• Journal of Power Electronics
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• v.14 no.6
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• pp.1093-1099
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• 2014

This paper proposes a power conversion topology involving a multi-winding transformer and converters. The fundamental idea is described with circuit diagrams, and the voltage output of the proposed topology is analyzed mathematically. The effectiveness of the topology is discussed with test results from a small-scale power conversion system. When conventional hardware consisting of two-level converters and a transformer is employed, multi-level voltage outputs can be applied to the transformer windings by the proposed method.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.1
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• pp.55-60
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• 2010

For battery-powered device applications, which grow rapidly in the electronic market today, low-power becomes one of the most important design issues of CMOS VLSI circuits. A multi-VDD system, which uses more than one power-supply voltage in the same system, is an effective way to reduce the power consumption without degrading operating speed. However, in the multi-VDD system, level converters should be inserted to prevent a large static current flow for the low-to-high conversion. The insertion of the level converters induces the overheads of power consumption, delay, and area. In this paper, we propose a new level converter which can provide the level up/down conversions for the various input and output voltages. Since the proposed level converter uses only one power-supply voltage, it has an advantage of reducing the complexity in physical design. In addition, the proposed level converter provides lower power and higher speed, compared to existing level converters.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.136-145
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• 2009

This paper proposes control methods and simulation models of a driving system, which consists of converters and inverters, for high speed trains employing multi-level power converters. The control method of a single phase three-level converter for high-speed trains is designed to use DC values instead of instantaneous current values which are usually used in single-phase application, so that it results in a fast and robust voltage control response. In addition, simulation models of Space Vector Pulse Width Modulation (SVPWM) for single phase three-level converters as well as three level inverters are proposed. Experimental results demonstrate the validity of the simulation model for three-level inverters.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• Journal of Power Electronics
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• v.15 no.1
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• pp.96-105
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• 2015

In recent years, the multilevel converters have been given more attention due to their modularity, reliability, failure management and multi stepped output waveform with less total harmonic distortion. This paper presents a novel symmetric multilevel inverter topology with reduced switching components to generate a high quality stepped sinusoidal voltage waveform. The series and parallel combinations of switches in the proposed topology reduce the total number of conducting switches in each level of output voltages. In addition, a comparison between the proposed topology with another topology from the literature is presented. To verify the proposed topology, the computer based simulation model is developed using MATLAB/Simulink and experimentally with a prototype model results are then compared.

• Journal of Power Electronics
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• v.13 no.2
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• pp.296-303
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• 2013

This paper proposes a high efficiency three-phase cascaded phase shifted H-bridge multi-level inverter without DC/DC converters for grid-tied multi string photovoltaic (PV) applications. The cascaded H-bridge topology is suitable for PV applications since each PV module can act as a separate DC source for each cascaded H-bridge module. The proposed phase shifted H-bridge multi-level topology offers advantages such as operation at a lower switching frequency and a lower current ripple when compared to conventional two level topologies. It is also shown that low ripple sinusoidal current waveforms are generated with a unity power factor. The control algorithm permits the independent control of each DC link voltage with a maximum power point for each string of PV modules. The use of the controller area network (CAN) communication protocol for H-bridge multi-level inverters, along with localized PWM generation and PV voltage regulation are implemented. It is also shown that the expansion and modularization capabilities of the H-bridge modules are improved since the individual inverter modules operate more independently. The proposed topology is implemented for a three phase 240kW multi-level PV power conditioning system (PCS) which has 40kW H-bridge modules. The experimental results show that the proposed topology has good performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1958-1968
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• 2015

In this paper, a new definition of short-circuit ratio concept for multi-converter HVDC systems is proposed. Analysis results of voltage interaction between converters show that the reactive power-voltage characteristic of a converter has a dominant effect on voltage interaction level compared with its active power-voltage characteristic. Such a relation between converter reactive power and voltage interaction level supports taking the former into account in the definition of short-circuit ratio concept for multi-converter systems. The proposed definition is verified by the method of maximum power curve for various system configurations. Furthermore, a formula to calculate transient overvoltage for multi-converter systems is derived based on the proposed definition, and the efficiency of the derived formula is verified.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.109-117
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• 2017

This paper describes the design and implementation of a unit module for a 10 kVA class 13.2 kV/220 V unidirectional solid-state transformer (SST) with silicon-carbide metal-oxide-semiconductor field-effect transistors. The proposed module consists of an active-front-end (AFE) converter to interface 1320 V AC voltage source to 2500 V DC link and an isolated resonant DC-DC converter for 500 V low-voltage DC output. The design approaches of the AFE and the isolated resonant DC-DC converters are addressed. The control structures of the converters are described as well. The experiments for the converters are performed, and results verify that the proposed unit module can be successfully adopted for the entire SST operation.

• Journal of Power Electronics
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• v.16 no.2
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• pp.522-531
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• 2016

This paper proposes a new NLC (Nearest Level Control) scheme for MMCs (Modular Multilevel Converters), which offers voltage ripple reductions in the DC capacitor of the SM (Sub-Module), the output voltage harmonics, and the switching losses. The feasibility of the proposed NLC was verified through computer simulations. Based on these simulation results, a hardware prototype of a 10kVA, DC-1000V MMC was manufactured in the lab. Experiments were conducted to verify the feasibility of the proposed NLC in an actual hardware environment. The experimental results were consistent with the results obtained from the computer simulations.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.250-253
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• 2001

This paper is proposed a sinusoidal input voltage Multi-level AC-DC Converter using transformer. In this paper Multi-level PWM Control converter which controls input current by combining buck Converters together to improve input current characteristic, and confirmed its validity throughout simulation and experiment. This method, which is multiplying and duplicating output of converter of equal capacity, is able to control unit power factor of input current, reduce the problem caused by high frequency switching, and apply to high power converter because filter is not necessary.