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EPE-PEMC 2008 - Topic: Renewable Energy Sources
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	A Novel Approach To Photovoltaic Powered Water Pumping Design   By Michael James Case	[View]   [Download]
Abstract: Modelling a photovoltaic (PV) system is generally a complex, time-consuming and computationally intensive exercise. This paper presents a simplified approach to using component efficiency and de-rate factors to generate a design estimate for a stand-alone, true North orientated, direct-coupled, PV powered water pumping system.
	A Research Platform for a Smart-Blade Wind Generation System   By J. Davey	[View]   [Download]
Abstract: A research platform, which is designed for a novel smart-blade wind turbine system, is presented. The proposed platform, which allows for the integration of different renewable sources, consists of a smart-blade wind turbine, a Permanent Magnet (PM) generator, a rectifier, a hybrid super-capacitor/battery energy buffer, and a boost and bi-directional converter. The PM generator, designed for the power profile of the smart-blade turbine, is driven by an induction motor drive to emulate the wind conditions. The research platform is implemented in a Simulink/MATLAB environment with a dSPACE interface for real time control. It has a controller for peak power point tracking (PPPT) and a user interface for real time metering, and is expected to facilitate rapid prototyping and energy related research.
	A Simple, Low Cost Design Using Current Feedback to Improve the Efficiency of a MPPT-PV System for Isolated Locations   By Herman Fernández	[View]   [Download]
Abstract: This work presents an efficiency improvement of a simple maximum power point tracking (MPPT) configuration, achieved by current feedback. The output current provided by the photovoltaic (PV) panel is used as the signal controlling the duty cycle of the PWM converter that regulates PV panel power output. The system performance is analyzed with the help of an accurate PSpice model of the PV cells developed for this application and experimentally improved. The results, both simulation and experimental, show that the proposed improved MPPT circuit is highly efficient. Since this is a simple, rugged and low cost system, it is ideal for applications in isolated locations in the less developed countries.
	A Single-Phase Active Power Filter Based in a Two Stages Grid-Connected PV System   By Kleber C. A. De Souza	[View]   [Download]
Abstract: In this paper a single-phase active power filter based in a two stages grid-connected photovoltaic system with is presented. The proposed system can not only inject PV power into utility but can act always as an active power filter to compensate the load harmonics and reactive power such that the input power factor is unity independently of the solar radiation. In sunny days, the system processes all the reactive and active load power and the excessive power from the PV module can be fed to the utility. On the other hand, on cloudy days for instance, if the PV power is not enough, the system processes all the reactive load power and the shortage of load active power is supplemented by the utility. Besides, just using one current sensor, the control strategy is simpler and of easy practical implementation.
	Active Filter Action of Inverter Exciting Induction Generator for Wind Power Generation   By Noriyuki Kimura, Tomoyuki Hamada, Katsunori Taniguchi and Toshimitsu Morizane	[View]   [Download]
Abstract: This paper shows new induction generation system for wind power generation. This system has the voltage source converter (VSC) exciting induction generator and the PFC converter to transfer the real power. Rated power of the VSC is minimized by transferring all the real power into the PFC converter. However, the harmonic components in the current from the VSC has larger peak than expected for the fundamental component. Therefore, active filter action to eliminate these harmonic components in the current from the VSC is investigated in this paper. Simulation results show the reduction rate of 1/5 of harmonic components by the active filter action.
	Analysis of Wide Area Integration of Dispersed Wind Farms Using Multiple VSC-HVDC Links   By S. González-Hernández	[View]   [Download]
Abstract: Two multi-terminal HVDC topologies are investigated in this paper to connect large-scale wind farms to the grid: two single-input single-output HVDC corridors and a double-input single-output double HVDC corridor. The first topology has two DC links operating in parallel which implies using four converter stations. The second topology has two DC corridors both connected at the output end to a single HVDC dual-input station by means of a DC busbar, which implies using three converter stations. The first topology collects power generated from widely dispersed wind farm sites, whilst the second topology is intended to efficiently interconnect nearby wind farms. The simulations results presented in this paper are building blocks towards the development of platforms helpful in the design and testing of new control strategies for operating multiple interconnected HVDC corridors. The steady state and transient performance of each topology is clearly presented throughout various study cases. The modeling and simulation work has been carried out using Simulink©.
	Analysis of Wind Farm and Multilevel Converter Interactions in Medium Voltage Networks Under Steady-State and Transient Conditions   By J. Sosa-Ruiz	[View]   [Download]
Abstract: The research work presented in this paper focuses on analyzing the steady-state and transient operation of a wind farm interconnected to the medium voltage network through a Voltage Source Converter with Neutral Point Clamped structure, VSC-NPC. As first part of the analysis, a number of wind speed variations are carried out to observe the steady-state performance of the system. For transient conditions, two particular study cases are performed in the test network: a) the occurrence of voltage sag, b) the occurrence of voltage swell. The simulation results illustrate the favorable impact of the multilevel controller on the distribution network performance.
	Direct Controls in Voltage-Source Converters - Generalizations and Deep Study   By Károly Veszprémi	[View]   [Download]
Abstract: The well-known principle of the direct torque control applied mainly to squirrel-cage induction motor drives can be generalized and applied to other machines, quantities, converters and systems. These are: other AC machines (double-fed induction and permanent magnet synchronous machine), active and reactive power, direct power control of the line side converter, direct controls of both of the converters in a DC link inverter. The idea is the same for all of them and can be generalized. Looking deeper into the operation of the direct controls, some special effects can be found: different resulting error bands and switching frequency in different operation modes of the converter, large delay in reference tracking. These can badly affect the operation of the control: larger (not the expected) error, larger switching frequency, slower control. Methods are given against them: modified switching tables, increasing the number of sectors, selecting proper sector orientation.
	Experimental Results of a Hybrid Wind/Hydro Power System Connected to Isolated Loads   By Mehdi Nasser	[View]   [Download]
Abstract: Variable speed hydro power plants allow to compensate and to smooth the fluctuating wind power when feeding isolated loads. This is shown experimentally in this paper with the help of a 3 kW laboratory test bench able to emulate a hybrid wind/hydro power system. The test bench is equipped of a doubly fed induction generator based small hydro power plant emulator associated with a fixed-speed wind generator emulator. This kind of wind generator is often used in small or medium power isolated networks. Tests show that the frequency and voltage are well controlled in spite of load variations.
	Generator Selection for Offshore Oscillating Water Column Wave Energy Converters   By D. L. O'Sullivan	[View]   [Download]
Abstract: In the field of wind energy, electrical generator solutions have converged on a small number of technologies, for specific technical and economic reasons. This paper investigates whether a similar rationale exists within the field of oscillating water column, wave energy converters. The predicted performance of the various generator options within a typical wave regime is validated by means of a time-domain MATLAB/Simulink model. The suitability or otherwise of brushed machines in the offshore marine environment is examined in detail. Each generator configuration is then modelled and the annual energy output for a typical wave climate assessed with consideration being given to the impact of speed control on the energy output.
	Grid Connection of Multi-Megawatt Clean Wave Energy Power Plant under Weak Grid Condition   By Kai Rothenhagen	[View]   [Download]
Abstract: The WaveDragon is a 7 Megawatt Wave Energy Converter, that is currently developed for clean offshore energy production. The system will be floating several kilometres off the Pembrokeshire coast, Wales, UK, and transfers energy using a submarine power cable. Key interest is the control of the power take-off system at disturbed voltages and under weak-grid condition due to long submarine cable and remote, rural location. A multireference frame controller is implemented for harmonics compensation. A parameter estimator is implemented to estimate the grid impedance. Simulation and measurements results from a laboratory test setup that illustrate properties of developed method are shown.
	Improved Sizing Method of Storage Units for Hybrid Wind-Diesel Powered System   By A. M. Tankari, B. Dakyo and C. Nichita	[View]   [Download]
Abstract: This paper deals with the segmentation of frequency domain to achieve DC bus stability by efficient design of storage and control principle. The wind energy disturbances measured on DC link are actively filtered by flywheel and battery storages to provide smoothed and secured behaviour of diesel engine. This is obtained by cascaded low pass filters applied to currents control when the dc link voltage is assumed constant. Thus, the templates, the degree of filters selectivity influence the sizing of storage units. This study focuses on the flywheel and battery sizing taking in to account wind energy path dynamics. Simulation results provide first step considerations for energy management tied to energy periodicity and system effectiveness.
	Improving Connection and Disconnection of a Small Scale Distributed Generator Using Solid-State Controller   By M. M. R. Ahmed	[View]   [Download]
Abstract: Self excited induction generator is extensively used in renewable energy sources such as small & large wind farms, small hydroelectric power plant and recently in micro combined heat and power systems µCHP. When connecting this unit to the grid a high transient current will flow. There will be a large, very fast, magnetic inrush current similar to that which occurs when a transformer is energised. This paper presents a solid state controller using CoolMOS devices for improving connection and disconnection of the Induction generator to and from the grid. The behaviour of the grid with connection/disconnection of the induction generator (islanding) through solid state controller have been simulated. Experimental model for solid state controller has been built using CoolMOS devices. Both simulations and experimental tests based on a laboratory 1.1 kW induction generator driven by a dc motor are clearly compared and show that the proposed controller are reliable and cost effective.
	Modeling and Optimal Sizing of Hybrid Renewable Energy System   By Rachid Belfkira	[View]   [Download]
Abstract: This paper presents a new methodology of sizing optimization of a stand-alone hybrid renewable energy system. The developed approach makes use of a deterministic algorithm to minimize the life cycle cost of the system while guaranteeing the availability of the energy. Firstly, the mathematical modeling of the principal elements of the hybrid wind/PV system is exposed showing the main sizing variables. Then, the deterministic algorithm is presented and implemented to minimize the objective function which is equal to the life cycle cost of the hybrid system and finally, the obtained results are exposed and discussed.
	Multi Objective Distributed Generation Planning Using NSGA-II   By Muhammad Ahmadi	[View]   [Download]
Abstract: With the increasing share of distributed generation in electrical energy supply, the proper planning procedure for using these units, has become more vital for power system planners. In this paper, the application of multi-objective optimization techniques for siting, sizing and determination of the proper technology to be used, has been investigated in such a way that, the load demand during the planning horizon is met and the technical and environmental constraints are satisfied. Unlike the traditional optimization methods used in power system optimization, NSGA-II multi-objective optimization algorithm does not consider techno-economical and environmental parameters in the constraints of optimization problem. This method optimizes them simultaneously as multiple cost functions to find out nondominated solutions set, named Pareto optimal front, instead of aiming to find single solution.
	Multipolar Double Fed Induction Wind Generator with a Single Phase Secondary Winding   By Leonids Ribickis	[View]   [Download]
Abstract: The project concerns the practical applications of multipolar induction machines as generators for small and medium wind turbines. Such a multipolar generator should be built in a way that the primary and secondary windings are placed on the stator, and the rotor is tooth-like without windings, with each tooth equivalent to one pole pair. The most reliable design is that with a single-phase secondary winding, which provides efficient control of the generator.
	Optimisation of Wind Power PMSM to Grid Conversion System   By Ince Kayhan	[View]   [Download]
Abstract: Wind energy conversion systems have become a focal point in the research of renewable energy sources. Due to rapid advances in the size and power rating of wind generators as well as development of power electronics. These electrical utilities generate and provide energy in AC form. As the wind energy to electrical power conversion is rather expensive we concentrate on efficiency increase inside electrical system which can be obtained at moderate costs. The cost per power at grid inversion point shall be as low as possible. This paper describes the implementation, design and performance of a 70 W small wind turbine with two different generator-converter combinations and the analysis of rectifier design with Si-, MOSFET and Schottky diodes for battery charge applications. Three-phase full bridge rectifiers are compared on the basis of topology, cost, efficiency, power consumption and control complexity. The power conversion system includes a pulse-width modulation (PWM) rectifier coupled to a battery load.
	Output Maximization Using Direct Torque Control for Sensorless Variable Wind Generation System Employing IPMSG   By Yukinori Inoue	[View]   [Download]
Abstract: A variable-speed wind power generation system, based on direct torque control (DTC) of an interior permanent magnet synchronous generator (IPMSG), is proposed herein. The proposed system can achieve the MPPT control without wind speed in addition to the speed and position sensorless control as well as the current control method. DTC has several advantages such as simple system configuration, easy control of flux-weakening, and it doesn't need a position sensor. In particular, the proposed control method can maintain the voltage and current at the rated value in the high speed operating region. Furthermore, as the armature resistance is the only necessary parameter, the system is insensitive to parameter variations. The performance of the proposed wind generation system was validated experimentally.
	Photovoltaic System MPPTracker Investigation and Implementation using DSP Engine and Buck-Boost DC-DC Converter   By Dimosthenis Peftitsis, Panagiotis Bakas and Anastasios Balouktsis	[View]   [Download]
Abstract: In this paper, solar radiation simulation using clearness index kt, hour of day ωs and day of year n is studied. Daily distributions of solar radiation are presented for various clearness indexes kt. Additionally, taking into account the studies about solar radiation, a photovoltaic array system and a DC/DC buck - boost converter are studied. Simulation of the whole system is presented focusing on DC/DC converter's control strategy so that the system operates in maximum power point (MPP) and converter's output voltage remains constant. Incremental conductance algorithm is used for maximum power point tracker (MPPT) implementation. A simplest method for controlling duty cycle D and photovoltaic array's voltage by using a new variable d = D1/1-D is proposed. Simulation results are shown and analyzed. For the implementation of this system, the dsPIC30F2010 Microchip's microcontroller was programmed to provide pulses to the semiconductor element of the DC-DC converter in order to track the Maximum Power Point (MPP) of the photovoltaic array.
	Research Control of Electric Systems in Wind Generator Systems   By Stefan Winternheimer	[View]   [Download]
Abstract: The problem of the operation's quality improvement of existing control systems of the wind-turbine electric plant is investigated in dynamic processes. The computer model of dynamic processes of considered system is developed for the decision of the given problem. On the basis of modern optimization methods and by means of computer simulation the optimization of existing control systems of the wind-turbine electric plant is executed. The new method of the model predictive control is offered for the researched electric system.
	Rotor Turn-to-Turn Faults of Doubly-Fed Induction Generators in Wind Energy Plants - Modelling, Simulation and Detection -   By Vincenz Dinkhauser	[View]   [Download]
Abstract: This work considers the seldomly treated case of rotor turn-to-turn fault of a doubly-fed induction generator. This fault can take place where the doubly-fed induction generator is a standard solution in wind power stations. For investigations an error-adoptable three phase machine model is derived and simulated. Furthermore the model is integrated in a wind energy plant model and simulated for a turn-to-turn fault in one rotor phase. Motor current signature analysis, wavelet transformation and the Luenberger observer are used for detection and are compared.
	Soft Switching Boost Converter for Photovoltaic Power Generation System   By Doo-Yong Jung	[View]   [Download]
Abstract: In this paper, a soft switching boost converter for solar power system is proposed. It is a topology, which raises efficiency for DC-DC converter of photovoltaic PCS (Power Conditioning System). And it minimizes switching losses by adopting soft switching method using resonance. It analyzes the operation characteristic of topology which was suggested through simulation, and proves the validity by analyzing loss and efficiency at real operation with experiment.
	Soft Switching Multi-Phase Boost Converter for Photovoltaic System   By Joo-Hyuk Lee	[View]   [Download]
Abstract: In this paper, we proposed soft switching multi-phase boost converter. A high efficiency power conversion device is required to obtain constant voltage from solar cells of which output voltage fluctuates very severely by irradiance and temperature. Using the proposed converter, we can control input voltage that fluctuates within operation range to constant output voltage, and it can reduce input current ripple and output voltage ripple. In addition, using ZVS (Zero Voltage Switching) and ZCS (Zero Current Switching), switching losses are reduced. We performed simulation and experiment for the proposed soft switching multi-phase boost converter.
	Stand-Alone Photovoltaic Generation System with Combined Storage Using Lead Battery and EDLC   By Hiroaki Nakayama	[View]   [Download]
Abstract: This research is mainly concerned with a stand-alone photovoltaic (PV) generation system for low power DC applications placed where the commercial AC grid connection is not supported. In this paper, basic and improved circuit topologies and the control schemes of stand-alone photovoltaic generation system are proposed. To prevent battery from deep discharge, Electric Double Layer Capacitor (EDLC) is incorporated into the proposed systems as combined energy storage device in parallel with conventional lead battery. The fundamentals of operating performances and effectiveness of proposed stand-alone PV system are illustrated and evaluated on the basis of a practical point of view.
	Static and Dynamic Response of a Photovoltaic Characteristics Simulator   By Anastasios Ch. Nanakos	[View]   [Download]
Abstract: In this paper a simulator of photovoltaic generators with programmable electrical characteristics is presented. The proposed system has the ability to generate the current-voltage curves of photovoltaic modules under any desirable insolation and temperature conditions. The system is also capable of integrating any maximum power point tracking algorithm under a unified control. The simulator's aim is the introduction of a faster, spherical and more effective approach in experimental investigation of photovoltaic systems, either in standalone or grid connected applications, independently from the atmospheric conditions. Towards this aim, the use of a DC power supply, controlled through a data acquisition card by appropriate algorithms, is proposed. These algorithms are implemented on a personal computer. Special effort was given in the development of a simplified user interface that monitors and controls the entire system offering effortless and faster conclusions.
	Testing of the Grid-Connected Photovoltaic Systems Using FPGA-Based Real-Time Model   By Robert Stala	[View]   [Download]
Abstract: The paper describes FPGA-based real-time simulation method of photovoltaic systems. FPGA devices are widely used for power electronic systems control, but the same chip can have implemented real-time model of controlled system. Prototyping the control circuit before application in power system increases the safeness, and can reduce time and costs of implementation. FPGA-based prototyping of power systems enables research of the system sensitivity on parameters variations, or topology conceptions. The paper presents examples of designs of the FPGA-based models of PV array, PV grid-connected transformerless systems with single phase inverter and L and LCL filters, the dc/dc converter. The conception of FPGA-based realization of spectral analysis is also presented.
	The Measurement on the Solar Cells in Liberec City   By Jiri Kubin	[View]   [Download]
Abstract: In the years 2005 - 2007 was realised the project "Pilot project of the power-produsing yield of the solar photovoltaic system in our climatic conditions for requirement of the supplying of the information and monitoring system of Liberec city". The project was solved at Technical University of Liberec (TUL) with the cooperation of High School for Electrotechnics and Mechanical Engineering in Liberec (SPŠSE). The project was financed by statutory city of Liberec. The paper deals with realisation of the project, measurements proceeding and some particular results.
	The Operation of Power Electronic Converters in Photovoltaic Drive Systems   By Marek Niechaj	[View]   [Download]
Abstract: The paper presents most important inferences, that have arisen from the research about technical, energetical and economical properties of Photovoltaic Drive Systems (PDS), especially at an angle of conditions of use of different power electronic converters and their operation terms in such systems. The research has been done by availing material models (laboratory stands) and mathematical models (computer simulations). The short description of the most important features of different PDS structures, with presenting their block diagrams, is done. The schematic diagram of simple, and relatively inexpensive, stand-alone PDS without electrical buffer source (e.g. electrochemical accumulator), and with DC commutator motor with permanent magnet excitement, is presented. This system may be applied for irrigation of cultivable lands, or for water circulation and filtration for swimming pools or fountains.
	The Use of Switched Reluctance Generator in Wind Energy Applications   By Eleonora Darie	[View]   [Download]
Abstract: Using of the wind energy has become increasingly important as a renewable energy source and therefore is an increasing interest in exploiting it using a Switched Reluctance Machine as a generator and optimize its characteristics in this domain. This work analyzes the generator mode of the Switched Reluctance Machine in the direct coupling to the turbine shaft and coupled to the shaft through a gearbox.
	Wide Bandwidth Power Flow Control Algorithm of the Grid Connected VSI Under Unbalanced Grid Voltages   By Zoran Ivanovic, Marko Vekic, Stevan Grabic, Evgenije Adzic and Vladimir Katic	[View]   [Download]
Abstract: The main contribution of this paper is the new wide bandwidth power flow control algorithm of the grid connected VSI under unbalanced grid voltage conditions. The algorithm is based on simple control structure and does not demand any filter for obtaining symmetrical components, e.g. notch or anti-resonant filter. Proposed control structure applies dual vector current control, based on regulation of positive and negative sequence components. The main advantages of the suggested control method are wide controller bandwidth, as well as possibility to obtain controller parameters by using standard tuning techniques. Comparing it with the previous solutions, this control strategy eliminates oscillating components in both, active and reactive power. However, as a consequence nonsinusoidal grid current waveforms will appear. The effectiveness of proposed control algorithm is verified by detailed switching simulation model.