Research On Control System For Doubly Fed Wind Generation Based On PSCAD/EMDTC

With the improvement of human life, electricity has been an indispensable part of our daily activities, to the city traffic as well as defense, small to daily life light, electromagnetic oven, freezer, electric has penetrated into all aspects of life. However, with the increasing of electricity demand and reducing of coal and other raw materials, energy shortage is becoming more and more severely, the development and utilization new energy has become urgent need.In the development of all kinds of renewable and new resources, the wind power generation has the great potential of scale production, the commercial development prospect, the largest commercial development conditions, the perfect conditions for development, the most flexible operation, the most mature development, the lowest damaging of environment, the fastest speed at reducing the development cost.At the same time, compared with other power sources,wind energy is really inexhaustible and renewable。Countries around the world have all attached great importance to invest in wind power industry. The governments establish R&D departments in succession and strive to constantly innovate on the technology.With the maturation of development technology for the large-scaled cut-in wind turbine generator, the installed capacity of wind power generator has continued to increase, how to make maximum use of wind energy and improve operational efficiency of the system have become the hot issues.As the rotor speed cannot vary with the speed of the wind in constant speed constant frequency wind power system, the system cannot make maximum use of wind energy.So, since the1990s, wind power generation has experienced from constant speed constant frequency technology to variable speed constant frequency technology. As the rotor speed could vary with the speed of the wind in variable speed constant frequency wind power system, the system makes maximum use of wind energy, increasing the efficiency of wind energy.First, this paper analyses equivalent circuit of doubly fed generator, derives Its math model, deduces the power transfer of doubly fed generator in sub-synchronous、super-synchronous、synchronous operating conditions, then analyses control strategies for back-to-back PWM converter in d-q coordinate system.Finally, based on PSCAD/EMDTC software, this paper constructs simulation models of variable speed constant frequency wind power system, validates the performance of control strategy for variable speed constant frequency wind power system.The result of simulation proves that the stator flux-oriented vector control strategy for the rotor side converter can realize de-coupled control of active and reactive power.The source-side converter of the DFIG maintains effectively the voltage of DC bus and regulates valid the power factor of source side by adopting grid voltage oriented vector control strategy. The result of simulation proves rationality and efficiency of the proposed method.