On Novel Structure of Multilevel DC-link Inverter

To reduce the number of power devices, diodes and simplify the driving circuitry, a novel Multilevel DC-link (MLDCL) inverter is proposed in this paper. The new topology consists of N DC-DC converter cells and a single-phase full-bridge converter, of which each DC-DC converter needs only one power device to implement power conversion. The new topology produces a significant reduction in the number of power devices and diodes required in the multilevel DC-link. To solve the problem that the output power and switch burthen of each DC-DC converter cell in the MLDCL inverter are imbalance, a new strategy is presented. By adjusting the control angles of staircase modulation strategy in each cell during half of phase voltage cycle, it can balance the output power of each cell. Meanwhile the switch numbers and switch burthen of each power devices in the cells also achieve balance. Further more, the new strategy is simulated and confirmed, and the simulation results also show that it can improve the waveform performance of phase voltage.