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Adolfo J. Sánchez
Departamento de Ingeniería de Sistemas y Automática, Universidad de Sevilla, Camino de los Descubrimientos S/N, 41092 Sevilla, Spain

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Journal article
Published: 02 April 2021 in Solar Energy
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One of the main control objectives in parabolic trough solar thermal plants is to maintain the outlet temperature around an operating point. For this, a synthetic oil flow is used as the main control variable. However, another crucial system of the plant is the defocusing safety system of the collectors to prevent the oil temperature from exceeding an upper limit to prevent its degradation. This will occur, in general, when the oil flow reaches the maximum possible and is not able to regulate anymore the temperature. This mechanism is generally applied based on heuristic rules and partial or total defocus, which leads to a large number of actuator actions and temperature oscillations. In commercial plants, this defocus mechanism is applied firstly to the last collector, and as necessary, other collectors are defocused. In addition, it must be taken into account that loops’ parameters will be, in general, different. In this work, a FeedForward-based strategy is proposed to control the outlet temperature of collectors 1, 2 and 3 of a solar plant using the defocus angle as the manipulated variable. It is also proposed to dynamically obtain the set-point temperatures for the first 3 collectors through an optimization based on the concentrated parameter model. The results of the simulations are presented in different situations where the good performance of the strategy is observed. It is shown how the dynamic modification of the set-points can avoid possible energy losses on occasions where a fixed set-point of temperature is not the optimal option.

ACS Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. Hierarchical set-point optimization and feedforward strategy for collector defocusing of a solar plant. Solar Energy 2021, 220, 282 -294.

AMA Style

A.J. Sánchez, A.J. Gallego, J.M. Escaño, E.F. Camacho. Hierarchical set-point optimization and feedforward strategy for collector defocusing of a solar plant. Solar Energy. 2021; 220 ():282-294.

Chicago/Turabian Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. 2021. "Hierarchical set-point optimization and feedforward strategy for collector defocusing of a solar plant." Solar Energy 220, no. : 282-294.

Journal article
Published: 09 September 2020 in Solar Energy
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In solar thermal plants, as in any industrial process, it is important to maintain good control of the system and, more importantly, to have a good security system to avoid exceeding the safety limits of the components and avoid their degradation. In the case of solar thermal plants, one of the main components is the Heat Transfer Fluid (HTF), which must be kept below a maximum temperature. Although the temperature of the fluid, in general, will be controlled by modifying the flow-rate, when the plant is saturated HTF temperature is kept under limits by defocusing of the collectors. In this paper, an analysis of the control of the defocus control applied to the different collectors is presented. A Model Predictive Control technique will be applied to control the temperature by defocusing two and four collectors in different situations. It is shown how controlling the temperature by defocusing only two collectors is not sufficient in all situations and that controlling by defocusing the four collectors solves this problem in addition to maintaining the defocus actions in areas with high control authority.

ACS Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. Parabolic Trough Collector Defocusing Analysis: Two control stages vs four control stages. Solar Energy 2020, 209, 30 -41.

AMA Style

A.J. Sánchez, A.J. Gallego, J.M. Escaño, E.F. Camacho. Parabolic Trough Collector Defocusing Analysis: Two control stages vs four control stages. Solar Energy. 2020; 209 ():30-41.

Chicago/Turabian Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. 2020. "Parabolic Trough Collector Defocusing Analysis: Two control stages vs four control stages." Solar Energy 209, no. : 30-41.

Conference paper
Published: 06 March 2020 in Actas de las XXXIX Jornadas de Automática, Badajoz, 5-7 de septiembre de 2018
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ACS Style

Adolfo J. Sánchez; Juan Manuel Escaño; Carlos Bordons; Eduardo F. Camacho. Estimador borroso de una planta solar cilindro-parabólica. Actas de las XXXIX Jornadas de Automática, Badajoz, 5-7 de septiembre de 2018 2020, 1 .

AMA Style

Adolfo J. Sánchez, Juan Manuel Escaño, Carlos Bordons, Eduardo F. Camacho. Estimador borroso de una planta solar cilindro-parabólica. Actas de las XXXIX Jornadas de Automática, Badajoz, 5-7 de septiembre de 2018. 2020; ():1.

Chicago/Turabian Style

Adolfo J. Sánchez; Juan Manuel Escaño; Carlos Bordons; Eduardo F. Camacho. 2020. "Estimador borroso de una planta solar cilindro-parabólica." Actas de las XXXIX Jornadas de Automática, Badajoz, 5-7 de septiembre de 2018 , no. : 1.

Journal article
Published: 18 November 2019 in Journal of Process Control
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One of the ways to improve the efficiency of solar energy plants is by using advanced control and optimization algorithms. In particular, model predictive control strategies have been applied successfully in their control. The control objective of this kind of plant is to regulate the solar field outlet temperature around a desired set-point. Due to the highly nonlinear dynamics of these plants, a simple linear controller with fixed parameters is not able to cope with the changing dynamics and the multiple disturbance sources affecting the field. In this paper, an adaptative model predictive control strategy is designed for a Fresnel collector field belonging to the solar cooling plant installed at the Escuela Superior de Ingenieros in Sevilla. The controller changes the linear model used to predict the future evolution of the system with respect to the operating point. Since only the inlet and outlet temperatures of the heat transfer fluid are measurable, the intermediate temperatures have to be estimated. An unscented Kalman filter is used as a state estimator. It estimates metal-fluid temperature profiles and effective solar radiation. Simulation results are provided comparing the proposed strategy with a PID + feedforward series controller showing better performance. The controller is also compared to a gain scheduling generalized predictive controller (GS-GPC) which has previously been tested at the actual plant with a very good performance. The proposed strategy outperforms these two strategies. Furthermore, two real tests are presented. These tests show that the proposed controller achieves adequate set-point tracking in spite of strong disturbances.

ACS Style

Antonio J. Gallego; Adolfo J. Sánchez; M. Berenguel; Eduardo F. Camacho. Adaptive UKF-based model predictive control of a Fresnel collector field. Journal of Process Control 2019, 85, 76 -90.

AMA Style

Antonio J. Gallego, Adolfo J. Sánchez, M. Berenguel, Eduardo F. Camacho. Adaptive UKF-based model predictive control of a Fresnel collector field. Journal of Process Control. 2019; 85 ():76-90.

Chicago/Turabian Style

Antonio J. Gallego; Adolfo J. Sánchez; M. Berenguel; Eduardo F. Camacho. 2019. "Adaptive UKF-based model predictive control of a Fresnel collector field." Journal of Process Control 85, no. : 76-90.

Journal article
Published: 16 July 2019 in Energies
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Solar energy for cooling systems has been widely used to fulfill the growing air conditioning demand. The advantage of this approach is based on the fact that the need of air conditioning is usually well correlated to solar radiation. These kinds of plants can work in different operation modes resulting on a hybrid system. The control approaches designed for this kind of plant have usually a twofold goal: (a) regulating the outlet temperature of the solar collector field and (b) choosing the operation mode. Since the operation mode is defined by a set of valve positions (discrete variables), the overall control problem is a nonlinear optimization problem which involves discrete and continuous variables. This problems are difficult to solve within the normal sampling times for control purposes (around 20–30 s). In this paper, a two layer control strategy is proposed. The first layer is a nonlinear model predictive controller for regulating the outlet temperature of the solar field. The second layer is a fuzzy algorithm which selects the adequate operation mode for the plant taken into account the operation conditions. The control strategy is tested on a model of the plant showing a proper performance.

ACS Style

Eduardo F. Camacho; Antonio J. Gallego; Juan M. Escaño; Adolfo J. Sánchez. Hybrid Nonlinear MPC of a Solar Cooling Plant. Energies 2019, 12, 2723 .

AMA Style

Eduardo F. Camacho, Antonio J. Gallego, Juan M. Escaño, Adolfo J. Sánchez. Hybrid Nonlinear MPC of a Solar Cooling Plant. Energies. 2019; 12 (14):2723.

Chicago/Turabian Style

Eduardo F. Camacho; Antonio J. Gallego; Juan M. Escaño; Adolfo J. Sánchez. 2019. "Hybrid Nonlinear MPC of a Solar Cooling Plant." Energies 12, no. 14: 2723.

Review
Published: 13 April 2019 in Energies
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This paper reports a general overview of current research on analysis and control of the power grid with grid scale PV-based power generations as well as of various consequences of grid scale integration of PV generation units into the power systems. Moreover, the history of PV renewable growth, deregulation of power system and issues related to grid-connected PV systems considering its contribution to various responsibilities like frequency control, virtual inertia capabilities and voltage regulation are discussed. Moreover, various outcomes of the high-penetrated grid with PV power plants such as power quality, active and reactive power control, protection, balancing and reliability under various loading conditions are reviewed and discussed.

ACS Style

Elyas Rakhshani; Kumars Rouzbehi; Adolfo J. Sánchez; Ana Cabrera Tobar; Edris Pouresmaeil. Integration of Large Scale PV-Based Generation into Power Systems: A Survey. Energies 2019, 12, 1425 .

AMA Style

Elyas Rakhshani, Kumars Rouzbehi, Adolfo J. Sánchez, Ana Cabrera Tobar, Edris Pouresmaeil. Integration of Large Scale PV-Based Generation into Power Systems: A Survey. Energies. 2019; 12 (8):1425.

Chicago/Turabian Style

Elyas Rakhshani; Kumars Rouzbehi; Adolfo J. Sánchez; Ana Cabrera Tobar; Edris Pouresmaeil. 2019. "Integration of Large Scale PV-Based Generation into Power Systems: A Survey." Energies 12, no. 8: 1425.

Journal article
Published: 01 April 2019 in Solar Energy
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Commercial solar plants produce energy around a nominal operating point in which the solar field outlet temperature is high and close to the thermal limit of the heat transfer fluid. The main control of the temperature is carried out by means of the fluid flow-rate that circulates through the solar field. Defocusing the collectors is normally used as a safety mechanism to avoid exceeding the thermal limit. However, in situations in which the flow is saturated, the control of defocusing the collectors becomes of vital importance and is the system in charge of controlling the solar field outlet temperature. The paper presents an Adaptive State Space Model Predictive Control strategy with an incremental formulation to control the fourth and third collector defocus angles for field outlet temperature set-point tracking at the nominal operation point, avoiding the Heat Transfer Fluid temperature from exceeding the manufacturer thermal limit (oil degradation). The state space description uses an Unscented Kalman Filter for estimating the non-measurable states. A 50 MW parabolic solar trough plant nonlinear model has been used to design and validate the strategy. Simulation results are presented showing the advantages of using the proposed strategy.

ACS Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. Adaptive incremental state space MPC for collector defocusing of a parabolic trough plant. Solar Energy 2019, 184, 105 -114.

AMA Style

A.J. Sánchez, A.J. Gallego, J.M. Escaño, E.F. Camacho. Adaptive incremental state space MPC for collector defocusing of a parabolic trough plant. Solar Energy. 2019; 184 ():105-114.

Chicago/Turabian Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. 2019. "Adaptive incremental state space MPC for collector defocusing of a parabolic trough plant." Solar Energy 184, no. : 105-114.

Journal article
Published: 20 December 2018 in Energies
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Model predictive control has been demonstrated to be one of the most efficient control techniques for solar power systems. An incremental offset-free state-space Model Predictive Controller (MPC) is developed for the Fresnel collector field located at the solar cooling plant installed on the roof of the Engineering School of Sevilla. A robust Luenberger observer is used for estimating the states of the plant which cannot be measured. The proposed strategy is tested on a nonlinear distributed parameter model of the Fresnel collector field. Its performance is compared to that obtained with a gain-scheduling generalized predictive controller. A real test carried out at the real plant is presented, showing that the proposed strategy achieves a very good performance.

ACS Style

Eduardo F. Camacho; Antonio J. Gallego; Adolfo J. Sanchez; Manuel Berenguel. Incremental State-Space Model Predictive Control of a Fresnel Solar Collector Field. Energies 2018, 12, 3 .

AMA Style

Eduardo F. Camacho, Antonio J. Gallego, Adolfo J. Sanchez, Manuel Berenguel. Incremental State-Space Model Predictive Control of a Fresnel Solar Collector Field. Energies. 2018; 12 (1):3.

Chicago/Turabian Style

Eduardo F. Camacho; Antonio J. Gallego; Adolfo J. Sanchez; Manuel Berenguel. 2018. "Incremental State-Space Model Predictive Control of a Fresnel Solar Collector Field." Energies 12, no. 1: 3.

Conference paper
Published: 19 December 2018 in Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016
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ACS Style

Antonio J. Gallego; Luis J. Yebra; Eduardo F. Camacho; Adolfo J. Sánchez. Mathematical Modeling of the Parabolic Trough Collector Field of the TCP-100 Research Plant. Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016 2018, 912 -918.

AMA Style

Antonio J. Gallego, Luis J. Yebra, Eduardo F. Camacho, Adolfo J. Sánchez. Mathematical Modeling of the Parabolic Trough Collector Field of the TCP-100 Research Plant. Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016. 2018; (142):912-918.

Chicago/Turabian Style

Antonio J. Gallego; Luis J. Yebra; Eduardo F. Camacho; Adolfo J. Sánchez. 2018. "Mathematical Modeling of the Parabolic Trough Collector Field of the TCP-100 Research Plant." Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016 , no. 142: 912-918.

Journal article
Published: 22 September 2018 in Solar Energy
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Optimal operation of a solar plant is generally understood as a tracking of the optimal working temperatures which maximize the net electric power. However, a commercial solar plant may receive a limitation from the Transmission System Operator due to saturation of the electrical grid. In these situations the plant moves to an operation mode in which the objective is not maximum production but compliance with the orders of the Transmission System Operator. The paper proposes an Event-Based Gain Scheduling Generalized Predictive Control strategy for electric power production reference tracking when power limitations are imposed by the Transmission System Operator. Gain Scheduling Generalized Predictive Controllers are proposed to control fourth and third collector defocus in order to prevent heating fluid temperature from exceeding the limits of the manufacturer and therefore, avoid oil degradation. A 50 MW parabolic solar trough plant model has been used to design and validate the strategy. Simulation results are presented showing the advantages of using the proposed strategy.

ACS Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. Event-based MPC for defocusing and power production of a parabolic trough plant under power limitation. Solar Energy 2018, 174, 570 -581.

AMA Style

A.J. Sánchez, A.J. Gallego, J.M. Escaño, E.F. Camacho. Event-based MPC for defocusing and power production of a parabolic trough plant under power limitation. Solar Energy. 2018; 174 ():570-581.

Chicago/Turabian Style

A.J. Sánchez; A.J. Gallego; J.M. Escaño; E.F. Camacho. 2018. "Event-based MPC for defocusing and power production of a parabolic trough plant under power limitation." Solar Energy 174, no. : 570-581.

Journal article
Published: 01 May 2018 in Solar Energy
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ACS Style

Adolfo J. Sánchez; Antonio Javier Gallego; Juan Manuel Escaño; E.F. Camacho. Temperature homogenization of a solar trough field for performance improvement. Solar Energy 2018, 165, 1 -9.

AMA Style

Adolfo J. Sánchez, Antonio Javier Gallego, Juan Manuel Escaño, E.F. Camacho. Temperature homogenization of a solar trough field for performance improvement. Solar Energy. 2018; 165 ():1-9.

Chicago/Turabian Style

Adolfo J. Sánchez; Antonio Javier Gallego; Juan Manuel Escaño; E.F. Camacho. 2018. "Temperature homogenization of a solar trough field for performance improvement." Solar Energy 165, no. : 1-9.

Conference paper
Published: 10 November 2016 in 2016 3rd Conference on Control and Fault-Tolerant Systems (SysTol)
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Direct solar radiation is important in a solar trough plant because it is the perturbation that affects most the operation. Generally, it is measured locally. Production losses or dangerous situations may occur when controlling a plant with wrong measurements. A possible solution is to have several pyrheliometers though two problems arise: cost and sensor fusion (complexity). The aim of this paper is to prove that a solar estimation based on Classification and Regression Trees can be used to design a Fault Tolerant Model Predictive Control strategy capable to work with erroneous values of radiation or even none, avoiding dangerous situations or production losses.

ACS Style

Adolfo J. Sanchez; Juan Manuel Escaño; Antonio J. Gallego; Eduardo F. Camacho. Fault tolerant MPC of a solar trough field based on classification and regression trees. 2016 3rd Conference on Control and Fault-Tolerant Systems (SysTol) 2016, 152 -157.

AMA Style

Adolfo J. Sanchez, Juan Manuel Escaño, Antonio J. Gallego, Eduardo F. Camacho. Fault tolerant MPC of a solar trough field based on classification and regression trees. 2016 3rd Conference on Control and Fault-Tolerant Systems (SysTol). 2016; ():152-157.

Chicago/Turabian Style

Adolfo J. Sanchez; Juan Manuel Escaño; Antonio J. Gallego; Eduardo F. Camacho. 2016. "Fault tolerant MPC of a solar trough field based on classification and regression trees." 2016 3rd Conference on Control and Fault-Tolerant Systems (SysTol) , no. : 152-157.

Conference paper
Published: 01 June 2016 in 2016 27th Irish Signals and Systems Conference (ISSC)
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In this paper, an input selection technique for fuzzy-based dynamic modelling is presented. When a system is composed of a large number of input-output variables with strong coupled dynamics, a systematic method is required in order to minimise the modelling error through the selection of proper variables. The selection approach is based on a Genetic algorithm optimisation to obtain solutions as binary strings that effectively determine a proper input field structure.

ACS Style

Juan Manuel Escaño; Adolfo J. Sánchez; Kritchai Witheephanich; Samira Roshany-Yamchi. Input variables selection of fuzzy dynamic models by using genetic algorithm. 2016 27th Irish Signals and Systems Conference (ISSC) 2016, 1 -6.

AMA Style

Juan Manuel Escaño, Adolfo J. Sánchez, Kritchai Witheephanich, Samira Roshany-Yamchi. Input variables selection of fuzzy dynamic models by using genetic algorithm. 2016 27th Irish Signals and Systems Conference (ISSC). 2016; ():1-6.

Chicago/Turabian Style

Juan Manuel Escaño; Adolfo J. Sánchez; Kritchai Witheephanich; Samira Roshany-Yamchi. 2016. "Input variables selection of fuzzy dynamic models by using genetic algorithm." 2016 27th Irish Signals and Systems Conference (ISSC) , no. : 1-6.

Conference paper
Published: 01 June 2015 in 2015 26th Irish Signals and Systems Conference (ISSC)
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In this paper we propose an estimator of solar radiation and a heuristic radiation selector to design a solar radiation Fault Tolerant Model Predictive Control strategy for solar trough plants. The complete design of the control system proposed has been simulated using the model of ACUREX solar trough plant at the Plataforma Solar de Almería (PSA) using a Gain Scheduling Generalized Predictive Control(GS-GPC) control strategy. Simulation results (estimation/heuristic selector/GS-GPC) of the proposed scheme are compared with simulations of the same GS-GPC controller strategy when using only a pyrheliometer radiation measurement.

ACS Style

Adolfo J. Sanchez; Juan Manuel Escaño; Niel Canty; Antonio J. Gallego; Eduardo F. Camacho; Sanchez A.J.; Escano J.M.; Canty N.; Camacho E.F.. Solar radiation estimator and fault tolerant model predictive control of a parabolic-trough field. 2015 26th Irish Signals and Systems Conference (ISSC) 2015, 1 -7.

AMA Style

Adolfo J. Sanchez, Juan Manuel Escaño, Niel Canty, Antonio J. Gallego, Eduardo F. Camacho, Sanchez A.J., Escano J.M., Canty N., Camacho E.F.. Solar radiation estimator and fault tolerant model predictive control of a parabolic-trough field. 2015 26th Irish Signals and Systems Conference (ISSC). 2015; ():1-7.

Chicago/Turabian Style

Adolfo J. Sanchez; Juan Manuel Escaño; Niel Canty; Antonio J. Gallego; Eduardo F. Camacho; Sanchez A.J.; Escano J.M.; Canty N.; Camacho E.F.. 2015. "Solar radiation estimator and fault tolerant model predictive control of a parabolic-trough field." 2015 26th Irish Signals and Systems Conference (ISSC) , no. : 1-7.