Showing papers on "Power optimizer published in 1999"

Pitch-controlled variable-speed wind turbine generation

Abstract: Wind energy is a viable option to complement other types of pollution-free generation. In the early development of wind energy, the majority of wind turbines were operated at constant speed. Recently, the number of variable-speed wind turbines installed in wind farms has increased and more wind turbine manufacturers are making variable-speed wind turbines. This paper covers the operation of variable-speed wind turbines with pitch control. The system the authors considered is controlled to generate maximum energy while minimizing loads. The maximization of energy was only carried out on a static basis and only drive train loads were considered as a constraint. In medium wind speeds, the generator and power converter control the wind turbine to capture maximum energy from the wind. In the high wind speed region, the wind turbine is controlled to maintain the aerodynamic power produced by the wind turbine. Two methods to adjust the aerodynamic power were investigated: pitch control and generator load control, both of which are employed to control the operation of the wind turbine. The authors analysis and simulation shows that the wind turbine can be operated at its optimum energy capture while minimizing the load on the wind turbine for a wide range of wind speeds.

Method and apparatus for multi-power source for power tools

Abstract: Method and apparatus for providing multi-power source for power tools. The apparatus includes (a) a multi-functional power block capable of being powered from multiple energy sources including, but not limited to, AC mains, DC power or fuel cell, and (b) a multi-functional battery module capable of receiving power from the multi-functional power block and fit into the recess in the tool which receives the power pack. The multi-functional power block includes an AC to DC converter, a voltage input selector, a DC to DC converter, an auto voltage selector, and a solid state power monitor which automatically sets the voltage and current to be delivered to power connectors integral to the multi-functional power block. The multi-functional battery module includes batteries, a battery charger which uses power from the multi-functional power block to recharge the battery, a power distributor, and a power monitor which monitors operation of the tool's motor so that the power distributor can automatically deliver the required voltage and current to the tool's motor from one or a combination of battery power and the multi-functional power block to produce the required operational driving torque. The apparatus also includes an AC mains plug and a first flexible line running from the AC mains plug to the multi-functional power block, a DC connector and a second flexible line running from the DC connector to the multi-functional power block, a third flexible line with attached DC plugs at both ends, and a series of adapters designed to fit into recesses in the multi-functional power block and in the tool.

A peak power tracker for small wind turbines in battery charging applications

Abstract: This paper describes the design, implementation and testing of a prototype version of a peak power tracking system for small wind turbines in battery charging applications. The causes for the poor performance of small wind turbines in battery charging applications are explained and previously proposed configurations to increase the power output of the wind turbines are discussed. Through computer modeling of the steady-state operation the potential performance gain of the proposed system in comparison with existing systems is calculated. It is shown that one configuration consisting of reactive compensation by capacitors and a DC/DC converter is able to optimally load the wind turbine and thus obtain maximum energy capture over the whole range of wind speeds. A proof of concept of the peak power tracking system is provided by building and testing a prototype version. The peak power tracking system is tested in combination with a typical small wind turbine generator on a dynamometer. Steady-state operating curves confirming the performance improvement predicted by calculations are presented.

New approach to photovoltaic arrays maximum power point tracking

Abstract: The present trend for commercial telecommunication and scientific satellites is the utilization of standard platform, characterized by a high level of flexibility and reduced nonrecurring costs. One of the areas where flexibility is mandatory is the electrical primary power subsystem, due to the impact on solar array configuration and dimensions and on power conditioning unit. Use of the maximum power point tracker (MPPT) concept allows optimization of the above mentioned subsystem, maximizing the power transfer from the photovoltaic generator. The purpose of the paper is to present a new MPPT approach that allows minimization of the drawback caused by the intrinsic capacitance of the photovoltaic array (generally neglected) giving the possibility of operation with a large degree of freedom, independent from the converter topology and photovoltaic power generator, electrical network and technology.

Integrated photovoltaic system

Abstract: An integrated photovoltaic system includes a plurality of individual photovoltaic modules that each convert solar energy into DC power. Each of the photovoltaic modules is coupled to a busway that combines the DC power generated by each photovoltaic module into a DC power output. The connection between each photovoltaic module and the busway is environmentally sealed, as is the electrical wiring contained within the busway. The busway is coupled to a DC to AC power inverter that provides a supply of AC power. The coupling between the busway and the power inverter is environmentally protected, such that the entire DC wiring for the photovoltaic system is environmentally sealed and the system functions as an “AC photovoltaic system” having an AC power output.

High efficiency power system with plural parallel DC/DC converters

Abstract: A distributed staged power system for use in electric and hybrid electric vehicles, and the like. The system comprises a plurality of parallel DC-to-DC power modules that are controlled by way of input and output control signal interfaces using a smart controller. The distributed staged power system provides higher efficiency because of smart staging of the power modules. The distributed staged power system enables or disables each of the modules as determined by a smart controller to provide the highest possible conversion efficiency.

A fast maximum power point tracker for photovoltaic power systems

Abstract: In this paper, the authors proposed a novel maximum power point controller, which not only can track the maximum power of an array quickly without perturbation and observation process but also can be implemented easily. The main idea is based on the graphical interpretation of the maximum power point as the intersecting point of two curves on the phase plane corresponding to the solution of two algebraic equations. In other words, the operating point is the intersecting point of the PV-array characteristic curve and the maximum power line. A circuit is constructed based on a boost circuit and a three phase full bridge inverter.

Integrated planar inductor scheme for multi-module interleaved quasi-square-wave (QSW) DC/DC converter

Abstract: Compact, high-efficiency, low-voltage and large-current DC/DC power converters with a fast transient slew rate are needed for future generation microprocessors. The interleaved quasi-square-wave (QSW) topology is a good candidate to improve their transient response significantly. Inductors are critical components in these converters. An integrated planar inductor scheme for multi-module interleaved QSW power converters is proposed. This integrated inductor utilizes the phase relationships of the currents in each module to integrate all the separate inductors for each module into one core, resulting in great reductions in the size and power losses of the inductor.

A simple wind power generating system with permanent magnet type synchronous generator

Abstract: The authors propose an inexpensive wind power generating system in this paper. Existing wind power generating systems are mostly of large capacity (over 100 kW) and high-priced (about 1000 USS/kW). Because of the erratic changes of wind power and of smoothing peak power, an AC/DC converter-fed battery system is recommended. Thus, one requires the exact rotating speed of generators (especially in the case of synchronous generators) to use AC/DC converters with high quality. These factors are increasing the cost of such systems. The authors adopt a compact permanent magnet type synchronous generator, which doesn't need exciting current, and a step-up/down buck-boost chopper to wind power generating system of a few kW output without position or speed sensor. In addition, they employ an inexpensive rectifier circuit using a diode bridge instead of an AC/DC power converter with PWM method. Using these methods, they achieve a simple and inexpensive wind power generating system.

Power line filter design considerations for DC-DC converters

Abstract: This article presents an overview of switching regulated DC-DC power convertor electromagnetic interference problems and possible solutions, with special emphasis on power line conducted emissions and power line input filters. Potential stability and performance problems that can be caused by the interaction between the power line input filter and the switching regulator are discussed in detail. Candidate damped input filter structures are presented, along with a general input filter design strategy and a detailed design procedure for one of the candidate configurations.

An exact analysis of Class-DE amplifier at any output Q

Abstract: Previous papers on Class-DE power amplifiers are based on the assumption that the Q factor of the series-tuned circuit is high enough that the load current is sinusoidal. This paper presents a theoretical description of the Class-DE power amplifier in which the assumption of infinite Q is eliminated. Design and performance curves are given and discussed and a comparison with the previous known results, a practical tuning procedure, and practical limitations of the Class-DE circuit are also presented. Such an analysis is useful because low-Q circuits are appropriate for applications in which the harmonic content of the output is not important, e.g., in high-efficiency DC/DC converters, in providing RF energy for heating, for generation of plasmas, arcs, or sparks, for communications jamming, or for input driver to a higher power stage. Experimental results closely agree with the theoretical predictions.

Integrated design environment for DC/DC converter FET optimization

Abstract: This paper presents a new integrated design environment for device optimization for DC/DC converter applications. The tool, developed for a synchronous buck converter, combines a physical device model with a power loss model and uses the results to evaluate optimum die specifications. This integrated environment has been used for several different applications and has led to significant improvements in the final in-circuit efficiency.

Maximum power operating inverter system

Abstract: PROBLEM TO BE SOLVED: To solve the problem in an AC output solar cell power generating system for taking out maximum power from solar cells and superimposing it on the power from an AC power supply, that the power conversion loss is increased because power is converted twice when a DC/DC converter having a maximum power point tracking function is combined with an inverter in order to realize maximum power point tracking and total efficiency of the power generating system is lowered. SOLUTION: Maximum power point tracking is realized without employing a DC/DC converter by keeping optimal operating conditions of an inverter from the waveform of pulse voltage and current generated from solar cells when the instantaneous output power from the inverter varies over time.

Wind power plant with an integrated acceleration system

Abstract: A wind power plant comprises a wind acceleration system having an accelerating wind means for acceleration of an incoming prevailing wind and a plurality of turbine chambers each of which is a closable outlet passage of the accelerating wind means and closed-off by a controlled closing-off means. The accelerating wind means includes regulating means for modulating accelerated wind speeds in the acceleration system. Each turbine chamber is used for mounting a wind driven turbine which is operatively connected to an electric generator by a mechanical transmission means and an adapted gearing to convert mechanical energy into electrical energy. A wind direction sensor, a wind speed sensor and a control unit are provided for controlling the operation of the wind power plant. The control unit processes the data received from the wind sensors to selectively close-off the turbine chambers by controlling the closing-off means for optimizing energy production and to modulate the accelerated wind speeds in the acceleration system by controlling the regulating means for maintaining regular regimes of operation of the wind driven turbines in spite of any high prevailing natural wind speed. In the construction of the wind power plant any controllable (changeable or closable) opening can be divided into smaller controllable openings arranged at different altitudes and closed-off by controlled windows (windows, doors or shutters) which implement functions of the regulating means or closing-off means. Whereby the wind power plant can be constructed in any scale and will harness the wind resources intensively and effectively and operate normally at any high natural prevailing wind speed.

Single phase amplitude modulation inverter for utility interaction photovoltaic system

Abstract: In this paper, a new inverter for a utility interactive photovoltaic system is proposed. This system consists of the DC converter that generates the single phase absolute value of sinusoidal current and a square wave voltage inverter which synchronizes with the AC power source. This DC converter consists of two switching devices and a capacitor for a nondissipative snubber circuit. The DC converter is applied to a pulse width modulation to obtain absolute value of sinusoidal current. It is not necessary to set the dead time of the switching devices in generating waveforms. Therefore, we can regard the dead time effects as small. The inverter is switched by the AC power source frequency so the line noise of voltage and current caused by the high frequency switching is very small. In this paper, it is confirmed by simulation that the proposed inverter for a new photovoltaic system has stable operation and good output characteristics are obtained by the experimental results.

Line power unit for micropower generation

Abstract: A line power unit controls electrical power delivery to a grid from a three phase permanent magnet generator. A line power unit controller receives a power level command and controls a main inverter that draws DC power from a DC bus to deliver the commanded power to a grid. The DC bus is fed DC voltage via a three phase permanent magnet generator and a rectifier. The inverter delivers power to the grid via a filter, transformer and main contactor. The line power unit controller also controls the main contactor to break the connection with the grid. A precharge circuit draws power from the grid to precharge the DC bus to a precharge voltage. Alternatives include a start inverter separate from the main inverter that permits simultaneous delivery of power to the grid and commutation of the permanent magnet generator as a motor to spin an engine connected thereto at a speed sufficient to permit engine starting. Another alternative utilizes a single inverter for engine starting and power delivery which does not permit these operations to be simultaneously performed. Further alternatives include eliminating the transformer by utilizing a high-voltage rated main inverter.

Transformerless DC-to-AC power converter and method

Abstract: A system and method for generating an AC power output signal from a DC power input signal. The system incorporates a transformerless DC-to-DC boost regulator including a plurality of boost stages coupled in series for receiving a DC input signal and producing a boosted DC power signal. The system further incorporates a DC-to-AC converter coupled to the transformerless DC-to-DC boost regulator, for receiving the boosted DC power signal and generating an AC power output signal. A control element is coupled to both the DC-to-DC boost regulator and the DC-to-AC converter. In at least one embodiment, the system and method for generating an AC power output signal from a DC power input signal are used in connection with an uninterruptible power supply.

Application of a power-controlled flywheel drive for wind power conditioning in a wind/diesel power system

Abstract: In isolated or autonomous power systems incorporating renewable power sources such as wind turbine generators, short-term energy storage devices are desirable for economic operation and transient load mitigation. The paper presents a 45 kW flywheel energy storage system with bi-directional power control capability along with its application into an autonomous wind/diesel power system. The technical aspects relating to system integration and those of the design and development of reliable active and reactive local power controllers are described. Practical results obtained from the application of the storage system for wind power conditioning are presented and supported by analysis.

Incorporation of wind power in the east Danish power system

Abstract: This paper gives an overview of some of the phenomena which will occur in a power system with a large amount of wind production Some of the problems occur due to the induction generators used in the windmills Other problems occur due to the stochastic nature of the wind The paper concentrates on the problems occurring in the eastern Danish power system up to year 2008, where three off-shore wind farms each of 150 MW will be connected to the system To integrate such a large amount of production from windmills creates a technical challenge, which affects the basic principles for both planning and operation of the system

A wind power plant and a method for control

Abstract: A wind power plant comprising at least one wind power station (29), which includes a wind turbine and an electric generator (1) driven by this wind turbine, and an electric alternating voltage connection (30) connecting the wind power station with a transmission or distribution network (31). On the network side of the plant a frequency converter (34) is connected in the electrical alternating voltage connection (30), which frequency converter is arranged to fix the frequency of the connection between the wind power station and the converter to be essentially below the network frequency and to convert this low frequency of the connection into correspondence with the higher frequency of the network. Furthermore, the invention comprises a corresponding method for control.

Development of converters for improving efficiency and achieving both power factor correction and fast output regulation

Abstract: Development of converters for improving efficiency and achieving both fast regulation and power factor correction (PFC) is presented in the paper. A general configuration is first introduced, and, then, the degenerated configurations are derived according to the variation of power-split ratios. With these configurations, not only the converter systems discussed in literature can be developed alternatively, but novel converters can be synthesized. In addition, power-split and power-combination configurations are introduced to help the development of converter systems, resulting in more physical insights into the system configurations. With the concept of energy partial processing, overall conversion efficiency is improved, while PFC and fast regulation can still be achieved effectively.

An independent maximum power extraction strategy for wind energy conversion systems

Abstract: A new hysteresis maximum power tracking scheme, which is independent of wind turbine or turbine generator characteristics, is proposed and investigated in this paper. As a comparison, two other wind energy conversion control schemes, namely DC-link voltage based linear control and hill-climb maximum power tracking, are studied. A simplified wind turbine model using MATLAB/SIMULINK is given in this paper as well. Simulations for these schemes have been conducted. Some field test waveforms are also presented.

An alternative to supply DC voltages with high power factor

Abstract: AC/DC is one of the most common power conversions in power electronics, DC loads should be fed with a stable and a tight regulated voltage. At the same time, the AC/DC converter should comply with low-frequency harmonic regulation. The classical two-stage AC/DC converters achieve these two objectives, although the overall efficiency is low because the power is processed twice. An alternative solution is presented in this paper. It is based on the division of the input power in two parts, one of them processed only once and keeping a unity power factor. This strategy improves the efficiency and reduces the size of the converter without any complex control scheme. This proposal can be implemented with a great variety of well-known topologies. The experimental results show that this solution is a good tradeoff between efficiency and size.

Power electronics building blocks

Abstract: Power electronics is a very important field in modern day electronics. There are many power electronic modules that get used over and over again in the field of research and education. It would be ideal if these modules were made readily available. Instead of rebuilding these modules from scratch, specific power electronic modules could be selected to perform the desired task. This will reduce the time spent on rebuilding and troubleshooting. Dc/Dc converters are frequently used in the field of power electronics as rectifiers and inverters to perform voltage regulation. The most common form of a Dc/Dc converter is the switched mode converter. As the name implies, switches are utilised to achieve the desired output regulation. The switch duty ratio is controlled by means of pulse-width modulation, which is the most common form of control technique. This paper focuses on the design of a Dc/Dc converter that can be cascaded with a PWM module to illustrate the concept of power electronics building blocks. A Class C chopper circuit is to be constructed to perform voltage regulation in the buck, boost and buck-boost mode. The half-bridge circuit would be able to be configured to operate in the three modes through selection of the transistor and diode pair. The selected conduction “path” would determine the mode of operation.

Power supply module in integrated circuits

Abstract: This invention discloses the concept of the integration of the four terminal switcher and the capacitor pairs for the DC to DC converter or power supplier. This invention can be built by IC process as the DC to DC converter or power supply alone or used as power supply or converter module or block for distributed power in the System-on-Chip. This invention discloses the basic structure of the DC to DC converter or power supply module on standard CMOS IC process and on SOI substrates. This basic structure of the DC to DC converter or power supply module provides high current and low voltage applications for future generations of ICs.

Fast dynamic DC-link power balancing scheme for a PWM converter-inverter system

Abstract: We propose a new converter control scheme for a converter-inverter system. The strategy is to fully utilize the inverter dynamics in controlling the converter dynamics. We obtain the power dynamics for both converter and inverter systems, and control the converter power so that it matches the required inverter power exactly. Then, in the ideal case, no power flows through the DC-link capacitors, and thus the DC-link voltage does not fluctuate even though a very small amount of the DC-link capacitance is used. In forcing the converter power to match the inverter power, we utilize the master/slave control concept. We control the DC-link voltage level indirectly through the stored capacitor energy in order to exploit the advantage of the linear dynamic behavior of the capacitor energy. This helps us to circumvent a complex control method in regulating the DC-link voltage. Through simulation and experimental results, the superiority of the proposed converter control scheme is demonstrated.

Full-load-range-ZVS hybrid DC-DC converter with two full-bridges for high-power battery charging

Abstract: A novel soft switching DC-DC power converter is proposed that is ideal for high-power battery charging applications. Its main advantages are zero-switching under all operating conditions without significant conduction loss penalty, and significantly lower filter requirement compared to conventional power converters. The application of the proposed converter for high-power battery charging is discussed along with simulation and experimental results.

Inverter for a photovoltaic unit for use in a solar generator to maximize the power/performance output, the so-called maximum power point tracking

Abstract: An inverter has a common inverter bridge with several parallel switched DC/DC converters/transducers added to convert the DC from one voltage level to a higher voltage level. The inverter has several parallel-arranged slots to accommodate the converters/transducers, with a computer interface unit for central control, while the inverter can be formed without galvanic separation and with no transformer on the AC side.

Photovoltaic power generating set

Abstract: PROBLEM TO BE SOLVED: To enable a photovoltaic power generating set to make uninterruptible power feed to an important load, without causing instantaneous interruptions caused system power failure, etc., by effectively utilizing the power generated from a solar battery as much as possible. SOLUTION: A photovoltaic power generating set is provided with an inverter (first inverter) 17 connected with a solar battery 15, another inverter (second inverter) 22 connected with a rectifier 19 and a battery 20, and an input bridging switch 23. The set is also provided with an AC output circuit 24, which always feeds the AC power outputted from the inverters 17 and 22 to a load 28 and a control circuit 30, which controls the operation of the inverters 17 and 22 and the opening/closing of the switch 23. The control circuit 30 is provided with a normal operation control means, which operates the inverter 17 by controlling the tracking of the maximum power point of the solar battery 15 and the inverter 22 by performing CVCF control through the means of opening the switch 23, and an insufficient operation control means which operates the inverters 17 and 22 by performing CVCF control by using the solar battery 15, rectifier 19, and battery 20 as a common DC power source, due to the power feed becoming insufficient due to the CVCF control. COPYRIGHT: (C)2001,JPO

Bidirectional DC-to-AC inverter with improved performance

Abstract: Switch-mode DC-to-AC inverters using DC-to-DC converter topology have many advantages over the traditional bridge-type inverter. A bidirectional power circuit combined with a nonlinear robust control is proposed to form a high performance inverter. The output voltage of the inverter can be stabilized regardless of large changes in input voltage and output current. The distortion near the zero crossing point can be minimized. The load of the inverter can be resistive, inductive, or capacitive. Simulation results and experimental verification are provided.