Lyapunov Function-Based Control Strategy for Single Phase GFI System Using LLCL Filter With Faster Dynamics

Integrating an LLCL filter within a grid-following inverter (GFI) system poses resonance challenges that can lead to system instability, similar to the classic LCL filter. In a single-phase GFI system employing an LLCL filter, Lyapunov function-based current (LFBC) control is commonly used to address these issues. While LFBC control ensures global stability, it fails to eliminate grid current oscillation, which remains a significant concern. To overcome this challenge, a modified LFBC controller is proposed in this paper, which guarantees global stability and substantially reduces grid current oscillation. The proposed technique incorporates the PR controller to generate inverter current references. The use of the PR controller, combined with the modified LFBC controller, ensures accurate and robust generation of inverter current references, leading to improved system performance and enhanced stability. Additionally, the modified LFBC controller resolves the limitations of the conventional LFBC control method and significantly improves the stability and quality of the grid current. The effectiveness of the proposed technique is compared with the traditional LFBC control method. The results demonstrate that the proposed LFBC controller successfully mitigates grid current oscillation while maintaining global stability. The GFI system shows a fast dynamic response and effectively injects sinusoidal grid current by utilizing the proposed controller, thereby improving the system’s performance.