There are many solar power and wind stations installed in the power system for environmental and economic reasons. In fact, wind energy is inexpensive and the safest among all sources of renewable energy, it has been recognized that variable speed wind turbine based on the doubly fed induction generator is the most effective with less cost and high power yield. Therefore, this paper has chosen doubly fed induction generator for a comprehensive study of modeling, analyzing, and control. DFIG in wind turbine has to operate below and above the synchronous speed, which requires smooth transition mode change for reliable operation, specially, close to synchronous speed where the DFIGWT instability starts to appear. Furthermore, its output electric power has to be controlled to provide stability for the power system; hence its performance depends on the generator itself and the converter operation and control system. This paper presents completed mathematical model of DFIG with its AC/DC/AC converter driven by DC machine. A new vector control technique is designed and modeled, which allows to evaluate the dynamic performance of the controller under (below, above, and through synchronous speed). The simulation results demonstrate the accuracy and high performance of the new control system of DFIG for wind turbine, which provides smooth transition mode without using any extra circuit. 1. Introduction The electric power generation using wind farms is subject to considerable attention in the world due to the increase of electricity demand and consumption, which led to the depletion of existing energy sources such as fossil fuels, coal, and oil. Furthermore, there are many countries unable to generate hydroelectric power or nuclear energy. Indeed, wind power is environmentally and economically acceptable and the safest source among renewable energy sources [1]. Large wind turbines can be operated at a constant speed or variable speed using different types of generators that can be either directly connected to the network or connected through a power electronic converter. In recent years more development has been carried out to improve the performance of variable speed wind turbines to overcome the problem of the necessity to operate above, below, and through synchronous speed; as the result of this development the wind energy industry ended up with doubly-fed induction generator wind turbine (DFIGWT), which is the most efficient generator in wind energy conversion system so far. In fact, DFIG it is one of the most important generators in high-power applications;
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