Supercapacitor-Based Inertia Support Control Strategy for Generator Units in Microgrids

Abstract

With the increasing penetration of inverter-based renewable energy sources, low-inertia microgrids are more vulnerable to severe frequency excursions, high rates of change of frequency (RoCoF), and fast electromagnetic transients under sudden disturbances. This study proposes a coordinated supercapacitor-based virtual inertia support strategy in which active power is injected proportionally to RoCoF while voltage and energy constraints are strictly enforced. A microgrid model including three 2 MW synchronous generators, two coordinated 50 F supercapacitor units, photovoltaic generation, and frequency-dependent dynamic loads is established in MATLAB/Simulink. To reduce sensitivity to measurement noise in derivative-based control, a first-order low-pass filter is incorporated into the control loop. The proposed strategy is evaluated under representative scenarios, including a 20% load step, a 2 MW generator trip, and ± 15% band-limited stochastic photovoltaic fluctuations. Compared with the no-supercapacitor baseline, the coordinated multi-supercapacitor strategy reduces the maximum frequency deviation from 0.61 ± 0.02 Hz to 0.32 ± 0.01 Hz and shortens settling time from 14.8 ± 0.5 s to 8.7 ± 0.3 s under the 20% load-step condition. The coordinated control also reduces the peak power burden on each unit and improves state-of-energy balance, indicating improved short-term frequency regulation.