Cascaded H-bridge inverters with separated DC sources charging the DC-link are widely used in the industry application due to its inherent advantages. However, a failure of the DC sources can interrupt the power supply which results in economic loss. This paper proposes a soft-switching modulation algorithm to tackle this issue. A pre-set table lists all of the possible redundant module states that can adjust the voltage of the DC-link. With this method, the DC voltages can be always balanced even under DC source failures, resulting in good flexibility, good dynamic performance and no voltage level-skip. Hence, a reliable and continuous power supply is guaranteed. Finally, 3-module experimental results verify the validity of the proposed method and simulation tests are used to verify its balance limitations.

具有分离的直流电源给直流母线充电的级联H桥逆变器由于其固有的优势而在工业应用中得到了广泛的应用。但是，直流电源故障会中断电源，从而导致经济损失。本文提出了一种软开关调制算法来解决这个问题。预设表列出了可以调整直流母线电压的所有可能的冗余模块状态。使用这种方法，即使在直流电源故障的情况下，直流电压也可以始终保持平衡，从而具有良好的灵活性，良好的动态性能和无电压电平跳变的情况。因此，保证了可靠且连续的电源。最后，通过3个模块的实验结果验证了该方法的有效性，并通过仿真测试验证了该方法的平衡局限性。