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Showing papers on "Power optimizer published in 2007"


Journal ArticleDOI
TL;DR: In this article, a buck/buck-boost fused multi-input dc-dc converter and a full-bridge dc-ac inverter is proposed for grid-connected hybrid photovoltaic (PV)/wind power system in order to simplify the power system and reduce the cost.
Abstract: The objective of this paper is to propose a novel multi-input inverter for the grid-connected hybrid photovoltaic (PV)/wind power system in order to simplify the power system and reduce the cost. The proposed multi-input inverter consists of a buck/buck-boost fused multi-input dc-dc converter and a full-bridge dc-ac inverter. The output power characteristics of the PV array and the wind turbine are introduced. The perturbation and observation method is used to accomplish the maximum power point tracking algorithm for input sources. The operational principle of the proposed multi-input inverter is explained. The control circuit is realized by using a digital signal processor and auxiliary analog circuits. For practical applications, functions of soft-start and circuit protection are implemented. Experimental results have shown the performance of the proposed multi-input inverter with desired features

386 citations


Patent
06 Dec 2007
TL;DR: In this article, the converters are coupled in series and an inverter is connected in parallel with the series connection of converters and inverts a DC input to the inverter from converters into an AC output.
Abstract: A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

363 citations


Journal ArticleDOI
TL;DR: Two fundamental conclusions are derived from this study: (1) the buck–boost DC/DC converter topology is the only one which allows the follow-up of the PV module maximum power point regardless of temperature, irradiance and connected load and (2) the connection of a buck– boost DC/ DC converter in a photovoltaic facility to the panel output could be a good practice to improve performance.

239 citations


Patent
14 Nov 2007
TL;DR: In this paper, a method to convert direct current (DC) power generated by a photovoltaic (PV) arrays to alternating current (AC) power using a PV inverter is proposed.
Abstract: A method to convert direct current (DC) power generated by a photovoltaic (PV) arrays to alternating current (AC) power using a PV inverter, the method includes: applying the DC power generated the PV array to the PV inverter; boosting the DC power from the PV array from a predetermined voltage level to a predetermine DC link voltage, wherein the PV array is regulated by the boosting to output a voltage at the predetermined voltage level; converting the boosted DC power to AC power, and disabling the boost of the power generated by the PV array after the array has a predetermined voltage level at least as great as the DC link voltage.

118 citations


Proceedings ArticleDOI
02 Apr 2007
TL;DR: In this article, a voltage balancer for dc distribution is proposed and studied and computer simulation results demonstrated that dc micro-grid was able to supply both ac and dc power to loads simultaneously and stably by 3-wire dc distribution line and load side converters.
Abstract: DC micro-grid is a novel super high quality electric power system. The power is transmitted through dc distribution line and converted to required ac or dc voltages by converters placed near loads. Those load side converters do not need transformers by choosing proper dc distribution voltage (plusmn170 V). The dc power line is composed of 3 wires: +170 V line, neutral line and -170 V line. The distribution voltages have to be balanced to keep high quality power supplying. In this paper, a voltage balancer for dc distribution are proposed and studied. Computer simulation results demonstrated that dc micro-grid was able to supply both ac and dc power to loads simultaneously and stably by 3-wire dc distribution line and load side converters. In addition, another voltage balancer (dc/dc converter type) is also proposed and studied in the last section.

109 citations


Journal ArticleDOI
TL;DR: In this article, a controller is designed that isolates wind-power fluctuations from the power grid by causing the closed-loop wind turbine to behave as a simple first-order power filter, where power injected into the grid is a low pass filtered version of the incident wind power.
Abstract: This paper introduces a new control topology for converter-interfaced wind turbines. Through a singular perturbation decomposition of the system dynamics, a controller is designed that isolates wind-power fluctuations from the power grid. Specifically, the controller causes the closed-loop wind turbine to behave as a simple first-order power filter, where power injected into the grid is a low-pass filtered version of the incident wind power. It is shown that a turbine hub-speed instability imposes a limit on the largest filtering time constant that may be safely implemented. A linearized analysis is used to calculate how a small filter time constant can be implemented to obtain regulation of the tip-speed ratio for the widest range of frequencies. The methodology thus offers the possibility to either deliver a filtered power at suboptimal conversion efficiency or track peak wind power. It is mathematically demonstrated that the control structure achieves the regulation of torsional dynamics and the dc-link capacitor voltage without involving the grid-side converter controls, thus eliminating the influence of those dynamics on the grid. Simulation studies are used to demonstrate the methodology's viability and explore the associated tradeoffs.

109 citations


Patent
19 Feb 2007
TL;DR: In this paper, an LED lighting source comprising a housing adapted for coupling to an AC power source; a rectifier circuit for converting the AC power to a DC supply; a power control circuit disposed in the housing and electrically connected to the DC supply, the LEDs in the string being connected in series and being of a number selected to produce a voltage difference across the power control circuits.
Abstract: The present invention is directed to an LED lighting source comprising a housing adapted for coupling to an AC power source; a rectifier circuit for converting the AC power to a DC supply; a power control circuit disposed in the housing and electrically connected to the DC supply; a string of LED's electrically connected between a control node of the power control circuit and the DC supply, the LEDs in the string being connected in series and being of a number selected to produce a voltage difference across the power control circuit sufficient to power active components of said power control circuit when powered from the DC supply and the power control circuit for limiting a forward current through the string to a nominal forward current of a single LED.

108 citations


Journal Article
TL;DR: In this paper, the impact of large-scale wind power integration on power system is studied by means of the dynamic modeling of wind turbines based on doubly-fed induction generator (DFIG) and power system simulation containing large amounts of wind farms.
Abstract: The impact of large-scale wind power integration on power system is studied. By means of the dynamic modeling of wind turbines based on doubly-fed induction generator (DFIG) and power system simulation containing large amounts of wind farms, the impact of wind power integration on grid voltage level and on transferred power of transmission line, the contribution of DFIG based wind turbines to short-circuit current and short-circuit capacity of the grid, the impact of wind power integration on power system transient stability are investigated. The simulation results show that the large-scale wind power integration may cause overload of transmission lines, increase of short-circuit capacity and change of power system transient stability. Corresponding countermeasures to handle above- mentioned issues emerged after the wind farm integration are recommended.

104 citations


Proceedings ArticleDOI
01 Jul 2007
TL;DR: In this paper, an adaptation of the usual power set point control has been proposed in order to improve the transient behavior for high wind speeds, and several strategies for the active power control are studied.
Abstract: This paper is devoted to the active power control of DFIG wind turbines. An adaptation of the usual power set point control has been proposed in order to improve the transient behavior for high wind speeds. Several strategies for the active power control are studied. In the high wind speed range, the pitch control seems the most relevant to release a power margin while, in the low wind speed range, the increase of the rotation speed is more convenient. The power margin set point variation rate has to be limited in order to avoid torsion oscillations of the shaft. Nevertheless, the reaction speed of the wind turbine lies in the time frame of seconds, so that the participation to the primary frequency control is feasible.

101 citations


Patent
27 Sep 2007
TL;DR: An integrated voltaic energy system incorporates a bio-friendly DC power generator with a photovoltaic (PV) system connected to feed a main service panel and a utility grid.
Abstract: An integrated voltaic energy system incorporates a bio-friendly DC power generator with a photovoltaic (PV) system connected to feed a main service panel and a utility grid. A plurality of inverters are connected one each, to a respective output of one of a plurality of photovoltaic (PV) solar arrays. The outputs of each of the inverters are connected to a main service panel and a utility grid. A further inverter is connected to the DC power generator and in parallel with the other inverters. The DC power generator is also connected to each of the PV solar panel inverters through a switch operated at a specific time manually or automatically. When switched the DC power generator feeds all of the inverters. A resistor/capacitor structure is connected between the DC power generator and each inverter. A self-powered timer may control the output level of the DC power generator.

95 citations


Journal Article
TL;DR: In this paper, the authors presented the development of a wind turbine simulator which consists of an induction motor driven by a torque control inverter, which includes wind turbine simulation, mathematical models of wind turbines, modelling of rotor blade characteristics, modeling of tower effect and emulation of rotor inertia.
Abstract: The paper presents the development of a wind turbine simulator which consists of an induction motor driven by a torque control inverter. The wind turbine simulation system includes wind speed simulation, mathematical models of wind turbines, modeling of rotor blade characteristics, modeling of tower effect and emulation of rotor inertia. Wind speed can be easily programmed based on Van der Hoven spectrum, or recorded wind speed data or manual set up. The developed algorithms were implemented by a low-cost, high-performance digital signal controller with C language and the system was tested in a laboratory with a 1 kW dc generator. The power responses, torque responses and tip speed ratio responses confirms that the system can perform satisfactorily under step changes of power reference, load disturbances and tower effect.


Patent
30 Aug 2007
TL;DR: In this article, a wind turbine system with a pitch control mechanism, an emergency power supply mechanism, and a variable pitch angle was described. But the pitch control was not used to control the pitch angle.
Abstract: A wind turbine system is provided with a wind turbine rotor, a pitch control mechanism, and an emergency power supply mechanism. The wind turbine rotor includes a blade having a variable pitch angle. The pitch control mechanism drives the blade to control the pitch angle. The emergency power supply mechanism generates electric power from rotation of the wind turbine rotor and feeds the electric power to the pitch control mechanism, in response to occurrence of an accidental drop of a system voltage of a power grid.

Patent
03 Apr 2007
TL;DR: An apparatus for powering a load from solar energy comprises a DC/DC converter, battery terminals coupled to an output of the DC and DC converter and coupleable to an energy storage device.
Abstract: An apparatus for powering a load from solar energy comprises a DC/DC converter, battery terminals coupled to an output of the DC/DC converter and coupleable to an energy storage device, and solar panel terminals coupled to an input of the DC/DC converter and coupleable to a solar panel. Logic is coupled to the converter to control its conversion rate. A detector is coupled to the converter and detects its power output. The logic is operable to adjust the conversion rate until the solar panel operates at the smaller of a maximum power point of the solar panel and a power point of the solar panel that results in a maximum desired power.

Journal Article
TL;DR: In this article, the authors address some of the most significant challenges for wind generation facilities, including voltage control, reactive power management, dynamic power-swing stability, and behavior following disturbances in the power grid.
Abstract: In China, as in other parts of the world, many of the best resources for wind generation are located far away from load centers. Large generating facilities connected to distant load centers by long ac transmission lines face numerous technical challenges, regardless of the type of generating facility. This paper addresses some of the most significant challenges for wind generation facilities, including voltage control, reactive power management, dynamic power-swing stability, and behavior following disturbances in the power grid. Wind generation technology has evolved significantly over the past several years, and proven solutions to these technical challenges now exist. Controls integrated into the power electronics and mechanical controls of individual wind-turbine-generators, combined with integrated wind-farm control systems, have the capability of controlling numerous wind turbines so that they act as one unified generating plant at the point of interconnection with the power grid. This advanced hierarchical control of both real and reactive power output can provide dynamic performance that is, in many cases, superior to that achievable with modern conventional synchronous generation. This paper describes: ① Wind farm control functions, including performance for controlling grid voltage in quasi-steady-state and dynamic conditions. ② Low-voltage ride-through characteristics, including performance following severe system disturbances. ③ Dynamic power control functions within wind turbine-generators, including transient and dynamic performance for power swings.

Journal ArticleDOI
TL;DR: In this article, a PID pitch angle controller for a fixed speed active-stall wind turbine, using the root locus method, is proposed to enable the wind turbine to perform power system stabilisation.

Journal ArticleDOI
TL;DR: In this article, the analysis and simulation of 15 kW wind turbine generator (WTG) driving low speed Permanent Magnet Synchronous Generator (PMSG) using PSIM computer simulation program.
Abstract: This paper elaborates on the analysis and simulation of 15 kW Wind Turbine Generator (WTG) driving low speed Permanent Magnet Synchronous Generator (PMSG) using PSIM computer simulation program. The system consists of wind turbine, permanent magnet generator, three-phase diode rectifier, boost converter, and voltage source inverter models. In the WTG model, the best performance coefficient has been determined according to the wind and rotational speed. The low speed PMSG has been used to eliminate gear- box to achieve high efficiency. The ac power output from PMSG is fed to a three-phase diode bridge forward by boost converter to effectively control the dc voltage level. The voltage source PWM inverter is used to interface the system with the electrical utility. The modulation index of the PWM inverter has been controlled to enhance the stability of the dc bus voltage. Simulation results show the superior stable control system and high efficiency. P , m T : mechanical power and torque production from wind turbine, respectively.

Patent
05 Jul 2007
TL;DR: In this article, a method for operating a wind energy installation was proposed, where the wind energy system is switched off following the release of a deactivation signal by a safety cut-out device (20) which logically overrides a management system.
Abstract: The invention relates to a method for operating a wind energy installation, whereby said wind energy installation (10) is especially switched off following the release of a deactivation signal by a safety cut-out device (20) which logically overrides a management system. Said method is improved in that, following a safety cut-out, the wind energy installation (10) is reactivated by means of an operating device (41) which is spatially separated from the wind energy installation (10). The invention further relates to an energy supply system comprising at least one wind energy installation (10), to a safety chain on a wind energy installation, and to a wind energy installation.


Proceedings ArticleDOI
18 Jun 2007
TL;DR: An energy minimization loop, with on-chip energy sensor circuitry, that can dynamically track the minimum energy operating voltage of a digital circuit with changing workload and operating conditions occupies 0.05mm2 in 65nm CMOS.
Abstract: An energy minimization loop, with on-chip energy sensor circuitry, that can dynamically track the minimum energy operating voltage of a digital circuit with changing workload and operating conditions occupies 0.05mm2 in 65nm CMOS. The DC-DC converter that enables this minimum energy operation can deliver load voltages as low as 250mV and achieved an efficiency >80% while delivering load powers of the order of 1 pW and higher from a 1.2V supply

Patent
19 Dec 2007
TL;DR: In this article, a method for operating a wind farm which includes a wind-farm control system and at least two wind turbines, which are connected via an internal grid, is provided.
Abstract: A method for operating a wind farm which includes a wind farm control system and at least two wind turbines, which are connected via an internal grid, is provided. The method includes determining the actual power consumption of the wind farm; and adjusting the power production of at least one of the wind turbines so that the actual power production and actual power consumption of the wind farm are substantially equal. Further, a method for operating a wind farm which includes a wind farm control system and several power sources, are connected via an internal grid, is provided. At least two of the power sources are wind turbines and at least one power source is an additional power source selected from a group consisting of a fuel power source, a battery-based power source and a solar power source. The method includes determining the actual power consumption of the wind farm; and adjusting the power production of at least one of the power sources so that the actual power production and actual power consumption of the wind farm are substantially equal. Furthermore, a wind farm control system arranged for balancing the power production and consumption of a wind farm is provided.

Patent
01 Jun 2007
TL;DR: In this paper, the peak power of a photovoltaic system is determined by incrementally changing the excitation current in predetermined time intervals, until the supplied electric power produces a power level which can be regarded as the peak.
Abstract: A photovoltaic system includes a plurality of photovoltaic modules and a DC motor connected to a three-phase generator driven by a shaft. The three-phase generator is connected to a power mains. The electric power supplied to the DC motor by the plurality of photovoltaic modules is repeatedly measured and adjusted, by changing an external excitation current of the DC motor, to the peak power attainable at the current ambient temperature and the current incident solar radiation intensity. The peak power is preferably determined by incrementally changing the excitation current in predetermined time intervals, until the supplied electric power produces a power level which can be regarded as the peak power.

Proceedings ArticleDOI
23 May 2007
TL;DR: In this paper, a variable step MPPT method is proposed for faster and more precise tracking process, based on an applicable solar cell model, which gives a second order convergence speed, compared with the traditional MPPT methods, which always behave as one order convergence.
Abstract: Solar power is considered as a kind of "clean power". The problems of using solar power include varying weather condition brings different power output of the photovoltaic cells, which may cause a serious waste of solar power. For solving this problem, a maximum power point tracking (MPPT) strategy is required to make Solar cells keep giving maximum power under different environment condition. In this paper, a variable step MPPT method is proposed for faster and more precise tracking process, based on an applicable solar cell model. The new MPPT method gives a second order convergence speed, compared with the traditional MPPT methods, which always behave as one order convergence. According to the applicable solar cell model, a series of differential equations are established to describe the MPPT process, and the maximum power point is present as the solution of those equations. Using a Newton iterative method can not only get the solution of the equations, but also set up ever search step of the tracking process. A matlab-simulink model was established as a two stage PV system including a DC/DC regulator and a load converter to analysis the performance of the proposed MPPT strategy. Simulation result in the last part proved that this MPPT method is practical with a better performance than the traditional strategies.

Proceedings ArticleDOI
02 Apr 2007
TL;DR: In this article, the authors consider possible future ac and dc electronic power system architectures, which fully decouple the dynamics between sources, distribution system, and loads by using separate source-, load-, and distribution-converters.
Abstract: Future advanced electric power systems will have practically all loads interfaced to energy sources through power electronics equipment. Furthermore, all alternative, sustainable, and distributed energy sources, as well as energy storage systems, can be only connected to electric grid through power electronics converters. This will require new concepts for electronic control of all power flows in order to improve energy availability, power density, and overall energy and power efficiency in all electrical systems, from portable devices to cars, airplanes, ships, homes, data centers, and the power grid. Starting from the example of a computer power system, the paper contemplates possible future ac and dc electronic power system architectures, which fully decouple the dynamics between sources, distribution system, and loads by using separate source-, load-, and distribution-converters. Several ideas and possible methodologies for modeling, analysis, and system-level design of such systems, including power flow control, protection, stability, and subsystem interactions, are presented.

Journal ArticleDOI
TL;DR: In this article, a wind park dynamic model is presented together with a base methodology for its application to power system studies, which addresses the wind turbine components and phenomena more relevant to characterize the power quality of a grid connected wind park, as well as the wind park response to the grid fast perturbations, e.g., low voltage ride through fault.
Abstract: In this paper, a wind park dynamic model is presented together with a base methodology for its application to power system studies. This detailed wind generation model addresses the wind turbine components and phenomena more relevant to characterize the power quality of a grid connected wind park, as well as the wind park response to the grid fast perturbations, e.g., low voltage ride through fault. The developed model was applied to the operating conditions of the selected sets of wind turbine experimental benchmark data from Azores and Alsvik wind parks, both for steady and transient operation of the grid. The results show a fairly good agreement in the relevant range of frequencies and indicate the model may be used as a tool for power system studies.

Proceedings Article
Liu Yong1, Shang Tao1
01 Dec 2007
TL;DR: In this article, a GA is utilized to coordinate the wind and thermal generation dispatch and to minimize the total production cost in the economic dispatch considering wind power generation and valve effect of thermal units.
Abstract: As wind power penetrations increase in current power systems, its impacts to conventional thermal unit should be investigated Development of better wind-thermal coordination economic dispatch is necessary to determine the optimal dispatch scheme that can integrate wind power reliably and efficiently In this paper, genetic algorithm (GA) is utilized to coordinate the wind and thermal generation dispatch and to minimize the total production cost in the economic dispatch considering wind power generation and valve effect of thermal units Ten units system incorporating one wind power plant is utilized for numerical simulation Different simulations scenarios with and without wind power production are simulated Simulation result shows the effect of wind power generation in reducing total fuel cost

Patent
24 Jul 2007
TL;DR: In this article, the authors proposed a power storage type photovoltaic power generation system capable of specifying the power generated by a solar cell and the discharge power of power storage devices, and preventing reverse flow of the discharged power of the power storage device charged with the power from a grid.
Abstract: PROBLEM TO BE SOLVED: To provide a power storage type photovoltaic power generation system capable of specifying the power generated by a solar cell and the discharge power of a power storage device, and preventing reverse flow of the discharged power of the power storage device charged with the power from a grid. SOLUTION: A power conditioner of the photovoltaic power generation system in which a solar cell is linked to a grid is provided with: a power converter having both functions of an inverter operation of converting DC power from the solar cell into AC and a converter operation of converting AC power from the grid into DC; a reverse flow relay for detecting that reverse flow is generated in the grid; a single controller for selectively controlling charging/discharging of power for any one of a first power storage device suppressing output variation of the solar cell and a second power storage device charging midnight power; and a changeover switch for interrupting connection between the second power storage device and the controller on the basis of an output of the reverse flow relay when reverse flow of excessive power occurs in the solar cell. In the power conditioner, the controller is connected to a solar cell side of the power converter, and the changeover switch is inserted and connected between the first power storage device, the second power storage device and the power converter. COPYRIGHT: (C)2009,JPO&INPIT

Proceedings ArticleDOI
21 May 2007
TL;DR: A simple method to connect various PV modules in order to improve power quality and the PV interleaving becomes simple and efficient in terms of dynamic performances, steady-state condition and well regulated output voltage is proposed.
Abstract: In the present paper, an application of interleaved dc-dc converter in photovoltaic (PV) modular system has been presented. In the multi-string technology, several PV strings are interfaced with their own dc-dc converter to a common dc-ac inverter. Enlargements are easily achieved since a new string with dc-dc converter can be plugged into the existing platform. This paper proposes a simple method to connect various PV modules in order to improve power quality. Thanks to the proposed digital control method, the PV interleaving becomes simple and efficient in terms of dynamic performances, steady-state condition and well regulated output voltage.

Patent
22 May 2007
TL;DR: In this paper, an interface device transmits a reactive power command depending on a power system from a voltage regulation device of the power system to a wind power generation apparatus electrically connected to the power systems.
Abstract: An interface device transmits a reactive power command depending on a power system from a voltage regulation device of the power system to a wind power generation apparatus electrically connected to the power system, and the wind power generation apparatus receives the reactive power command. Then, the wind power generation apparatus outputs reactive power according to a value obtained by adding, to a reactive power command, another reactive power command for suppression of voltage fluctuation caused by output power of the wind power generation apparatus.

Patent
04 Aug 2007
TL;DR: In this paper, an electrical power converter circuit including a photovoltaic cell and a power supply adapted to control a low power output of the cell is described. But the power supply includes an input switch, an overvoltage detector, an under voltage detector, a rechargeable battery, a DC to DC converter circuit, an output capacitor, a delay element and an output switch.
Abstract: Disclosed is an electrical power converter circuit including a photovoltaic cell and a power supply adapted to control a low power output of the photovoltaic cell. The power supply includes an input switch, an over-voltage detector, an under voltage detector, a rechargeable battery, a DC to DC converter circuit, an output capacitor, a delay element and an output switch. An item of luggage is adapted to support and carry the photovoltaic cell, power supply, and optional ancillary equipment.