Cost effective capacitor voltage balancing control for five-level grid-tied inverters

The neutral point (NP) potential self-balancing of five-level full bridge inverters with conventional modulation strategy is related to the modulation index. Both the voltages of two split-capacitors should be sampled and controlled, when the inverter operates with the low modulation index. Therefore, an improved modulation strategy is proposed to realize the NP potential self-balancing for five-level full bridge inverters within the whole modulation index range. Only the sum of input split-capacitors voltage needs to be sampled, and the hardware cost is reduced. Experimental results verify the effectiveness of the improved modulation strategy.