one of the first multistring inverters introduced in practice was the half-bridge inverter with boost converters in the dc-dc stage by SMA. Other to pologies that have followed include the H-bridge, the H5, three-phase two-lev- el voltage-source inverter (21 VSI),the 3L NPC, and the three-phase three-level T-type converter (3L-T). Figure 3 shows some examples of practical multistring configurations. The most common dc-dc stages used for multistring