• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.191-199
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• 2016

Conventional two-level Zeta converters have drawbacks, such as high voltage stresses and high current ripples. To address these problems, a three-level Zeta converter that uses a couple inductor is proposed in this study. The proposed converter utilizes the three-level power switching circuit to reduce the voltage stresses and inductor current ripples. Compared with the conventional converter, the proposed converter can improve power efficiency and power density. A 500 W prototype circuit is used to verify the operation and performance of the proposed converter via experimental results.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.126-129
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• 1996

This paper study on the control method of 3-level converter. The control of converter is composed of active power control for controlling a output voltage and of reactive power control for high power factor drives. And also, output central voltage is controlled by sensing a each condensor voltage of bank connected the part of dc.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.342-348
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• 2013

In this paper, an improved non-isolated 3-level high step-up boost converter is proposed. By using the well known duality principle, the proposed converter is derived from two-phase buck converter. Compared with the traditional boost converter and 3-level boost converter, the proposed converter can obtain very high voltage conversion ratio and the voltage stress of switching devices and diodes is only 1/4 of the output voltage. A 1 kW prototype converter is built and tested to verify performances of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.464-470
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• 2015

In this paper, a non-isolated three-level high step-up boost converter with output voltage balancing is proposed. By adding one extra inductor to the conventional three-level boost converter, the proposed converter is derived. Compared with the traditional boost converter and the three-level boost converter, the proposed converter can obtain very high voltage conversion ratio, and the voltage and current stress of switching devices and diodes are reduced. A 2.7 kW prototype converter is built and tested to verify performances of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.96-105
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• 2021

Large-scale power converters consist of series or parallel module combinations. In these modular converter systems, the interleaving technique can be applied to improve capacitor reliability by reducing the ripple of the I/O current in which each module operates as a phase difference. However, when applying the interleaving technique for conventional three-level boost converters, the short-circuit period of the converter can be an obstacle. Such problem is caused by the absence of a low-level inductor of the conventional three-level boost converter. To solve this problem, a three-level boost converter with a low-level inductor is proposed and analyzed to enable interleaved operation. In the proposed circuit, the current ripple of the output capacitor depends on the neutral point connections between the modules. In this study, the ripple current is analyzed by the neutral point connections of the three-level boost converter that has a low-level inductor, and the effectiveness of the proposed circuit is proven by simulation and experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.36-43
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• 2017

This paper describes a hybrid multi-output three-level DC/DC converter suitable for a wide, high-input voltage range of an auxiliary power supply for a high-power photovoltaic generating system. In a high-power photovoltaic generating system, the solar panel output voltage depends on solar radiation quantity and varies from 450Vdc to 1100Vdc. The proposed hybrid multi-output three-level DC/DC converter, which is an auxiliary power supply, would be used as power source for control printed circuit boards and relay and cooling fans in a high-power photovoltaic generating system. The proposed multi-output ($24V_{DC}/30A$, $230V_{DC}/5A$) hybrid three-level boost converter, which uses an energy recovery snubber, is controlled by variable-frequency and phase-shifted modulations and can achieve zero-voltage switching with all operating conditions of input voltage and load range. Experimental results of a 2kW prototype are evaluated and implemented to verify the performance of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.535-542
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• 2017

This paper proposes a simple 3-level interleaved charger-discharger for the uninterruptible power supply (UPS) with various combinations of battery cells. The proposed converter not only improves charging and discharging efficiency, but also reduces the physical volume and the cost. Furthermore, the converter also offers the capability of the neutral point voltage, so that more stable operation can be obtained. In addition, the proposed converter significantly reduces the ripple current of the battery inductor, thereby providing an expected life extension of the battery. Experimental results for a 300kVA UPS prototype verify the validity of the proposed converter. The proposed charger-discharger is suitable for UPSs and energy storage systems (ESSs) with wide input battery voltage ranges.

• Journal of Power Electronics
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• v.15 no.3
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• pp.652-659
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• 2015

This paper presents a new hybrid soft switching dc-dc converter with a low circulating current and high circuit efficiency. The proposed hybrid converter includes two sub-converters sharing two power switches. One is a three-level PWM converter and the other is a LLC converter. The LLC converter and the three-level converter share the lagging-leg switches and extend the zero-voltage switching (ZVS) range of the lagging-leg switches from nearly zero to full load since the LLC converter can be operated at f_sw (switching frequency) $\approx$ f_r (series resonant frequency). A passive snubber is used on the secondary side of the three-level converter to decrease the circulating current on the primary side, especially at high input voltage and full load conditions. Thus, the conduction losses due to the circulating current are reduced. The output sides of the two converters are connected in series. Energy can be transferred from the input voltage to the output load within the whole switching period. Finally, the effectiveness of the proposed converter is verified by experiments with a 1.44kW prototype circuit.

• Journal of Power Electronics
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• v.14 no.3
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• pp.478-487
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• 2014

This study presents a new interleaved three-level zero-voltage switching (ZVS) converter for high-voltage and high-current applications. Two circuit cells are operated with interleaved pulse-width modulation in the proposed converter to reduce the current ripple at the input and output sides, as well as to decrease the current rating of output inductors for high-load-current applications. Each circuit cell includes one half-bridge converter and one three-level converter at the primary side. At the secondary side, the transformer windings of two converters are connected in series to reduce the size of the output inductor or switching current in the output capacitor. Based on the three-level circuit topology, the voltage stress of power switches is clamped at $V_{in}/2$. Thus, MOSFETs with 500 V voltage rating can be used at 800 V input voltage converters. The output capacitance of the power switch and the leakage inductance (or external inductance) are resonant at the transition interval. Therefore, power switches can be turned on under ZVS. Finally, experiments verify the effectiveness of the proposed converter.

• Journal of Power Electronics
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• v.14 no.3
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• pp.499-506
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• 2014

This paper proposes a 3 kW single-phase bi-directional multi-level converter for energy storage applications. The proposed topology is based on the H-bridge structure with four switches connected to the DC-link. A simple phase opposition disposition PWM method that requires only one carrier signal is also suggested. The switching sequence to balance the capacitor voltage is considered. The topology can be extended to a nine-level converter or a three-phase system. The operating principle of the proposed converter is verified through a simulation and an experiment.