An optimum speed MPPT controller for variable speed PMSG wind energy conversion systems

A maximum power point tracking (MPPT) controller for variable speed permanent magnet synchronous generator (PMSG) wind energy conversion systems (WECS) is proposed. The proposed controller, without requiring the knowledge of wind speed, generates at its output, the optimum speed (OS) reference signal for the speed control loop of the vector controlled machine side converter control system, thus, allowing maximum power extraction. Optimum speed - power curve of the WECS, used by the controller, takes into account the changes in system efficiency while operating at different operating points due to the change in wind speed. The method proposed is based on the fact that the optimum output power of a WECS at a certain wind speed depends upon the total mechanical power developed by the turbine and efficiency of the WECS at the corresponding OS of rotation of the turbine. The controller requires the active power and air density as its inputs to generate optimum reference speed. The proposed controller is validated experimentally in a variable speed direct drive PMSG WECS using a wind turbine emulator.