Abstract:
In order to reduce the Total Harmonic Distortion (THD) in a three phase boost rectifier,
active switching and passive filters are incorporated in this work. A constant frequency
switching is used for active filtering and pulse width modulation is used to regulate the
output voltage. An input Electro Magnetic Interference (EM!) filter is used to suppress
the high frequency component generated by the active switching. Moreover, a series LC
filter resonating with the supply frequency is also used to suppress the low frequency
component that may pass to the input. With addition of this series LC filter, the THD
value could be made less than three percentages, which is a great improvement over the
earlier rectifiers that have only EMI filter. In the earlier types of rectifiers, the THD value
was as high as 17%.
The efficiency of the module is also studied. As the output voltage has nonlinear relation
with duty cycle, the efficiency is also nonlinear with output voltage variation. But up to
certain range of duty cycle it could be made linear in nature with output voltage.
The input LC series filter and the EMI filter design are discussed. The efficiency versus
output voltage, THD versus duty cycle curve for the proposed rectifier circuit is given for
clear understanding of the model.
ORCAD 9.1 release Version, very powerful Electrical and Electronics design software is
used to design the rectifier circuits. A lot of efforts had to be done to get the ultimate
results by simulation.
