Showing papers on "Maximum power principle published in 1993"
TL;DR: It is concluded that the various forms and uses of energy bound up in essential ecosystem processes present a formidable obstacle to obtaining an operational definition of a general, aggregated available-work concept, a prerequisite for the systems approach of Odum and others.
Abstract: The central role of energy in all life processes has led to the development of numerous hypotheses, conjectures and theories on the relationships between thermodynamics and ecological processes. In this paper we examine the theoretical and empirical support for these developments, and in particular for the widely published set of thermodynamic conjectures developed by H.T. Odum, in which the maximum power principle is put forward as a generic feature of evolution in ecosystems. Although they are widely used, we argue that many of the ecological studies that have adopted the ideas encapsulated in Odum's work have done so without being aware of some of the fundamental problems underlying this approach. We discuss alternative ways in which a general available-work concept could be constructed for use as a numeraire in an energy-centered ecological theory or paradigm. In so doing, we examine what is meant by material accessibility and energy stocks and flows with respect to traditional food web and food chain theories, and relate these to results from the evolutionary dynamics of ecosystems. We conclude that the various forms and uses of energy bound up in essential ecosystem processes present a formidable obstacle to obtaining an operational definition of a general, aggregated available-work concept, a prerequisite for the systems approach of Odum and others. We also show that the prototypical derivations of the maximum power principle, and its interpretation, are contradicted on many scales both by empirical data and models, thereby invalidating the maximum power principle as a general principle of ecological evolution. The conclusions point to the fundamental problem of trying to describe ecosystems in a framework which has a one-dimensional currency.
109 citations
TL;DR: In this article, the authors calculate the efficiency of an endoreversible Carnot-type cycle in the maximum power regime by using a nonlinear heat transfer law (the so-called Dulong and Petit's law of cooling).
Abstract: We calculate the efficiency of an endoreversible Carnot‐type cycle in the maximum power regime by using a nonlinear heat transfer law (the so‐called Dulong and Petit’s law of cooling). The results obtained from this model compare well (around 99% in some cases) with observed efficiencies for several power plants. The considered law of cooling includes conductive‐ convective and radiative contributions to the heat exchange between the working fluid and its surroundings. Our calculations improve considerably those obtained by means of a linear heat transfer law for the same power sources. We also analyze a nuclear power plant using an ecological optimization criterion for finite‐time heat engines.
87 citations
TL;DR: In this paper, a numerical technique is presented to evaluate the maximum power that can be absorbed from a linear three-dimensional multi-degree-of-freedom system, where a weighted global constraint is imposed on the system's excursions to ensure that the assumptions of linear theory remain valid.
79 citations
Patent•
29 Jul 1993
TL;DR: In this paper, the MPP is determined by measuring the short circuit current, measuring the idle voltage and comparing the characteristics by means of the computer control, preferably an SPS, and the dynamic load impedance of the load is set by pulse width modulation by the control signal output by the SPS and thus the maximum power is taken from the solar module.
Abstract: The invention relates to the use of maximum power point regulation for the optimum operation of photovoltaic solar systems. According to the invention, the MPP is determined by measuring the short circuit current, measuring the idle voltage and comparing the characteristics by means of the computer control, preferably an SPS, and the dynamic load impedance of the load is set by pulse width modulation by means of a control signal output by the SPS and thus the maximum power is taken from the solar module.
43 citations
TL;DR: In this article, the design parameters of a heat engine operating under radiative heat transfer conditions were examined to find the maximum power output, and it was found that the ratio of the cold to the hot reservoir temperature must be less than 0.2 for an optimal design.
37 citations
TL;DR: The central-limit current distribution control for the system is incorporated in this control scheme to improve the system efficiency and reliability by uniformly distributing the total peak power among the converters connected in parallel.
Abstract: A control scheme for parallel connected converter systems that will transfer the maximum available power from a nonideal voltage source is presented. Monitoring the rates of change in both the average input current and average input power from the source in each switching period, the proposed control method can dynamically regulate the DC-DC converter system to track the peak power of the source. The amplitude and frequency of the oscillation due to a limit-cycle around the system peak power point is analyzed. In addition, the central-limit current distribution control for the system is incorporated in this control scheme to improve the system efficiency and reliability by uniformly distributing the total peak power among the converters connected in parallel. >
33 citations
10 May 1993
TL;DR: A new low-cost, simplified control strategy, based on the positive feedback of the output current in a maximum power point tracking (MPPT) converter, is introduced, which reduces the energy cost of renewable energy generators by optimizing the utilization of the renewable energy source.
Abstract: A new low-cost, simplified control strategy, based on the positive feedback of the output current in a maximum power point tracking (MPPT) converter, is introduced. Cost effective MPPT reduces the energy cost of renewable energy generators by optimizing the utilization of the renewable energy source. Maximum power point tracking for relative small photovoltaic (PV) power systems, with battery back-up, is achieved by employing this simplified positive feedback control strategy to maximize the output current into the battery. This new control strategy is analyzed and practical tested by using a buck power converter topology, but can also be used by the known converter topologies for PV systems and other renewable energy sources with a single power maximum. Experimental verification on the operation of this controller is included. >
30 citations
TL;DR: In this paper, two types of engines are modelled, a reciprocating and a steady flow, with results obtained for maximum power output and efficiency at maximum power, and it is shown that the latter is the same for both kinds of engines but that the maximum value of power production is different.
Abstract: An endoreversible heat engine is an internally reversible and externally irreversible cyclic device which exchanges heat and power with its surroundings. Classical engineering thermodynamics is based on the concept of equilibrium. Time is not considered in the energy interactions between the heat engine and its environment. On the other hand, although rate of energy transfer is taught in heat transfer, the course does not cover heat engines. The finite-time thermodynamics is a newly developing field to fill in the gap between thermodynamics and heat transfer. Two types of engines are modelled in this paper—a reciprocating and a steady flow—with results obtained for maximum power output and efficiency at maximum power. It is shown that the latter is the same for both types of engines but that the maximum value of power production is different.
22 citations
TL;DR: In this article, the maximum power which can be lost by volume processes in a tokamak divertor has been calculated using energy balance arguments, and a simple 1D model is used for parallel heat conduction in the scrape-off layer.
Abstract: Using energy balance arguments, the maximum power which can be lost by volume processes in a tokamak divertor has been calculated. A simple 1D model is used for parallel heat conduction in the scrape-off layer. It is shown that when radiation is added to the power balance, solutions are often thermally unstable. Conduction remains a powerful loss mechanism for plasma temperature at the target greater than or equal to 10 eV. The maximum power which can be lost by radiation or other volume processes decreases with increasing plasma density, but increases with increasing input power. It is difficult to make the fractional power radiated exceed 50% for typical divertor parameters.
22 citations
01 Jan 1993
TL;DR: In this paper, a control scheme for parallel connected converter systems that will transfer the maximum available power from a nonideal voltage source is presented, which can dynamically regulate the DC-DC converter system to track the peak power of the source.
Abstract: A control scheme for parallel connected converter systems that will transfer the maximum available power from a nonideal voltage source is presented. Monitoring the rates of change in both the average input current and average input power from the source in each switching period, the proposed control method can dynamically regulate the DC-DC converter system to track the peak power of the source. The amplitude and frequency of the oscillation due to a limit-cycle around the system peak power point is analyzed. In addition, the central-limit current distribution control for the system is incorporated in this control scheme to improve the system efficiency and reliability by uniformly distributing the total peak power among the converters connected in parallel. >
20 citations
Patent•
14 Jul 1993
TL;DR: In this article, the maximum power point tracking control of a DC power source is performed regardless of the variance in voltage-current characteristic of the DC power sources like a solar battery.
Abstract: PURPOSE:To always take out a maximum power from a DC power source by satisfactorily performing the maximum power point tracking control regardless of the variance in voltage-current characteristic of the DC power source like a solar battery. CONSTITUTION:A CPU 48 outputs the waveform pattern read out from a ROM 49 to a D/A converter 51 to obtain a reference sine wave signal S11 and switches an FET bridge 36 through a PWM modulation circuit 43 and a gate drive circuit 42 to convert the DC power from a solar battery 32 to an AC power. A detected inverter output current IOUT is converted to a digital value by an A/D converter 47 and stored in a RAM 50. The CPU 48 compares the preceding output current value and the present, output current value with each other to discriminate whether the output current IOUT is increased or not. The amplitude changing direction of the reference sine wave signal S11 is kept if it is increased, but this direction is inverted if it is reduced, and the amplitude of the reference sine wave signal S11 is changed in the determined direction by one stage to perform the maximum power point tracking control of the solar battery 32.
Patent•
22 Jun 1993
TL;DR: In this article, a power control circuit converts DC power into voltage and currents regarding an output from a solar cell and increases output voltage up to a value corresponding to the maximum output power of the solar cell.
Abstract: PURPOSE:To utilize natural energy effectively by supplying an air conditioner with the maximum power of a solar cell from the solar cell and supplying a shortage power from a commercial system power supply when the power consumption of the air conditioner is larger than output power from the solar cell. CONSTITUTION:A power control circuit 1 converts DC power into voltage and currents regarding an output from a solar cell 2. The AC power of a commercial power supply 6 is transmitted over a VVVF inverter 7 through a voltage doubler rectifier circuit 4 in an inverter air conditioner 3, and a compressor 8 is driven in response to power from each circuit 1, 4 by the inverter 7. The power control circuit 1 has a followup value control section 21 for following the maximum point of output voltage from the solar cell, changes over an FET bridge 12 by a pulse signal at a duty ratio corresponding to an output from the followup value control section 21, when output voltage from the solar cell is smaller than the power consumption of the air conditioner, and increases output voltage from the power control circuit 1 up to a value corresponding to the maximum output power of the solar cell. When power consumption is larger than the maximum power of the solar cell, a shortage section is supplied from the commercial system power supply.
TL;DR: In this paper, the thermal efficiency of two different types of MHD-generator cycles operated at maximum power output is compared with the Curzon and Ahlborn efficiency, for electrical efficiency ηe approaching unity.
Patent•
22 Dec 1993
TL;DR: In this article, a method of controlling the application of power to a plurality of metering devices in a pesticide dispensing system was proposed, which permits operator controlled designation of row numbering, row-specific dispensing quantity of both seed and pesticide, and accurate records of starting and stopping times and locations.
Abstract: A method of controlling the application of power to a plurality of metering devices in a pesticide dispensing system permits operator controlled designation of row numbering, row-specific dispensing quantity of both seed and pesticide, and accurate records of starting and stopping times and locations. The method also permits operation of a large number of dispensing devices with a normal electrical system capacity by controlling the application or sequencing of power, the maximum power required by the system can be reduced at maximal speed and efficiency.
Patent•
15 Jul 1993
TL;DR: In this article, the authors propose to start fuel cell operation with a load optimized according to a cell condition by controlling the inside load with a cell voltage lower limit value and a cell current upper limit value previously inputted.
Abstract: PURPOSE:To start fuel cell operation with a load optimized according to a cell condition by controlling the inside load with a cell voltage lower limit value and a cell current upper limit value previously inputted. CONSTITUTION:When load temperature rise starts in starting operation, a signal to set a cell voltage lower limit value and a cell current upper limit value previously inputted in an operation control program in an inside load control circuit 5 is outputted from a controller 4. An inside load 3 is controlled according to the increase in cell current so as to keep cell voltage in the lower limit value until cell current reaches the upper limit value to supply the maximum power to the load in each moment. After cell current reached the upper limit value, the load 3 is controlled according to the increase in cell voltage so as to keep the cell current in the upper limit value to supply the maximum power generation amount to the load. The power is supplied to the optimized load from the staring of operation of the fuel cell.
TL;DR: In this article, a Banki wind turbine based on the classical hydraulic machines theory is proposed for water pumping and electricity generation, and a 1 × 1 m prototype is evaluated in real wind with and without a guiding vanes system.
Patent•
03 May 1993TL;DR: In this article, an angular power function is extracted from each power spectrum by quantifying optical power along lines originating at various angles from an origin of the power spectrum, and an optimum for the lithographic system is determined based upon the data extracted from the angular power functions.
Abstract: A method of determining a feature-forming variant, such as focus or exposure, for a lithographic system or the like includes Fourier processing that extracts a figure of merit. In a preferred embodiment, the lithographic system fabricates a series of formations of a single pattern. An optical image of each exposure is formed. A Fourier power spectrum is determined for each optical image. An angular power function is extracted from each power spectrum by quantifying optical power along lines originating at various angles from an origin of the power spectrum. With regard to axes of maximum power, the distribution of on-axes and off-axes power is quantified for each angular power function. An optimum for the lithographic system is determined based upon the data extracted from the angular power functions. Preferably, the extraction of an angular power function from the associated Fourier power spectrum is an averaging of the optical power along selected portions of the lines originating from the origin, thereby improving the signal-to-noise ratio.
Proceedings Article•
07 Dec 1993TL;DR: In this paper, a neural network is used to predict the maximum power drawn from PV modules, which is based on the environmental factors such as insolation, cell temperature, and so on.
Abstract: This paper presents an application of a neural network to the prediction of maximum power drawn from PV modules. The output power from the modules depends on the environmental factors such as insolation, cell temperature, and so on, therefore, accurate estimation of maximum power and continuous control are required to achieve maximum output efficiency. The proposed neural network has a simple structure resulting in highly accurate prediction of maximum power from the PV modules. >
Patent•
09 Sep 1993TL;DR: In this article, the maximum permissible power of rectifier is calculated as a time-varying value from data provided by heat sink and ambient temperature sensors 17, 14, which data together with stored rectifier characteristic data allow the actual rectifier junction temperature to be calculated.
Abstract: In a frequency converter system in which a rectifier unit 1 is connected to a DC bus 3 supplying inverters 6, eg. in a numerically-controlled machine having inverter-driven motors 7, prolonged overloads or short-term extreme load peaks in the rectifier 1 are prevented by determining the loading of the rectifier 1, that is the ratio of instantaneous to maximum permissible power of rectifier 1, to produce a loading signal A. If signal A indicates that rectifier 1 is overloaded, the power taken by certain, or all, of the inverters is reduced or also one inverter/motor unit 6, 7 can be operated as a generator. If the overload condition cannot be reduced within a maximum permitted time the motors 7 are stopped. The instantaneous power of rectifier 1 may be determined by input current sensors 15, or from signals A' indicating individual inverter powers. The maximum permissible power of rectifier 1 is calculated as a time-varying value from data provided by heat sink and ambient temperature sensors 17, 14, which data together with stored rectifier characteristic data allow the actual rectifier junction temperature to be calculated. The maximum permissible power is dependent on the difference between the actual junction temperature and the maximum junction temperature specified by the manufacturer. Switching frequency and DC bus 3 voltage may also be taken into account when determining maximum power. Trends may also be observed, so that if the power requirement shows a tendency to increase, before an overload actually occurs inverter control modules 5 may operate to prevent power drawn from rectifier 1 increasing further. A comparatively small rectifier can thus be operated continuously at its power limit.
TL;DR: In this article, the trade-off between the objectives of generating maximum power and minimizing the dynamic loads of a variable speed wind tumine operated below rated wind speed is investigated, and linear quadratic optimal control methods are used to investigate this balance.
TL;DR: In this paper, a methodology to predict solar cell/array power output based on the measurement of I sc, V oc and two points near P mp is presented, which eliminates the need for precise measurement of cell/string maximum power point.
Patent•
10 Dec 1993
TL;DR: In this article, the authors proposed a power-feeding algorithm to improve working efficiency of a power feeding equipment and reduce its cost by specifying relations among the maximum feeding power of one power supply unit and the total consuming power of loads and the number of the power supply units which are so interconnected that their loads are applied uniformly and in common to them.
Abstract: PURPOSE:To improve working efficiency of a power feeding equipment and reduce its cost, by specifying the relations among the maximum feeding power of one power supply unit and the total consuming power of loads and the number of the power supply units which are so interconnected that their loads are applied uniformly and in common to them. CONSTITUTION:In common to all base units of racks 1-4, power is fed via a power supply line 50 and a GND line 60 from the respective power supply units 22, 32, 41, 42. Since the respective power supply units 22, 32, 41, 42 are connected with each other via a current balancing line 70, uniform loads are applied respectively to the respective power supply units 22, 32, 41, 42, and uniform power is fed to them always. When denoting a necessary number of the power supply units, a maximum power feeding capacity of the one power supply unit, and a total load capacity by N, P, and Pt respectively, they are related to each other by an equation I. There, one of the power supply units is used as a backup power supply unit, and the first term of the right hand of the equation I is made to be an integer by a round-up. Since there are the errors caused by the variations of the base units, etc., when the number of the power supply units is M, the ratio Pm of the power, which can be fed actually to the one base unit, to the maximum power feeding capacity of the one power supply unit is determined by an equation II.
Patent•
03 Sep 1993
TL;DR: In this article, a series circuit of solar cells and an AC/DC converter in parallel with a battery and controlling the output voltage of the converter to maximize the power generation of the solar cells is discussed.
Abstract: PURPOSE:To enhance efficiency and to reduce cost and size of solar beam power generating facility by connecting a series circuit of solar cells and an AC/DC converter in parallel with a battery and controlling the output voltage of the converter to maximize power generation of solar cells thereby reducing the capacity of the converter. CONSTITUTION:Upon variation of terminal voltage VPV for generating maximum power due to variation of the cell temperature of solar cell 1, output voltage VAD from an AC/DC converter 2 is controlled at a control section 9 according to a climbing method, for example, so that the terminal voltage VPV has a level for maximizing power generation PPV. If power consumption PLOAD of a load 5 is higher than the sum of maximum power generation of the solar cells 1 and a generation PPV. If power consumption PLOAD of a load 5 is higher between the PLOAD and the sum of generated powers PPV, PAD, is supplemented by means of a battery 3 through an inverter 4. If the power PLOAD is lower than the sum of maximum power generation of the solar cells 1 and the generated power PAD, excessive power equal to the difference between the sum of generated powers PPV, PAD and the power PLOAD is fed to the battery 3.
TL;DR: In this article, a new method of the simulated power source (SPS) to analyze the PV system is proposed, which is under the control of the 10cm2 reference solar cell, so the output characteristics of the SPS is in proportion to the output of the reference solar cells not only static but dynamic.
Abstract: Numerous studies were performed so as to evaluate the performance of the photovoltaic power systems (PV systems), included maximum power control of the solar cell, effects of the PV systems on distribution feeders, long-term performance of the PV systems, etc. In order to estimate the performance of the PV systems, the output characteristics of the solar sell should be taken into consideration.In this paper, a new method of the simulated power source (SPS) to analyze the PV system is proposed. The SPS is under the control of the 10cm2 reference solar cell, so the output characteristics of the SPS is in proportion to the output characteristics of the reference solar cell not only static but dynamic.
Patent•
26 Nov 1993
TL;DR: In this paper, the authors proposed a solar power generation system which efficiently operates an inverter while performing the maximum power following-up control, which maximizes the generated power, in all of the period of power generating operation.
Abstract: PURPOSE:To provide the solar power generation system which efficiently operates an inverter while performing the maximum power following-up control, which maximizes the generated power, in all of the period of power generating operation. CONSTITUTION:This system is provided with a solar battery 1, plural inverters 2A and 2B which convert the output of the solar battery 1 to an AC to connect it to a power system 4, a controller 5 which performs the maximum power following-up control of the specific inverter 2A, and a controller 6A which allots the generated power outputted from the solar battery to respective inverters and controls the outputs of inverters so that the efficiency of the whole of the system is maximum.
Patent•
11 Jun 1993
TL;DR: In this article, the authors proposed a method to prevent the malfunction of a DTMF receiver by calculating the total power value and the maximum power value by an adder and a discriminator.
Abstract: PURPOSE:To prevent the malfunction of a DTMF receiver CONSTITUTION:The total power value and the maximum power value are calculated by an adder 1 which inputs the full power value related to the low group frequency calculated by a DTMF receiver and a maximum power discriminater 2 A power comparater 3 calculates the difference between both power values, and a discriminater 4 compares the calculated difference with the set threshold value and decides whether just a single frequency belongs to an input low group or not In the same way, an adder 5 and a maximum power discriminater 6 calculate the total power value and the maximum power value respectively in regard of the high group frequency Then a power comparator 7 calculates the difference between both values, and a discriminater 8 compares this difference with the set threshold value to discriminate whether just a single frequency belongs to an input high group or not If just a single frequency belongs to the input low and high groups respectively, a general discriminator 9 discriminates that an input signal is identical with a DTMF signal in regard of the low and high groups respectively
01 Jan 1993
TL;DR: In this paper, the power output of a simple, finite-time closed gas-turbine power plant is modeled and analyzed using a reversible Brayton cycle coupled to a heat source and a heat sink by heat transfer.
Abstract: The power output of a simple, finite-time closed gas-turbine power plant is modeled and analyzed. The model adopted is a reversible Brayton cycle coupled to a heat source and a heat sink by heat transfer. Both the heat source and the heat sink may have either finite or infinite heat-capacity rates. A mathematical expression is derived for the power output of the irreversible power plant. The maximum power output of the power plant is found by computer simulation. The maximum bound provides the basis for designing a real closed gas-turbine power plant and for a performance comparison with existing power plants
Patent•
01 Jul 1993
TL;DR: In this article, the authors proposed a variable heating power allocation to the individual boilers of a coffee machine, which can be used to dispense a large number of beverages even if the maximum available power is insufficient to supply all the heating elements at the same time.
Abstract: The device, especially a coffee machine, comprises three boilers (1, 2, 3) for heating water. To this end, in each boiler there is a heating element (10, 11, 12) which can be switched on and off by a switch (20, 21, 22) in a control device (16). There is also a temperature probe (13, 14, 15) in each boiler to measure the hot water temperature. In addition, the control device (16) has computing (17) and storage means (18, 19). Predetermined reference temperatures for the water in the individual boilers and the maximum power supply available for the coffee machine can be stored in the storage means (18, 19). The control device is laid out in such a way that, on the basis of the water temperature cycle in the individual boilers, heating power can be distributed to that boiler which needs it first owing to a certain priority. At the same time, it is ensured that the coffee machine can draw no more heating power than is available. This variable heating power allocation to the individual boilers thus makes it possible to dispense a large number of beverages even if the maximum available power is insufficient to supply all the heating elements at the same time. The heating power is allocated in the device of the invention depending on the power supply and the power requirement of the individual boilers.