Improved MPPT Control for Single-phase Grid-Connected PV System

Abstract

In single-phase PV grid-connected systems, the dc-link voltage is characterised by a ripple whose frequency is double the grid-frequency. The voltage ripples always prevent MPPT controllers from capturing the maximum available PV power and it also affects the efficiency of the whole system. This paper introduces the analysis and design of an improved MPPT control strategy for single-phase two-stage PV grid-connected system (PVGCS). The improved MPPT control strategy is used to eliminate the side effects of the voltage ripple on the extracted PV maximum power. This paper shows how the double grid-frequency voltage ripples affect the extracted PV power and the MPPT controller performance. This analysis indicates by equations that the extracted power from the PV has an average value which is less than the maximum value of the available PV power and finds the relation between this value and the double grid frequency voltage ripples. The paper also proposes a modified MPPT strategy to overcome this phenomenon. The modified strategy is tested with two known MPPT controllers, the incremental conductance and the ripple correlation controller. Superior performance regarding MPPT performance and ripple voltage mitigation is validated in both cases through Simulink simulations.