Showing papers on "Maximum power point tracking published in 1997"

Integrated photovoltaic maximum power point tracking converter

Abstract: A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed to use an integrated MPPT converter as part of the PV panel. It is proposed that this integrated MPPT uses a simple controller in order to be cost effective. Furthermore, the power converter has to be very efficient, in order to transfer more energy to the load than a directly-coupled system. This is achieved by using a simple soft-switched topology. A much higher conversion efficiency at lower cost will then result, making the MPPT an affordable solution for small PV energy systems.

Neural network based estimation of maximum power generation from PV module using environmental information

Abstract: This paper presents an application of an artificial neural network for the estimation of maximum power generation from PV module. The output power from a PV module depends on environmental factors such as irradiation and cell temperature. For the operation planning of power systems, the prediction of the power generation is inevitable for PV systems. For this purpose, irradiation, temperature and wind velocity are utilized as the input information to the proposed neural network. The output is the predicted maximum power generation under the condition given by those environmental factors. The efficiency of the proposed estimation scheme is evaluated by using actual data on daily, monthly and yearly bases. The proposed method gives highly accurate predictions compared with predictions using the conventional multiple regression model.

Power control apparatus for solar power generation system

Abstract: In a power control apparatus of a solar power generation system for converting power generated by a solar panel and supplying the converted power to a load, the output voltage and output current of the solar panel are sensed, and, under ordinary conditions, MPPT control is performed so that the solar cells will operate at a maximum output point. If the output power of the solar panel exceeds a predetermined power, a power conversion unit is controlled so as to raise the output voltage of the solar panel, thereby limiting the output power of the solar panel. As a result, excessive power is prevented from being output by the power control apparatus.

Solar power generation apparatus and power control device therefor

Abstract: In order to extract maximum power from a solar cell, maximum power point tracking (MPPT) control is performed under ordinary circumstances. If the output current of the solar cell becomes too small, the operating point of the solar cell is caused to fluctuate over a range wider than that of MPPT control at a period longer than that of MPPT control and the output voltage and current of the solar cell is sampled. In a case where it is indicated by power values obtained from the sample voltage values and current values that a plurality of maximal points of power value exist, a voltage value corresponding to a power value indicative of the largest value is set as the operating point of the solar cell.

Solar cell power source device

Abstract: A solar cell power source device is disclosed which optimizes the power output of the solar cell by detecting a maximum power point of the solar cell and controlling the duty cycle of a switching transistor in a switching power converter such that the output current of the solar cell follows the maximum power point. Also shown is a pulse width modulation controller which multiplies the output voltage of the solar cell by the output current of the solar cell to obtain a power detecting signal, samples the power detecting signal during two different sample periods to determine if the power output is decreasing, and modulating the pulses output to the switching transistor of the switching power converter in order to maintain the power output of the solar cell at the maximum power point.

Apparatus for controlling a solar array power system

Abstract: A system for controlling power supplied by a solar array panel to one of either a load or a battery for optimal power consumption is disclosed. The solar array power control system of the present invention includes a power stage for directing the solar array to discharge an appropriate amount of current, a signal conditioner for receiving and conditioning voltage and current signals from the solar array and determining the signs of the time derivatives of solar array voltage and power, a processor for evaluating the signs of the time derivatives of solar array power voltage and for directing operation of either a battery current control mode or a peak power tracking mode and a high gain amplifier for directing an appropriate voltage to the power stage according to the operating mode. The signal conditioner, processor and high gain amplifier cooperate to determine whether the solar array is capable of supplying the power demanded by at least one of the battery and the load. When it has been determined that the required power level to be supplied from the solar array is within the capability of the solar array, the system commands the solar array to discharge the exact power demanded. In times when the solar array is not capable of completely satisfying the required power level, the system commands the solar array to discharge the maximum power available under the present conditions.

Electric power supplying apparatus using unstable electric power supply and control method therefor

Abstract: An electric power conversion unit 2 for driving a pump 3 run by electric power generated by a solar panel 1 , a storage battery 5 connected to the solar panel 1 via the switch 6 , and a controller 7 for controlling the electric power conversion unit 2 and the switch 6 are provided. The controller 7 closes the switch 6 during any period when the amount of insolation is large and performs the maximum power point tracking control of the solar panel 1 , and otherwise, controls the electric power conversion unit 2 to drive at one of plural fixed frequencies in dependence upon an output voltage from the solar panel 1 by closing the switch 6 . Accordingly, it is possible to utilize output from an unstable electric power supply efficiently, such as a solar cell, thereby providing a reliable electric motor driving apparatus having a simple configuration and a control method therefor.

Control of DC/DC converters for solar energy system with maximum power tracking

Abstract: Solar power converters were used to convert the electrical energy from solar arrays to a stable and reliable power source. The object of this paper is to analyze and design DC/DC power converters of different types in a PV power system to investigate the performance of such converters. A simple method which combines discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The system is kept to operate close to the MPPs, thus the maximum possible power transfer from the solar array is achieved. The implementation of the proposed power converter system was based on a digital signal processor. Experimental tests were carried out for buck, boost and buck-boost power converters using a simple maximum power point tracking algorithm. The efficiencies for the system with different power converters are compared and presented.

Method and apparatus for reducing common mode voltage in multi-phase power converters

Abstract: Multi-phase power is provided to a load via the use of an inverter which has an even number of inverter legs. DC source voltage, such as from an AC-to-DC converter receiving power from a main AC power supply or from an independent DC power source such as a battery, is provided to the inverter. The DC source voltage is provided on DC bus lines of the inverter so as to be symmetric about ground. Switching devices in the inverter legs are controlled using a modulation strategy to synthesize desired output voltage waveforms on the inverter leg outputs from the voltage on the DC bus lines. The modulation strategy is subject to a modulation constraint such that, at any one time, half of the inverter legs provide a positive output voltage signal with respect to ground, and the other half of the inverter legs provide a negative output voltage signal, of equal magnitude, with respect to ground. If the multi-phase load to which the inverter is connected is a balanced impedance, the present invention makes possible the reduction or elimination of common mode voltage and, therefore, common mode current. Load balancing may be achieved using a multi-phase second order filter connected between the inverter leg outputs and the load. The present invention may be applied to power conversion systems including hard switching or soft switching inverters, and may be used in combination with conventional inverter modulation strategies.

A new scheme for maximum photovoltaic power tracking control

Abstract: It is shown that the derivative (dp/sub s//de/sub s/) of output power (p/sub s/) with respect to output voltage (e/sub s/) of a photovoltaic array is equal to zero at the maximum power point. This kind of relationship is independent of insolation and temperature. This property may be utilized to perform maximum power tracking control, that is, at all insolation and temperature levels, the maximum power point can be obtained by regulating dp/sub s//de/sub s/ toward zero. Based on this concept, a new scheme of maximum power tracking control is proposed and applied to a utility-interactive photovoltaic power conditioning system, where the boost chopper is responsible for maximum power tracking control and the inverter responsible for unity power factor control and constant DC input voltage control. The related design method is described. The usefulness and validity of the proposed method are verified by simulation. Compared to conventional methods, this method show a considerably high tracking performance.

Power flow of photovoltaic system using buck-boost PWM power inverter

Abstract: This paper presents a buck-boost PWM power inverter and its application for residential photovoltaic power systems. The PWM power inverter is realized by combining two sets of high frequency buck-boost choppers and by making them operate in the discontinuous conduction mode. A PV power system with the power inverter has the following advantages: (1) the power generated by the photovoltaic array can be transferred to the load and the utility line under any array voltage; (2) isolation between the photovoltaic array and the utility line is performed by a small high frequency reactor operating as energy storage element; (3) unity power factor operation is provided; (4) there is no need of a reactor for interconnection with the utility line; and (5) so the system configuration is very simple. The input-output characteristics of the system are analyzed. As a result, the ripple component of the array current and the power flow between the interface and the utility line are derived and verified experimentally.

Power supply controller in computer system for supplying backup power to volatile memory while the computer receives AC power

Abstract: In a computer system equipped with a hibernation type resume function including standby control functions, a power supply controller detects whether AC power or battery power is used as power for the system. When AC power is supplied, power is kept supplied to a memory even when a power switch is set off. When the power switch is set on later, an AC standby control function to set the system back to the operational state is executed based on the memory contents.

Wind power site

Abstract: The invention concerns a wind power site (2) which comprises at least two wind power plants (4) and a line-side power converter station (46), each wind power plant (4) comprising a rotor (6), a generator (24), a rectifier (30), a smoothing choke (36) and an output-regulating arrangement (62). The line-side power converter station (46) comprises a smoothing choke (48), a power inverter (50), a matching transformer (52), a filter (28) and a regulating arrangement (102), the wind power plants (4) being electrically connected in parallel on the direct current side, and the line-side power converter station (46) being electrically connected in series on the direct current side to the wind power plants (4) connected in parallel on the direct current side. In this way, a wind power site (2) is obtained whose entire available wind power output can be transferred into a regional supply network.

Development and testing of a 20-kW grid interactive photovoltaic power conditioning system in Western Australia

Abstract: A prototype current-controlled power conditioning system has been developed and tested on a weak rural feeder line at Kalbarri, about 600 km northwest of Perth in Western Australia. This system sources 20 kW of power from a photovoltaic array with maximum power point tracking control. In addition, it provides voltage support for the power grid at Kalbarri by varying its reactive power in response to the measured voltage at the point of connection. This paper describes the development and testing of the power conditioning system.

Apparatus and method for optimizing power distributed in a broadband signal system

Abstract: A broadband system that simultaneously delivers output power and supplies a broadband signal and has a redundant bus power supply. The system includes a central office having a video gateway. The system further includes a plurality of nodes having a power supply and a combiner for coupling the broadband signal to the power supply output. At each node, a distribution line delivers broadcast services and power to a consumer site. The power supply comprises a battery source, rectifier, filter, inverter and generator to provide a secondary DC power source. The various elements of the power supply are diode isolated and are interconnected via a redundant power bus, thus allowing power to be maintained to the subscribers even in case of failure of one or more elements of the power supply. The power supply further includes a plurality of inverters, each inverter supplies power to a distribution line. A controller monitors the status of each inverter and secondary power source. In addition, the controller monitors output power supplied by each inverter. The controller exchanges control and status information with the power supply and secondary power source through a memory array. By issuing control data to the power supply, the controller compensates for a detected loss of power supplied to each distribution line. The controller transmits status information to the central office.

An active power filter implemented with a three-level NPC voltage-source inverter

Abstract: This paper presents an active power filter implemented using a three-level neutral point-clamped voltage-source inverter. The active power filter can compensate current harmonics and reactive power in medium voltage distribution systems. The paper presents the principles of operation and design criteria for both the power and control circuits. Finally, the viability of the proposed scheme is shown with computer simulation using Matlab.

Inverter apparatus and solar power generation apparatus

Abstract: In order to provide an inverter apparatus and a solar power generation apparatus in which when a main AC power system (5) has suffered, e.g., a power failure, the operation mode of an inverter (2) in the tie operation with the main AC power system (5) can be easily and safely switched from the tie operation mode to the self-support operation mode, and electric power can be supplied to a load (4) directly using normal indoor wiring, the open/closed state of a switch (3) for opening/closing a connection between the output terminal of the inverter (2) and the main AC power system (5) is detected, and the self-support operation of the inverter (2) is started when the open state of the switch (3) is detected.

Advanced photovoltaic inverter with additional active power line conditioning capability

Abstract: This paper presents an advanced photovoltaic inverter which can deliver the maximum power from photovoltaic arrays to the utility grid for all sunlight conditions, as well as simultaneously providing power conditioning to suppress power line distortions. A new control strategy is developed to maximize the inverter output from the photovoltaic array and to suppress current harmonics in the power line using a single inverter configuration. A new control strategy and experimental results are given.

Power supply and electronic ballast with low-cost inverter bootstrap power source

Abstract: A power supply (10) for powering a load (500) includes an inverter (100), a series resonant output circuit (200), and a bootstrap power source (300) for supplying operating power to an inverter driver circuit (110). The bootstrap power source (300) is coupled in series with the load (500) via a dc blocking capacitor (240) and provides automatic shutdown of the inverter (100) by ceasing to supply operating power to the inverter driver circuit (110) when the load (500) fails to conduct current or is removed.

A hybrid wind-photovoltaic power supply for a telecommunication system

Abstract: This paper describes a stand-alone hybrid wind-photovoltaic power plant for a remote telecommunication system located on the Black Sea Coast. First, the wind and solar potential of the site and also the load profile were assessed. It is shown that the two energy sources are complementary, so it is possible to have a better energy utilization factor. As a consequence, the storage unit resulting is smaller than in the case of individual wind or PV systems. The power system consists of a 1500 W wind turbine and a 900 W photovoltaic array. Since solar and wind energy converters are finite sources of power, the energy capture efficiency is improved by using a power conditioner (which includes a peak-power tracker and a battery charger). A 220 V/50 Hz inverter was used. The power system was tested and monitored for one year under real conditions in the authors' test facility, also located on the Black Sea Coast.

Load sharing operation of a 14 kW photovoltaic/wind hybrid power system

Abstract: In this paper, a design procedure for photovoltaic/wind hybrid power generation system is presented. The hybrid system is composed of a DC/DC converter for photovoltaic energy conversion, a DC/DC converter for wind energy conversion, a four switch IGBT inverter converting the combined DC power to the AC power and a backup power battery. Here, it is very important to select the desired battery size to meet the stable output and economic cost aspect since this system utilizes a fluctuating and finite energy resource. The purpose of this paper is to develop a sizing method for the PV/wind energy hybrid system with load sharing operation. The method demonstrates a simple tool to determine the desired battery size that satisfies the energy demand from the user with the photovoltaic and wind natural source. The proposed method is verified on a 14 kW hybrid power system including a 10 kW PV generator and a 4 kW wind generator established in Cheju island, Korea.

Operation control method of distributed power supply equipment

Abstract: PROBLEM TO BE SOLVED: To realize a parallel synchronous operations of respective distributed power supply devices, when the respective distributed power supply devices are paralleled off from a power system into self-contained operations, while synchronism is not obtained by exchanging information on output powers, output currents, etc., between the distributed power supply devices. SOLUTION: When a plurality of distributed power supply devices (solar generators 1) which are paralleled off from a power system 5 are put into self-contained operations, an inverter 3 of one of the respective distributed power supply devices is used as a reference inverter. The reference inverter is operated by a voltage control operation to form an AC voltage source. After the reference inverter generates a voltage, the inverters 3 of the remaining distributed power supply devices are operated by current control operation synchronously with the output voltage of the reference inverter. Through the current control operation, AC-current sources synchronous with the AC voltage source are respectively formed, and the parallel synchronous operations of the respective distributed power supply devices are realized.

Solar generator for generating direct current power by sunlight and outputting generated power to commercial AC power source

Abstract: An air conditioner equipped with a solar generator is disclosed. The solar generator is capable of converting the DC power generated by a solar cell into the AC power whose voltage and frequency correspond to that of the commercial power source. The electrical power generated by the solar cell and the electrical power consumed by the air conditioner are monitored and may be displayed. The DC power generated by the solar cell is used directly by the air conditioner or used indirectly as the commercial power source by merging the converted AC power to the commercial power source. Further, the converted AC power may be selectively merged to the commercial power source depending on the various states of the air conditioner, and the air conditioning operations may be regulated depending on the electrical power generated by the solar cell.

Photovoltaic power generation monitor system

Abstract: PROBLEM TO BE SOLVED: To measure various types of electric energy with a stable operation and high reliability by a method wherein a bought power, a sold power and a photovoltaic power are respectively measured by a power measuring means in accordance with the outputs of respective current transformers attached to a commercial AC power system side and a phtovoltaic power generation system side and those powers are indicated respectively. SOLUTION: A power is supplied to a load 30 from a distribution panel of a commercial power supply (commercial distribution panel) and a photovoltaic power from an inverter 20 is also supplied to the load 30. A power conversion unit 40 detects three types of powers, i.e., a solar power, a bought power and a sold power, which are outputted from the inverter 20 respectively and converts them into digital values. An indicator 50 has functions of indicating the three types of powers (or integrated electrical energy values if required), calculating an energy change, data logger, etc., and indicates received data on an indicating part. The power conversion unit 40 is connected to the indicator 50 with a communication line. With this constitution, various types of electric energy can be measured with a stable operation and high reliability. COPYRIGHT: (C)1998,JPO

Method for controlling power generating amount of wind power generator

Abstract: PROBLEM TO BE SOLVED: To perform demand balance without using a circuit for discharging power such as heater, by efficiently controlling the pitch angle even if the demand balance of power falls into the excessive supplying state SOLUTION: When a power generating method of a DC link is adopted in order to restrain the output fluctuation to be generated caused by fluctuation of wind, output of a power generator is automatically adjusted by temporarily storing electric power to a storage battery 9 as a function for preventing voltage from being raised resulting from excessive output to a system in the case where the system power demand is very low and less than output of a wind power generator and by decreasing the power generating amount through a process of adjusting the pitch angle of a blade by using the voltage of the storage battery as a wind speed signal and a pitch angle control signal in the case where the voltage of the storage battery 9 is further raised

Uninterruptive power supply having redundant function

Abstract: PROBLEM TO BE SOLVED: To provide an uninterruptive power supply having redundant functions which is capable of performing stable power supply to a load device and easily performing the maintenance of a battery or the like. SOLUTION: An uninterruptive power supply is constituted by a rectifier 1 converting an AC power into DC power, battery 11-1 to 11-n, charge circuit 2 supplying power to each battery, capacity residual amount detection mechanism 4 for detecting a capacity residual amount of each battery, connection condition detection mechanism 5 detecting connection of each battery, trouble detection mechanism 6 detecting troubles of each battery, I/F circuits 15-1 to 15-n connected to a battery unit, memory device 3 storing a data obtained from each detection mechanism, redundant control mechanism 7 referring to the memory device 3 determining from what battery outputting to a load side via a switch 10-1 to 10-n, inverter 8 converting an output from the battery into an AC power, and a changeover switch 9 switching a commercial power output and a battery output in the case of generating power interruption or the like. COPYRIGHT: (C)1999,JPO

MPPT for temperature compensation of photovoltaic system with neural networks

Abstract: In this paper, we investigate the possibilities of P/sub max/ control using the neural networks, a back propagation algorithm is used to train a neural network controller, and we also examine the optimal power converter using a step-up chopper circuit to operate the solar cell at an optimal compensated voltage. The proposed step-up MPPT system is studied by simulation and is implemented by using a microprocessor which controls the duty ratio of the IGBT boost converter.