Supercapacitor Internal Resistance Mitigation for Rapid Inertia Emulation of Renewable Power Generation

Inertia emulation control (INEC) using supercapacitors (SC) has become an appealing approach to effectively enhance the frequency stability of modern low-inertia power grids. However, considerable internal resistance (IR) existing in commercially available SCs may adversely degrade the speed and accuracy of SC-based inertial response, which has been neglected by existing INEC schemes. To tackle this issue, this paper proposes an SC IR mitigation (SCIRM) for rapid INEC, consisting of an online IR identification module to obtain up-to-date IR value through fictitious frequency ramp injection and an IR mitigation control to compensate for the voltage deviation across the identified IR. The small-signal stability of the SCIRM-based rapid INEC scheme is strengthened through control parameter optimization. The effectiveness of the scheme in correcting SC inertial response as well as promoting power system frequency stability is evaluated through experimental verifications using a 10 kW testbed and simulation studies using a modified IEEE 39-bus New England system.