An Integrated Semi-Double Stage-Based Multilevel Inverter With Voltage Boosting Scheme for Photovoltaic Systems

This article proposes a single-phase, seven-level, transformerless inverter, employing a semi-double stage-based conversion technique, which is particularly suitable for photovoltaic (PV) applications. The proposed configuration achieves voltage boosting using a non-isolated interleaved buck-boost converter, which is fused with the inverter configuration through two switched capacitors (SCs). The interleaved front-end boost stage is capable of achieving a voltage gain of three while resulting in reduced peak current stress on the switching devices. In this topology, a part of the load power is transferred directly from the PV source, while the other part is transferred through the SCs. The proposed topology and the associated pulsewidth modulation (PWM) technique are capable of reducing the leakage current by isolating the terminals of the PV source in the freewheeling state. This article also presents a thorough analysis of the stray capacitor voltage and the common-mode voltage (CMV). These analyses reveal that the high-switching frequency transitions are eliminated in both of these waveforms. Furthermore, the proposed topology results in the reduction of low-frequency transitions in the stray capacitor voltage and the CMV, which in turn result in further reduction of the leakage current. The simulation and experimental results are in agreement with the mathematical analysis of the proposed inverter.