A highly reliable single-stage converter for Electric Vehicle applications

The parallel ac link universal converter is an extension of a buck-boost converter in which the current of the inductor is alternating with zero dc component. Charging an inductor in both positive and negative directions allows better utilizing it. The input and output in parallel ac-link universal converter can have any number of phases with dc or ac voltages, and the switches benefit from the soft switching. The main limitation of the parallel ac-link universal power converter is that it requires large number of switches, i.e. twice the number of switches required for the same converter with dc link, to be able to charge and discharge the inductor in both positive and negative directions. Large number of switches decreases the reliability of the converter and increases its cost. Several modified configurations that require fewer switches than the original configuration and offer the same advantages have been proposed. In this paper, the application of one of these topologies, called “extremely sparse parallel ac-link universal converter”, in Electric Vehicle (EV) is studied. This single-stage converter fulfills the task of the dc-dc converter, inverter, and battery charger in an EV. In contrast to the conventional configuration in which a bulky electrolytic capacitor is used, the proposed approach uses a small inductor and a small ac capacitor at the link that increases the reliability of the system. In this paper, principles of operation, analysis and design procedure of this converter are presented, and its performance in EV application is evaluated.