A Robust Photovoltaic Power Conditioning System Connected to Weak Grid Through Virtual Impedance Shaping

Abstract

Grid-connected inverters are crucial in transmitting power from distributed production systems and renewable sources to the grid. However, these inverters often generate current harmonics due to high-frequency switching and DC link ripple. To address these issues, various filters, including the LCL filter, are employed. This paper focuses on improving the power quality of grid-connected photovoltaic arrays using LCL filters, primarily through a current sensor and virtual impedance shaping. The paper divides the output impedance of the photovoltaic array power optimization system into an active and passive part. It neutralizes the active component by introducing a series of virtual impedances and counteracts its adverse effects with parallel virtual impedance. The design process for both series and parallel virtual impedance is elaborated, and the system's sensitivity is thoroughly analyzed. To validate the proposed approach, extensive simulations have been carried out using MATLAB software. The simulations demonstrate the robust and precise performance of the control system in effectively injecting the maximum power generated by the photovoltaic array into the grid. Additionally, they showcase the high-quality current being injected into the grid and the system's capacity to maintain stability, even in a weak network environment.