Dynamic LQR control for improved DC link voltage stability in grid-integrated solar PV system

Abstract

The integration of photovoltaic (PV) systems into power grids poses a significant challenge to voltage stability, especially at the DC link. Fluctuations in solar irradiance directly cause power variations and instability in this critical interface. If not properly controlled, this variability can lead to inefficiencies, equipment damage, and widespread grid disturbances. To address the abovementioned challenge, this paper proposes a dynamic converter control strategy designed to enhance DC link voltage stability in grid-integrated solar PV system. The core of the proposed control system is based on a Linear Quadratic Regulator (LQR) mechanism, implemented within a two-stage, PV grid connected system with LCL-filtered three three-phase voltage source converter (VSC). Unlike conventional methods such as Sliding Mode Control (SMC), which can suffer from chattering effects, the proposed LQR approach enhances the performance of grid connected solar PV systems. The proposed scheme allows the designed LQR technique to dynamically and optimally adjust its control parameters in response to fluctuating PV power generation, thereby maintaining optimal voltage stability. Simulation results demonstrate that the LQR control system effectively mitigates DC-link voltage fluctuations. Furthermore, compared to the conventional SMC method, the proposed LQR approach significantly enhances the overall system's robustness and reliability