Showing papers on "Maximum power point tracking published in 2000"

Comparative study of maximum power point tracking algorithms using an experimental, programmable, maximum power point tracking test bed

Abstract: Maximum power point tracking (MPPT) is important in solar power systems because it reduces the solar array cost by decreasing the number of solar panels needed to obtain the desired output power. Several different MPPT methods have been proposed, but there has been no comprehensive experimental comparison between all the different algorithms and their overall maximum power point (MPP) tracking efficiencies under varying conditions (i.e. Illumination, temperature, and load). This paper such a comparison. Results are using a microprocessor controlled MPPT powered by a 250 W photovoltaic (PV) array and also a PV array simulator.

A fuzzy-logic-controlled single-stage converter for PV-powered lighting system applications

Abstract: This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

Application of radial basis function networks for solar-array modelling and maximum power-point prediction

Abstract: A neural network-based approach for solar array modelling is presented. The logic hidden unit of the proposed network consists of a set of nonlinear radial basis functions (RBFs) which are connected directly to the input vector. The links between hidden and output units are linear. The model can be trained using a random set of data collected from a real photovoltaic (PV) plant. The training procedures are fast and the accuracy of the trained models is comparable with that of the conventional model. The principle and training procedures of the RBF-network modelling when applied to emulate the I-V characteristics of PV arrays are discussed. Simulation results of the trained RBF networks for modelling a PV array and predicting the maximum power points of a real PV panel are presented.

Past, present and future of grid connected photovoltaic- and hybrid-power-systems

Abstract: As a short introduction on the general development and forecast of world market in photovoltaics (PV) are presented. The general classification introduces grid connected, stand alone, large scale and roof-top PV-systems. The core of presentation concentrates on the development and trends of converters for grid connected PV-systems. The novel multi-string converter is introduced representing one of the major trends in PV system technology towards modular PV-system design based on string converter technology with low specific costs and optimal energy yield. A brief excursion into the area of hybrid power systems deals with the development of hybrid power system technology using some representative examples installed by SMA around the world. As one of the future trends in that area a new bi-directional battery-converter for a modularly-structured hybrid power system technology is introduced.

Inverter circuit and method of operation

Abstract: An inverter includes a first switch to disconnect an output of the inverter from any device connected thereto; a second switch to disconnect and connect an input of the inverter from direct current fed to the inverter; a discharge device to discharge any residual charge on a large capacitor; a voltage sensor to measure input DC voltage to the inverter; a current sensor to measure input DC current to the inverter; and a data recorder to provide a current voltage trace to provide a current-voltage curve tracer to provide current-voltage curve data that may then be used to calibrate a maximum power point tracker or alternatively sense array shading.

Transformerless 3 phase power inverter

Abstract: The invention in the simplest form is an improved transformerless 3 phase power inverter topology and control method for power distribution systems. This 3 phase power inverter system provides the necessary output voltage and current waveform regulation, harmonic distortion rejection, very low output impedance, and ultra low DC offset of the output AC power, even when exposed to a high magnitude of the non-linear, single phase, or the unbalanced loading.

Using power line carrier communications to prevent islanding [of PV power systems]

Abstract: Islanding of grid-connected photovoltaic (PV) power systems jeopardizes personnel and equipment and must therefore be prevented. Existing islanding prevention schemes are undesirable because they fail for certain relatively common customer loads and when more than one PV power system is present, degrade PV power quality, reduce system efficiency, and increase system complexity. These problems can be overcome using power line carrier communications. (PLCC) and an inexpensive, purpose-designed receiver. The use of PLCC for islanding prevention is discussed. In this paper, including considerations for maximum anti-islanding effectiveness. Also, a low-cost receiver for a commercial PLCC system is described and demonstrated. This receiver demonstrates the feasibility of PLCC-based islanding prevention.

Maximum power point tracking with capacitor identifier for photovoltaic power system

Abstract: A perturbation and observation method with a capacitor identifier is presented for maximum power point tracking (MPPT) in a photovoltaic power system. Usually, by increasing or decreasing the duty ratio of on-state of switching device, the maximum power point is tracked. The variation of duty ratio is determined by considering its circuit parameters. However, it is known that actual capacitance of an electrolytic capacitor in parallel with the photovoltaic array has 50% tolerance of its nominal value. If the variation of duty ratio is determined based on its nominal value, the performance of the MPPT is degraded. Thus, we must change the variation of the duty ratio accordingly, based on its actual value. In the system presented, the model reference adaptive system is adapted to identify the capacitor, so the capacitance can be accurately estimated and the variation of the duty ratio can be corrected by the estimated value. As a result, the high performance of the MPPT may be obtained. Experimental results are presented using a proposed power inverter using buck-boost chopper circuits.

Simple maximum power point tracker for photovoltaic arrays

Abstract: A new technique is presented for tracking the maximum power point (MPP) of solar arrays. Although the control circuit is extremely simple and robust, its dynamics are complex. The MPP becomes inherently the global attractor of the system, thus ensuring optimum operation under transient and steady-state conditions. Experimental results confirm excellent tracking effectiveness and rapid dynamic response.

Energy management uninterruptible power supply system

Abstract: A power system is provided in which a grid supplies electrical power to a load and in which backup power is provided from one of a generator and a dc storage device. The power system includes a standalone inverter having an input and an output. The output of the standalone inverter is connected to the load. The power system includes a grid parallel inverter having an input and an output. The output of the grid parallel inverter is connected to the grid. A dc bus is electrically connected to the input of the standalone inverter and to the input of the grid parallel inverter.

Maximum power point tracking control of photovoltaic generation system under non-uniform insolation by means of monitoring cells

Abstract: A photovoltaic power generation system (PV system) is operated under various insolation conditions. Sometimes the PV system is operated under nonuniform insolation, which may generate several maximum output power points on the V-I curve of the PV array and raises serious problem on maximum power point tracking (MPPT) control of the system. In order to solve this problem, the authors propose a novel practical MPPT method, which uses monitoring cells to get a proper starting point of operation as well as the incremental resistance method (dV/dI method).

Power supplies having protection circuits

Abstract: A power supply including an inverter receiving a DC input signal from a DC input source ( 11 ). The inverter is comprised of two half bridges (S 1 A, S 2 A and S 1 B, S 2 B). Each inverter is driven by a signal source ( 13 A, 13 B), which outputs an AC signal. The output from each inverter is input to a first stage harmonic filter. The power supply includes an output circuit that includes first and second rectifiers (D 1, D 2 ) arranged about a point so that if the inverter attempts to drive the point beyond a predetermined first and second voltage, the respective rectifier conducts in order to return at least one of power and current to the DC input source. The output from the first harmonic filter (L 1 A, C 1; L 1 B, C 1 ) is output to a second harmonic filter (L 2, C 2 ) and is then output from the power supply.

Short-current pulse based adaptive maximum-power-point tracking for photovoltaic power generation system

Abstract: This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems The method is based on the use of a short-current pulse of the PV array to determine an optimum operating current for the maximum output power and completely differs from conventional hill-climbing based methods In the proposed system, the optimum operating current is instantaneously determined by taking a product of the short-current pulse amplitude and a parameter k because the optimum operating current is exactly proportional to the short current under various conditions of illuminance and temperature Also, the system offers an identification function of k by means of fast power-vs-current curve scanning, which makes the short-current pulse based MPPT adaptive to disturbances such as shades partially covering the PV panels The above adaptive MPPT algorithm has been adopted to a current-controlled boost chopper and a multiple power converter system composed by PV-chopper modules Various operating characteristics have been examined, and excellent MPPT performance has been confirmed through the experimental tests

Passivity/sliding mode control of a stand alone hybrid generation system

Abstract: Fil: Valenciaga, Fernando. Universidad Nacional de La Plata. Facultad de Ingenieria. Departamento de Electrotecnia. Laboratorio de Electronica Industrial, Control e Instrumentacion; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata; Argentina

Real-time maximum power point tracking for grid-connected photovoltaic systems

Abstract: The paper presents a model-based method for photovoltaic array maximum power point prediction. The method was tested successfully on a small grid-connected PV system. A three-phase IGBT-voltage-source inverter is used as the power conditioner and a DSP-controller is employed to perform real-time control and prediction functions. The system and experimental results obtained are presented in the paper.

Photovoltaic converter system suitable for use in small scale stand-alone or grid connected applications

Abstract: Of the commercially-available solutions for the conversion of energy from photovoltaic arrays into a usable form, a large number consist of systems which have been developed for a dedicated application and are thus very inflexible. Those that are available as a generic module for use in a variety of environments are often restricted to a single mode of operation, for example utility supply only. A generic modular photovoltaic power conversion system is presented, aimed at single-phase applications which can supply passive AC and DC loads with a regulated voltage or by way of a maximum power tracking system with the maximum power available from the array. In addition a live AC load such as the utility can be supplied with maximum array power. The system is small, light and can be constructed from readily available components.

Power supply system for distributed source

Abstract: PROBLEM TO BE SOLVED: To provide a power supply system for a distributed source, installing a distributed power source system in a plot of a power user by a power supply provider to perform power supply to the user, diagnosis of system operation, etc. SOLUTION: This system includes a distributed power source system 16, supplying power of commercial frequency to a load 8 of a specific user, additionally performing system linkage and a system managing means 15 connected to each distributed power source system via a communication network 12; the distributed power source system 16 includes a solar battery 1, a fuel cell 2, a storage battery 3, a power converter means 4 for system-linking power output from these power-generating means, a power condition monitor means 6, and a system control means 7; and the system control means 7 communicates operating information of the distributed power source system 16 to the system managing means 15 and controls the operating condition of the power converter means 4, according to the indication received from the system-managing means 15.

Fuzzy logic implementation for photovoltaic maximum power tracking

Abstract: The paper presents a simulation study and an experimental implementation of a fuzzy logic controller (FLC) for Cuk converter in a stand alone photovoltaic (PV) energy scheme. DC-DC converters are used to convert the unregulated DC input into a regulated DC output at a desired voltage level. A FL algorithm is selected and used to control the PV nonlinear system. The control objective for Cuk converter is to move the operating point of the PV system to its peak power point. A system that consists of a PV generator, converter, AC PWM inverter and load models is simulated, analyzed, and experimentally implemented. The simulated system with FLC is investigated at different solar insolation levels. The fixed structure FLC shows a robust performance when applied on a wide operating range of the proposed converter and AC PWM inverter.

A Micromachined Vibration-Induced Power Generator For Low Power Sensors Of Robotic Systems

Abstract: This paper presents the design, analysis, and experimental results of a vibration-induced power generator with total volume of -1 cm3 that uses laser-micromachined springs as resonating structures. The goal of our research is to create a minimally sized electric power generator capable of producing enough voltage to drive low-power IC circuit systems or micro sensors for robotic and automation applications where mechanical vibrations are present. Potential applications for the generator may also include mobile phone and heart-pacers where human motions can be used as a source of mechanical energy. Thus far, we have produced a generator capable of producing 2V DC with 64Hz input frequency with <200pm input vibration amplitude.

Power management circuit for battery systems

Abstract: A power management circuit (10) for battery systems composed of a switch (16, 32) defining a single charge/discharge path. The switch (16, 32) is selectively controlled using analog signals to couple a battery (20) to a power source for charging, or to couple the battery to an active load (14). For charging, the switch is controlled by a controller circuit (18, 22, 30) that monitors the battery voltage, the power source and the individual battery cells. The battery is only coupled to the power source if it is determined that the power source is present and that each of the battery cells is capable of receiving a charge. During discharge, the controller monitors the discharge current from the battery and compares this value to a threshold current. If the discharge current falls below the threshold, the switch is controlled to decouple the battery from the load. In this way, an overcharge condition is avoided if, for example, a power source is reapplied to the system. In a multiple battery system where the battery and battery circuits are connected in parallel to a load and a power source, the use of the threshold current prevents a cross-conduction between batteries.

Analysis of utility interactive photovoltaic generation system using a single power static inverter

Abstract: This paper presents the analysis of a static conversion system for treatment of the solar energy from photovoltaic panels. This system is interconnected with the mains power supply, contributing to the generation of the electrical energy. The power structure is composed of a current-fed push-pull converter, a buck converter, and a current inverter. The main features of the system are: simple control strategy, robustness, lower harmonic distortion of the current and natural isolation. The principle of operation, design procedure and experimental results are presented.

Evaluating MPPT converter topologies using a Matlab PV model

Abstract: An accurate PV module electrical model is presented based on the Shockley diode equation. The simple model has a photo-current current source, a single diode junction and a series resistance, and includes temperature dependences. The method of parameter extraction and model evaluation in Matlab is demonstrated for a typical 60W solar panel. This model is used to investigate the variation of maximumpower point with temperature and insolation levels. A comparison of buck versus boostmaximum power point tracker (MPPT) topologies is made, and compared with a direct connection to a constant voltage (battery) load. The boost converter is shown to have a slight advantage over the buck, since it can always track the maximum power point.

Four-quadrant AC-AC drive and method

Abstract: An electric drive apparatus and method for controlling medium-voltage alternating current motors wherein a multi-phase power transformer having multiple secondary windings provides multi-phase power to multiple power cells which provide four quadrant operation. Each power cell has a single-phase output and is controllable by a modulation controller. The power cells are connected in series thus permitting the maximum output voltage for each cell to be less than the maximum line-to-line voltage. Each power cell can have a rectifier portion to convert input AC-to-DC, capacitors, an output DC-to-AC inverter, a regenerative bridge converter connected in parallel with the rectifier portion and a local modulation controller connected to a master controller.

Controller arrangement for boost converter systems sourced from solar photovoltaic arrays or other maximum power sources

Abstract: Conventional power converter systems, such as boost converters, derive their input from sources that may be considered to have negligible output impedances. As such, the use of quite simple conventional control algorithms suffice to give acceptable performance. When the output impedance of the source to such a converter is no longer negligible, and moreover if the source has a markedly nonlinear output impedance, the simple conventional algorithms will no longer be adequate to satisfy the control requirements of the converter. The effect of driving such a converter from a type of source, for example a photovoltaic array which has a point of maximum power delivery within the operating range is discussed, as is the impact that the use of such a source has upon the control requirements of the converter. A novel control arrangement, which includes a complete embedded maximum power tracker, is then presented together with results validating the proposed controller.

A RISC-microcontroller based photovoltaic system for illumination applications

Abstract: This work presents the development of a solar powered public illumination system used for a waste recycle campaign in the city of Sao Paulo (Brazil). A lighting pole is installed in a street for area illumination. It has a translucent sign vinyl which shines in the sun and glows at night with fluorescent lamps; there are stainless steel receptacles used as recycle trash bin collectors at the base of the pole. The intented use of such a photovoltaic array to power the glassy advertisement works as a way of bringing solar energy into daily use, and to encourage companies in funding local recycle awareness campaigns. Solar energy is captured by a photovoltaic solar panel and delivered into a lead-acid battery through a flyback converter. The converter also performs the function of tracking the maximum power operating conditions. At night, a resonant push-pull current-fed inverter drives a fluorescent lamp. The system is controlled by a RISC PIC16C74 microcontroller, which searches the maximum power point by commanding the flyback converter with a hill-climbing algorithm, monitors the battery energy level, and turns on the fluorescent inverter with a real-time internal clock. Serial communication is provided for connection to a portable computer, which is used for battery life management and time clock settings. The paper shows the implementation of the whole system and describes comprehensive field tests.

Maximum power point tracking with capacitor identificator for photovoltaic power system

Abstract: This paper presents a perturbation and observation method with an identifier of capacitor for the maximum power point tracking (MPPT) in a photovoltaic power system. Usually, by increasing or decreasing the duty ratio of on-state of switching device, the maximum power point is tracked. The variation of duty ratio is determined by considering its circuit parameters. However, it is known that actual capacitance of an electrolytic capacitor in parallel with the photovoltaic array has 50% error of its nominal value. If the variation of duty ratio is determined based on its nominal value, the performance of MPPT is degraded. Thus, accordingly we must change the variation of duty ratio based on its actual value. In our system, we adapt the model reference adaptive system to identify the capacitor, then we can estimate the accurate capacitance and correct the variation of duty ratio. As a result, we may obtain the high performance of MPPT. Experimental results are shown using a proposed power inverter using buck-boost chopper circuits.

Photovoltaic power generation apparatus and control method thereof

Abstract: A photovoltaic power generation apparatus having a plurality of power converters, respectively connected to a plurality of solar battery arrays, for converting direct-current power generated by the solar battery arrays to alternating-current power so as to provide the alternating-current power to a commercial power system. The photovoltaic power generation apparatus is so constructed that the plurality of power converters do not simultaneously suspend operation when an abnormal state is detected, in order to prevent generation of an electrical stress or reduction of the power generation amount caused by simultaneous operation suspension of the power converters or repeated operation suspension and operation resume. When the power generation amount of each solar battery array is different, a power converter connected to the solar battery array of the smallest power generation amount is set in the first-to-suspend condition.

Maximum output control of photovoltaic (PV) array

Abstract: A photovoltaic (PV) system output depends on environmental parameters such as the solar insolation and the PV module temperature. If it is possible to predict the maximum power point under the outdoor environment and to operate at that point, the PV system can generate the maximum output every time. In this paper, a maximum power point control method that maximizes the output of a PV array is proposed. This method determines the maximum output operation point from the I-V characteristics introducing empirically the effects of the solar insolation and the module temperature. The authors derived two main parameters from this analysis; one is the power gain G, and another is the environmental operation parameter X. At the operation point determined by this method, G becomes larger than that of under the same environmental conditions. G becomes large with the increase of X, and the large X mainly means low solar insolation. The characteristics of PV module which will supply more power especially at large X should satisfy the following points; the fill factor of the module should be lower and the short circuit current of the module should be larger than those of arrays currently available in the market.

Power fluctuation smoothing apparatus and method for controlling distributed power supply system comprising the same

Abstract: PROBLEM TO BE SOLVED: To surely smooth fluctuation of output to a power system due to distributed power supply such as a wind power generation system and a solar power generation system by preventing shortage of power accumulation or full charging of a power accumulator. SOLUTION: A distributed power supply system 10 consisting of distributed power supply 9, a power fluctuation smoothing apparatus 1 and a power converter 15 is connected to a power system 12, a controller 4 of the power fluctuation smoothing apparatus 1 is composed of an output detector 5, an accumulated power detector 6, a target value setting device 7 for setting a target output value, and a charge/discharge controller 8 for controlling a charger/ discharger 3. An output of the distributed power supply 9 and amount of accumulated power of a power accumulator 2 are detected. A running average value in the preset period of an output of the distributed power supply 9 is compensated with an output target adjusting value which is preset depending on the amount of accumulated power to set an output target value to the side of the power system 12. When an output of the distributed power supply 9 is larger than the output target value, an extra power is used to charge the power accumulator 2. When an output is smaller than the output target value, shortage is compensated with the power discharged from the power accumulator 2 until the output to the side of power system 12 reaches the output target value. COPYRIGHT: (C)2002,JPO

Control and interfacing of bi-directional inverters for off-grid and weak grid photovoltaic power systems

Abstract: Photovoltaics (PV) is one of the most cost-effective, reliable and durable energy sources to provide electricity in remote areas not connected to a grid. In some parts of the world grid-connected PV systems also help utilities to alleviate the need to install or operate costly power plants by supplementing and meeting high peak hours of electricity demand. The key to the widespread application of PV power plants is the availability of efficient and low cost power electronic equipment. A photovoltaic generator is a current source depending on solar radiation intensity and temperature. Simple charge controllers and DC-DC converters with maximum power point tracking are used to interface solar panels with batteries. There are different types of inverters for converting the DC power from batteries and/or solar panels to AC power. This paper describes the application of bi-directional inverters for remote area power systems using PV, diesel generators and battery storage. Use of bidirectional inverters to improve power quality and reliability in weak grids is also presented.