Design Methodology for a Medium Voltage Single Stage LLC Resonant Solar PV Inverter

Abstract

An inverter is generally employed with MV LFT to connect to the grid in a grid-tied PV system. However, in some single-stage topologies, the LFTs are replaced by HFT combined with an unfolder inverter. Generally, these topologies have limited use at high-power MV grids due to high switching losses on the primary side. This study proposes an LLC resonant converter-based single-stage inverter design procedure. Resonant converters make use of ZVS to reduce switching losses. The design includes both the resonant tank as well as output filter components. The design is verified by simulations in MATLAB/Simulink for various loads and input voltages at 13.8kV grid output voltage. THD simulations validate the filter design.