A neutral point voltage ripple inhibition topology for three-phase four-wire inverter

The mid-wire current of three-phase split DC link inverter flow into split capacitors under unbalanced load, causing the neutral point voltage ripple. The ripple will influence three-phase output voltages' amplitude and phase. Moreover, with the growth of mid-wire current, in order to guarantee the symmetric three-phase voltage, the split-capacitor capacity has to be increased to decrease voltage ripple, but the increasing capacitor capacity will lead to a great addition of cost and volume. To solve the unbalanced voltage of split-capacitor problem caused by capacitors' divergence and the increasing of load imbalance, a high frequency converter was applied to the preceding stage of three-phase split DC link inverter to balance the voltage of split-capacitor, and a neutral point voltage ripple inhibition topology for three-phase four-wire inverter was proposed and its working models were analyzed. As the simulation and experiment results show, this topology improves inverter's ability for restraining three-phase unbalanced load and reduces the capacity and volume of split-capacitor efficiently.