Robust feedback-linearisation control of a boost converter feeding a grid-tied inverter for PV applications

In this study, the feedback-linearisation (FBL) technique is employed to design a dc-dc boost voltage regulator feeding a grid-tied inverter for photovoltaic (PV) systems. The key feature of the proposed approach is that only a voltage control loop is used to generate the driving signal for the converter and no current control loop is required. Thereby, unlike the cascaded structure, the bandwidth of the voltage control loop can be specified only by the switching frequency as there is no need for an intermediate inner-loop. The major concern of this control scheme is its limited ability to eliminate completely the steady-state error under model uncertainty and unknown disturbance such as the PV current, which is considered as an unmatched disturbance. For this purpose, the unknown perturbation is estimated by a disturbance observer and compensated in the control law to drive the steady-state error to zero. With a fast disturbance estimation, the composite controller is able to retain the nominal transient performance specified with the FBL. The effectiveness of the proposed approach was verified by both simulation and experimental results, and a remarkable agreement was obtained while exhibiting excellent performances.