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Modulation Scheme Analysis for High
Efficiency Three-phase Buck Rectifier
Considering Different Device Combinations
ABSTRACT
The three-phase buck-type rectifier has advantages as front-end converter for high efficiency power supplies in
telecommunication and data centers. In this project, the different commutation types of a three-phase buck rectifier with a
freewheeling diode are analyzed through experiments using different semiconductor devices. Further, the switching loss of the
converter is modeled and calculated for four space vector modulation schemes. It is shown that when the switches include
minority carrier devices, such as Si PiN diode, IGBT and Reverse Blocking IGBT (RB-IGBT), more switching loss will occur in
the commutation between two switches than between a switch and the freewheeling diode. This difference can be reduced if
majority carrier devices, such as SiC Schottky diodes, are used in series with the switches. The modulator can be arranged to
eliminate the specific transition which has the most switching loss. According to the analysis, each modulation scheme has its own
field for high efficiency application. The advantageous modulation scheme is given for different device combinations in this
project.
CIRCUIT DIAGRAM
Existing System
In this project, the commutation in the three-phase buck rectifier with freewheeling diode is investigated in
detail, based on the experiments with different device combinations. Then the switching loss is modeled and calculated,
including both the switching loss under positive and reverse voltage, as well as the loss caused by charging and
discharging of the junction capacitor of non-active devices in the rectifier. The comparison of the four modulation schemes
is given for different device combinations. Through the switching loss analysis in this project, the high-efficiency
modulation scheme can be selected for the three-phase buck rectifier with different device combinations.
Proposed System
When Df is included, the commutation in a buck rectifier is more complex, as it involves another
commutation between switches and this diode. Although the freewheeling diode was included, the subtleties of
the additional commutations were not fully considered in the loss calculations. Besides, the switching loss
varies in different transitions of the modulation scheme. For example, the IGBT may have larger turn-off loss
than turn-on loss due to the tail current. It is efficient to reduce its turn-off times in a modulation scheme.
Actually the performance of the modulation scheme is highly related with the device characteristics and
different transitions should be identified carefully in the analysis. Another part of loss may come from the
charge and discharge of the junction capacitors of the non-active devices which are kept off in the
commutation. It has not been well considered in the previous evaluation of different modulation schemes
TOOLS AND SOFTWARE USED:
 MP LAB
 ORCAD/PSPICE
 MATLAB/SIMULINK
OUTPUT:
 HARDWARE
 SIMULATION