A new class of high-power-density universal power converters

In this paper a new class of universal power converters that offers significantly higher reliability and power density will be introduced. Universal power converters are single-stage power converters that are capable of interfacing any types of electrical loads and any types of electrical sources regardless of their form, number of phases or frequency. They are also capable of simultaneously interfacing several sources and loads. Therefore, they can be configured as dc-dc, dc-ac, ac-dc, ac-ac, or hybrid power converters. The proposed universal power converter is inspired by galvanically isolated Ćuk converter; however, it is controlled and designed such that even for a high power system only a small film capacitor is used for transferring the power from input towards the output. Therefore, no electrolytic capacitors will be needed, and the lifetime of the converter will be longer. Regardless of the number of input or output phases or their forms (dc or ac) a single-phase high frequency transformer can be used for providing galvanic isolation. Given that three-phase low frequency transformers can account for more than 50% of the weight in numerous applications, such as wind power system, this feature of the proposed converter substantially increases the power density. Unlike other types of universal power converters, the proposed universal power converter requires small number of switches. In case of a three-phase ac-ac configuration only 12 switches with anti-parallel diodes are need. This new converter can be either hard-switching or softswitching. In the soft-switching configuration a small inductor is placed in series with the capacitor. In this case, all the switches can benefit from the zero current turn-off and soft turn-on. Thus, naturally commutated switches, such as fast thyristors can also be used. In this paper, the principles of the operation of this converter will be presented and its performance will be evaluated.