Research On Equivalent Modelling Of Wind Farms And Transient Operational Performances

With large-scale wind farms in the planning, construction and operation, the penetration of wind power in electrical power systems gradually increases, the interactions between large-scale wind farms and the connected power systems will be obvious. It is extremely important to study the principles of interactions and the influences between a large-scale wind farm and the grid. On the one hand, it is considered that the influence of wind power fluctuation on the stability of the grid. On the other hand, the effect of the power system faults on the wind turbines systems is also considered. Hence, the equivalent modelling of a large-scale wind farm is the base to study the transient behaviors between the grid and the wind farm.This thesis mainly focuses on the a large-scale wind farm including wind turbines with squirrel cage induction generators (SCIG) and doubly fed induction generators (DFIG), aim at the equivalent modelling of a wind farm and at the transient operational performances of the mixed wind farm composing of different wind turbine generator systems. Firstly, the operational principles and the control strategies of a SCIG wind turbine and a DFIG wind turbine are presented.The mathematics models of the two wind turbine generator systems are established, respectively. The dynamic characteristics have been simulated and analyzed. Secondly, the different traditional equivalent method of a wind farm, such as the weighted equivalent method, the modified weighted method, the parameter transformed method, and the reduced-order re-scaled method are introduced and the corresponding models are established. Regarding the wind turbine generator system with identical and different parameters in a SCIG wind farm and a DFIG wind farm, the dynamic characteristics and transient operational performances of a wind farm with the presented equivalent models are analyzed. Thirdly, an equivalent method and dynamic parameters optimal model of a SCIG wind farm is proposed based-on genetic algorithm by utilizing the sampling power values in the SCIG wind farm using detail model.And then the dynamic characteristics and transient operational performances of the equivalent model are analyzed. Finally, based on the presented equivalent models of a wind farm, object of studying different wind farms connected the grid by infinite bus. The transient operational performances of the mixed wind farm have been analyzed from the views points of the wind farm with the different capacitance ratios, var compensated equipment, the ratios of short circuit capacity, the impedance ratios of the contact line to the grid.The obtained different equivalent methods and models of wind farms, and the obtained conclusions of transient operational performances of a mixed winds farm including a SCIG and DFIG wind farm will provide some theoretical references and decision supports for safety and stability analysis of the power system with a large-scale wind farm.