High-Frequency Impedance Analysis of Grid-Connected PV Inverter Topologies

The increasing integration of renewable energy sources, particularly photovoltaic (PV) systems, has introduced significant challenges in grid stability and power quality, especially in the high-frequency range. Accurate impedance modeling and measurement are helpful for understanding the dynamic behavior of grid-connected PV inverters. This paper presents a novel methodology for high-frequency impedance analysis of parallel-connected PV inverter topologies, addressing limitations of conventional low-frequency impedance models. Experimental measurements of impedance were performed for various topologies using a grid simulator and PV inverters, and data was transformed load impedance form for enhanced analysis. The effects of high-frequency propagation were incorporated into the impedance model using the propagation constant and characteristic impedance of low-voltage cables. The methodology was validated by comparing measured and modeled results for combined topologies, demonstrating that the inclusion of high-frequency effects significantly improves impedance modeling accuracy. This work highlights the necessity of accounting for signal propagation and its results such as phase shift in high frequencies in grid-connected inverter systems, paving the way for more reliable and efficient integration of renewable energy. The results show that this modification can reduce model error and even about 3 to 4 times more accurate for frequencies higher than 10kHz.