A Reduced Power Switches Count Multilevel Converter-Based Photovoltaic System with Integrated Energy Storage

A multilevel topology for photovoltaic (PV) systems with integrated energy storage (ES) is presented in this paper. Both PV and ES power cells are connected in series to form a DC-link, which is then connected to an H-bridge to convert the DC voltage to an AC one. The main advantage of the proposed converter compared to the cascaded-H-bridge (CHB) converter, as well as compared to the available multilevel topologies, is that fewer semiconductor devices are needed here. As the output voltage levels increase, more switches are saved, which results in a more efficient, cheaper, and smaller converter. So far, there is still no modulation strategy that is designed particularly for PV-fed multilevel converters with built-in ES. The standard modulations are unpractical for such an application since they suffer from deficiencies such as polluted output signals—thus, requiring larger output-filter—and over-modulation. A modified modulation strategy for PV+ES multilevel inverters is, therefore, introduced in this work. The proposal has been simulated and experimentally validated to evaluate its effectiveness, where it has been shown that the proposed topology is not exclusively feasible, but also suffers from less conduction and switching loss, achieving higher efficiency with respect to its counterpart the CHB.