Bipolar power flow in a dc/ac converter with only one high-frequency switch pair

The present investigation is concerned with dc/ac power conditioning interfaces that employ active waveshaping techniques. It is shown that these interfaces can be accomplished with only one high-frequency transistor/diode switch pair, even if power must flow in both directions. It is noted that the necessary alteration in topology can be achieved through the bridge switches because the direction of power flow governs whether the bridge transistors or the bridge diodes are the operating devices. The bridge transistors must place the ac system in a different location in the topology than do the bridge diodes and the dc system must have the characteristics of a voltage source. The solution for the dc-current-source case requires more bridge switches. It is concluded that the costs inherent in this technique make it necessary to weigh the relative tradeoffs.