High Performance Three-phase PWM Converter with Reduced DC-Link Capacitor under Unbalanced AC Voltage Conditions

Abstract

A high performance three-phase pulse width modulation (PWM) converter with reduced DC-link capacitor under unbalanced AC voltage conditions is proposed in this paper. The unique feature of the converter lies in that sinusoidal symmetrical AC currents and ripple free DC voltage can be achieved simultaneously without using a bulky capacitor, which was thought to be a dilemma in the past. The control scheme is implemented in α-β frame, so the complex rotate transformations are avoided, and it does not require the extraction of positive and negative sequence currents, which simplifies the control algorithm. A two-quadrant operation active power compensator together with its controller is developed to suppress the voltage ripple in the DC-link. Compared with the passive compensation method, the compensator is equipped with a smaller capacitor to reduce the system size, weight and cost. Moreover, the compensator could be integrated with the conventional three-phase three-leg PWM converter seamlessly.

Existing System

Genetic Algorithm.

Proposed System

This paper proposes a novel solution for three-phase PWM converters operating under unbalanced AC voltage conditions. Sinusoidal symmetrical AC currents and ripple free DC voltage can be achieving simultaneously without using a bulky electrolytic capacitor. The inherent reason for instantaneous power oscillation of the converter is analyzed through a mathematical model in α-β frame. Based on the model, a simple control scheme in α-β frame is used for sinusoidal symmetrical AC currents without the complex rotate transformation and the extraction of positive and negative sequence currents. An active power compensator with simple configuration circuit is integrated to the DC-link of the conventional three-phase three-leg PWM converter to remove the DC voltage ripple. The capacitor used in the compensator is compared with the passive compensation method comprehensively. Comparing results show that the compensator is equipped with a smaller capacitor. Therefore, the proposed scheme could further reduce the system size, weight and cost.

Architecture

Structure of the proposed three-phase PWM converter