3kW-class three-phase interleaved insulated Bi-directional DC-DC converter analysis and design

Analysis and Design of Three-Phase Isolated Bi-directional
    Interleaved DC-DC Converter

Taesub Kang

Department of Electrical Engineering,Graduate School
Chungnam National University Daejeon,Korea
(Supervised by Professor Hanju Cha)
This thesis presents an implementation of three-phase DC-DC
converter which converses the low  input voltage level to a high
voltage level and is used in fuel-cell and battery applications.
For the purpose of highly efficient voltage conversion,two topologies
has been analyzed and implemented a basis of three-phase DC-DC converter.
Firstly,the PWM  and operating principles has been explained for
three-phase current-type active clamp DC-DC converter,where all
switches are operated in ZVS operation because ofthe active clamp
circuit and leakage inductor of converter.Also,by using  -back
method astable pre-charging can bee stablished even in case of the
load variation.By connecting two PI controllers in series,the output
voltage and the input current values has been maintained during the
load variation. In this thesis,a 800W  three-phase current-fed active
clamp DC-DC converter propotype,which connects a fuel-cell with
an grid-connected inverter,has been implemented and verified in a
real three-phase grid-connected application.
Secondly,an interleaved method has been applied in to the existing
converter for implementing a three-phase interleaved bi-directional
DC-DC  converter The  three-phase  full-bridge  rectifier of the
interleaved DC-DC  boost converter has been modified by using
IGBT's reverse-directional diode,hence the analysis and design of
bi-directionalconverter,which operates in two modes:boost mode
and buck mode operation,has been carried out.The PWM operation
and  interleaved DC-DC converter has been explained.
All switches  of  three-phase  interleaved  bi-directional DC-DC
converter are worked in ZVS operation.As a result,the effect of
reducing converter's input current's ripple and ZVS operation of all
switches at1kW power is about 95%.1kW and 3kW converters were
directly designed and the converter's prototype such as PCB,input
and leakage inductor,transformer design process have been described.
Finally, the  3kW   three-phase  interleaved  bi-directional DC-DC
converter has been verified in stable operation.In conclusion,this
converter has been verified to be suitable for high-power conversion
equipment in batterycharger/dis-charger,UPS and hybrid car.
FULL THESIS
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