High-efficiency Modulation Scheme for Three-Level Buck Four-Leg Current-Source Inverter

Four-leg current source inverter (4L-CSI) has abilities of zero-sequence current handling, voltage boosting, and output short-circuit protection, but it also has the drawbacks of bulkiness and low efficiency. To address these drawbacks, a three-level buck 4L-CSI (3L-Buck-4L-CSI) topology and a simple and high-efficiency modulation scheme are proposed. Due to the multilevel characteristics of 3L-Buck-4L-CSI, the volume of its DC inductor can be reduced greatly and the DC-link current could respond quickly. The proposed modulation scheme is an algebraic modulation scheme, in which the duty cycles are obtained by solving algebraic equations simply and directly. In addition, it reduces the DC-link current and the average switching frequency compared with conventional modulation schemes, which improves the efficiency of the converter. The experimental results validate the effectiveness of the proposed topology and modulation scheme.