Showing papers on "Grid-connected photovoltaic power system published in 1992"

Self-tuning control of a solar power plant with a distributed collector field

Abstract: A self-tuning proportional-integral controller for a solar distributed collector field that is based on a pole-assignment approach employing serial compensation to cope with measurable external disturbances is presented. The scheme is compared with the more commonly adopted parallel feedforward approach by both simulation and implementation on the plant itself. >

Battery charge controller characteristics in photovoltaic systems

Abstract: Typical strategies for battery charge regulation and load control in stand-alone photovoltaic (PV) systems are presented. Several charge algorithms (methods of controlling current to the battery) are presented, along with terminology used by the PV industry for battery charge controllers. Information gained from an extensive evaluation of commercially available charge controllers and data collected from tests on PV systems in the field are discussed. An overview of battery performance characteristics needed for the successful design and long-term operation of PV systems is presented with the intent of soliciting feedback on the information presented from the battery industry. >

Modular power conditioning unit for photovoltaic applications

Abstract: The concept of modular power conditioning systems for photovoltaic (PV) applications is discussed, with particular reference to the battery as the load. A MOSFET-based power conditioning unit (PCU) of 1 kW capacity is discussed in detail along with a control algorithm to track the maximum power point. Maximum power from each PV array is extracted in spite of any mismatch in the array characteristics. One system controller is capable of handling several PCUs, simplifying the design and resulting in a lower cost of the system. It was observed that the maximum power point tracking (MPPT) increases the power output by abut 10% over a day as compared to the direct connection. >

Analysis and experimental evaluation of a new MPPT converter topology for PV installations

Abstract: A novel maximum power point tracking (MPPT) converter topology, based on the parallel power conversion technique (PPCT), to enhance the energy conversion efficiency in photovoltaic (PV) systems is analyzed. Extensive experimental verification of the operation of this converter topology, compared to other topologies, is included. Based on these results, the MPPT topologies are evaluated against each other for utilization in PV systems. The PPCT topology has the highest efficiency compared to the other power converters on the same basis. This increased efficiency is experimentally evaluated and analytically described. It is shown experimentally that the PPCT results in a meaningful enhancement of the basic converter efficiency, from 76% to 94% with a 12 V battery and from 85% to 95% with a 36 V battery. >

Optimizing the integration of photovoltaic systems with electric utilities

Abstract: The author introduces a comprehensive simulation package whereby the optimal size, operation, performance and economics of a photovoltaic (PV) system can be determined in the utility-integrated mode. The central issue is to present a single definitive optimization model. A stepwise analytical methodology starting at the solar resource and culminating in the value of the PV system in terms of avoided costs is provided. The methodology includes processing of the solar irradiance; identification of the PV system's configuration and operational features; identification of real-time system controls in the presence of PV generation; security assessment in the presence of PV and production costing and capacity expansion analysis with PV. The optimization package is subdivided into five different subgroups based on their respective purposes in the context of the overall scheme. The author describes the functions of each subgroup. >

Self-deploying photovoltaic power system

Abstract: A lightweight flexible photovoltaic (PV) blanket is attached to a support structure of initially stowed telescoping members. The deployment mechanism comprises a series of extendable and rotatable columns. As these columns are extended the P.V. blanket is deployed to its proper configuration.

Sunlight power generating system

Abstract: PURPOSE:To utilize the output of a solar battery effectively by maintaining the voltage at a power receiving terminal normally even if the voltage of an electric power system is high. CONSTITUTION:A solar battery array 1, an inverter 2, which converts the DC generated by the solar battery array 1 into the AC, and an electricity storage means 7 are provided. The output of the inverter 2 is connected to a commercial electric power system 5 through an interconnection protective device 4. When the voltage of the commercial electric power system 5 exceeds a specified value, the generated energy of the solar battery array 1 is stored in a secondary battery 72 constituting the electricity storage means 7.

The ground testing of a 2 kWe solar dynamic space power system

Abstract: The solar dynamic power system chosen by NASA for Space Station Freedom SSF requires validation in the vacuum/microgravity environment. The planned ground tests of a proof-of-concept 2 kWe solar dynamic system with address subsystem integration issues involving such major system components as the behavior of thermal energy storage materials. This test scheme will be scalable to 25 kWe, and will be flight-configured to incorporate features of the SSF's power module design.

Generator excitation system performance requirements arising from grid system considerations

Abstract: The author examines the generator excitation system performance requirements arising from transmission system considerations with particular reference to the existing National Grid Company plc grid system and its future developments. The developing trends of higher per unit reactance generating equipment designs and increased utilisation of transmission systems over the past few decades has placed increased emphasis on excitation and other control systems to provide the compensating effects to offset reductions in system stability margins arising from these design trends. At the same time developments in computational system analysis and control equipment design techniques have improved considerably to enable design of excitation and other control equipment with appropriate characteristics. >

Integrated solar power satellites: An approach to low-mass space power

Abstract: Previous concepts for solar power satellites have used conventional-technology photovoltaic arrays, feeding a power collection and transmission system connected to microwave tubes for direct current to radio frequency DC to RF conversion, which in turn are coupled to a phased array antenna. This paper proposes using thin-film photovoltaics with an integrated solid-state phased-array to design an ultra-lightweight solar power satellite. The status of the enabling technologies, conceptual designs, possible applications, and development steps are discussed. It is found that as these technologies evolve, their use in this design results in a potential reduction in weight by a factor of ten to a hundred over conventional concepts for solar power satellites, and increases the utility by allowing service to smaller receivers at multiple receiving sites.

Transient operation of orthoginal-core type DC-AC converter for photovoltaic power system

Abstract: Discusses transient operation of the orthogonal-core-type DC-AC converter for a grid-connection-type photovoltaic (PV) power system. In particular, they consider the transient operation when the converter is connected to and disconnected from the utility grid on the basis of simulation and experiment. Furthermore, they examine the converter behavior when a line-to-line fault occurs in the utility grid. It is shown that the DC-AC converter has excellent tolerance for various faults which occur in a PV power system. >

Centralized PV generation and decentralized battery storage for cost effective electrification of rural areas

Abstract: A novel technique for the reduction of the overall system cost of PV (photovoltaic) systems in rural areas is presented. This technique consists of centralized PV generation at a maximum power point voltage of between 90 V and 108 V, power distribution at around 85 V, and decentralized battery storage at 12 V (nominal). Maximum power point tracking (MPPT), single axis solar path tracking (daily), and reflectors are used to maximize the energy from the PV array. Decentralized energy storage in every house, with access restricted to the particular house, encourages energy management by the individual households. Load diversity is exploited by charging remaining batteries at a higher rate when some of the batteries are fully charged. Low distribution losses are obtained by charging the 12 V batteries in series, but access to the energy in the 12 V batteries is restricted to the individual households only. Experimental results are presented, including the power conversion efficiencies of the MPPT and the battery regulator, the energy conversion efficiency of a storage battery, and the increase in ampere hours from a PV panel using a three-stage solar path tracker.

Solar probe power systems concepts

Abstract: Some of the design options under consideration for providing on-board electric power for the Solar Probe Mission are discussed. Five spacecraft configurations were evaluated with slightly different power demands and volumetric constraints on the power system. This resulted in three different baseline power system designs to satisfy the five spacecraft configurations. These three current baseline power system designs use modified general-purpose heat source (GPHS) radioisotope thermoelectric generators (RTGs) similar to those launched on the Galileo and Ulysses spacecraft. The modular RTG currently under development and testing is a potential advanced alternative to the current baseline GPHS-RTG technology design.

Utility interface concerns with in-plant generation in a harmonic environment

Abstract: Industrial or commercial in-plant generators that are operated in parallel with the electric utility supply system are considered. The issues involved in industrial and commercial in-plant generation and its role in determining the amount of harmonic current injected back into the connected utility are discussed. A detailed example shows the consequences of in-plant generation in a plant with harmonic loads. System operating conditions, harmonics, and other related issues are also discussed. >

Economy on a Residential Photovoltaic Power System

Abstract: This paper firstly proposes a new methodology to assess the generating costs of photovoltaic power systems for residential electric energy use and to evaluate these systems economies.We next describe the hourly computer simulation method of residential photovoltaic system operation by applying the standard meteorological data and typical daily residential load curves to make clear the following subjects; (1) the extent of the residential electric energy being served by photovoltaic power system, (2) the extent of the most economical battery capacity, (3) the relation between the scale of photovoltaic system and the size and shape of residential load curve, (4) the contribution to the residential photovoltaic systems economy by the utilities purchase price of surplus power. We actually estimated the economy of residential photovoltaic power system in 2000 in Japan.As a result we found that it was difficult for residential photovoltaic power system to get economy under the cost target of Sunshine Project in 2000 and it was necessary to reduce the cost of solar cell and balance of systems furthermore.

Economic evaluation of a photovoltaic power generation introduced into an electric power system with electricity storage

Abstract: Renewable energy utilization and electricity storage will soon be introduced into the conventional electric power system. This study assumes that a photovoltaic (PV) power generation system, a set of the PV units, is installed into the electric power system with electricity storage; moreover, the effects of uncertain variation characteristics of the PV system output on the operations of the conventional power generation system and the storage units are evaluated by simulations, with cost a major consideration. According to the simulation results, it is clearly demonstrated that the costs of the PV system are influence sharply by the prediction accuracy of their output.

The Effects of Dispersed Utility Connected Photovoltaic Generation on the Distribution System

Abstract: There are technical and economic issues that have to be addressed if photovoltaic (PV) generation is to contribute significantly to a utility's total generation mix. In particular dispersed PV generation, in the form of roof mounted panels, may cause the consumer's voltage to fluctuate outside normal limits as insolation level varies. System frequency variation is also a potential problem. It is shown in this paper that PV generation systems can be designed so that voltage and frequency problems are eliminated. This may require some amount of battery or other forms of storage. Depending on costs, storage can also be used to enhance the economic benefits of PV generation.

Transmission Worth of Photovoltaic Generation

Abstract: Long distance, high-voltage electric power transmission to transfer electricity produced by solar photovoltaic (PV) systems has received little, if any, attention within the U.S. utility solar power community. In fact, current thinking among utility solar power researchers and planners has shifted from visions of centralized power stations to one of distributed, smaller generation systems. This shift of interest from centralized to distributed photovoltaic power generation, however, appears to be based in part on an unstated premise of limited land area for PV power plants within a utility's service area. Hydroelectric power planners have clearly taken a different approach. Given the limited number of good sites for large scale hydropower generation and the adverse land-use relationship between densely populated, electric power demand centers and the construction of hydroelectric facilities, long high-voltage transmission lines are typically required. In this paper an order of magnitude analysis is made of the economic feasibility of using transmission lines to transport solar photovoltaic power from sunny to cloudy regions.