M.R.A. Calado

On the influence of the pole and teeth shapes on the performance of linear switched reluctance actuator

Purpose – The purpose of this paper is the evaluation of the influence of pole and teeth shapes on the behaviour of a linear switched reluctance actuator (LSRA). The study was carried out through the application of a finite element static analysis and the application of a new method for dynamic analysis. Those studies are thereafter evaluated with experimentations.Design/methodology/approach – The paper characterizes the performance of an LSRA for different polar geometries. A finite element tool is used at an early research stage. Results are then used to build a dynamic numerical model. Obtained data allow the construction of a laboratory prototype.Findings – Polar shape has great influence in actuator behaviour. Different geometrical polar configurations are evaluated and their influence is observed. The obtained data allow attraction force minimization with minimal penalty in the thrust force. A numerical dynamic model is used to evaluate actuator movement with different polar shapes, without taking i...

Optimal output control: Load frequency control of a large power system

This paper addresses the stabilization and performance of the load frequency regulator. The problem is solved by using the theory of the optimal control. An algorithm, based on the new technique, proposed by the authors, to overcome the difficulties of specifying the weighting matrices Q and R, is presented. The algorithm here proposed considers the multi-area electric energy system. The paper presents illustrative numerical simulation results for this model. The results indicate that the obtained controller exhibits better performance then those based on classic control.

Design of a new linear generator for wave energy conversion based on analytical and numerical analyses

This paper addresses the problem of the sea wave energy conversion. The power delivery at low speeds is one of the barriers imposed by the irregular movement of sea waves, requiring the use of electric machines that can produce large amounts of force to compensate the low speeds of that motion. The main concern is the proposal of a new linear switched reluctance generator. The proposed generator has high power density, robustness, and easy modeling and construction. Its analytical design and optimization based on finite element method are presented. Results and design challenges are discussed.

Dispatch of Head Dependent Hydro Units: Modeling for optimal generation in electricity market

Deregulation and liberalization of electric power industry, among other things, has created new requirements for the market participants. The power system engineer, operator, and, in general, the market participant is being faced with requirements for which he does not have adequate training and the proper software tools. In this framework, among others, a pure hydro-generation company has to (1) operate its hydro units, throughout the operating day, trying to fulfill the market clearing schedule, and modify the program in the intra-day energy markets if necessary (or more suitable) as real-time operation is getting closer and (2) make the offers for the regulation service market. In this scenario the Dispatch of Head Dependent Hydro Units is a problem that must be solved before dealing with the hourly hydro resource scheduling for energy and reserve optimization.

Power Quality Experimental Analysis on Rural Home Grid-Connected PV Systems

Microgeneration is the small-scale generation of heat or electric power or both, by individuals or buildings to meet their own needs. Recently, microgeneration is being regarded as a means to decentralize the power production of renewable energies, reducing the impacts on the grid caused by unexpected energy demands. Given the increase in microgeneration facilities, determining the quantity of energy produced and the power quality assumes growing importance in low, medium, or high voltage facilities. This paper presents a power quality analysis of two different facilities with photovoltaic generation localized in a rural area of Portugal, describing the voltage and frequency behaviour, the harmonic contents, and the total harmonic distortion. Statistical data are presented regarding the number of voltage events and occurrence of dips and swells in both facilities as a percentage of rated voltage. We conclude that some PV systems can severely affect voltage quality, forcing the grid to work at and even above the maximum voltage standard limit.

Characterization of a new linear switched reluctance actuator

This paper presents the electromagnetic analysis of a new designed and constructed prototype of a single-sided linear switched reluctance actuator. First, a brief consideration on the adopted analytical design methodology, establishing some desired electrical and mechanical parameters, is stated. After, a characterization of the actuator is made, analyzing the distribution of magnetic fields and connected translation forces, through the determination of energy and co-energy variation, performing a numerical analysis based on Finite Element Method. A saturation factor is then introduced, corresponding to the magnetic circuit saturation level, allowing the knowledge of the actuator thrust development performance, as well as the definition of proper relative positions for coils excitation, and respective current intensities, in specific practical motion applications. The influence of saturation factor in the actuator mechanical force development, for different positions and excitations, is established and connected with thermal, electrical and mechanical constraints. The paper is illustrated with experimental tests carried out by the authors.

Particle swarm and Box׳s complex optimization methods to design linear tubular switched reluctance generators for wave energy conversion

Abstract This paper addresses the optimization of the linear switched reluctance generator with tubular topology to be applied in a sea wave energy conversion system. Two new algorithms to optimize the geometry of the generators are proposed. The algorithms are based on both particle swarm and Box´s complex optimization methods. The optimization procedures consist of a multidimensional optimal value search. First the initial variable vectors are specified throughout the feasible search space. Then, an iterative procedure is applied with the goal of finding the variable values that minimize the objective function. The proposed algorithms are suitable for the optimization problem considered since the objective function is highly nonlinear and not analytically defined, as evaluated using a finite element analysis based software, and show very good performance. A factor that characterizes the generation capabilities is also defined and the obtained optimized generators are compared.

An electric vehicle charging station: Monitoring and analysis of power quality

Electric vehicles are a relatively recent technology that is seeking for its place in the market. It has several advantages, such as the reduced greenhouse emissions, fuel savings and its ease of use. The increase of the electric vehicles in the roads raises issues about their impact on the grid, in terms of power quality. This paper presents the main considerations about power balance and the impact of an electric vehicle charge in the voltage, current, and total harmonic distortion. An experimental charging station prototype for Modes 2 and 3 is used to acquire data of voltage, current and active and reactive power for different charging profiles and battery state of charge.

Design of a tubular switched reluctance linear generator for wave energy conversion based on ocean wave parameters

This work presents a procedure for the design and analysis of a linear tubular switched reluctance generator for wave energy conversion. The generator is meant to be applied to a direct drive wave energy converter, namely a point absorber. The device is modeled according to wave climate conditions at Esposende site in the Portuguese coast. The procedure starts with statistical analysis of the local random ocean behavior in order to determine most likely values of occurrence for the wave parameters in question. Based on that, the generator is analytically designed. With the proper dimensions calculated, a numerical simulation is performed and the magnetic flux path and density values are determined.

Linear switched reluctance motor. A new design methodology based on performance evaluation

This paper concerns the design of linear switched reluctance machines (LSRM), by evaluating the traction forces under defined speed operation conditions. A new methodology concerning optimised design of LSRM, for urban systems of electric traction at low and medium speeds, is proposed. This methodology, supposed to be original, is based on the systematic use of a known and fast processing calculation process, in which some changes are made in order to turn it more generic. For each one of the several design machines the respective magnetization curves are calculated, based on the B=f(H) characteristic of the used material, as well as on the calculated machine dimensions. This calculation was made through the linearization of the airgap length mean value between the unaligned and aligned positions. The simulation of different machines permits the selection of proper model for specific requested application. Simultaneously, machine simulation allows to define the best control strategy for continuous operation. The developed software, for machine simulation, still allows to simulate any LSRM with known magnetization curve I=f(/spl psi/,x).