Adaptive Droop Control Strategy for Grid-Forming Inverters in Weak Grid Applications

In recent years, it has been seen a shift from conventional source to the renewable source of energy. With this transformation comes its own challenges. This increasing generation from inverter-based resources (IBRs), especially solar photovoltaic (PV) and wind energy, challenges the stability and reliable operation of the utility grid due to their inherent low inertia with conventional phase locked loop (PLL)-based grid following (GFL) control. To enhance the stability of IBRs dominated power systems, the grid-forming (GFM) inverter is introduced which helps to reach n number of renewable integration to the power grids with high stability. This paper presents the grid-forming (GFM) control of three-phase inverter by implementing the Droop control strategy. The objective of this work is to investigate the challenges of the grid following inverter in the transient stability and weak grid condition and the ways grid-forming inverter can effectively solve the problem. In weak grid condition and transient condition, the grid-forming inverter generates voltage, frequency, phase angle by its own without depending on the grid using various control strategies like Droop control, virtual synchronous machine (VSM) control, virtual oscillation (VOC) control, etc., and can deliver power to the grid and the other loads with high stability. The work is based on theoretical analysis of the Droop controlled-based grid-forming inverter and simulation results where the simulation results validate the reliability of the proposed theoretical approach.