Control And Design Of A Doubly Fed Induction Generator Analysis

Abstract- This paper describes the control and design of a Doubly Fed Induction Generator (DFIG) using back-to-back PWM converter in wind turbines. A back-to-back PWM converter is used as the excitation power supply for the DFIG wind power generation of variable speed constant frequency. The Simulink model and control strategy of converter which is connected to grid side is analyzed. The grid side converter is used to regulate the voltage of the DC link capacitor. Besides it satisfies the unity power factor of grid-side and bi-direction flowing ability of energy. The control model of whole system is built using Matlab/Simulink program. The proposed control structure achieved the fastest and robust dynamic response without stressing the converters or deteriorating the
The main purpose of the grid side converter (GSC) is to maintain the voltage level on the dc bus capacitor by exchanging active power with the grid. It also has the ability to control terminal voltage or power factor by exchanging reactive power with the grid.
Running on different operating conditions, the rotor of DFIG has different energy flow directions. Although energy always flows from stator to grid, sub-synchronous operating state, the energy flows from the grid to the rotor; super-synchronous operating state, the energy flows in an opposite way. Therefore, in order to make the system run in a wide speed range, it has to ensure that the rotor energy can flow in double-way. This process is achieved with GSC by regulating the stability of the DC voltage.
In this paper, the complete mathematic model of the GSC is obtained and controlled with two level pwm controller. The model is developed on the synchronously rotating, voltage oriented and dq reference frame since in this frame all the sinusoidal quantities are transformed into dc quantities in steady-state. GSC MATHEMTIC