Showing papers on "Maximum power point tracking published in 1993"

A high-efficiency maximum power point tracker for photovoltaic arrays in a solar-powered race vehicle

Abstract: A maximum power point tracker for photovoltaic arrays is presented. Components are optimized for weight/power-loss tradeoff in a solar-powered vehicle, resulting in over 97% efficiency. The control circuit uses a robust auto-oscillation method. Measurement and multiplication of array voltage and current is shown to be unnecessary, and the control is based only on output current measurement. Multiple local maxima arising from partial shading of the solar array are discussed. >

A general battery model for PV system simulation

Abstract: A battery model is proposed as a tool to simulate and optimize photovoltaic (PV) / storage systems. the normalized form of the equations with respect to the battery capacity allows us to generalize its use for any type and size of lead-acid batteries. The validity of this model to represent the battery voltage evolution during charge, overcharge and discharge processes and to predict the performance of solar systems under different operational conditions is analysed. Moreover, the battery efficiency losses are presented as a function of the upper regulation thresholds of the charge controllers and the size of the array and storage systems in a domestic application in the climate of Madrid.

A new maximum power point tracking system

Abstract: In power systems involving a load, a battery and a solar array, MPPT (maximum power point tracking) is a promising principle to extract the maximum amount of energy from the solar array and distribute it to the battery and loads. A digital hill-climbing control strategy combined with a bidirectional current mode power cell is presented that makes it possible to get a regulated bus voltage topology, suitable for space applications, by means of two converters. Theory, simulation, and breadboard validation are successively detailed. >

Low cost DC to AC converter for photovoltaic power conversion in residential applications

Abstract: The development and experimental results of a low-cost 500-W DC-AC power converter for photovoltaic power conversion in residential applications are described. The converter uses low-cost technology usually applied in consumer products. The DC-AC converter is specially designed for operation at a wide DC input voltage range (30-170 V) in order to allow optimal power conversion with an arbitrary number of series connected solar arrays. A step-up chopper is used for MPP tracking and provides a constant 200-V DC link for the following push-pull power converter. This galvanic isolating power converter operates at 100 kHz and controls the current in the mains sinusoidally. A thyristor bridge alternates the current after each half line period. The required auxiliary power is kept below 7 W and is taken from the choke of the step-up chopper. >

Battery operated computer having improved battery gauge and system for measuring battery charge

Abstract: A digitizer tablet computer has a host processor connected to a service processor which, in turn, is connected to a digitizer controller and to a power subsystem microcontroller. A battery supplies the primary power for operating the computer but the computer is also connectable to an external source of DC power to charge the battery and to operate the computer when it is not running on battery power. The service processor includes a battery gauge the contents of which indicate how much power is left in the battery and how much time remains at the current rate of power consumption before the power runs out. The amount of remaining power in the gauge is determined by keeping track of power consumed, power added, and power lost during off periods. The use of the second derivative of a voltage versus time discharge curve creates a point from which relative accurate estimates can be made of how much longer the computer can be operated.

Starting characteristics of direct current motors powered by solar cells

Abstract: The authors deal with the calculation of the starting to rated current ratio and starting to rated torque ratio of the permanent magnet, separately, series and shunt excited motors when powered by solar cells for the two cases where the system includes a maximum-power-point-tracker (MPPT), and without an MPPT. Comparing these two cases, one gets a torque magnification of about three for the permanent magnet motor and about seven for other motor types at rated design insolation. The calculation of the torques may assist the photovoltaic system designer to determine the advantage of including an MPPT in the system as far as the starting characteristics of the DC motors are concerned. >

Power converter with controller for switching between primary and battery power sources

Abstract: A power converter, based on a modular architecture, in which a boost power factor correction circuits is provided as an input stage for both a primary power source and a battery power source. This arrangement permits the same power conversion stages which follow the boost power factor correction circuit to be used regardless of whether the primary or battery power source is in use. The power supply includes a controller for monitoring the primary power source voltage and the DC voltage produced at the output of the boost circuit and comparing each to a preselected reference. When a sufficiently large difference appears between each of those voltages and its respective reference, the controller connects the battery power source to the input of the boost circuit and simultaneously disconnects the primary power source therefrom. This switching of power sources is transparent to the load whose input voltage is maintained at a substantially constant level by the boost power factor correction circuit.

Photovoltaic power generating equipment capable of jointly using battery

Abstract: PURPOSE:To make the power generation capacity of a solar battery maximum, and to effectively utilize solar radiation energy by operating a DC/DC converter and controlling the output voltage of the solar battery so that the generated power of the solar battery becomes maximum. CONSTITUTION:At the time of supplying electric power from a solar battery 1 to an inverter 3, a DC/DC converter 5 controls an output voltage of the solar battery 1 so that the generated electric power of the solar battery 1 becomes maximum. When the generatable maximum electric power PPVL of the solar battery 1 is smaller than the consumption electric power PINV of the inverter 3, insufficient electric power obtained by subtracting the generated electric power PPVI of the solar battery from the consumption electric power PINV of the inverter 3 is supplied by electric power supply caused by discharge of a battery 4. On the other hand, when the generatable maximum electric power PPVI of the solar battery 1 is larger than the consumption electric power PINV of the inverter 3, surplus electric power obtained by subtracting the consumption electric power PINV of the inverter 3 from the generated electric power PPVI of the solar battery 1 is used for the charging of the battery 4.

A new single phase buck-boost converter with unity power factor

Abstract: A novel cascade buck-boost power convertor topology that offers a high degree of power factor correction is proposed Low-frequency harmonic elimination in the input current is achieved and the power factor is improved to over 99% at power levels of 500 W in typical applications using very simple control circuitry The buck mode has the same performance as the boost mode A broad range of output voltage and output power is obtained with unity power factor The analysis performed and the design equations presented should enable the design to be adapted to a wide range of output power The effect of the cascade buck-boost inductance and current ripple on the size and efficiency of the converter power stage was taken into consideration Due to the source impedance and the EMI (electromagnetic interference) filter, the generated high-frequency harmonics do not affect communication systems >

Economical, PV maximum power point tracking regulator with simplistic controller

Abstract: A 30% cost reduction of photovoltaic generation can be brought about by the investment in a novel, highly efficient maximum power point tracker (MPPT). Such a power converter is currently under development, implementing a feedforward output current controller as tracking algorithm. The DC-DC power converter, typical of a MPPT, exploits the efficient high-frequency operation, associated with zero-transition switching. Thus the output filter only consists of the combination of a storage battery and its cabling. The resulting power converter is suitable for integration into standard PV panels during manufacturing. The efficiency of the MPPT is 96% for a range of output powers at a low battery voltage of 12.5 V and a component cost of US$21.00. >

High power factor AC-DC converter with reactive shunt regulation

Abstract: A high power factor AC to DC converter with shunt regulation include first and second power converters for converting AC power to DC power; the first power converter receives and regulates input power from a power source and delivers a component of an output power to a load. The second power converter delivers another component of the output power to the load. The first power converter includes a unidirectional power output connected to the load. The second power converter includes a bi-directional power input shunted across the load with a bi-directional power output connected to an energy storage apparatus for storing a difference between the input power and the output power components

Multi-function electric power conversion system

Abstract: The bus line of an electric power system is connected to an inverter which can be placed in a forward operation mode or in a reverse operation mode, and batteries are connected to the inverter to store the dc energy thereof. When a commercial power source is normal, an ac switch is closed, so that the inverter is placed in the forward operation mode to perform an active filter operation for eliminating harmonic current and reactive current. When necessary, the batteries are charged, and the inverter is placed in the reverse operation mode to perform a peak cut power generation. At loss of the commercial power source or momentary drop of the supply voltage, the switch is opened so that the inverter is placed in the reverse operation mode to perform an UPS operation (emergency power generation). Hence, electric power is supplied without interruption to an important load and the emergency load.

Protection device for stopping operation of an inverter

Abstract: A protection device for an inverter which is connected to an AC power system, converts DC power into AC power, supplies the AC power to a load and includes a control circuit for detecting a phase and a frequency of an output voltage, for generating a current reference synchronized with the output voltage and for controlling the inverter such that an output current is coincident with the current reference. The protection device includes a first detection circuit for detecting that an AC output is disconnected from the AC power system based on an electrical quantity of the output voltage and for generating a detection signal based on a detection result, and a correction circuit connected to receive the detection signal for generating a correction signal to break a power balance between an output power and a power consumed by the load. The control circuit corrects the current reference by the correction signal and controls the inverter based on the current reference thus corrected thereby to break the power balance. The protection device also includes a second detection circuit for detecting that the power balance is broken and for generating an abnormality signal to stop operation of the inverter based on a detection result.

Simplified maximum power point controller for PV installations

Abstract: A new low-cost, simplified control strategy, based on the positive feedback of the output current in a maximum power point tracking (MPPT) converter, is introduced. Cost effective MPPT reduces the energy cost of renewable energy generators by optimizing the utilization of the renewable energy source. Maximum power point tracking for relative small photovoltaic (PV) power systems, with battery back-up, is achieved by employing this simplified positive feedback control strategy to maximize the output current into the battery. This new control strategy is analyzed and practical tested by using a buck power converter topology, but can also be used by the known converter topologies for PV systems and other renewable energy sources with a single power maximum. Experimental verification on the operation of this controller is included. >

Intelligent power supply

Abstract: An intelligent power supply is disclosed for use with a computer system having an external keyboard connected to the computer system by means of a keyboard input connector. The power supply includes a primary power supply and a power controller for controlling and monitoring operation of the primary power supply. The power supply further includes a connection interface for connecting the power controller between the keyboard and the keyboard input connector of the computer such that normal data transmission between the keyboard and the computer system is not affected and such that control signals may be transmitted from the keyboard to the power controller. The power controller is responsible to those control signals from the keyboard to control the operation of the primary power supply. The power controller may be separately powered by a secondary power supply.

Control method of parallel operation of inverter for system interconnection

Abstract: PURPOSE:To maintain the proper value of power conversion efficiency as the whole inverter system for system interconnection consisting of a plurality of inverters and a DC power supply such as a solar cell respectively. CONSTITUTION:When the sum of the output power of both inverters 2A and 2B detected by an output voltage detector 6 is smaller than a set value thereof, an electromagnetic 3C for varying interconnection among both inverters and both solar cells 1A, 1B is closed, and either one inverter selected in both inverters is supplied with electricity from both solar cells. When the sum of both output power is larger than the set value thereof, the electromagnetic switch 3C is opened. Accordingly, the inverters are operated in both combination of the inverter 2A and the solar cell 1A and the inverter 2B and the solar cell 1B, and the operation of the inverters is controlled in conformity with a specified program in a switching control circuit 7 so as to maintain the proper value of the power conversion efficiency of the inverters by the increase of the load factor of the inverters regarding the inverters selected to be worked.

Analysis of a new compound converter as MPPT, battery regulator and bus regulator for satellite power systems

Abstract: A new compound energy converter for low earth orbit satellites is proposed, using the parallel power conversion technique, a new maximum power point tracking technique based on positive feedback, and the peak current-programmed control technique. These techniques are used for low EMI (electromagnetic interference), high power conversion efficiency, high reliability, stability and size reduction. >

System interconnection type inverter controller

Abstract: PURPOSE:To always take out a maximum power from a DC power source by satisfactorily performing the maximum power point tracking control regardless of the variance in voltage-current characteristic of the DC power source like a solar battery. CONSTITUTION:A CPU 48 outputs the waveform pattern read out from a ROM 49 to a D/A converter 51 to obtain a reference sine wave signal S11 and switches an FET bridge 36 through a PWM modulation circuit 43 and a gate drive circuit 42 to convert the DC power from a solar battery 32 to an AC power. A detected inverter output current IOUT is converted to a digital value by an A/D converter 47 and stored in a RAM 50. The CPU 48 compares the preceding output current value and the present, output current value with each other to discriminate whether the output current IOUT is increased or not. The amplitude changing direction of the reference sine wave signal S11 is kept if it is increased, but this direction is inverted if it is reduced, and the amplitude of the reference sine wave signal S11 is changed in the determined direction by one stage to perform the maximum power point tracking control of the solar battery 32.

Dual power refrigerator

Abstract: A rotary-compressor control system for electric refrigerators using rotary compressors for cooling the inside of the refrigerators, in which a battery for feeding direct-current power, an inverter power section for converting direct-current (d-c) power from the battery into a low-voltage three-phase alternating-current (a-c) voltage, a low-voltage three-phase induction motor for driving the rotary compressor with the low-voltage three-phase a-c power obtained in the inverter power section, and a control circuit for controlling the inverter power section on the basis of a control command signal given from the outside, so that the rotary compressor is driven by the three-phase induction motor that operates with a low voltage of the order of battery voltage

Fuzzy logic controller for maximum power tracking in line-commutated photovoltaic inverter scheme

Abstract: The paper presents simulation and implementation of a photovoltaic fuzzy logic tracking controller. The purpose is to track the maximum available solar power in a photovoltaic array interfaced to an electric utility grid via a line-commutated inverter. The scheme shows a satisfactory performance with almost an agreement between the simulation and experimental results. >

Parallel inverter system

Abstract: In a parallel inverter system such as for an uninterruptible power supply, output voltages of the inverters 2, 3 are compared at 25, 26 and a current control loop (11, 13, 17, 21,23; 12, 14, 18, 22, 24) responds to the magnitude of an output current of each inverter such as to change a command value for a voltage waveform control circuit 23; 24 associated with each inverter, and the gain of the current control loop is made to be variable, whereby currents shared by the inverters can be set to effectively suppress a cross current flowing between the inverters upon establishment of parallel running. In a further embodiment (Figs 6, 24) the output currents of the inverters are also compared to provide additional control. In an alternative embodiment (Figs 13, 14) the output voltage of one inverter may be compared with the average output voltage to the load. In a still further embodiment (Figs 15, 20, 21) the output currents of the inverters are compared instead of the output voltages. Further (Fig 26) the output currents of the inverters may be compared to the average output current.

Power converter and controlling method

Abstract: PURPOSE: To obtain a power converter and a method for controlling in which a charged state of a battery for supplying a DC to an inverter to be regenera tively operated is controlled. CONSTITUTION: A battery 4 is connected to a DC circuit for connecting a converter 1 to an inverter 2, and at the time of operating the inverter 2, the battery is discharged to the inverter 2 until a voltage detected value 5 of the battery becomes a set value (a voltage lower limit value) of a voltage instruction unit 6. In order to control a discharging current of the battery 4, the discharging current is detected by a detector 8, its value is inputted to a current regulator 9 of the converter 1, and a current of the converter 1 is controlled. Thus, since a battery voltage is held at a preset lower limit value, regenerative power can be absorbed to the battery to a maximum limit. A regenerative inverter is eliminated to simplify its configuration. COPYRIGHT: (C)1994,JPO&Japio

Application of neural network to prediction of maximum power from PV modules

Abstract: This paper presents an application of a neural network to the prediction of maximum power drawn from PV modules. The output power from the modules depends on the environmental factors such as insolation, cell temperature, and so on, therefore, accurate estimation of maximum power and continuous control are required to achieve maximum output efficiency. The proposed neural network has a simple structure resulting in highly accurate prediction of maximum power from the PV modules. >

1.2 MW DC-DC converter

Abstract: A DC-DC power converter has been developed to charge power capacitors to 16 kV from a 400 V battery bank. It is designed to charge an 8.5 MJ bank nine times in 3 min. The converter is composed of six modules, each producing 12.5 A of charging current, and an enclosure which houses the modules and provides control power and a master controller. The six 200 kW modules have a combined power rating of 1.2 MW. The pulse width modulation converter system operates at 24 kHz and contains inverters with power metal-oxide-semiconductor field effect transistors (MOSFETs) as the principal inverter components, 200 kW power transformers and power inductors, and full-bridge rectifiers with fast recovery diodes. The converter modules have a volume power density of 1.0 MW/m/sup 3/ and a mass power density of 1.2 kW/kg. The converter design and test results are described. >

Constant voltage constant frequency inverter and method for controlling the same

Abstract: A CVCF (Constant Voltage Constant Frequency) inverter includes a main circuit, a voltage control loop, and a frequency control loop. In a normal operating mode, constant voltage, constant frequency control is carried out by these loops. In a lap switching operation, if a comparator detects that the output current of the inverter exceeds a predetermined level, a switch is closed so that the effective power component computed by an effective power computing unit is inputted to the frequency control loop. The output frequency of the inverter is controlled by changing a reference frequency in response to the effective power. This reduces the phase difference between the output voltage of the inverter and an external power supply, thus decreasing a cross current. This makes it possible to protect the components of the inverter and to supply power reliably.

Probabilistic design of high quality power supply photovoltaic systems

Abstract: The stand-alone application of photovoltaic (PV) systems, at current industrial production technological levels, could provide a viable solution to the problem of producing electricity for users located far away from power distribution systems. The author discusses the criteria for calculating the sizes of PV peak power and energy storage of a highly reliable power supply for special loads, with the aim of reaching the desired availability level. Adopting the criteria of loss of load probability (LOLP), the sizes of PV peak power and energy storage of the system are calculated in two steps. An initial provisional calculation is made, followed by a simulation of the most critical conditions, as a sequence of days with a minimum level of irradiation calculated probabilistically. A simple iterative process is adopted to evaluate performance. >