Wind speed estimation based variable speed wind power generation

Abstract

Significant variation of the resource kinetic energy, in the form of wind speed, results in a substantially reduced energy capture in a fixed speed wind turbine. In order to increase the wind energy capture in the turbine, variable speed generation (VSG) strategies have been proposed and implemented. Typically, VSG strategies vary the rotational speed of the turbine, by controlling either a mechanical or electrical parameter to maintain a constant tip-speed ratio of the turbine. This is known as a maximum power point tracking (MPPT) controller. Traditionally, the MPPT controller is based upon a simple, but slow, search or perturbation algorithm to determine the optimal rotational speed of operation. In this paper, a wind speed estimation-based MPPT algorithm is proposed that employs a heuristic model of both the turbine and the generator to estimate the wind speed. A local search/perturbation of the rotational speed is employed to attain fine tuning of the desired optimal tip-speed ratio tracking. While this algorithm is more complicated than the search based method, it can still be implemented inexpensively. The ease of implementation guarantees fast control updates and ensures maximum power point operation for all wind speeds within the design limitations. The controller has been verified for efficacy on a 1.5 kW laboratory VSG wind generator.