This paper deals with the concept of the stochastic optimization methodology for power line designing, which allows optimizing transmission network planning. The paper presents a comparison of both methods applied for selecting the best line design alternative - the deterministic economic intervals method and the stochastic approach based method, taking into account market conditions. Both methods are utilized for designing overhead power lines, including the choice of main line parameters such as tower height, type and coordinates, conductor type and cross-section, line fittings, etc. Moreover, the use of High Temperature Low Sag conductors - a part of the advanced technology - was evaluated alongside the use of conductors of the traditional type. The optimization problem is formulated as minimization of the total annual costs. The proposed methodology is tested in the developed tool, which is realized in MATLAB software by using the Monte Carlo method, and in an overhead power line designing program - PLS-CADD. Two basic case studies for verifying the proposed power line planning solution are presented in the paper.
Permanent magnets have become more and more important in today's technology of electrical machines. This paper gives an overview of usability of different types of magnetic materials in electrical machines. The research is based on a synchronous generator construction using NdFeB, SmCo, ferrite and Alnico permanent magnets. The reason of the research is to determine, which kind of magnets are suitable for the current generator design, besides the neodymium magnet. Electromagnetic simulations of the PM generator were performed by using finite element analysis. A 5 kVA PM generator for wind power applications was designed, manufactured and tested. The test results of the prototype PM generator have been investigated and compared with the calculated characteristics and data.
This paper deals with the squirrel-cage induction machine's rotor fault diagnostics - dynamic eccentricity concretely - in nominal steady state. The particular fault diagnostic is carried out with both vibration and stator current frequency spectra analyses. Besides the machine with faulty rotor the same analyses on the machine with a healthy one are performed as a reference point. The comparison of both diagnostic methods is discussed.
This paper presents a novel Direct Power Control strategy for a three-phase grid connected multilevel inverter. The proposed DPC strategy combines discrete-time sliding mode control and predictive control. The active and reactive power are directly controlled by inverter switching states, represented by a switching vector, using the value of the power error computed from samples of phase voltages and currents. An appropriate switching vector is selected for each sampling period to minimize average value of the switching functions on the time interval on three sampling periods. The prediction of phase voltages and currents is necessary for algorithm implementation. The switching frequency is constant, and the digital control implementation is simple. The designed control system is tested using a simulation model of a three-level neutral-point clamped multilevel inverter. Simulation results confirm the design aims.
This paper is devoted to the study and control of output voltage of a conversion chain based on wind conversion PMSM using a PI controller integrated into the system, and presents a mathematical model that allows the simulation of all under the Matlab environment. This with the implementation of the direct torque control DTC for the synchronous machine supplied with a rectifier installed on the output of the PMSM after the voltage regulation loop To show the effectively of this kind of control in the amelioration of the power quality.
This paper presents an improved direct torque control (DTC) based on fuzzy logic technique. Two major problems that are usually associated with DTC drives are the high torque ripple and switching frequency that varies with operating conditions. To overcome these problems, fuzzy controllers are proposed and associated with DTC scheme. The proposed approach is shown to be able to reduce the torque and flux ripple and to improve performance DTC. The control algorithm is based on the SVM (space vector modulation) technique to provide a constant inverter switching frequency. Furthermore, to verify the effectiveness of this model, a DSP-based experimental induction motor DTC drive system is built.
This paper describes a rotor field oriented control of dual star induction motor (DSIM). The difficulty of control of the induction machine is the coupling between the torque and flux because; the changing of the load torque causes unquestionably the flux variation. However, to ensure a control separate of these two variables, the field oriented control is widely used in practice. The performance of this technique depends of changing parameters because adjusting parameters of conventional regulators is based on the system parameters. The variation of system parameters being inevitable, therefore the control loses its reliability. So, it is desirable to use independent regulators of parameters changes, order to, ensure the decoupling independently the variations of the parameters. For this purpose, we use controllers based on fuzzy logic controllers and we test system performance under the influence of parametric variations. The simulations results obtained from MatLab/Simulink are presented followed by a discussion.
This paper proposes a new method which can track the maximum power under partially shaded conditions (PSC). Global maximum power (GPmax) searching method is used in this study, that is obtained by combining incremental conductance (IncCond) and scanning approach method which utilizes duty cycle sweep to track the global maximum when the PV array operates under PSC. This method is used in photovoltaic (PV) array simulation model that established in MATLAB/Simulink simulation platform. This study shows that the proposed method can track the real maximum power point accurately.
For understanding the dynamic behavior and assessing the stability of induction generator based wind generation system, the system should be modeled accurately. Power system transient stability is usually assessed in terms of critical clearing time (CCT) of fault. CCT determines the time for which the wind generating systems can be connected to the grid, when the grid is subjected to a fault. In the literature, CCT of induction generator based wind generation system connected to the grid was determined by assuming the mechanical torque output of wind turbine as constant throughout the fault simulation. However, while determining CCT, the mechanical torque output of wind turbine, before and after the fault cannot be considered as a constant as the mechanical torque-speed characteristic of a wind turbine depends on the wind speed and the slip of the induction generator connected to the wind turbine. During fault, the slip of the induction generator changes and hence mechanical torque output of wind turbine also changes accordingly. The results of CCTs obtained by considering nonlinear mechanical torque-speed characteristic of wind turbine are presented and are compared with CCTs obtained with the mechanical torque output of wind turbine assumed constant.
This paper proposes a systematic process of a multi-objective optimal design of an axial-flux permanent-magnet motor for electric scooters. In the preliminary design, the zero-dimensional magnetic circuit model is used to determine the numbers of slots and poles and the initial size of the motor according to the driving requirements of scooter. In the optimal design process, the one-dimensional magnetic circuit model with an effective air-gap distribution function is used while searching a set of motor parameters that minimize torque ripple and maximize torque and torque density. The final design is verified and refined by the 3-dimensioanl finite element method. Experimental results on a motor prototype show that the proposed design process results in an axial-flux permanentmagnet motor with a high torque density for electric scooters.
Permanent magnet flux switching machines have been attracting revived research interests for various applications over the last decades. Those machines not only inherit most merits from the conventional permanent magnet synchronous machines but also possess a simple passive and hence robust rotor. In this paper, a comprehensive overview on the evolution of new topologies for the permanent magnet flux switching (PMFS) rotary and linear machines is presented, and performance analysis and optimization of such machines are reviewed. Particular emphasis has been placed on practical techniques of torque/force pulsation analysis and reduction. The pros and cons of those PMFS machines are appraised so as to highlight the prospective applications.
Electricity market development (EMD) emerges to be a current concern following a shift of paradigm from EMD design with focuses upon energy as the key commodity to a need to deliver a sustainable low-carbon generation future. The feasible options of EMD are set to illustrate the interaction of the policy instruments, the market regulation and the sustainable investment environment. The economic benefits and costs have to be realized systematically and in a wide perspective including technical, operational and financial dimensions. The paper suggest that the energy policy of a sustainable electricity market development is set to ensure the energy needs of the community to be met; to maintain the safe, reliable, efficient energy at reasonable prices; to minimize the environmental impact of energy production and use; and to promote the efficient use and conservation of energy. It involves a wide range of complex and interrelated technical, economic and regulatory issues. A dynamic decision making model has been developed to cope with the requirements of the multimarket trading policy framework. Fuzzy Differential Evolution (FDE) algorithm is employed to solve the multi-period stochastic optimization problem and obtain the optimum results for each time interval. Policies defining the interactive markets can accurately reflect the intended goals such as decreasing emissions and promoting renewables.
This paper presents the losses characterization on distribution transformers windings. The losses are determined through the Frequency Response Analysis (FRA), using the Finite Element Method (FEM). The losses on the windings are evaluated on a frequency range established from 100Hz to 2MHz for a specific transformer. Finally, a methodology is proposed, that can be applied to different transformers.
Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology for combating the frequency selective fading, multipath propagation, and narrowband interference in power line communication. However, OFDM systems are extremely sensitive to synchronization deviation. Slight synchronization deviation can affect the performance of OFDM systems. This paper presents a design and implementation synchronization algorithm based on constant amplitude zero auto-correlation (CAZAC) for power line communication. Matlab simulation prove that, with less computation, the proposed algorithm can complete symbol timing synchronization and frequency offset synchronization well and the performance of OFDM synchronization in power line communication is significantly improved.
The anaerobic digestion is a wastewater treatment process without oxygen. It is a very complex process with a nonlinear model of six variables. This model is complex for state estimation and automatic control. We propose a nonlinear equivalent model but for which the theories developed for the linear case can be applied easily using the LMI tools.
This paper presents a study which investigates the impact of cross-border electricity transmission capacity, as well as of generation capacity, on network reliability. Monthly empirical data on network reliability and generation and cross-border transmission capacities from 18 different European countries for a time span of 10 years is used. Results show how a higher sum of remaining generation margin and import capacity corresponds with fewer fault events in the network.
In this article we have studied transient system of the squirrel cage induction generator, we will establish the modeling of wind turbine and present different topologies that exist in the literature with a focus on their application in fixed speed realized with squirrel cage induction generator SCIG. We have tried to connect the SCIG directly to the grid without starting technical by circuit breaker, inverter or filter with Capacitor Bank.
This study implements a virtual laboratory for half bridge, full bridge and three phase voltage source inverters (VSI). Users can connected to the system from any computer having internet connection and perform any experiment by using designed user interface. Simulation models have been constructed with MatLAB/Simulink software while user interfaces have been arranged with LabVIEW software. The connection between these two software has been provided by Simulation Interface Toolkit (SIT) as uninterruptible and bidirectional. Implemented system can be used as a useful education tool for learning VSI subject.
