Electrolytic capacitor-less dual buck inverter with CM and DM active resonance damping control for Non-isolated grid-connected PV applications

Abstract

The shoot-through problem of conventional H-Bridge inverters imposes a threat to system's reliability and efficiency. This is because the unintentional shoot-through state short-circuits the DC-Link capacitor. To overcome the severity of the shoot-through state, Dual Buck Inverters (DBIs) were introduced. These topologies have at least one inductor connected in-parallel with the DC-Link capacitor at accidental shoot-through states' activation; thus, preventing the DC-side from getting short-circuited. Besides, DBIs' circulate inherently low ground leakage current and thereby they are considered as attractive choices in single-phase non-isolated grid-connected Photovoltaic (PV) applications. Therefore, this work proposes a modified non-isolated grid-tied LCL-filter based DBI with a control scheme that improves the reliability and the stability. Specifically, adopting an appropriate Active Power Decoupling Control (APDC) scheme enhances the reliability. This scheme utilizes the Common-Mode (CM) operation of the DBI. As for stability assurance, an Active Resonance Damping Control (ARDC) is developed. This ARDC is deployed in both inverter modes, the CM and the Differential-Mode (DM). Eventually, the theoretical analyses are confirmed on a 3 kW / 30 μΚ electrolytic capacitor-less system. The results showed that the single-phase low frequency ripples of the DC-bus voltage were negligible. Meaning that, the input capacitance requirement of the system is reduced about 40–50 times compared to the conventional methodology. Consequently, utilizing reliable polypropylene film capacitors for effective DC-Linking.