Design and Analysis of an LCL-based Photovoltaic Power Generation System in Low Voltage Grid Through Virtual Impedance Shaping
Majid Hosseinpour
1
(
Department of Electrical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
)
Rasoul Akbari
2
(
Department of Electrical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
)
Elham Seifi
3
(
Department of Electrical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
)
Mehdi Shahparasti
4
(
School of Technology and Innovations, Electrical Engineering, University of Vaasa, Vaasa, Finland.
)
Keywords: Grid-connected inverter, Photovoltaic array, LCL filter, Virtual impedance,
Abstract :
Grid-connected inverters play a crucial role 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. Yet, in situations with variable network impedance and LCL filter resonance in weak networks, instability can occur. 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 virtual impedance 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.
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