Achieving Specific Compensation of Current Harmonics in Grid Connected PV Power Station Under Limited Reactive Current

Abstract

The new control strategy presented in this paper focuses on improving the capacity of active harmonic filtering in a grid connected PV Power Station (PVPS). The PV field is connected to the grid through a PCS (Power Conditioning System: boost chopper + DC-AC PWM converter). Based on the nominal PVPS power value, reactive power and harmonic currents generated by the nonlinear load can be compensated. The proposed approach is applied to the grid-side converter to realize flexible active power injection and, at the same time, improves power quality at the CP (Connecting Point) by compensating reactive power and ensuring active filtering of the 5^th and 7^th harmonics without reaching the reactive current limit. To guarantee high optimal filtering results of these specific harmonics, a harmonic isolation method based on a High Selectivity Filter (HSF) is employed. This allows the electrical grid to supply only sinusoidal currents under a constant power factor. In this work, to improve the capacity of the PV inverter in terms of harmonics mitigation, it is suggested to suppress instantaneously the high-order harmonics (the 5^th and 7^th harmonics) if possible; otherwise, the specific compensation of current harmonics is canceled. Under normal conditions, the simulations have been carried out and show that the studied PVPS can operate at its optimum energy, and power quality enhancement is achieved through the integration of a specific harmonic filtering algorithm.