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- Decision making for sustainable aggregation of clean energy in day-ahead market: uncertainty and riskPublication . Gomes, Isaías; Melicio, Rui; Mendes, Victor; Pousinho, H. M. I.This paper addresses a strategy for decision-making of sustainable aggregation for clean energy participating in a day-ahead electricity market. The clean energy consists of wind turbines, photovoltaic arrays and energy storage, contributing to a better resilience of the system. The power delivered by a wind turbine or by a photovoltaic array is most certainly in deviation from the value associated with the bid accepted at a closing of a day-ahead electricity market. The deviation is due to the unpredicted variable nature of the respective sources of energy, leading to uncertainty and may imply a risk of loss of profit. So, uncertainty must be considered, and the addressed strategy considers uncertainty by scenarios of historical data and risk by the conditional value at risk. The strategy is a unified approach based on a risk-constrained and a two-stage stochastic optimization problem rewritten as a mixed-integer linear programming problem. A case study is presented to illustrate the main result and drive conclusions.
- Wind energy conversion system control using distinct controllers for different operating regionsPublication . Viveiros, C.; Melicio, Rui; Igreja, José; Mendes, VictorThis paper presents a control strategy based on two distinct controllers for different operating regions applied to a wind turbine benchmark. In previous works, we proposed the control of a wind turbine using two distinct controllers for all operating regions. The contribution of this work focus on the use of two distinct controllers for two different operation regions, the fuzzy proportional integral controller in the partial load region, i.e., Region II, and the use of model predictive controller in the full load region, i.e., Region III. The distinct controllers applied on the different operation regions are compared to a standard controller and the simulation results show the efficacy of the proposed control approach.
- Comparison of offshore and onshore wind systems with MPC five-level converter under 3Energy 4.0Publication . Seixas, Mafalda; Melício, R; Mendes, VictorThis paper is about offshore/onshore wind systems under energy 4.0. A consideration is taken to account for the action of the floating motion given by the stiffness torque acting on the drive-train. The drive-train incorporates the dynamics of the floating platform and tower, resulting from the motion of the surface due to the marine wave perturbation. The performance of the multiple point clamped five-level converter is considered mainly from electrical power perspective. The simulation considers a blade pitch control fault causing an instantaneous cutoff on the capture of the wind energy to unveil the impact on the systems performance. Particularly, the fault influence on the behavior of the voltages in the capacitor banks is mitigated by selection of the suitable vectors. The multiple point clamped five-level converter with the conveniently proposed control strategy is able to recover normal operation after fault clearing.
- HVDC power transmission simulation for offshore wind system with three-level converterPublication . Seixas, Mafalda; Melicio, Rui; Mendes, VictorAn integrated mathematical model for the simulation of an offshore wind system performance is presented in this paper. The mathematical model considers an offshore variable-speed turbine in deep water equipped with a permanent magnet synchronous generator using multiple point full-power clamped three-level converter, converting the energy of a variable frequency source in injected energy into the electric network with constant frequency, through a HVDC transmission submarine cable. The mathematical model for the drive train is a concentrate two mass model which incorporates the dynamic for the blades of the wind turbine, tower and generator due to the need to emulate the effects of the wind and the floating motion. Controller strategy considered is a proportional integral one. Also, pulse width modulation using space vector modulation supplemented with sliding mode is used for trigger the transistors of the converter. Finally, a case study is presented to access the system performance.
- Offshore wind energy system with DC transmission discrete mass: modeling and simulationPublication . Seixas, Mafalda; Melicio, Rui; Mendes, VictorThis article presents an integrated model for an offshore wind energy system taking into consideration a contribution for the marine wave and wind speed with perturbations influences on the power quality of current injected into the electric grid. The article deals with the simulation of one floating offshore wind turbine equipped with a permanent magnet synchronous generator and a two-level converter connected to an onshore electric grid. The use of discrete mass modeling is accessed in order to reveal by computing the total harmonic distortion on how the perturbations of the captured energy are attenuated at the electric grid injection point. Two torque actions are considered for the three-mass modeling, the aerodynamic on the flexible part and on the rigid part of the blades. Also, a torque due to the influence of marine waves in deep water is considered. Proportional integral fractional-order control supports the control strategy. A comparison between the drive train models is presented.
- Optimization of wind power producer participation in electricity markets with energy storage in a way of energy 4.0Publication . Gomes, Isaías; Pousinho, Hugo M. I.; Melicio, Rui; Mendes, VictorThis paper proposes a problem formulation to aid as a support information management system of a wind power producer having energy storage devices and participating in electricity markets. Energy storage can play an important role in the reduction of uncertainties faced by a wind power producer. Excess of conversion of wind energy into electric energy can be stored and then released at favorable hours. Energy storage provides capability for arbitrage and increases the revenue of the wind power producers participating in electricity markets. The formulation models the wind power and the market prices as stochastic processes represented by a set of convenient scenarios. The problem is solved by a powerful stochastic mixed integer linear programming problem. A case study using data from the Iberian Electricity Market is presented to show the aid of the formulation.
- Stochastic coordination of joint wind and photovoltaic systems with energy storage in day-ahead marketPublication . Gomes, Isaias L. R.; Pousinho, H. M. I.; Melicio, Rui; Mendes, VictorThis paper presents an optimal bid submission in a day-ahead electricity market for the problem of joint operation of wind with photovoltaic power systems having an energy storage device. Uncertainty not only due to the electricity market price, but also due to wind and photovoltaic powers is one of the main characteristics of this submission. The problem is formulated as a two-stage stochastic programming problem. The optimal bids and the energy flow in the batteries are the first-stage variables and the energy deviation is the second stage variable of the problem. Energy storage is a way to harness renewable energy conversion, allowing the store and discharge of energy at conveniently market prices. A case study with data from the Iberian day-ahead electricity market is presented and a comparison between joint and disjoint operations is discussed.
- Darrieus-type vertical axis rotary-wings with a new design approach grounded in double-multiple streamtube performance prediction modelPublication . Batista, Nelson; Melicio, Rui; Mendes, VictorExploitation of wind energy with vertical axis rotary-wing has advantage over horizontal axis rotary-wing in areas where the wind is turbulent and unstable, i.e., with fast changes either in direction or velocity as normal happens in urban areas. The Darrieus-type vertical axis rotary-wing is experiencing a growth in interest for development and installation due to a growing interest in decentralizing energy conversion. This growth is expected to be in further augment in what concerns the way of the future, i.e., the smart grid environment. A problem linked with this Darrieus-type rotary-wing is the complexity in the performance prediction study, since the blades move around the rotor in 360 degrees. An approach to the double-multiple streamtube performance prediction model for the vertical axis rotary-wing is offered in this paper, offering a flexible adapted tool when the airfoils lift and drag data are not available, or when more complex blade profiles of rotary-wings are in development. A new Darrieus-type vertical axis rotary-wing design is carried out with the approach offered, allowing for a self-start capable blade profile, having an adequate performance at high tip speed ratios. Several field tests are offered providing validation to the self-start, low noise and stable performance of the new rotary-wing design. Also, a modeling, control and simulation of grid integration are presented.
- Comparison between inflexible and flexible charging of electric vehicles—a study from the perspective of an aggregatorPublication . Gomes, Isaías; Melicio, Rui; Mendes, VictorThis paper is about the problem of the management of an aggregator of electric vehicles participating in an electricity market environment. The problem consists in the maximization of the expected profit through a formulation given by a stochastic programming problem to consider the uncertainty faced by the aggregator. This uncertainty is due to the day-ahead market prices and the driving requirements of the owners of the vehicles. Depending on the consent of the owners, inflexible charging to flexible charging is considered. Thus, the aggregator can propose different profiles and charging periods to the owners of electric vehicles. Qualitatively, as expected, the more flexible the vehicle owners, the higher the expected profit. The formulation, however, offers more to the aggregator and provides the ability to quantify the influence of consent of favorable driving requirements in the expected profit, allowing the aggregator to consider rewarding the owners of vehicles with more flexibility. Case studies addressed are for comparison of the influence of owners having inflexibility, partial flexibility, or flexibility in the expected profit of the aggregator.
- Home energy forecast performance tool for smart living services suppliers under an energy 4.0 and CPS frameworkPublication . RODRIGUES, FILIPE; Cardeira, Carlos; Calado, João Manuel Ferreira; Melicio, RuiIndustry 4.0 is a paradigm consisting of cyber-physical systems based on the interconnection between all sorts of machines, sensors, and actuators, generally known as things. The combination of energy technology and information and technology communication (ICT) enables measure ment, control, and automation to be performed across the distributed grid with high time resolution. Through digital revolution in the energy sector, the term Energy 4.0 emerges in the future electric sector. The growth outlook for appliance usage is increasing and the appearance of renewable energy sources on the electric grid requires strategies to control demand and peak loads. Potential feedback for energy performance is the use of smart meters in conjunction with smart energy man agement; well-designed applications will successfully inform, engage, empower, and motivate con sumers. This paper presents several hands-on tools for load forecasting, comparing previous works and verifying which show the best energy forecasting performance in a smart monitoring system. Simulations were performed based on forecasting of the hours ahead of the load for several households. Special attention was given to the accuracy of the forecasting model for weekdays and weekends. The development of the proposed methods, based on artificial neural networks (ANN), pro vides more reliable forecasting for a few hours ahead and peak loads.