Showing papers on "Maximum power point tracking published in 1982"

Steady-State Security Regions of Power Systems

Abstract: A steady-state security region is a set of real and reactive power injections (load demands and power generations) for which the power flow equations and the security constraints imposed by equipment operating limits are satisfied. The problem of determining steady-state security regions is formulated as one of finding sufficient conditions for the existence of solutions to the power flow map within the security constraint set. Explicit limits on real and reactive power injections at each bus are obtained, such that if each injection lies within the corresponding limits, the system is guaranteed to operate with security constraints satisfied.

New solar cell power supply system using a boost type bidirectional DC-DC converter

Abstract: New solar cell power supply system is presented, in which the boost type bidirectional dc-dc converter and the simple control circuit with a small monitor solar cell are employed to track the maximum power point of the solar array. It is confirmed by the experiment that the new system has the sufficiently precise tracking operation performance and the satisfactorily high power efficiency. Also, a comparison of the power efficiencies is made with theoretically as well as experimentally on the new and the conventional solar cell power supply systems. As a result, it is revealed that the new system is superior to the conventional one in the power efficiency.

DC To AC power inverter

Abstract: The DC to AC power inverter is of the class B, C, D or E type and includes a battery, at least one power SCR and associated capacitor circuitry, at least one input winding on a main transformer core and at least one output secondary winding on the transformer core. Such inverter requires a quiescent current to establish operating current for capacitor commutation charge and includes a feedback loading circuit for feeding current generated by the quiescent current back to the battery. The inverter also includes a self-detecting load demand circuit coupled to a line from said output winding for cyclically energizing the inverter, for sensing a minimum AC load and for holding said inverter in an energized state until less than a minimum AC load is sensed during an energizing cycle. Further the invention includes automatic power factor correction circuitry for supplying full time leading power factor correction to a load, with the automatic power factor correction circuitry being sensitive to light reactive loads.

Control apparatus for D.C. power transmission system

Abstract: This invention relates to an apparatus for controlling a D.C. power transmission system having a line-commutated converter which is connected between a first A.C. system and D.C. power transmission lines and which performs power conversion between A.C. power and D.C. power, and a forced-commutated converter which is connected between the D.C. power transmission lines and having a second A.C. system and which performs power conversion between A.C. power and D.C. power. In order to control transmission power in the two-terminal D.C. power transmission system wherein the two A.C. systems are associated by direct current, a control apparatus for a D.C. power transmission system according to this invention includes a voltage detector which detects a D.C. voltage of the D.C. power transmission lines, a first control circuit for comparing the output of the voltage detector with a voltage reference signal and for controlling ignition of the self-excited converter in accordance with the comparison, a detector which detects a current which is proportional to the conversion power of the line-commutated converter, and a second control circuit for comparing the output of the current detector with a power reference signal and for controlling ignition of the line-commutated converter in accordance with the comparison.

Maximum power point tracker for photovoltaic power plants

Abstract: The paper describes two different closed-loop control criteria for the maximum power point tracking of the voltage-current characteristic of a photovoltaic generator. The two criteria are discussed and compared, inter alia, with regard to the setting-up problems that they pose. Although a detailed analysis is not embarked upon, the paper also provides some quantitative information on the energy advantages obtained by using electronic maximum power point tracking systems, as compared with the situation in which the point of operation of the photovoltaic generator is not controlled at all. Lastly, the paper presents two high efficiency MPPT converters for experimental photovoltaic plants of the stand-alone and the grid-interconnected type.

A Utility Interactive PWM Sine-Wave Inverter Configured as a High Efficiency UPS

Abstract: Conventional UPS equipment employs a tandem charger, battery, and inverter to isolate critical loads from utility disturbances and failures. Since two distinct stages of power conversion -- charger and inverter -- are required, this method is both inefficient and expensive. This paper describes a new circuit topology and operating method that uses a single four-quadrant PWM sine-wave inverter to both regulate the critical load and charge the standby battery. The complete power system consists of an inverter coupled to the utility through an inductor. The critical load is connected directly across the inverter output. This allows the inverter complete control of the load voltage and waveform. When the inverter is operated synchronously with the utility, power flow is regulated by varying the phase angle between the inverter and the utility. The phase angle is automatically adjusted using an 8-bit microprocessor to meet the load and battery charge current requirements. The microprocessor also performs housekeeping and display functions. Since the system requires only one power conversion stage, throughput efficiencies exceeding 90% have been achieved at the 3kW power level. Power densities also have been improved because of its "chargerless" construction. General principles of operation with phasor diagrams including actual system waveforms are presented as well as advantages and disadvantages of this approach with respect to conventional UPS equipment.

A Low Distortion PWM DC-AC Inverter, with Active Current and Voltage Control, Allowing Line-Interfaced and Stand-Alone Photovoltaic Applications

Abstract: The energy transfer between a photovoltaic solar panel and the grid can be realized by means of a DC-AC inverter, which is described in this paper. A reliability study of the entire system (i.e. the solar panels and the inverter) shows that the voltage generated by the solar panel matrix has to be low (≪ 100 V). The stability conditions of the energy transfer dictate a current source behaviour of the inverter. This is realized by means of an appropriate feedback system. In this way a voltage inverter type can be used instead of the current inverters which are usually proposed, so the relatively heavy and expensive inductors can be omitted. This also allows the inverter to be used as an AC voltage power supply, in the absence of the power grid.

A Photovoltaic Array Simulator

Abstract: A system simulating the output voltage-current characteristics of a photovoltaic array is described. The simulator may be used to test the performance of PV arrays and associated power conditioning equipment necessary for the autonomous or interconnected operation of photovoltaic energy sources. The simulator's main features include simplicity of construction, wide parametric variability and low cost. It is capable of reproducing the output characteristics of commercially available arrays at varying solar irradiation levels with sufficient accuracy. The design ensures the lowest possible power dissipation and minimal thermal drift. It is estimated that the cost of the simulator is an insignificant fraction of the actual array cost in the kilowatt power range.

Power Conditioning in Solar Photovoltaic Array Applications

Abstract: The design and implementation of appropriate power conditioning apparatus for the interconnected operation of PV arrays with the utility grid are presented. Problems of maximum power transfer from the PV array to the utility grid, reliability of the interconnected system operation and component protection are addressed. Because of the intermittent nature of the available solar energy, the need for conversion of dc electrical power to ac and the fluctuating loads of the utility system, optimization methodologies and associated equipment are developed for converting the maximum available solar power to electrical form and transfering it to the grid. A dual methodology is adopted containing a theoretical — system simulation — study of the performance of the interconnected system and a parallel experimental facility for the implementation of the system design. Results indicate higher energy transfer efficiencies in combination with an increased quality and reliability of performance of the PV array — utility grid system.

Regulated Converter Circuit for Direct Photovoltaic Energy Feedback into the Power Grid

Abstract: A new regulated utility interactive (UI) inverter for direct photovoltaic energy feedback to the mains has been realized. The inverter acts as a current source, its output is a sinewave with negligible harmonic distortion and has a projected efficiency of over 90%. A novel maximum power tracking (MPT) strategy based on a simple current peak error detection is described.

Improved power inverter

Abstract: An improvement is provided in a power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, which inverter includes first and second branches controlled by separate switching means to create the alternating current through the load. The improvement is the provision of a starting inverter having a D.C. input and an A.C. output with a frequency controlled by a series of repeating gating commands, means for selectively applying the A.C. output of the starting inverter across the load until a preselected load condition exist and an arrangement for controlling the frequency of the gating command in the starting inverter to produce a generally unity power factor across the load during the starting cycle. The improved inverter includes a circuit responsive to the voltage wave across the load for controlling the firing position of the gating signals. Also, a method of operating a power inverter including provision of a separate starting inverter having an alternating current output with a frequency controlled by repetitive gating commands, connecting the output of the starting inverter across the load, energizing the starting inverter, adjusting the frequency of the gating command to produce a substantially unity power factor across the load, maintaining the power factor for a starting cycle and then energizing the power inverter for normal operation.

Solar electricity-a low power technology

Abstract: The author examines the future potential of solar power with regard to its applications. He suggests that although the large size and small power output of solar cell electric systems are obstacles to high power usage, realistic low power applications can make a valuable contribution to world energy needs

Field Trial of Rural Solar Photovoltaic System

Abstract: A small standalone solar photovoltaic system using silicon solar cells has been set up in a village near Kalyani, India to meet two typical rural applications like a) village cominunity cum adult literacy centre, b) irrigation pimping. A television set of 65 watts and three fluorescent lamps of total 100 watts and a d.c pump set of about 300 watts are being used as load. Power conditioning units include high frequency dc-dc converter for TV set, dc-ac invertor for fluorescent lamps. Separate storage batteries have been used for the nighttime and daytime load. The performance of solar pump has been investigated for different options like with or without storage battery with a view to determine the cost effective option for stand-alone solar photovoltaic irrigation pump5.ng. The balance of system (BOS) costs of this system has been estimated and compared with that reported in the U.S.A. The electrical and thermal performances of the solar cell modules have been investigated. The social impact of this system in the village has also been studied. These observations lead to some interesting features of a typical SPS in rural conditions in India.