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To improve light load efficiency, a three-phase photovoltaic (PV) based microinverter may operate in single-phase, two-phase or three-phase mode depending on the available input power. Therefore, its DC link capacitor may be subjected to large peak-to-peak voltage ripple when operating in phase skipping mode. This paper determines the minimum value of the DC link capacitor by allowing the maximum...
High-voltage and high-current power converters are essential in numerous applications, including shipboard power systems and industrial motor drives. Most of the existing topologies are based on dc-link converters, and use dc-dc or dc-ac power cells to realize a multilevel power converter. Therefore, they require a large number of capacitors with high capacitances. This paper proposes a new modular...
This paper proposes an adaptive DC-bus stabilizer for single-phase grid-connected voltage source converter (VSC) with small-scale renewable energy integration. To enhance converter's power density, the conventional active power decoupling (APD) techniques were adopted to reduce the DC capacitance by compensating the inherent second-order harmonic power ripples in the single-phase VSC. However, it...
This paper introduces a large air-gap capacitive wireless power transfer (WPT) system for electric vehicle charging that achieves a power transfer density exceeding the state-of-the-art by more than a factor of four. This high power transfer density is achieved by operating at a high switching frequency (6.78 MHz), combined with an innovative approach to designing matching networks that enable effective...
At present, the research on the quality of micro-grid power at home and abroad is still at the initial stage, which focuses on the study of the power quality characteristics of micro-sources. There is little research on the quality control of micro-grid power and the power quality adjustment device for microgrid. In particular, there is no literature on the power quality of the microgrids containing...
This paper proposes a control structure of SST (Solid-state-transformer), which consists of MMC (Modular Multi-level Converter) based AC/DC converters and isolated DC/DC converters, to reduce the size of capacitors. The phase separated configuration requires a high capacitance needed for smoothing capacitors due to instantaneous power oscillation at the double line frequency. This paper proposes an...
In single-phase photovoltaic (PV) systems, power mismatching between input and output terminal leads to power pulsation, seriously affecting maximum power point tracking (MPPT). Paralleling an electrolytic capacitor (e-cap) across PV panel to smooth power pulsation seems to be an unreliable method owing to its short lifetime. Various power decoupling methods used in micro-inverters have been proposed...
Capacitive DC links provide the only low-impedance current path connected with an input source during the start-up of many voltage source converters. A soft-start circuit is usually implemented to limit the inrush current. A two-terminal active capacitor is recently proposed which can directly replace conventional passive capacitors in DC links, with reduced cost or size for a given application. The...
Metal-insulator-semiconductor capacitors used as a RC snubber attenuate voltage overshoots which may occur during switching phases. These devices feature good temperature stability up to 200°C and can be integrated very close to power switches on the same transfer substrate. As the capacitors need to withstand high voltages in most applications, thick dielectric layers have to be used, causing significant...
Hybrid DC circuit breakers have the advantages of fast fault current interruption with the solid-state semiconductor devices and low conducting loss with the mechanical switches. Therefore it is suitable to be used in the multi-terminal DC transmission system. The objective of this paper is to determine a voltage sharing between the mechanical switch and the IGBTs in a proposed topology of hybrid...
In this paper, the low voltage and high current driver is used as an example to analyze and suppress the EMC problem caused by DC / DC power conversion. In the process of low-voltage and high-current driver design, the problem of misalignment of the drive signal occurs. The paper analyzes the mechanism of the electromagnetic interference in the switch process, and then detects the electromagnetic...
This paper proposes a current-source parallel resonant Class E inverter with low peak switch current. The proposed circuit consists of two switches, a parallel resonant circuit, a capacitor, an inductor, a choke inductor, and a DC voltage source. The peak current flowing through the switches is no more than the input current, which reduces the current stress of the switching devices. Zero-voltage...
Bulky capacitors are usually needed to buffer the double-frequency ripple power (DFRP) in single-phase power factor correction (PFC) rectifier. It is important to reduce the capacitance requirements for improving the system reliability and power density. In this paper a control method for capacitive idling converter based PFC (CIC-PFC) rectifier is proposed. The DFPR is diverted to the energy transfer...
This paper realizes a high power factor, high reliability, and low cost PMSM drive system with small DC-link capacitor. Compared with conventional bulky electrolytic capacitor for the regulation of DC-link voltage, a small-size film capacitor with capacitance reduction to 1% is used to realize a seneorless PMSM drive with high power factor, high reliability, and high compactness. To overcome high...
The power decoupling strategies of single-phase Z-source/quasi-Z-source inverter (ZSI/qZSI) to handle the inherent double-line-frequency (2ω) power are overviewed. They are categorized as passive and active power decoupling methods. The former suppresses the 2ω ripple by the impedance network, modified modulation methods, or closed-loop damping control. The latter diverts the 2ω ripple to the compensation...
For a wireless transmission system, low efficiency is the most serious problem. Proper capacitance compensation for the system is expected to reduced reactive power and improve system efficiency. In present paper, system performances are studied and compared in two cases, no compensation and compensated by series capacitance. Then variation trend of transmission efficiency with other parameters (frequency,...
This paper deals with the transformation from differential to common mode noise due to slightly unbalanced filter capacitors in a three-phase motor drive system. Indeed, filter components, i.e., inductors and capacitors, can be slightly different due to the tolerance of commercial products usually varying from 5% to 20%. Such components discrepancies result in noise transformation from differential...
We present a summary of the results of an intercomparison of high voltage capacitance between the National Metrology Institutes of Argentina (INTI) and Uruguay (UTE). The traveling standard was a 400 kV, 50 pF capacitor, SF6-isolated. This capacitor was calibrated in each laboratory against their own standards, comparing the results.
We evaluate the flying capacitor multilevel converter (FCMC) with one switched-capacitor cell under asymmetric working condition, as a highly efficient hardware realization for the virtual infinite capacitor (VIC). The VIC is a type of electronic circuit, recently introduced to replace large, expensive and unreliable electrolytic capacitors, mainly intended for smoothing random fluctuations of a DC...
The objective of this paper is to determinate the influence of grading capacitance on breakdown characteristics of a double-break vacuum interrupter. A prototype of double-break vacuum interrupter was built up as a U-type configuration with two 12 kV vacuum interrupters in series. The double-break vacuum interrupter is stressed by a power frequency withstand voltage and a lightning impulse withstand...
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