José Manuel Prista do Valle Cardoso Igreja

A simulation study on the abatement of CO2 emissions by de‐absorption with monoethanolamine

Because of the adverse effect of CO2 from fossil fuel combustion on the earth’s ecosystems, the most cost‐effective method for CO2 capture is an important area of research. The predominant process for CO2 capture currently employed by industry is chemical absorption in amine solutions. A dynamic model for the de‐absorption process was developed with monoethanolamine (MEA) solution. Henry’s law was used for modelling the vapour phase equilibrium of the CO2, and fugacity ratios calculated by the Peng–Robinson equation of state (EOS) were used for H2O, MEA, N2 and O2. Chemical reactions between CO2 and MEA were included in the model along with the enhancement factor for chemical absorption. Liquid and vapour energy balances were developed to calculate the liquid and vapour temperature, respectively.

Application of a discrete adaptive LQG and fuzzy control design to a wind turbine benchmark model

This paper deals with a wind turbine control simulation supported by the use of computational tools appropriate to simulate complex systems. High performance and reliability are required for wind turbines to be competitive within the energy market. A key challenge for control systems is the wind power which is an uncontrolled input and also acts as a disturbance. A discrete adaptive LQG (linear quadratic) as well as a fuzzy PI control design of publicly available wind turbine benchmark models are proposed and simulation results by Matlab/Simulink are shown in order to prove the effectiveness of the design.

Fuzzy, integer and fractional-order control: Application on a wind turbine benchmark model

This paper presents a comparison between proportional integral control approaches for variable speed wind turbines. Integer and fractional-order controllers are designed using linearized wind turbine model whilst fuzzy controller also takes into account system nonlinearities. These controllers operate in the full load region and the main objective is to extract maximum power from the wind turbine while ensuring the performance and reliability required to be integrated into an electric grid. The main contribution focuses on the use of fractional-order proportional integral (FOPI) controller which benefits from the introduction of one more tuning parameter, the integral fractional-order, taking advantage over integer order proportional integral (PI) controller. A comparison between proposed control approaches for the variable speed wind turbines is presented using a wind turbine benchmark model in the Matlab/Simulink environment. Results show that FOPI has improved system performance when compared with classical PI and fuzzy PI controller outperforms the integer and fractional-order control due to its capability to deal with system nonlinearities and uncertainties.

Control and Supervision of Wind Energy Conversion Systems

This paper is about a PhD thesis and includes the study and analysis of the performance of an onshore wind energy conversion system. First, mathematical models of a variable speed wind turbine with pitch control are studied, followed by the study of different controller types such as integer-order controllers, fractional-order controllers, fuzzy logic controllers, adaptive controllers and predictive controllers and the study of a supervisor based on finite state machines is also studied. The controllers are included in the lower level of a hierarchical structure composed by two levels whose objective is to control the electric output power around the rated power. The supervisor included at the higher level is based on finite state machines whose objective is to analyze the operational states according to the wind speed. The studied mathematical models are integrated into computer simulations for the wind energy conversion system and the obtained numerical results allow for the performance assessment of the system connected to the electric grid. The wind energy conversion system is composed by a variable speed wind turbine, a mechanical transmission system described by a two mass drive train, a gearbox, a doubly fed induction generator rotor and by a two level converter.

On Wind Turbine Model Predictive Pitch Control: An Event-Based Simulation Approach

This paper is about a hierarchical structure with an event-based supervisor in a higher level and a model predictive control (MPC) in a lower level applied to a wind turbine. The event-based supervisor analyzes the operation conditions to determine the state of the wind turbine. The objectives and constraints of the model predictive controller can also be adjusted by this supervisory controller. This hierarchical structure is able to ensure the performance and reliability required for a wind turbine to be integrated into an electric grid. Comparisons between model predictive pitch control and a default proportional integral pitch controller applied to a wind turbine benchmark are given and simulation results by Matlab/Simulink are shown in order to prove the effectiveness of the proposed approach.

On performance of distributed model predictive control in power system frequency regulation

This paper describes the implementation of a distributed model predictive approach for automatic generation control. Performance results are discussed by comparing classical techniques (based on integral control) with model predictive control solutions (centralized and distributed) for different operational scenarios with two interconnected networks. These scenarios include variable load levels (ranging from a small to a large unbalance generated power to power consumption ratio) and simultaneously variable distance between the interconnected networks systems. For the two networks the paper also examines the impact of load variation in an island context (a network isolated from each other).

Fractional order control on a wind turbine benchmark

This paper is about a hierarchical structure with an event-based supervisor in a higher level and a fractional-order proportional integral (FOPI) in a lower level applied to a wind turbine. The event-based supervisor analyzes the operation conditions to determine the state of the wind turbine. This controller operate in the full load region and the main objective is to capture maximum power generation while ensuring the performance and reliability required for a wind turbine to be integrated into an electric grid. The main contribution focus on the use of fractional-order proportional integral controller which benefits from the introduction of one more tuning parameter, the integral fractional-order, taking advantage over integer order proportional integral (PI) controller. Comparisons between fractional-order pitch control and a default proportional integral pitch controller applied to a wind turbine benchmark are given and simulation results by Matlab/Simulink are shown in order to prove the effectiveness of the proposed approach.

Fault Tolerant Control Based on Adaptive LQG and Fuzzy Controllers

This paper describes a fault tolerant switching loop control study case for a three water tank laboratory setup with sensors and actuators redundancies. Fault diagnosis and tolerance are two main characteristics of intelligent setups when closed-loop control is used for large complex systems. Discrete adaptive LQG (linear quadratic) and Fuzzy fault tolerant controllers, for nominal situation, are presented and tested in the laboratory setup. For abrupt fault situation (structural fault), switching from one controller to another based on controller performance evaluation using PCA (principal component analysis) technique is implemented. The main contributions are: (a) proposed approach based on PCA to detect structural faults; (b) performance assessment based on performance index through Mahalanobis distance using T 2 statistics and (c) control switching between LQG and Fuzzy controllers based on the performance index. Experimental results applied to a three-tank laboratory setup in the presence of a structural fault are shown to evaluate the performance of the proposed approach.

Mechanical Multi-agent Maneuvering Using Noncooperative DMPC

Distributed Model Predictive Control is used to coordinate agents in multi-agent systems by managing set-points and coupling constraints. The coordination of multi-agent systems concept regards all type of control algorithms dependent on information interchange between subsystems. The control algorithms are developed to solve a series of static optimization problems with nonlinear coupling constraints by means of a typical receding horizon policy applied in predictive control design. For distributed scenarios, the motion of each agent is determined by the distributed algorithm as function of the information shared with the other agents making the individual behavior implicitly dependent on a global outcome or cost. The control algorithm is used to maneuver dynamically decoupled mechanical agents in a two dimensional scenario with obstacles avoidance. The found solution is meaningful to realize how Predictive Control can be an alternative to other solutions obtained through Dynamic Games, where the agents play an important role, in a strategic space, as game players or Computational Intelligence technique, where the agents present a self-organized behavior. Hence, the developed algorithm is useful to maneuver unmanned vehicles in mazes, formations and also for collision avoidance.

Wind energy conversion system under a supervisor deterministic finite state machine

This paper presents a simulation of an onshore energy conversion system connected to the electric grid and under a strategy of a supervisor control based on deterministic version of a finite state machine. The simulation is planned to address an analysis on performance due to the action of the supervisor. The supervisor is included at the higher level, having the objective of analyzing the operational states according to the wind speed. The energy conversion system is equipped with a doubly-fed induction generator and a variable speed variable pitch wind turbine. The analysis is carried by computer simulations and the obtained results allow assessment to the performance of the system. A comparison of the wind energy conversion system performance with or without the supervisor is carried out in order to access the influence of the strategy on the performance.