T‐type direct AC/AC converter structure

In this study, a novel T‐type topology for single‐phase direct AC/AC conversion is proposed. In this topology, frequency changing takes place directly (without common DC voltage bus) through three converters that are connected in a T structure. Unity input power factor and precise output voltage and frequency regulation is achieved through appropriate control of these three converters. H‐bridge converters can be used in each branch of T to make the proposed converter. The converter is controlled such that the average active power of each H‐bridge remains zero. Therefore, capacitors are implemented in DC links of H‐bridges. Moreover, using half‐bridge converters, instead of H‐bridge ones, for T branch converters, leads to an AC/AC converter with only six semiconductor switches. Also, multilevel inverters, specially cascaded H‐bridge can be used in branches of T. This will lead to a multilevel AC/AC converter that is suitable for high‐power applications such as intertie connections and high‐power motor drives. Principle of operation and control schemes of the converter are then explained. Simulation and experimental results verify the performance of the converter while operating as a power supply at different frequencies.