Showing papers on "Maximum power point tracking published in 1985"

Method of and system for controlling a photovoltaic power system

Abstract: In a method of and a system for controlling a photovoltaic power system including a solar battery and a power converter receiving the output of the solar battery, the voltage of the solar battery is kept at a voltage reference which is determined in accordance with the operating condition of the system thereby to maximize the power of the solar battery. Operating mode is switched between a first mode in which the voltage reference is periodically decreased and a second mode in which the voltage reference is periodically increased. The switching between the first and the second mode is effected in accordance with the direction of change of the power and the voltage of the solar battery. Where there is a reactance between the solar battery and the point at which the voltage or the current is detected, or a time lag element in a voltage detector or a current detector, an arrangement may be provided to compensate detection error due to the reactance or the time lag element.

A probabilistic mechanism for small disturbance instabilities in electric power systems

Abstract: Unstable, oscillatory behavior has been observed on several occasions in electrical power systems operated in an unfaulted, normal state under moderate load. In some cases system failure has resulted from this behavior. In this paper, we report on some recent results in the mathematics of stochastic processes which suggest a mechanism leading to small disturbance instabilities of this type in power systems. Unstable oscillations in power angles may be produced in a system consisting of a synchronous machine with negligible damping weakly coupled through randomly fluctuating links to other machines each with positive damping. The assumptions necessary to structure the model to produce this behavior are simple, flexible and consistent with possible operating conditions in an electrical power system.

Uninterruptible power supply with isolated bypass winding

Abstract: An uninterruptible power supply including a transformer having a first input winding normally coupling an inverter AC source with a critical AC load, which transformer also includes a second input winding operable to supply power from a bypass source to the load in the event of malfunction of the inverter circuit The inverter is of the four-quadrant pulse-width-modulated type, thereby to permit recharging of the battery which serves as the DC source to the inverter An inductance is provided for varying the phase relationship between a utility voltage source and the inverter voltage to produce minimum real inverter current and the "break-even" operating conduction, and a step-up device is provided for increasing the utility voltage to further minimize the break-even inverter current required during normal operation, and to maximize the through-put efficiency

Study of a resonant converter using power transistors in a 25KW x-rays tube power supply

Abstract: This paper describes a converter whose purpose is to feed an χ-rays tube (25 KW, 140 KV) from the industrial main power supply (380 V, 50 Hz). The authors justify the structure of this generator that is constituted by an inverter using power transistors and a transformer-voltage multiplier set which are connected by a series resonant circuit. The control logic of the transistors gives them the dual properties of these of thyristors. An accurate analytical study of this system allows to predetermine the characteristics of this converter now in its industrialization phase.

Frequency converting device and control method therefor

Abstract: A frequency converting device is provided with a converter for converting ac input power into dc power. The device includes an inverter for inverting an output (dc power) of the converter into an ac output power, and adjustment device for adjusting an output waveform of the inverter in accordance with the voltage values of the ac input power. The adjustment device comprises a memory which stores adjustment data corresponding to the voltage value of the ac input power source connected to the converter, and a selector for selecting a certain adjustment data from the memory in accordance with the voltage value of the ac input power to which the device is connected. Thus, even when the voltage of the ac input power is changed, the effective output of the inverter can be kept substantially constant by adjusting on/off times of the switching elements constituting the inverter to vary a duty factor of the inverter output.

Application of balanced realizations to power system equivalents

Abstract: An algorithm is presented to accurately estimate the feasible order reduction of dynamic models used in power system analysis. Order estimates obtained by balancing a linear model of the power system are used to determine the proper aggregation level of power system models derived from modal-coherency analysis. Test results for the 39 bus New England system are presented.

Control method for maximum power of battery power source

Abstract: PURPOSE: To stably obtain the maximum power also with a high accuracy by changing a variation width of a voltage reference which is given to a power converter, in accordance with whether a variation quantity of an output power of a battery power source, which has been generated by a variation of this voltage reference is large or small. CONSTITUTION: A maximum power control circuit 23 generates a voltage reference Vs*, based on a detecting value of a current detector 21 and a voltage detector 22 and supplies it to an inverter 11 being a power converter. In this case, the control circuit 23 varies the voltage reference Vs* by a prescribed variation width (ΔVs*) each, and detects an output power P of a solar battery 10 of that time. When a variation quantity ΔP of this detecting value is in an increase direction, a direction for varying the voltage reference Vs* is maintained as it is. On the contrary, when said variation quantity is in a decrease direction, the variation direction is inverted, and also a size of a variation width ΔVs* of the voltage reference Vs* is changed in accordance with whether the variation quantity ΔP is large or small. By executing a control in this way, the maximum power can be obtained stably and also with a high accuracy. COPYRIGHT: (C)1987,JPO&Japio

Power converter control apparatus and power converter control method

Abstract: A power converter control apparatus includes an automatic power controller (APC) for controlling a rectifier (1A) and an automatic reactive power controller (AQC) for controlling an inverter (1B). The inverter (1B) is coupled via DC power transmission lines (3) to the rectifier (1A). An output (E44) from the automatic power controller (APC) is utilized to change a control angle (or margin angle) of the inverter (1B) if a DC current (ld) flowing through the DC power transmission lines (3) increases to exceed a rated current value of the apparatus, thereby allowing a stable power transmission.

Stabilized electrical-power supply

Abstract: 1. Stabilized electrical power supply device, of the type comprising a static inverter (9) fed at normal rating by the electrical power distribution grid via a rectifier (2) and, in the event of failure of the grid, by a battery of accumulators (4) which is associated with a battery charger (5) connected to the grid, characterized in that it comprises in series, upstream of the inverter (9), a chopper-booster (8), the inverter and the chopper-booster being controlled by a regulating system (13) acting separately on the chopper-booster and the inverter, on the one hand to regulate the amplitude of the output direct current voltage of the chopper-booster which feeds the inverter with direct current voltage of substantially constant amplitude, in such a manner as to maintain the amplitude of the output alternating current voltage of the inverter substantially constant, and on the other hand to regulate the frequency of the inverter in such a manner as to maintain the frequency of the output alternating current voltage of the inverter substantially constant.

Design and construction of an advanced power conditioning subsystem for small photovoltaic applications

Abstract: The power inverter development described in this report is based on the technical approach development during a previous project funded by the US Department of Energy. That project was completed in mid-1981. During that investigation the high-frequency transformer-link power conditioning system was selected as the preferred approach. This approach appears to have the greatest potential for cost reduction when compared to other transformer-isolated designs because of its significant reduction of magnetic component size and weight. This report describes the details of a microcomputer-controlled 4 kW inverter design intended for residential applications. The theory of operation, detailed design, and some operational results are given. The inverter was designed to deliver utility quality power to the residential grid. Total harmonic current distortion of less than 5% and efficiencies around 90% were achieved. This report also gives reliability and cost analyses of the inverter and presents an equivalent circuit of the inverter useful for system analysis.

Solar photovoltaic generation control system

Abstract: PURPOSE: To stably and efficiently supply power irrespective of weather variation by setting weather pattern on the basis of weather information predicted on generating day, selecting the operating pattern of an inverter from the weather pattern to control the operation of the inverter. CONSTITUTION: A means of daily solar radiation is accumulated by the start of the operation of a system, and any one of weather patterns such as fine pattern, cloudy pattern and rainy pattern as a preset weather pattern. Since the upper and lower limit values of the power to be used are known by an inverter in response to the weather pattern, the number of inverters to be operated is decided. If the power supply based only on the output of a solar cell 1 is difficult, insufficient amount is supplemented by the power supply due to the discharge of a storage battery 8. After the amount of daily solar radiation is increased so that the output of the cell 1 exceeds the upper limit value of the power to be used by inverters 2, 3, 4, the excess output is charged in the battery 8. Therefore, power can be supplied stably and efficiently irrespective of the variation in the amount of daily solar radiation. COPYRIGHT: (C)1987,JPO&Japio

Electrolyte flow type battery system

Abstract: PURPOSE:To buffer short time variation of electric power generated by sun light and short time variation of load power by using together a lead-acid battery free from movable part such as pump when a battery having an electrolyte flow type electrolytic cell is used in power storage and/or voltage transformation of sun light power generation or wind power generation. CONSTITUTION:A system consists of power generating equipment 15 such as sun light power generating or wind power generating equipment, an electrolyte flow type battery 16, an inverter (a.c.-d.c. converter) 17, a lad 18, and a battery 19 such as lead-acid battery free from movable part such as pump. Carged power of both batteries detects the point A, and confirms it after retaining DELTAT, then the first set stack is started or stopped. Similarly, the point B is detected and the second set stack is started or stopped. Thereby, charge efficiency is increased as a whole.

System linkage inverter

Abstract: PROBLEM TO BE SOLVED: To make available a long-time operation with low output by suppressing ground current and noise during a low output operation, in the case that a multiple switching method is used. SOLUTION: This inverter is constituted of an inverter main circuit 2, having an inverter section 7 constituted of a plurality of switching elements and an inverter control circuit 3 which controls the inverter main circuit 2, by a multiple switching method. The inverter control circuit 3 conducts phase control on a sinusoidal waveform as a reference for a current command. When the output voltage of a DC power supply is smaller than a specified threshold value, a power factor is set to a value less than 1, proportional to the magnitude of the output power. In other cases, the power factor is maintained at 1, regardless of the magnitude of the output power.

Leasecraft Power System Leasecraft Power System

Abstract: Various building blocks of the Fairchild Leasecraft Power System are described in detail after a brief description of the evolution of the Leasecraft spacecraft. The principle of maximum power transfer from a solar cell array has been employed in the power system advantageously. Results of detailed tradeoff studies are presented which led to the selection of the decentralized regulation concept utilizing a nondissipative unregulated main (power) bus approach. Finally the main features of the Leasecraft Power System, i.e., flexibility, reliability, input and output electrical characteristics, etc. are presented.

Standby type no-break power source

Abstract: PURPOSE: To reduce the size of a power source and to save energy by utilizing an inverter for the removal of harmonic waves of a load current and for the charge of a storage battery during commercial power receiving to effectively use the inverter. CONSTITUTION: The harmonic wave components in a current of a load 17 are detected by a harmonic wave detector 23. A controller 22 of an inverter 15 is controlled by the detected harmonic wave component of the detector 23 during the receiving of commercial power. The inverter 15 is also used as a charger of a storage battery 14. Thus,the variations in the battery voltage and current of the battery 14 are detected by a battery variation detector 24, and the battery variation component and the detected component of the detector 13 are combined by a composite circuit 25. The combined output and the inverter variation component of an inverter variation detector 21 are switched by a switching circuit 26, and supplied to the controller 22. The circuit 26 is controlled by as a power interruption detector 19. COPYRIGHT: (C)1987,JPO&Japio

Dynamic simulation of dispersed, grid-connected photovoltaic power systems: system studies

Abstract: To investigate the operating characteristics and dynamic behavior of photovoltaic (PV) power systems, four PV system configurations were selected as representative of those currently being used in PV applications. These included single and three phase, line and self commutated power conditioners with a flat-plate PV array as the dc source. Detailed computer models of each of these systems were developed and incorporated into dynamic representations of typical primary and secondary distribution feeders. The dynamic electrical behavior of the PV and distribution systems following common network disturbances such as large load changes, PV system startup, and cloud cover transients are characterized. The dynamic behavior was also investigated during abnormal operating conditions following line faults, PV system malfunctions, and islanding of distribution systems containing significant levels of dispersed PV generation. Results of verification tests involving two of the single phase PV system configurations, in which the simulated response characteristics are compared with actual measurements, are also provided.

Power conditioning subsystems for photovoltaic central-station power plants - Technology and performance

Abstract: Central-Station (CS) Photovoltaic (PV) systems have the potential of economically displacing significant amounts of centrally generated electricity. However, the technical viability and, to some extent, the economic viability of central-station PV generation technology will depend upon the availability of large power conditioners that are efficient, safe, reliable, and economical. This paper is an overview of the technical and cost requirements that must be met to develop economically viable power conditioning subsystems (PCS) for central-station power plants. The paper also examines various already commercially available PCS hardware that may be suitable for use in today's central PV power stations.

Inverter design for high frequency power distribution

Abstract: A class of simple resonantly commutated inverters are investigated for use in a high power (100 KW - 1000 KW) high frequency (10 KHz - 20 KHz) AC power distribution system. The Mapham inverter is found to provide a unique combination of large thyristor turn-off angle and good utilization factor, much better than an alternate 'current-fed' inverter. The effects of loading the Mapham inverter entirely with rectifier loads are investigated by simulation and with an experimental 3 KW 20 KHz inverter. This inverter is found to be well suited to a power system with heavy rectifier loading.

Reverse voltage preventing method for system linkage inverter

Abstract: PURPOSE: To stop reverse electric power from an inverter to a commerical AC power source by detecting and comparing reactive power supplied by the inverter and reactive power which is consumed by a load with each other. CONSTITUTION: A device consists of a solar battery 1, the inverter 2, a system linkage reactor 4, the commercial power source 3, the load 5, a phase converter 6, converter transformers 7 and 13, an active power detector 8, a phase control circuit 10, reactive power detectors 9 and 14, a voltage control circuit 12, and an inverter driving circuit 11. The phase control circuit 10 inputs the output P of the detector 8 and sends a command to the inverter driving circuit 11 on the basis of the input value so that the output of the solar battery 1 is invariably maximum. The voltage control circuit 12 inputs the outputs Q and Q' of the detectors 9 and 14 and sends a command to the inverter driving circuit 11 so that Q does not exceeds Q'. A power failure of the commercial power source is detected from the certain-time continuation of Q≥Q' and the inverter 2 and commercial power source 3 are paralleled off in this case. COPYRIGHT: (C)1987,JPO&Japio

Uninterruptible Power Supply System (UPS) with PWM Inverter and Microprocessor Controlled Measuring Equipment

Abstract: This paper describes a single phase static UPS (uninterruptible power supply system) comprising of an inverter which uses high current transistors for a power range which was reserved to thyristors up to now. A microprocessor controlled measuring system calculates all data of interest such as input and output power, efficiency etc. The basic theory of the PWM inverter and the microprocessor unit is handled in detail.

On the automatic interconnection between solar cells and inverter

Abstract: A novel system including many solar cells and a secondary battery is presented. These energy sources are connected to each other with a bus bar through inverters and supply ac power to loads on the bus bar. The output voltage of the solar cell is always kept constant in order to derive the almost maximum output power from the solar cell when the light strength from the sun is varied. When multiple-loads in different places should be supplied, the solar cells can be distributed near by the respective load in order to remove transmission loss of the bus bar.