Design and stability analysis of a high-performance three-phase inverter for photovoltaic applications

This paper presents the design and analysis of a three-phase photovoltaic inverter based on a Boost-Buck-Discharge microinverter architecture. It converts low DC voltages (24–240 V), typical of PV panels, into high-quality three-phase AC with minimal THD. The topology integrates a boost converter elevating voltage to 240 V, a buck-discharge stage generating rectified sinusoidal waveforms, and a full-bridge inverter producing pure sinusoidal outputs. A step-up transformer ensures standardised voltages of 225 V RMS (single-phase) and 390 V RMS (line-to-line) with galvanic isolation. Sliding mode control is applied to buck-discharge circuits to ensure robust and stable operation, validated via Lyapunov analysis. Results show THD below 3 % for all tested resistive and inductive loads, confirming efficient multilevel conversion and suitability for decentralised renewable energy systems requiring reliable three-phase DC-AC transformation.