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EPE 2003 - Topic 12a: Distributed Power, Renewable Energy Systems and Alternative Energies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2003 - Conference > EPE 2003 - Topic 12: POWER ELECTRONICS IN GENERATION, TRANSMISSION AND DISTRIBUTION OF ELECTRICAL ENERGY > EPE 2003 - Topic 12a: Distributed Power, Renewable Energy Systems and Alternative Energies
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	Interaction of distributed generation with power grid   By G. Blajszczak	[View]   [Download]
Abstract: The power grid (power plants, transmission network, power stations, etc.) is successfully controlled for a number of years using the same principles. However, rapid development of distributed generation causes a number of new problems which will have to be handled. This paper presents the main task in grid control, classifies and describes negative aspects of distributed generation presence and shows necessary changes in grid control strategy. Additional costs that arise because of that are also evaluated.
	Voltage control and load sharing in DC distribution systems   By P. Karlsson; J. Svensson	[View]   [Download]
Abstract: This paper addresses voltage control and load sharing in DC distribution systems. At present, DC distribution systems are utilised in, for example, telecommunication systems. Future applications could also involve distributed power systems based on renewable energy sources. The dynamic and stationary properties of voltage droop control and its load sharing abilities are investigated. The DC bus voltage droop controller gain is selected so that the loading of each source converter is equal in per unit. Both experimental and simulation results verify the operation. Experimental results regarding fault detection in DC distribution systems are also presented.
	Simplified high frequency converters in decentralized grid-connected PV systems: a novel low-cost solution   By N.P. Papanikolaou; E.C. Tatakis; A. Ciritsis; D. Klimis	[View]   [Download]
Abstract: This paper presents the design and the control strategy of a new single stage high frequency simplified converter topology for decentralized grid-connected PV systems. The proposed converter is based on the flyback converter topology operating in the discontinuous conduction mode where it behaves as a current source. Its main advantages are the very high power density and the high efficiency, due to its simple structure, as well the high power factor regulation that is achieved. A design methodology is developed aiming the achievement of a converter with the smallest possible volume for a given power. PSPICE simulation results will be exhibited, highlighting the advantages of the proposed converter topology. The validation of the design and control methodology is also confirmed by experimental results accomplished on a100 W laboratory prototype.
	Machine-Converter Complexes (MCC) for electrical energy production and transmission   By J.M. Kauffman; Yu. Shakaryan; Yu. Vinitsky	[View]   [Download]
Abstract: Advanced methods for electrical energy production and transmission by the use of electrical machines and frequency converters in the stator or (and) rotor circuits are described. Benefits of such systems are highlighted. New approaches to the control principles are shown. Different generating sets and their combinations are described.
	Active system for voltage control in wind generation units   By A. A. Bayod Rújula; J. Mur Amada; J. Sallán Arasanz	[View]   [Download]
Abstract: A combined system that permits a wise control of reactive power in WECS (Wind Energy Conversion Systems) without harmonic generation is presented. In the case of asynchronous generator, it uses the thyristors of the usual soft-starting system to connect a TCR (thyristor controlled reactor) and a smallrated active filter (PWM-VSI) so its implementation is very economical.
	Power converter system for Flexible Reliable and Intelligent Electrical eNergy Delivery System (FRIENDS)   By Y. Hayashi; T. Ise; K. Tsuji	[View]   [Download]
Abstract: Power quality issue is becoming more and more important due to wide spread use of computerized and power electronic equipment, which requires high quality power. On the other hand, some loads require lower price power rather than such high quality power. Unbundled power quality service is paid much attention under the circumstances of diversification of needs of customers for quality and price of electric power[1][2]. Moreover, distributed generators (DGs) such as photovoltaic generations (PV) and wind turbines (WT) will be introduced to distribution system more and more, and reverse flow of active power has possibility to cause new problems in the distribution system such as voltage rise of distribution line and protection problem. Flexible, Reliable and Intelligent Electrical eNergy Delivery System, which is called FRIENDS, has been proposed as one of promising distribution system for such requirements, and intensive studies are under way[3][4][5]. One of features of this system is introducing power converter system called Quality Control Center (QCC) into the system for realization of unbundled power quality service and easy installation of DGs. In this paper, Details of AC-type Quality Control Center as power converter system are shown. Main characteristics are that power fluctuations from unstable DGs such as wind turbine and photovoltaic generation can be compensated in proposed QCCs and unbundled power quality service is operated. Simulation and experimental results about these characteristics are shown here.
	Comparison of complete and reduced models of a wind turbine using Doubly-Fed Induction Generator   By J. Morren; S.W.H. de Haan; P. Bauer; J.T.G. Pierik; J. Bozelie	[View]   [Download]
Abstract: Wind turbines equipped with a Doubly-Fed Induction Generator are increasingly popular in the power range above 1 MW. For power system stability studies of large wind parks it is desirable to apply reduced models of the machine and the converter in order to limit the computation time. Several reduced models have been developed and evaluated. With respect to the generator, models with and without transient terms in the fluxes have been compared. With respect to the converter, models with and without PWM operation have been used. The whole system has been modelled both in abc coordinates and in a rotating d-q reference frame. Especially a model with transient flux terms and without PWM operation, which has been modelled in the d-q reference frame, has shown to be accurate and fast.
	Matrix converter and conventional schemes in rural power generation systems   By J.M. Pacas; M. Schulz	[View]   [Download]
Abstract: Different conventional schemes utilized in small power variable speed generation plants for rural enviroments, including a solution that utilizes a matrix converter, are analysed. The analysis covers the realisation effort, the power quality, the reliability and the maintenance.
	A novel single-stage inverter for the AC-module with reduce low-frequency ripple penetration   By S. Baekhoej Kjaer; F. Blaabjerg	[View]   [Download]
Abstract: This paper presents a new DC-AC inverter for photovoltaic (PV) and single-phase applications, in particular for the AC-Module. The benefits associated with this new inverter are a low number of components and the possibility of an inherent power decoupling. A novel power-decoupling scheme is also presented. The aim for the power decoupling is to reduce the amount of capacitance inside the inverter. The decoupling scheme can also be used together with the boost DC-AC inverter. The decoupling is a must for achieving a good utilization of the PVmodule. This is hard to achieve with today’s single-stage inverters without using large electrolyticcapacitors. A large capacitor involves a decreased lifetime, which this solution overcomes.
	Digital control of a single-phase voltage source inverter for renewable energy sources   By K.J.P. Macken; J. Van den Keybus; R.J.M. Belmans	[View]   [Download]
Abstract: This paper presents a digital control technique for a single-phase voltage source inverter being part of an utility interface for renewable energy sources. The purpose of the control is to transfer the power produced by the renewable energy source to the utility system. The control design is discussed and validated with experimental results
	Autonomous high power variable speed wind generator system   By L. Leclercq; A. Ansel; B. Robyns	[View]   [Download]
Abstract: A high power Wind Energy Conversion System (WECS) connected to isolated loads is considered in this paper. As the WECS must work without auxiliary source, ensure the balance generation – consumption, set the adequate frequency and voltage, it is combined to a Flywheel Energy Storage System (FESS). For the WECS, we have considered a Variable Speed Wind Turbine (VSWT) coupled to a Permanent Magnet Synchronous Generator (PMSG). A control strategy of this system is proposed. As loads are not necessary balanced, it is proposed to control directly the alternating line-toline voltage of the network with the help of resonant controllers. The performance of the proposed global system is analyzed with the help of simulations.
	Controller for dispersed generators to support grid voltage and frequency stability   By S. Wijnbergen; S.W.H. de Haan	[View]   [Download]
Abstract: A control method is proposed to let dispersed power sources participate in voltage control and primary frequency control. The method is based on independent control of active and reactive current of the power electronic interface, within limits imposed by the prime mover and the converter rating. The controller design is treated in detail. Both simulation and experimental results are shown.
	A study of doubly fed wind power generator under power system faults   By I. Serban; F. Blaabjerg; I. Boldea; Z. Chen	[View]   [Download]
Abstract: The paper presents an investigation made on the doubly-fed-induction generator for wind power applications and on its behavior under a three-phase grid short-circuit. A vector controlled back-to-back power electronics converter is connected in the rotor circuit of the generator. A rather accurate decoupled active and reactive power control strategy and simulation results are presented in detail. A three-phase short-circuit on the grid is modeled and analyzed, the effects are discussed and some potential mechanisms to improve the performance during the fault and to reduce the destructive effects of this fault are described. It is concluded that the limitation of the rotor currents references is, accorded to this study, the best method to reduce the dominant stator and rotor current peaks during short-circuit with approximate 50%.
	Innovative distributed photovoltaic power plant concept   By A. Neusser; D. Lafore; Y. Lausenaz; P. Mestre; P. Malbranche; P. Boulanger	[View]   [Download]
Abstract: Power electronics offer new possibilities in photovoltaic system design. With them, low loss charging and improved management of storage facilities, in our case a battery park, are feasible. The new concept of a photovoltaic system presented here is a modular power supply built out of small autonomous standardized units. Controlled energy exchanges between these units might also be realized. This new concept can be implemented in the presented way thanks to power electronics. A bi-directional step-up/stepdown DC/DC converter or a zeta or a buck converter can take the role of one battery charger. After the detailed description of the new concept, its advantages in comparison to classical systems and storage management are pointed out.
	Maximum-power-point tracking method of photovoltaics using only single current sensor   By T. Noguchi; H. Matsumoto	[View]   [Download]
Abstract: This paper describes a novel strategy of maximum-power-point tracking for photovoltaic power generation systems. A unique feature of this method is capability to seek the maximum power point using only a single current sensor, i.e., a Hall-effect CT. Output power of the photovoltaic can be estimated with an average value and ripple amplitude of the detected current. A conventional hill-climbing method is employed to seek the maximum power point, using the output power obtained from only the current sensor. In this paper, not only a theoretical aspect of the proposed method is described, but also experimental results are presented to prove feasibility of the method.
	Energy modelling of a lead-acid battery within hybrid wind / photovoltaic systems   By O. Gergaud; G. Robin; B. Multon; H. Ben Ahmed	[View]   [Download]
Abstract: Within the scope of full-scale energy modeling of a hybrid wind / photovoltaic system coupled to the network, our focus herein lies in a battery set-up that makes use of the CIEMAT model. The implementation and energy-based analysis of this model are conducted with emphasis on the continuous estimation of battery capacity. A measurement vs. model results comparison is then performed under actual operating conditions.
	Low order harmonic cancellation scheme for multiple PV grid-connected inverters   By M. Armstrong; D. J. Atkinson; C. M. Johnson; T. D. Abeyasekera	[View]   [Download]
Abstract: In grid connected multiple string inverter systems, it is normal to synchronise the output current of each inverter to the common network voltage. Any current controller deficiencies, which result in low order harmonics, are also synchronised to the common network voltage. The harmonics produced by individual converters show a high degree of correlation and tend to be additive. Each controller can be tuned to achieve a different harmonic profile so that harmonic cancellation can take place in the overall system, thus reducing the net current total harmonic distortion level. However, inter-inverter communication is required. A novel technique is presented for producing cancellation of low order harmonics in gridconnected inverters for photovoltaic systems. A randomised based control in each inverter causes a different harmonic profile so that harmonic cancellation can take place in the overall system, thus reducing the net current total harmonic distortion level.
	A UPF Power Conditioner with a Simple Maximum Power Point Tracker for Grid Connected Variable Speed Wind Energy Conversion System   By A. B. Raju; B. G. Fernandes; K. Chatterjee	[View]   [Download]
Abstract: In this paper, a simple control strategy for an optimal extraction of output power from grid connected variable speed wind energy conversion system(VSWECS) is presented. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator(PMSG) through a gear box and two PWM power converters. Output power from PMSG is first converted into dc, inverted and then it is fed to the grid. Both the power conversions are performed at unity power factor and the dc link voltage is maintained constant. The maximum power point tracker(MPPT) extracts optimum power from the wind turbine from cut-in to rated wind velocity by sensing only dc link power. The complete system has been simulated for various wind velocities. The control algorithm is implemented on TMS320F243 DSP and the viability of the scheme is confirmed through experimental studies.
	Sliding mode control laws for variable speed wind power systems   By I. Munteanu; N. Laverdure; S. Bacha; D. Roye	[View]   [Download]
Abstract: This paper deals with the design of a controller for variable speed and fixed pitch horizontal axis wind turbines (HAWT), using the sliding mode control theory. Two kinds of controller are presented, according to two different control goals. The first one aims to obtain the optimal energy conversion regime, by keeping the optimal tip speed ratio. The second one consists on a power tracking scheme. In both cases, the proposed solution deals directly with the nonlinear model of the wind power system, which is an advantage versus, for instance, the control strategies requiring linearization. Theoretical results and Matlab & Simulink simulations are presented, allowing a comparative evaluation of the two laws. A study of robustness is also presented.
	Simulation of a wind energy conversion system based on a doubly-fed induction generator   By F. Poitiers; M. Machmoum; R. Le Doeuff	[View]   [Download]
Abstract: This article proposes the study and the simulation of a variable speed wind energy conversion system based on a doubly fed induction generator (DFIG). The DFIG is directly connected to the grid at the stator side and via a bidirectional converter at the rotor side. This configuration authorizes speed variations of ± 30 % around the synchronous speed and the converter is then dimensioned for a third of the nominal power of the machine. The wind variations are established using a spectral decomposition of the wind speeds and are applied to the model of the wind turbine. The model of this turbine is made using the traditional equations describing the mechanical operation of a classical horizontal wind turbine. The resulting torque reference is then applied to the DFIG which is controlled in order to obtain a maximum output power at each wind speed.
	Novel test bench to develop power electronics for fuel cells   By L. Schindele; H. Späth	[View]   [Download]
Abstract: Fuel Cell (FC) systems show great promise for use in electricity generation, transport and portable power supplies. This paper describes a test bench to investigate the influence of different switching power electronic devices on fuel cells. Furthermore, online identification of fuel cell parameters is possible.
	Single-phase photovoltaic energy conversion system based on a new maximum-power-point-tracking algorithm   By D. Casadei; G. Grandi; C. Rossi	[View]   [Download]
Abstract: A new maximum power point tracking algorithm for single-stage converters connecting photovoltaic panels to a single-phase grid is presented. The algorithm is based on the analysis of the current and voltage low-frequency oscillations introduced in the PV panels by the single-phase utility grid. The proposed control technique allows the generation of sinusoidal grid currents with unity power factor. The proposed algorithm has been developed to allow an array of PV modules to be connected to the grid by using a single-stage converter. This simple structure yields higher efficiency and reliability when compared with standard solutions based on a two-stage converters configuration. The proposed maximum power point tracking algorithm has been numerically simulated and experimentally implemented by means of a converter prototype connected to a single-phase grid. Numerical and experimental results are presented in the paper, showing the effectiveness of the proposed system.
	LQG-based multivariable control of a doubly-fed induction machine for a variable-speed wind energy generation   By C. Darengosse; F. Poitiers; M. Machmoum	[View]   [Download]
Abstract: This paper presents a control strategy of the doubly-fed induction machine used in generating mode (DFIG). This device is intended to be implemented in a variable-speed wind-energy conversion system connected to the grid. In order to control the active and reactive power exchanged between the stator of the machine and the grid, the rotor is fed by a bi-directional variable frequency converter. The DFIG is controlled by a state-space regulator derived using LQG methodology. Its performances are compared with controller presented in previous work in term of robustness, reference tracking and sensibility to perturbations.
	Grid connected asymmetric full-bridge multilevel inverter   By H. Valderrama-Blavi; C. Alonso; B. Estibals; L. Martínez-Salsmero; J. Maixé	[View]   [Download]
Abstract: In this paper we present a multilevel inverter topology that economizes devices compared to other topologies having the same number of levels. This device reduction makes this inverter suitable for photovoltaic, fuel cell or wind energy applications. To assure that the injected current has a sinusoidal waveform in phase with the grid voltage, a control strategy derived from sliding mode theory is applied.
	A control method to charge series connected ultra-electric double layer capacitors suitable for photovoltaic generation systems   By N. Mutoh; T. Inoue	[View]   [Download]
Abstract: A new combined control method suitable for photovoltaic (PV) generation systems is described. The new method combines a maximum power point tracking (MPPT) control method to make it possible to take the maximum power which solar arrays can generate at any time irrespective of the weather and a control method to charge the maximum power by the MPPT control method to series connected ultra-electric double layer capacitors (ultra-EDLCs) while maintaining the electric capacity which solar arrays can generate at that time. The MPPT method controls the output current of the solar arrays so that the output power converges on the maximum power in the prediction line previously determined based on the linearity between the maximum output power and the optimization current. The MPPT method is characterized by having the ability to enlarge the controllable range of the output power to lower solar radiation in comparison with the conventional hill-climbing method. The charging method controls the current and voltage so as to be charged at around the power generated at that time while supervising the maximum voltage and allowable temperature of each series connected EDLC. The combined control method makes it possible to charge with the maximum power generation from solar arrays into ultra-EDLCs. Effectiveness of the methods is verified by simulations and experiments.
	Optimisation of power electronics of small stand alone wind power stations   By A. Schmidhofer; H. Weiss; F. Konetschnik	[View]   [Download]
Abstract: Wind power stations with rating up to several kW are installed as stand alone generation systems far from the public power supply. Especially at non-optimal locations an optimal wind exploitation is essential. Wind turbines have simple standard components with non-controllable power regulation possibilities due to the high costs of complicated mechanical systems like e.g. pitch control. That is why the electrical equipment like generator system and power electronics components plays an important role. A self-built 2 kW wind power station is introduced. The wind turbine is connected via a gear to the permanent magnet synchronous generator (PMSM). A special designed and controlled DC/DC step down converter manages the energy storing into the battery.
	A novel control strategy for power smoothing in variable speed wind diesel systems   By R. Cárdenas; R. Peña; G. Asher; J. Clare	[View]   [Download]
Abstract: In wind-diesel systems, wind speed variations can produce frequent start/stop cycles of the diesel engine in response to periods of low wind speed. Consequently, an energy buffer is very important in these schemes to avoid unnecessary deterioration of the diesel engine. In this paper, control systems for the operation of a variable speed wind-diesel system, including power smoothing, are analyzed. The power smoothing system comprises a front-end converter, a flywheel energy store and a vector controlled induction machine. The wind energy conversion system comprises a variable speed wind turbine and back to back converters for interfacing the variable speed generator to the load. Control of the power smoothing system compensates for the effects of wind variation and load disturbances. The operation of the whole system including the wind turbine, front-end converter, control of active and reactive power supply is discussed as well as the vector control system of the induction machine driving the flywheel. Simulation results for the entire system for a number of operational conditions are presented. Experimental results are provided for the control of the flywheel energy store.