Research On The Impact Of Wind Energy On Electric Power Network

With the increasing severity of energy and environment problems, renewable energy is competitively developed all over the world. Wind energy, which is clean and abundant, is attached great importance to and becomes the fastest developing renewable energy. As the rating of wind power in power network rises, the large wind farms often reach several hundred MW. Unlike the other power plants, the active power from wind farms varies all the time, which may influence the operation and stability of power network after connection. As a result, the impact of wind power on power system should be analyzed in detail. This thesis focuses on the following aspects:First, the reserve and structure of energy in China are analyzed, and the necessity of renewable energy development is explained. With the introduction of the history and development of wind power all over the world, the factors that influence the development of wind energy are pointed out. Then several advanced packages for wind power analysis are introduced. In Chapter 2, the principle of wind energy generation is analyzed in detail, while the structure of wind turbine systems is modeled, including the wind model, wind wheel model, the power control strategy, the drive model, etc. Also, the models of induction generator, synchronization generator and converter are simply introduced. In Chapter 3, eight structures of wind turbine systems and their characters are discussed, among which three most widely used wind turbines are analyzed in detail and compared. The "fixed pitch induction generator" model is simulated and analyzed using PSCAD/EMTDC. Chapter 4 discusses the advantages and disadvantages of onshore and offshore wind farms with comparison. The ways to select wind farm location and to arrange wind turbines are also proposed. And then, three connection methods between wind farms and power network are given, including AC/AC, AC/DC and DC/DC. At last, an equivalent model of wind farm for power system analysis is modelled.In Chapter 5, with several cases, the principle of the impact of wind energy on power network is analyzed, including voltage variation, the change of short-circuit current, the influence on power losses, flicker, etc, using PSCAD/EMTDC. The causes and rules of the impacts are concluded.