Predictive current control technique for three-phase active power factor correction
Date
1997
Authors
Zhuang, Xiaoyan
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Abstract
Three-phase active power factor correction has become a demanding research topic due to the restricted power quality requirements. The objective of power factor correction is to make the input to a converter behave like a resistive load. However, with a conventional diode or phase controlled rectifier, the line current drawn from the utility contains rich harmonics resulting in poor power factor. It increases the utility transmission power loss, injects harmonics into the power line and causes harmonic distortion of the line voltage in the neighborhood. Poor power factor also reduces the converter efficiency and increases the ratings of the power devices. To overcome these disadvantages, an active power factor corrector can be applied as a front-end power processing unit.
In this thesis, a predictive current control technique is applied to a three-phase boost rectifier with pulse width modulation (PWM) for active power factor correction (PFC). The predictive current control law is derived by analyzing the steady-state operation of the PWM boost rectifier. Six-step PWM technique is integrated with the predictive current control technique because it offers distinct advantages over the conventional PWM techniques. With six-step PWM, the switching losses and conduction losses of the rectifier are reduced and an optimum switching pattern is obtained. A prototype experimental setup including the boost rectifier circuit and DSP based control circuit is built to implement the predictive current control scheme for power factor correction. The design of the prototype is based on the steady-state analysis of the rectifier. The derived predictive current control algorithm is implemented on a DSP TMS320C40 system by a control program. The systematic approach of analysis, design and implementation of output voltage regulation is also presented in this thesis. The steady-state operation and dynamic performance of the converter system are investigated by simulation and experiments. With predictive current control, the input line current follows the shape of the line input voltage within one sampling period resulting in fast dynamic response and nearly unity power factor.