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Showing papers on "Isolation transformer published in 2009"


Journal ArticleDOI
TL;DR: A control method is proposed to lock the switching frequency at just above the load insensitive frequency for optimized efficiency at heavy loads and a prototype transcutaneous power regulator is built and found to to perform excellently with high efficiency and tight regulation under variations of the alignment or gap of the trans cutaneous transformer, load and input voltage.
Abstract: Based on a generic transcutaneous transformer model, a remote power supply using a resonant topology for use in artificial hearts is analyzed and designed for easy controllability and high efficiency. The primary and secondary windings of the transcutaneous transformer are positioned outside and inside the human body, respectively. In such a transformer, the alignment and gap may change with external positioning. As a result, the coupling coefficient of the transcutaneous transformer is also varying, and so are the two large leakage inductances and the mutual inductance. Resonant-tank circuits with varying resonant-frequency are formed from the transformer inductors and external capacitors. For a given range of coupling coefficients, an operating frequency corresponding to a particular coupling coefficient can be found, for which the voltage transfer function is insensitive to load. Prior works have used frequency modulation to regulate the output voltage under varying load and transformer coupling. The use of frequency modulation may require a wide control frequency range which may extend well above the load insensitive frequency. In this paper, study of the input-to-output voltage transfer function is carried out, and a control method is proposed to lock the switching frequency at just above the load insensitive frequency for optimized efficiency at heavy loads. Specifically, operation at above resonant of the resonant circuits is maintained under varying coupling-coefficient. Using a digital-phase-lock-loop (PLL), zero-voltage switching is achieved in a full-bridge converter which is also programmed to provide output voltage regulation via pulsewidth modulation (PWM). A prototype transcutaneous power regulator is built and found to to perform excellently with high efficiency and tight regulation under variations of the alignment or gap of the transcutaneous transformer, load and input voltage.

221 citations


Proceedings ArticleDOI
21 Mar 2009
TL;DR: In this article, the authors proposed a ripple reduction method in current without using any additional switching devices, which realized a DC active filter function without increasing the number of the switching device because the energy buffer capacitor is connected to the center tap of the isolation transformer.
Abstract: This paper proposes a ripple reduction method in current without using any additional switching devices. The current ripple that has double frequency component of the power supply is generated in the DC part when a single-phase PWM inverter is used for a grid connection. The current ripple causes short lifetime for electrolytic capacitors, batteries and fuel cells. The proposed circuit realizes a DC active filter function without increasing the number of the switching device because the energy buffer capacitor is connected to the center tap of the isolation transformer. In addition, the buffer capacitor voltage is controlled by the common mode voltage of the inverter. This paper describes the features of the proposed circuit, control strategy and experimental results. As a result, about 1/5 times of the ripple can be reduced.

139 citations


Patent
John L. Melanson1
02 Dec 2009
TL;DR: In this article, the primary-side signal value is a sample of a current in the primary side windings of the transformer and the secondary-side current is a current out of a filter coupled to a rectifier and into a load.
Abstract: A power control system includes a transformer and a controller regulates a current on a secondary-side of the transformer based on a primary-side signal value. In at least one embodiment, the secondary-side current is a current out of a filter coupled to a rectifier and the secondary-side of the transformer and into a load. In at least one embodiment, the primary-side signal value is a sample of a current in the primary-side windings of the transformer. In at least one embodiment, the primary- side signal value represents a sample value of a primary-side transformer current. Proper timing of sampling the primary-side signal value substantially eliminates contributions of a transformer magnetizing current from the primary-side transformer current sample. Sampling the primary-side signal value when contributions of the transformer magnetizing current are substantially eliminated allows at least an average of the secondary-side current to be determined from the primary-side signal value.

108 citations


Journal ArticleDOI
TL;DR: In this paper, a custom high-power signal generator that injects high-frequency signals on the bushing tap of the transformer under investigation, as well as a circuit to replace the short bushing-tap short and allow online operation of the system is demonstrated on a 650 kV transformer.
Abstract: Online transformer condition monitoring techniques based on transfer function methods, such as transmission-line diagnostics and swept frequency-response analysis, require the injection of a known test signal into the transformer On larger power transformers, a practical method is to use the available bushing tap connection In this paper, we will discuss a custom high-power signal generator that injects high-frequency signals on the bushing tap of the transformer under investigation, as well as a circuit to replace the bushing tap short and allow online operation of the system Finally, the system is demonstrated on a 650 kV transformer

95 citations


Proceedings Article
06 Oct 2009
TL;DR: In this article, the authors proposed a new inverter topology for transformer-less photovoltaic (PV) systems, which is suitable for using in transformerless PV applications due to high efficiency, low leakage current and EMI.
Abstract: The grid-connected photovoltaic (PV) systems are an important part of renewable energy sources and their integration is getting more and more widespread. In order to improve the efficiency, practicality and reliability of the PV systems, many kinds of new inverter topologies have been proposed to avoid using a grid isolation transformer. The NPC topology and two other derived topologies are presented and analyzed in this paper. Validated by experiments, it has been proven that they are very suitable for using in transformer-less PV applications due to high efficiency, low leakage current and EMI. Simulations using Simulink and the PLECS toolbox have been done for evaluating efficiency of different NPC topologies and some experimental results are presented in this paper to validate the operation of the different topologies.

80 citations


Journal ArticleDOI
TL;DR: This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit, and will compare various modified forms of theMMCCC topology with existing dc-dc converter circuits from compactness and component utilization perspectives.
Abstract: This paper presents the various configurations of a multilevel modular capacitor-clamped converter (MMCCC), and it reveals many useful and new formations of the original MMCCC for transferring power in either an isolated or nonisolated manner. The various features of the original MMCCC circuit are best suited for a multibus system in future plug-in hybrid or fuel-cell-powered vehicles' drive train. The original MMCCC is capable of bidirectional power transfer using multilevel modular structure with capacitor-clamped topology. It has a nonisolated structure, and it offers very high efficiency even at partial loads. This circuit was modified to integrate single or multiple high-frequency transformers by using the intermediate voltage nodes of the converter. On the other hand, a special formation of the MMCCC can exhibit dc outputs offering limited isolation without using any isolation transformer. This modified version can produce a high conversion ratio from a limited number of components and has several useful applications in providing power to multiple low-voltage loads in a hybrid or electric automobile. This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit. In addition, this paper will compare various modified forms of the MMCCC topology with existing dc-dc converter circuits from compactness and component utilization perspectives.

76 citations


Journal ArticleDOI
TL;DR: In this paper, the voltage oscillations during switching-in operations are recorded and calculated with and without a cable installed between the VCB and the transformer, and the measured voltages show good agreement with the calculated voltages.
Abstract: The work presented in this paper deals with the investigation of circuit breaker prestrike effect that occurs during energizing a distribution transformer. An experimental test setup that consists of a supply transformer, a vacuum circuit breaker (VCB), a cable and a test transformer is built, and the prestrikes in the VCB are recorded. The test transformer is a prototype distribution transformer, with installed measuring points along transformer windings in each phase. Voltage oscillations are measured along the windings and transformer terminals. The transformer is modeled by lumped parameters extracted from telegrapher's equations in discrete form. Voltage oscillations during switching-in operations are recorded and calculated with and without a cable installed between the VCB and the transformer. Computed voltages show good agreement with the measured voltages. Described method can be used by transformer manufacturers to estimate voltage wave forms during switching or lightning, to provide useful information for insulation coordination studies, and to investigate resonance effects in transformer windings.

53 citations


Proceedings ArticleDOI
01 Nov 2009
TL;DR: In this paper, an innovative DC-DC converter is investigated which provides electrical power to the gate driver units of medium voltage level converters, which is achieved with a coreless transformer in order to obtain a cost effective solution.
Abstract: In this paper, an innovative DC-DC converter is investigated which provides electrical power to the gate driver units of medium voltage level converters. For the discussed DC-DC converter, a galvanic isolation (isolation voltages of up to 35 kV) is required. This electrical isolation is achieved with a coreless transformer in order to obtain a cost-effective solution. Furthermore, the DC-DC converter contains a full-bridge converter being operated with low switching losses, a resonant compensation network to achieve a high overall efficiency and an output side rectifier. In this paper, the design of the coreless transformer, the appropriate compensation networks and the power electronics are discussed in detail. Moreover, measurement results obtained from a 100 W prototype, operated at a switching frequency of 410 kHz, are presented. With the proposed setup, a high overall efficiency of up to 80% and a transformer breakdown voltage of 55 kVrms is achieved. Thus, the proposed converter concept represents a very competitive solution with respect to the typically employed DC-DC converters with dry-type cast coil transformers.

53 citations


Patent
16 Jul 2009
TL;DR: In this article, an open loop power switcher, a power isolation transformer, a backlight driving circuit, and a power circuit are employed to convert a direct current (DC) power into an alternating current (AC) input voltage.
Abstract: A power supply apparatus includes an open loop power switcher, a power isolation transformer, a backlight driving circuit, and a power circuit. The open loop power switcher converts a direct current (DC) power into an alternating current (AC) input voltage. The power isolation transformer is coupled to the open loop power switcher and includes a primary-side winding, a first winding, and a second winding, wherein the first and second windings are disposed at the secondary-side of the power isolation transformer, and the first winding is employed for generating a first voltage signal according to the AC input voltage. The backlight driving circuit is employed for driving a backlight module according to the first voltage signal. The power circuit is employed for receiving a second voltage signal generated from the second winding according to the AC input voltage, in order to generate an output power signal.

43 citations


Patent
24 Jul 2009
TL;DR: In this paper, a method and system for enhancing computer peripheral safety is presented, which is configured to monitor and isolate alternating current (A.C.) supplies with and/or from any peripheral subsystems or devices.
Abstract: A method and system for enhancing computer peripheral safety is provided. In accordance with various aspects of the present invention, the exemplary method and system are configured to monitor and/or isolate alternating current (A.C.) supplies with and/or from any peripheral subsystems or devices. An exemplary method and system comprises an A.C. supply, a host computer system, and a peripheral subsystem or device connected to the host computer system, such as an ultrasound imaging and/or therapy peripheral, and an isolation subsystem configured for monitoring and/or isolating the A.C. supply from the peripheral subsystem or device. In accordance with an exemplary embodiment, an isolation subsystem comprises application software and associated modules and functions that when executed continuously monitors and/or polls the host computer's hardware and/or operating system for the presence of an isolated source, such as a battery, or an unisolated power source, such as through a battery charger and/or other connection path to the A.C. main supply. In accordance with other exemplary embodiments, an isolation subsystem can comprises a wireless or other safe/isolated electrical link for connecting a patient contact device, and/or a verification link or other verification mechanisms configured between an isolation transformer and host computer to monitor or observe usage to power the host computer and peripheral subsystem.

42 citations


Journal ArticleDOI
TL;DR: The need for an isolation transformer is eliminated, the size, weight and cost of the system are significantly reduced and new control algorithms of the rectifier, the charger/discharger and the inverter are proposed.
Abstract: A transformerless three-phase on-line uninterruptible power supply (UPS) is proposed. The proposed UPS is composed of a rectifier, an inverter and a battery charger/discharger. The rectifier regulates a DC-link voltage and performs power factor correction. On the other hand, the inverter provides a regulated sinusoidal output voltage and has the current-limiting capability for an impulsive load. The battery charger/discharger reduces the number of battery and supplies the power demanded by the load in the event of the input power failure or abrupt decrease of the input voltage. Since both neutral lines of the input and output voltages are connected at the centre of the DC-link, the need for an isolation transformer is eliminated and the size, weight and cost of the system are significantly reduced. Additionally, new control algorithms of the rectifier, the charger/discharger and the inverter are proposed.

Journal ArticleDOI
TL;DR: In this paper, a single-stage bidirectional power electronic transformer (PET) for lighting systems as a three-phase electronic ballast is presented, which can operate without any bulky storage elements.
Abstract: This paper presents a single-stage bidirectional power electronic transformer (PET) for lighting systems as a three-phase electronic ballast. The lighting system supplies multilamp units that are controlled simultaneously by a bidirectional PET using a pulsewidth modulation scheme. The PET contains a single-input multioutput high-frequency isolating transformer to control the illumination of the lamps as well as providing galvanic isolation in each unit simultaneously. The high-frequency operation, direct ac to ac conversion, and bidirectional power flow capabilities help the PET to operate without any bulky storage elements. So good efficiency, and low weight, volume, and cost of the power conversion system can be achieved. The control strategy promotes the ballast performance to let fluorescent lamps operate free from both voltage flicker and disturbances. As a result, improved dimmable illumination, lamps protection, and increasing lifetime of lamps can be achieved. A design procedure based on equivalent circuit is presented to determine the resonant output circuit parameters. The experimental results of the prototype, which converts 110 V/3phi/50 Hz input voltage to 130 V/1phi/25 kHz and 70 V/1phi/25 kHz output voltages, show the practical aspects of the proposed PET.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a bidirectional DC-DC converter which employs the two bridge configuration resonant class-E converters on the both sides of the isolating transformer.
Abstract: To improve the energy quality, most of the renewable energy systems include an energy storage element charged by the bidirectional DC-DC converter. This paper proposes the bidirectional DC-DC converter which employs the two bridge configuration resonant class-E converters on the both sides of the isolating transformer. The low side converter is controlled as step up and the high side converter is controlled as step down. The proposed system is characterized by good dynamic properties and high efficiency because the converter transistors are switched in ZVS conditions. A theoretical analysis to provide relations for system design, and the laboratory model investigations to validate the system characteristic are given in the paper.

Proceedings Article
06 Oct 2009
TL;DR: In this paper, a new cascaded converter based on two level half-bridge modules for shunt compensators is proposed in order to compensate the currents produced by the electric traction system as a popular of medium voltage unbalanced load properly.
Abstract: Cascaded multi-level converters have some noticeable advantages such as high reliability, efficient fault management capability, simple structure, and adaptability with different power levels. Furthermore, these converters could be connected to medium-voltage networks without an isolating transformer. However, the voltage balancing of the DC capacitors is a highly challenging task particularly in harmonically polluted and unbalanced systems. To overcome this problem, a new cascaded converter based on two level half-bridge modules for shunt compensators is proposed in this paper. The control algorithm of the compensator and its configuration are designed and optimized in order to achieve an efficient performance in unbalanced systems. This makes it possible to compensate the currents produced by the electric traction system as a popular of medium voltage unbalanced load properly.

Patent
John L. Melanson1
30 Jun 2009
TL;DR: In this article, a switching power converter with a current sensing transformer providing input to an auxiliary power supply provides efficient current sensing, while reducing the cost of the magnetic coupling element, which is compensated for in the current sensing result.
Abstract: A switching power converter having a current sensing transformer providing input to an auxiliary power supply provides efficient current sensing, while reducing the cost of the magnetic coupling element. The auxiliary power supply and current sense circuit both receive input from a secondary winding of a current sensing transformer having a primary winding coupled in series with the converter's main magnetic coupling element. To provide accurate sensing, the magnetization the current sensing transformer is accounted for. The magnetization is compensated for in the current sensing result, current sensing is performed during a part of the cycle in which charging of the auxiliary power supply is disabled, or the core of the current sensing transformer is made large, raising its mutual inductance. In another alternative technique, a circuit node can be pre-charged to a value that cancels the offset due to the magnetization current.

Journal ArticleDOI
TL;DR: In this article, new algorithms for detection of internal inter-turn faults in power transformers are described, which are extremely difficult to detect since they induce negligible increase of the currents at the transformer terminals, although the currents flowing at fault place are very high and dangerous for the transformer to be protected.

Journal ArticleDOI
I. Kartashev, T. Vontz1, H. Florian
TL;DR: In this paper, an attempt has been made to investigate the influence of temperature, mechanical and electrical field stress, properties of piezoceramic material and regimes of Piezoelectric transformer operation on the value of its power density.
Abstract: Piezoelectric transformers have a high potential for use in power supplies due to large power density and flexibility in design. A lot of work has been done in piezoelectric transformer design and analysis of their operation in different regimes and in different electronic circuits. In this paper an attempt has been made to investigate the influence of temperature, mechanical and electrical field stress, properties of piezoceramic material and regimes of piezoelectric transformer operation on the value of its power density. The results of the presented calculations of piezoelectric transformer parameters show a good correlation with measured data on experimental transformers. A substantial improvement of piezoelectric transformer power density seems feasible, making them more attractive for a wider range of applications in power supplies. In addition, useful guidelines for piezoelectric transformer design and selection criteria for piezoelectric materials for transformers have been established.

Patent
13 Feb 2009
TL;DR: In this paper, the excitation frequency is selected among a plurality of excitation frequencies in such a way that an equivalent load resistance, Req, is matched to an output impedance of the piezoelectric transformer so as to minimize power losses in the transformer.
Abstract: The present invention relates to an electronic power converter comprising a piezoelectric transformer, a drive circuit arranged to generate and provide an input voltage signal to the piezoelectric transformer, said input voltage signal comprising a burst frequency and a substantially constant excitation frequency, and a rectifier module. According to the present invention the excitation frequency is selected among a plurality of excitation frequencies in such a way that an equivalent load resistance, Req, is matched to an output impedance of the piezoelectric transformer so as to minimize power losses in the piezoelectric transformer. Moreover, the present invention relates to a method for configuring an electronic power converter.

Patent
18 Feb 2009
TL;DR: In this article, a reference transformer is coupled between the X inverters and output terminals of the power supply, is connected in parallel with the output terminals, and is configured to provide at least one of a neutral reference and a ground reference.
Abstract: A power supply includes an isolation transformer. The isolation transformer includes a primary winding and N secondary windings, where N is an integer. The primary winding receives a first alternating current voltage. Each of the N secondary windings generates a second alternating current voltage. M rectifiers convert the second alternating current voltages to a direct current voltage, where M is an integer. X inverters convert the direct current voltage to a third alternating current voltage, where X is an integer. A reference transformer is electrically coupled between the X inverters and output terminals of the power supply, is connected in parallel with the output terminals, and is configured to provide at least one of a neutral reference and a ground reference.

Proceedings ArticleDOI
01 Nov 2009
TL;DR: In this article, a new type of transformer, equipped with equal functions, however a simpler mechanism as compared with a conventional one, was proposed, termed the transformer a roof-delta connected transformer, which is expected to decrease costs by reducing quantity of winding.
Abstract: At Shinkansen substations in Japan that receive electric power from an extra-high voltage system, we have been using modified Woodbridge connected transformers for traction power supply since the inauguration of the Sanyo Shinkansen, which commenced commercial operations in March 1972 However, this transformer is of a rather complicated structure Therefore, we studied a new type of transformer, equipped with equal functions, however a simpler mechanism as compared with a conventional one We termed the transformer a roof-delta connected transformer since it has a roof-winding and a delta-winding The roof-delta connected transformer expectable to decrease costs by reducing quantity of winding We fabricated roof-delta connected transformers for trial at 66kV-voltage We performed various tests including measurement of neutral phase current Test results revealed that this transformer is applicable to the used in AC traction feeding system The first practical roof-delta connected transformer is going to be installed at a new Shinkansen substation constructed by JRTT JR East is also planning at present to install them at existing Tohoku and Joetsu Shinkansen substations for their renewal This paper describes the fundamental characteristics of the roof-delta connected transformer and the test results

Proceedings ArticleDOI
06 Nov 2009
TL;DR: In this paper, a step-up DC/DC converter topology for distributed power generation systems is presented, which utilizes the voltage fed quasi Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer and a voltage doubler rectifier.
Abstract: This paper presents a new step-up DC/DC converter topology intended for the distributed power generation systems. The topology utilizes the voltage fed quasi Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer and a voltage doubler rectifier. To increase the power density of the converter, implementation of the three-phase auxiliary AC-link (three-phase inverter and three-phase isolation transformer) and the three-phase voltage doubler rectifier are proposed by the authors. The paper describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.

Patent
07 Oct 2009
TL;DR: In this paper, a direct-current voltage reducing circuit is proposed, where the battery unit is connected with an energy storing inductor to form a voltage reducing discharge loop, and a control circuit controls state of the first and second switching elements to alternatively and repeatedly carry out synchronous switch-on and switch-off operation.
Abstract: The invention provides a direct-current voltage reducing circuit. Anode of a battery direct-current bus is sequentially connected with a second switching element, an energy storing inductor, a first switching element and cathode of the battery direct-current bus to form the energy storing circuit loop; cathode of a battery unit is connected with anode of a second diode, cathode of the second diode is connected with anode of a first diode through the energy storing inductor, cathode of the first diode is connected with anode of the battery unit, so as to form a voltage reducing discharge loop; a control circuit controls state of the first and the second switching elements to alternatively and repeatedly carry out synchronous switch-on and switch-off operation. The invention has advantages as follows: exchange between direct current and alternative current does not need, energy loss in voltage reducing process of isolating transformer is avoided, the circuit has simple structure, low cost and high efficiency; when the circuit is applied to management of balancing electric quantity of batteries connected serially, a battery unit is corresponding to a voltage reducing circuit, works independently and modularly and has high reliability; the control of voltage reducing proportion is flexible; standard and batch production can be realized.

Patent
Christoph Loef1, Peter Luerkens1
27 May 2009
TL;DR: In this paper, a high-voltage power supply circuit for inductively transmitting electrical energy from a stationary part to a load on a rotary part which requires a non- symmetrical voltage transfer, for example, an Xray tube of an X-ray computed tomography device.
Abstract: The present invention refers to a high-voltage power supply circuit for inductively transmitting electrical energy from a stationary part to a load on a rotary part which requires a non- symmetrical voltage transfer, for example, an X-ray tube of an X-ray computed tomography device. The circuit may be realized as a resonant-type power converter circuit with a single rotary power transformer (500) or more than one such power transformer, where at least two separate DC/AC power inverter stages provide two individually controllable AC input voltages (U1, U2) to different windings (511, 512) of a multi-primary coil belonging to the rotary power transformer. Two output voltages supplied by the multi-secondary coil (521, 522, 523, 524) of said transformer which are derived from the two individually controllable AC input voltages are fed to the tube electrodes for powering the X-ray tube.

Patent
21 Oct 2009
TL;DR: In this article, a system and method for providing isolated power to a component that is also subject a set of RF signals that includes at least a first RF signal having first RF frequency is provided.
Abstract: System and method for providing isolated power to a component that is also subject a set of RF signals that includes at least a first RF signal having a first RF frequency is provided. There is included providing a DC voltage signal and modulating the DC voltage signal into an isolated power signal using an isolation transformer. The isolated power signal has an intermediate frequency that is higher than 60 Hz and lower than the first RF frequency. There is included supplying the DC voltage signal to the primary winding and obtaining the isolated power signal from the secondary winding; and delivering the isolated power to the component using the isolated power signal.

Proceedings ArticleDOI
06 Nov 2009
TL;DR: In this paper, the authors proposed a novel topology for a three-phase high-frequency power electronic transformer, where two mutually-coupled primary windings and one secondary winding are used.
Abstract: In this paper, a novel topology for a three-phase high-frequency power electronic transformer is proposed. In each phase, there are two mutually-coupled primary windings and one secondary winding. On the high-voltage side of the transformer, only two controlled switches are required to create a three-phase high frequency ac link. This is a significant reduction in the required number of controlled high voltage semiconductor switches as compared to the present state-of-the-art, leading to simplicity, reliability and reduced system cost. A 3×3 matrix converter is used on the low-voltage side of the transformer. The matrix converter is modulated with the proposed space vector PWM to achieve the following features simultaneously: 1) grid power factor control, 2) load voltage of adjustable amplitude and frequency and 3) elimination of common-mode voltage at the load terminals. The simulation results of a 2 MVA system demonstrating the abovementioned capabilities of the proposed topology are presented.

Patent
Lateef A. Kajouke1
27 Mar 2009
TL;DR: In this paper, an AC grid voltage source is coupled to and inductor and a switching matrix, and the inductor is charged and the switching matrix is controlled to crate various current paths for the voltage across the inductors to add to the AC Grid voltage.
Abstract: Apparatus for unity power factor, isolated, single phase switch matrix converter/battery charger is provided. In one implementation, An AC grid voltage source is coupled to and inductor and a switching matrix. The inductor is charged and the switching matrix is controlled to crate various current paths for the voltage across the inductor to add to the AC grid voltage. The boosted AC grid voltage flow across an isolation transformer to be rectified and used to charge a battery matrix for an electric powered vehicle.

Patent
13 Mar 2009
TL;DR: In this paper, the problem of how to drive an auxiliary machine even when the power of a stringing is stopped, and to suppress energizing inrush currents of a main transformer from the stringing was solved.
Abstract: PROBLEM TO BE SOLVED: To drive an auxiliary machine even when the power of a stringing is stopped, and to suppress energizing inrush currents of a main transformer from the stringing. SOLUTION: In a railroad vehicle system, the power is supplied from an electrical storage device 17 to secondary windings 12a, 12b via electrical power converters 14a, 14b so that the primary side of the main transformer 6 has the stringing voltage/phase, and the main transformer 6 is inversely excited by using the secondary windings 12a, 12b. By connecting the main transformer 6 in which the voltage of the same phase and the same level as those of the stringing voltage is applied to the primary side to a stringing 1, the energizing inrush currents of the main transformer 6 is suppressed. When the power of the stringing is failed, an auxiliary machine 8 is driven by the power of the electrical storage device 17. The power of the electrical storage device 17 is accumulated by the regenerative energy of driving motors 7a, 7b. A power supply control device 10 changes the power supply of the electrical storage device 17 for the inverse excitation of the main transformer 6 or the power supply for driving the auxiliary machine 8. The power supply control device 10 determines whether the power failure from the stringing is caused by a changing section or by the power failure of a power transformation station. COPYRIGHT: (C)2010,JPO&INPIT

Patent
05 Aug 2009
TL;DR: In this article, a grid-connected photovoltaic power generating system based on a novel direct current converter and a working method of the grid connected PV power generation system is presented.
Abstract: The invention provides a grid-connected photovoltaic power generating system based on a novel direct current converter and a working method of the grid-connected photovoltaic power generating system. The grid-connected photovoltaic power generating system is characterized in that the grid-connected photovoltaic generating power system consists of a direct current converter, a grid-connected inverter, an isolation transformer and a control circuit; the working method comprises the steps as follows: 1. collecting signal; 2. MPPT module data processing; 3 applying an MPPT arithmetic; 4 inverter module data processing; 5. applying a grid-connected arithmetic; and 6. applying SPWM arithmetic. The grid-connected photovoltaic power generating system and the working method thereof have the advantages of small technical realization difficulty, obviously reducing the cost, flexible installation, convenient maintenance, high voltage and current detection precision, advanced control arithmetic, quick running speed of control chip, the system being capable of obtaining excellent tracking precision and stability, combining the hardware device with the software programming of a digital signal processor, simple design, low cost and easy realization of the hardware device, brief and understandable software programming arithmetic.

Proceedings ArticleDOI
01 Nov 2009
TL;DR: In this article, an electronic three-phase switching controller has been designed and some thyristors were used for switching power to the transformers to reduce the transient inrush currents.
Abstract: At the time of transformer energization, a high current will be drawn by the transformer. The mentioned current is called transient inrush current and it may rise to ten times the nominal full load current of transformer during operation. Energization transients can produce mechanical stress to the transformer, causes protection system malfunction and it often affect the power system quality and may disrupt the operation of sensitive electrical loads such as computers and medical equipment connected to the system. Reduction and the way to control of energization transients currents have become important concerns to the power industry for engineers. One of the methods to reduce inrush current is use of point on wave switching at the time transformer is initially connected to supply. This paper discusses the simulations and the experimental results on a three-phase transformer for reduction of inrush currents. An electronic three-phase switching controller has been designed and some thyristors were used for switching power to the transformers.

Proceedings ArticleDOI
19 Jul 2009
TL;DR: In this article, the authors discuss the possibility effect of harmonic phenomenon due to degradation process of transformer insulation system based on Dissolved Gas Analysis (DGA) and power quality analysis.
Abstract: Harmonic is one of common phenomenon occurred during power system operation, especially when the non linear load applied within the power system. These harmonic will affect to the transformer, such as increasing hysteresis losses (magnetization) on steel and iron of transformer core, where the value is temperature depended. Degradation of transformer insulation can be driven by this temperature increasing. The harmonic that monitored continuously can be use as a reference parameter of degradation level of transformer insulation. To determine the actual condition of transformer insulation we developed Dissolved Gas Analysis (DGA) to enrich data analysis and using power quality monitoring to determine the power condition. This paper will discuss the possibility effect of harmonic phenomenon due to degradation process of transformer insulation system based on DGA and power quality analysis.