Abstract: An apparatus is provided for securing to and collecting power from an electrical conductor, including a current transformer comprising a core and an electrical winding that receives an induced current from magnetic flux generated according to alternating current present on the electrical conductor, and a clamping mechanism that attaches the apparatus to the electrical conductor. According to various aspects, apparatus may include a housing that encloses circuitry for monitoring conditions of the electrical conductor, where the circuitry includes one or more sensors, and wireless communications circuitry.

Abstract: This article presents a survey on failures, monitoring, and new trends of power transformers. There are three main types of power transformers, namely, oil immersed, gas-insulated, and dry-type transformers with or without cast coil insulation system. Operating stresses of power transformers have increased due to the load growth and the increased bulk power transactions, where recent and imminent alternating current (AC) systems are rated 1,100 kV and 1,200 kV, respectively. Failures of windings, onload tap changers (OLTC), and bushings are the main defective components as they represent about 84% of the failure statistics. Online and offline diagnostic monitoring of power transformers can be used to detect faults at an early stage, prevent degeneration into catastrophic phenomena, and monitor the aging process of the insulating systems. Many of the well-known preventive maintenance techniques are discussed. New trends of power transformers have recently taken many steps forward in different dimensions, e.g., Powerformer, Dryformer and Windformer utilizing high-voltage (HV) cross-linked polyethylene (XLPE) cables, gas-insulated transformers (GIT), converter transformers rated ±800 kV, and high-temperature super conducting (HTS) transformers. The latter type represents a key technology for future power systems engineering as they offer many advantages over the others.

Abstract: A simple rectifying circuit for an isolated two-channel LED driver without active current-sharing control is proposed. An alternating current source can be used to generate a two-channel LED driver with the proposed rectifying structure. With the proposed H-bridge rectifier and a block capacitor in series with the secondary side winding of the transformer, the currents in two LED strings are shared automatically even for different LED strings with different voltage drops. The operation principle of the rectifier is analyzed with a sinusoidal current source, and it is verified with a series-parallel resonant (LLC) dc/dc converter. This proposed rectifier can be applied to other converters featuring a high-frequency current source link.

Abstract: Today's power systems use alternating current (ac) for transmission and distribution of electrical energy, although the first grids were based on direct current (dc). Due to the absence of appropriate equipment to change voltage levels dc technology did not become widely accepted and was finally ruled out by the more efficient ac infrastructure. However, as a result of considerable technical progress, high-voltage direct current (HVDC) transmission has found its way back into power systems. At lower voltage and power levels medium-voltage dc (MVDC) distribution has been proposed for offshore wind farms and industrial applications. This paper describes the design of an MVDC grid for the interconnection of high-power test benches at a university campus. Voltage control within the dc grid as well as the behavior in different fault scenarios is analyzed using numerical simulations. To assess the environmental impact of the grid the magnetic flux density emitted by the dc cable lines is calculated.

Abstract: Increased electrical power demands are being experienced on the new generation of aircraft due to an increased reliance on electrical technology such as air conditioning, de-icing systems and electrical flight control actuation. Distribution of power at higher voltages is therefore now being seen in modern aircraft to avoid the penalties incurred due to high wire weights. Voltages have increased past the minimum of Paschen's law resulting in a risk that life limiting partial discharge damage can occur in the insulation systems. This study uses a theoretical analysis backed by experimental results to investigate the optimal operating voltage of a wiring system. In addition it proposes a methodology for optimising the operating voltage level based on an analysis of the power carrying capability of wiring within a fixed volume system and the derivation of the wire weight as a function of voltage. The work done has shown that the optimal operating point for an aircraft power system does not imply the use of the highest voltage possible. A trade-off between wire weight and power transfer is required and furthermore the use of direct current systems can result in higher power transfers than conventional three phase/400 Hz alternating current (AC) systems.

Abstract: According to one exemplary embodiment, a power transmitting apparatus is provided with: a plurality of resonators configured to resonate at resonance frequencies which differs from one another, respectively; a plurality of exciters each configured to cause an associated one of the plurality of resonators to excite alternating current; and a controller configured to drive at least one of the plurality of exciters.

Abstract: Investigation of the electric properties of semi-conducting materials in an applied ac electric fields gives information about the nature of charge transport and localized states in the forbidden gap. Layered crystals usually contain structural defects, such as dislocations and vacancies that may form a high density of localized states near the Fermi level. So, the current study was carried out for insight into the dielectric Properties of Tl2S layered single crystals. These properties were studied using the ac measurements in the low temperatures ranging from 77 to 300 K. The real part of dielectric constant e?, imaginary part of dielectric constant e?, the dissipation factor tan δ and the alternating current conductivity σac were measured in an applied ac electric field of frequencies extending from 2.5 to 50 kHz. Based on the dependencies of these dielectric parameters on both the frequency and temperature, the dielectric properties of the crystals under investigation were elucidated and analyzed. The ac conductivity was found to obey the power law σac(ω) = Aωs with which the values of the exponent s were evaluated to be less than unity in the range 0.21 ≥ s ≥ 0.19. Furthermore, it was found that the temperature dependence of ac conductivity follows the Arrhenius relation via which the impact of temperature on the electrical processes in an applied ac electric field was illustrated and analyzed. The influences of temperature and frequency on both the exponent s and band gap were also discussed in this investigation.

Abstract: AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors are currently investigating the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in coils made from YBCO superconductors. In this paper, a 2D finite element model based on the H formulation is introduced. The model is then used to calculate the trans port AC loss using both a bulk approximation and modeling the individual turns in a racetrack-shaped coil. The coil model is based on the superconducting stator coils used in the University of Cam bridge EPEC Superconductivity Group's superconducting permanent magnet synchronous motor design. The transport AC loss of a stator coil is measured using an electrical method based on inductive compensation using a variable mutual inductance. The simulated results are compared with the experimental results, verifying the validity of the model, and ways to improve the accuracy of the model are discussed.

Abstract: The invention belongs to the technical field of distributed power generation microgrid systems in power systems and relates to a wind-solar-diesel storage isolated microgrid system which comprises a lead-acid battery, one group or multiple groups of photovoltaic battery arrays, a fan, a diesel generator, a microgrid monitoring sub-system, a controllable load and an uncontrollable load, wherein the fan comprises more than one wind turbine generator or more than one group of wind turbine generator set, the lead-acid battery and the photovoltaic battery arrays are merged into a direct current bus bar through all front-stage two-way DC (direct current)/DC converters and connected into an alternating current bus bar through a two-way DC/AC (alternating current) inverter, the diesel generator is merged into the direct current bus bar through an AC/DC current converter, the wind turbine generator set is connected into the alternating current bus bar through an AC/DC/AC converter, the microgrid monitoring sub-system is used for controlling voltage and the frequency in a microgrid to be stable. The invention simultaneously provides a coordinated operation control method for the system. Thewind-solar-diesel storage isolated microgrid system has stronger robustness and flexibility, and can meet the long-term high-efficient stable operation requirement of the isolated microgrid system.

Abstract: A portable power supply apparatus is provided having reduced impedance losses. The portable power supply apparatus is comprised of: a portable housing; a battery system residing in the housing; and an inverter circuit residing in the housing. The battery system generates a direct current (DC) voltage having a magnitude greater than or equal to a peak value of a desired alternating current (AC) voltage. The inverter circuit receives the DC voltage directly from the battery system, converts the DC voltage to an AC output voltage and outputs the AC output voltage to one or more outlets exposed on an exterior surface of the portable housing.

Abstract: An apparatus, system, and method includes a housing having at least one inlet plug suitable for connection to an alternating current (AC) power outlet and at least one outlet receptacle suitable receiving an AC plug connected to a load device. An AC measurement module is contained within the housing and is coupled to the inlet plug and the outlet receptacle to measure AC voltage and AC current usage of the load device connected to the outlet receptacle. A communication module is operative to transmit AC power values calculated based on the measured AC voltage and AC current in accordance with the IEEE 802.11 wireless networking standard (Wi-Fi) to a wireless network access point.

Abstract: The invention provides a wind energy and solar energy grid-connected generation system and a control method thereof. The wind energy and solar energy grid-connected generation system comprises a generation unit, an inversion unit, a grid-connecting unit, a main control unit and a detection unit. Each unit is effectively controlled by an integrated control unit which is formed by a digital signal processor (DSP), and operating state parameters of the system are predicted by a neural network, so the defect that the grid-connected system changes due to execution delaying of a control instructionis overcome, and the operating stability of the system is improved. Island detection adopts an active and passive detection mode, so the capacity for anti-island operation of the system is improved. The invention has the advantages that: inverted electric energy is supplied to an electricity grid and can be locally supplied to local alternating current and direct current loads, so the load pressure of the electricity grid is reduced, and the capacity for stable operation of the electricity grid can be improved; and when the output electric energy of the system is smaller than a local load, the electricity grid can supply power to the local load of the system, so the local load is supplied with power doubly by power supplies of the system and the electricity grid, and the time for uninterrupted power supply of the power supplies is prolonged.

Abstract: The invention discloses a coordination control and optimization method for battery energy accumulation and photovoltaic power generation based on a co-direct current bus in synchronization and independent operation modes, which supports the access of various types of storage batteries and photovoltaic battery boards through the free combination of the co-direct current bus of a DC (Direct Current)/DC converter, the automatic intelligent charge-discharge management of a storage battery branch and the maximum power tracing management of a photovoltaic battery board branch, wherein the branches are completely independently controlled to realize optimization management; the energy collected by a direct current bus is interacted with the energy of a power grid or an independent load through a post DC/AC (Alternating Current) converter; the DC/AC converter adopts a method for carrying out directional vector control on the voltage of the power grid and modulating the space vector pulse widthof the voltage in the course of the synchronization operation in an active and reactive complete decoupling control mode; and V/f control is adopted in the course of the independent operation to provide a constant voltage and frequency reference to an alternating current bus. The result of an experiment proves that the invention can realize the coordination complementary control and the autonomous optimization management of photovoltaic power storage and has the advantages of good generality, practicality and application prospects.

Abstract: The invention relates to a vehicle-mounted charging system of an electric vehicle, comprising a vehicle-mounted battery, a single/three-phase power conversion module, a direct current charging device, a charging contactor, a signal detection unit and a micro control unit (MCU), wherein the single/three-phase power conversion module, the direct current charging device, the charging contactor, the signal detection unit and the MCU are respectively connected with the vehicle-mounted battery; the direct current charging device comprises a voltage boosting module and a voltage reduction module which can charge the vehicle-mounted battery through boosting or reducing the voltage of an external direct current charging power supply; and the single/three-phase power conversion module directly multiplexes a vehicle-mounted inverter of the electric vehicle with an alternating/direct current bidirectional inversion function. In the invention, three charging modes of the electric vehicle are integrated in one vehicle-mounted charging system and are flexible and selectable, the vehicle-mounted charging system can be charged by three different charging voltages, i.e. external direct current voltage, single-phase alternating current voltage and three-phase alternating current voltage, and four alternating current charging modes can meet the diversity requirement of the charging modes of current electric vehicles; and meanwhile, the original vehicle-mounted inverter components can be multiplexed, thereby effectively reducing the cost.

Abstract: A wireless power transmitting apparatus ( 10 ) is a wireless power transmitting apparatus which transmits electric power in a wireless manner by electromagnetic induction to a power receiving apparatus ( 20 ) which is provided with a power reception coil ( 220 ) and a fixed capacitance capacitor ( 230 ) electrically connected in parallel with the power reception coil. The wireless power transmitting apparatus is provided with: an alternating current power supply ( 110 ) which generates alternating current power; a power transmission coil ( 120 ) which is electrically connected to the alternating current power supply; a variable capacitance capacitor ( 130 ) which is electrically connected in series with the power transmission coil; and a capacitance controlling device ( 140 ) which controls a capacitance value of the variable capacitance capacitor to reduce a phase difference between a voltage phase and a current phase of the alternating current power.

Abstract: The invention discloses a solar photovoltaic and commercial power combined power supply system and a control method thereof, and belongs to the field of new energy power supply systems. The structure of the system comprises a photovoltaic array, a commercial power supply, a DC/DC converter, a PFC converter and a DC/AC inverter, wherein the photovoltaic array and the commercial power supply are connected with a direct current bus through the DC/DC converter and the PFC converter respectively and supply power to an alternating current load through the DC/AC inverter. In the invention, for fullyutilizing solar, the DC/DC converter can operate with the maximum power of a photovoltaic battery; meanwhile, the commercial power is used as an auxiliary power supply, three power supply modes are realized, and the stable work of the load under various conditions is ensured.

Abstract: An adaptive bleeder circuit is applicable to a power converter, in which the power converter has a transformer primary side and a transformer secondary side, and the power converter enables input power to be selectively input or not input to the transformer primary side through a pulse-width-modulated signal. The adaptive bleeder circuit includes a switched bleeder circuit, and the bleeder circuit switch dynamically adjusts a turn on/off ratio (or referred to as duty ratio) of the switch element according to the TRIAC holding current and the converter input current of an alternating current (AC) TRIAC. When the input current is less than the holding current, the bleeder circuit increases conduction time ratio of the pulse-width-modulated signal, such that the input current recovers to the holding current to maintain normal conduction of the AC TRIAC.

Abstract: Various methods and apparatus are described for a photovoltaic system. In an embodiment, pluralities of three-phase Alternating Current (AC) inverter circuits electrically connect into a common three phase AC output. Each of those inverters receives a bipolar DC voltage supplied from its own set of Concentrated PhotoVoltaic (CPV) modules.

Abstract: In this paper, research on the comparison of the fault characteristics of the direct current (DC) distribution system and the alternating current (AC) distribution system has been conducted. Since the DC distribution system is a promising topology to be used in future smart distribution systems having high efficiency and reliability, it is expected that there would be an increase in the installation of DC distribution systems in houses and buildings. For the analysis, DC and AC networks to be analyzed are implemented using PSCAD/EMTDC. Simulation results show that the DC distribution system has several benefits compared to the regular AC distribution system such as improved voltage drop and power quality characteristics at the customer-end during a disturbance. This is because the DC/DC converters of DC distribution system can mitigate voltage fluctuations caused by disturbance and increase power quality.

Abstract: A power interchange system for interchanging electric energy between a battery and an electric grid is provided The power interchange system includes a rectifier unit for converting alternating current of the electric grid into direct current for charging the battery; a grid measurement device for measuring an electric parameter of the electric grid, and a controller unit for adjusting the direct current for the charging the battery as a function of the electric parameter of the electric grid. Moreover a method for interchanging electric energy between a battery and an electric grid is provided.

Abstract: The invention relates to the technical field of high voltage and insulation, in particular to a device for researching and testing an insulating property of high-voltage oiled paper. Aiming at the positions of frequent faults during the operation of a converter transformer, the device simulates a ball-board, a needle-board, a board-board, faces and suspension discharge electrode models; and the typical high-voltage oil/oiled paper insulating experiments can be realized under direct current (DC) voltage, alternating current (AC) voltage and AC-DC voltage so as to acquire partial discharge characteristics and breakdown characteristics of the major insulation of the converter transformer.

Abstract: Micro-inverters convert direct current (DC) from a single solar panel to alternating current (AC). They have several advantages over conventional string inverters like higher maximum power point tracking efficiency, easier installation and longer lifetime. For the control of micro-inverter, boundary current mode (BCM) is chose to improve the efficiency while discontinuous current mode (DCM) is used to limit the switching frequency. If the switching frequency in DCM is constant, the switching loss will play a more significant role in the overall power loss at light load condition. In this paper, the effect of the DCM/BCM control and frequency limitation to the efficiency and output performance is analyzed first. Then a variable switching control method is proposed to reduce the switching loss under different PV panel's output power level and input/output voltage changes. Simulation and a 120W prototype's experimental results validated the proposed control method.

Abstract: A power converter circuit may convert alternating current signals into direct current signals. A load may be powered from output terminals that are provided with the direct current signals. The power converter circuit may have a transformer with primary and secondary sides. A transistor on the primary side may be controlled using a pulse width modulation controller. A diode may be coupled in series with the secondary side of the transformer and the load. To improve efficiency at larger load currents, a synchronous rectifier control circuit may modulate a transistor on the secondary side that is coupled in parallel with the diode. The synchronous rectifier control circuit may monitor voltage pulses on the transistor on the secondary side or may make direct load current measurements to ascertain how much load current is flowing. Under low or no load conditions, synchronous rectification can be inhibited to improve efficiency.

Abstract: An electric vehicle charging station is described. The charging station includes an input connector configured for coupling with an alternating current (AC) power source and an output connector configured for coupling with an electric vehicle. The charging station also includes a variable-output transformer comprising a primary side and a secondary side. The primary side is coupled to the input connector and the secondary side is coupled to the output connector and configured to be in selective electromagnetic communication with an energy storage device associated with the electric vehicle. The charging station also includes a controller coupled to the transformer and configured to determine a level of voltage to provide to the electric vehicle.

Abstract: An inductive power transfer (IPT system) includes an AC-AC full-bridge converter (T p1 -T p4 ) provided between the primary conductive path (L pt ) and an alternating current power supply (V in ). The system may include a controller for controlling the pick-up device to shape the input current drawn from the alternating current power supply (V in ).

Abstract: Provided is an electric outboard motor that includes a drive motor, which is an AC motor, as a drive source. The electric outboard motor includes: an outboard motor main body that includes the drive motor and an inverter that converters a direct current to an alternating current to supply the alternating current to the drive motor; a control/power supply unit that is formed separately from the outboard motor main body and that can supply the direct current to the inverter; and a connection cable that electrically connects the outboard motor main body and the control/power supply unit. The inverter and the drive motor are stacked and arranged in an axial direction of a rotation output axis of the drive motor. Part of the inverter falls within an outline of the drive motor in a view in the axial direction of the rotation output axis of the drive motor.

Abstract: A solar power inverter that detects islanding conditions includes a power generation component that generates alternating current (AC) from direct current produced by photovoltaic cells. The inverter generates AC for a load or an electrical power grid. The inverter also includes a component that generates synchrophasors from characteristics of electrically proximate AC. The inverter further includes a component that receives grid synchrophasors transmitted from a location on the electrical power grid (e.g., a transmission substation). The inverter further includes a controller that uses the inverter synchrophasors and the grid synchrophasors to calculate a degree of correlation between the electrical power grid AC frequency and the frequency of the electrically proximate AC. If the degree of correlation dips below a predefined value or exhibits certain patterns or behaviors that are indicative of a loss of mains (e.g., a loss of main power along the electrical power grid), the controller can cause the power generation component to stop generating AC or cause the inverter to intentionally island by electrically disconnecting from the electrical power grid.

Abstract: A contactless power transfer system, including a coil configured to supply or receive power contactlessly via magnetic coupling, a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, and a smoothing capacitor connected between the DC terminals. A load is connectable to either end of the smoothing capacitor. One of the AC terminals is connected to one end of the coil via a first capacitor. The other of the AC terminals is connected to the other end of the coil. The bridge circuit includes two serially-connected circuits each having upper and lower arms, each arm having a semiconductor switch and a diode in reverse parallel connection. A second capacitor is connected in parallel to the semiconductor switch of an upper arm, or of a lower arm, or to two semiconductor switches respectively of an upper arm and of a lower arms, of the bridge circuit.