Integral adaptive controller design for single-phase-grid-connected solar PV systems with output LCL filters

In this work, a nonlinear integral adaptive backstepping scheme (ABS) for single-phase grid-connected (SPGC) solar photovoltaic (SPV) systems with output LCL filters is proposed to enhance the quality of injected power. The proposed controller is designed to suppress the total harmonic distortion (THD) from the injected grid-current while minimizing the tracking error of the injected grid-current. However, external disturbances could deteriorate the performance of the THD and tracking error of the injected grid-current. Hence, to achieve the robust performance of the proposed control scheme, external disturbances are also incorporated within dynamical model which can be estimated by employing adaptation laws. In addition, the global stability of the system is analyzed by formulating the Lyapunov function (LF) during the design step of the controller. Lastly, the effectiveness of the proposed control scheme is assessed on a 3.5 kW SPGC SPV system under changing operating conditions. The controller performance is also compared with an existing controller in terms of THDs of the injected grid-current.