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An advanced LLC series resonant converter (SRC) with resonant switched-capacitor technique is proposed in this paper to satisfy the high voltage and high step-down requirements. The series structure in the high-voltage side, together with a switched capacitor and its resonant inductor, effectively reduces the voltage stress on the high-side switches to half of the input voltage, which enhances the...
This paper proposes the size reduction methods for two-stage Boost-LLC converter to achieve high power density in 60W AC-DC adapter. The two-stage converter has high component count, and the passive components such as inductor, transformer, and capacitor occupy the most of the area. In order to make the converter have small size, this paper proposes the size reduction methods of passive components:...
Till now, the various types of the half-bridge (HB) converters with output inductor have been developed, and they exhibit a good performance in medium power applications such as the server power supplies and personal computer (PC) power supplies requiring the hold-up time conditions and high output current. However, they have common problems such as high snubber loss and switch turn-off losses caused...
Symmetry Cockcroft Walton multiplier is a typical cascade voltage multiplier. It is an attractive alternative to the high voltage (HV) transformer with high turn ratio and bridge rectifier in the HV generator in medical X-ray machine. It can reduce the stray capacitance of the HV transformer. However, previous work reports that the parasitic capacitances in the multiplier itself can be added to the...
This paper describes two basic approaches to calculate the small signal behavior of the resonant LLC-converter. There are no limitations to the underlying time domain model, simulations based on Spice are possible. The theory behind the ‘Virtual Network Analyzer’ and ‘Sampled-Data Modeling’ approach is described in detail. An analysis of the performance and effort to implement these methods is presented...
This paper takes a fundamental look at the mechanisms underlying the stability of single-edge pulse-width modulated current regulator loops. The analysis applies to continuous-time or highly oversampled digital current regulators. It is shown that pulse-width modulation is essentially a sampling process. Associated with this sampling process is a small-signal z-domain model of the pulse-width modulator...
While hysteresis current control offers the benefits of a fast dynamic response and inherent overcurrent protection, its variable switching frequency and inherent two-level switching response make it unsuitable for many applications. This paper presents a new approach for three-level hysteresis control of a single phase grid-connected inverter that overcomes these limitations. The strategy adjusts...
This paper investigates a new approach in developing a current control method utilizing the grid virtual flux estimation technique for reducing the number of sensors and to enhance the control performance of the grid connected three phase ac-dc converter system. Accordingly, a virtual flux oriented control (VFOC) with the improvement of virtual flux estimation technique has been proposed in this work...
This paper discusses a novel isolated three-phase AC-DC converter using Modular Multi-level Converter (MMC) topology for a medium voltage application. The MMC at a primary stage of an isolated AC-DC converter can directly convert a three-phase AC into a high-frequency AC voltage of 1 kHz. In this paper, the features of the proposed circuit are discussed according to the voltage ratings of the switching...
The novel DC-DC converter composed of an X-shape diode-capacitor network provides a simple solution for high step-up power conversion in renewable energy applications. With regard to the uni-directional power flow of the diodes, two capacitors are naturally charged in parallel, and discharged in series. Thus, high voltage gain is achieved without extreme large duty ratio. Furthermore, the voltage...
This paper discusses the performance of a large-scale grid-connected photovoltaic system (GCPS) under unbalanced voltage sag conditions in the grid. By applying the droop control to address the low-voltage-ride-through (LVRT) capability, the output currents are no longer sinusoidal due to the oscillations produced in the current references. To deal with this problem a moving average filter (MAF) technique...
This paper presents a division-summation (D-Σ) digital control for a three-phase transformerless bi-directional photovoltaic inverter with wide inductance variation, which can eliminate the leakage ground currents due to panel parasitic capacitance. The bi-directional inverter fulfilling grid connection and rectification with power factor correction has been implemented in the laboratory. The proposed...
A photovoltaic micro-inverter with a half-bridge inverter, half-wave cycloconverter and front-end boost converter is proposed with a series resonant circuit. A PV panel is connected to the micro-inverter via the front-end DC-DC converter. The micro-inverter is integrated to the grid by using the half-wave cycloconverter. The Half-wave cycloconverter and the half-bridge inverter are interfaced by using...
Since PV power output depending on the operating voltage and current, PV systems need maximum power point tracker (MPPT). Further, multiple local maximum power points appear in the power-voltage characteristics under partial shading conditions, finding the global MPP using conventional MPPT is a difficult task. To solve this issue, the authors proposed a PSO technique to solve the problems involved...
The Actively Clamped Resonant DC-Link Inverter(ACRDCLI) has remarkable features of simple structure and high efficiency with only one auxiliary switch. However, there exists unfixed commutation delay in two-amplitude control system, which causes sub-harmonics. This paper presents a DC-Link control strategy for the ACRDCLI. By measuring and analyzing the unfixed delay time, the method shifts forward...
This paper describes the development of a static starting device for a gas turbine. The static starting device is a load commutated inverter (LCI), and also called static frequency converter (SFC). The main objective of this study is to miniaturize the dimensions of the converter structure. For this purpose, electrical ratings, mechanical structures, and several other elements were changed. With these...
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