| Abstract |
This paper presents a midpoint voltage balancer (MVB) which provides neutral point voltage stabilization to three-phase four-wire converters. The MVB consists of dual switching legs, two neutral inductors, and two split capacitors. A sensorless approach with open-loop control is adopted. It removes current/voltage sensors and alleviates computational demand. It is a cost effective and robust alternative to the closed-loop MVB. Due to the zero-crossing of the neutral inductor current, all switches of the MVB operates in zero-voltage switching mode when neutral current is smaller than the nominal phase current of the three-phase four-wire converter. Interleaving operation of the MVB minimizes the high-frequency current circulation in the split capacitors. In addition, the two neutral inductors are magnetically coupled to decrease the inductor current ripple. As a result, the size of passive components of the MVB is reduced. The proposed sensorless approach is verified by a 20 kVA prototype. |
