Autonomous Load Control for Frequency Regulation in Low-Inertia Systems: An Experimental Demonstration

The increasing use of inverter-based resources in modern power systems has significantly reduced synchronous inertia, making frequency regulation more challenging. Further, fast and autonomous responses are required to relieve rapid frequency variations following disturbances, and controllable loads have emerged as a promising alternative to support system stability. However, evaluating such control in real power systems is difficult because large-scale testing in a real power system is costly and operationally restrictive owing to its negative effect. To overcome this limitation, this study constructs a laboratory-scale isolated power system with adjustable mechanical inertia, designed to emulate varying levels of renewable energy penetration, and experimentally investigates autonomous load control (ALC) activated according to frequency deviation and the rate of change of frequency (RoCoF). A short control cycle is adopted to detect frequency changes promptly, enabling fast power consumption changes under controllable loads. The experimental results show that frequency-deviation-based ALC improves the frequency nadir by up to 51%, while the combined frequency-deviation- and RoCoF-based control achieves an improvement of up to 73% and reduces the RoCoF by up to 60% under low-inertia conditions. These results confirm that demand-side fast load control can complement traditional supply-side measures and enhance the stability of future low inertia power systems. These findings offer practical insights into the design of ALC for grids with declining system inertia.