Variable Structure Direct Torque Control and grid connected for wind energy conversion system based on the PMSG

This study proposes a novel Variable Structure Direct Torque Control (VS-DTC) scheme for Wind Farm (WF) based on the Permanent Magnet Synchronous Generators (PMSGs) in order to maximize the generated power from wind turbines. The 30KW wind farm consists of 3 PMSGs based 10KW generators connected to a common DC-bus. Each generator of the farm is connected to the DC-bus through a rectifier, but the DC-bus is connected to the grid through only one DC/AC inverter. The efficiency of the variable speed farm can be greatly improved using an appropriate control strategy. In addition, WF has strong nonlinear multivariable with many uncertain factors and disturbances. Consequently, the control strategy combines the technique of DTC and Sliding Mode (SM) nonlinear control theory. Considering the variation of wind speed, the PMSGs side converters are used to achieve Maximum Power Point Tracking (MPPT), while the grid-side converter regulates DC-link voltage, injects the generated power into the AC network and it´s used to achieve unity power factor. The employed control strategy provides an optimal control solution for wind farm systems based on the PMSG.