With increasing the penetration level of renewable energy resources in power systems, impacts of these resources in steady-state and dynamic analysis of power systems interest engineers and researchers in the field of power engineering. Currently, wind energy in terms of installed capacity is the dominant source of renewable energies. Wind farms use a modular structure that include ample of wind-turbine generators (WTGs) which are connected to a grid. Using detailed model for each WTG unit will provide a complex dynamic model for a wind farm with hundreds of WTGs. Conventional method for modeling and analysis of a wind farm is to define an aggregated model that includes one or a few equivalent WTG units for different zones in the wind farm. This thesis deals with developing aggregated model for analysis of wind farms with fixed-speed WTGs. The thesis presents a method for developing an aggregated model of a wind farm useful for the steady-state and dynamic analyses. To this end, firstly the existing method for developing the aggregated models are investigated and their accuracy and performance in a dynamic analysis are investigated using a few test systems. Then, a modelling method based on weighted summation of the frequency response of the all WTGs is suggested which provide an aggregated model for a wind farm. The proposed method uses the dynamic model of the generators in the synchronous reference frame to develop the model of WTGs in a wind farm. Then, the equivalent model of the wind farm is obtained using the model of each WTGs considering its participation to generate total wind power as a weighting factor to develop the aggregated model. It is assumed that the aggregated model of the wind farm is similar to that of a single WTG in which the equivalent parameters of the model are obtained based on the best matching of the frequency response of the wind farm with the proposed model. Similarly, an equivalent turbine for the mechanical parts of the WTGs is presented by defining the impact factors of WTGs at a given operating point. To evaluate the performance and accuracy of the proposed method, a test system with two wind turbine- generators is used under four different test conditions. Then, its aggregated model is obtained using the existing and proposed methods. Then, the steady-state and dynamic behaviors of the test wind farm system is simulated under different test conditions and the test results are compared with those of obtained based on the conventional and the proposed aggregated models. It is shown that the proposed method especially when the wind speeds and the parameters of WTGs in a wind farm are different, provides more accurate test results compared with existing methods where its error is less than 0.75% in the steady-state and 2.75% in transient tests.
