A Single DC Source Five-Level Switched Capacitor Inverter for Grid-Integrated Solar Photovoltaic System: Modeling and Performance Investigation

Abstract

Boost converters and multilevel inverters (MLI) are frequently included in low-voltage solar photovoltaic (PV) systems for grid integration. However, the use of an inductor-based boost converter makes the system bulky and increases control complexity. Therefore, the switched-capacitor-based MLI emerges as an efficient DC/AC voltage convertor with boosting capability. To make classical topologies more efficient and cost-effective for sustainable power generation, newer topologies and control techniques are continually evolving. This paper proposes a reduced-component-count five-level inverter design for generating stable AC voltages for sustainable grid-integrated solar photovoltaic applications. The proposed topology uses seven switching devices of lower total standing voltage (TSV), three diodes, and two DC-link capacitors to generate five-level outputs. By charging and discharging cycles, the DC capacitor voltages are automatically balanced. Thus, no additional sensors or control circuitry is required. It has inherent voltage-boosting capability without any input boost converter. A low-frequency-based half-height (HH) modulation technique is employed in the standalone system for better voltage quality. Extensive simulations are performed in a MATLAB/Simulink environment to estimate the performance of the proposed topology, and 17.58% THDs are obtained in the phase voltages. Using a small inductor in series or an inductive load, the current THD reduces to 8.23%. Better dynamic performance is also observed with different loading conditions. A miniature five-level single-phase laboratory prototype is developed to verify the accuracy of the simulation results and the viability of the proposed topology.