A new robust control scheme: Application for MPP tracking of a PMSG-based variable-speed wind turbine

Abstract

This paper proposes a novel Improved Maximum Power Point Tracking (IMPPT) algorithm to extract the maximum available power from a direct-drive Permanent-Magnet Synchronous Generator (PMSG) based standalone Small-scale Variable Speed Wind Turbine (VSWT). The proposed control scheme consists of an IMPPT algorithm to effectively improve the extracted power under various regimes of wind speed. The IMPPT constructs the reference value of the DC voltage for the DC bus. Moreover, a composite low-cost controller (LCC) is also proposed in order to improve the DC voltage tracking based on a new designed nonlinear state observer. The proposed nonlinear robust controller accounts for the overall system dynamics and nonlinear behavior. The objective is to improve the dynamic performance and ensure a good balance of energy conversion efficiency, robustness, cost efficiency, and a simple structure for practical implementation in wind energy conversion systems. Furthermore, the stability of the closed-loop system is analyzed and guaranteed through Lyapunov stability theory. Moreover, two scenarios are used for validation in Matlab/Simulink, including step change and stochastic profiles of wind speed. Simulation results verify the effectiveness and superiority of the IMPPT-LCC approach whereas comparisons with other techniques prove its superiority.