New MPPT technique using phase-shift modulation for LLC resonant micro-inverter

Under varying environmental conditions, Maximum Power Point Tracking (MPPT) is an essential technique for photovoltaic (PV) systems. Most of MPPT techniques including the widely used one, Perturb and Observe (P&O) are proposed for conventional Pulse Width Modulated (PWM) converters. However, they are not suitable for resonant converters. Resonant converter is a type of high efficiency converters with the capability to operate at very high switching frequency which leads to reduces its footprint. In this paper, two-stage micro-inverter is presented based on the advantage of high efficiency resonant converter. A design of LLC resonant converter as pre-stage DC/DC with MPPT is discussed. For this purpose, phase-shift MPPT technique is proposed. To show the effectiveness of the proposed phase-shift MPPT for the LLC converter, a 300-W PSIM simulation model is designed and its results are presented.