Dual current control scheme for PWM converter under unbalancedinput voltage conditions
Hong-Seok Song; Kwanghee Nam
Industrial Electronics, IEEE Transactions on
Volume 46, Issue 5, Oct 1999 Page(s):953 - 959
Digital Object Identifier 10.1109/41.793344
Summary:Voltage unbalance in a three-phase system causes performance
deterioration of PWM power converters by producing 120 Hz voltage
ripples in the DC link and by increasing the reactive power. To
eliminate the DC link voltage ripple and the DC component of the
reactive power, both positive- and negative-sequence currents should be
controlled simultaneously, according to the paper by Rioual et al
(1996). The authors used two synchronous reference frames: a
positive-sequence current regulated by a proportional integral (PI)
controller in a positive synchronous reference frame (SRF); and a
negative-sequence current regulated by a PI controller in a negative
SRF. In the positive SRF, which rotates counterclockwise, the positive
sequence appears as DC, while the negative sequence appears as 120 Hz.
In contrast, in the negative SRF, which rotates clockwise, the negative
sequence appears as DC, while the positive sequence appears as 120 Hz.
By deleting 120 Hz components using a notch filter in each SRF, one can
measure positive- and negative-sequence currents separately, and use
them for constructing two feedback controllers. Since the
negative-sequence current is also controlled in its own SRF by a DC
command, this approach yields better performance without increasing the
control gain. Note that, since the controller is implemented by a
software routine in the digital signal professor chip, using two SRFs
does not require additional hardware. The authors demonstrated the
effectiveness of the proposed control scheme by using computer
simulation and experiments
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