Fernando Valenciaga

Supervisor control for a stand-alone hybrid generation system using wind and photovoltaic energy

A comprehensive supervisor control for a hybrid system that comprises wind and photovoltaic generation subsystems, a battery bank, and an ac load is developed in this paper. The objectives of the supervisor control are, primarily, to satisfy the load power demand and, second, to maintain the state of charge of the battery bank to prevent blackout and to extend the life of the batteries. For these purposes, the supervisor controller determines online the operation mode of both generation subsystems, switching from power regulation to maximum power conversion. Decision criteria for the supervisor based on measurable system variables are presented. Finally, the performance of the supervisor controller is extensively assessed through computer simulation using a comprehensive nonlinear model of the plant.

Lyapunov-Designed Super-Twisting Sliding Mode Control for Wind Energy Conversion Optimization

This work explores an adaptive second-order sliding mode control strategy to maximize the energy production of a wind energy conversion system (WECS) simultaneously reducing the mechanical stress on the shaft. Such strategy successfully deals with the random nature of wind speed, the intrinsic nonlinear behavior of the WECS, and the presence of model uncertainties and external perturbations acting on the system. The synthesized adaptive controller is designed from a modified version of the super-twisting (ST) algorithm with variable gains. The suitability of the proposed strategy is proved by extensive computer-aided simulations employing a comprehensive model of the system emulating realistic conditions of operation, i.e., considering variations in the parameters and including external disturbances. Additionally, a second controller based on the traditional ST algorithm is also designed and simulated. Results are presented and discussed in order to establish a comparison framework.

Variable Structure Control of a Wind Energy Conversion System Based on a Brushless Doubly Fed Reluctance Generator

This paper introduces a variable structure robust controller for wind energy conversion systems based on brushless doubly fed reluctance machine. Two simultaneous control goals are tackled: maximization of the wind energy conversion efficiency and minimization of the machine copper losses. The proposed multiple-input multiple-output (MIMO) robust controller is systematically synthesized following a general design method for MIMO nonlinear affine systems. The design is approached through a theoretical framework based on the combination of variable structure techniques and the Lyapunovs theory. Robustness to bounded disturbances and chattering minimization is attained.

Power control of a solar/wind generation system without wind measurement: a passivity/sliding mode approach

This paper deals with the control of the output power of a solar/wind stand-alone system. The control system regulates the generation of the wind subsystem in order to satisfy, jointly with the photovoltaic generation subsystem, the load and battery charge power demand. The controller is designed using a theoretical framework that unifies passivity and sliding mode techniques. The resultant control law does not need wind measurement and only relies on rotational speed and current measurements. An analysis of the acceleration estimate error is carried out and a countermeasure to compensate its effects is proposed. Finally, the performance of the controller is assessed through computer simulation, using a comprehensive nonlinear model of the plant.

Active and Reactive Power Control for Wind Turbine Based on a MIMO 2-Sliding Mode Algorithm With Variable Gains

This study proposes a power control strategy for a grid-connected variable-speed wind turbine, based on a doubly-fed induction generator (DFIG) with slip power recovery. The control objectives vary with the zones of operation (dependant on the wind speed), aiming to maximize the active power in the partial load zone and to limit it when operating within the full load zone, while regulating the stator reactive power following grid requirements. The control design, based on the second-order sliding modes (SOSM) and Lyapunov, uses a modified version of the super-twisting algorithm with variable gains which can be applied to nonlinear multiple inputs-multiple outputs (MIMO) systems. The well-known robustness of the sliding techniques, the simplicity of the algorithm, and the adaptive characteristic of its gains are used together in this study to obtain a controller able to deal robustly with the exacting challenges presented by these systems. An additional benefit of the proposal lies in the smoothness of the control action, an important issue regarding applied mechanical efforts. Representative results obtained by simulation of the controlled system are shown and discussed.

An adaptive feedback linearization strategy for variable speed wind energy conversion systems

This paper presents a control strategy based on adaptive feedback linearization intended for variable speed grid-connected wind energy conversion systems (WECS). The proposed adaptive control law accomplishes energy capture maximization by tracking the wind speed fluctuations. In addition, it linearizes the system even in the presence of turbine model uncertainties, allowing the closed-loop dynamic behaviour to be determined by a simple tuning of the controller parameters. Particularly, the attention is focused on WECS with slip power recovery, which use a power conversion stage as a rotor-controlled double-output induction generator. However, the concepts behind the proposed control strategy are general and can be easily extended to other WECS configurations. Copyright

Sliding mode control for efficiency optimization of wind energy systems with double output induction generator

This paper deals with generation efficiency maximization of wind energy conversion systems (WECS) with double output induction generator (DOIG). In the first place, to design a sliding mode controller, an apropos model of the DOIG with electronic drive in the rotor is developed. Then, conditions of maximum power generation are obtained. Finally, a sliding mode control strategy for this type of WECS is presented. The proposed strategy varies the firing angle of the electronic drive in order to set the extreme control values equal to the maximum and minimum available control action of the system. Consequently, robustness to parametric uncertainties and external disturbances is maximised.

Experimental results on smooth path tracking with application to pipe surveying on inexpensive AUV

This paper details the development aspects of a low cost AUV autonomous, designed for autonomous pipline inspections, describing: hardware, software and control aspects. The article details three of the mains stages of the project, that have been already achieved: (a) the simulation results of Lyapunov based path planning of torpedo shaped AUV on pipe searching; (b) the construction details of dual torpedo AUV for pipeline inspection and (c) the experimental results when using the prototype in path following using the line of sight (LOS) algorithm.

Variable gains super-twisting control for wind energy conversion optimization

An adaptive second order sliding mode control strategy is explored in this work, to maximize the energy extracted from the wind in a wind energy conversion system (WECS). It is required to such strategy to deal with the nonlinear nature of the WECS, the randomness of the wind speed, model uncertainties and external disturbances, and also with the need to reduce mechanical loads. The special features of this adaptive technique together with the robustness, relative simplicity and other desirable inherent characteristics of the super-twisting algorithm make the proposed controller an attractive solution. The suitability of the proposed strategy is proved by extensive computer aided simulations employing a comprehensive model of the system.

Active and reactive power control of a brushless doubly fed reluctance machine using high order sliding modes

This article develops a decoupled active and reactive power control for a variable-speed constant-frequency (VSCF) power generation system based on a brushless doubly fed reluctance machine. This machine is a forthcoming low cost candidate for applications with limited variable speed requirements such as pumping and wind generation. Basically, it allows the use of a partially rated power electronic converter and, at the same time, offers a reliable and maintenance-free operation because of its brushless feature. The control design is approached through second order sliding mode techniques. This theoretical framework permits to deal with systems described by perturbed nonlinear dynamic models, obtaining simple controllers with a finite time reaching phase and a chattering free behavior. The controller performance is assessed through exhaustive simulations.