An efficient variable-step P&O maximum power point tracking technique for grid-connected wind energy conversion system

This paper proposes an efficient modular sector variable-step perturb and observe (VSPO) maximum power point tracking algorithm. The proposed algorithm enhances the speed tracking and minimizes oscillations level problems associated with traditional P&O methods. The routine of generating the variable step sizes depends on splitting the (P–ω) characteristic curve of wind turbines into modular sectors, in which the perturbation step size for each sector is selected by comparing a suggested ratio with another specified ratio designed according to the required accuracy. By continuously observing the distance between the actual rotor speed and the optimal rotor speed, the VSPO technique applies variable perturbation step sizes according to the current operating sector. Moreover, a wind speed estimation technique is used as a replacement of distributed anemometers for tracking the optimal rotor speed at different wind speeds. The studied system configuration includes three-phase back-to-back converter which is used to connect a 1.5 MW permanent magnet synchronous generator into the utility grid. Furthermore, the model predictive control is used for current control loop in the machine-side converter. To demonstrate the performance of the proposed algorithm, its simulation results are compared with the simulation results of conventional P&O technique under step and random wind variations. In addition, the algorithm performance is studied with real wind data (Hokkaido Island, Japan) using MATLAB/SIMULINK environment. Simulation results show that the VSPO ensures the high tracking speed of maximum power point, while the steady-state oscillation is significantly reduced. The proposed algorithm enhances the system efficiency by 3.5% over the conventional one.