정지훈 교수

A bidirectional full-bridge CLLC resonant converter using a new symmetric LLC-type resonant network is proposed for a low-voltage direct current power distribution system. This converter can operate under high power conversion efficiency because the symmetric LLC resonant network has zero-voltage switching capability for primary power switches and soft commutation capability for output rectifiers. In addition, the proposed topology does not require any snubber circuits to reduce the voltage stre

In this paper, an online induction motor diagnosis system using motor current signature analysis (MCSA) with advanced signal-and-data-processing algorithms is proposed. MCSA is a method for motor diagnosis with stator-current signals. The proposed system diagnoses induction motors having four types of faults such as breakage of rotor bars and end rings, short-circuit of stator windings, bearing cracks, and air-gap eccentricity. Although MCSA is one of the most powerful online methods for diagnos

A LLC resonant topology is analyzed to derive efficiency and cost optimal design for wide input ranges and load variations. In the LLC converter, a wide range of output power is controlled with only a narrow variation in operating frequency since this converter is capable of both step-up and stepdown. In addition, ZVS turn-on and ZCS turn-off of MOSFETs and diode rectifiers can be achieved over the entire operating range. Finally, the inductance of a resonant tank in the primary side can be merg

The increased integration of fuel cells with power electronics, critical loads, and control systems has prompted recent interest in accurate electrical terminal models of the polymer electrolyte membrane fuel cell. Advancement in computing technologies, particularly parallel computation techniques and various real-time simulation tools, has allowed the prototyping of novel apparatus to be investigated in a virtual system under a wide range of realistic conditions repeatedly, safely, and economic

Real-time simulation and fast prototyping with power electronics, critical loads, and control systems have prompted recent interest in accurate electrical terminal models of photovoltaic (PV) panels and array systems. Advancement in computing technologies have allowed the prototyping of novel apparatus to be investigated in a virtual system under wide range of realistic conditions repeatedly, safely, and economically. This paper accesses numerical iteration methods, selects appropriate technique

A bifilar winding method is proposed for the center-tapped transformer which includes integrated resonant inductance in an LLC resonant converter in order to improve the balance of its resonant network and power conversion efficiency. This method can reduce resonance imbalance and transformer inefficiency caused by leakage inductance imbalance in the secondary side of the transformer. As a result, the proposed bifilar winding method employed in the center-tapped transformer maintains the balance

A bidirectional full-bridge LLC resonant converter with a new symmetric LLC-type resonant network using a digital control scheme is proposed for a 380V dc power distribution system. This converter can operate under high power conversion efficiency since the symmetric LLC resonant network has zero voltage switching capability for primary power switches and soft commutation capability for output rectifiers. In addition, the proposed topology does not require any clamp circuits to reduce the voltag

A design methodology for transformers including integrated and center-tapped structures for LLC resonant converters is proposed. In the LLC resonant converter, the resonant inductor in the primary side can be merged in the transformer as a leakage inductance. And, the absence of the secondary filter inductor creates low voltage stress on the secondary rectifiers and is cost-effective. A center-tapped structure of the transformer secondary side is widely used in commercial applications because of

Flyback converters are widely used in industrial and commercial products because of their advantages of simple structure and low cost. Energy and environmental conservation have prompted interest in high efficiency and low standby power consumption in switch mode power supply applications. However, it is difficult to satisfy both conditions simultaneously because of conflicting design considerations. A novel active clamp control method is proposed for improving power conversion efficiency and re

A corrosion model of a rotor-bar-under-fault progress in induction motors is presented for simulations of induction machines with a rotor-bar fault. A rotor-bar model is derived from the electromagnetic theory. A leakage inductance of the corrosion model of a rotor bar is calculated from the relations of magnetic energy, inductance, current, and magnetic-field intensity by Ampere's law. The leakage inductance and resistance of a rotor bar varies when the rotor bar rusts. In addition, the skin ef

Stability improvement of V/f-controlled induction motor drive systems by a dynamic current compensator is proposed. The proposed method uses a dynamic current compensator to improve the stability of the V/f-controlled induction motor drive systems. This method is easy to implement and helps eliminate the oscillations causing the instability of V/f-controlled induction motor drive systems.

A feed-forward frequency compensator for an asymmetrical pulsewidth modulated (APWM) half-bridge (HB) flyback converter is proposed to increase its power conversion efficiency. Under a variable input voltage, the APWM HB flyback converter cannot be satisfied with the zero-current switching (ZCS) condition of output rectifiers because the variation of the turn-ON duration of main switches, which regulate the output voltage, induces their improper turn-OFF duration. This means that the resonance o

As a bi-directional isolated interface for solid state transformer applications, practical design considerations of a dual active bridge (DAB) converter are proposed by means of a detailed mathematical model based on the converter's steady state operations. The DAB converter is useful in isolated bi-directional power conversion applications due to high performance, high efficiency, and bidirectional control manner. However, design considerations should be taken into account to overcome the disad