Chang-Yeol Oh

A High-Efficient Nonisolated Single-Stage On-Board Battery Charger for Electric Vehicles

The design and implementation of a high-efficiency nonisolated single-stage on-board battery charger (OBC) for electric vehicles are presented. Reviewing the conventional topologies, a suitable circuit structure is determined to charge a battery in a wide spectrum of input and output conditions. Additionally, a suitable strategy for a highly efficient OBC is presented through the analysis of selected topology. A detailed theoretical analysis, operating strategy, and experimental results on a 3.7-kW prototype are presented in order to evaluate the performance of the proposed system.

Design of Optimal Resonant Frequency for Series-Loaded Resonant DC-DC Converter in EVs On-Board Battery Charger Application

This paper describes the process of optimal resonant frequency design with full-bridge series-loaded resonant dc-dc converter in a high efficiency 3.3 kW on-board battery charger application for Electric Vehicles and Plug-in Hybrid Electric Vehicles. The optimal range of resonant frequency and switching frequency used for ZVS are determined by considering trade-off between loss of switching devices and resonant network with size of passive/magnetic devices. In addition, it is defined charging region of battery, the load of on-board charger, as the area of load by deliberating the characteristic of resonant. It is verified the designed frequency band by reflecting the defined area on resonant frequency.

Design of resonant network based on power losses analysis of series resonant converter for on-board battery charger in EVs

This paper describes the process of the design of resonant network through power losses analysis of full-bridge series resonant converter in a high efficiency 3.3kW on-board battery charger application for electric vehicles. The losses of switching devices and passive components with transformer are analyzed theoretically by considering losses in the charging area of high voltage Li-ion battery. In addition, theoretical procedures based on losses analysis are possible to optimal design of resonant network in series resonant converter for on-board battery charger application. The parameters and result of the process can be used for analyzing the variation of size and losses. The proposed design process can be verified through calculations in every frequency domain by comparing with operation area.

Optimal design and control of OBC-LDC integrated power unit for electric vehicles

This paper proposes an integrated circuit sharing internal parts of a low voltage DC-DC converter (LDC) and an on-board charger (OBC) for electric vehicles (EVs). The proposed circuit structure can be operated as an OBC standalone mode, a LDC standalone mode, and a simultaneous operating mode. The operating modes of the proposed system are analyzed and the advantages and disadvantages are also discussed. To improve the derived disadvantage, the expanded circuit structure is suggested and applied. Through this, the practicality of the integrated OBC with LDC is enhanced. The additionally suggested circuit is a built-in zero voltage switching (ZVS) buck unit. Prototype rated with 3.3 kW OBC and 1 kW LDC is built and the experimental results are carried out in order to verify the performance and the validity of the proposed power unit.

Topology and Control Scheme of OBC–LDC Integrated Power Unit for Electric Vehicles

This paper proposes a novel integrated low-voltage dc-dc converter (LDC) and onboard battery charger (OBC) for electric vehicles (xEVs) that share heatsinks, terminals, sensing circuits, and circuit components between both parts. The proposed OBC-LDC integrated power unit (OLPU) can be simplified by modifying the internal connections of the vehicle, thus eliminating the cost of high-power cables. In addition, the OLPU decreases the number of circuit components and increases the total power density by combining or sharing heatsinks, terminals, sensing circuits, and circuit components. Further, the proposed circuit satisfies the performance characteristics of conventional OBCs and LDCs and can be operated as such. Moreover, a simultaneous charging method for both a high-voltage battery and a low-voltage battery is suggested through an additional operational mode that results from the integration. This paper also specifically describes the operating characteristics and the design method in each mode. Design considerations, including possible problems with the integrated circuit structure, are presented, and an additional compensation circuit is suggested to solve these problems. The prototype is built, and experiments are carried out to verify the performance and validity of the proposed power unit.

Analysis of MOSFET Failure Modes in Bi-directional Phase-Shift Full-Bridge Converters

This paper presents an analysis of the mechanism of failure modes in bi-directional phaseshift full-bridge converters, composed of MOSFET, based on the circuit operation and parasitic parameters of MOSFET. In addition, the relation between circuit operation and parameters is suggested through an experimental comparison. From this relation, the suitable ranges of parameters for stable performance are analyzed. The design criteria of the bi-directional phase-shift full-bridge converter are presented and evaluated from the experimental verification.

Sensorless active damping method of LCL-filter in grid-connected parallel inverters for battery energy storage systems

In this paper, a sensorless active damping scheme of LCL-filter is proposed in grid-connected parallel inverters for battery energy storage systems. The proposed damping method is superior to the conventional notch filter and virtual damping methods with respect of robustness on the variation of resonance of the filter and unnecessary additional current sensors. The theoretical analysis of the proposed damping method is explained in detail, along with the characteristic comparison to the conventional active damping methods. Through the performance verification of the proposed sensorless active damping method, it is noted that the performance is comparable to the conventional virtual damping method even without additional current sensors. Finally, informative simulation and experimental results are provided to examine the overall characteristics of the proposed method.

Analysis and Design of LCL Filter with Passive Damping Circuits for Three-phase Grid-connected Inverters

The analysis and design process of the LCL filter with passive damping circuits for threephase grid-connected inverter are presented based on the generalized model of LCL filter. Several types of the passive damping circuits in previous studies could be compared and analyzed by using the generalized model considering various design criteria of passive damping circuits. According to the analysis in this paper, a reasonable configuration of passive damping circuits for three-phase gridconnected inverters is proposed. The validity of the proposed design process is verified by informative simulation and experimental results.

A seamless transfer control method with high load sharing performance for modular ESS

This paper describes a theoretical and experimental study on a seamless transfer control strategy for the parallel operation of three-phase voltage source inverters (VSIs) for energy storage systems (ESSs). Moreover, phase-locked loop, seamless transfer control, and parallel control algorithm are optimized for simplicity in order to implement in a unified-controller. Finally, the proposed algorithm is validated through informative simulation waveforms and experimental results.

Analysis and design of LCL filter with passive damping circuits for three-phase grid-connected inverters

In this paper, a design method of LCL and a generalized model with various types of passive damping circuits for the three-phase grid-connected inverter are proposed. Based on the generalized model, theoretical analysis is carried out to examine the performance of the designed LCL filter. The validity of the proposed filter model is verified by simulation and experimental results.