Nonlinear Control for Single-Stage Single-Phase Grid-Connected Photovoltaic Systems

A nonlinear control strategy is developed for a single-stage single-phase grid-connected photovoltaic (PV) inverter in synchronous dq frame. The control scheme is proposed to achieve both maximum power point operation, regardless of the atmospheric conditions, and to control the active and reactive power. The control scheme forces the d-axis current to track a novel trajectory reference current, obtained online. The control scheme provides for energy balance from the input to the output of the system along with mitigating the PV current ripple, which is the major drawback of the single-phase PV inverter. A Lyapunov analysis is developed to prove the stability of the system and boundedness of signals. The scheme is validated through a simulation.