Fixed frequency predictive MPPT for phase-shift modulated LLC resonant micro-inverter

The variability of the environmental conditions tuned the Maximum Power Point Tracking (MPPT) control to be a fundamental technique for Photovoltaic (PV) systems. The majority of the well-known MPPT techniques are good fitting to conventional (PWM) converters; but they are not suitable for resonant converters applications, as its output gain is frequency dependent. In this paper, a fixed frequency predictive phase shift MPPT technique for the LLC resonant converter. A two-stage Micro-inverter is presented, for grid tied PV applications, employing the LLC resonant converter as the first DC/DC stage, due to it's high power density, high efficiency and the possibility to operate at Zero-Voltage Switching (ZVS) or Zero-Current Switching (ZCS). The second stage is formed from traditional H-bridge Inverter. The proposed control is a fixed frequency predictive phase shift MPPT technique for the LLC converter stage with both fixed and variable steps. To demonstrate the proper operation of the proposed MPPT methodology, a 300 W simulation model for the converter is tested. Hardware prototype is being built in the lab and samples of the experimental results are presented that proves the advantage of the proposed control.