Production enhancement of long string photovoltaic plants during partial shading through switching capacitor power optimizer circuit

Abstract

Long series connections are widely preferred by photovoltaic (PV) power plants because they offer advantages such as higher voltage, independent operation of modules at optimal voltage, ease of installation, and lower losses. However, PV power plants are highly susceptible to partial shading and suffer high power losses, resulting in large financial losses. The existing solutions have numerous weaknesses, such as multiple peaks in the characteristic’s curves, erroneous tracking losses, lower power generation and extraction, and limited applications. To overcome the above limitations, a power optimizer based on a switching capacitor circuit has been proposed in this paper to improve the reliability of long strings in power plants under partial shading scenarios. The power optimizer provides higher power output and a single peak in the characteristics curves by minimizing the voltage differences between modules in the string to enable smoother operation of PV systems under partial shading. To evaluate the application and performance of the proposed power optimizer, two PV system sizes are considered and compared with the conventional techniques under static, moving, and progressive partial shading scenarios. From the in-depth analysis, it is found that the power optimizer minimizes the mismatch between modules by reducing the power losses from 70.83 % in the conventional system to 35.13 %. By implementing the power optimizer in the string, a power extraction of up to 68.68 %, generation efficiency of more than 99 %, and power improvement of 54.21 % are achieved along with single-peak characteristics curves.