INTEGRAL BACKSTEPPING CONTROLLER DESIGN OF PHOTOVOLTAIC SYSTEM CONNECTED TO THE GRID

Abstract

In this paper, the problem of maximum power point tracking (MPPT) in photovoltaic (PV) system comprising a PV panel, a PWM DC / AC inverter connected to the single-phase network is addressed. Unlike conventional systems, the great benefits of the proposed system are reduced cost as it involves no temperature/irradiation sensors and no chopper, and higher reliability. We seek to achievement three control objectives: (i) extracting the maximum power from the photovoltaic generator, (ii) regulating the DC voltage to a desired value (Vpv,ref) (iii) supply a current with sinusoidal form and in phase with the grid voltage. The control strategy is based on the design of a nonlinear controller Integral Backstepping robust to be applied to the DC-AC inverter in order to optimize the PV energy extraction and to achieve unity power factor (UPF). In order to improve the robustness of the nonlinear control, an integral action is introduced. The stability of the nonlinear control is demonstrated by means of Lyapunov analysis. Representative Computer simulations show the performance of the control strategy to track the maximum power point of the photovoltaic panel and network synchronization grid current with the mains voltage in different climatic conditions.