Showing papers on "Power optimizer published in 1997"

A variable speed wind turbine power control

Abstract: To optimize the power in a wind turbine, the speed of the turbine should be able to vary with the wind speed. A simple control scheme is proposed that will allow an induction motor to run a turbine at its maximum power coefficient. The control uses a standard V/Hz converter and controls the frequency to achieve the desired power at a given turbine speed.

Method and system for wind turbine braking

Abstract: Stored rotational energy in an operating variable speed wind turbine is used to pitch blades and brake the wind turbine in the event of utility power grid failure. In one embodiment, a generator IGBT converter and the main power utility grid IGBT converter supply control and pitch servo power during turbine deceleration, and a ride-through capacitor on a DC emergency power supply bus and the main DC link capacitor provide additional energy storage. In another embodiment, a step-down DC/DC power converter adds to the intermediate DC link of the power conversion system with the secondary of the step down converter powering both the hub pitch controller and the wind turbine control system.

Solar cell power source device

Abstract: A solar cell power source device is disclosed which optimizes the power output of the solar cell by detecting a maximum power point of the solar cell and controlling the duty cycle of a switching transistor in a switching power converter such that the output current of the solar cell follows the maximum power point. Also shown is a pulse width modulation controller which multiplies the output voltage of the solar cell by the output current of the solar cell to obtain a power detecting signal, samples the power detecting signal during two different sample periods to determine if the power output is decreasing, and modulating the pulses output to the switching transistor of the switching power converter in order to maintain the power output of the solar cell at the maximum power point.

Control of DC/DC converters for solar energy system with maximum power tracking

Abstract: Solar power converters were used to convert the electrical energy from solar arrays to a stable and reliable power source. The object of this paper is to analyze and design DC/DC power converters of different types in a PV power system to investigate the performance of such converters. A simple method which combines discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The system is kept to operate close to the MPPs, thus the maximum possible power transfer from the solar array is achieved. The implementation of the proposed power converter system was based on a digital signal processor. Experimental tests were carried out for buck, boost and buck-boost power converters using a simple maximum power point tracking algorithm. The efficiencies for the system with different power converters are compared and presented.

A new scheme for maximum photovoltaic power tracking control

Abstract: It is shown that the derivative (dp/sub s//de/sub s/) of output power (p/sub s/) with respect to output voltage (e/sub s/) of a photovoltaic array is equal to zero at the maximum power point. This kind of relationship is independent of insolation and temperature. This property may be utilized to perform maximum power tracking control, that is, at all insolation and temperature levels, the maximum power point can be obtained by regulating dp/sub s//de/sub s/ toward zero. Based on this concept, a new scheme of maximum power tracking control is proposed and applied to a utility-interactive photovoltaic power conditioning system, where the boost chopper is responsible for maximum power tracking control and the inverter responsible for unity power factor control and constant DC input voltage control. The related design method is described. The usefulness and validity of the proposed method are verified by simulation. Compared to conventional methods, this method show a considerably high tracking performance.

Apparatus, method and article of manufacture providing for auxiliary battery conservation in adapters

Abstract: An apparatus, method and article of manufacture are disclosed which provides for auxiliary battery conservation in adapters requiring auxiliary batteries A power controller selects from one of two or more power sources to provide variable power components with DC power For instance, power consumption of the transmitter (more specifically the transmit power amplifier) varies with the desired transmit power level The transmitter can be supplied with DC power from the host device or the auxiliary source or both The power controller can select the source of DC power (ie, the host device or the auxiliary battery) or may combine the two power sources to provide necessary power to the transmit power amplifier

Wind power site

Abstract: The invention concerns a wind power site (2) which comprises at least two wind power plants (4) and a line-side power converter station (46), each wind power plant (4) comprising a rotor (6), a generator (24), a rectifier (30), a smoothing choke (36) and an output-regulating arrangement (62). The line-side power converter station (46) comprises a smoothing choke (48), a power inverter (50), a matching transformer (52), a filter (28) and a regulating arrangement (102), the wind power plants (4) being electrically connected in parallel on the direct current side, and the line-side power converter station (46) being electrically connected in series on the direct current side to the wind power plants (4) connected in parallel on the direct current side. In this way, a wind power site (2) is obtained whose entire available wind power output can be transferred into a regional supply network.

Modular DC cogenerator systems

Abstract: A DC power system receives AC electrical power and DC electrical power from separate first and second sources simultaneously. The DC power system delivers DC electrical power to an output for use by a load requiring DC power. The DC power system includes a converter to convert AC electrical power to DC electrical power and a power sharing control device to control and distribute the DC electrical power to an output. The first source of DC electrical power includes a storage battery, which provides standby DC electrical power to the DC power system. It also includes a power sharing device, which maintains the storage battery fully charged for use at peak loads, when the DC output electrical power is insufficient to meet the DC load. The second source of DC electrical power is a cogenerator such as a fuel cell, a thermo photovoltaic generator or an internal combustion engine and an alternator for generating and delivering DC electrical power to the power sharing device, while producing and delivering waste heat for use of an external load requiring this heat.

Uninterruptible power supply providing continuous power mainstore function for a computer system

Abstract: A method for providing back-up power for system mainstore memory and an uninterruptible power system (UPS) for a computer system are provided. The computer or data processing system includes a system memory and a system power supply. The uninterruptible power supply (UPS) includes an AC output and a DC output, an inverter circuit, a battery and an interface to the system power supply. The inverter circuit supplies AC power to the AC output. The battery supplies DC power to the DC output and to the inverter circuit. The interface enables the inverter circuit to initially supply AC power to the system power supply via the AC output upon detection of a utility power loss and then, after a predetermined period of time, activates the DC output to supply DC power to the system memory via the system power supply, and disables the inverter circuit to stop the initial supply of AC power to the system power supply.

Three phase rectifier using three single phase converters and a single DC/DC converter

Abstract: A power converter for converting three phase input power to DC output power and a method of effecting such conversion. The power converter includes: (1) three single phase DC converters, each having outputs, that receive the three phase input power, (2) a DC/DC converter coupled to the outputs of the three single phase DC converters and (3) a converter selection circuit, associated with the three single phase DC converters, that selects a selected subset of the three single phase DC converters as a function of an electrical characteristic of each phase of the three phase input power to conduct a portion of the three phase input power to the DC/DC converter, the converter selection circuit permitting the power converter to operate on the three phase power with less than three DC/DC converters.

Controlled DC power supply for a refrigeration appliance

Abstract: A controlled DC power supply for a refrigeration appliance is disclosed for reducing heat dissipation and power loss. The refrigeration appliance has AC-powered components, such as compressors and fans, and DC-powered components, such as relays and solenoids. The relays operate to supply AC power from an AC input to the AC-powered components. The relays are selectively activated or deactivated by the controller through enable signals in response to factors such as time and/or temperature. The power supply has an AC-to-DC power conversion circuit for converting AC power at an AC input to one or more DC power outputs for powering DC-powered components. When a group of DC-powered components powered by the same DC power output, such as a group of relays, do not require DC power, the controller selectively disables or reduces a portion of the AC-to-DC power conversion circuit to reduce power consumption and heat dissipation therein. The AC-to-DC power conversion circuit also may utilize a transformerless (reactive) input stage and a dual-output, dual-polarity DC output stage.

Power supply device for power failure

Abstract: PROBLEM TO BE SOLVED: To safely and surely secure emergency power from the battery, etc., of an electric automobile without providing any special equipment to the automobile by supplying supplied power after converting the power into such power that can operate each electric appliance when a power failure occurs. SOLUTION: The battery 22 of an electric automobile is always charged with DC power supplied from commercial power supply 23 through an AC/DC conversion adapter 24 for charging. When a power failure detecting device 25 detects a power failure, the change-over contact of the switch of a cable-side connector component is switched and the contact is closed. Consequently, the DC power stored in the battery 22 is supplied to a DC/AC converter 26 and supplied to each electric appliance of a house after the DC power is converted into 100-V AC power through a DC/AC converter 26. Therefore, emergency power can be secured safely and surely from the battery 22 without providing any special equipment to the electric automobile.

IGBT module construction

Abstract: A hybrid vehicle includes a power unit communicating power between a turbine alternator, flywheel and traction motor. The power unit stores DC power in capacitors and places the power on a DC bus for use in driving the induction machines. Power transistors receive the DC power from the DC bus and are pulse width modulated to output a synthesized AC waveform. The power transistors include a support plate of thermally conductive material having a first surface supporting the transistor and a second surface forming a heat sink with cooling fluid. An electrical insulation layer is fixedly connected between the power transistor and the support plate on the first surface.

Advanced photovoltaic inverter with additional active power line conditioning capability

Abstract: This paper presents an advanced photovoltaic inverter which can deliver the maximum power from photovoltaic arrays to the utility grid for all sunlight conditions, as well as simultaneously providing power conditioning to suppress power line distortions. A new control strategy is developed to maximize the inverter output from the photovoltaic array and to suppress current harmonics in the power line using a single inverter configuration. A new control strategy and experimental results are given.

Power supply control method and corresponding circuit

Abstract: A power supply control circuit generates DC power output intermittently at predetermined intervals during a power saving mode of operation, so as to save power. The power supply control circuit includes an AC power circuit for receiving AC power and for outputting the AC power for a predetermined time; a DC power generator connected to the AC power circuit for converting the AC power into DC power; and a controller receiving a power-on/off signal generated from a power switch, for generating a first power control signal of a first logic state in response to the power-on signal and for generating a second power control signal alternating between the first logic state and a second logic state in response to the power-off signal. The second power control signal alternates between the first and second logic states at predetermined intervals.

High quality flyback power factor corrector based on a two input buck post-regulator

Abstract: The two-input buck (TIBuck) post-regulator has been proposed to improve the dynamic characteristics of conventional power factor correctors (PFCs). This post-regulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power conversion process and, therefore, the overall efficiency of the complete converter is very close to that of the first stage. In this paper, the implementation of a PFC based on a conventional flyback and a TIBuck is analyzed.

A hybrid wind-photovoltaic power supply for a telecommunication system

Abstract: This paper describes a stand-alone hybrid wind-photovoltaic power plant for a remote telecommunication system located on the Black Sea Coast. First, the wind and solar potential of the site and also the load profile were assessed. It is shown that the two energy sources are complementary, so it is possible to have a better energy utilization factor. As a consequence, the storage unit resulting is smaller than in the case of individual wind or PV systems. The power system consists of a 1500 W wind turbine and a 900 W photovoltaic array. Since solar and wind energy converters are finite sources of power, the energy capture efficiency is improved by using a power conditioner (which includes a peak-power tracker and a battery charger). A 220 V/50 Hz inverter was used. The power system was tested and monitored for one year under real conditions in the authors' test facility, also located on the Black Sea Coast.

Load sharing operation of a 14 kW photovoltaic/wind hybrid power system

Abstract: In this paper, a design procedure for photovoltaic/wind hybrid power generation system is presented. The hybrid system is composed of a DC/DC converter for photovoltaic energy conversion, a DC/DC converter for wind energy conversion, a four switch IGBT inverter converting the combined DC power to the AC power and a backup power battery. Here, it is very important to select the desired battery size to meet the stable output and economic cost aspect since this system utilizes a fluctuating and finite energy resource. The purpose of this paper is to develop a sizing method for the PV/wind energy hybrid system with load sharing operation. The method demonstrates a simple tool to determine the desired battery size that satisfies the energy demand from the user with the photovoltaic and wind natural source. The proposed method is verified on a 14 kW hybrid power system including a 10 kW PV generator and a 4 kW wind generator established in Cheju island, Korea.

Effects of turbulence on power generation for variable-speed wind turbines

Abstract: One of the primary advantages of variable-speed wind turbines over fixed-speed turbines should be improved aerodynamic efficiency. With variable-speed generation, in order to maintain a constant ratio of wind speed to tip speed, the wind turbine changes rotor speed as the wind speed changes. In this paper we compare a stall-controlled, variable-speed wind turbine to a fixed-speed turbine. The focus of this paper is to investigate the effects of variable speed on energy capture and its ability to control peak power. We also show the impact of turbulence on energy capture in moderate winds. In this report, we use a dynamic simulator to apply different winds to a wind turbine model. This model incorporates typical inertial and aerodynamic performance characteristics. From this study we found a control strategy that makes it possible to operate a stall-controlled turbine using variable speed to optimize energy capture and to control peak power. We also found that turbulence does not have a significant impact on energy capture.

Parallellism of power converters for automatic power factor correction

Abstract: The modular development of a single-stage 3-phase AC-DC power converter is described. The converter offers several advantageous features.

Method for controlling power generating amount of wind power generator

Abstract: PROBLEM TO BE SOLVED: To perform demand balance without using a circuit for discharging power such as heater, by efficiently controlling the pitch angle even if the demand balance of power falls into the excessive supplying state SOLUTION: When a power generating method of a DC link is adopted in order to restrain the output fluctuation to be generated caused by fluctuation of wind, output of a power generator is automatically adjusted by temporarily storing electric power to a storage battery 9 as a function for preventing voltage from being raised resulting from excessive output to a system in the case where the system power demand is very low and less than output of a wind power generator and by decreasing the power generating amount through a process of adjusting the pitch angle of a blade by using the voltage of the storage battery as a wind speed signal and a pitch angle control signal in the case where the voltage of the storage battery 9 is further raised

SRM drive system with improved power factor

Abstract: The switched reluctance motor (SRM) has the advantages of simple structure, low rotor inertia and high power rate per unit volume. However, the SRM has the disadvantages of high current harmonics and low power factor because of the pulse-type discontinuous excitation. This paper investigates an SRM drive system with reduced harmonics and improved power factor. The system consists of a switching power converter with power factor correction (SPC-PFC), a DC/DC power converter and a three-phase inverter. The SPC-PFC is designed to produce a pure sinusoidal input current, improve the power factor and reduce harmonics. The performances in the proposed system are verified through both simulation and experiments.

Neural network for wind power generation with compressing function

Abstract: The power generated by electric wind turbines changes rapidly because of the continuous fluctuation of wind speed and direction. It is important for the power industry to have the capability to estimate this changing power. In this paper, the characteristics of wind power generation are studied and a neural network is used to estimate it. We use real wind farm data to demonstrate a neural network solution for this problem, and show that the network can estimate power even in changing wind conditions.

DC link voltage control of reduced switch VSI-PWM rectifier/inverter system

Abstract: Three-phase to three-phase VSI-PWM rectifier and inverter systems with eight switches have many advantages: capability of unity or even leading power factor; sinusoidal input current waveforms; bidirectional power flow etc. This paper derives a mathematical model of the DC link voltage control for such a system. The transient model for overall and difference voltages of split capacitor DC link is developed, and typical simulated and experimental results for dynamic responses are presented to illustrate important performance characteristics to verify the developed model.

Power control of wind power generator

Abstract: PROBLEM TO BE SOLVED: To attain small-scale system operation or individual operation of a windmill by suppressing fluctuation in supply power to the system as mush as possible even in a wind power generator which cannot avoid wind speed fluctuation. SOLUTION: This wind power generator is provided with a storage battery 10 which converts windmill generating power consisting of AC power from an induction generator 4 jointed to a windmill blade 1, from DC power into AC power, supplies it to a power system, stores the surplus power of the windmill generating power and supplies insufficient power. If the windmill generating power is in excessive supply, the frequency of reactive power is increased along with charging into the storage battery 10 and stored as the rotation rising energy of the windmill blade 1. On the other hand, if it is in insufficient supply, surplus energy stored as the rotation increasing energy is recovered simultaneously with a discharging process from the storage battery 10, or selectively.

The effects of variable speed and drive train component efficiencies on wind turbine energy capture

Abstract: A wind turbine rotor achieves optimal aerodynamic efficiency at a single tip-speed ratio (TSR). To maintain that optimal TSR and maximize energy capture in the stochastic wind environment, it is necessary to employ variable-speed operation. Conventional constant-speed wind turbines have, in the past, been converted into variable-speed turbines by attaching power electronics to the conventional induction generator and gearbox drive train. Such turbines have shown marginal, if any, improvement in energy capture over their constant-speed counterparts. These discrepancies have been shown to be the result of drive train components that are not optimized for variable-speed operation. Traditional drive trains and power electronic converters are designed to achieve maximum efficiency at full load and speed. However, the main energy producing winds operate the turbine at light load for long periods of time. Because of this, significant losses to efficiency occur. This investigation employs a quasi-static model to demonstrate the dramatic effect that component efficiency curves can have on overall annual energy capture.

Maximum power point tracking charge controllers for telecom applications-analysis and economics

Abstract: Simple charge controllers connect photovoltaic modules directly to the battery bank resulting in a significant power loss if the battery bank voltage differs greatly from the PV Maximum Power Point (MPP) voltage. Modeling work at AES has shown that DC-DC converter type MPP tracking charge controllers can deliver more than 30% more energy from PV modules to the battery when the PV modules are cool and the battery state of charge is low-this is typically both the worst case condition (i.e., winter) and also the design condition that determines the PV array size. Economic modeling, based on typical telecom system installed costs shows benefits of more than $3/Wp for MPPT over conventional charge controllers in this application-a value that greatly exceeds the additional cost of the DC-DC converter.

Matching DC motors to photovoltaic generators for maximum power tracking

Abstract: A maximum power tracking method for separately excited or permanent magnet DC motors fed from photovoltaic generators through buck power converters is given. Positive feedback of motor speed with a developed control law is employed. Averaged state space equations are used to study the transient performance. Experimental results obtained from an implemented system are given.