High-Flexibility DC-Link Voltage Control for Grid-Tied Solar PV Systems: Maximizing Performance and Power Quality

This paper presents a novel high-degree-of-freedom (DOF) DC-link voltage control loop for a three-phase voltage source inverter (VSI) in a grid-tied solar photovoltaic (PV) system. Unlike conventional approaches that suffer from double-grid-frequency ripple, slow transient response, and complex PI controller design, this work brings forward three key innovations. First, a novel control strategy is proposed that allows straightforward PI gain calculation by incorporating an additional integral term, simplifying the design process. Second, applying a gravitational search algorithm (GSA) for optimal DC-link voltage regulation offers a distinct advantage in achieving efficient system operation. Third, the integral time square error (ITSE) metric is integrated into the heuristic optimization process, ensuring accuracy and precision. These innovations collectively result in substantial improvements in dynamic performance and power quality, specifically in reducing steady-state oscillations and settling time. Additionally, a second-order, second-order generalized integrator quadrature signal generator (SOGI-QSG) is employed to extract the active component from three-phase load currents, which is then used with the proposed outer DC-link voltage control gain to estimate reference grid currents. As a result, the overall VSI control reduces steady-state oscillations and enhances dynamic performance, leading to fewer oscillations and reduced settling time. Simultaneously, the robust control ensures the multifunctional operation of the VSI, including harmonic elimination, power factor enhancement, and grid synchronization. Furthermore, a detailed analysis of the computational load associated with the GSA-based control strategy is provided, including metrics such as processing time, memory usage, and computational efficiency, ensuring the method’s practicality for real-time applications. The comparative analysis between state-of-the-art and proposed control strategies highlights the superior responses of the latter. Furthermore, the performance of the proposed method is validated using a laboratory prototype based on a dSPACE-1104 microcontroller, and the results conform to the IEEE-519-2014 standard.