Robust Volt-VAr Control Using Model Predictive Control for Grid-Connected Three-Phase Inverters

In modern power systems, the intermittent nature of distributed energy resources (DERs) and the fluctuating load demands can lead to significant voltage fluctuations in the distribution network, greatly impacting the grid's stability and reliability. Thus, energy storage systems (ESSs) are normally integrated into the grid, using three-phase voltage source inverters (VSIs), to provide the required power and compensate for voltage fluctuations. Traditionally, linear control strategies, such as proportional-integral (PI) control, are adopted to control three-phase VSIs and provide the required reactive power to ensure the secure operation of the grid. However, these control methods suffer from a slow-dynamic response, which may cause reliability challenges to the power grid's stability. Hence, this paper proposes a Volt/VAr control strategy-based model predictive control (MPC), which can be implemented on grid-connected three-phase VSIs. The presented control technique is developed to mitigate the voltage fluctuations at the distribution network resulting from the fast changes in the load. Simulation results, using MATLAB/Simulink™, are carried out to validate the effectiveness of the proposed control method under varying load conditions.