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This brief proposes a highly-integrated 3-phase ( $3\boldsymbol{\Phi }$ ) 4:1 resonant switched-capacitor (ReSC) converter with parasitic capacitor soft charging for Internet-of-Things devices, reducing the current stress at the point of load. Both the $3\boldsymbol{\Phi }$ resonant operation and the parasitic loss reduction schemes improve the power conversion efficiency. Also, this $3\boldsymbol{\Phi }$ -ReSC converter implements a flying capacitor pre-charge scheme to guarantee a safe startup. The chip, fabricated in a 65-nm CMOS process, occupies a silicon area of 1.39 mm2. We achieve a peak efficiency of 85.5% and a maximum output current of 130mA, in a mm-sized solution, with an input range of 2.3 V – 2.5 V.

for automobile applications, a high-switching 48-to-5V DC-DC buck converter is implemented with 0.5µm CMOS process and 0.5µm Gallium-Nitride (GaN)-on-Si process, including the pre-charge tracking technique, temperature-dependent controlled gate driver, and adaptive relaxation gate-drive control technique, which can increase the efficiency by about 8.8% and ensure the current capacity of Enhance-GaN (E-GaN). The inner local negative feedback loop can enhance the reliability and reduce the RON by 12mΩ. The peak efficiency is as high as 95.4%.

This article describes the memory cell proposed design of a low-power 8T SRAM cell. Two PMOS transistors are employed in this proposed approach, one of which is connected to the node voltage Q and the other one is connected to the Qbar. In order to remove the swing voltage at the bit and bit bar lines. When the cell is in working mode, the swing voltage is minimized, which reduces the dynamic power dissipation. Precharge voltage level is a technique in which a PMOS transistor acts as a switch and an NMOS transistor acts as a resister, resulting in a series of leakage current reductions when the transistors move from sleep to active and vice versa. The findings of the comparison show that the read, write, and hold mode operation for the proposed 8T SRAM cell is superior to that of the 6T SRAM cell. This is frequently because greater static noise margins are obtained, ensuring good bit cell write ability. All simulation results of read and write on the proposed 8T SRAM cell and current models of 6T SRAM cell have been applied to 130 nm CMOS technology utilizing the Symica DE tool.

A pulse-width-modulation (PWM) bidirectional ac-dc converter (i.e., active rectifier) with dc-faultblocking and self-pre-charge capabilities is proposed in this paper for low-voltage dc (LVDC) applications. The proposed converter, which is named as ”H5 + converter”, consists of an H4 bridge, a bidirectional switch, and a transient-voltage-surge (TVS) diode. The bidirectional switch and the TVS diode enable the dc-fault blocking and dc-bus self-pre-charge, while preserving the low common mode voltage noise and low leakage current of the converter. Additionally, the proposed H5+ converter has advanced features under a dc-side short circuit fault, such as fault diagnosis and fault recovery. Operation principles of the proposed converter are presented and analyzed. A down scaled prototype is built. Experiment results are shown and analyzed, including steady-state waveforms, common-mode performance, start-up dynamics, as well as dc fault blocking, fault diagnosis, and fault recovery. Moreover, the proposed converter is compared with other two dc-fault blocking converters for LVDC applications, in terms of converter capabilities, required devices, and power switch losses.

A non-volatile memory designed to FLASH recollections and switch SRAM seems to be the Magnetic RAM (MRAM) proximity unit. Due to its inherent radiation hardness, Spin Transfer Torque Magnetic Memory (STT-MRAM) was also used for top-responsibility applications. CMOS circuit sensitive to radiation Pre Charge Sense electronic equipment (PCSA); but we are able to recharge the non-volatile storage ceaselessly to urge accurate details. Since the current advantages are abandoned by radiation effects, STT-MRAM cannot be used specifically for top radiation applications. In this paper, a new style in the change of PCSA STT-MRAM sensing circuit is proposed and the paper focused more on power and space with performance up gradation.

Due to limited scalability and leakage power of CMOS-based logic circuit, Spin Transfer Torque (STT) device, which has the characteristics of a low area, zero leakage power, nonvolatile and infinite endurance, is one of the strongest candidates to overcome limitations of CMOS. Based on these characteristics, efforts have been made to develop STT-device logic circuit. However, STT-device logic circuit has encountered the problem of read reliability. To address read reliability issue, we propose a new Sense amplifier, named variation-tolerant separated precharge sense amplifier. This circuit, by using transmission gate and feedback, is resilient to process variation and has high read reliability. Simulation using the 65nm process is conducted to show the performance of the proposed sensing circuit. Simulation results demonstrate that the reading error rate of the proposed sense amplifier decreased by 68% and 37% respectively, compared to the conventional SPCSA and RESPCSA.

This paper proposes the pre-charge, discharge, and mini-UPS circuits of an auxiliary power network architecture for 10kV SiC-based power electronics building block. The design and working principle of all components are given with hardware prototypes and test waveforms. This architecture proposes a simple auxiliary-power-only pre-charge method, and increase the system reliability by having a rapid discharge circuit for dc-link, and a mini-UPS backup power supply.

This paper presents a cost-effective electromagnetic energy harvester (EMEH) based on wire-wound technology. It also shows the energy management system used to convert the EMEH's AC voltage to a DC one. The EH system is self-powered and does not require external sources or pre charge of any of its components and provides maximum power point tracking.

The deployment of electric vehicles (EVs) protects the environment by reducing carbon emissions. Since plugged-in EVs require energy from the power grid to charge their batteries, the charger component is inevitable. With the appropriate control, additional functions can be achieved with the existing charger’s converter topology. This paper discussed the implementation of a new control strategy in a three-phase off-board EV charger, which provided grid voltage regulation while charging the vehicle. The vehicle charging control (P-control) and grid voltage regulation control (V-control) were implemented in the back-end DC/DC converter and front-end AC/DC converter of the charger, respectively. The proposed P-control utilized the constant current/reduced constant current charging approach to rapidly charge the battery while alleviating battery deterioration. Meanwhile, the proposed V-control had the capability to regulate the grid voltage and DC-link voltage during the EV charging process. Besides the PSCAD/EMTDC simulation, experimental testing was performed on a 2 kVA laboratory EV charger to validate the control performance. While complying with the harmonic standards, the experimental results showed that the charger prototype effectively regulated the grid voltage to the pre-charge voltage while maintaining the DC-link voltage at 150 V during various charging currents of up to 5 A.

To deeply understand interrupting phenomena in high-voltage circuit breakers, it is important to measure the electrical characteristics of switching arcs in high-speed gas flow at current zero. A ring-shaped capacitive probe is proposed to measure a spatial arc voltage distribution. The configuration of the probe is decided by considering the effects of arc position and arc radius. The difference between arc voltage distributions is distinguished for an interrupting current of 12 and 30 kA on interrupting tests using the circuit breaker model.

– This paper presents a zero voltage switching DC/DC converter for DC micro-grid system applications. The proposed circuit includes three half-bridge circuit cells connected in primary-series and secondary-parallel in order to lessen the voltage rating of power switches and current rating of rectifier diodes. Thus, low voltage stress of power MOSFETs can be adopted for high voltage input applications with high switching frequency operation. In order to achieve low switching losses and high circuit efficiency, asymmetric pulse-width modulation is used to turn on power switches at zero voltage. Flying capacitors are used between each circuit cell to automatically balance input split voltages. Therefore, the voltage stress of each power switch is limited at Vin/3. Finally, a prototype is constructed and experiments are provided to demonstrate the circuit performance.

This letter presents a voltage-controlled capacitor that varies from 20% to 100% of the rated capacitance (1 μ F) with a control voltage from half of the voltage rating to 0 V. Capacitance, self-resonant frequency, and equivalent series resistance were measured with respect to the control voltage. An equivalent circuit and a nonlinear model derived from relationship between permittivity and electric field were created and implemented in SPICE. A buck converter with input of 12 V, output of 5 V, and switching frequency of 500 kHz was built to demonstrate the change from 85% to 40% of the rated capacitance of the voltage-controlled capacitor. The error between the simulation and experiment was limited within 10%, which verifies the model.

This paper discussed the design and development of a 2 kVA three-phase off-board electric vehicle charger prototype with a practical voltage control, where the procedures of the experimental construction were comprehensively presented. For the experimental setup, the effectiveness of the interface circuits and auxiliary power supply units were individually validated. Moreover, the electric vehicle charger utilized a Digital Signal Processor to employ the control strategies of vehicle charging and power grid voltage regulation. The proposed control can simultaneously charge the battery of electric vehicle, maintain a constant DC-link voltage and also provide the appropriate reactive power compensation to regulate the grid voltage to the desired level. While complying with the power quality standards, the experimental results had validated the practicality of the integrated electric vehicle charger and the control performance. The charger prototype had effectively regulated the grid voltage to the pre-charge voltage of 0.96 per unit while maintaining the DC-link voltage at 150 V during various charging currents of up to 5 A.

As a key element of a power system, a circuit breaker (CB) requires regular maintenance. Intelligent online condition assessment is increasingly becoming a requirement for key items of power plants, including CBs. The interruption chamber, as the most critical part of the CBs, plays an important role in the proper operation of CBs. Online assessment of this part is difficult from a technical perspective due to the high noise level and presence of a transient recovery voltage. This paper proposes a set up for the online measurement of the CB arc voltage during trip/close operations. In addition, a method has been proposed to evaluate the remaining useful lifetime of the interruption chamber based on the measured arc voltage and current. The setup and the proposed approach are verified experimentally.

Wireless power transmission (WPT) based on near-field inductive coupling principle is a promising solution to the power supply issue of a freely moving capsule robot (CR) that employs dc motors as actuators. However, the limited inductive power can cause a voltage drop when dc motors start or stall, because short-time peak power is required. To handle the voltage drop issue, we propose the use of a novel power management circuit (PMC) that consists of four successively connected segments of a full-bridge rectifier for ac–dc conversion, a buck dc–dc converter for highly efficient voltage reduction, a power buffer for power storage and short-time power supply, and a low drop-out (LDO) regulator for voltage stabilization. The power buffer is implemented with a super-capacitor array (SCA) that employs the output voltage of the dc–dc converter as its charging voltage. To analyze and optimize the PMC containing the SCA (PMC-SCA), a model is built based on deducing the input resistance relations between each pair of adjacent segments, and its correctness is then validated experimentally. A comparison between the PMC-SCA and the traditional PMC (a rectifier + a regulator) is also conducted, and the former shows superiorities in both reducing voltage drop and improving safety related to temperature rise of onboard receiving coil (RC). Finally, a primary PMC-SCA prototype measuring $\Phi $ 13 mm $ \times $ 4 mm is integrated to an inchworm-like CR for effectiveness validation; the CR working voltage is measured to be higher than 3 V at all times, which ensures the proper functioning of the CR.

DC power relay is a key electromechanical component widely used in electrical vehicles, photovoltaics, as well as more-electric aircrafts for energy managing, power conversion, and distribution. As the voltage and current increase due to relay switches, arc discharge becomes an unavoidable and significant issue during the operation of the dc high-power relay. Bridge-type contact and external permanent magnets are spontaneously employed in its arc chamber to accelerate the quenching of arc. In this paper, the complicated arc discharge plasma in a dc power relay has been investigated by using both experimental and numerical approaches. Initially, arc dwell and arc restriking characteristics during the arc motion phase are presented by analyzing the voltage and current waveforms and arc images acquired in carefully designed breaking experiments. The arc driven by a transverse magnetic field with a variety of flux densities and the influence of flux densities on arc voltage and dwell are preliminarily discussed based on the experimental results. Then, to reveal the arc physics and to determine the influence of transverse magnetic field on arc motion characteristics, a simplified model based on the magnetohydrodynamic (MHD) theory is built and three cases with different magnetic field are calculated. The simulated arc behaviors including distributions of the temperature and current density are presented. The mechanism underlying the influence of transverse magnetic field on the arc motion is analyzed according to arc root transfer and arc voltage variation. In addition, to understand the formation of the arc restriking, the critical breakdown electric-field strength inside the arc gap is also calculated based on streamer breakdown theory. The parameters in the space occupied by earlier arcs, as predicted by the MHD simulations, are used in the breakdown calculation. Results show that the critical breakdown voltage reduces remarkably along with growth of the operating voltage and breaking current, and the arc dwell time can be reduced by strengthening the external magnetic field within a reasonable extent.

This paper presents a work that was aimed to develop methods along with test facilities for characterizing the arc/contact movement in low-voltage miniature circuit breaker which has a related current under 125 A, and to find its relation with the short-circuit current/voltage in the circuit. The method consists of: 1) the high-speed camera for obtaining the image of the arc or contact movement; 2) the data acquisition system that measures the current during the short-circuit break; and 3) the circuitry system that establishes the synchronization of the arc movement capturing and the current acquisition. In particular, two methods were developed for this purpose: one based on analog signal and the other based on digital signal. The experiment shows that the accuracy of the synchronization, dependent on the sampling rate of the high-speed camera, is about from tens of microseconds to hundreds of microseconds with both methods. The two methods have their own advantages and disadvantages, and they can be tailored to applications for the best performance.

Traditionally, series electric vehicles, such as bus, construction machine like bulldozer, carry a certain capacity of power batteries, capacitors or other energy storage units. However, these energy storage units not only occupy a few large of vehicle space leading to be uncomfortable for passengers and driver, but also increase production cost, and reduce the powerline's reliability. In order to make the powerline system more compact and reliable, a new series electric system without energy storage unit is proposed in this paper. This new powerline's mathematic models are established. And a fuzzy PI closed-loop control strategy with parametric self-tuning function control is put forward to stabilize the powerline DC-link's voltage fluctuation. The models and control strategies are simulated in Matlab/Simulink software environment. The results give a verification on the new powerline's configuration, as well as the proposed control strategy.

This study examines the use of superconducting magnetic and battery hybrid energy storage to compensate grid voltage fluctuations. The superconducting magnetic energy storage system (SMES) has been emulated by a high-current inductor to investigate a system employing both SMES and battery energy storage experimentally. The design of the laboratory prototype is described in detail, which consists of a series-connected three phase voltage source inverter used to regulate ac voltage, and two bidirectional dc/dc converters used to control energy storage system charge and discharge. "DC bus level signaling" and "voltage droop control" have been used to automatically control power from the magnetic energy storage system during short-duration, high-power voltage sags, while the battery is used to provide power during longer term, low-power undervoltages. Energy storage system hybridization is shown to be advantageous by reducing battery peak power demand compared with a battery-only system, and by improving long-term voltage support capability compared with an SMES-only system. Consequently, the SMES/battery hybrid dynamic voltage restorer can support both short-term high-power voltage sags and long-term undervoltages with significantly reduced superconducting material cost compared with an SMES-based system.

A novel voltage-doubling circuit with parallel-resonant dc–dc converter is proposed. The converter consists of full-bridge inverter, resonant tank, high-frequency high-voltage transformer, and voltage-doubling circuit. In the high-voltage applications, low-output voltage ripple has been given much attention. The output voltage step-up ratio is increased by two parts. One is a high-frequency high-voltage transformer and the other is a voltage-doubling circuit. The novel voltage-doubling circuit can not only reach a higher output voltage but also reduce output ripple to a lower level than the conventional one. Therefore, while maintaining the same output voltage, the transformer's turn ratio can be reduced compared with the conventional voltage-doubling circuit. The output power can be adjusted by the phase-shift control technique. In addition, combining this technique with the parallel resonant tank can make all the switches achieve zero voltage turn on (ZVS). The operating principles, steady-state analysis, and the parameter designs are discussed in this paper. Finally, a prototype circuit with 400-V input voltage, 40-kV output voltage, and 300-W output power is developed in the laboratory to verify the performance of the proposed converter.

Various circuit breaker models have been developed as a tool to evaluate the breaker interrupting capability and to investigate interaction between the breaker and the external circuit. This paper presents selected models of high voltage SF6 circuit breakers (Cassie–Mayr, Schwarz–Avdonin, and an ideal switch with a predefined chopping current level), followed by analysis of the models impact on the 400 kV overhead line fault clearing process. Several study cases have been performed to demonstrate the impact of the circuit breaker model on the arcing time and on the transient recovery voltage (TRV) during breaking of the near-to-generator faults. The results obtained indicate that the arc voltage introduced by the circuit breaker model can force the fault current zero crossing and in consequence can significantly change the breaking conditions. It particular, in the study cases where the arc voltage has significant impact on the breaking conditions (such as the near-to-generator fault), the models applied accurately represent arc voltage during the entire current interruption process.

This paper presents a CMOS fully-integrated temperature sensor based on a relaxation oscillator for IoT applications. To reduce power consumption, this sensor utilizes the half-period pre-charge compensation relaxation oscillator and uses a time-to-digital convertor (TDC) instead of analog-to-digital convertor (ADC) to count. Besides, the current distribution circuit is employed to improve temperature accuracy. The proposed sensor is implemented in 0.18 µm CMOS and occupies an area of 0.11 mm2. Measurement results show that the temperature sensor achieves an inaccuracy of −0.3/+0.27 °C across −15°C to 65°C after 2-point calibration. The chip consumes 1.3 µW at 27°C with a 650 mV voltage supply.

Due to the charge leakage during the touch sensing period and the threshold voltage shift of the driving thin-film transistors (TFTs), the conventional gate driver circuits suffer from poor stability for in-cell touch displays with an increased touch reporting rate. This paper shows a new gate driver circuit, consisting of a two-stage pre-charge structure, which can reduce the charge leakage during the touch sensing period and suppress the threshold voltage shift of the driving TFTs. Simulation results demonstrate that, the rising and falling time differences between adjacent stages are 9.3% and 1.6% for the conventional and the proposed gate driver circuit, respectively. In the case that the threshold voltage of key TFT shifts by +10 V, the rising and falling time degradation ratios are 120% and 2.4% for the conventional and the proposed gate driver circuit, respectively. Therefore, the proposed gate driver circuit is stable for in-cell touch panels with a high touch reporting rate.

In order to improve the ability to quench the power frequency arc following broken down by lightning overvoltage, this paper introduces a multigap structure and analyses the process and mechanism of arc quenching in the arc chamber. A simulation model has been established based on the magnetohydrodynamics theory to analyze the characteristics of the plasma in an arc chamber. A series of comprehensive tests have also been carried out to test the 10-kV arc quenching structure by using a test platform, which can generate power frequency voltage and lightning impulse voltage. Results show that the multigap arc quenching structure can quench an arc quickly after flashover, and the quenching time occurs at zero crossing of the power frequency follow current. After extinction, arc does not occur any more when the power frequency voltage is recovered. The arc voltage drop in the proposed structure guarantees that the power system does not suffer from trip accident which may be caused by short-circuit overcurrent protection.

As industry pursues safer workplaces with arc flash mitigation programs, they face major challenges in effectively reducing incident energies on the secondary of medium voltage to low voltage (MV-LV) transformers. When an arc fault occurs on the transformer secondary, primary currents can be below the short circuit range of the primary protection. Typical E-rated fuses can take over 2 seconds to clear while high side device 51 relays will have a waiting period before initiating a breaker trip. Solutions that adjust the LV main breaker’s (if applied) protective functions for faster response, do not address arc fault issues on the bus connecting this main breaker to the transformer secondary. This paper presents a method of applying a high speed grounding switch (HSGS) at a location between the MV Erated fuse load terminal and the transformer's primary connection. Since the transformer's primary voltage is reduced to zero in milliseconds, the low voltage arc flash event collapses quickly to limit incident energies to less than 1.2 cal/cm2. Applications can include MV-LV transformers up to 5000kVA.

This paper presents a new gate driver circuit for active-matrix liquid crystal displays with an in-cell touch structure designed by hydrogenated amorphous silicon thin-film transistors. To increase the reporting rate of a touch panel, the proposed circuit can be used to pause display operations to perform touch sensing operations several times per frame. The proposed circuit exploits a pre-charge structure that alleviates the leakage current and long-term stress of a driving TFT during the touch sensing operation. Simulation results confirm that the proposed gate driver circuit can generate a highly uniform output waveform after each touch sensing operation that lasts for 200 μs when the circuit is operate at 85 °C. The variations of the rising and falling time are suppressed below 3.71%, confirming the feasibility of use of the proposed gate driver circuit for an in-cell touch panel.

Hybrid electric and universally electric aircraft seem to be one possible option to fulfil ambitious future emission and noise reduction targets forced by the European Commission with the Strategic Research and Innovation Agenda and the NASA with the NASA N+3 goals. The overall vehicular efficiency of such concepts can be considerably improved. A key element is the design of the electric power train system with regard to efficiency and also mass. Based on a battery-powered direct current (DC) system architecture, the efficiency impact of different design voltages has been investigated in this paper. The main components within a DC electric architecture are power electronics such as converters and inverters, transmission cables, protection devices and cooling systems. Especially, the power electronics show the highest sensitivity when choosing a design system voltage. Two main losses occur within those components, conduction losses and switching losses. While conduction losses decrease with an increase in the design voltage, switching losses normally increase. Therefore, for a required design power there will be a trade-off between conduction and switching losses. For that purpose, two different architecture design philosophies were investigated to compare the system efficiencies at different design voltages. The first architecture is the constant system voltage (CSV) architecture, which compensates a decreasing output voltage of a battery, and a variable system voltage (VSV) architecture, which does not compensate this voltage drop. It has been identified that for an electric power train system delivering a constant power of 6000 kW, the VSV shows the best efficiency. The optimum system voltage of the VSV architecture is near the operating voltage of the electric motor, while the optimum system voltage of the CSV architecture was identified at higher voltages. These results will serve as baseline for the identification of the best voltage level for a mass- and efficiency-optimized system.

A novel integrated implementation of a high step-down multiphase buck for low voltage power supply is presented. The design and test chip measurements of a 10.8,16V to 0.65,2V, 2A, 10MHz, 25.6mW/mm2, four-phases single-chip solution are presented with considerations on architecture, passive components, problems related to high frequency integration and relative improvements on power density. The experimental results confirm the theoretical predictions by simulations and are compared with respect to previous discrete implementations and integrated topologies focusing on high step-down conversion and output power. So-called "high step-down multiphase buck" topologies present advantages in terms of extended duty cycle, reduced passive components' size and reduced switches' breakdown voltages. However, these topologies require a more complex gate drive structure for their high side switches which are working each on a different voltage domain. A novel drive architecture that eliminates the need of any external auxiliary voltage source, being directly supplied on fractions of the input voltage, is proposed. This architecture provides also a recycling of the gate charge at the turn-off of the switches. Another problem addressed is the start up of the converter, which requires a proper pre-charging of the topology's flying capacitors. Power stage measured waveforms show the correct start-up and steady-state operation of the proposed converter design.

SUMMARY This paper proposes a highly efficient drive method for an open-winding induction machine with a single constant voltage source and a single capacitor. By focusing on the phase voltage of the open-winding machine, which is determined by the phase difference and the dc voltage of each power converter, it is possible to control the peak value of the phase voltage by controlling the voltage of the capacitor. Thus, a reduction in the iron loss due to harmonic voltage in the open-winding machine is expected. In the proposed method, the voltage of the capacitor is controlled by the difference between the two reference voltages of the power converter, which depends on the machine power factor and the phase difference of the power converter connected to both ends of the winding. Based on experimental results, the converter loss and the machine loss can be reduced by controlling the voltage of the capacitor in accordance with the machine speed using the proposed method.

Submodule (SM) capacitor is a key component in a modular multilevel converter (MMC), the selection of which must consider the component’s specifications and the requirements of the targeted converter application. This paper focuses on the capacitor selection for MMCs in applications including high-voltage direct current (HVDC) transmission and static VAr compensation using metalized polypropylene film (MPPF) capacitors. The dominant ageing mechanisms of the MPPF capacitors are reviewed to define their operational limits. A straightforward computational procedure and a set of curves are presented to assist the capacitor selection, taking into account criteria in the aspects of maximum capacitor voltage, capacitor voltage ripple, SM voltage capability, and capacitor ripple current stress. Simulation shows the validity of the method and demonstrates its use in design examples.

An application of H-bridges that enable soft start and power factor correction of cage induction machines is presented. The proposed power electronics employs floating capacitor H-bridges connected in series with utility grid and a cage induction motor to provide series voltage compensation. Injecting a series voltage in each phase, the proposed system can be used to control the motor voltage during starting and hence limit the motor starting current. In addition, an algorithm is proposed to accurately predict the worst case scenario for bridge dc capacitor voltage before motor starting. Thus, a dc capacitor overvoltage problem can be avoided. Experimental results show that the proposed system can successfully soft start a standard squirrel cage induction machine under different modes and load conditions. A simple representation of the worst case scenario for dc capacitor voltage before motor starting is established.

This study proposes a single-phase multi-level AC–DC power conversion interface that is composed of a power factor correction stage and a buck power conversion stage. The power factor correction stage is configured using two power factor correctors (PFCs) connected in cascade. Only the power electronic switch in one of the PFCs is switched in high-frequency pulse-width modulation to generate a five-level voltage at the input AC terminals of the power factor correction stage. The input current of the power factor correction stage is controlled to be sinusoidal and in phase with the utility voltage. Accordingly, the voltage stress and switching loss are improved because the change in voltage in each switching operation is reduced. The filter inductance and the electromagnetic interference are also reduced. The buck power conversion stage integrates a buck power converter and a forward power converter that combines the output voltages of the two PFCs in a stable DC voltage that supplies the load. The controllers for the buck power converter and the forward power converter are integrated to simplify the controller for the buck power conversion stage. A hardware prototype is developed to verify the performance of the proposed single-phase AC–DC power conversion interface.

A method of arc voltage gradient calculation for an electric arc furnace (EAF) is presented. The arc voltage gradient is the basic characteristic in study and simulation of an automatic power control system of an EAF. This characteristic is a strongly nonlinear multifactorial function that depends on electrical parameters of a power supply system, thermal conditions, and processes of arc heat exchange in an EAF melting bath. The method of arc voltage gradient calculation considers the relation between the electric and thermal conditions of an EAF in order to describe feasible nonlinear properties and to improve expressions for voltage and current transfer ratios as nonlinear multifactorial functions in particular. An EAF is regarded as a subject of control. Multifactorial properties are defined by the parameters of an equivalent electrical circuit of a furnace and by variable conditions of arc heat exchange in a melting chamber during steel melting. The method is effective for overcoming the uncertainty of the arc length in simulation of an EAR power controller. The unstable behavior of the furnace at a high impedance was explained using the obtained functions of the arc current and the arc voltage for various electrodes and the arc length. The minimum allowed arc current was found. The automatic power controller becomes unstable and the arc is extinguished under this value.

This paper analyzes the effect of unbalanced voltage on voltage rise for a grid-connected photovoltaic (PV) system, and proposes a voltage rise mitigation strategy which injects negative-sequence currents to compensate the unbalanced voltage aiming especially to reduce the voltage rise. The paper also discusses how the averaged powers related to the injected negative-sequence currents are measured by the power meter. Simulation result confirms the superior performance of the proposed strategy over the classical method which suppresses the voltage rise by adjusting the power factor.

In all the grid connected converters, irrespective of the front end topology (whether it is a diode rectifier, a bridgeless active power factor correction rectifier, or an active front end rectifier (AFE)), there is always a DC bus electrolytic capacitor with high value after the front end, for energy storage and line frequency ripple mitigation requirements. During start-up, there is a pre-charge circuit associated with this capacitor to limit inrush current. The existing pre-charge circuits usually include charge resistor and mechanical contactor, are often related to a high component volume and also high surge current at beginning. To address that, this paper proposes a novel precharge circuit including only solid state device. This circuit utilize a “virtual” miller capacitor along with a MOSFET to control the inrush/charge current flowing through the bus capacitor, although the input is AC, the discontinuous charge current is controlled within a constant value profile. The major benefits of proposed method include much reduced volume, lowest peak current stress, and extended life time/reliability.

This paper presents two capacitive-pulling techniques to aid the settling of the switched-capacitor residue amplifier in a pipeline analog to digital converter. The main idea is to pre-charge the load capacitors to proper voltages, connect them to the output of the operational trans-conductance amplifiers (OTAs) during the evaluation phase, and hence pull the passive charge sharing so that the initial voltage step of the OTA input is instantly minimized. The OTA hence skips the slew region, and enters into the linear settling region, leaving just a minor charge to be moved by the OTA. This allows you to get the same settling precision with saving 30% power consumption of the OTA using minimal three-level pre-charged method. Alternatively, the conversion rate can be increased by over 30% using the continuously controlled pre-charged method.

A new grounded voltage controlled positive resistor (GVCPR) is proposed in this brief. The proposed GVCPR with a single control voltage is composed of only six MOS transistors operated in saturation region. It has the feature of fine tunability from about 770 ${\Omega }$ to about 1370 ${\Omega }$ . It can be operated properly up to a few hundreds of MHz. It has low power consumption and a wide dynamic range. It does not need any bias currents and voltages. However, its control voltage does not have the property of high input impedance and it requires some active element matching conditions. A novel second-order voltage-mode multifunction filter is given as an application example. A lot of simulation results and some experimental tests are achieved in order to verify the theory.

Aimed to provide a more close-to-reality and rapid calculation method for optimization design of low voltage circuit breaker with complex mechanism, an interruption model is constructed, which can describe the coupling of air blast process with arc model, complex mechanical movement, magnetic field, and electric circuit. The model is based on the non-stationary gas conservation equations, and considers the influence of the chamber structure on the gas dynamics. To realize the interaction between the arc movement and the gas flow simply, on the one hand, the moving electric arc is deemed an energy input source of the chamber gas. On the other hand, the movement equation of the arc considering action of the gas flow is built. With this model, the general principle of the chamber gas flow, arc voltage and current during the interruption process of an actual breaker are calculated and compared with the experiment results. As an application, the influence of the chamber vent size on the arc movement is studied with the model as well.

The power supply system in KSTAR neutral beam injector consists of low voltage and high current DC power supplies for plasma generator of ion source and high voltage and high current DC power supply for accelerator grid system. The arc discharge is initiated by an arc power supply supplying the arc voltage between the chamber wall and 12 filaments which are heated by individual filament power supply. The negative output of arc power supply is common to each positive output of 12 filament power supplies. To interrupt the arc discharging for the fault condition of the arc current unbalance, DCCT current monitor is placed at the positive output cable of the filament power supply. The plasma grid (G1) power supply has the maximum capability of 120 kV/70 A which consists of low voltage regulator with IGBT-switched chopper array system for the voltage control in unit of 600 V and the high voltage rectified transformers to supply DC voltage of 20 kV, 30 kV, and 50 kV. The output voltage of the G1 power supply is also connected to the input of the voltage divider system which supplies the gradient voltage to the gradient grid (G2) in the range of 80–90% of G1 voltage by changing tap of winding resistors in unit of 1%. The charged G1 voltage is turned on and off by the high voltage switch (HVS) system consisting of MOSFET fast semiconductor switches which can immediately be opened less than 1 μs when the ion source grid breakdown occurs. The decelerating grid (G3) power supply is inverter system using capacitor-charge power supply to supply maximum −5 kV/5 A. The important component in power supply system is the surge absorber near the ion source to limit the arc energy deposited to accelerator grid. This paper presents configuration and features of power supply system, main controller, and interlock system of KSTAR NBI.

The static and dynamic voltage distribution characteristics and voltage sharing design of a 126-kV modular triple-break vacuum circuit breaker (VCB) was discussed in this paper. The finite-element method and power frequency tests were used to calculate and verify the static voltage distribution ratios and distributed capacitance parameters of multi-break VCBs, respectively. A model combining the post arc current model and equivalent capacitance model was proposed for simulations of dynamic transient recovery voltage (TRV) distribution characteristics of the triple-break VCB. The simulation results indicated that besides the stray capacitances, the TRV sharing design should take the influence of residual charge (RC) into account, and the influence of RC on the TRV distribution is relevant to the differences of RC parameters among the series interrupters. Therefore, the appropriate value of grading capacitors should meet the requirement of the worst case. Based on the investigation of this paper, a 126 kV U-shaped triple-break VCB prototype with 1000 pF grading capacitors has been produced, and the successful large current breaking tests indicate the good breaking capacity and suitable voltage sharing design of the triple-break VCB.

A current-limiting circuit breaker (CLCB) can quickly interrupt circuit faults and limit the short-circuit current. Modeling of a CLCB is important for the calculation of short-circuit current and arc flash energy. Based on the analysis of the arc voltage waveforms of CLCBs, a new arc model is derived. The Schwarz arc model and arc length are used to represent the complicated voltages of CLCBs, and arc length is determined from a differential equation. The test results of a commercial CLCB sequentially deployed in a couple of three-phase power systems are studied, and the parameters of the model are obtained. The three-phase faults in the power systems are simulated. The short-circuit currents and voltages of the CLCB are calculated and compared to the test results. The simulation results are in good agreement with the test data, and the proposed model can predict the high-current arcs in CLCBs. These techniques facilitate the calculation of short-circuit currents.

Bulky electrolytic capacitors, which are often needed in dc systems to filter out voltage ripples, considerably reduce power density and system reliability. In this paper, a ripple eliminator, which is a bidirectional buck–boost converter terminated with an auxiliary capacitor, is adopted to replace bulky capacitors in dc systems. The voltage ripples on the terminals (i.e., the dc bus) can be transferred to the auxiliary capacitor, and the ripples on the auxiliary capacitor can vary in a wide range. Moreover, the average voltage of the auxiliary capacitor can be controlled either lower or higher than the dc-bus voltage, which offers a wide operational range for the ripple eliminator and also the possibility of further reducing the auxiliary capacitance. Hence, the total capacitance required can be much smaller than the originally needed. After proposing a control strategy to transfer the voltage ripples to the auxiliary capacitor, three control strategies are proposed to regulate the auxiliary-capacitor voltage to maintain proper operation. Intensive experimental results are presented to demonstrate the performance.

Studies of circuit breakers are of interest to high voltage direct current (HVDC) power system. The method for investigation of the switching arc characteristics of a 500 kV metallic return transfer breaker (MRTB) is presented in this paper, by coupling magneto-hydro-dynamics (MHD) arc model with the resonant circuit equations. 2-D MHD arc model taking account of important physical processes of mass flow, Ohmic heating, radiation energy transfer, momentum exchange, Lorentz force and current flow is developed, and then the influence of stray resistor is analyzed under the interrupting current of DC 4 kA. Calculation results of the distribution of temperature and gas pressure in the nozzle region are presented, where the shock wave and negative voltage-current characteristic of arc are discussed. The calculated arc current and voltage are in agreement with the experimental results to some extent, which could verify the validity of the calculation method partially.

The neutral beam injection generate ultra-high temperature energy in the tokamak of nuclear fusion. The neutral beam injection make up arc power supply, filament power supply and acceleration & deceleration power supply. The arc power supply has characteristics of low voltage and high current. Arc power supply generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The proposed buck converter used parallel switch because it can be increased capacity and decrease conduction loss. When an arc generated, the neutral beam injection chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus the proposed converter should be designed for the characteristics of low voltage and high current. Also, the arc power supply should be guaranteed for system stability. The proposed parallel buck converter enables the system stability of the divided low output voltage and high current. The proposed converter with constant output be the most important design of the output inductor. In this paper, designed arc power supply verified operation of system and stability through simulation and prototype. After it is applied to the 288(kW) arc power supply for neutral beam injection.

International audience; Ensuring that the DC voltage remains within an acceptable range is a major concern for HVDC systems. In DC systems, the capacitance is the dominant factor that determines the volatility of the DC voltage against sudden disturbances in analogy to inertia of the AC system characterizing the rate of change of the frequency. As a solution to this problem, the authors of this paper previously proposed a novel control method for Modular Multilevel Converter (MMC), named Virtual Capacitor Control. This enables to make the MMC behave as if there were a physical capacitor whose size is adjustable. Thus, it is possible to attenuate the fluctuations of the DC voltage by virtually enhancing the equivalent capacitance of the system. This paper presents a method to determine the required size of this virtual capacitor to limit the peak of the DC voltage to a desired value in the case of the HVDC grid collecting the power generated by wind farms where a master/slave control may be applied. Its advantages are explicated with analysis on the DC voltage dynamics, and its feasibility is verified by EMT simulations of a three-terminal DC grid.