Seamless Control for a PV System during Transitions between Grid Connection and Standalone Operation

Abstract

This paper introduces a simple and accurate seamless transfer control strategy for PV Distributed Generator (DG). This seamless transfer guarantees the stable operation of the critical loads fed by the DG during transition from grid connection to the standalone mode or vice versa. This strategy is based on classical PI controller which operates in two modes of operation. The first mode is the standalone mode where the PI controller acts as a voltage regulator. The second mode is the grid connected mode where the PI operates as a current controller. The PV operates in two modes of operation as well. The first mode is the MPPT mode during which a Perturb and Observe (PO) technique is responsible for maximum power extraction from the PV arrays. This mode is active during grid connection. The second mode is active during standalone operation where a PI controller is responsible for stabilizing the DC-link voltage by manipulating the boost converters duty ratio. The simulation results show the effectiveness of the proposed control strategy.