Direct-drive low-speed wind energy conversion system incorporating axial-type permanent magnet generator and Z-source inverter with sensorless maximum power point tracking controller

With the ever increasing concern on environmental pollution and energy crisis, generation of power from wind is developing very fast. In the proposed wind energy conversion system (WECS), a variable-speed wind turbine, axial-type permanent magnet generator (PMG), Z-source inverter (ZSI) and sensorless maximum power point tracking (MPPT) controller are included. Although the conventional-type induction generator has the advantage of robust construction and maintenance-free operation, it has drawbacks like low-power factor and need for an ac excitation source which is overcome by the PMG. To obtain fixed voltage and frequency, PMG-generated voltage is fed to power converters. Conventionally the three stages of power conversion consist of rectifier, boost chopper and pulse-width-modulated inverter which reduce the efficiency, power quality and reliability of the overall WECS. To overcome these barriers of conventional system a two-stage-based direct-drive WECS is proposed. The maximum power point for each speed is traced using sensorless MPPT controller, which estimates the rotor speed, by using a simple sensorless speed estimator which is given as the input to the MPPT controller. The proposed sensorless MPPT controller for direct-drive WECS along with the ZSI is simulated in MATLAB/SIMULINK and the results are compared with experimental setup.