An Enhanced Control Strategy for Harmonic Current Suppression of Grid-Connected PV System without Phase-Locked Loop Under Distorted Grid Voltage Conditions

This paper proposes an enhanced proportional resonant (EPR) current controller for a grid-connected photovoltaic system (GCPVS) without phase-locked loop (PLL). The EPR current controller suppresses the grid current harmonics in the presence of distorted grid voltages. The overall control strategy of the proposed system is implemented in the α-β reference frame without PLL and the park’s transformation. Consequently, the computational requirement of the GCPVS is reduced. Further, the dynamic performance of the system is enhanced under the grid frequency deviation. Moreover, a modified incremental conductance maximum power point tracking (MINC MPPT) algorithm is implemented, which is characterized by faster tracking ability under rapidly changing environmental conditions and maintaining low power oscillations in the steady-state. The effectiveness of the proposed PLL-less EPR control strategy is validated through a real-time digital simulator OPAL-RT under distorted grid voltage conditions and compares it with the conventional PR PLL based control strategy.