Showing papers on "Maximum power principle published in 1998"
TL;DR: A simple method of tracking the maximum power points (MPPs) and forcing the system to operate close to these points is presented, and the principle of energy conservation is used to derive the large- and small-signal model and transfer function.
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.
746 citations
TL;DR: In this paper, a charge pump cell is used to make a voltage doubler using improved serial switches and a complete power efficiency theory is presented which fits the measurements, and the importance of capacitors is shown with plots of power efficiency versus load and stray capacitors.
Abstract: A charge pump cell is used to make a voltage doubler using improved serial switches. A complete power efficiency theory is presented which fits the measurements. The importance of capacitors is shown with plots of power efficiency versus load and stray capacitors. Several problems arising at low voltage or high frequency are developed and some optimizations are presented. The substrate current is totally suppressed by the technique of bulk commutation. A power efficiency of 95% has been reached using external capacitors. A fully integrated charge pump is also presented and shows a maximum power efficiency of 75%.
468 citations
TL;DR: A high-performance discrete MPPT controller that tracks the maximum power point with zero-slope regulation and current-mode control is presented and the DC-DC power converter is capable of combining with the BESS for performing the functions of power conditioning and active power filtering.
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.
421 citations
17 May 1998
TL;DR: In this article, 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, based on a digital signal processor (DSP) and the experimental results are presented.
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.
323 citations
15 Feb 1998
TL;DR: In this paper, 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).
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.
319 citations
Patent•
[...]
26 Nov 1998
TL;DR: In this paper, a solar array system is described with switches connected by switches to an output bus, and switches can be opened and closed so the system operates at its maximum power point.
Abstract: A solar array system is described having a solar array (31) divided into sections (33, 35, 37, 39) connected by switches (43, 45, 47, 49) to an output bus (51). The switches can be opened and closed so the system operates at its maximum power point. The system can be used, for example, to power satellites.
127 citations
TL;DR: It is shown that an iterative power control and base station assignment algorithm based on CIR measurements converges to a unique fixed point at a geometric rate, even if some or all of the users are subject to maximum power constraints.
Abstract: In wireless communication systems, mobile users adapt to a time varying radio channel by regulating transmitter powers. This power control is intended to provide each user an acceptable connection, as measured by a carrier to interference ratio (CIR), by eliminating unnecessary interference. It is important that a power control algorithm can converge quickly to a fixed point at which either all users have acceptable connections or an infeasibility can be detected. In this work, we show that an iterative power control and base station assignment algorithm based on CIR measurements converges to a unique fixed point at a geometric rate. This conclusion is shown to hold even if some or all of the users are subject to maximum power constraints. The rate of convergence is evaluated by simulation of a one dimensional CDMA system.
111 citations
TL;DR: In this article, finite-time thermodynamics has been applied to optimize the power output of closed Brayton cycles for infinite thermal capacitance rates of the heat reservoirs, and the optimum values of power, thermal efficiency and second-law efficiency of Brayton cycle are presented.
106 citations
07 Jul 1998
TL;DR: In this paper, the maximum power of a photovoltaic system changes with temperature, solar intensity and load, and an analytical model is built for the solar cell on the basis of the manufacturer characteristics.
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.
104 citations
TL;DR: In this article, the power density (the ratio of the power to the maximum specific volume in the cycle) is maximized for an Atkinson engine, and the results showed that the efficiency at maximum power density is always greater than that at maximum output power.
90 citations
21 Sep 1998
TL;DR: In this paper, a model-based method to predict the maximum power point (MPP) of a PV array using the measured data of radiation and temperature was proposed, which can be embedded in a synchronous rotating reference frame (SRRF) current regulator.
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.
TL;DR: In this article, the concept of maximum power for analyzing the power stability of single-infeed HVDC systems, is extended to the multi-infed HVDc situation.
Abstract: In this work, the well known concept of maximum power for analyzing the power stability of single-infeed HVDC systems, is extended to the multi-infeed HVDC situation. Based on this concept, two approaches to analyze the power stability of multi-infeed HVDC systems are derived. One approach uses the standard maximum power curve technique while the other uses an eigenvalue decomposition technique. These approaches are not equivalent, thus, comparisons between them and other power/voltage stability analysis methods are also made.
TL;DR: In this paper, a performance analysis based on the maximum power density criterion has been carried out for an irreversible regenerative reheating Joule-Brayton engine, and the obtained results were compared with those obtained using the conventional maximum power performance criterion.
Abstract: A performance analysis based on the maximum power density criterion has been carried out for an irreversible regenerative reheating Joule-Brayton engine. The obtained results were compared with those obtained using the maximum power performance criterion. The design parameters under the optimal conditions have been derived analytically and their effects on the engine's performance have been discussed. The overall effects of reheating, regeneration and internal irreversibilities are investigated. The obtained results may provide a general theoretical tool for the optimal design and operation of real non-regenerative and regenerative reheating gas turbines.
TL;DR: This paper proposes a novel approach to obtain a lower bound of the maximum power consumption using automatic test generation (ATG) technique and shows that this approach generates the lower bound with the quality which cannot be achieved using simulation-based techniques.
Abstract: Excessive instantaneous power consumption may reduce the reliability and performance of VLSI chips. Hence, to synthesize circuits with high reliability, it is imperative to efficiently obtain a precise estimation of the maximum power dissipation. However, due to the inherent input-pattern dependence of the problem, it is impractical to conduct an exhaustive search for circuits with a large number of primary inputs. Hence, the practical approach is to generate a tight lower bound and an upper bound for maximum power dissipation within a reasonable amount of central processing unit (CPU) time. In this paper, instead of using the traditional simulation-based techniques, we propose a novel approach to obtain a lower bound of the maximum power consumption using automatic test generation (ATG) technique, Experiments with MCNC and ISCAS-85 benchmark circuits show that our approach generates the lower bound with the quality which cannot be achieved using simulation-based techniques. In addition, a Monte Carlo-based technique to estimate maximum power dissipation is described. It not only serves as a comparison version for our ATG approach, but also generates a metric to measure the quality of a lower bound from a statistical point of view.
TL;DR: In this paper, a Maximum Power Point Tracker (MPPTT) using a step up converter with a current locked loop was developed, which showed an improvement in the output power by 22.5% (average) over a wide range of solar irradiation in a day.
TL;DR: In this article, the matching of separately excited dc motors to photovoltaic generators (PVG) for maximum power output is addressed. But the authors focus on the matching process of the motor to the generator and do not consider the effect of temperature on the I-V characteristic of the generator.
Patent•
30 Sep 1998
TL;DR: In this paper, each output of a solar battery group (for example, solar battery arrays 20A, 20B, and 20C) is follow-up controlled at the maximum power point in a DC state by a maximum powerpoint followup controlling means (DC/DC converter parts 3A, 3B, 3C, and converter control parts 4A, 4B, 4C) provided for each solar battery groups.
Abstract: PROBLEM TO BE SOLVED: To reduce the increase of manufacturing costs to the minimum, and to improve power conversion efficiency SOLUTION: Each output of a solar battery group (for example, solar battery arrays 20A, 20B, and 20C,) is follow-up controlled at the maximum power point in a DC state by a maximum power point follow-up controlling means (DC/DC converter control parts 3A, 3B, 3C, and converter control parts 4A, 4B, 4C,) provided for each solar battery group Then, the output of the maximum power point follow-up controlling means is converted into AC by a DC/AC converting means (invertor 5 and invertor controlling part 6) Thus, the maximum power can be precisely extracted for each solar battery group
Patent•
07 May 1998
TL;DR: In this article, the authors proposed a power conversion device for photovoltaic generation having a plurality of solar cell modules 8a, 8b, 8c as power sources.
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
TL;DR: In this paper, the performance of an isothermal chemical engine with finite-rate mass transfer and a mass leak is analyzed and the relation between the optimal power output and the efficiency is derived on the basis of linear (Onsager) mass transfer law using the analogous method of finite-time thermodynamics.
Abstract: The performance of an isothermal chemical engine with finite-rate mass transfer and a mass leak is analysed in this paper. The relations between the optimal power output and the efficiency, the maximum power output and the corresponding efficiency and the maximum efficiency and the corresponding power output are derived on the basis of linear (Onsager) mass-transfer law using the analogous method of finite-time thermodynamics for a heat engine. There exists a maximum efficiency bound with nonzero power output besides the maximum power output bound with nonzero efficiency for the engine. This characteristic is different from that for the chemical engine with the sole irreversibility of finite-rate mass transfer. The optimal region of parameter selection for the engine is provided and the effect of the mass-transfer law is analysed.
31 Aug 1998
TL;DR: In this article, 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, and a local search/perturbation of the rotational speed is employed to attain fine tuning of the desired optimal tip-speed ratio tracking.
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.
10 Aug 1998
TL;DR: This work proposes a new technique for generating a small set of patterns to estimate the maximum power supply noise of deep sub-micron designs using the Genetic Algorithm based on the efficient waveform simulator.
Abstract: We propose a new technique for generating a small set of patterns to estimate the maximum power supply noise of deep sub-micron designs. We first build the charge/discharge current and output voltage waveform libraries for each cell, taking power and ground pin characteristics, the power net RC and other input characteristics as parameters. Based on the cells' current and voltage libraries, the power supply noise of a 2-vector sequence can be estimated efficiently by a cell-level waveform simulator. We then apply the Genetic Algorithm based on the efficient waveform simulator to generate a small set of patterns producing high power supply noise. Finally, the results are validated by simulating the obtained patterns using a transistor level simulator. Our experimental results show that the patterns generated by our approach produce a tight lower bound on the maximum power supply noise.
Patent•
18 Sep 1998
TL;DR: In this paper, an apparatus for extracting maximum power from an energy source, such as a photo voltaic panel or a windmill, and delivering that power to a battery or an array of batteries is described.
Abstract: Apparatus and attendant methodology for extracting maximum power from an energy source, such as a photo voltaic panel, an array of photo voltaic panels, or a windmill and delivering that power to a battery or an array of batteries is disclosed. The apparatus determines the maximum operating point of the energy source, and circuits and circuit topologies are presented for extracting the energy. The apparatus eliminates the problem of finding local maximum points, and problems attendant variations of the absolute maximum power point as a function of temperature, insolation, array construction, and photo voltaic panel manufacturing tolerances. The energy source supplies power in the form of a voltage and charges the batteries with a controllable current source.
TL;DR: This paper describes a maximum power point tracking algorithm for a single-phase, grid-connected photovoltaic system with a transformerless, diode-clamped inverter and results show the superiority of the proposed algorithm.
TL;DR: In this paper, the authors presented a new maximum power tracking algorithm based on the incremental conductance algorithm, which successfully operates even in cases of rapidly changing atmospheric conditions. But, the performance of the developed algorithm depends on the relationship between the load line and the tangent line angles of the I-V characteristic curve.
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.
TL;DR: In this article, a scalar index called line-stability index for each line is calculated based on the power flow through the line, which can be used as a tool for system monitoring and future load planning.
Abstract: A simple but useful technique is proposed to study steady-state line outage and hence voltage collapse of the system. Voltage collapse prediction can be performed through the study of line outages, though techniques for nodal-based prediction or critical-node identification are frequently proposed. Experimentally, it was proven that both line outage and system voltage collapse take place simultaneously. In fact, line outages can be treated as the secondary cause of voltage collapse. A scalar index called line-stability index for each line is calculated based on the power flow through the line. The line-stability index may have a value that varies from zero (no power flows through the line) to one (maximum power flows through the line). Any line exceeding the maximum limit of stability index (1.00) can cause system-wide voltage collapse. The proposed technique is tested on a six-bus standard test system, and encouraging results are observed. The results obtained indicate that the technique has the potential to be used as a tool for system monitoring and future load planning.
01 Dec 1998
TL;DR: In this paper, a microcontroller based automatic sun tracker combined with a new solar energy conversion unit is designed and implemented, where the switching device of the chopper is not only used for power conversion but also for maximum power point (MPP) detection.
Abstract: A microcontroller based automatic sun tracker combined with a new solar energy conversion unit is designed and implemented. The automatic sun tracker is implemented with a DC motor and a DC motor controller. The solar energy conversion unit consists of an array of solar panels, a step-up chopper, a single-phase inverter, an AC mains power source and a microcontroller based control unit. The novelty of this unit is that the switching device of the chopper is not only used for power conversion but also for maximum power point (MPP) detection. In the existing MPP trackers, the MPP is detected by hardware. The parameters of the hardware subject to the changes of the environmental conditions. In the new unit the MPP is determined by simple embedded software with a current sweep approach. With this new approach, the modularization of the conversion from solar power to electric power at its maximum power point can be made more compact and more reliable.
07 Jul 1998
TL;DR: In this paper, the authors investigate the reasons for the status quo and seek acceptable solutions, both technically and economically, to find an optimal power point tracking method for low power applications.
Abstract: The cost of PV modules dictate that maximum use be made of the available power that can be produced. To achieve this goal, it is necessary to match the PV module characteristics with that of the load. Although this fact is not new, many charge regulation products and water pumping systems still operate on less than optimum principles. Especially, small systems (50-80 W) make use of direct coupling to the PV module or rely on fixed voltage operation. The purpose of this work is to investigate the reasons for the status quo and to seek acceptable solutions, both technically and economically. The need for extracting maximum power from a PV module is obvious. A cost-effective method, which is reliable, will make optimum power point tracking feasible, even for low power applications.
27 May 1998
TL;DR: In this article, the authors presented a novel approach to optimize pin array design of an integrated, liquid-cooled, insulated gate bipolar transistor (IGBT) power module with the aid of a computational fluid dynamics (CFD) code.
Abstract: This paper presents a novel approach to optimize pin array design of an integrated, liquid-cooled, insulated gate bipolar transistor (IGBT) power module. With the aid of a computational fluid dynamics (CFD) code, the fluid field and heat transfer inside the module were analyzed, and several design options for pin arrays were examined. For IGBT die circuitry, the uniformity of temperature distribution among the dies is as critical as the magnitude of the die temperature. A noticeable variation in temperature among dies can accelerate thermal runaway and reduce device reliability. With geometrically-optimized-pin designs located both upstream and downstream of the channel, a total power dissipation of 1200 W was achieved. The maximum junction temperature was maintained at /spl sim/100/spl deg/C and the maximum variation among dies was controlled to within 1/spl deg/C. The results from this study indicated that the device junction temperatures were not only reduced in magnitude but were also equalized. In addition, the maximum power dissipation of the module was enhanced. Comparison with other direct (pool boiling) and indirect (cold plate) liquid cooling techniques was also discussed.
TL;DR: In this paper, a fundamental analysis of the influence of load characteristics on the power/voltage stability of three typical HVDC system configurations is carried out in this two-part work.
Abstract: For pt.I see ibid., vol.13, no.4, p.1437-44 (1998). The influence of load characteristics on the power stability of a specific HVDC system configuration has been shown. This points to a more fundamental influence of load characteristics on the power/voltage stability of HVDC systems in general. Thus, a fundamental analysis of the influence of load characteristics on the power/voltage stability of three typical HVDC system configurations is carried out in this two-part work. Three aspects are treated; (i) the basic power/voltage stability equations incorporating load characteristics, the effect of load characteristics and system parameters; (ii) the relationships between the maximum power and voltage sensitivity based methods for all the configurations incorporating load characteristics; and (iii) the most unfavourable load characteristics with respect to degrading power/voltage stability margins and the sensitivity of these margins to load characteristics. This paper presents point (iii).
TL;DR: In this paper, a fundamental analysis of the influence of load characteristics on the power/voltage stability of three typical HVDC system configurations is carried out in two-part work.
Abstract: The influence of load characteristics on the power stability of a specific HVDC system configuration has been shown. This points to a more fundamental influence of load characteristics on the power/voltage stability of HVDC systems in general. Thus, a fundamental analysis of the influence of load characteristics on the power/voltage stability of three typical HVDC system configurations is carried out in this two-part work. Three aspects are treated; (i) the basic power/voltage stability equations incorporating load characteristics, the effect of load characteristics and system parameters; (ii) the relationships between the maximum power and voltage sensitivity based methods for all the configurations incorporating load characteristics; and (iii) the most unfavourable load characteristics with respect to degrading power/voltage stability margins and the sensitivity of these margins to load characteristics. This paper presents points (i) and (ii) while part II deals with point (iii).