Showing papers on "Power optimizer published in 1993"
20 Jun 1993
TL;DR: In this article, a flexible active and reactive power control strategy is developed, such that the optimal torque-speed profile of the turbine can be followed and overall reactive power can be controlled, while the machine copper losses have been minimized.
Abstract: Variable-speed constant-frequency generating systems are used in wind power, hydroelectric power, aerospace, and naval power generation applications to enhance efficiency and reduce friction. In these applications, an attractive candidate is the slip power recovery system comprising a doubly excited induction machine or doubly excited brushless reluctance machine and PWM power converters with a DC link. In this paper, a flexible active and reactive power control strategy is developed, such that the optimal torque-speed profile of the turbine can be followed and overall reactive power can be controlled, while the machine copper losses have been minimized. At the same time, harmonics injected into the power network have also been minimized. In this manner, the system can function as both a highly-efficient power generator and a flexible reactive power compensator. >
270 citations
Patent•
12 Jul 1993
TL;DR: In this article, a method and an apparatus for efficiently controlling the power output of a solar array string or a plurality of solar cell array strings to achieve a maximum amount of output power from the strings under varying conditions of use is presented.
Abstract: A method and an apparatus for efficiently controlling the power output of a solar cell array string or a plurality of solar cell array strings to achieve a maximum amount of output power from the strings under varying conditions of use. Maximum power output from a solar array string is achieved through control of a pulse width modulated DC/DC buck converter which transfers power from a solar array to a load or battery bus. The input voltage from the solar array to the converter is controlled by a pulse width modulation duty cycle, which in turn is controlled by a differential signal comparing the array voltage with a control voltage from a controller. By periodically adjusting the control voltage up or down by a small amount and comparing the power on the load or bus with that generated at different voltage values a maximum power output voltage may be obtained. The system is totally modular and additional solar array strings may be added to the system simply be adding converter boards to the system and changing some constants in the controller's control routines.
110 citations
Patent•
03 Sep 1993TL;DR: In this paper, a high power factor AC to DC converter with shunt regulation is described, where the first power converter receives and regulates input power from a power source and delivers a component of output power to a load.
Abstract: A high power factor AC to DC converter with shunt regulation include first and second power converters for converting AC power to DC power; the first power converter receives and regulates input power from a power source and delivers a component of an output power to a load. The second power converter delivers another component of the output power to the load. The first power converter includes a unidirectional power output connected to the load. The second power converter includes a bi-directional power input shunted across the load with a bi-directional power output connected to an energy storage apparatus for storing a difference between the input power and the output power components
44 citations
07 Mar 1993
TL;DR: In this paper, the authors considered the case of a three-phase to threephase quasi-direct power converters, and a simple and effective control technique suitable for this purpose, which also provided high power factor and small distortion of the supply currents, was described.
Abstract: The family of quasi-direct power converters, i.e. forced-commutated AC/DC/AC power converters including small energy storage devices in the DC link, is introduced. In particular, the case of a three-phase to three-phase quasi-direct converter is considered. Since energy storage minimization calls for instantaneous input/output power balance, a proper control strategy is needed. A simple and effective control technique suitable for this purpose, which also provides high power factor and small distortion of the supply currents, is described. The general properties of quasi-direct power converters are discussed, design criteria of both power and control sections are given, and experimental results of a 2 kVA prototype are reported. >
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
05 Sep 1993
TL;DR: The proposed converter is consisted of DC-Nx: modules whose inputs are connected in parallel and their outputs in series with a control scheme that ensures input current sharing among the modules and requlated output voltage.
Abstract: In this paper the author intends to present and analyze a modular Dc-Dc converter for high output voltage applications. The proposed converter is consisted of DC-Nx: modules whose inputs are connected in parallel and their outputs in series with a control scheme that ensures input current sharing among the modules and requlated output voltage . Moreover, it utilizes single feedback voltage sensing that achieves almost equal output voltage sharing among the modules. List of symbols C = output filter capacitance of one DC-DC module d = the AC part of the duty cycle D a duty cycle Gi = gain of the current sensing amplifier = N / 3 x R s G = gain of the modulator = d/v = Ad/Av = inpul current of one module I n CT i = AC part of the output filter inductor current I = input current of the DC-DC converter system k = the number of DC-DC modules L = output filter inductance of one DC-DC module N = number of turns of the power transformer primary winding N = number of turns of the power transformer secondary winding Paper APT 138-11-28 accepted for presentation at the IEEE/NTUA Athens Power Tech Conference: "Planning, Operation arid Control of Today's Electric Power Systems", Athens, Greece, Sept. 5-8,1993. N = turns ratio of the current sampling transformer P = output power of the DC-DC converter system T. = current loop gain T V = voltage loop gain T = transfer function of the voltage error amplifier R = load resistance of the converter system R = output filter capacitor ESR of one DC-DC module R = output filter inductor ESR of one DC-DC module R = resistance of current sensing network ,s v = AC part of control voltage V ,= output voltage of the DC-DC converter system ,o v = AC part of the converter system output voltage Vo,&= output voltage of one module V = input voltage of the D€-DC converter system ,s v = AC part of input voltage a = power transformer turns ratio = N / N 2 1 q = overall efficiency of the DC-DC converter qd= efficiency of one module w = frequency of the modulator w = frequency of the voltage error amplifier pole w = frequency of the voltage error amplifier zero w ' = frequency of the voltage error amplifier zero when CT
19 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.
18 citations
14 Sep 1993
TL;DR: The paper presents simulation and implementation of a photovoltaic fuzzy logic tracking controller that shows a satisfactory performance with almost an agreement between the simulation and experimental results.
Abstract: The paper presents simulation and implementation of a photovoltaic fuzzy logic tracking controller. The purpose is to track the maximum available solar power in a photovoltaic array interfaced to an electric utility grid via a line-commutated inverter. The scheme shows a satisfactory performance with almost an agreement between the simulation and experimental results. >
12 citations
07 Mar 1993
TL;DR: A survey of key original equipment manufacturer (OEM) specifiers of power supplies reveals a number of changing power supply requirements as discussed by the authors, in particular, purchasers of AD/DC switchers are tending to add power factor correction and universal input voltages.
Abstract: A survey of key original equipment manufacturer (OEM) specifiers of power supplies reveals a number of changing power supply requirements. In particular, purchasers of AD/DC switchers are tending to add power factor correction and universal input voltages. There will be growing demand for 3.3 V outputs, and power requirements will generally move in a downward direction. DC/DC converter specifiers plan sharp increases in distributed power usage, and also expect to buy more high density, high frequency converters. Power rating will generally show an upward trend, along with more widespread demand for DC/DC converters with 3.3 V outputs for use in portable computers. >
8 citations
05 Sep 1993
TL;DR: In this article, a variety of control modes which have been developed to operate wind turbines are compared in terms of energy capture, engineeritig implications at different levels of wind speed boundaries.
Abstract: t ~ l s i i i l t i i ~ i . I O ope~ate ;it i i ~ i l ~ i ~ l i ~ ~ t i l coiiversiori cfficieticy at d l witid speeds tcqitiies the wiiid turbine to operate at vwinble slmxl. Motlerti wi i id turbines begiti to operate :ik ;I clit-in wincl sliecd. When the rntcd wirid spcetl is rc:iclictI (lie titrl>irie has to be corirrollccl so rl int tlic cxccss c‘iictg i i i the wind is shed. Filiiilly ;it it cut-out wii ic l :,pcecl the turbine is shut clo~vi~. ‘ l l ~ paper (liscu choice of cii ti n , ratcd ;i iid c ut-oil t wi tic1 \I)eecis atid the variety of control modes which Iiiivc beeti developed to opcrn~e wind tiit bines wiiliiri iliese wind speed boundaries. ‘I’he coritrol tiiocles ate compared in terms of energy capture, engineeritig implications atid ~i~echa~iiciil stresses 01’1 the syste111. r ,
01 Jun 1993
TL;DR: A fourth order step-down power converter is treated as an example of how to survey a given circuit to decide whether a given topology is interesting for realization.
Abstract: A fourth order step-down power converter is treated as an example of how to survey a given circuit to decide whether a given topology is interesting for realization. An idealized power converter model is then established in which continuous operation mode and ideal devices are assumed. >
19 Oct 1993
TL;DR: An economic three-phase AC/DC power converter that possesses bidirectional power flow capability and a mathematical model of the power converter and a critical inductance condition are derived for simulation and design.
Abstract: An economic three-phase AC/DC power converter is proposed. The proposed converter uses only four active switches to simplify the hardware circuit and reduce the cost. In addition to the characteristics of unity power factor and sinusoidal input current waveform, the proposed power converter also possesses bidirectional power flow capability. A mathematical model of the power converter and a critical inductance condition are derived in this context for simulation and design. Finally some simulated and experimental results are presented for verification. >
07 Mar 1993
TL;DR: It is concluded that in spite of the evolution of standard DC/DC converters and modular power supplies, custom power supplies are here to stay.
Abstract: An in-depth comparison of standard versus custom power supplies is provided. It is concluded that in spite of the evolution of standard DC/DC converters and modular power supplies, custom power supplies are here to stay. >
16 Aug 1993
TL;DR: In this paper, the authors present the results of the implementation of a two stage AC/DC pre-regulator, using a boost converter (as a power factor corrector), and a full bridge zero voltage switched-PWM converter, in order to improve the dynamic features of the DC bus, working as well as a battery charger within the scheme of distributed power supply.
Abstract: The authors present the results of the implementation of a two stage AC/DC pre-regulator, using a boost converter (as a power factor corrector), and a full bridge zero voltage switched-PWM converter, in order to improve the dynamic features of the DC bus, working as well as a battery charger within the scheme of distributed power supply in which it will be used. >
TL;DR: In this paper, a pitch controller for a wind turbine in a small wind-diesel power system was developed for wind converted power to meet the constraints of system frequency and power limit of wind turbine.
16 Aug 1993
TL;DR: In this paper, a parallel inverter was designed with a current source model to equilibrate the consumption and compensate the capacitive energy, using the oriented field theory in active and reactive power regulation, and the sliding method in the power poles control.
Abstract: A new parallel inverter was designed with a current source model to equilibrate the consumption and compensate the capacitive energy. It uses the oriented field theory in active and reactive power regulation, and the sliding method in the power poles control. The result is an energy transference between AC and DC in both ways without harmonics. The same converter provides connection to photovoltaic cells. A 30-kVA prototype unit is finished. >
27 Sep 1993
TL;DR: In this paper, a new medium to high power static inverter for use in UPSs is presented, and the advantages of its high performance features in a number of fields are discussed.
Abstract: Computers and telecommunications devices require electric power of a very high quality often provided via an uninterruptible power supply (UPS). This paper presents a new medium to high power static inverter for use in UPSs, and discusses the advantages of its high performance features in a number of fields. >