A Flexible Active and Reactive Power Control Strategy of a LV Grid Connected PV System

Abstract

The aim of this paper is to present a command approach of a typical double-stage grid-connected PV system functioning under normal conditions and Symmetrical Grid Voltage Dips (SGVD). In Normal Operation Mode (NOM), the command developed rises the relatively low solar voltage to a suitable level corresponds to the Maximal Power Point Tracking (MPPT) and regulates, respectively, the dc-link voltage and the output inverter currents. It permits to inject energy into the grid at unity power factor and a current with low harmonic distortion. Under SGVD, the control strategy approach should ensure a stable connection as long as possible and inject some reactive power to support the grid faults. This command calculates dynamically active and reactive powers that inverter can deliver according to the level of voltage dips and inverter rating currents. Those values are used as reference to control output inverter currents, the dc-link voltage and to deactivate the MPPT command. To validate and to prove the effectiveness of the control strategy, some experimental results are also presented.