Minimum DC-Link Voltage Control for Efficiency and Reliability Improvement in PV Inverters

This article proposes the minimum dc-link voltage control for efficiency and reliability improvement of two-stage grid-connected photovoltaic (PV) inverters. The main goal is to compute in real-time the minimum dc-link voltage required for power transfer to reduce the stresses on capacitors and semiconductor devices. Analytical expressions of current and voltage stresses in the converter components are derived to support the viability of the technique. The feasibility of this control strategy is demonstrated by experimental results. The efficiency and system-level reliability are computed based on a case study of a 3-kW commercial PV inverter. The results indicate that the proposed solution leads to suitable dynamic response, reduced power losses, and increased system-level reliability. Since no additional hardware is required to implement the proposal, this approach can improve the reliability of current PV inverter technology through simple modifications in the firmware of installed systems.