Dong-Keun Jeong

Optimized Design of Bi-Directional Dual Active Bridge Converter for Low-Voltage Battery Charger

This paper proposes an optimized design of dual active bridge (DAB) converter for low voltage charger. Among various bi-directional DC/DC converters, DAB converter is a high efficiency buck and boost bi-directional DC-DC converter isolated by a high frequency transformer. Battery voltage varies according to the charging status of the battery and the parameters of the DC/DC converter are the same regardless of the battery voltage. When the battery voltage is high, the soft switching (ZVS) region is reduced compared to the low battery voltage. In this paper, variable switching frequency is adopted in order to maximize soft-switching (ZVS) region at the high battery voltage. The same power can be obtained at the same duty regardless of the battery voltage using the variable switching frequency. The proposed method is applied to a 5kW prototype dual active bridge converter, and the experimental results are analyzed and verified.

High power ultrasonic transducer with LLCC resonant converter using digital control algorithm

A variety of applications using ultrasonic transducer is operating at high power in a low frequency range in industry. The resonance frequency shift and electrical impedance change is a common phenomenon in the application of high-power ultrasonic transducer. In order to achieve a stable or consistent results, it is important to track the resonance frequency. To solve these problems, various electrical methods have been described to track the operating frequency. This paper proposes ultrasonic transducer drive system and a simple digital control algorithm for sonicating aluminum alloy. The ultrasound transducer drive system is implemented to verify the proposed digital control algorithm. The proposed digital control algorithm is applied to a 3 kW prototype ultrasound transducer drive system, and the experimental results are analyzed and verified.

Dual active bridge converter for Energy Storage System in DC microgrid

In order to increase the reliability and response speed of an Energy Storage System(ESS), the power management algorithm for ESS is proposed using a dual active bridge(DAB) converter. The DAB converter has been popular, because it operates with high performance, high efficiency, galvanic isolation, and an inherent soft-switching feature. The bi-directional power transmission is a characteristic of the dual active bridge converter, permitting flexible interfacing to energy storage devices. This paper suggests a control strategy for the power management among independent components in ESS system. Its test-bed contains the power management algorithm which consists of a bidirectional DC/DC converter, a renewable energy simulator, DC loads, and a DC-bus protector. The proposed power management algorithm is analyzed, which is verified from the proposed ESS test-bed.

Test-bed implementation of DC microgrid in islanding mode

In order to increase the reliability and response speed of a DC microgrid system, the power management algorithm for autonomous operation is proposed using a DC-bus signaling (DBS) method, instead of the centralized power management system which needs communications among power interfaces. The DC-bus voltage is considered as an information signal of the status of the DC-bus. In addition, DC-bus voltage bands are proposed to classify the scenarios of DC-bus conditions. The DC microgrid components individually operate to achieve the functionality of the system control in the DC-bus voltage band. This paper suggests a control strategy for the power management among independent components in the islanding mode. Its test-bed contains the power management algorithm which consists of a grid-connected AC/DC rectifier, a bidirectional DC/DC converter, a renewable energy simulator, DC loads, and a DC-bus protector. The proposed power management algorithm in the islanding mode is analyzed via simulation result, which is verified from the proposed DC microgrid test-bed.

Dynamic Analysis and Optimal Design of High Efficiency Full Bridge LLC Resonant Converter

In this paper, high efficiency full bridge LLC resonant converter for server power system is introduced. LLC resonant converter was reported in many papers recently because of its simple structure, high efficiency and high switching frequency ability. However, many SMPS designers and field engineers still encounter technical difficulties of power stage design and control scheme due to environmental regulations of power system. This paper clearly presents theoretical and practical details involved with the dynamic analysis and design procedures. The accuracy of dynamic analysis and validity of optimal design are confirmed with both computer simulations and experimental measurement.