Se-Kyo Chung

A phase tracking system for three phase utility interface inverters

The analysis and design of the phase-locked loop (PLL) system is presented for the phase tracking system of the three phase utility interface inverters. The dynamic behavior of the closed loop PLL system is investigated in both continuous and discrete-time domains, and the optimization method is considered for the second order PLL system. In particular, the performance of the three phase PLL system is analyzed in the distorted utility conditions such as the phase unbalancing, harmonics, and offset caused by the nonlinear load conditions and measurement errors. The tracking errors under these distorted utility conditions are also derived. The phase tracking system is implemented in a digital manner using a digital signal processor (DSP) to verify the analytic results. The design considerations for the phase tracking system are deduced from the analytic and experimental results.

Digital control of phase-shifted full bridge PWM converter

This paper presents the modeling and design of the digital controller for a phase-shifted full-bridge converter (PSFBC) in the discrete-time domain. The discretized PSFBC model is first derived and then analyzed considering the sampling effect and the system parameters. Based on this model, the digital controller was directly designed in discrete-time domain. The simulation and experimental results are provided to verify the proposed modeling and controller design.

High-voltage power supply for semi-active suspension system with ER-fluid damper

Electrorheological (ER) fluid is a composite material sometimes applied to mechanical motion devices such as the semi-active suspension, high-speed clutch, and vibration isolator. ER fluid application needs a high-voltage power supply (HVPS) having special requirements such as sufficiently high and continuously controllable output voltage, fast dynamic performance, over-current-limiting capability, low cost, and compact size. This paper deals with the HVPS for the semi-active suspension using the ER-fluid damper. The electrical characteristics of the ER-fluid damper are analyzed and the design and implementation of the HVPS are presented. It is well demonstrated through experiments that the developed HVPS shows a satisfactory performance suitable for ER-fluid application.

Active clamped three-phase isolated boost converter with series output connection for high step-up applications

A new active clamped three-phase isolated boost converter is presented for the high step-up DC-DC converter applications such as fuel cells, photovoltaic and battery sourced power conversion systems. The proposed converter employs the parallel three-phase input and series output structure to handle the high input current and high output voltage. This structure is suitable for generating the high output voltage using relatively low PWM duty and transformer turns ratios, which provides the high efficiency and low device stress. Moreover, the zero voltage switching (ZVS) is also achieved using an active clamping circuit. The operational principle and key waveforms of the proposed converter are presented. The considerations for the design and implementation are also discussed. The experimental results for a prototype converter with a 600W power rating, 24V/380V input/output voltages are provided to show the validity of the proposed converter scheme.

Implementation of fuel cell dynamic simulator

This paper presents a development of fuel cell dynamic simulator using a programmable DC power supply and LabVIEW graphical user interface. The developed simulator closely describes the static and dynamic characteristics of an actual fuel cell. The developed simulator can be used as a convenient and economic alternative of an actual fuel cell for developing and testing the fuel cell power conditioning system.

EMI reduction technique of flyback converter based on capacitance model of transformer with wire shield

A common mode EMI reduction technique of a flyback converter using a wire shield is presented. The capacitance model of the flyback transformer is derived and it is used to determine the values of the wire shield turns and compensation capacitor minimizing the noise voltage. The experimental results for an actual adaptor are provided to verify the effectiveness of the proposed method.

Analysis of LLC Resonant Converter with Current- Doubler Rectification Circuit

In this paper, LLC series resonant converter with current-doubler as a rectification circuit for secondary side is proposed. The current-doubler circuit is generally used for the high voltage input and low voltage output application to get high efficiency characteristics with reduced transformer turn ratio. However, an inductive circuit is not used in a secondary side for the LLC series resonant converter generally. When there is inductive circuit like current-double on the secondary side, the resonant characteristics are changed. In this paper, LLC converter with the current-doubler using coupled inductor is proposed. We verify that the secondary side current-doubler using coupled inductor is not affect to the resonant characteristic of primary LLC by the mathematical analysis. Finally, the analysis results are proved by the simulation and experiments.

Active clamped three-phase isolated boost converter with voltage doubler output for high voltage conversion ratio

A new active clamped three-phase isolated boost converter is proposed for low voltage distributed energy resources. The proposed converter has a parallel input and voltage doubler output structure to obtain the high output voltage from the low voltage source. The three-phase parallel input structure with an interleaved operation provides a high power rating and reduced input current ripple. The high voltage conversion ratio can be easily obtained using the voltage doubler output stage. Moreover, the zero voltage switching (ZVS) is also achieved using an active clamping circuit. The converter operation and prototype design are presented. The experimental results are finally provided to show the validity of the proposed converter scheme.

Multi-envelope 3-dimensional constellations for polarization shift keying modulation

In this paper, multi-envelope 3-dimensional (3-D) constellations for polarization shift keying modulation (POLSK) are introduced. Signal points of the constellations are on the surfaces of two concentric spheres. In the receiver, two kinds of demodulation schemes are exploited. One is the conventional coherent detection (CD) of the Stokes parameters. The other is based on the maximum-likelihood (ML) algorithm. As a result of simulation, the 16-ary cube-in-cube (CIC) constellation with the ML receiver shows the best error performance in the additive white Gaussian noise (AWGN) environment.

Design of power conversion system for Stirling engine Micro-CHP integrated into DC power distribution network

This paper describes a design of the power conversion system for the DC distribution network with the String engine micro-CHP source. The design of the PWM AC-DC and high step-up DC-DC power converters is presented for the Stirling engine with a permanent magnet synchronous generator (PMSG). The maximum power control for a low voltage PMSG and PWM AC-DC converter is discussed and the high efficiency design of the high step-up isolated DC-DC converter is considered. The prototype converter with 1kW power rating and 400VDC output is implemented and the experimental results are provided to verify its operation and performance.