Yu-Seok Jeong

An Isolated DC/DC Converter Using High-Frequency Unregulated

This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss. The prototype converter with a 1-kW design (Vin = 24 ~ 48 V/Vo = 400 V) shows an efficiency of above 90.2% under a 24-V input and full load conditions.

LLC

This paper presents an algorithm to calculate the current references on line, considering the inherent nonlinear nature of the saturation effect in an interior permanent-magnet synchronous machine for the minimum-copper-loss control under the current and voltage limit of the drive system. This paper basically approaches this issue as a nonlinearly constrained optimization problem where the torque command imposes the nonlinear equality constraint and the voltage limit imposes the nonlinear inequality constraint. Depending on the operating region, it solves the corresponding set of nonlinear equations in real time derived from the Lagrange multiplier method. Newtons method among various techniques is adopted to implement the numerical solution. This scheme gives accurate results not only in motoring but also in generating operation of the machine, since the voltage drop of the stator resistance is taken into account, which is hardly applicable to a two-dimensional lookup table where the inputs are the torque command and the maximum flux amplitude, and the output is each axis current reference in the rotor reference frame. The simulation and experimental results show the feasibility and performance of the proposed technique

Resonant Converter for Fuel Cell Applications

Novel analysis and design methodology using the newly adopted synthetic flux linkage for interior permanent-magnet (PM) synchronous motors (IPMSMs) with a multilayered PM have been proposed. In addition, cross magnetization between the d and q axes in the IPMSM is taken into account via the proposed synthetic flux linkage, which can be identified numerically and experimentally. It is validated with the experimental ones for the purposely built prototype, and its further effectiveness on control application is introduced.

Online Minimum-Copper-Loss Control of an Interior Permanent-Magnet Synchronous Machine for Automotive Applications

This paper presents the design and implementation procedures of a control scheme for a high-performance induction motor drive for the traction purpose of full-scale electric vehicles to be series produced. For automotive use, the control scheme is designed with the expectation of possible advances in energy efficiency by adopting maximum-torque-per-ampere control and in robustness by employing extensive compensations for variations in magnetic flux, temperature, and voltage. The control scheme is then validated in the course of the bench test, followed by the in-vehicle test.

Novel Analysis and Design Methodology of Interior Permanent-Magnet Synchronous Motor Using Newly Adopted Synthetic Flux Linkage

This letter suggests a two-stage isolated/bidirectional dc/dc converter with three bridges. Two bridges are used for electrical isolation and constant gain, and the bidirectional control is accomplished through only a single bridge. RMS currents in the high-voltage source and link capacitor can be alleviated by capacitor division and synchronizing operation of both stages. This structure provides a simple control scheme and removes snubber circuitry, so a high efficiency can be obtained under a high switching frequency regardless of operational modes.

Energy-Efficient and Robust Control for High-Performance Induction Motor Drive With an Application in Electric Vehicles

This paper describes operational analysis results of the DC micro-grid using detailed model of distributed generation. Detailed model of wind power generation, photo-voltaic generation, fuel cells generation was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The operation analysis was carried out using PSCAD/EMTDC software, in which the power circuit is implemented by built-in model and the controller is modeled by user-defined model that is also coded with C-language. Various simulation results confirm that the DC micro-grid can operate without any problem in both the grid-tied mode and the islanded mode. The operational analysis result confirms that the DC micro-grid make it feasible to provide power to the load stably. And it can be utilized to develop an actual system design and building.

A Two-Stage Isolated/Bidirectional DC/DC Converter With Current Ripple Reduction Technique

In this paper 3.3 kW on-board charger is proposed for electric vehicles or plug-in hybrid electric vehicles. Considering the life time of charger, new topology which is not using the high-voltage electrolytic capacitors is proposed. This charger is comprised of two stages that one is boost converter stage for PFC control and the other is uncontrolled LLC resonant converter for galvanic isolation and step-down of voltage. Proposed charger is implemented and it is 7.1 liters in volume and 6.8kg in weight. The experimental result indicates 92.5% of the efficiency at input voltage 220Vac and 88.3% at input voltage 110Vac under 3.3kW of output power. And the output voltage ranges is from 150V to 450V.

DC Micro-Grid Operational Analysis with a Detailed Simulation Model for Distributed Generation

This paper presents a simulation model and a parameter identification scheme of an induction motor drive for electric vehicle. The induction motor in automotive applications should operate in very high efficiency and achieve the maximum-torque-per-ampere (MTPA) feature even with saturated magnetic flux under very high torque. The indirect vector control which is typically adopted in traction drive system requires precise information of motor parameters, particularly rotor time constants. This work models an induction motor considering magnetic saturation and proposes an empirical identification method using the current controller in the synchronous reference frame. The proposed method is applied to a 22kW-rated induction motor for electric vehicle.

3.3kW on board charger for electric vehicle

This paper proposes a grid-tied power conditioning system for the fuel cell, which consists of an LLC resonant DC-DC converter and a 3-phase inverter. The LLC resonant converter boosts the fuel cell voltage of 26–48V up to 400V, using the hard-switching boost converter and the high-frequency unregulated LLC resonant converter. The operation of proposed power conditioning system was verified through simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental works with a laboratory prototype, which was built with 1.2kW PEM fuel-cell stack, 1kW high gain step-up converter, and 2kW PWM inverter. The proposed system can be utilized to commercialize a real interconnection system for the fuel-cell power generation.

Parameter Identification of an Induction Motor Drive with Magnetic Saturation for Electric Vehicle

The interest is coming to be high, recently with depletion of the fossil fuel and with carbon dioxide exhaust limit about emittion, from a car of Internal combustion engine to Electric vehicle. AC-DC converter is necessary to battery charging which is an electric vehicle energy storage. Necessary conditions of the converter are necessary for wide output voltage range, high efficiency, high power factor etc. It is composed two stages for wide output voltage range and insulation. Preliminary stage uses LLC resonant converter and the after stage uses BOOST converter PFC circuit for being considered a power factor and confirmed experimentally.