A Proportional Plus a Hysteretic Term Control Design: A Throttle Experimental Emulation to Wind Turbines Pitch Control

Leonardo Acho

doi:10.3390/en12101961

Abstract

Pitch control is a relevant issue in wind turbines to properly operate the angle of the blades. Therefore, this control system pitches the blades usually a few degrees every time the wind changes in order to keep the rotor blades at the required angle thus controlling the rotational speed of the turbine. All the same time, the control of the pitch angle is not easy due to the system behavior being highly nonlinear. Consequently, the main objective of this paper is to depict an easy to implement control design based on a proportional controller and a hysteretic term to an emulator pitch control system in wind turbines. This emulator is just an automotive throttle device. This mechanical body dynamically captures some hard non-linearities presented in pitch wind turbine mechanisms, such as backlash, asymmetrical non-lineal effects, friction, and load variations. Even under strong non-linear effects that are difficult to model, a proportional controller and a hysteretic term may satisfy the main control design objective. Hence, a recent control design is developed and applied to a throttle system. We invoke the Lyapunov theory to confirm stability of the resultant closed-loop system. In addition, the proposed control approach is completely implemented by using operational amplifiers. Hence, no digital units are required at all. Moreover, the cost of the developed experimental platform and its outcomes are inexpensive. According to the experimental results, the controller performance seems acceptable, and validating of the control contribution too. For instance, a settling-time of about 0.03 s to a unit step-response is obtained.

Highlights

Pitch control is important in wind turbines to help drive the angle of the blades
The throttle device has been extensively analyzed in the automotive combustion control area [1,4,5,6,7]
Some use control design by compensating the undesired effects introduced by the friction and limp-home non-linearities, while others are based on control adaptive theory by requiring complex plant modelling

Summary

Introduction

Pitch control is important in wind turbines to help drive the angle of the blades. This control system pitches the blades a few degrees every time the wind changes to keep the rotor blades at the required angle, controlling the rotational speed of the wind turbine. Some use control design by compensating the undesired effects introduced by the friction and limp-home non-linearities, while others are based on control adaptive theory by requiring complex plant modelling. Regarding the last two pints, and in order to conceive an inexpensive experimental platform, it was essential to coin a simple and robust controller able to be applied in an elementary analog electronic circuit. To the best of the author’s knowledge, the number of contributions on wind turbine pitch (or equivalent throttle device) control realization through using an electronic circuit design is not large. A re-configurable fractional-order PIλ circuit controller applied to a throttle mechanism is presented in [22] This design employs operational transconductance amplifiers where integration functions is performed by reconfigurating the integer-order topology. The list of symbols related to the main involved electronic parts is utilized: R: Resistance

Control Design

Conclusions