• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.739-749
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• 2015

A new conceptual dual-buoy Wave Energy Converter (WEC) for the enhancement of energy extraction efficiency is suggested. Based on actual wave data, the design process for the suggested WEC is conducted in such a way as to ensure that it is suitable in real sea. Actual wave data measured in Korea's East Sea (position: $36.404N^{\circ}$ and $129.274E^{\circ}$) from May 1, 2002 to March 29, 2005 were used as the input wave spectrum for the performance estimation of the dual-buoy WEC. The suggested WEC, a point absorber type, consists of two concentric floating circular cylinders (an inner and a hollow outer buoy). Multiple resonant frequencies in proposed WEC affect the Power Ttake-off (PTO) performance of the WEC. Based on the numerical results, several design strategies are proposed to further enhance the extraction efficiency, including intentional mismatching among the heave natural frequencies of dual buoys, the natural frequency of the internal fluid, and the peak frequency of the input wave spectrum.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1122-1132
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• 2019

In this paper, aiming at high-voltage applications, transformer windings schemes of multiple-output two-transistor flyback converters are investigated, which are mainly based on the stray capacitances effect. First, based on a transformer model including equivalent stray capacitors, the operational principle of the converter is presented, and the main influence of its stay capacitors is determined. Second, the windings structures of the transformer are analyzed and designed based on the stray capacitances effect. Third, the windings arrangements of the transformer are analyzed and designed through a coupling analysis of the secondary windings and a stray capacitance analysis between the primary and secondary windings. Finally, the analysis and design conclusions are verified by experimental results obtained from a 60W laboratory prototype of a multiple-output two-transistor flyback converter.

• Journal of IKEEE
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• v.15 no.4
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• pp.330-338
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• 2011

In this paper, a current-mode buck-boost converter using Multiple switching devices is presented. The efficiency of the proposed converter is higher than that of conventional buck-boost converter. In order to improve the power efficiency at the high current level, the proposed converter is controlled with PWM(pulse width modulation) method. The converter has maximum output current 300mA, input voltage 3.3V, output voltage from 700mV to 12V, 1.5MHz oscillation frequency, and maximum efficiency 90%. Moreover, this paper proposes watchdog circuits in order to ensure the reliability and to improve the performance of dc-dc converters. An electrostatic discharge(ESD) protection circuit for deep submicron CMOS technology is presented. The proposed circuit has low triggering voltage using gate-substrate biasing techniques. Simulated result shows that the proposed ESD protection circuit has lower triggering voltage(4.1V) than that of conventional ggNMOS(8.2V).

• Journal of Power Electronics
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• v.17 no.3
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• pp.632-640
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• 2017

Input series output independent (ISOI) dc-dc converter systems are suitable for high voltage input and multiple output applications with low voltage rating switches. This paper proposes a novel control strategy consisting of one output voltage regulating (OVR) control loop and n-1 (n is the number of modules in the ISOI system) input voltage sharing (IVS) control loops. An ISOI system with the proposed control strategy can be applied to applications where the output loads of each module are the same. Under these conditions, IVS can be achieved and output voltages copying can be realized in an ISOI system. In this control strategy there is only one controller for each module and the design process of the control loops is simple. Since no central controller is needed in the system, modularity of the system is improved. The operation principle of the new control strategy is introduced and the control effect is simulated. Then the output power and voltage characteristics of an ISOI system under this new control strategy are analyzed. The stability of the proposed control strategy is explored base on a Hurwitz criterion, and the design guide line of the control strategy is given. A two module ISOI system prototype is fabricated and tested in the laboratory. Experimental results verify the effectiveness of the proposed control strategy.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1037-1047
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• 2017

The Differential Power Processing (DPP) converter is a promising multi-module photovoltaic inverter architecture recently proposed for photovoltaic systems. In this paper, a DPP converter architecture, in which each PV-panel has its own DPP converter in shunt, performs distributed maximum power point tracking (DMPPT) control. It maintains a high energy conversion efficiency, even under partial shading conditions. The system architecture only deals with the power differences among the PV panels, which reduces the power capacity of the converters. Therefore, the DPP systems can easily overcome the conventional disadvantages of PCS such as centralized, string, and module integrated converter (MIC) topologies. Among the various types of the DPP systems, the feed-forward method has been selected for both its voltage balancing and power transfer to a modified H-bridge inverter that needs charge balancing of the input capacitors. The modified H-bridge multi-level inverter had some advantages such as a low part count and cost competitiveness when compared to conventional multi-level inverters. Therefore, it is frequently used in photovoltaic (PV) power conditioning system (PCS). However, its simplified switching network draws input current asymmetrically. Therefore, input capacitors in series suffer from a problem due to a charge imbalance. This paper validates the operating principle and feasibility of the proposed topology through the simulation and experimental results. They show that the input-capacitor voltages maintain the voltage balance with the PV MPPT control operating with a 140-W hardware prototype.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.23-30
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• 2011

This paper presents a Single-Inductor Multiple-Output (SIMO) DC-DC Converter with a negative feedback selection circuit to improve a regulation property at light load and to generate independent multiple outputs. The conventional SIMO DC-DC converter with a fixed negative feedback circuit cannot regulate correctly at light load. The SIMO DC-DC converter with the proposed negative feedback selection circuit has been designed in 0.35um 2-poly 3-metal BCDMOS. This converter is dual output boost converter with the 1.5V input and 2.5V, 3.0V output. The power conversion efficiency varies from 59% at 10mA loads to 85% at 50mA loads.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.195-196
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• 2012

In recent years, in an effort to improve the efficiency and the power density of the front-end power factor correction(PFC), the interleaving of multiple converter is employed. The conventional interleaved continuous conduction mode(CCM) boost PFC converter requires input and output voltage sensing and three current sensing to obtain current balancing between modules. In this paper, the interleaved CCM PFC converter based on modulated carrier control is proposed. With the proposed method, two phase interleaved PFC can be realized simply without line voltage sensing resistor and can achieve current balancing without additional current sensing resistor on common return path. The simulation studies are carried out to verify the effectiveness of the proposed control scheme.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1132-1136
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• 2014

In the context of increasing electric energy consumption in a data center, energy efficiency improvement is strongly emphasized. In a data center, electric energy is largely consumed by DC power supply system, which is based on a rectifier composed by multiple parallel converters. Therefore, rectifier efficiency must be improved for minimizing loss of DC power supply system. Rectifier efficiency can be modulated by load allocation to converters because converter efficiency depends on input AC power. In this paper, we propose a new control method to maximize rectifier efficiency. The method can control load allocation to converters by introducing active power converter control scheme and start-and-stop of converters. In order to illustrate optimal load allocations in a rectifier, a maximization problem of rectifier efficiency is formulated as a nonlinear optimization one. The problem is solved by Lagrangian relaxation method and the computation results provide the validity of proposed method.

• Journal of Power Electronics
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• v.10 no.3
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• pp.245-250
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• 2010

Input-series-output-parallel (ISOP) converters consisting of multiple modular DC/DC converters can enable low voltage rating switches to be used under high voltage input applications. This paper presents a digital control strategy, which can achieve equal sharing of input voltage for a modular ISOP system consisting of two-transistor forward DC/DC converters by forcing the input voltages of neighboring modules to be equal. The proposed scheme is analyzed using small signals analysis based on the state space average method. The performance of the proposed control strategy is verified with an experimental prototype of an ISOP converter made up of three two-switch forward converters.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2272-2283
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• 2016

This paper proposes a power conditioning system (PCS) for distributed photovoltaic (PV) applications using an asymmetric cascaded multilevel inverter with a single PV source. One of the main disadvantages of the cascaded multilevel inverters in PV systems is the requirement of multiple isolated DC sources. Using multiple PV strings leads to a compromise in either the voltage balance of individual H-bridge cells or the maximum power point tracking (MPPT) operation due to localized variations in atmospheric conditions. The proposed PCS uses a single PV source with a flyback DC-DC converter to facilitate a reduction of the required DC sources and to maintain the voltage balance during MPPT operation. The flyback converter is used to provide input for low-voltage H-bridge cells which processes only 20% of the total power. This helps to minimize the losses occurring in the proposed PCS. Furthermore, transient analyses and controller design for the proposed PCS in both the stand-alone mode and the grid-connection mode are presented. The feasibility of the proposed PCS and its control scheme have been tested using a 1kW hardware prototype and the obtained results are presented.