Showing papers on "Maximum power point tracking published in 1998"

Implementation of a DSP-controlled photovoltaic system with peak power tracking

Abstract: Photovoltaic systems normally use a maximum power point tracking (MPPT) technique to continuously deliver the highest possible power to the load when variations in the insulation and temperature occur. It overcomes the problem of mismatch between the solar arrays and the given load. A simple method of tracking the maximum power points (MPPs) and forcing the system to operate close to these points is presented. The principle of energy conservation is used to derive the large- and small-signal model and transfer function. By using the proposed model, the drawbacks of the state-space-averaging method can be overcome. The TI320C25 digital signal processor (DSP) was used to implement the proposed MPPT controller, which controls the DC/DC converter in the photovoltaic system. Simulations and experimental results show excellent performance.

Generation unit sizing and cost analysis for stand-alone wind, photovoltaic, and hybrid wind/PV systems

Abstract: This paper presents the results of investigations on the application of wind, photovoltaic (PV), and hybrid wind/PV power generating systems for utilization as stand-alone systems. A simple numerical algorithm has been developed for generation unit sizing. It has been used to determine the optimum generation capacity and storage needed for a stand-alone, wind, PV, and hybrid wind/PV system for an experimental site in a remote area in Montana with a typical residential load. Generation and storage units for each system are properly sized in order to meet the annual load and minimize the total annual cost to the customer. In addition, an economic analysis has been performed for the above three scenarios and is used to justify the use of renewable energy versus constructing a line extension from the nearest existing power line to supply the load with conventional power. Annual average hourly values for load, wind speed, and insolation have been used.

Residential photovoltaic energy storage system

Abstract: This paper introduces a residential photovoltaic (PV) energy storage system, in which the PV power is controlled by a DC-DC power converter and transferred to a small battery energy storage system (BESS). For managing the power, a pattern of daily operation considering the load characteristic of the homeowner, the generation characteristic of the PV power, and the power-leveling demand of the electric utility is prescribed. The system looks up the pattern to select the operation mode, so that powers from the PV array, the batteries and the utility are utilized in a cost-effective manner. As for the control of the system, a novel control technique for the maximum power-point tracking (MPPT) of the PV array is proposed, in which the state-averaged model of the DC-DC power converter, including the dynamic model of the PV array, is derived. Accordingly, a high-performance discrete MPPT controller that tracks the maximum power point with zero-slope regulation and current-mode control is presented. With proposed arrangements on the control of the BESS and the current-to-power scaling factor setting, the DC-DC power converter is capable of combining with the BESS for performing the functions of power conditioning and active power filtering. An experimental 600 W system is implemented, and some simulation and experimental results are provided to demonstrate the effectiveness of the proposed system.

Study of maximum power tracking techniques and control of DC/DC converters for photovoltaic power system

Abstract: As the electric power supplied by solar arrays depends on the insolation, temperature and array voltage, it is necessary to control the operating points to draw the maximum power of the solar array. The object of this paper is to investigate the maximum power tracking algorithms which were often used to compare the tracking efficiencies for the system operating under different controls. Besides, different type DC/DC converters were designed to evaluate the converter performance. A simple method which combines a discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The implementation of the proposed converter system was based on a digital signal processor (DSP) and the experimental results are presented.

Comparative study of peak power tracking techniques for solar storage system

Abstract: As the power supplied by solar arrays depends upon the insolation, temperature and array voltage, it is necessary to control the operating points to draw the maximum power of the solar array. The object of this paper is to investigate the maximum power tracking algorithms which were often used to compare the tracking efficiencies for the system operating under different controls. A simple method which combines a discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The implementation of the proposed converter system was based on a digital signal processor (DSP). The experimental tests were carried out, the tracking efficiencies are confirmed by simulations and experimental results.

Performance optimization for doubly-fed wind power generation systems

Abstract: Significant variation of the resource kinetic energy, in the form of wind speed, results in substantially reduced energy capture in a fixed speed wind turbine. In order to increase the wind energy capture in the turbine, variable speed generation (VSG) strategies have been proposed and implemented. However, that requires an expensive AC/AC power converter which increases the capital investment significantly. Consequently doubly-fed systems have been proposed to reduce the size of the power converter and thereby the associated cost. Additionally, in doubly-fed systems, at a fixed operating point (power and speed), power flow can be regulated between the two winding systems on the machine. This feature can be utilized to essentially minimize losses in the machine associated with the given operating point or achieve other desired performance enhancements. In this paper, a brushless doubly-fed machine (BDFM) is utilized to develop a VSG wind power generator. The VSG controller employs a wind speed estimation based maximum power point tracker (MPPT) and a heuristic model based maximum efficiency point tracker (MEPT) to optimize the power output of the system. The controller has been verified for efficacy on a 1.5 kW laboratory VSG wind generator. The strategy is applicable to all doubly-fed configurations, including conventional wound rotor induction machines, Scherbius cascades, brushless doubly fed machines, and doubly-fed reluctance machines.

Two-loop controller for maximizing performance of a grid-connected photovoltaic-fuel cell hybrid power plant

Abstract: Maximizing performance of a grid-connected photovoltaic (PV)-fuel cell hybrid system by use of a two-loop controller is discussed. One loop is a neural network controller for maximum power point tracking, which extracts maximum available solar power from PV arrays under varying conditions of insolation, temperature, and system load. A real/reactive power controller (RRPC) is the other loop. The RRPC achieves the system's requirements for real and reactive powers by controlling incoming fuel to fuel cell stacks as well as switching control signals to a power conditioning subsystem. Results of time-domain simulations prove not only the effectiveness of the proposed computer models of the two-loop controller but also its applicability for use in stability analysis of the hybrid power plant.

Method and apparatus for providing uninterruptible power using a power controller and a redundant power controller

Abstract: A power supply system has a power input to receive input power from a power source, a power output to provide output power to a load, at least one battery module having a battery output that provides battery power, at least one power module coupled to the power input to receive the input power, coupled to the battery output to receive the battery power and coupled to the power output to provide the output power, a controller, coupled to the at least one power module, constructed and arranged to monitor and control the output power from the at least one power module, and a redundant controller, coupled to the at least one power module and to the controller, constructed and arranged to provide redundant monitoring and controlling of the output power from the at least one power module.

Control strategy for grid-connected DC-AC converters with load power factor correction

Abstract: The paper presents the modelling, analysis and design of a pulse width modulation voltage source inverter (PWM-VSI) to be connected between a DC source, which is supplied from a photovoltaic (PV) array and the AC grid. The control algorithm of the PWM-VSI applies the concepts of the instantaneous p-q (real-imaginary) power theory. The objective is to show that, with an adequate control, the converter can transfer the DC energy from PV array and improve the power factor (and the power quality) of the electrical system. Some design considerations are also discussed. A digital simulation and measurements on a small prototype model verified the feasibility of the proposed control method.

Novel solar cell power supply system using the multiple-input DC-DC converter

Abstract: Recently, clean electric power generation systems have attracted a great deal of social attention to exploit clean energy resources such as solar arrays, wind generators, fuel cells, etc. In this case, the multiple-input DC-DC power converter is useful to combine the several input power sources and to supply the regulated output voltage for the load. The novel solar cell power supply system using the buck-boost type two-input DC-DC converter is proposed, in which the solar array and the commercial AC line are exploited as power sources and they are combined by the two input windings of the energy-storage reactor. Also, its operation principle and performance characteristics are discussed. Furthermore, the solar cell optimum operating point tracker is proposed and examined. It is confirmed by the experiment that the proposed solar cell power supply system has the excellent performance characteristics.

A fuzzy logic based photovoltaic peak power tracking control

Abstract: This paper describes the analysis, modeling and implementation of a fuzzy based photovoltaic peak power tracking system. The maximum power of a photovoltaic system changes with temperature, solar intensity and load. An analytical model is built for the solar cell on the basis of the manufacturer characteristics. The solar panel is integrated with the converter model and a fuzzy algorithm is developed so as to perform an on-line search procedure to track the maximum power continuously. The system is implemented by an inexpensive RISC microcontroller. Experimental results have shown excellent performance, robustness with parameter variation, modularity for parallel operation at higher power, and ready to retrofit existing installations.

Optimal control of a grid-connected PV system for maximum power point tracking and unity power factor

Abstract: The paper discusses a model-based method to predict the maximum power point (MPP) of a PV array using the measured data of radiation and temperature. The proposed method can be embedded in a synchronous rotating reference frame (SRRF) current regulator. This ensures good performance voltage control and unity power factor current supply to the grid. A simulation study of the proposed control scheme has been carried out, and the results are presented in the paper.

An integrated maximum power point tracker for photovoltaic panels

Abstract: This paper proposes a maximum power point tracker (MPPT) for a photovoltaic panel, that is to be integrated with the panel during manufacturing. The MPPT is inexpensive, efficient and has few components that serve to increase the MPPT's mean time between failures (MTBF). The MPPT uses an inexpensive microcontroller to perform all of its functions. This includes maximum power point tracking, series battery voltage regulation, sensorless short circuit protection of the MPPT's converter and intelligent shutdown and wakeup at dusk and dawn. The MPPT can source 10 A to a 6-36 V lead-acid storage battery and can be connected in parallel or series with other MPPTs. The MPPT may be easily configured to perform output voltage regulation on passive and water pumping loads. It could also control the actuation of a diesel generator in a hybrid remote area power supply (RAPS). Energy transfer enhancements of up to 26%, compared to solar panels without MPPTs, have been measured, The complete component and materials cost of the MPPT is approximately 2.8% of the cost of photovoltaic panels with a peak power rating of 154 W. The integrated MPPT also consumes no stored energy at night.

Solar power generation inverter device

Abstract: PROBLEM TO BE SOLVED: To improve the use efficiency of power at the time of independent operation and low output linking operation by stably executing the maximum power point tracking control in spite of the large change of sunshine. SOLUTION: A controller 19 receives a limit signal from a limit circuit 60 and limits a reference current value ID1* in the case of VD2L*

An artificial neural network-based real time maximum power tracking controller for connecting a PV system to the grid

Abstract: This work deals with the application of a neural network-based controller for tracking the point of maximum power of a photovoltaic (PV) system interconnected to the utility grid. The neural network is used to identify, in real time, the voltage for maximum output power of the system. The controller, through the information supplied by the neural network, generates a control signal that will be applied to a DC/DC (boost) converter in such a way to take the voltage of the system to a value which guarantees the operation of the PV system at maximum power. The boost converter duty-cycle is generated by a PI controller based on the information supplied by the neural network. In order to connect the PV system to the electric distribution system a three-phase voltage source inverter (VSI) is used operating with optimized sinusoidal PWM strategy with harmonics elimination at the output voltage up to the 17/sup th/ harmonic. The inverter uses IGBT as power switches, and is microcontroller operated.

Wind turbine power converters: a comparative study

Abstract: Two of the most promising types of power converter applicable to the task of interfacing variable-voltage DC energy sources to the grid are compared. The converters studied are first a DC/DC power converter with a current-controlled voltage source inverter and, secondly, the line-commutated SCR with an active compensator for reduction of harmonic current and reactive power demand. The comparison is drawn with particular reference to use with variable-speed permanent-magnet wind turbine generators. The optimal power transfer, reactive power/voltage regulation and harmonic minimisation are addressed. Experimental results from laboratory models are presented alongside simulation results, which are in good agreement, to demonstrate the power control and harmonic performance of these systems. Power losses and semiconductor costs are also discussed.

Parallel operation system of solar-generating inverter

Abstract: PROBLEM TO BE SOLVED: To attain easy setting, simplification and high reliability of individual inverters, low cost and high reliability of a whole system, and easy reading of the output for the whole system. SOLUTION: This system converts a DC power generated by a solar battery 1 into AC power and feeds linkedly it to a commercial power system 2. The system is provided with a plurality of inverters 4 which are operated in parallel and a controller 5 controlling a plurality of inverters 4. The controller 5 is equipped with a means of detecting the conditions of feeding of a plurality of inverters 4 and the commercial power system, a means of generating parallel operational control signals of the respective inverters according to the conditions detected by the means, and a means of generating the display signal of the output power. The system is also provided with a display 6 displaying the output power by a signal to be outputted from the controller 5.

Controller for solar electric generator for recreational vehicles

Abstract: A controller for a solar electric generator that permits the generator to produce power substantially at its maximum capacity. Power is transferred from the generator to a temporary electric storage device that is periodically partially drained of power to maintain the temporary electric storage device at a voltage corresponding to the voltage needed by the generator to provide maximum generator power. The electric power drained from the temporary storage device is used to charge conventional batteries. In a preferred embodiment, the temporary storage device is a capacitor that is part of a buck regulator operating at 50 kHz with duty factor control between 0% and 100%. This buck topology switching type regulator provides the periodic draining. In the preferred embodiment control of the duty factor of the buck regulator is utilized to limit current, to prevent battery over charging, to test for the voltage corresponding to maximum power, and to operate the solar generator at is maximum power voltage. When operated at its maximum power operating point, the output to the battery is constant power, providing greater battery charge current than prior art controllers.

Power conversion device for photovoltaic generation

Abstract: PROBLEM TO BE SOLVED: To improve the efficiency of system generation in a system linkage inverter which has input from a plurality of solar cell arrays connected in parallel, by causing the individual solar cell arrays to independently follow maximum power. SOLUTION: In a power conversion device for photovoltaic generation having a plurality of solar cell modules 8a, 8b, 8c as power sources, each of the solar cell modules 8a, 8b, 8c is provided with step-up chopper portions 26a, 26b, 26c which follow the maximum power of the individual solar cell modules 8a, 8b, 8c, and a DC-DC converter for waveform generating portions. Maximum power is derived from respective solar cell modules 8a, 8b, 8c and is converted into an alternating-current output through a inverter 23, a DC-AC converter 36, and the like in a bundle. COPYRIGHT: (C)1999,JPO

Wind speed estimation based variable speed wind power generation

Abstract: Significant variation of the resource kinetic energy, in the form of wind speed, results in a substantially reduced energy capture in a fixed speed wind turbine. In order to increase the wind energy capture in the turbine, variable speed generation (VSG) strategies have been proposed and implemented. Typically, VSG strategies vary the rotational speed of the turbine, by controlling either a mechanical or electrical parameter to maintain a constant tip-speed ratio of the turbine. This is known as a maximum power point tracking (MPPT) controller. Traditionally, the MPPT controller is based upon a simple, but slow, search or perturbation algorithm to determine the optimal rotational speed of operation. In this paper, a wind speed estimation-based MPPT algorithm is proposed that employs a heuristic model of both the turbine and the generator to estimate the wind speed. A local search/perturbation of the rotational speed is employed to attain fine tuning of the desired optimal tip-speed ratio tracking. While this algorithm is more complicated than the search based method, it can still be implemented inexpensively. The ease of implementation guarantees fast control updates and ensures maximum power point operation for all wind speeds within the design limitations. The controller has been verified for efficacy on a 1.5 kW laboratory VSG wind generator.

Single phase to three phase converter

Abstract: A converter for providing three phase power to a three phase load from a single phase supply includes an inverter connected to single phase input power lines and a bi-directional switch connected in series with one of the input power lines. The converter has three output lines, one connected to the inverter output, another connected to an input power line between the bi-directional switch and the inverter, and the third connected directly to the other input power line. The inverter switching devices are controlled to provide a signal on the output of the inverter to provide balanced three phase power on the converter output lines. This is preferably accomplished by pulse width modulation of an inverter output voltage reference signal derived by phase shifting the single phase input voltage signal by 60°. The inverter is preferably also controlled to phase shift the inverter output signal when necessary to ensure that the net power flow into the inverter is zero under light load conditions. During load start-up, the bi-directional switch is phase controlled to adjust the amplitude of the converter output current to thereby adjust the load current to limit inrush current levels and provide a soft starter by ramping up the current in the load.

Development of a low-cost integrated 20-kW-AC solar tracking subarray for grid-connected PV power system applications. Final technical report

Abstract: This report chronicles Utility Power Group's (UPG) successful two-year Photovoltaic Manufacturing Technology (PVMaT) Phase 4A1 work effort which began in July, 1995. During this period, UPG completed design, fabrication, testing and demonstration of a modular and fully integrated 15-kW-ac, solar tracking PV power system sub-array. The two key and innovative components which were developed are a Modular Panel which optimizes factory assembly of PV modules into a large area, field-deployable, structurally-integrated PV panel, and an Integrated Power Processing Unit which combines all dc and ac power collection, conversion and control functions within a single, field-deployable structurally-integrated electrical enclosure. These two key sub-array elements, when combined with a number of other electrical, mechanical, and structural components, create a low-cost and high-performance PV power system. This system, or sub-array, can be deployed in individual units, or paralleled with any number of other sub-arrays, to construct multi-megawatt P fields. 21 figs.

Developed Algorithm of Maximum Power Tracking for Stand-Alone Photovoltaic System

Abstract: The rapid increase in the cost of conventional energy sources leads to the use of nonconventional energy sources. The photovoltaic (PV) is one nonconventional source that is safe, reliable, and environmentally healthy. However, the PV system is expensive and needs a large area to operate. To solve these disadvantages, it is necessary to operate at the maximum power point (MPP) of the array. This article presents a new maximum power tracking algorithm based on the incremental conductance algorithm, which successfully operates even in cases of rapidly changing atmospheric conditions. The developed algorithm depends on the relationship between the load line and the tangent line angles of the I-V characteristic curve. A simulation program was designed to investigate the performance of the developed algorithm using mathematical models for the different system components. The simulation led to a good realization of the algorithm.

Single-stage converters for photovoltaic powered lighting systems with MPPT and charging features

Abstract: This paper proposes single-stage power converters (SSCs) for application in photovoltaic powered lighting systems. The synchronous switch technique is employed to synthesize the SSCs which can fulfill maximum power point tracking, battery charging, discharging and lamp ballasting features. Several typical SSCs are discussed in the paper. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed. Both pulse-width modulation and variable-frequency controls are used to govern the system. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has the merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems.

Photovoltaic power generation apparatus

Abstract: A solar cell array used in a photovoltaic power generation apparatus for housing covers a relatively large outside area for installation, and a considerably large earth capacitance Ca exists between the solar cell array and the ground. Further, as an inverter for converting direct-current electric power generated by the solar cell array into alternating-current electric power, a transless-type inverter is used for reducing cost. Therefore, a slight leak current flows via the earth capacitance Ca, which may cause undesirable operation of an earth leakage circuit breaker inserted between the inverter and a commercial AC power system. In the photovoltaic power generation apparatus of the present invention, by designing it so that the relationship between the earth capacitance Ca[μF] and leak current detection sensitivity EL[mA] of the earth leakage circuit breaker is Ca

Neutral point connected apparatus providing compensation to an AC power line

Abstract: Apparatus for injection voltage compensation in series into an electric power line includes an inverter (3) or other controlled voltage source which wye connects the secondary windings (13a, b, c) of a three-phase transformer (11) to the load end (9) of the electric power line. The transformer, which could already be present for meeting load requirements, has its primary winding (15a, b, c) connected to the source end (5) of the electric power line and sustains the saturation currents rather than the inverter in response to faults on the source side of the transformer. Preferably, a three-phase inverter with a common dc link is used. For active power line conditioner (APLC) action, a second, also preferably a three-phase, inverter is connected in parallel to the load end of the electric power line and to the common dc link. This parallel inverter provides harmonic and reactive power compensation and also supplies the real power requirements of the wye connection inverter.

A novel utility interactive photovoltaic inverter with generation control circuit

Abstract: This paper describes a novel utility interactive photovoltaic inverter. Since photovoltaic modules in photovoltaic power generation systems in urban areas are installed on roofs, shadows created by neighboring homes, utility poles, and trees may sometimes cover some part of the photovoltaic modules. In this case, power generated from each photovoltaic module becomes unbalanced and its total generation power is greatly decreased, especially when the photovoltaic modules are connected in series. These problems cannot be solved in conventional systems. We developed a novel utility interactive inverter with generation control circuit. In this proposed inverter system, each of these photovoltaic modules is individually operated at its corresponding maximum power point. By using this inverter, the efficiency of the photovoltaic system can be improved.

A PV dispersed generator: a power quality analysis within the IEEE 519

Abstract: It is envisaged that the use of environmentally clean photovoltaic (PV) dispersed generation will become more widespread in the near future due to advances in PV technology which will lead to cost reductions. This paper summarizes the results of a power quality study performed on a rural distribution feeder having a PV generator and nonlinear loads in order to understand the effects that inverter-interfaced PV dispersed generation have upon the quality of electric power. Different interpretations for the harmonic distortion limits set in the IEEE 519-1992 standard are considered. This paper also includes a statistical analysis of all measurements recorded with the help of two power quality monitors, an evaluation of the results from a connection/disconnection test, and harmonies simulation results.