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In order to accelerate the fault current transfer rate of hybrid DC circuit breaker (HDCCB) and reduce the cost. A novel full thyristors HDCCB combining vacuum and gas integrated series switch is proposed in this paper, which accelerates the fault current transferred. Moreover, the breaking of higher current levels and lower cost by using the full thyristors to replace the IGBT and other power electronic (PE) devices are realized. The operation of proposed HDCCB is analyzed in detail, and the theoretical numerical model is derived. With the key parameters optimized in terms of the operation HDCCB, the breaking current capability and the effectiveness are verified by the simulation model. Based on this, preliminary tests from a developed low-power prototype are presented and verified the performance of the proposed novel HDCCB.

The significant role of nonlinear wave–particle interactions in the macrodynamics and microdynamics of the Earth's outer radiation belt has long been recognised. Electron dropouts during magnetic storms, microbursts in atmospheric electron precipitation, and pulsating auroras are all associated with the rapid scattering of energetic electrons by the whistler-mode chorus, a structured electromagnetic emission known to reach amplitudes of about 1 % of the ambient magnetic field. Despite the decades of experimental and theoretical investigations of chorus and the recent progress achieved through numerical simulations, there is no definitive theory of the chorus formation mechanism, not even in the simple case of parallel (one-dimensional) propagation. Here we follow the evolution of these theories from their beginnings in the 1960s to the current state, including newly emerging self-consistent excitation models. A critical review of the unique features of each approach is provided, taking into account the most recent spacecraft observations of the fine structure of chorus. Conflicting interpretations of the role of resonant electron current and magnetic field inhomogeneity are discussed. We also discuss the interplay between nonlinear growth and microscale propagation effects and identify future theoretical and observational challenges stemming from the two-dimensional aspects of chorus propagation. [ABSTRACT FROM AUTHOR]

The frequency chirping of chorus waves is commonly observed in the Earth's inner magnetosphere, but its generation remains an open question. Recently, Liu et al. (2021), https://doi.org/10.1029/2021JA029258 reported two unusual rising‐tone (upward chirping) chorus elements. Although the central frequency of constituent subpackets rises, the frequency of a single subpacket is surprisingly downward chirping. With a gcPIC‐δf $\delta f$ simulation in the dipole field, we successfully reproduce this kind of substructure, which contains alternating signs of chirping. Interestingly, both hole and hill structures are formed around the theoretical resonant velocities in the electron phase space, no matter whether the chirping is upward or downward. However, during each chirping interval, only one structure (either a hole or a hill) is associated with wave excitation: the upward chirping is related to the hole, while the hill contributes to the downward chirping. Our study provides a fresh perspective on the theory of frequency chirping in chorus waves. Plain Language Summary: The frequency chirping is a typical feature of chorus waves in the Earth's inner magnetosphere, which generally contain either rising‐tone (upward chirping) elements or falling‐tone (downward chirping) elements. Previous theory has suggested that the chirping is due to the nonlinear wave‐particle interaction, where the hole or hill structure is formed in the electron phase space. Recently, Liu et al. (2021), https://doi.org/10.1029/2021JA029258 have observed the upward chirping elements with their subpackets of downward chirping. What electron structure is associated with these elements becomes a puzzle. With a one‐dimensional (1D) general curvilinear particle‐in‐cell (gcPIC) δf simulation in the dipole magnetic field, we successfully reproduce this kind of chorus element, whose frequency contains alternating upward and downward chirping. Interestingly, both the hole and hill structures are formed during a chirping interval, but only one of the two structures is responsible for wave excitation and frequency chirping. The structure of hole‐hill combination provides an important clue into the theory of the frequency chirping in chorus waves. Key Points: With a gcPIC‐δf $\delta f$ simulation in the dipole field, we reproduce the upward chirping chorus element, whose subpackets are downward chirpingBoth hole and hill structures can be formed in the ζ−v‖ $\zeta -{v}_{\Vert }$ phase space, no matter whether the frequency is upward or downward chirpingThe time evolution of the hole and hill structures in the phase space leads to the alternating frequency chirping [ABSTRACT FROM AUTHOR]

Abstract The frequency chirping of chorus waves is commonly observed in the Earth’s inner magnetosphere, but its generation remains an open question. Recently, Liu et al. (2021), https://doi.org/10.1029/2021JA029258 reported two unusual rising‐tone (upward chirping) chorus elements. Although the central frequency of constituent subpackets rises, the frequency of a single subpacket is surprisingly downward chirping. With a gcPIC‐δf simulation in the dipole field, we successfully reproduce this kind of substructure, which contains alternating signs of chirping. Interestingly, both hole and hill structures are formed around the theoretical resonant velocities in the electron phase space, no matter whether the chirping is upward or downward. However, during each chirping interval, only one structure (either a hole or a hill) is associated with wave excitation: the upward chirping is related to the hole, while the hill contributes to the downward chirping. Our study provides a fresh perspective on the theory of frequency chirping in chorus waves.

Vienna rectifier is widely employed in the electric vehicle charging system and wind turbine system due to its higher efficiency and lower total harmonic distortion. However, the Vienna rectifier with the LCL filter has the challenge of resonant current mitigation, current zero-crossing distortion elimination, neutral point (NP) voltage balance and switching loss reduction. Moreover, these problems are mutually coupled. To overcome these issues, the causes of resonant current with the conventional discontinuous pulsewidth modulation (PWM) (DPWM) method is analyzed, which reveals that the abrupt change of reference voltage has a wide range harmonics band and easily induces the resonant current at resonant frequency. Then, based on the analysis, a novel three-layer DPWM method with three offset voltages injection is proposed. In the first layer, the NP voltage balance is realized by injecting the first offset voltage. In the second layer, the second offset voltage, which makes the discontinuous reference voltages smooth is presented to reduce the losses and suppress the resonant current. In the third layer, the third offset voltage is elaborated to eliminate current zero-crossing distortion caused by different power factor and the LCL filter. Based on the proposed method, resonant current mitigation, current zero-crossing distortion elimination, NP voltage balance are realized simultaneously with reduced switching losses. The effectiveness and performance of the proposed method are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This article proposes a harmonic voltage injection pulsewidth modulation (PWM) method for a Vienna rectifier with an LCL filter. Existing PWM methods for Vienna rectifiers with full power factor can lead to resonance problems. It generates current oscillation at the resonant frequency. It is analyzed that why the resonance problem occurs in Vienna rectifier with the existing PWM methods. To solve these resonance problems, the proposed method injects a sinusoidal harmonic voltage into the sinusoidal reference voltage. The magnitude and phase of the injection voltage are determined by the power factor of the rectifier-side. Compared to other PWM methods, the proposed PWM method eliminates the possibility of resonant problems. Considering the operation characteristics of the proposed PWM method, this article suggests a design process for an LCL filter. The effectiveness and performance of the proposed PWM method and the design process for an LCL filter are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

High efficiency, high power density and wide output voltage are required for on‐board charger (OBC) applications. LLC resonant converter has the advantage of achieving zero‐voltage switching for variable frequency and different load conditions. Compared with conventional fundamental harmonic approximation method, operation‐mode analysis based on the time domain model provides an accurate description of resonant current, voltage and DC gain. In this study, the efficiency‐oriented modified method is proposed based on the operation‐mode analysis. The converter inductance ratio, characteristic impedance and transformer turns ratio are optimised and both‐side soft switching can be achieved in the high output voltage region. Conduction loss can be minimised by optimising resonant parameters. Finally, a high‐efficiency design method is proposed and validated through experiments on a 3.3kW prototype applied in OBC. The prototype of the LLC resonant converter has been tested for dynamic charging voltage (230–430V) with a peak efficiency value of 98.5%. [ABSTRACT FROM AUTHOR]

In the conventional full-bridge LLC converter, the duty cycle is kept as 0.5 and the phase-shift angle of the half-bridge modules is 0° to be a symmetrical operation, which makes the resonant tank operating frequency only equal to the switching frequency of the power devices. By regulating the duty cycles of the upper and lower switches in each half-bridge module to be 0.75 and 0.25 and the phase-shift angle of the half-bridge modules to be 180°, the asymmetrical duty cycle controlled full-bridge LLC resonant converter is derived. The proposed asymmetrical duty cycle controlled scheme halves the switching frequency of the primary switches. As a result, the driving losses are effectively reduced. Compared with the conventional full-bridge LLC converter, the soft-switching condition of the derived asymmetrical controlled LLC converter becomes easier to reduce the resonant current. Consequently, the conduction losses are decreased and the conversion efficiency is improved. The asymmetrical control scheme can be also extended to the stacked structure for high input voltage applications. Finally, two LLC converter prototypes both with 200-kHz resonant frequency for asymmetrical and symmetrical control schemes are built and compared to validate the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

A new approach to the description of resonant tunneling current through a molecule is developed based on a one-electron kinetic equation for the electrodes-molecule system. Expressions for the steadystate population of the level of an extra electron on the molecule and for the current strength as functions of the temperature and voltage across the electrodes are derived. [ABSTRACT FROM AUTHOR]

Two estimation methods for a backward impedance of a power distribution system are proposed in this paper. According to the first method, the backward impedance is estimated based on information obtained from the frequency response of a transient current flowing into a capacitor connected to a distribution line. The backward impedance is determined from the attenuation constant and the resonant frequency calculated using the capacitance and the impedance of the power distribution system. These parameters can be reliably obtained from a frequency response of the transient current using the least square method. The accuracy of the method strongly depends on the origin on the time axis for Fourier transform. An additional estimate of the time-origin is required for an accurate estimation of the backward impedance. The second method estimates the backward impedance using two transient current waveforms obtained by alternately connecting different capacitors to a distribution line. The backward impedance can be represented as a function of the frequency responses of these currents. Since this method is independent from the time-origin, it is suitable for automatic measurements of the backward impedance. Proposed methods are applicable to the estimation of harmonic currents in distribution systems. In this paper, harmonic currents flowing through a distribution line are calculated based on the estimated backward impedance and on the measured values of voltage harmonics obtained by the instrument developed by the authors. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 28–40, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20900 [ABSTRACT FROM AUTHOR]