Browsing by Issue Date, starting with "2018-06-12"
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- A New Approach for Dynamic Energy Storage SystemPublication . Barbara, João; Fermeiro, J.B.L.; Pombo, José Álvaro Nunes; Mariano, S.; Calado, M. do RosárioBattery packs with a large number of cells are becoming more and more prominent technology. Monitoring and controlling these packs is now a subject with increased importance. The proposed implemented system consists of only three switches per cell, allowing several types of connection between the cells. The battery management system relies on a distributed hierarchical architecture with n-1 local controllers and a global controller. In the proposed algorithm the cells act as a single swarm functioning autonomously and depending on the parameters (voltage, current and temperature) of each cell of the pack. The hardware for each cell is explained and demonstrated. The results obtained both in simulation and in experimental tests show the excellent performance of the proposed methodology. Also, the charging approach based on the traditional multistage method exhibited an excellent performance on charging supercapacitors, concerning its efficiency, charging time and overvoltage protection.
- Instantaneous Force Control of a Linear Switched Reluctance ActuatorPublication . Pestana, Luís; Calado, M. do Rosário; Mariano, S.This paper is focused on the modeling and analysis of the instantaneous force control of a Linear Switched Reluctance Actuator (LSRA). The conventional control method to reduce thrust ripple uses force distribution functions (FDF) taking into consideration the overall thrust reference and the machine parameters to convey a phase current reference (force is indirectly controlled). In this work two strategies are followed and compared, namely the direct instantaneous thrust control with pulse width duty-ratio adjustment (DITC-PWM) and cosine FDF. The analysis is made in Matlab/ Simulink software package and by using a machine model grounded in lookup tables characteristic data.
- A Modified Multidimension Diode Model for PV Parameters Identification Using Guaranteed Convergence Particle Swarm Optimization AlgorithmPublication . Nunes, H.G.G.; Bento, P.M.R.; Pombo, José Álvaro Nunes; Mariano, S.; Calado, M. do RosárioThis paper proposes a modified multidimension diode model to identify the photovoltaic (PV) parameters using the guaranteed convergence particle swarm optimization algorithm. The main advantage of this model is that it allows adjusting the number of diodes of the PV model by finding the configuration that most accurately characterizes a PV device under a certain operating condition and of different PV technologies. The proposed model was validated from experimental data measured at different irradiance and temperature levels, as well as for six different PV technologies. The results show that the model is able to accurately characterize the behaviour of PV devices.
- Daily Operation Optimization for Grid-Connected Hybrid System Considering Short-Term Electricity Price Forecast SchemePublication . Bento, P.M.R.; Nunes, H.G.G.; Álvaro Nunes Pombo, José; Mariano, S.; Calado, M. do RosárioWith an increasing public and governmental awareness regarding environment protection and sustainable resources, hand-in-hand with an escalating electricity demand, the exponential growth of renewable energy generation capacity has been the “answer”. Mitigating the environmental harms associated with the more conventional energy sources such as: coal, oil, gas and nuclear. Nonetheless, some challenges remain, particularly concerning the integration of these technologies into the conventional generation mix. Hybrid energy systems allow a paradigm shift from a concentrated conventional generation to a more distributed one. This paper discusses the optimized PVwind with hydro and battery storage capabilities for a gridconnected application considering the Short-Term Price Forecast information. The proposed technique has been tested in different scenarios, and results demonstrate the effectiveness of the proposed approach.
- Power Management Strategy for Standalone PV Applications with Hybrid Energy Storage SystemPublication . Faria, João; Pombo, José Álvaro Nunes; Mariano, S.; Calado, M. do RosárioHybrid energy storage systems that combine the high density power of the supercapacitors with the high energy density of the Li-ion batteries have been substantially researched, with great interest. This manuscript proposes a new power management strategy implemented using the Rule based controller which considers the state of charge of the Li-ion batteries (SOC). The Li-ion batteries are used to provide a steady and constant power, function of the state of charge (SOC), enabling a higher efficiency and extending batteries lifespan. A typical standalone PV application is used to demonstrate and validate the performance of the proposed power management strategy.
- Evaluation of the Operational Modal Responses in Linear Switched Reluctance ActuatorsPublication . Salvado, José A.; Calado, M. do Rosário; Espírito Santo, AntónioThe vibrations produced by switched reluctance drives have been studied by numerous authors, mainly for those producing rotational movement. This paper deals with the problem of vibrations produced by linear switched reluctance actuators in operation. We propose a test setup to measure and evaluate the operational responses produced by linear switched reluctance actuators. The phase current and the local accelerations are presented and analyzed, and its frequency components are evaluated and discussed concerning the natural modes obtained from a study supported by finite elements analysis. The information about the operational modal responses is important to establish the control strategies and to avoid switching frequencies close to those of the natural modes.