Showing papers on "Power optimizer published in 1994"

A new maximum power point tracker of photovoltaic arrays using fuzzy controller

Abstract: Studies on photovoltaic systems are increasing because of a large, secure, essentially exhaustible and broadly available resource as a future energy supply. However, the output power induced in the photovoltaic modules is influenced by an intensity of solar cell radiation, temperature of the solar cells and so on. Therefore, to maximize the efficiency of the renewable energy system, it is necessary to track the maximum power point of the input source. In this paper, a new maximum power point tracker (MPPT) using fuzzy set theory is proposed to improve energy conversion efficiency. A fuzzy algorithm based on linguistic rules describing the operator's control strategy is applied to control the step-up converter for the MPPT. Fuzzy logic control based on coarse and fine mode has been incorporated in order to reduce not only the time required to track the maximum power point but also the fluctuation of power. The MPPT algorithm is implemented by a 16 bit single chip 80C196KB microcontroller. Simulation and experimental results show that performance of the fuzzy controller in a maximum power tracking of a photovoltaic array is better than that of controller based upon the hill climbing method. >

Maximum power point tracking for low power photovoltaic solar panels

Abstract: A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper). The system consists of three main units: (i) the photovoltaic panels that convert solar power to electricity; (ii) a chopper which couples the power of PVP to the load or batteries at a constant voltage; and (iii) maximum power point (MPP) computing unit that determines the set point of the chopper to keep the panel voltage at a maximum power transfer (MPT) condition. The tracking of the MPP for low power PVP (50 W-1 kW) is feasible only when the power consumption of the tracking unit is lower than the increase of the output power that they provide. The developed and tested circuit consumes only 40 mW, and therefore is suitable even for low power applications down to 50 W. The tracking unit performs MPP computation periodically through analog computing stages. The computation mode requires 20 mA from the /spl plusmn/5 V source for a 50 ms period. In the control and sleep mode, the consumption falls down to 4 mA. The developed unit regulates the panel output voltage at its optimum value in the control mode. The modes are switched by a timing circuit. The sleep mode is initiated when maximum PVP output power of the existent illumination level drops to a preset value, which cannot balance the losses of the chopper and the consumption of the MPP tracker unit. >

Maximum power point tracker using fuzzy control for photovoltaic arrays

Abstract: The solar cell has an optimum operating point to be able to get the maximum power. To obtain the maximum power from a photovoltaic array, the photovoltaic power system usually requires a maximum power point tracking controller. This paper proposes a maximum power point tracking control of photovoltaic array using fuzzy control; the controller only uses the output power. Therefore, this control method is easy to implement to a real system. Moreover, this method can track maximum power point rapidly with fuzzy inference even if the optimum operating point changes. The usefulness of this control method is confirmed by experiments using step-down chopper with constant resistive rod. >

A utility interactive wind energy conversion scheme with an asynchronous DC link using a supplementary control loop

Abstract: The paper presents modelling, simulation and experimental verification of a utility interactive wind energy conversion scheme with an asynchronous link comprised of a diode bridge rectifier and a line commutated inverter. The control objective is to track and extract maximum power from the wind energy system and transfer this power to the electric utility. This is achieved by controlling the firing delay angle of the inverter. Since the diode bridge rectifier has no control on the DC link voltage, a supplementary control loop is used to limit the voltage within a preset voltage threshold. The proposed scheme for regulating the flow of power through the DC link ensures reduced reactive power burden on the self-excitation capacitor banks and better utilisation of available wind energy, while limiting the DC link voltage within a preset voltage threshold. The simulated results are experimentally verified and found to give good power tracking performance. >

Congeneration power system

Abstract: A secondary power system eliminates the need for an automatic transfer switch and permits simultaneous supply from different sources. Primary power is rectified and connected to a DC bus, an AC generator has its output rectified and connected to the DC bus, and a storage battery is also connected to the DC bus. Current on the DC bus is inverted to AC to provide an uninterrupted power supply. The system is connected to a household electrical system by a power distribution panel which can be installed in a home prior to the secondary power system and can facilitate installation of the secondary system. The distribution panel can selectively bypass the secondary system and can disconnect non-vital loads when primary power is not available. The generator is powered by an engine using gasoline, natural gas or water, which can also power other systems, such as air conditioning, with exhaust heat or rotary motion.

Control of an optimized converter for modular solar power generation

Abstract: Important drawbacks of solar power generation are the DC-wiring and fusing needed for the serial and parallel connection of solar panels. These problems can be reduced to AC wiring and fusing by using a modular set up of panels together with integrated single phase DC-AC power converters on a power level of approximately 200 W. A general applicable model has been developed for the coupling of two single-phase systems by a voltage link with small storage capacitance. It allows the decoupling of the pulsating mains power from the panel. Based on this model, which avoids the need of large filters, a sophisticated control principle has been developed. The result is a power converter which allows the operation in the maximum power point without any power pulsation In the solar panel. The required reactive elements, and therefore the size of the power converter, are very small. >

Development of a new utility-connected photovoltaic inverter LINE BACK

Abstract: A new utility-connected photovoltaic inverter called "LINE BACK", which is suited to small-scale photovoltaic generation systems for use in private households, has been developed. The inverter converts DC power generated by rooftop photovoltaic cells into AC power, and provides it to house loads connected to the utility line. When photovoltaic power is greater than the loads, the excess power is fed to the utility line through a reverse power flow. The inverter has several special functions such as a utility protection relay, maximum power point tracking (MPPT) control, automatic operation with photovoltaic power, detection of islanding operation, and utility voltage compensation for reverse power flow. These functions and characteristics conform to the "Utility-Connected System Technical Guidelines" revised by Japan's Ministry of International Trade and Industry in March 1993. >

Simplified power system with a single power converter providing low power consumption and a soft on/off feature

Abstract: A computer power system with a keyboard, a computer housing, and a single AC to DC power converter that generates a DC power signal as long as it is energized by an AC power source. The power system is digitally controllable by the central processing unit (CPU) or from soft on/off switches on the keyboard and computer housing. This is made possible by a soft on/off controller that receives soft on/off control signals from the CPU and the soft on/off switches and in response generates a power transition signal that triggers shaping circuits to connect (soft on) or disconnect (soft off) power system output lines and power lines from the converter. The shaping circuits also ensure that the rising edge of a digitally switched power system output signal resembles the rising edge of the converter's cold-start power signal. Following a soft off event,, the power system is in a low power standby state as power is not being supplied to the computer's power hungry components even though the converter is still generating a power signal.

A photovoltaic maximum power tracking using neural networks

Abstract: The paper presents laboratory implementation of a photovoltaic artificial neural network (ANN) based maximum power tracking controller. The control objective is to track the maximum available solar power in a photovoltaic array interfaced to an electric utility grid via a line-commutated inverter. The inverse dynamic characteristics of this interface scheme is identified via off-line training using a multi-layer perceptron type neural network. The ANN output is used as the control signal to vary the line-commutated inverter firing control angle, hence track the available maximum solar power. The weights of the ANN are also updated by a novel on-line training algorithm which utilizes the on-line power mismatch error. This ensures on-line maximum solar power tracking. The proposed controller is compared with a well tuned conventional proportional plus integral controller to validate its effectiveness. >

Backup power-supply system for emergency

Abstract: The present invention discloses a backup power-supply system for emergency that may apply power to a data processing system and recover the information in it when the power supply is cut off or a power-supply connector is abruptly removed due to a careless user, so as to prevent the damage to the information the user is working on. When the power is applied to the system, a battery is charged with the direct current power applied from a linear conversion rectifier by a battery charger, and when the power is not applied to the system while a power switch is being turned on, a DC/DC converter is operated by a power controller to apply the DC power charged in the battery to the main power-supply system after the direct current has been converted into DC/DC power in such a manner that the main power-supply means applies to the system the power for recovering the information a user was working on in the system.

Study of an optimized resonant converter for high-voltage applications

Abstract: This paper presents the study of a high-voltage DC-to-DC resonant power converter which has excellent behaviour for use in applications with strong variations in the output voltage and in the output current, because it maintains high efficiency in these types of applications. To do so, the switching losses have been minimized by integrating all parasitic elements (leakage inductance, secondary side capacitance of the high-voltage transformer and parasitic capacitances of the power switches and diodes) into the power topology, and the conduction losses have been minimized by operating the converter in a special mode (optimum switching line) in which no reactive energy is returned from the resonant elements to the input voltage source. The type of control used (PWM phase-shifted) allows one to maintain these desirable characteristics even when the operating point suffers a very strong variation, The final power topology might be called a "full-bridge, clamped mode, LCC-type parallel resonant power converter with capacitive output filter".

Buck converter having a variable output and method for buck converting power with a variable output

Abstract: A power supply for providing an ac/dc output to a load, includes a first source of dc power and an inverter that provides an ac output to the load. A second source of dc power is provided and selectably connects the first and second sources of dc power in series with the load when the output current reverses. In one embodiment the power sources are connected in series with every output current reversal. The first source of dc power is controllable and the magnitude of the dc current is responsive to a current reference signal. A control circuit provides the current reference signal, wherein the current reference signal is pulsed immediately prior to the ac output reversing polarity. The first source of dc power source preferably includes a buck converter that is switched at a variable frequency, depending upon the desired output current. In the event the user selects either an ac or dc electrode negative output a period of electrode positive dc energy is provided at start up to help establish the arc.

Applying distributed power modules in telecom systems

Abstract: The design of modern decentralized power systems in telecommunication applications are increasingly realized by using distributed DC/DC power modules. Power modules are usually characterized by high switching frequencies which enables the use of small ferrite magnetics and ceramic capacitors to enhance the reliability, the power density and the possibility of live insertion, all desired features in new power system designs. However, to utilize the advantages of power modules there are a number of considerations to be made in the design. These considerations are addressed focusing on telecom systems with an average power dissipation of >

Integrated uninterruptible DC converter with low input distortion and wide regulation capability

Abstract: This paper presents a novel integrated uninterruptible AC/DC power converter which operates at unity power factor. With the inherent high frequency triport configuration, it delivers uninterrupted DC power to the load through two independent power sources of commercial input power and battery power. The circuit operation and theoretical analysis, together with the experimental results from a prototype for verification of the theory, are presented.

Maximum Power Point Tracking Control of Photovoltaic Array Using Fuzzy Control

Abstract: The solar cell has an optimum operating point to be able to get maximum power. To obtain maximum power from photovoltaic array, photovoltaic power system usually requires maximum power point tracking control ler. The output characteristics of solar cell are nonlinear, and these characteristics vary with load, solar insolation, cell temperature. Therefore, the tracking control of maximum power point is the complicated problem. This paper proposes the maximum power point tracking control of photovoltaic array using fuzzy control. To obtain maximum power from photovoltaic array, the fuzzy controller only uses the output power. Therefore this control method is easy to implement to real system. Moreover, this method can track maximum power point rapidly with fuzzy inference even if the optimum operating point changes. The usefulness and validity of proposed control method are proved experimentally under constant natural solar insolation.

Simulation of DC power distribution systems

Abstract: Direct current (DC) power distribution systems have been extensively used in nuclear power plants and transit systems. The major concern of DC system studies is the voltage and voltage drop at load buses. A Newton-Raphson method based DC load flow algorithm and a DC system simulation package have been developed and reported in this paper. DC generators, batteries, AC/DC rectifier converters and constant power, constant current, constant resistance loads can be considered in the simulation. Time-varying and moving loads can also be simulated. >

Method and device for maximum output following control for photovoltaic power generation system

Abstract: PURPOSE: To stably perform the following control of an inverter by reducing the delay of peak point detection concerning the maximum output following control method for photovoltaic power generation system for controlling the inverter so as to maximize the output power of a solar battery. CONSTITUTION: A peak power curve 10 is prepared by connecting the maximum output points of the power generating characteristic curve of the solar battery with sunshine and temperature as parameters, and the maximum output point of the solar battery is retrieved by changing the DC voltage set value of the inverter along the peak power curve 10. Since the change width of a DC voltage at a peak point is narrow, even when the DC voltage of the inverter is changed near this curve 10, a control system is not made instable. Further, since the retrieval width of the peak point is narrow, the delay of peak point detection is reduced. COPYRIGHT: (C)1996,JPO

Power supply with the main inventive concept of periodically drawing power from a DC source

Abstract: A power supply periodically draws power from a DC soure. The power supply includes an electroluminescent lamp and an inverter used to convert the DC into a sinusoidal voltage that is applied to the lamp.

Power failure landing device for elevator control device

Abstract: PURPOSE:To make a rescue running in regeneration easily and inexpensively by igniting the elements of an inverter device so as to make the DC control of an electric motor for regenerative operation if a DC voltage exceeds a set voltage in a regenerative running during a rescue running at power failure. CONSTITUTION:In normal running, a three-phase AC power 1 is controlled in a constant DC voltage by a converter device 2 and, in power running, the energy of the three-phase AC power 1 is supplied to an electric motor 7 through an inverter 6. Also, in regenerative running, the regenerative energy of the electric motor 7 is returned to the three-phase AC power 1. On the other hand, in power failure, a DC contactor 9 is closed and, in power running, the energy of a battery 8 is supplied to the electric motor 7 for rescue running. In this case, the outputs from a DC voltage detector 14, and DC control start and stop voltage setting devices 16 and 17 are input into comparators 15, respectively, and a DC control command is output. Then, when a command is output, the elements Q1 to Q6 of an inverter device 6 are ignited simultaneously by a phase controller 20.

A review of single phase power factor correction circuits for telecommunication applications

Abstract: This paper presents a comparative performance of resonant, soft-switched and hard-switched single phase power factor corrected rectifier circuits for telecommunication power supply applications. Three practical rectifiers employing a boost pre-regulator and a resonant, soft-switched and hard-switched DC/DC power converter topologies respectively are built in the laboratory for the same set of requirements. It is shown that the resonant rectifier has higher efficiency than other two rectifiers. All the three rectifiers with forced air cooling are found to have the same size. >

Minimisation of reactive component values in back-to-back converters

Abstract: The back-to-back AC-AC power converter, consisting of two PWM inverter bridges with a common DC link, is considered as a future replacement for the conventional inverter drive. The topology offers the advantages of high power factor and regenerative capability. The factors determining the size of the reactive components are discussed. Guidelines for selecting components are derived from consideration of the required DC link voltage, the input current quality, the stability of the DC link voltage control loop, and the transient response of the system. Simulation shows the feasibility of implementing a 7.5 kW converter with a DC link capacitance of 50 mu F. This result suggests that it may be possible to use nonelectrolytic capacitors in the DC link.

Load Sharing in High-Reliability AC-DC and DC-DC Converter Power Systems

Abstract: The high reliability of power systems utilizing paralleled rectifiers or converters is based on redundancy of individual modules. This paper traces the origines of the load-sharing approach to airborne electromechanical power systems and highlights the fundamental features of today's state-of-the-art approaches. The emphasis is on the over-all performance, reliability and user-friendliness.

Enhanced traction system for trolleybuses, powered from a 600-volt direct current power line

Abstract: An electrical system that receives power from an external power source that includes an inverter (U1) The inverter (U1) receives DC power and generates a variable voltage output First and second current collectors (30, 32) connected to the inverter (U1) and receive the DC input through contact with positive and negative poles of the external power source A motor (M1) and an internal DC bus (+,-) are connected to the current collectors (30,32) A protection circuit is connected across the internal DC bus (+,-), and protects the inverter (U1) from connection to an input of improper polarity The protection circuit permits the inverter (U1) to deliver a DC output to the power source during a regenerative braking operation

Design of a controller for a test-rig for a variable speed wind turbine

Abstract: One of the most promising of the sources of renewable energy for the UK is wind power. Over the last ten years there has been considerable development in the associated technology and the cost of power generated by wind turbines has been reduced markedly. Nevertheless, further progress is required for wind power to become fully competitive on a commercial basis. The Dutch Department of Energy is funding a research programme, FLEXHAT, with the stated aim of reducing the cost of wind power by 30%. It is envisaged that the reduction in cost might be achieved by a flexible variable speed horizontal axis wind turbine. The drive-trains of light-weight flexible variable speed wind turbines are highly resonant. ECN in Holland have constructed a test-rig, IRFLET, to investigate the problems arising from the resonant drive-train. The test-rig has a resonance at 3 Hz approximately with a damping factor less than 0.005. To maintain a variable speed wind turbine at the correct operating point for most effective operation, it is necessary to actively control the wind turbine through the generator reaction torque. It might also be feasible to utilise the control system to regulate the resonance. The purpose of this paper is to report the design and test of a controller to achieve this aim. >

Cross-regulation in two related multi-output resonant DC to DC converters

Abstract: Two resonant, zero voltage switching (ZVS), zero current switching (ZCS), DC to DC power converter topologies were investigated and compared for use in multi-output low-voltage power supplies for space applications. The topologies appear quite similar, except that the tuning components are on the primary side of the transformer in one case, and on the secondary side in the other. This makes a large difference to the performance, particularly the cross-regulation. Experimental results are included.

Wind power and solar power installations - can have different shapes and sizes, e.g. drum-shape, cylindrical-shape, or globe-shape

Abstract: The solar power equipment can have different shapes and sizes. The solar equipment can be round, spherical, cylindrical, flat, curved, cube shaped, edged, angular, mirror type or even other types. Similarly, the wind power equipment can have different shapes and sizes, e.g. star or half-shell. The wind power generator can be constructed with wings and silicon thin-film solar cells. Waffle-type designs can be used on the rotor blades to increase their efficiency. USE/ADVANTAGE - Wind and solar power generation. Solar cells for mounting on trains, ships or airplanes. Can be swivelled or installed slanting, vertical or even horizontal to provide increased power wrt current wind or solar power installations.

Bicycle using wind power

Abstract: A bicycle using wind power and comprising a wind turbine (1) located above the front wheel (13) and supported at each end of its shaft (2) by frame extensions (21, 22). The rotational shaft (2) is coupled to the crankset (3) via a corner gear (4) and a drive chain (5). As the bicycle moves along, the wind rushes into the blades (1) which rotate and transmit power to the crankset (3) to supplement the rider's pedalling power, thereby substantially improving the performance of the bicycle. As the strength of the wind increases along with the speed of the bicycle, a number of chain wheels (3) located under the drive chain (5) provide a variety of torque ratios enabling the output of the wind power system to be adjusted and optimised. The unique positioning of the wind turbine and the special configuration of the frame also eliminate most of the points where wind is caught but cannot be used. The wind power used by the above-mentioned device may also be converted into electric power.

Automatic Interconnecting System for Photovoltaics and Utiliy Line

Abstract: This paper will describe a new interconnecting system for numerous photovoltaics and utility line. In this system, each of dc-dc converters derives the maximun power from each of photovoltaics for any daylight strength. Outputs of converters are connected to dc bus line. The inverter sends power from dc bus line to the utility line. The inverter are automatically synchronized to the utility line by means of phase locked loop. A power factor controller combined with the phase locked loop makes power factor unity by changing the output voltage of the inverter corresponding to total output power of photovoltaics.