On Balance Control Strategy with a Wide Range of Modulation Indexes for Multilevel DC-link Inverter

To solve the problem that the output power and switch burthen of each DC-DC converter cell in the multilevel DC-link (MLDCL) inverter are imbalance, a new power balance control strategy is proposed in this paper. By adjusting the control angles of each cell in 1/2 output cycle of phase voltage to overcome the adverse effects of the control angles in conventional staircase modulation, it can balance the output power of each cell with a wide range of modulation indexes. 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 with different modulation indexes, and the simulation results show that it can also improve the waveform performance of phase voltage.