Adaptive Frequency Estimation Technique for Grid Connected Photovoltaic System

Abstract

This paper deals with the adaptive estimation of frequency observation (AEFO) based technique for compensating the harmonics component of two-stage grid-connected solar photovoltaic (PV) system. The maximum PV power is extracted using maximum power point tracking (MPPT) algorithm. Moreover, the input DC voltage of the voltage source converter (VSC) is maintained at desired level using a proportional integral (PI) controller. The AEFO control injects the required reactive component, which shapes the balanced grid currents. Moreover, the active power is injected in to the grid, which eliminates the harmonics in the grid currents. Using this controller, the fundamental reference currents are estimated using nonlinear load currents. This system maintains the grid current total harmonic distortion (THD) in accordance to the IEEE 519 standard. The dynamic response is improved by adding the PV feed-forward term with the estimated magnitude of i eα and i eβ current quantities. This control improves the dynamic response when insolation is changed and also provided a good response when switched from PV array to DSTATCOM and vice versa. Moreover, the power quality issues such as load unbalancing, power factor correction and reduced the grid side currents harmonics. Test results has shown the reactive power compensation of balanced and unbalanced nonlinear loads and the steady-state and dynamic performances of the system and PV array to DSTATCOM and vice-versa.