A Five-Level Boosting Inverter for PV Application

Abstract

Transformerless inverters (TIs) are widely used in grid-connected photovoltaic (PV) applications due to their higher efficiency and low cost. However, the absence of galvanic isolation leads to the flow of ground leakage current due to PV parasitics resulting in safety issues and deteriorated power quality. This article proposes a single-phase five-level TI topology with switched diodes and floating capacitors (FCs). The proposed topology employs a lower number of active power switches and has self-voltage-balancing of FCs, voltage boosting ability, and suppressed leakage current complying with the VDE-4105 standard for safety. A suitable modulation strategy is applied to the proposed TI in order to generate a common-mode voltage with a reduced number of voltage swings and transitions yielding in suppressed leakage current. Simulation and experiment results are presented to prove the operability of the proposed TI. A prototype model rated for 1 kW is developed, and the experimental results so obtained are presented. The leakage currents of magnitudes ≈10 and ≈17 mA are obtained in the simulation and experiments, respectively. A detailed comparison with the other similar topologies is presented to attest to the merits of the proposed TI.