Showing papers on "Grid-connected photovoltaic power system published in 1994"

Electric power supply system

Abstract: This electric power supply system includes an air conditioner serving as load, a solar photovoltaic cell for supplying power to the air conditioner, and a system power control circuit and further including a commercial power source for use in combination with the solar photovoltaic cell for supplying additional power when insufficient, power is supplied from the solar photovoltaic cell to the air conditioner In an operation state of the air conditioner, the system power control circuit operates to regulate an operating point of the solar photovoltaic cell and variably regulate the supplied power from the solar photovoltaic cell while comparing required power of the air conditioner with the supplied power from the solar photovoltaic cell

Linkage type solar light power generating device with abnormality checking function for solar battery module

Abstract: PURPOSE: To provide a linkage type solar light power generating device with the abnormality checking function for the solar battery module which detects solar battery output voltages by strings and can automatically check a solar battery output and perform safe and secure maintenance management. CONSTITUTION: The linkage type solar light power generating device 1 consists of a solar battery array 2 and a linkage inverter 3, and the DC power generated by the solar battery array 2 is converted by the linkage inverter 3 into AC power of the same quality as a system power source 4 to perform linkage operation. The AC power is supplied to a load 5 and its excessive power returns to the system power source 4 as a tidal current. The solar battery array 2 is constituted by connecting plural series-connected solar battery modules in parallel and serial components of the solar battery modules are regarded as strings S 1 -Sn n . The output voltage Vs s1 and Vs n of the respective strings S 1 -S n are compared with an input voltage V in to detect and specify abnormality of strings. COPYRIGHT: (C)1996,JPO

Analysis of wind driven grid connected induction generators under unbalanced grid conditions

Abstract: A wind driven induction generator feeding power to the grid has been analyzed under the abnormal condition of unbalanced grid voltages. Using the symmetrical component and double revolving field theory, appropriate equivalent circuits and model equations have been derived for the generating mode with suitable realistic modifications. It is emphasized that the active and reactive power components and their directions for both positive and negative sequence systems need to be properly identified in order to obtain the cumulative response of the generator under different wind power conditions. In view of the fact that the reactive power is drawn from the grid while the active power is fed into the grid, the extent of variations in power fed to the grid and the reactive VAr due to unbalanced grid voltages for different wind power conditions need to be estimated to provide guidelines in the design and operation of the wind energy conversion system. Both experimental and theoretical results for a 3.7 kW laboratory model have also been presented, to validate the theoretical formulations, extendable to large units. Extensive data have been presented and discussed for a 55 kW unit installed in site. >

A novel high-concentration PV technology for cost competitive utility bulk power generation

Abstract: This paper describes an innovative design for a nominal 20 kW, integrated, high-concentration (260/spl times/) photovoltaic (IHCPV) system which has been developed for cost-effective, utility-scale bulk power generation. This technology set a new world record for efficiency: 20.3% under STC (18.5%, >20 kW at PVUSA operating conditions). High-concentration PV systems offer several advantages for low cost power generation: (1) cost reduction through the optimum utilization of silicon, (2) higher conversion cell (hence system) efficiency at concentration vs. one-sun, and (3) inherently higher capacity factor in high direct normal insolation areas because of its built-in tracking. Previously little progress has been made in deploying HCPV for large-scale electricity generation because of: (1) the lack of a stable, high performance, high-concentration solar cell, and (2) the high cost associated with the PV modules, structure, tracking system, and ancillary equipment. With the arrival of a stable high performance cell developed by AMONIX, high-concentration PV systems can now be realized. A novel integrated system concept greatly reduces the costs associated with system hardware and labor by: (1) integrating the load bearing structure and the Fresnel lens/receiver plate elements eliminating the need for separate modules, and (2) use of a manufacturing-worthy receiver plate which makes use of "circuit-board" construction techniques. A full-scale 20 kilowatt IHCPV system has been deployed, and test results which validate the system design are reported.

Control of an optimized converter for modular solar power generation

Abstract: Important drawbacks of solar power generation are the DC-wiring and fusing needed for the serial and parallel connection of solar panels. These problems can be reduced to AC wiring and fusing by using a modular set up of panels together with integrated single phase DC-AC power converters on a power level of approximately 200 W. A general applicable model has been developed for the coupling of two single-phase systems by a voltage link with small storage capacitance. It allows the decoupling of the pulsating mains power from the panel. Based on this model, which avoids the need of large filters, a sophisticated control principle has been developed. The result is a power converter which allows the operation in the maximum power point without any power pulsation In the solar panel. The required reactive elements, and therefore the size of the power converter, are very small. >

Solar powered pumping system

Abstract: A solar water pumping system for home use utilizing amorphous solar panels and circuitry for maintaining proper power to the system. Three reference voltages in combination with switching circuitry achieve this purpose by constantly monitoring input and output voltages and allowing a non-discontinuous switching between solar power and battery power.

Development of a new utility-connected photovoltaic inverter LINE BACK

Abstract: A new utility-connected photovoltaic inverter called "LINE BACK", which is suited to small-scale photovoltaic generation systems for use in private households, has been developed. The inverter converts DC power generated by rooftop photovoltaic cells into AC power, and provides it to house loads connected to the utility line. When photovoltaic power is greater than the loads, the excess power is fed to the utility line through a reverse power flow. The inverter has several special functions such as a utility protection relay, maximum power point tracking (MPPT) control, automatic operation with photovoltaic power, detection of islanding operation, and utility voltage compensation for reverse power flow. These functions and characteristics conform to the "Utility-Connected System Technical Guidelines" revised by Japan's Ministry of International Trade and Industry in March 1993. >

Photovoltaic system using Buck-Boost PWM Power Inverter

Abstract: This paper presents a buck-boost PWM power inverter and its application for residential photovoltaic system. The PWM power inverter is realized by driving a inverter constructed with a high frequency buck-boost chopper in the discontinuous conduction mode (DCM). Photovoltaic system with the power inverter has the following advantages: (1) The power generated by the photovoltaic array can be transfered to the load and the utility line under any array voltage, (2) Isolation between the photovoltaic array and the utility line is performed by a small high frequency reactor operating as energy storage element, (3) There is no need of a reactor to link the utility line, (4) Unity power factor operation is provided, (5) So the system configuration is very simple. The input-output characteristics of the system is analyzed. As the result, the ripple component of the array current and the power flow between the interface and the utility line are derived, and verified experimentally.

Performance of modular grid connected PV systems with undersized inverters in Portugal and the Netherlands

Abstract: Preliminary results on the design and performance of three multi-array grid connected PV systems on flat roofs are presented. From the results it can be concluded that inverters can at least be undersized to 65% of the PV peak power without any significant loss of energy production. These results confirm the findings from model calculations carried out as a part of the design process.

Sizing procedure for photovoltaic systems

Abstract: The purpose of this study is to establish a comprehensive sizing procedure for photovoltaic (PV) systems. To establish it, the knowledge about PV system design is acquired by analyzing existing PV systems which have been designed optimally and interviewing with expert PV engineers. The acquired knowledge has been systematized as a sizing procedure for PV systems. It has the following features. It covers wide varieties of PV system configurations including stand-alone systems, hybrid systems and utility-connected systems. It is based on an analytical method and could size not only PV arrays but also batteries, inverters and diesel generators. It makes PV system design optimal at the practical level on the basis of experiential knowledge. The proposed sizing procedure has been confirmed that it enables appropriate design of PV systems. It should contribute to wide spread of PV systems in the future.

A development of compact and reliable protective control unit for grid connected small residential PV systems

Abstract: In the future, serious problems may arise with the maintenance of power quality, stability and safety of electric utility grids interconnected with low quality private PV power systems, without adequate protection measures being taken. The safety problem is the most important factor for electric utilities in Japan and therefore the reliability of islanding protection of such power systems must be checked because the phenomenon will directly affect the safety of personnel and utility facilities. In order to solve this problem, a reliable and compact protective control unit for residential PV power system application was developed by CRIEPI. It is confirmed that the unit shows excellent reliability for interconnected power system islanding protection.

Development, testing and first installations of an integrated solar roof system

Abstract: There are some aspects of PV power systems which must be carefully considered in the detail design stage. These are a consequence of the nature of the PV conversion (i.e. that the efficiency reduces with increasing temperature), of the requirements of the building envelope (i.e. weatherability) and safety requirements (i.e. high voltage DC systems). This paper reports on a program to design, test and commercialise a PV power system within these constraints. The concept was tested in full scale prototype in the indoor solar simulator at the University in Cardiff, both for operational performance and for durability and weatherability. A first installation has just been completed in Oxford, UK.

Avoided cost benefits of PV on diesel-electric grids

Abstract: EDRL has been assessing the effects on plant operation and avoided cost benefits of using PV power systems on diesel-electric grids in Canada's northern communities. Modelling results to date show that the major impact of PV on a diesel grid is the energy credit associated with reductions in fuel consumption. In addition, although PV has little effect on runtime, it reduces generator starts which can be a benefit with those which are not kept pre-heated when on standby. This paper discusses the results of this analysis and briefly presents a 3 kW/sub p/ grid-connected PV power system which is being installed in the remote community of Iqaluit. This work is part of the PV for the North program.

Analysis of bidirectional PWM converter for application of residential solar air conditioning system

Abstract: In conventional solar air conditioning systems, the diode rectifier is used to build up DC link voltage from an AC utility source. The diode rectifier is simple and cheap but the reversal of power flow cannot be made. It can derate the utilization of solar cells and there problems of low power factor and harmonics at the AC input side have also occurred. Hence, in addition to peak power cutting in summer, some advantages can be obtained by adopting PWM power converters in solar air conditioners. As a result, the characteristics of the PWM power converter, such as low distorted current waveform and unity power factor are obtained. The proposed system is also verified by examining the dynamics of the PV power system to step load change as well as power reversal testing.

Recent test results of 6 commercial inverters for grid connected PV systems

Abstract: Test results of 6 commercial inverters for grid connected PV systems in the power range up to 5 kW are given. The considered aspects include: energy efficiency, power point tracking efficiency, start-up power, power quality, conformity to EMC standards, acoustic noise and susceptibility to electromagnetic noise. The results are obtained with the PV test facility of ECN. The results show that in the last few years considerable progress has been made concerning the performance of grid connected inverters which are available on the European market. In general the efficiency is over 88% over a wide power range, with a peak efficiency of about 92%. Most inverters comply with standards concerning power factor, harmonics, EMC and acoustic noise.

Photovoltaic power system applications

Abstract: This article is an overview of Photovoltaic Power System applications. Photovoltaic power system range in size from watts to megawatts. They are the most modular of all electric power generating systems. PV systems produce electricity for a wide variety of applications. They can be placed in almost any location in the world, and beyond when space applications are included. When PV power for watches, calculators, and similar consumer electronic products is included in the definition of PV power system, system sizes are even smaller and applications more numerous.

Grid-tied PV system modelling: how and why

Abstract: A critical part of Ascension Technology's operation and monitoring of numerous grid-tied photovoltaic (PV) power systems for the US Environmental Protection Agency's PV Demand-Side-Management Demonstration Projects is to insure that these PV systems are operating properly and that problems can be diagnosed by scrutiny of the data being retrieved from these systems. The objective of the work reported here was to develop accurate, flexible PV array and inverter models, and apply them to help understand the performance of the PV systems and address issues which are important to inverter designers/manufacturers, systems designers and system operators. Graphical display of measured PV system performance, along with modelled performance has proven useful for remotely diagnosing a wide range of PV power system phenomena and quantifying their impact: partial array shading, partial array snow cover, PV array max-power voltage lying outside the inverter tracking window (both an array sizing concern, as well as an inverter design issue) and inverter power limiting. Modelling was also key to discovering and understanding an inverter control problem.

Power conditioner for photovoltaic power generation

Abstract: PURPOSE:To provide a compact, high-performance power conditioner for linking a photovoltaic power generation unit (solar battery) to a commercial system in a private house. CONSTITUTION:A power conditioner (X) has a solar battery 6 accompanied by a monitor solar battery 5, and at least an inverter 1, an insulating transformer 2, a system connection protection unit 3, and a control unit 4 are provided in a one-body casing. The control unit 4 includes an inverter control unit 41, a load balance control unit 42, a monitor battery daylight quantity discriminating unit 43, a maximum output power control unit 44, a sequence control unit 45, and a linkage protection and detection unit 46. Then, the power conditioner is controlled and the control power is turned on or off on the basis of a daylight quantity level estimated from the monitor solar battery 5.

Optimisation of photovoltaic water pumps coupled with an interfacing pulse width modulated DC/AC inverter power conditioning device

Abstract: A proper matching of electromechanical loads to a PV array is a great problem in many PV power systems. This is mainly related to the nonlinear solar irradiance and cell temperature-dependent voltage and current characteristic of the PV array generator. A simple nonlinear optimisation technique is used to solve the load matching problem of a PV water pumping system. A number of case studies (at best and worst month solar radiation situations) are presented based on the power consumption of the load. Results show that, an optimum matching factor of 0.74 and 0.55 (at best and worst month respectively) can be achieved using 1.76 kWp M55 type PV array and M402/SP5A-7 type motor/pump with SA1500 DC/AC inverter interfacing device in this works field study area. It is possible to achieve a higher load matching factor by selecting carefully the proper size of the array and the motor/pump.

Distributed photovoltaic demand-side generation: an economic evaluation for electric utilities

Abstract: From an electric utility's viewpoint, distributed photovoltaic demand-side generation (PV-DSG) systems can be evaluated in a similar manner to other demand-side management (DSM) technologies. This study evaluates the economic benefits of PV-DSG systems, using hourly utility cost and performance data, as a function of the utility's load duration curve (LDC). The analysis focuses on one utility, New England Electric System (NEES), USA. Actual utility hourly system load data for 1991 and corresponding PV output data from a 2.2 kW (DC) grid-connected residential PV system, installed as part of the NEES Gardner project, are used for this study. At NEES's weighted average cost of capital of 8.78% the energy and capacity benefit values calculated equate to an allowable installed PV system cost of $2.41/watt. A social discount rate of 3% allows for an even higher installed cost-per-watt figure of $4.72. The higher the, allowable installed cost, the easier it will be for the PV industry to enter the utility market. These results are represented graphically as a target to emphasize the importance of the utility target market to the PV industry.

Efficient photovoltaic charging of electric vehicles

Abstract: The University of South Florida in Tampa, USA, has initiated operation of a photovoltaic (PV) system capable of a 6 kW (peak) output that can be used for simultaneous computer controlled direct DC-DC charging and utility interconnection. The PV DC-DC system is part of the 20 kW (peak), 12 bay Electric Vehicle/Photovoltaic Demonstration and Evaluation Program being conducted at the University and consists of a four bay portion of the parking facility equipped with roof mounted PV panels. These panels not only provide power for charging, but also help protect vehicles from damage caused by solar radiation. The program has been created to evaluate the potential contribution of photovoltaics as a method for offsetting the fuel cost of electric vehicles while reducing air pollution generated by power plants that are fueled by nonrenewable sources. The DC-DC charger controls the charging current of a battery pack with minimal parasitic power waste, by computer on/off control of each of four source circuits. It provides superior efficiency over DC-AC-DC charging and its cost and maintenance requirements are lower.

Technical evaluation of a dual-junction same-band-gap amorphous silicon photovoltaic system at NREL

Abstract: On December 7, 1992, a 1.8-kW/sub AC/ utility-interconnect photovoltaic (PV) system using amorphous silicon modules was brought on-line at the National Renewable Energy Laboratory's photovoltaic test site. This system was deployed to conduct an in-situ technical evaluation of the PV array (in a high voltage configuration) and system performance and reliability in a utility-interconnect application. The system is unique due to the installation of construction-grade insulation on the back of each PV module. This use of insulation is an attempt to levelize the annual array power output by elevating the operating temperature of the modules. This paper presents array and system performance data. Emphasis is placed on quantifying the effects of individual losses as well as seasonal changes on PV array and system performance.

Design considerations and performance of Maspeth a-Si PV system

Abstract: This paper describes the design and early performance of a 17‐kWp(ac) amorphous silicon (a‐Si) photovoltaic (PV) system in Maspeth, New York. The system started operating in June, 1993. The system is mounted on the roof of a warehouse operated by the New York City Transit Authority. The system was designed and installed by Integrated Power Corporation using a unique ballast‐weighted system configuration with no roof penetrations. Same‐band‐gap tandem a‐Si modules from United Solar Systems Corporation are used. The PV modules face south and slope 10 degrees from horizontal. This paper estimates the monthly system performance and reports the system’s performance during the first three months of operation.

Issues in utility-interactive photovoltaic generation

Abstract: This article examines factors affecting the application of solar Photovoltaic Power Plants to their power grid. A utility considering the use of solar photovoltaic generation should consider the following issues: power conditioning, protection, islanding, intermittent output, and installation. PV generation, like many advanced electrical technologies, will at times require improved performance from the utility system. Operating and protection practices may have to change to accommodate PV. However, operating experience and studies show that PV generation will operate well with existing electric utility systems.