Showing papers on "Grid-connected photovoltaic power system published in 1991"

Control of parallel connected inverters in stand-alone AC supply systems

Abstract: A scheme for controlling parallel-connected inverters in a standalone AC supply system is presented. This scheme is suitable for control of inverters in distributed source environments such as in isolated AC systems, large and distributed uninterruptible power supply (UPS) systems, photovoltaic systems connected to AC grids, and low-voltage DC power transmission meshes. A key feature of the control scheme is that it uses feedback of only those variables that can be measured locally at the inverter and does not need communication of control signals between the inverters. This is essential for the operation of large AC systems, where distances between inverters make communication impractical. It is also important in high-reliability UPS systems where system operation can be maintained in the face of a communication breakdown. Real and reactive power sharing between inverters can be achieved by controlling two independent quantities: the power angle and the fundamental inverter voltage magnitude. Simulation results are presented. >

Photovoltaic generation effects on distribution feeders

Abstract: As the electric utility industry looks to diversify and expand its energy mix, more and more attention is being focused on alternate energy sources such as roof-mounted photovoltaic (PV) generation systems. The principal objective of this research project is to determine if present designs for distributed photovoltaic generation equipment will operate without detrimental effect on either the utility system or the customer owned equipment. Grid-connected roof-mounted photovoltaic (PV) systems have been installed by the New England Electric System Companies on 30 houses in Gardner, Massachusetts. All 30 PV houses are in one neighborhood on the very end of one phase of a 13.8 kV feeder. To further illustrate use of the analysis techniques, they were applied to the same 13.8 kV feeder as it might be configured in the year 2018, 30 years hence, with a total of 500 PV installations averaging 6 kW each for a total installed PV generation of 3000 kW. The results not only illustrate use of the analysis techniques in a general sense but also provide realistic examples of the pitfalls that a distribution planner should look out for when designing a feeder with an expected high penetration of customer owned generation. 1 ref., 79more » figs., 23 tabs.« less

Design and optimization of a self-deploying PV tent array

Abstract: A study was performed to design a self-deploying tent shaped PV (photovoltaic) array and optimize the design for maximum specific power. Each structural component of the design was analyzed to determine the size necessary to withstand the various forces it would be subjected to. Through this analysis the component weights were determined. An optimization was performed to determine the array dimensions and blanket geometry which produce the maximum specific power for a given PV blanket. This optimization was performed for both Lunar and Martian environmental conditions. The performance specifications for the array at both locations and with various PV blankets were determined.

Solar power generating/storing system

Abstract: PURPOSE:To provide a solar power generating/storing system in which the output can be taken out efficiently from a solar cell and stored in a battery. CONSTITUTION:A solar cell PV is connected with a high capacity capacitor C which can be charged instantaneously with high current through a first charging circuit D1. The high capacity capacitor C is connected with a battery B through a second charging circuit D2 and charged when the output of the solar cell PV increases thus charging the battery B continuously from the high capacity capacitor C even after the output of the solar cell PV dropped. Furthermore, the operation can be switched depending on the conditions, e.g. the load L is fed with power from the solar cell PV when the output therefrom is high, by switching the connection of the load L between the output terminals of the high capacity capacitor C and the battery B.

Power supply system in highly-airtight heat-insulated residence

Abstract: PURPOSE:To cut down the cost of power facility and attain comfortable residence space by supplying power by a solar battery system wherein the primary components are a storage battery which charges the power from a solar battery or midnight power and a controller which controls the power charge method for the storage battery CONSTITUTION:For the charge method for the storage battery 24 of a solar battery system 21, the power is charged from a solar battery array board 22 or midnight power 23 to a storage battery 24 by the operation of the time switch 30 being set to specified time unit For example, in the daytime, the time switch 30 on the side of a solar battery board 22 is turned on, and the power generated in the solar battery board 22 is charged in the storage battery 24 through the second charge circuit S4 Moreover, late at, the time switch 30 on the side of the solar battery 22 is turned off, and the time switch 30 on the side of an AC main power source 23 is turned on, whereby the midnight power is charged in the storage battery 24 through the first charge circuit S3

Solar generator linked with system

Abstract: PURPOSE: To absorb the output fluctuation of a solar battery and suppress the load variation of a commercial power source by detecting the output of the solar battery and the room temperature with sensors, and adjusting an air conditioner when driving an inverter in liaison with AC where the outputs of the commercial power source and the solar battery are inverted. CONSTITUTION: The output of a solar battery 2 is converted into the frequency of a commercial power source 1 with the first inverter 3, and an air conditioner 5 is operated in liaison with the commercial power source 1. The air conditioner 5 rectifies 51 the AC of the commercial power source and generates the AC of VVVF with the second inverter so as to drive an air motor 53. A power detector 6 detects the output of a solar battery 2, and a temperature sensor 7 measures the room temperature and compares 9 it with reference temperature 8. When the temperature difference is zero, it adjusts the second inverter 52 by the detected value of the power detector 6, and when there is temperature difference, it adjusts the second inverter 52 by the detected value of the temperature sensor 7. Hereby, the output fluctuation of the solar battery 2 is absorbed, and the load variation of the commercial power source is suppressed, and the output of the solar battery is effectively made use of. COPYRIGHT: (C)1992,JPO&Japio

Three years performance and reliability of a 15 kWp amorphous silicon photovoltaic system

Abstract: A 15 kWp grid-connected photovoltaic system was installed in August 1988 at one of Florida Power Corporation's substations near Orlando, Florida. The photovoltaic array is made of 640 G4000 modules. The system's performance has been monitored for three years of operation, and periodic diagnostic tests have been conducted to evaluate the subsystem reliability. During the three-year period, the power output of the photovoltaic array has degraded by 25% of its original value and the array peak power efficiency is 4.0% as of August 1991. Due to the annealing effects and more favorable spectral distribution of solar irradiance in summer, the array efficiency is about 10% relatively higher in summer time than in winter period (4.4% versus 3.9%). A significant corrosion build-up on 31 out of total 640 photovoltaic modules has been observed. Relatively high leakage currents of the array, particularly under wet conditions, have also been detected. >

Economic determination of optimal plant design for photovoltaics in the utility distribution system

Abstract: A simplified value analysis tool which is to be used in optimizing the design of a distributed grid-connected photovoltaic (PV) plant is presented. The resulting distributed value information may be combined with cost information to determine the most optimal plant design. The methodology and the data necessary to apply this methodology to a specific case are presented. >

Development testing of the advanced photovoltaic solar array

Abstract: The latest design, fabrication and testing details of a prototype wing are discussed Estimates of array-level performance are presented as a function of power level and solar cell technology for geosynchronous orbit (GEO) missions and solar electric propulsion missions through the Van Allen radiation belts Design concepts are discussed that would allow the wing to be self-retractable and restowable To date all testing has verified the feasibility and mechanical/electrical integrity of the baseline design The beginning-of-life (BOL) specific power estimate for a nominal 10-kW (BOL) array is about 138 W/kg, with corresponding end-of-life (EOL) performance of about 93 W/kg for a 10-year GEO mission

Cost-effective photovoltaic applications for electric utilities

Abstract: The Electric Power Research Institute (EPRI) is working with electric utilities around the USA in a comprehensive program to identify and introduce applications for photovoltaic (PV) power systems which are cost-effective. Early applications, as these cost-effective PV systems are termed, can solve small and remote power supply problems for utilities, save money for utilities, and built an experience base with photovoltaics among electric utility engineers. EPRI's early applications program has four elements: (1) identify cost-effective applications for PV; (2) inform utility personnel of these applications; (3) assist partner utilities with cost-saving PV system installation projects; and (4) develop tools and methods for utilities to evaluate PV applications. >

Experiences and lessons learned with residential photovoltaic systems

Abstract: Small, grid-connected photovoltaic (PV) systems are the focus of interest among many utilities, who recognize the potential for PV systems to become increasingly important to their regions in the 1990s. To provide utilities with information that will help them plan for future use of PV systems, the experiences and lessons learned were summarized from three key residential PV projects: the New England Electric Photovoltaic Research and Demonstration Project (Gardner, MA), the John F. Long Properties Solar One Project (Phoenix, AZ) and the Laguna Del Mar Townhouse Project (Carlsbad, Ca). The PV systems were visually inspected and electrically tested. PV homeowners and personnel from the host utility were interviewed regarding their experiences with the PV systems. PV system performance data were analyzed to investigate the correlations between PV output and loads. Key results from this study show: (1) residential rooftops are viable locations for PV arrays, (2) homeowners react favorably to roof-mounted PV, (3) utility ownership insures that PV systems will be maintained, (4) PV output helps reduce system peak loads, (5) power conditioners are key to the reliability of PV systems, (6) utility interface issues may present barriers to customer purchases of PV systems, and (7) advantages may exist formore » utility ownership of PV systems. 14 refs., 37 figs., 23 tabs.« less

Optimum Design of a Grid-Connected Photovoltaic Power System

Abstract: As a part of various electric power sources, the photovoltaic power system are expected to be one of the important power systems in a near future The authors have developed the computer program of optimizing grid-connected photovoltaic power system from points of view of daily electric load and electrical energy cost In a grid-connected photovoltaic power system (PV system), electric power generated is supplied to distribution line and loadIn this paper, the optimum design of typical private residence with PV system in Tokyo is calculated by using the various system performance models, the cost models, the daily electric load pattern, environmental data and so onIt was found that the capacity of PV system is 26kW when the selling price of surplus power and buying price of shortage one are equivalent And then, the electrical energy cost of the optimum PV system at 2, 000 A D is estimated to be about 35yen/kWh

Dynamic switching technique for load control in a PV system

Abstract: The voltage load control of a stand-alone photovoltaic power (SAPV) system can be an indication for the optimum utilization of the system A low-cost online control by a simple electronic circuit using a switching technique for both the PV array and the storage batteries is presented This circuit makes it possible to control the load voltage, and the charging and discharging currents of the storage batteries The circuit can also rearrange the PV array cells with load variations The series and parallel cells are determined at each operating point The coordinates of the photovoltaic array N/sub p/ and N/sub s/ are obtained such that the total power is generated at the extreme condition In addition, the break-even point of the overall system is deduced as an index between the two boundaries of power generated >

Comparison of photovoltaics with solar thermal trough electric systems as a central station utility resource in the 1990s

Abstract: The approach and results of work to compare solar thermal parabolic trough systems and photovoltaic systems as utility electric generation resources in the mid-to-late-1990s are discussed. Assumptions, methodology, designs, performance simulation, value analysis, cost estimates, and economic feasibility analysis are presented. Results, based on standard utility financial criteria and avoided costs, show that central station solar power generation is not economically feasible in the 1990s for the case considered. While economic feasibility of troughs occurs in 2004 and somewhat less later for emerging PV options, incorporation of environmental or resource diversification attributes would hasten cost-effectiveness of both technologies. >

A simplified method for determining the available power and energy of a photovoltaic array

Abstract: A practical method of calculating the power and energy capabilities of a PV array source is presented in this paper. The method is based on power flow relationships with average values for constants and actural measurements of key variables, solar irradiance and module temperature on an hourly basis or other discrete time intervals. Included in this paper is an example for a PV plant and a simple procedure for constructing and validating the math model The method is applicable to any PV array configuration which is operating normally, i.e., when no PV modules are bypassed by the shunt diodes. The array can comprise one or more PV modules. The accuracy of this method is dependent upon proper selection of the values of various constants in the math model as well as how well the model has been validated. The calculation and display of maximum power capability in real-time have been implemented in several PV plants. Some of them have found it to be very useful for operation, maintenance, performance analysis,...

Field investigation of a photovoltaic power system for a telecommunications system

Abstract: Nippon Telegraph and Telephone Corporation (NTT) introduced a photovoltaic power system (26 kWp) into a microwave radio station in Hokkaido, Japan, which was monitored and evaluated from September 1989 to August 1990. The authors describe the outline and results of this investigation. The photovoltaic power system supplied on average 92% of its output from sunshine throughout the year of study, satisfying the design forecast. >

Photovoltaic Power Stations

Abstract: Photovoltaic (PV) power generation is gaining increasing importance as a renewable energy supply. From small-scale space applications in the 1960s, production of photovoltaic modules has increased to about 45 MW peak power per year worldwide. This development was accompanied by a cost reduction for solar modules to as low as 4-5 US $/Wp in 19892.

PV assisted DC and AC fluorescent lighting systems compared

Abstract: A comparison is made between efficient fluorescent lighting systems powered by AC and by DC with photovoltaic arrays providing a share of the load. The AC system requires an inverter on the photovoltaic array, and the DC system requires a DC power supply between the grid and the lighting circuit. More photovoltaic power is available for the lighting at all times when the sun is shining with the DC system. The total grid power consumed by each system is a function of power supply and inverter efficiencies, season, and TOD (time-of-day) benefits. The DC system appears to reduce summer utility peaks and summer customer demand charges further than an AC system would. >

Photovoltaic research at Pacific Gas and Electric Company

Abstract: Cost-effective photovoltaic (PV) use by utilities is anticipated to extend beyond today's small, stand-alone installations to grid support, villages and islands, and customer-sited applications before PV enters peaking and bulk power markets. PV research at Pacific Gas and Electric Company has evolved since 1980 to demonstrate the technology and stimulate utility consideration and acceptance of PV. >

Solid state regulator/charger for low power PV systems

Abstract: The different types of electronic regulator battery chargers employed in low-rating solar-powered lighting systems are discussed. A low-power photovoltaic (PV) lighting unit was built and tested which includes a basic constant-current series regulator interfacing with the PV module and the storage battery. The system is especially designed for use in remote areas to serve small farming communities. The system has proved to be practical, low in cost, and reliable. >

Novel phenomena in a 12 kW photovoltaic grid connected system

Abstract: The experimental and qualitative analysis of transient start-up and shut-down processes is given. It is reported that during a faulty transient process the photovoltaic (PV) array current maybe 10-15 times higher than the PV array short-circuit current. Possible explanations of the phenomenon observed are discussed. >