Showing papers on "Grid-connected photovoltaic power system published in 1993"

A general battery model for PV system simulation

Abstract: A battery model is proposed as a tool to simulate and optimize photovoltaic (PV) / storage systems. the normalized form of the equations with respect to the battery capacity allows us to generalize its use for any type and size of lead-acid batteries. The validity of this model to represent the battery voltage evolution during charge, overcharge and discharge processes and to predict the performance of solar systems under different operational conditions is analysed. Moreover, the battery efficiency losses are presented as a function of the upper regulation thresholds of the charge controllers and the size of the array and storage systems in a domestic application in the climate of Madrid.

Multiple reflector concentrator solar electric power system

Abstract: Disclosed is a solar electric power system that utilizes multiple reflectors to concentrate sun light onto a panel of photovoltaic (PV) cells. The power system, consisting of multiple reflectors, mounted PV cells, and a heat dissipation component, is mounted on a tracker that keeps the system directed to the sun. A noteworthy feature of this system is its designed-in capability of being retrofitted with advanced reflectors, PV components, and heat dissipation components during the system's multi-year operating life. The common axes design feature of the system allows for low cost materials and manufacturing concepts. The system can operate on either a single or a dual axis tracker with active or passive cooling.

Photovoltaic power generating equipment capable of jointly using battery

Abstract: PURPOSE:To make the power generation capacity of a solar battery maximum, and to effectively utilize solar radiation energy by operating a DC/DC converter and controlling the output voltage of the solar battery so that the generated power of the solar battery becomes maximum. CONSTITUTION:At the time of supplying electric power from a solar battery 1 to an inverter 3, a DC/DC converter 5 controls an output voltage of the solar battery 1 so that the generated electric power of the solar battery 1 becomes maximum. When the generatable maximum electric power PPVL of the solar battery 1 is smaller than the consumption electric power PINV of the inverter 3, insufficient electric power obtained by subtracting the generated electric power PPVI of the solar battery from the consumption electric power PINV of the inverter 3 is supplied by electric power supply caused by discharge of a battery 4. On the other hand, when the generatable maximum electric power PPVI of the solar battery 1 is larger than the consumption electric power PINV of the inverter 3, surplus electric power obtained by subtracting the consumption electric power PINV of the inverter 3 from the generated electric power PPVI of the solar battery 1 is used for the charging of the battery 4.

Control method of parallel operation of inverter for system interconnection

Abstract: PURPOSE:To maintain the proper value of power conversion efficiency as the whole inverter system for system interconnection consisting of a plurality of inverters and a DC power supply such as a solar cell respectively. CONSTITUTION:When the sum of the output power of both inverters 2A and 2B detected by an output voltage detector 6 is smaller than a set value thereof, an electromagnetic 3C for varying interconnection among both inverters and both solar cells 1A, 1B is closed, and either one inverter selected in both inverters is supplied with electricity from both solar cells. When the sum of both output power is larger than the set value thereof, the electromagnetic switch 3C is opened. Accordingly, the inverters are operated in both combination of the inverter 2A and the solar cell 1A and the inverter 2B and the solar cell 1B, and the operation of the inverters is controlled in conformity with a specified program in a switching control circuit 7 so as to maintain the proper value of the power conversion efficiency of the inverters by the increase of the load factor of the inverters regarding the inverters selected to be worked.

Solar Photovoltaic Air Conditioning of Residential Buildings

Abstract: The use of photovoltaics (PV) for residential air conditioning (AC) represents an attractive application due to the close match between the diurnal cooling load and the availability of solar radiation. Conventional wisdom suggests that air conditioning is a process too energy intensive to be addressed by PV. Previous investigations have concentrated on the feasibility of matching PV output to vapor-compres sion machines, and the cost effectiveness of other solar cooling options. Recently, Japanese manufacturers have introduced small (8,000 Btu/hr) grid-connected solar assisted AC systems. These small room-sized systems are inadequately sized to meet air conditioning peak demands in larger U.S. homes of conventional construction practice. Previous studies considering the use of PV for solar cooling have treated the building thermal load as a fixed quantity. However, the large initial cost of PV systems ($6-$10/W peak) makes minimization of the building loads highly desirable. This paper describes a novel approach whereby the building, air conditioning and PV systems are simultaneously optimized to provide maximum solar cooling fraction for a minimum array size. A detailed hourly building energy simulation in a hot-humid climate is used to assess methods of reducing the building sensible and latent cooling loads to a practical minimum. A detailed PV system simulation is used to determine the match of the array output to that of the building’s peak loads. The paper addresses several key elements that influence the concept’s feasibility and potential economic attractiveness.

Small grid-connected solar photovoltaic generators in the UK

Abstract: This paper examines the engineering, commercial and regulatory aspects of the grid connection of small photovoltaic power systems in the UK, and compares the situation with other European countries where several thousand systems are being installed under either sponsored or independent programmes. Data was gathered from study of the European experiences and from extensive interviews within the electricity supply industry in the UK. The study concludes that the systems are technically feasible using currently available technology, although their widespread use in this country is held back by economic and organisational barriers. A technical guidelines document is also available from the study for those wishing to pursue such schemes. >

A New Approach For Reliability Evaluation Of Interconnected Power Systems

Abstract: __Abstract: Itcli:hility of iiitcrcotiiieclctl power systciiis is aii important arca of itivcstigatioti. Otic of tlic iiiiportatit atialytical mctliotls is tlic ~ i~ i i i l t ancor i s DecoiitpositionSiinulrttioti (SiDcS) [5,G].. A major drawbnclt of SiDcS nictliod is tl int tlie clliciciicy of tlie decoiiipositioti process decrcnscs rapidly as the prolxibility of tlic scts gcts siiiallcr and sitinllcr. After a few ilmntioiis, tlie iiiiitibcr of statcs Ilcitig cl~ssifietl in soiiie of tlie arcs falls to just oiic state. Coitscq~ictit~ly, t,lic tiunibcr of sets being geiieratcd is very largc for a iiiotlcrat,c iiutiiber of arcas. The nuiiiber of sets generated lias serious iiiiplicatioiis ott tlic storage requirciiiciits atid frequency calculn(ioiis which dcpciids on tlic cxatnirintioti of sribsct ititcrscctioii.

Probabilistic design of high quality power supply photovoltaic systems

Abstract: The stand-alone application of photovoltaic (PV) systems, at current industrial production technological levels, could provide a viable solution to the problem of producing electricity for users located far away from power distribution systems. The author discusses the criteria for calculating the sizes of PV peak power and energy storage of a highly reliable power supply for special loads, with the aim of reaching the desired availability level. Adopting the criteria of loss of load probability (LOLP), the sizes of PV peak power and energy storage of the system are calculated in two steps. An initial provisional calculation is made, followed by a simulation of the most critical conditions, as a sequence of days with a minimum level of irradiation calculated probabilistically. A simple iterative process is adopted to evaluate performance. >

Solar‐powered air conditioner

Abstract: We have successfully developed and industrialized a solar-powered air conditioner that operates through a combination of photovoltaic (PV) arrays and commercial power supplies. In order to achieve the most efficient operation possible from a one-horsepower inverter-type household air conditioner, we selected a PV array output of 540 W under standard test conditions, based on single-day power use patterns for air conditioners as well as on solar cell output patterns. When using a 540-W PV array, we have shown that the system can supply at least 90% of the power consumed by an air conditioner during peak power periods in summer. We have confirmed that on average the power generated by the PV array can satisfy at least 50% of the power consumed by an air conditioner in summer. We also confirmed that the system functions according to system design specifications. There is little doubt that the introduction and widespread use of this system will play an important role in reducing peak power energy requirements in summer.

Photovoltaic experiences in the electric supply for relay telecommunication station in Spain

Abstract: The are many reasons why Spain is considered one of the leaders in photovoltaic installations for telecommunications; plentiful sunshine, low population density, mountainous terrain and rapid economic growth during the last 20 years. This has resulted in the installation of hundreds of mountain-top relay stations. In many instances the transfer of energy via photovoltaics (PV) has proved cheaper than via the electricity grid, but because initial doubts concerning its reliability and correct functioning, this was not an argument for the installation of PV. The problems in PV are never due to the solar modules or the batteries, but always because of the sizing or of electronic parts such as control charge regulators, inverters or data collection system. >

Simulated Power Source Based on Output Characteristics of Solar Cell

Abstract: Numerous studies were performed so as to evaluate the performance of the photovoltaic power systems (PV systems), included maximum power control of the solar cell, effects of the PV systems on distribution feeders, long-term performance of the PV systems, etc. In order to estimate the performance of the PV systems, the output characteristics of the solar sell should be taken into consideration.In this paper, a new method of the simulated power source (SPS) to analyze the PV system is proposed. The SPS is under the control of the 10cm2 reference solar cell, so the output characteristics of the SPS is in proportion to the output characteristics of the reference solar cell not only static but dynamic.

Field experience with photovoltaic systems: Ten-year assessment. Final report

Abstract: Photovoltaic systems engineers from the Southwest Region Experiment station which is operated by the Southwest Technology Development Institute at New Mexico State University made site visits to assess the operational characteristics of 35 photovoltaic (PV) systems. A total of 76 trips were made to the 35 sites during the period from May 1983 through August 1990. During site visits, observations and field performance testing were performed. Simple system repairs were made during the site visits. Also presented in this report are operation and maintenance histories for three other line-connected PV systems. These data were taken during the latter 1980s and have been analyzed to identify system failure patterns. Observed problems fall into four general categories: failed modules; balance-of-system, direct-current component failures; downtime of power conditioning systems; and inaccurate system performance ratings. In spite of these problems, most of the 35 systems surveyed as well as the three systems analyzed are reliable energy producers. These PV systems have proven to be capable of operating unattended and to require little maintenance. Adoption of straightforward and generally low-cost changes in system, and hardware design and operation and maintenance policies holds promise for achieving even better PV system performance records in the future.

Photovoltaics vs. utility line extension in Austin, Texas

Abstract: The City of Austin Electric Utility is using stand-alone photovoltaic (PV) systems comprised of solar photovoltaic modules and lead-acid batteries to provide DC electricity to fifteen water flow meters used by the City of Austin Water and Waste Water Department. It was less expensive to provide electricity using stand-alone PV systems than through traditional electric distribution line connections. A 30-year economic analysis indicates that the photovoltaics will save the Electric Utility $61000. The savings are realized after accounting for battery replacements every five years and maintenance costs. Due to the success of the fifteen stand-alone photovoltaic installations, the Electric Utility is implementing a program to identify other cost effective applications of photovoltaic in the electric utility distribution system. >

Application of Distributed Scada System in Electric Power Plant

Abstract: The early development of Supervisory Control And Data Acquisition (SCADA) systems has been related to the implementation of remote monitoring and control functions in power system dispatch centers. Prior to the use of the digital computers, different SCADA functions were performed by separate hardware systems each of which had its own dedicated Man Machine Interface (MMI). Thus, the first digital implementation of SCADA functions was an emulation of the hard-wired analog systems in the digital coniputers using a common MMI subsystem. This phase of development is characterized with the centralized SCADA configuration where all data processing is performed at the power system dispatch center, while power plant control system participate only as input/output (110) facilities, usually without even local processing capabilities. The centralized SCADA configuration became obsolete with the advancement of computer technology and the availability of high performance 32-bit microprocessors at dramatically reduced prices in the mid 1980's. Since that time, the major challenge for SCADA systems is the distribution of various functions among a group of interconnected computers. This led to the application of distributed control systems in power plants and their incorporation into the distributed SCADA system at the level of power system dispatch centers. The benefits of such distributed SCADA processing include the improvements in SCADA performance, greater fault tolerance, easier maintenance, extensions and upgrading, as well as life-cycle cost reductions. This paper presents an evolutionary concept of distributed SCADA system development and application at the level of electric power plant. The proposed concept is under consideration for application at several hydropower plants in Yugoslavia.