Abstract: This paper presents the measurement and simulation of Alternating Current (AC) losses on the Stabilizer-free and Copper Stabilizer High Temperature Superconducting (HTS) Tapes: SuperPower SF12100 and SCS12050. The AC loss measurement utilised electrical method to obtain overall losses with AC transport currents. The 2D H-formulation by COMSOL Multiphysics has been used to simulate the real geometry and multi-layer HTS tapes. Ferromagnetic AC losses of substrate have been assumed to be ignored as the substrates of SF12100 and SCS12050 are non-magnetic. Hysteresis AC losses in the superconducting layer, and eddy-current AC losses in copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from simulation, with 3 cases of different AC frequency 10, 100, and 1000 Hz. The eddy-current AC losses of copper stabilizer at frequency 1000 Hz were determined from both experiment and simulation. The estimation of AC losses with frequency at 10,000 Hz was also carried out using simulation method. Finally, the frequency dependence of AC losses from Stabilizer-free Tape and Copper Stabilizer Tape were compared and analysed.

Abstract: A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of discharges, were investigated using simultaneously optical and electrical diagnostics. The glow-type discharge shows sinusoidal-like voltage and current waveforms with a peak current of hundreds of milliamperes. The frequency of the emission intensity variation of the glow-type discharge is the same as that of the electronic power dissipated in the plasma column. The glow-type discharge can transfer into a spark discharge characterized by a sharp peak current of several amperes and a sudden increase of the brightness in the plasma column. Transitions can also be found to take place from spark-type discharges to glow-type discharges. Short-cutting events were often observed as the intermediate states formed during the spark-glow transition. Three different types of short-cutting events have been observed to generate new current paths between two plasma channel segments, and between two electrodes, as well as between the channel segment and the electrodes, respectively. The short-cut upper part of the plasma column that was found to have no current passing through can be detected several hundreds of microseconds after the short-cutting event. The voltage recovery rate, the period of AC voltage-driving signal, the flow rates and the rated input powers were found to play an important role in affecting the transitions among the different types of discharges.

Abstract: Isolated modular multilevel dc–dc converter (IMMDCC), which consists of two modular multilevel converters and a medium-frequency transformer, is attractive for medium-voltage applications because of the following features: the modular structure can handle higher voltage, and synthesizing square-wave voltages toward the alternating current (ac) link increases the dc voltage utilization ratio and achieves the zero-voltage switching operation. However, the asymmetry of arm impedance in practice inevitably leads to power imbalance and divergence of total capacitor voltages in the upper and lower arms of IMMDCC, thereby inducing large ripples in the common-mode arm current and adding a dc bias to the synthesized ac voltage. To compensate for the power imbalance and maintain the stable operation, the interarm phase-shift modulation (IAPSM) scheme and arm voltage-balancing control strategy based on this scheme are presented in this paper. Combining the IAPSM scheme with the intersubmodule phase-shift modulation scheme, deep rising and falling edges of the synthesized square-wave voltage in each phase leg are modified into staircase waveforms with 2 N + 1 steps, dv/dt in the ac-link is thus significantly reduced. Simulation and experimental results validate the theoretical analysis and control strategy.

Abstract: At present, the changing structure, material and increasing device are used to suppress the vibration of motor in general. These methods increase system complexity in the different degree. So a novel vibration suppression method based on fractional order Proportional-Integral-Derivative (PID) controller is proposed in this article. First, the digital realization process of fractional order PID controller is illustrated in detail. Then the integer order PID controller and fractional order PID controller are, respectively, used to adjust the input current of inverter to control the 1.5 kW alternating current motor. The vibration frequency spectrums and stator current frequency spectrums in low-frequency and carrier frequency band are, respectively, studied by using the comparison and analysis methods. At the same time, the vibration frequency spectrum and stator current frequency spectrum of 15 kW alternating current motor are compared and analyzed. And the frequency spectrums near the rotating frequency of...

Abstract: Quantitative characterization of a high-power glow-mode gliding arc (GM-GA) discharge operated in open air is performed using a current-voltage lumped model that is built from the perspective of energy balance and electron conservation. The GM-GA discharge is powered by a 35 kHz alternating current power supply. Instantaneous images of the discharge volume are recorded using a high-speed camera at a frame rate of 50 kHz, synchronized with the simultaneously recorded current and voltage waveforms. Detailed analyzation indicates that the electrical input power is dissipated mainly through the transport of vibrationally excited nitrogen and other active radicals (such as O). The plasma is quite non-thermal with the ratio of vibrational and translational temperatures (Tv/Tg) larger than 2 due to the intense energy dissipation. The electron number density reaches 3 × 1019 m−3 and is always above the steady value owing to the short cutting events, which can recover the electron density to a relatively large val...

Abstract: The saturated core fault current limiter (SFCL) is one of the most effective methods for limiting fault current. A permanent magnet (PM)-biased SFCL (PFCL) can reduce dc bias current and additional energy consumption. However, the thermal stability of NdFeB PMs in PFCL poses a major challenge. This paper proposes a novel hybrid-type SFCL (HSFCL) topology that can reduce this risk. In the HSFCL, a hybrid PM/dc coil is designed to saturate the core, and a fault-limiting reactor is used to guarantee fault-clipping performance. The new structure provides air-gap branches for the time-varying magnetic field produced by alternating current, which reduces the eddy current in the PMs and enhances their stability. Electromagnetic coupling is used to analyze the operating principles and characteristics of HSFCL. Finite-element analysis simulations were performed using Maxwell and compared with verification experiments, proving that HSFCL is efficient in fault clipping and PM reliability enhancement.

Abstract: The present invention relates to a battery energy storage system including: a plurality of battery boxes provided with a plurality of battery packs; a plurality of power converter systems respectively connected to the plurality of battery boxes to selectively charge or discharge the plurality of battery boxes through alternating current supplied from an external power source device; a transformer disposed between the external power source device and the plurality of power converter systems; and a controller controlling the plurality of power converter systems to selectively charge or discharge the plurality of battery boxes.

Abstract: Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage and an increasing prevalence of end uses operating internally on DC. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. A variety of parametric simulations determine how and when DC distribution proves advantageous. This work shows that using DC distribution can be considerably more efficient than AC: a medium office building using DC distribution has an expected baseline of 11% savings, but may save up to 17%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building with enough battery storage to act as an islanding microgrid. DC is generally most advantageous in buildings with large solar capacity, large battery capacity, and high voltage DC distribution. In addition, based on the efficiency modeling results, a comparison of the economic performance of DC vs. AC distribution systems in commercial buildings is conducted. The results for the baseline scenario show that DC distribution systems in buildings can be cost effective when PV generation and battery storage are included in the building.

Abstract: Galloping-based piezoelectric energy harvesters scavenge small-scale wind energy and convert it into electrical energy. For piezoelectric energy harvesting with the same vibrational source (galloping) but different (alternating-current (AC) and direct-current (DC)) interfaces, general analytical solutions of the electromechanical coupled distributed parameter model are proposed. Galloping is theoretically proven to appear when the linear aerodynamic negative damping overcomes the electrical damping and mechanical damping. The harvested power is demonstrated as being done by the electrical damping force. Via tuning the load resistance to its optimal value for optimal or maximal electrical damping, the harvested power of the given structure with the AC/DC interface is maximized. The optimal load resistances and the corresponding performances of such two systems are compared. The optimal electrical damping are the same but with different optimal load resistances for the systems with the AC and DC interfaces. At small wind speeds where the optimal electrical damping can be realized by only tuning the load resistance, the performances of such two energy harvesting systems, including the minimal onset speeds to galloping, maximal harvested powers and corresponding tip displacements are almost the same. Smaller maximal electrical damping with larger optimal load resistance is found for the harvester with the DC interface when compared to those for the harvester with the AC interface. At large wind speeds when the maximal electrical damping rather than the optimal electrical damping can be reached by tuning the load resistance alone, the harvester with the AC interface circuit is recommended for a higher maximal harvested power with a smaller tip displacement. This study provides a method using the general electrical damping to connect and compare the performances of piezoelectric energy harvesters with same excitation source but different interfaces.

Abstract: A survey of methods of calculating losses has been proposed for a class of controlled ac drivers that work under extreme conditions with arbitrary control laws of currents and configurations of magnetic systems for electrical machines. It is shown that the existing methods have low calculation accuracy for the considered class of electric drivers (error up to 30%). The results of calculations by the finite-element method and the experimental data of simulations of thermal conditions and losses using 3D models, in which an electromechanical converter is regarded as a system with distributed parameters, have been considered; moreover, the parallel calculating algorithms have been used. For example, the calculations of losses in the 3D models of a field-regulated reluctance machine have shown that the discrepancy with the experimental data is not higher than 2%. Note that the main share of losses in steel is eddy currents. The results of calculations by numerical methods using 3D models allow one to determine the losses in controlled ac drivers for nonsinusoidal control laws of phase current of the stators with complex configurations of the magnet system of the electromechanical converter. For the considered class of electric drivers, the largest share of losses (from 60 to 80%) is eddycurrent losses.

Abstract: The availability of the electricity in doing a job lead to a dependency on it If there is a sudden failure on electricity, it will result in unfinished works To overcome the undesired situation because of wasting time, it is advisable to have your power supply The power supply can serve to replace electricity temporarily, or it could be as a replacement for power supply of PLN’s (State Electricity Company) electricity nets to meet the daily electricity needs Backup power available can sufficiently replace the source of PLN’s electricity nets with the output of square wave to the ordinary electricity needs The type of the intended power supply is inverter system as a backup system that supplies daily electricity In this case, it aims to change the DC (direct current) to AC (alternating current) voltages

Abstract: Recording electrodermal activity is a well-accepted physiological measurement for clinical approaches and research. Historically, applying a DC (direct current) signal to the skin to measure the conductance is the most common practice for exogenous recordings. However, this method can be subject to error due to electrode polarization even with "nonpolarizing" electrodes-a problem that can be eliminated with alternating current (AC) methodology. For that reason, Boucsein et al. () called for research demonstrating an AC method that is validated by comparison to standard DC methodology. Additionally, the complex structure of human skin has electrical properties that include both resistance and capacitance, and AC recording enables the measurement of skin susceptance (associated with current flow through capacitors). Finally, AC recording permits the simultaneous recording of the endogenous skin potential. In this paper, the results from a direct comparison between both methods are presented, which has not been reported previously. The results demonstrated excellent agreement between a 20 Hz AC method and a standard DC method, supporting the validity of the AC recording methodology employed. The results also showed that an applied voltage of 0.2 V is sufficient for DC recordings.

Abstract: In recent years, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We use this model to derive an optimization problem that protects power systems from GIC impacts through line switching, generator redispatch, and load shedding. We employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and the UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of optimal switching decisions with respect to GMD direction.

Abstract: The invention relates to a transformer area and access phase automatic recognition system and method. The transformer area and access phase automatic recognition system comprises a three-phase carrier module and a single-phase carrier module, and is characterized in that the three-phase carrier module is installed at a concentrator end, and the single-phase carrier module is installed at a user meter end. Each module is composed of a zero-crossing detection unit, an electric power carrier communication unit and a microcontroller. The three-phase carrier module comprises a three-phase electric power carrier communication unit and a corresponding zero-crossing detection unit. The electric power carrier communication unit is used for transmitting electric power carrier signals, and the zero-crossing detection unit is used for detecting a zero-crossing moment of low-voltage alternating current. Based on a phenomenon of phase deviation existing in alternating current mains supply on a low-voltage electric power line between different transformer areas and between different phases, the transformer area and access phase automatic recognition method can effectively solve a circumstance of belonging transformer area and access phase misjudgment caused by crosstalk between transformer areas and high-frequency signal interphase coupling, so that the probability of carrier signal transmission failure caused by noise interference is reduced.

Abstract: Inverter systems that feed electrical power from photovoltaic (PV) system into the grid must convert the direct current of the PV array into the alternating current of the grid. In many applications, it is important for a converter to be lightweight, highly reliable, input/output isolated, flexible and operable in a boost mode. These features can be achieved by using a High-Frequency inverter which involves an isolated DC-DC stage and DC-AC section, which provides AC output. This paper proposes a new three phase topology, based on multi stage converter and PV system in order to use in medium and high power applications. The Perturb and Observe (P&O) method is used for maximum power point tracking (MPPT) control of PV array. The switching control signals for three-phase inverter are provided by hysteresis control method. Also, the comparison between the proposed topology and traditional structures has been conducted and finally the simulation researches are performed in a closed-loop control system by MATLAB/Simulink software to verify the operation of the proposed structure. The results represent better performance of the introduced system over traditional topologies.

Abstract: Commutation failure is a common fault for line-commutated converters in the inverter. To reduce the possibility of commutation failure, many prediction algorithms based on alternating current (AC) voltage detection have already been implemented in high voltage direct current (HVDC) control and protection systems. Nevertheless, there are currently no effective methods to prevent commutation failure due to transformer excitation surge current. In this paper, an improved commutation failure prediction algorithm based on the harmonic characteristics of the converter bus voltage during transformer charging is proposed. Meanwhile, a sliding-window iterative algorithm of discrete Fourier transformation (DFT) is developed for detecting the voltage harmonic in real time. This method is proved to be an effective solution, which prevents commutation failure in cases of excitation surge current, through experimental analysis. This method is already implemented into TianShan-ZhongZhou (TianZhong) ± 800 kV ultra high voltage direct current (UHVDC) system.

Abstract: The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

Abstract: Multi-terminal high voltage direct current transmission based on voltage source converter (VSC-HVDC) grids can connect non-synchronous alternating current (AC) grids to a hybrid alternating current and direct current (AC/DC) power system, which is one of the key technologies in the construction of smart grids. However, it is still a problem to control the converter to achieve the function of each AC system sharing the reserve capacity of the entire network. This paper proposes an improved control strategy based on the slope control of the DC voltage and AC frequency (V–f slope control), in which the virtual inertia is introduced. This method can ensure that each AC sub-system shares the primary frequency control function. Additionally, with the new control method, it is easy to apply the secondary frequency control method of traditional AC systems to AC/DC hybrid systems to achieve the steady control of the DC voltage and AC frequency of the whole system. Most importantly, the new control method is better than the traditional control method in terms of dynamic performance. In this paper, a new control method is proposed, and the simulation model has been established in Matlab/Simulink to verify the effectiveness of the proposed control method.

Abstract: A high-power reversible converter can achieve a variety of functions, such as recovering regenerative braking energy, expanding traction power capacity, and improving an alternating current (AC) grid power factor. A new hybrid traction power supply scheme, which consists of a high-power reversible converter and two 12-pulse diode rectifiers, is proposed. A droop control method based on load current feed-forward is adopted to realize the load distribution between the reversible converter and the existing 12-pulse diode rectifiers. The direct current (DC) short-circuit characteristics of the reversible converter is studied, then the relationship between the peak fault current and the circuit parameters is obtained from theoretical calculations and validated by computer simulation. The first two sets of 2 MW reversible converters have been successfully applied in Beijing Metro Line 10, the proposed hybrid application scheme and coordinated control strategy are verified, and 11.15% of average energy-savings is reached.

Abstract: Joule heating is a significant phenomenon in dielectrophoresis-based microfluidic devices due to the local amplification of the electric field around electrodes. This leads to the temperature rising in microchannel which would influence the bioactivity of samples in the microchannel. In this paper, a numerical simulation model considering joule heating effect, electric field, and flow field is proposed to describe dynamic behaviors of two-phase flows of the dielectrophoresis microchip. The experimental methods are applied to verify the rationality of model and joule heating effects on microchips under both AC (Alternating current) and DC (Direct current) electric fields are investigated in detail. In numerical simulation part, the difference between AC and DC electric fields is compared. According to the results, it is found that with the same effective voltage, DC electric field can generate more joule heat and flow in the microchannel obtained higher temperature. This is caused by that the electric field strength around the electrodes in the DC electric field is stronger than that of the AC electric field. Secondly, effects of dispersed phase and continuous phase flow velocity are investigated and temperature will decrease with the increasing of flow velocity. Also, it is found that the Joule heating effects improve the droplet velocity based on the results. Finally, an infrared camera is applied to monitor the thermal characteristics of the microchannel to ensure that the numerical simulation is reasonable. These results are expected to provide useful guidance for future designs of dielectrophoresis-based microdevices that will avoid joule heating effects or take advantage of joule heating effects.

Abstract: A motor driving device is disclosed. The motor driving device includes: a rectifier rectifying alternating current (AC) power into direct current (DC) power to output an input voltage; a first buck-boost converter including a plurality of switches for converting the input voltage and having a buck mode of stepping down the input voltage and a boost mode of stepping up the input voltage; an inverter converting a DC-link voltage transformed from the first buck-boost converter into an AC voltage and transferring the AC voltage to a motor; and a controller receiving motor information related to driving of the motor, comparing magnitudes of a desired DC-link voltage depending on the received motor information and the input voltage with each other, and performing a control to switch only any one of the plurality of switches so that the first buck-boost converter is operated in the buck mode or the boost mode.