Low cost single stage micro-inverter with MPPT for grid connected applications

• Different modulation techniques were analysed and a novel one is proposed.
• A new control topology with two control loops was implemented.
• A macromodel of the inverter is proposed to improve simulation times of the system.
• The proposed control methods were tested on an experimental prototype.

This paper presents a novel control and modulation technique applied to a low cost single stage solar micro-inverter. Multiple modulation strategies are analysed and finally an optimal one is proposed and implemented in order to obtain a low total harmonic distortion factor and a power factor close to unity of the current supplied to the grid. The luminosity step time response of the system is improved using two analog control loops: a hysteresis current mode control loop and a voltage loop on the input solar panel voltage. A MPPT power loop is also implemented in order to harvest maximum energy from the solar panel. The simulation times of the entire system is improved by implementing an average model for the inverter. In this way multiple control strategies and MPPT algorithms can be tested and compared in a shorter time. The experimental results validate the theoretical and simulated ones.