INTEGRATED IGBT PWM CONVERTER/INVERTER SYSTEM FEEDING THREE-PHASE INDUCTION MOTOR

Abstract

The integrated PWM converter/inverter system has the capability of unity power factor, sinusoidal supply current, bi-directional power capabilities and constant de link voltage. Also, it has the ability to minimize the de link capacitance. The integrated PWM converter/inverter fed three-phase induction motor consists of two identical PWM converters. One is used to serve as power regulator with unity power factor and constant de voltage bus, while the other serve as inverter for the induction motor drive using the indirect vector-controlled technique. By using the synchronous rotating­ frame the current controllers in both the input and the output of the integrated system are characterized by fast current response and low harmonic distortion.

The de link is the intermediate stage between the PWM converter and the PWM inverter. It mainly consists of aluminium electrolytic capacitors, which are normally installed in the system as the energy storage element, but in some applications, such as high power motor drives, the electrolytic capacitor has several drawbacks from the viewpoints of size, weight, cost and reliability. Due to continuous out-gassing, the properties of the electrolytic capacitor deteriorate gradually as time goes by. Hence, the capacitor is the major factor limiting the lifetime of the integrated systems. In this work, the size of the de link capacitor can be reduced, as it means reduction of the cost and the volume of the converter/inverter systems.