It is no denying fact that energy issue emerging with the associated problems, such as a worldwide food crisis, becomes a more and more important problem and needs an immediate settlement. Utilizing clean and cheap resources is an excellent and alternate way of alleviating the huge and increasing energy demand. Wind energy is such a kind of resources. According to the European union report, the electricity demand will increase by 12% expected before Year 2020[1]. With the development of the power electronics technology, the variable speed constant frequency(VSCF) generation system is capable of tracking the maximum power point, and becomes the main trend nowadays. Meanwhile,the costs deduction and the performance enhancements of the magnetic materials make the wind energy conversion system (WECS) equipped with the permanent magnet synchronous generator (PMSG) a focus in recent years.Conventional power electronic components applied in the WECS comprise of uncontrollable AC/DC/AC converters, back-to-back voltage-source converter, and a cost-efficient power converter, which is composed of a uncontrollable rectifier, a boost loop between it and an inverter.
    Matrix converter is a kind of green and AC/AC power electronics device with the features such as the compact size and the absence of the bulky energy storage device.Multi-polar permanent synchronous generator with the elimination of the heavy gearbox is energy efficient in small size.As a result,the integration of the matrix converter and the PMSG is the best choice under some special circumstances.
    Maximum power point tracking (MPPT) is one of the basic problems to the WECS and it is the basic feature of ariable speed constant frequency generation, another problem is the efficiency of generation system. In essence, the two problems belong to the same one. In this paper, a hill-climb and bisection method based sensorless maximum power point tracking approach is presented in the paper. Additionally, the maximum efficiency control of PMSG is also concerned. Meanwhile, a particle swarm optimization (PSO) algorithm based optimal and robust PID control is explored to achieve a better dynamic response.
    The whole system is composed of a wind turbine, an indirect matrix converter, an input filter, and the power grid. As shown in Fig, the PMSG is directly driven by the wind turbine without the bulky and heavy gearbox. The inverter side of the indirect matrix converter is connected to the PMSG, while the rectifier of matrix converter is connected to the power grid via an input filter, which is used to filter the harmonics caused by the matrix converter. The reason why such a configuration is adopted is that the control the PMSG is much easier than the scheme presented in and more degrees of freedom could be utilized efficiently.

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