A novel control scheme for three-level full-bridge converter achieving low THD output voltage

A novel control scheme called symmetrical chop plus phase-shift (SCPS) control, allowing six switches of the three-level full-bridge converter to achieve zero voltage switching (ZVS) and reducing the total harmonic distortion (THD) of the transformer primary side voltage is proposed in this paper. The traditional control schemes for three-level full-bridge converter to achieve ZVS ignored the impact of the high THD of transformer primary side voltage. The high THD will cause large power loss in transformer and is not conducive to delivery energy for transformer. In the SCPS control, the output voltage of full bridge is symmetrical in half of switching period and the THD is reduced. At the same time, two switches have not achieved zero voltage on. This paper presents switching process and conditions of this control scheme. THD of the output voltage is analyzed and compared with CPS control. The performance of the proposed control scheme was verified on a prototype.