Adaptive Control of Grid-Following Inverter-Based Resources Under Low Network Short Circuit Ratio

Abstract

The stability and dynamic response of inverter-based resources are greatly influenced by uncertain grid parameters. The grid short circuit ratio (SCR) serves as a standard metric for assessing the strength of the network at any location within the electrical power network. A high SCR suggests a strong grid, whereas a low SCR indicates a fragile grid, more prone to disturbances and likely to affect the stability of grid-feeding inverters. Weak grids may lead to extended oscillatory periods in the injected currents at the point of common coupling and compromise the DC link voltage integrity. This research introduces a feedforward adaptive control scheme that operates alongside the current loop proportional-integral controllers, producing a compensating voltage to guarantee the dependable functioning of the voltage-oriented controlled inverters in extremely weak grid scenarios. The adaptive compensator is formulated on the basis of the deadbeat control principle and utilizes the information of the grid impedance to determine the feedforward voltage in real time. Comparative results demonstrate the effectiveness of this method in damping oscillations and shortening the settling time for the DC link voltage, active and reactive power in low SCR grids under transients and faults while minimizing the current total harmonic distortion. The proposed adaptive feedforward control strategy is also experimentally verified on a low voltage test rig under several dynamic conditions including transients, varying operating setpoints, and low voltage ride-through.