Showing papers on "Maximum power principle published in 1983"

Maximum power transfer system for a solar cell array

Abstract: A system for transferring maximum power from a solar cell array by loading the array in a manner which forces it to operate at its maximum power point. The system samples the open circuit voltage of the solar cell array to provide a signal proportional to the voltage of the array at its maximum power point. The sampled open circuit voltage is compared to the operating voltage of the solar cell array to provide an error signal which is proportional to the difference between the maximum power point voltage and the operating voltage of the array. The amount of power transferred from the array to a load is altered in accordance with the error signal to operate the array at its maximum power point.

An Analytic Approach to Optimum Oscillator Design Using S-Parameters

Abstract: An analytic approach to the design of microwave FET oscillators for maximum power output into a given load is presented. By the use of FET S-parameters, characterized as a function of incident input powers, design information can he obtained for any standard topology. By means of this technique, an experimental 5.3-GHz oscillator has been demonstrated which delivers 245 mW at 35-percent efficiency into a 50-Omega load.

Sun tracking by peak power positioning for photovoltaic concentrator arrays

Abstract: This paper details the design, development, and evaluation of a microcomputer-based solar tracking and control system (TACS) capable of maintaining the peak power position of a photovoltaic (PV) array by adjusting the load on the array for maximum efficiency and changing the position of the array relative to the sun. At large PV array system installations, inverters are used to convert the dc electrical output to ac for power grid compatibility. Adjustment of the inverter or load for maximum array output is one function performed by the tracking and control system. Another important function of the system is the tracking of the sun, often a necessity for concentrating arrays. The TACS also minimizes several other problems associated with conventional shadow-band sun trackers such as their susceptibility to dust and dirt that may cause drift in solar alignment. It also minimizes effects of structural warpage or sag to which large arrays may be subject during the day. Array positioning is controlled by a single-board computer used with a specially designed input/output board. An orderly method of stepped movements and the finding of new peak power points is implemented. This maximum power positioning concept was tested using a small two-axis tracking concentrator array. A real-time profile of the TACS activity was produced and the data analysis shows a deviation in maximum power of less than 1% during the day after accounting for other variations.

Nonlinear resistive maximum power theorem, with solar cell application

Abstract: This paper reports a multiport maximum power theorem for nonlinear resistive networks. The optimal nonlinear load characteristic is specified as a closed-form expression involving the constitutive relation of the source. An application to the optimal load-matching problem for a solar cell is given.

Method and apparatus for the automatic setting of the optimum operating point of a d-c voltage source

Abstract: Solar generators, fuel cells and similar d-c voltage sources have a current-voltage characteristic, on which at one point ("maximum power point" MPP) the maximum power can be taken from the d-c voltage source In an arrangement, in which a d-c voltage source feeds a consumer through a controllable power converter, the optimum operating point is automatically set by setting a reference value for the voltage or the current into the converter, and impressing a supplemental reference value temporarily thereon as a disturbance variable at certain time intervals If due to the impression, the output power of the d-c voltage source increases, the reference value is adjusted in the direction of the supplemental reference value If, on the other hand, the sign of the power change is negative, the reference value is changed opposite to the sign of the supplemental reference value After a finite number of reference value changes, the instantaneous operating point is this brought to the optimum operating point Since the sign of the power change is determined through evaluation of the derivative with respect to time of the actual power value, the amplitude of the disturbance variable can be chosen very small, so that the operation of the consumer is not impaired

Maximum power tracking

Abstract: By definition, a maximum power tracking device causes the photovoltaic array to operate on the locus of maximum power points within a specified accuracy. There are limitations to the application of maximum power tracking. A prerequisite is that the load be capable of absorbing all of the power availble at all times. Battery chargers, electrical heaters, water pumps, and most significantly, returning power to the utility grid, are prime examples of applications that are adaptable to maximum power tracking. Maximum power tracking is available to either dc or ac loads. An inverter equipped with a means of changing input voltage by controlling its input impedance can deliver maximum power to ac loads. The inverter can be fixed or variable frequency and fixed or variable voltage, but must be compatible with the ac load. The discussion includes applications, techniques, and cost factors.

Nonlinear Dynamic Maximum Power Theorem, with Numerical Method

Abstract: This paper considers the problem of maximizing the energy or average power transfer from a nonlinear dynamic n-port source. The main theorem includes as special cases the standard linear result Yload = Y*source and a recent finding for nonlinear resistive networks. An operator equation for the optimal output voltage 9(.) is derived, and a numerical method for solving it is given.

On the optimization of computer network power

Abstract: We study the tradeoff between throughput and delay involving the selection of a suitable operating point for a computer network. We choose to analyze this tradeoff through the maximization of various throughput-delay performance measures, all known as power. The models we analyze for the most part are those for a terrestrial wire network. We begin by analyzing power for simple computer networks. Although these networks are topologically simple, they also yield single-variable optimization problems which are mathematically simple. We concentrate on a critical system parameter, the average number in system at maximum power, since it is a parameter which is easily implemented in networks which use window flow control, and also because it exhibits important invariances. We next analyze a network which is topologically simple but which no longer has a simple problem formulation. We find that some of the nice results obtained for the simple formulations do not hold for this more complicated multi-variable problem. In particular, issues involving fairness of operating points are explored. We then extend the power problem in several ways. First the problem formulation itself is altered (the constraints and/or decision variables); second the objective function (the power function) is changed. We find with these extensions, that the multi-variable problem is often manageable. We also study a generalized power performance measure, which enables the analyst to vary the importance of throughput relative to delay, for the above problem formulations. Finally the analysis of power is extended to networks with blocking. Tradeoffs among throughput, delay and the blocking probability are examined.

Maximum power penetration through an electrically small aperture

Abstract: The maximum transmission cross section of an electrically small aperture reported by Harrington is derived from a power conservation law.

Dynamic simulation of dispersed grid-connected photovoltaic power systems: Task 1 - modelling and control

Abstract: For purposes of analysis and investigation, four power conditioning subsystems were selected as representative of photovoltaic systems. Two of these systems were single phase arrangements with power levels (5 to 10 kW) in the range of residential applications. The other two were three phase systems representative of power levels of 250 kW to several megawatts. Each system included an array, an inverter with control circuitry, and harmonic filters. Each system was assumed to be connected to a simplified equivalent of a power system. The first objective was to provide detailed representations of each of the four systems by simulating each of the systems on the hybrid computer at Purdue. The array was simulated using an aggregate model determined from digital computer studies of series and parallel strings of non-identical cells. These aggregation studies revealed that the Turfler aggregate model was sufficient to provide an adequate representation of a large array. The converters were simulated in enough detail to portray the switching of each valve within the converter. The primary control (cosine comparator for phase locked oscillator) was also simulated in detail. The secondary control for each converter was a voltage control. Computer traces are given that show the steady-state performancemore » of each of the converter systems. Next, the peak power tracking controls were incorporated into the simulation. These controls adjust the array voltage so that maximum power conversion is achieved for the given atmospheric conditions. A new method employing an incremental conductance measurement in the peak power tracking was developed. The start-up characteristics and the response of the converter systems during cloud cover transients were investigated using pilot cells and the incremental conductance methods. The systems responded in a satisfactory manner with no indication of instability due to control interaction.« less

Apparatus for determining the power available from a solar generator

Abstract: To enable the power, which is dependent upon the isolation at any time, to be determined directly, an apparatus is proposed which is provided with means for so loading the solar generator during a measurement e.g. to the left of load line R that the solar generator operates on a working point at which the generator voltage is less than the voltage at the working point for maximum power MPP, and a measuring system for measuring the current flowing during loading.

Apparatus for automatically tracking the optimum working point of a D.C. voltage source

Abstract: Solar generators, fuel cells and similar DC voltage sources have a current / voltage characteristic, is on a point ( "Maximum Power Point" MPP) distinguished by the fact that there can be taken from the DC voltage source, the maximum power. In an arrangement in which the DC power source 1 via a controllable power transformer, for. B. a interposing CTs 2 feeds a load 3, the optimum operating point is set automatically in that the transducer, a desired value U Takes as a result of the barge, the power output of the DC voltage source, the reference value U Is the sign of the power change is negative, then the target value is opposite to the sign of the additional setpoint changed. Characterized that the current operating point is in each case corrected to the optimum operating point according to a finite number of setpoint changes is achieved. Since the sign of the power change is detected by evaluating the time derivative of the Leistungsistwertes (differentiator 17) Storgrosenamplitude AU can be made very small ', so that the operation of the consumer is not impaired.

The performance of simple horizontal axis wind-turbines for the direct drive of water pumps

Abstract: Two turbine types were considered. Interest in both types, Cretian compliant-sail bladed machines and turbines with multiple flat slats as blades, has recently been revived, in developing nations, for water pumping applications. The work was based on wind-tunnel tests the results of which are presented in the form of power and torque coefficients versus velocity ratio. It was shown that a Cretian turbine can attain a maximum power coefficient of approximately 0.28 and also achieve a high starting torque. It was also found that optimised slatted wind-turbines are limited to maximum power coefficients of 0.19 to 0.23 depending upon their construction. The present results were combined with those of an earlier paper to yield what is believed to be a comprehensive summary map of the operational characteristics of optimised horizontal axis wind-turbines for the direct drive of water pumps.

Optimal Flux Distribution in Slab Reactors with Uniform External Source

Abstract: The problem of optimal flux distribution for maximum power, in bare slab reactors with uniform external source and maximum flux constraint, is solved using optimal control for-malism for the case of one group neutron diffusion approximation. A set of optimal solu-tions, which depend on the magnitude of the external source, the upper and lower limit of the control variable and the maximum flux allowable in the reactor, is obtained. The results corresponding to a critical reactor are included here, as a particular case. A numerical example is used to illustrate the parametric dependence of the solutions.