Bidirectional Power Converter for Solar Grid Interface Applications: An Experimental Investigation

Abstract

Switching control of a current controlled grid integrated inverter using three-level neutral point clamped (NPC) inverter is investigated in this paper. The proposed scheme uses both the hysteresis current control (HCC) and carrier based switching schemes to improve the low switching frequency operation. To overcome the problems associated with current control techniques a simple carrier injection method is proposed in this paper. This current control method uses a high frequency triangular carrier injected to the current tracking error. The triangular carriers are chosen with minute amplitude comparable with current tracking error. This will enhance the switching frequency and stabilize the NPC inverter. This will ensure constant switching frequency operation of the grid interface inverter (GII). A comprehensive modeling of GII is carried out to study the stability of the system. A comparative study of switching frequency stabilization is presented. To verify the proposed current controller a prototype setup is developed. Analytical studies with experimental results of the proposed techniques are presented to show the superiority of results.