Design and Implementation of Solar Grid-Connected Inverter With the Approach of Maximum Power Injection and THD Reduction in Partial Shading Conditions Using Cascaded Repetitive Controller

In this article, an approach is presented to ensure that a rooftop solar power plant performs efficiently in the face of partial shading. A two-stage, five-level H-Bridge hardware structure has been implemented to achieve lower switching losses compared to conventional two-level inverters. This design reduces heat generation and enhances the efficiency of the power injected into the grid. To track the sinusoidal input signal effectively, a novel Repetitive Controller has been employed, minimizing error and thereby decreasing Total Harmonic Distortion (THD). The controller’s performance results in an error that approaches zero, leading to a significant reduction in THD and an increase in the power injected into the grid. Notably, this novel controller outperforms traditional Repetitive Controllers as well as conventional Proportional-Integral (PI) and Proportional-Resonant (PR) controllers, especially during changes in grid frequency or under conditions of partial shading on the input panels. Using this controller, the amplitude of 3^ {rd}, 5^ {th}, and 7^ {th} harmonics is minimized. In normal conditions, there is no phase shift between the output current of the inverter and the grid voltage at frequencies of 50. 5 Hz, 50 Hz, or 49. 5 Hz. The Total Harmonic Distortion current (THD ₈) is measured at 1. 18% under normal conditions and 3. 01% during partial shading—both values significantly lower than those achieved with other methods. This structure, along with a suitable maximum power tracking control on the side of the input converter, has resulted in significant performance improvements.