Byeong-Mun Song

A three-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems

This paper describes a newly developed three-level dc-dc converter with wide-input voltage operations for ship-electric-power-distribution systems. The proposed converter is designed with zero-voltage-switching (ZVS) techniques. The operational principles, design details and performances of the converter are discussed along with soft-switching characteristics through experimental results. Furthermore, design criteria on the dc-dc converter are focused on the minimization of the circulation current between main switches and a transformer under soft switching. The converter has achieved about 95% efficiency over wide 7-kW load conditions.

Contactless inductive power pickup system for Maglev applications

This paper describes a newly developed contactless inductive power pickup system for Maglev applications. The system consists of a loosely coupled transformer and two high-frequency power converters. Furthermore, the proposed inductive system was verified through various simulations and experiments. System performances such as magnetic coupling, energy efficiency, and power factor correction effects are included.

Characteristics and utilization of a new class of low on-resistance MOS-gated power device

A new class of MOS-gated power semiconductor devices Cool MOS/sup TM/ has been introduced with a supreme conducting characteristic that overcomes the high on-state resistance limitations of high voltage power MOSFETs. From the application point of view, an immediate and very frequently asked question arises: does this device behave like a MOSFET or an insulated gate bipolar transistor (IGBT)? The goal of this paper is to compare and contrast the major similarities and differences between this device and the traditional MOSFET and IGBT. In this study, the new device is fully characterized for its (1) conduction characteristics, (2) switching voltage, current, and energy characteristics, (3) gate drive resistance effects, (4) output capacitance, and (5) reverse bias safe operating areas. Experimental results indicate that the conduction characteristics of the new device are similar to the MOSFET but with much smaller on-resistance for the same chip and package size. The switching characteristics of the Cool MOS are also similar to the MOSFET in that they have fast switching speeds and do not have a current tail at turn-off. However, the effect of the gate drive resistance on the turn-off voltage rate-of-rise (dv/dt) is more like an IGBT. In other words, a very large gate drive resistance is required to have a significant change on dv/dt, resulting in a large turn-off delay. Overall, the device was found to behave more like a power MOSFET than like an IGBT.

A soft-switching high-voltage active power filter with flying capacitors for urban Maglev system applications

This paper describes a newly developed soft-switching high-voltage active power filter for urban Maglev system applications. The active filter consists of a flying capacitor-based multilevel converter and a soft-switching circuit with coupled inductors. Various aspects like operation, design, analysis and control are discussed in depth and verified through computerized simulation and experimental results. In addition, the study of voltage balancing provided the fundamental high-level solutions to flying capacitor based multilevel converter and inverter applications without additional passive balancing circuits.

Design and control of a grid-connected three-phase 3-level NPC inverter for Building Integrated Photovoltaic systems

This paper presents the design and control of a grid-connected three-phase 3-level Neutral Point Clamped (NPC) inverter for Building Integrated Photovoltaic (BIPV) systems. The system consists of a PV array, boost DC/DC converter, 3-level NPC inverter, LC filter and the grid. The 3-level NPC inverter is designed without a galvanic isolation transformer and its current controller is developed to minimize leakage currents though common-mode voltage loops in the PV systems. A prototype 13kW NPC inverter with a LC filter was fabricated and tested, resulting in a low total harmonics distortion (THD) of less than 3% THD and 97.5% efficiency at the peak load. The detail simulation and test results are discussed.

Performance analysis and evaluation of a multifunctional grid-connected PV system using power hardware-in-the-loop simulation

This paper describes the performance analysis of a multi-functional grid-connected photovoltaic (PV) system using power hardware-in-the-loop simulation (PHILS). An intelligent control scheme for the multi-functional grid-connected PV power generation system is proposed and verified though the power hardware-in-the-loop simulation computer simulation and the digital signal processor TMS320F2812 controller under various irradiation and load conditions. The proposed hardware and control algorithm can easily be applied to the power quality enhancement of distribution system and improves the utilization of PV system.

RTDS-based real time simulations of grid-connected wind turbine generator systems

This paper presents the modeling and analysis of grid-connected wind turbine systems using real time digital simulator (RTDS). The different modeled systems of wind turbine generator systems (WTGS) such as permanent magnet synchronous generator (PMSG), induction generator (IG), synchronous generator (SG) and doubly fed induction generator (DFIG) are simulated. Three control schemes for 3 MW WTGSs of squirrel cage induction generator (SCIG), DFIG with back-to-back converter and PMSG with back-to-back converter are designed for the modeled systems. The simulation results show the performances of each type of WTGS under the same wind speed pattern. It has been verified that the RTDS based realtime simulations of grid-connected wind turbine generator systems to be effectively employed to evaluate the control schemes and output performances of different types of WTGSs.

Switching characteristics of NPT- and PT-IGBTs under zero-voltage switching conditions

In this paper, switching characteristics of nonpunch through (NPT) and punch through (PT) insulated gate bipolar transistors (IGBTs) are evaluated under zero-voltage switching (ZVS) conditions. Through the physics-based modeling and experiments, the interaction between the external circuit and the physical IGBT internal model under ZVS operation is evaluated. The effects of the external snubber capacitor on the turn-off tail current are modeled and analyzed with the Saber circuit simulator. The turn-on switching characteristics are evaluated for the study of switching losses. This study provides guidelines for designing IGBTs that are suitable for soft switching and for selection of appropriate snubbing capacitors in soft-switching inverter and converter applications.

Low frequency current reduction using a quasi-notch filter operated in two-stage DC-DC-AC grid-connected systems

For a single-phase grid-connected power system, output power is pulsated instantaneously with a double-fundamental frequency. Accordingly, the current drawn from renewable energy sources tends to be pulsated and contains low frequency ripple components, which causes several issues including a power harvesting deterioration and energy sources life shortening. This paper proposes a novel power pulsation decoupling scheme to reduce low frequency ripple current with a fast voltage loop. Proper control design based the small-signal model of two-stage dc-dc-ac converter is presented in a frequency domain analysis, and its experimental waveforms are provided to verify the effectiveness.

Improved design and control of proportional resonant controller for three-phase voltage source inverter

This paper presents an improved current control technique for a three-phase grid-connected DC/AC inverter using proportional resonant (PR) control. The proposed PR current control strategy is designed with tracking the reference current produced by an instantaneous power-based current reference generation method. In the controller the instantaneous power-based current reference generation method eliminates the delay in average power-based current reference generation methods, so a fast controller is required to maximize power delivery. The prosed PR controller also provides solutions for the drawbacks associated with conventional PI controllers that have slow dynamics and high distortion in the control feedback signal. For validation, simulation results of this grid-side control method are presented.