Improvement of Small Wind Turbine Control in the Transition Region

Mario L Ruz,Juan Garrido,Sergio Fragoso,Francisco Vazquez

doi:10.3390/pr8020244

Abstract

Wind energy conversion systems are very challenging from the control system viewpoint. The control difficulties are even more challenging when wind turbines are able to operate at variable speed and variable pitch. The contribution of this work is focused on designing a combined controller that significantly alleviates the wind transient loads in the power tracking and power regulation modes as well as in the transition zone. In a previous work, the authors studied the applicability of different multivariable decoupling methodologies. The methodologies were tested in simulation and verified experimentally in a lab-scale wind turbine. It was demonstrated that multivariable control strategies achieve a good closed-loop response within the transition region, where the interaction level is greater. Nevertheless, although such controllers showed an acceptable performance in the power tracking (region II) and power regulation (region IV) zones, appreciable improvement was possible. To this end, the new proposed methodology employs a multivariable gain-scheduling controller with a static decoupling network for the transition region and monovariable controllers for the power tracking and power regulation regions. To make the transition between regions smoother, a gain scheduling block is incorporated into the multivariable controller. The proposed controller is experimentally compared with a standard switched controller in the lab-scale wind turbine. The experiments carried out suggest that the combination of the proposed multivariable strategy for the transition region to mitigate wind transient loads combined with two monovariable controllers, one dedicated to region II and other to region IV, provide better results than traditional switched control strategies.

Highlights

During the last decades, the increasing concern about the environment and global warming have reinforced the interest in wind energy exploitation [1]
In a previous work [5], the authors compared different multivariable control methodologies methodologies to improve the energy capture, power quality, and wind transient alleviation for variable-speed variable-pitch (VS-VP) wind turbines. These techniques showed a proper closed-loop response, at the transition region, which presents more interaction. Such controllers showed an acceptable performance in the power tracking and power regulation zones, wind disturbance rejection presented appreciable improvement
The authors simulated and experimentally verified that multivariable control strategies achieve a good closed-loop response within the transition region. Such controllers showed an acceptable performance in the power tracking and power regulation regions, disturbance rejection can appreciably be improved

Summary

Introduction

The increasing concern about the environment and global warming have reinforced the interest in wind energy exploitation [1]. System control and optimization play a very important role in wind energy conversion systems. Control of the power quality and integration into the network, alleviation of mechanical loads, and maximization of energy capture are essential factors that have a direct impact on the cost and competitiveness of wind technology [3]. The ideal power curve of a wind turbine exhibits mainly three operational modes or regions depending on the wind speed: at low wind speeds (power tracking mode or region II), where the available power is below the nominal power, the main control objective is to maximize the power conversion efficiency. There is the high speed region or full load

Objectives

Results

Conclusion