Discrete-time integral variable structure control of grid-connected PV inverter

Abstract

In the paper a new discrete-time integral variable structure control of grid-connected PV inverter is proposed in order to   maximize the input power given by PV arrays and at the same time for  using the grid-inverter as a reactive power compensator. In the last   years different variable structure controls (VSC) have been proposed  in literature. In spite these algorithms have been implemented on  digital hardware, they have been developed by means of a timecontinuous formulation neglecting the effects of a   microprocessor-based implementation. Such approach can cause an increasing amplitude chatter of the state trajectories which means instability. The proposed VSC is fully formulated in discrete-time,  taking into account the effects introduced by a microprocessor-based implementation. Moreover it introduces respect to the classical  formalization of the VSC an integral action that improve the  performance of the controlled system. After a detailed formalization  of the proposed control algorithm, several numerical and experimental results on a three-phase grid-connected inverter  prototype are shown, proving the effectiveness of the control strategy. Thanks to the proposed control law the controlled system  exhibits fast dynamic response, strong robustness for modelling error and good current harmonic rejection.