Near Unity Power Factor Single-Phase to Three-Phase Converter
Feeding an Induction Motor
A. Maamoun*, A. M. Soliman* and A. M. Kheireldin**
* Electronics Research Institute, El-Tahrir Street, Dokki, Cairo, Egypt
Postal Code : 12622, Fax : 202-3351631, E-mail : maamoun@eri.sci.eg
** Faculty of Engineering, Ain Shams University, Cairo, Egypt
Index Terms – Power converters, ac drives, power factor correction, harmonic reduction, pulse width
modulation (PWM).
Summary
The conventional induction motor drive systems employ a rectifier-inverter structure
consisting of a diode or thyristor rectifier, dc bus filter and an inverter. They have
many drawbacks such as, high harmonic distortions and deterioration of power
factor in the main supply.
The paper presents a drive system consists of single-phase boost rectifier, space
vector pulse width modulation (SVPWM) inverter, and three-phase induction motor.
The single-phase boost rectifier is used to obtain near unity power factor and to
reduce the harmonic distortion in the main supply. The SVPWM inverter is used to
offer 15% increase in the output voltage and low output harmonic distortions
compared with the conventional pulse width modulation (PWM) inverter.
The boost converter is supplied from a full-wave rectified line voltage and operated
so that the input current follows the input voltage. The input current shaping results
in low line current harmonic distortion and a power factor close to unity at the
interface between the ac line and the rectifier. The clamped-current boost rectifier is
used as the proposed model for single-phase power factor correction (PFC) rectifier.
Current-mode pulse width modulator is used to control the boost converter. The
output dc voltage of the converter is regulated by voltage regulation loop where an
error amplifier is used as a proportional –integral (PI) regulator. The output of the PI
provides the reference current for the current control loop. The switch of the
converter is turned on at the beginning of a switching cycle, and turned off when the
switch current reaches the reference current, or when the switch duty ratio reaches
the maximum duty ratio (0.5).
The designed boost converter is used as a dc voltage source for SVPWM inverter
feeding three-phase induction motor. The SVPWM enables to feed the motor with a
higher voltage than the conventional PWM. The SVPWM allows to have a higher
torque at high speeds, and a higher efficiency. The voltage/frequency control is used
for open loop speed control of induction motor with a reasonable degree of accuracy.
The input/output performance of the proposed model of single-phase to three-phase
converter feeding an induction motor is investigated with different loading conditions.