High-Gain Seven-Level Switched-Capacitor Two-Stage Multi-Level Inverter

Due to the low voltage of the PV module and to enable AC module technology, where every PV module has its own DC-AC converter, this paper introduces a new high step-up seven-level two-stage multilevel inverter for a grid-connected Photovoltaic (PV) system. The introduced schematic consists of two stages. The first stage is a switched capacitor boost converter and the second stage is a seven-level seven-switches multilevel inverter. The first stage is designed to extract the maximum power of PV module and step-up its input voltage. The proposed seven-level seven-switches topology generates seven levels with only seven switches. Thus, the number of switches is reduced. The proposed inverter has eight valid switching states. In each switching state only three switches are ON at the same time. The proposed topology has some distinct features such as reduced number of switches and reduced conduction; total harmonic distortion (THD) of the current is 23% in case of pure resistive and with no filtration at the output and less than 3% using a small filter with integration into the grid. Due to the high boosting ability of the switched capacitor boost converter, a wide voltage gain is easily achievable. In this paper the system is tested at different voltage gains and the highest simulated efficiency was around 96%. The developed system is simulated in MATLAB/SIMULINK and in real time using DSPACE1202. Both simulation and real-time results are consistent with the theoretical analysis.

Automated summary

This paper proposes a new high step-up seven-level two-stage multilevel inverter for a grid-connected Photovoltaic (PV) system. It consists of a switched capacitor boost converter and a seven-level seven-switches multilevel inverter. The converter is designed to extract maximum power from PV module and boost its input voltage, and the inverter has a reduced number of switches and reduced conduction. The system achieves a wide voltage gain and has a low current total harmonic distortion (THD). The simulated efficiency of the system reaches 96%.