Grid Integration of Single-Phase Inverters Using a Robust PLL-Less Control Strategy for Renewable Energy Applications

In this paper, a PLL-less control technique for single-phase grid-connected voltage source converter (VSC) system is proposed that overcomes shortcomings in traditional PLL-based and existing PLL-less techniques. The proposed method avoids the use of a PLL and thus significantly decreases the computational complexity of the system as well as enhance system response dynamics for weak grid conditions connected to renewable energy sources. Using the proposed current control technique, the method ensures precise power injection and synchronisation with the grid voltage. Unlike conventional methods that require multiple controllers and complex transformations, the proposed method uses a single proportional-integral (PI) controller for implementation simplicity, along with better dynamic performance. The main contribution of this study is to use an alpha beta-dq transformation for reference generation without PLL dependency, enabling robust synchronisation and high-quality power injection. Performance evaluation results demonstrate the method's satisfactory response time, low total harmonic distortion (THD) and compliance with IEEE power quality standards under varying load and grid conditions. The case and comparative analysis highlight the proposed control method's ability to maintain stability and efficiency, outperforming traditional PLL-based and other PLL-less techniques. The study highlights the potential of the PLL-less approach for applications in renewable energy systems and provides a simplified, reliable and cost-effective alternative for grid integration. This controller design contributes to the advancement of grid-tied inverter technology, leading to more efficient use in renewable energy applications for the future.