Dual-ground transformerless nine-level dynamic voltage boosting inverter topology

This article presents a new nine-level common ground (CG) type transformerless inverter (TL) structure with an integrated boost (IB) cell. The proposed structure eliminates the leakage current due to the CG structure between the input source and the grid neutral. The proposed topology is derived by combining a DC-DC boost converter and switched capacitor (SC) cell, capable of generating the nine-level output voltage over a wide range of input voltage variations. By maintaining the duty cycle of the IB converter switch at 50%, the proposed topology generates the output voltage with a boosting factor of 4. Besides, soft charging of the involved SCs and reduced inrush current is also achieved through the inductor, which ensures the permissible current stresses of the power switches. Furthermore, the voltage across the SCs is self-balanced, eliminating the need for complex independent control techniques. A 725-W laboratory prototype is built to test the performance of the proposed topology under various operating conditions, such as input and load variations. The measured efficiency of 96.9% at 725 W is obtained and is comparable with the simulation efficiency. Finally, the merits of the proposed topology are highlighted using a detailed comparison with the other recent nine-level inverter topologies.