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Showing papers on "Grid-connected photovoltaic power system published in 2007"


Journal ArticleDOI
TL;DR: In this article, the authors proposed a high performance single-stage inverter topology for grid connected PV systems, which can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array.
Abstract: This paper proposes a high performance, single-stage inverter topology for grid connected PV systems. The proposed configuration can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array. Total harmonic distortion of the current, fed into the grid, is restricted as per the IEEE-519 standard. The proposed topology has several desirable features such as better utilization of the PV array, higher efficiency, low cost and compact size. Further, due to the very nature of the proposed topology, the PV array appears as a floating source to the grid, thereby enhancing the overall safety of the system. A survey of the existing topologies, suitable for single-stage, grid connected PV applications, is carried out and a detailed comparison with the proposed topology is presented. A complete steady-state analysis, including the design procedure and expressions for peak device stresses, is included. Necessary condition on the modulation index "M" for sinusoidal pulsewidth modulated control of the proposed inverter topology has also been derived for discontinuous conduction mode operation. All the analytical, simulation and experimental results are presented.

636 citations


Journal ArticleDOI
TL;DR: In this article, a single-stage three-phase grid-connected photovoltaic (PV) system is implemented to realize the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current.
Abstract: Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.

382 citations


Journal ArticleDOI
TL;DR: In this article, the authors evaluate the ability of PV to provide a large fraction (up to 50%) of a utility system's energy by comparing hourly output of a simulated large PV system to the amount of electricity actually usable.

375 citations


Journal ArticleDOI
TL;DR: In this article, the authors evaluate technologies that will enable solar photovoltaics (PV) to overcome the limits of traditional electric power systems, including increased system flexibility, load shifting via demand responsive appliances, and energy storage.

328 citations


Journal ArticleDOI
TL;DR: Based on the I-V curves of a photovoltaic (PV) module, a novel and simple model is proposed in this article to predict the PV module performance for engineering applications.

324 citations


Journal ArticleDOI
TL;DR: A comprehensible model is proposed which provides a better understanding of the common mode issue in single-phase transformerless PV systems and a procedure is developed to analyze the global performance, efficiency, grid current quality, and common mode behavior of a PV inverter as a function of its particular structure and modulation technique.
Abstract: The relative weight of the energy generated by means of renewable sources is constantly increasing. Among all these sources, the photovoltaic (PV) systems present the higher and more stable relative growth. However, the PV system is still too expensive and a significant effort is being done to increase the efficiency and reduce the cost. Concerning the PV inverters, this has lead to the elimination of the low frequency (LF) transformer that has been traditionally included. The LF transformer provides isolation from the grid but reduces the PV inverter efficiency and increases its size and cost. However, the elimination of the transformer might generate strong ground currents, which become now an important design parameter for the PV inverter. The ground currents are a function of the system stray elements. However, there is no simple model and procedure to study the common mode behavior of a PV system, which is required to analyze the ground currents. In this paper, a comprehensible model is proposed which provides a better understanding of the common mode issue in single-phase transformerless PV systems. In addition, a procedure is developed to analyze the global performance, efficiency, grid current quality, and common mode behavior of a PV inverter as a function of its particular structure and modulation technique. Copyright © 2007 John Wiley & Sons, Ltd.

294 citations


Journal ArticleDOI
TL;DR: In this article, a new type of hybrid photovoltaic/thermal (PV/T) collector with dual heat extraction operation, either with water or with air circulation is presented.

268 citations


Patent
11 Dec 2007
TL;DR: In this article, the authors describe a power aggregation system for electric vehicles, where individual Internet connections are established to numerous electric resources intermittently connected to the power grid, such as electric vehicles.
Abstract: Systems and methods are described for a power aggregation system. In one implementation, a service establishes individual Internet connections to numerous electric resources intermittently connected to the power grid, such as electric vehicles. The Internet connection may be made over the same wire that connects the resource to the power grid. The service optimizes power flows to suit the needs of each resource and each resource owner, while aggregating flows across numerous resources to suit the needs of the power grid. The service can bring vast numbers of electric vehicle batteries online as a new, dynamically aggregated power resource for the power grid. Electric vehicle owners can participate in an electricity trading economy regardless of where they plug into the power grid.

267 citations


Proceedings ArticleDOI
07 May 2007
TL;DR: In this paper, the authors analyze and compare the most common single-stage transformerless PV inverter topologies for single-phase and three-phase with respect to the leakage current generation.
Abstract: Renewable energy sources are getting more and more widespread, mainly due to the fact that they generate energy by keeping the environment clean. Most of these systems have an isolation transformer included, which if excluded from the system would increase the efficiency and decrease the size of PV installations, furthermore it would lead to a lower cost for the whole investment. But there are some safety issues regarding the missing galvanic isolation. This paper is aiming to analyze and compare the most common single-stage transformerless PV inverter topologies for single-phase and three-phase with respect to the leakage current generation. The best results, both for single-phase and three-phase systems, are obtained when the middle point of the input capacitors is connected to the neutral point, thereby minimizing the voltage fluctuations present at the terminals of the PV panel.

258 citations


Journal ArticleDOI
TL;DR: In this article, the effects of a high level of grid connected photovoltaic (PV) in the middle voltage distribution network have been analyzed and the emphasis is put on static phenomena, including voltage drop, network losses and grid benefits.

244 citations


Patent
09 Aug 2007
TL;DR: In this paper, the authors describe a power aggregation system for electric vehicles, where individual Internet connections are established to numerous electric resources intermittently connected to the power grid, such as electric vehicles.
Abstract: Systems and methods are described for a power aggregation system. In one implementation, a service establishes individual Internet connections to numerous electric resources intermittently connected to the power grid, such as electric vehicles. The Internet connection may be made over the same wire that connects the resource to the power grid. The service optimizes power flows to suit the needs of each resource and each resource owner, while aggregating flows across numerous resources to suit the needs of the power grid. The service can bring vast numbers of electric vehicle batteries online as a new, dynamically aggregated power resource for the power grid. Electric vehicle owners can participate in an electricity trading economy regardless of where they plug into the power grid.

ReportDOI
01 Sep 2007
TL;DR: In this article, an empirically based performance model for grid-connected photovoltaic inverters used for system performance (energy) modeling and for continuous monitoring of inverter performance during system operation is presented.
Abstract: This document provides an empirically based performance model for grid-connected photovoltaic inverters used for system performance (energy) modeling and for continuous monitoring of inverter performance during system operation. The versatility and accuracy of the model were validated for a variety of both residential and commercial size inverters. Default parameters for the model can be obtained from manufacturers specification sheets, and the accuracy of the model can be further refined using measurements from either well-instrumented field measurements in operational systems or using detailed measurements from a recognized testing laboratory. An initial database of inverter performance parameters was developed based on measurements conducted at Sandia National Laboratories and at laboratories supporting the solar programs of the California Energy Commission.

Journal ArticleDOI
15 Oct 2007
TL;DR: In this paper, the problem of power penetration of photovoltaic (PV) systems in urban networks has been analyzed in two different environments for PV systems: rural and urban networks, where a single line has been simulated in order to evaluate the relation between the number of PV systems installed along the line and the maximum PV power installable.
Abstract: This paper presents the problem of power penetration of photovoltaic (PV) systems in urban networks. After a qualitative problem description, two different environments for PV systems have been analyzed: rural and urban networks. Concerning the rural network, a single line has been simulated in order to evaluate the relation between the number of PV systems installed along the line and the maximum PV power installable. In the second part of this paper, possible problems due to power penetration have been examined concerning a clustered PV system that will be installed in the city of Torino (Italy) within the ambit of the EU project called POLYCITY.

Journal ArticleDOI
TL;DR: In this paper, the application aspects in the industry of hybrid photovoltaic/thermal (PV/T) systems with water heat extraction is presented, and the systems are analyzed with TRNSYS program for three locations Nicosia, Athens and Madison that are located at different latitudes.

Journal ArticleDOI
TL;DR: In this paper, the impact of PV surface orientation and inclination on grid-connected photovoltaic system performance under maritime climates was investigated using validated TRNSYS simulations, and the maximum annual PV efficiency, the inverter efficiency, system efficiency, performance ratio (PR) and PV savings were estimated annually, seasonally and on monthly bases for various surface inclinations and orientations.

Journal ArticleDOI
TL;DR: In this paper, a tethered solar power satellite (Tethered-SPS) consisting of a large panel with a capability of power generation/transmission and a bus system which are connected by multi-wires is proposed.

Proceedings ArticleDOI
01 Sep 2007
TL;DR: In this article, the authors present a novel current pulsation smoothing parallel active filter (CPS-PAF) which is independent from the inverter topology and his operation mode.
Abstract: The newest technology on decentralised grid-connected PV systems is the "AC-PV Module", which is characterised by a number of clear advantages over conventional large PV systems. Single stage topologies seem to be a rather attractive solution, for these applications, since in generally they are characterised by high efficiency, low cost and simple structure with high reliability due to reduced components count. On the other hand in single-phase AC-PV Module inverters, the power that is transferred to the power network has a large amount of power pulsation at twice line frequency. So a large ripple of voltage and current appears at the PV module output. Taking into account that there is a close correspondence between the power that flows from a PV module and the point of operation, this fact leads to reduced PV power generation. In order to overcome this defect, this paper presents a novel current pulsation smoothing parallel active filter (CPS-PAF) which is independent from the inverter topology and his operation mode. Purpose of the proposed CPS-PAF is the elimination of the low frequency PV current ripple. So the PV module can be operated close enough to the maximum power point and consequently the PV generated electricity power is maximised. The CPS-PAF conception, control and effectiveness are validated by PSpice simulation and experimental results accomplished on a laboratory prototype.

Journal ArticleDOI
Il-Song Kim1
TL;DR: A robust maximum power point tracker using sliding mode controller for the three-phase grid-connected photovoltaic system has been proposed in this paper and it shows robust tracking property against modeling uncertainties and parameter variations.

Proceedings ArticleDOI
07 May 2007
TL;DR: In this paper, the leakage current in a 1.5 kW PV installation is measured under different conditions and used to build simulation model to study the influence of the harmonics injected by the inverter on the leakage currents.
Abstract: For low-power grid connected applications a single phase converter can be used. In PV applications it is possible to remove the transformer in the inverter in order to reduce losses, costs and size. Galvanic connection of the grid and the DC sources in transformerless systems can introduce additional leakage currents due to the earth parasitic capacitance. This currents increase conducted and radiated electromagnetic emissions, harmonics injected in the utility grid and losses. Amplitude and spectrum of leakage current depends on the converter topology, on the switching strategy and on the resonant circuit formed by the ground capacitance, the converter, the AC filter and the grid. In this paper, the leakage current in a 1.5 kW PV installation is measured under different conditions and used to build simulation model. The installation includes a string of sixteen PV panel, a full bridge inverter and a LCL filter. This model allows studying the influence of the harmonics injected by the inverter on the leakage current.

Proceedings ArticleDOI
01 Nov 2007
TL;DR: A comprehensive comparison of different MPPT algorithms in terms of their tracking efficiencies, cost effectiveness, complexity of realization etc is given in this article, where the methods are classified according to the parameters they use in finding MPP, viz, PV voltage, PV current, output voltage, and output current.
Abstract: Use of solar energy using photovoltaic (PV) arrays is emphasized increasingly and regarded as an important resource of power energy in the coming years As the power supplied by PV arrays depends upon the insolation, temperature and array voltage, it is necessary to control the operating point to extract the maximum power from the PV arrays Number of methods for maximum power point tracking (MPPT) has been reported in the literature This paper aims to give a comprehensive comparison of different MPPT algorithms in terms of their tracking efficiencies, cost effectiveness, complexity of realization etc Here the methods are classified according to the parameters they use in finding MPP, viz, PV voltage, PV current, output voltage, and output current

Journal ArticleDOI
TL;DR: The Univer Project as discussed by the authors consists of four grid connected PV systems of 200 kW p fully integrated into the Jaen University buildings, in order to provide the University Campus with more than 8% of its electricity needs, i.e. 210 MWh/year.

Proceedings ArticleDOI
12 Dec 2007
TL;DR: In this article, a circuit-based piecewise linear PV device model for dynamic and transient power system studies is proposed, which facilitates understanding of the PV device and its behavior in the connected circuit.
Abstract: Recent interest in distributed generation (DG) due to the opening of the electricity market and the need for alternatives to conventional fossil fuel-based electricity generation has revived interest in grid-connected photovoltaic (PV) systems. Studies need to be performed at the power system level to examine the impacts of grid-connected PV systems and several models for PV arrays have been proposed in the literature for this purpose. However, the complexities of these models and the difficulties of implementing them in software programs can be deterrents to their use. This paper proposes a simple, robust and flexible piecewise linear PV device model for dynamic and transient power system studies. The circuit-based nature of the model is beneficial because it facilitates understanding of the PV device and its behavior in the connected circuit. Software implementation is straightforward and it can even be constructed using standard software library components, as demonstrated using PSCAD/EMTDC.

Patent
13 Feb 2007
TL;DR: In this paper, a utility grid consisting of a centralized control means (110), an intermittent renewable power source (200) for generating electrical power; at least one further power generation system (300); and at least local controller (400) for controlling the total power output of the power source.
Abstract: A utility grid (100) is provided, the utility grid (100) comprising a centralized control means (110), an intermittent renewable power source (200) for generating electrical power; at least one further power generation system (300); and at least one local controller (400) for controlling the total power output of said intermittent renewable power source (200) and said at least one further power generation system (300), wherein the centralized control means (110) is connected with the at least one local controller (400) and adapted to request a desired total power output from the local controller (400).

Journal ArticleDOI
TL;DR: In this paper, a new maximum power point tracking algorithm based on current control for a single stage grid connected photovoltaic system is presented, where a variable step size for the change in reference amplitude during initial tracking helps in fast tracking.

Journal ArticleDOI
TL;DR: The presented method for solving the problem has paved the way towards the general model for optimal sizing of all stand-alone PV systems that have some type of energy storage, as well as optimal size of PV power plant that functions together with the storage hydroelectric power plant.

Patent
27 Sep 2007
TL;DR: An integrated voltaic energy system incorporates a bio-friendly DC power generator with a photovoltaic (PV) system connected to feed a main service panel and a utility grid.
Abstract: An integrated voltaic energy system incorporates a bio-friendly DC power generator with a photovoltaic (PV) system connected to feed a main service panel and a utility grid. A plurality of inverters are connected one each, to a respective output of one of a plurality of photovoltaic (PV) solar arrays. The outputs of each of the inverters are connected to a main service panel and a utility grid. A further inverter is connected to the DC power generator and in parallel with the other inverters. The DC power generator is also connected to each of the PV solar panel inverters through a switch operated at a specific time manually or automatically. When switched the DC power generator feeds all of the inverters. A resistor/capacitor structure is connected between the DC power generator and each inverter. A self-powered timer may control the output level of the DC power generator.

Journal ArticleDOI
TL;DR: In this paper, the construction and performance of a distributed power generating system of photovoltaics (PV) using solar energy estimation is described. But instead of conventional batteries, a new storage device, called energy capacitor system (ECaSS), is used for its various advantages.
Abstract: This paper describes the construction and the performance of a distributed power generating system of photovoltaics (PV) using solar energy estimation. Instead of conventional batteries a new storage device, called energy capacitor system (ECaSS), is used for its various advantages. A procedure is described to estimate the PV output power by calculating solar radiation. To calculate the daily insolation, Hottel's equation and Liu-Jordan's equation have been used with some modification. The accuracy of the procedure is verified by comparing the calculated solar radiation with the practically measured one. To apply the procedure even in cloudy/rainy weather, the characteristic of the PV output in different weather conditions has been studied using 1-day-ahead weather forecasts. With an aim to set the optimum amount of buy power, a simulation program has been developed. The system is being operated in optimal economic mode in different weather conditions. The financial benefit and load-leveling capacity of the system have been studied and presented here. It was found that the system provides an excellent economic benefit for nonflat price of electricity and load-leveling facility with a good overall efficiency.

Journal ArticleDOI
TL;DR: In this paper, the performance of PV systems is evaluated and analyzed not only for component perspective but also for global perspective by reviewing one year of monitoring results and loss factors of PV system.

Patent
13 Mar 2007
TL;DR: In this paper, a tracking solar power system is described, which includes a solar power substructure and a platform having a first degree of freedom relative to the platform, and a receiver arranged to receive energy from the solar collector.
Abstract: A tracking solar power system is disclosed. The tracking solar power system includes: a solar power substructure and a platform having a first degree of freedom. The solar power substructure is mounted on the platform in a manner such that it has a second degree of freedom relative to the platform. The solar power substructure may include a solar collector and a receiver arranged to receive energy from the solar collector. The receiver may be mounted in a manner that avoids shading of the solar collector during operation. The solar collector may have an area focus at the receiver. The solar power substructure may include a non-concentrating solar power substructure.

Journal ArticleDOI
TL;DR: This paper tries to contribute to the analysis of the problem of dynamic characterization of photovoltaic inverters by means of an electronic system that both measures the real evolution of the characteristic curves of PV arrays at outdoor operation and then recreates them at the laboratory to test PV inverters.
Abstract: The increasing number of photovoltaic inverters that are coming on to the PV market stresses the need to carry out a dynamic characterization of these elements and their maximum power point tracking (MPPT) algorithms under real operating conditions. In order to make these conditions repeatable at the laboratory, PV array simulators are used. However, actual simulators, including the commercial simulators, recreate only a single or small set of PV array characteristic curves in which quite commonly theoretical calculations are included in order to simulate irradiance and temperature artificial variations. This is far from being a recreation of the real and long dynamic behavior of a PV array or generator. The testing and evaluation of the performance of PV inverters and MPPT algorithms has to be carried out when the PV system moves dynamically according to real operating conditions, including processes such as rapidly changing atmospheric conditions, partial shadows, dawn, and nightfall. This paper tries to contribute to the analysis of this problem by means of an electronic system that both measures the real evolution of the characteristic curves of PV arrays at outdoor operation and then recreates them at the laboratory to test PV inverters. This way the equipment can highlight the different performances of PV inverters and MPPT techniques when they operate under real operating conditions. As an example, two commercial inverters are tested and analyzed under the recreated behavior of a PV generator during 2 singular days that include processes of partial shading and fast irradiance variations. Copyright © 2007 John Wiley & Sons, Ltd.