Experimental Power-Hardware-in-the-Loop Investigation of Battery Frequency Response in Low-Inertia Power Systems

Frequency stability is becoming increasingly important in modern power systems due to high penetration levels of inverter-interfaced renewable energy sources (RES) and the resulting reduction in system inertia. To address this issue, battery energy storage systems have been proposed as fast-acting resources for frequency-related system support services. Respectively, this paper presents an experimental Power Hardware-in-the-Loop (PHIL) investigation of a Redox Flow battery’s frequency response in a low-inertia grid environment. A control scheme in which the battery state of charge is used as the primary control variable has been implemented. Virtual inertia and damping terms have been added to the battery control loop, so that the response to frequency deviations can be adjusted as required. The PHIL setup, comprising a real-time digital simulator, power amplifiers, a test grid platform, and a commercial Redox Flow battery, has been used to validate the proposed approach under a range of disturbance scenarios. The presented results show that although longer than usually expected response times are obtained, the emulation of inertia and damping in the BESS leads to reducing of the frequency nadir and shortening of the settling time. These results demonstrate that battery-based virtual inertia can effectively enhance frequency stability in low-inertia power systems, highlighting its potential role in future grids with high numbers of inverter-interfaced RESs.