much as possible.Then,the EEAC rule(Extended Equal Area Criterion)is used to analyze the influence mechanism of wind-fire ratio on transient stability of "wind-fire bundled"delivery system.The research shows that if the receiving end is infinite system,the increase of wind power can reduce the equivalent acceleration area of the system,so the access of wind power is beneficial to the transient stability of the system;but if the receiving end is not infinite system,the transient of the system.Stability is affected not only by the acceleration area but also by the inertia of the system.It is found that with the increase of the proportion of wind power,the transient stability of the system increases first and then decreases.That is to say,there exists an optimal ratio to make the transient stability of the system the best.In this paper,the typical"wind-fire bundled" systems with infinite bus system and non-infinite bus system are simulated and validated respectively.Finally,the actual situation of Heilongjiang grid is simulated and analyzed.Finally,the principle and control structure of virtual inertia additional control strategy are studied,and the influence mechanism of virtual inertia additional control on transient stability of "wind-fire bundled" transmission system is analyzed by using EEAC rule.The simulation of power grid fault and wind speed disturbance in IEEE four-machine two-zone system and Heilongjiang actual power grid is carried out to verify the correctness of mechanism analysis.The theoretical and simulation analysis shows that if the receiving end is a non-infinite system,the virtual inertia additional control can effectively enhance the transient stability of the system,and when wind speed disturbance occurs,the virtual inertia additional control can restrain the fluctuation of the output of the fan;when the receiving end is an infinite system,whether the fan adopts the virtual inertia additional control has little effect on the power angle stability of the system.However,when wind speed disturbance occurs,the additional control of virtual inertia can effectively suppress the fluctuation of fan output.