Generic security-constrained inertia emulation scheme for VSI-based DC system using supercapacitor

The large-scale grid integration of renewable energy source via a voltage source inverter (VSI)-based DC system results in a continuous reduction in system kinetic inertia, deteriorating grid frequency stability. To mitigate this problem, this paper proposes a generic security-constrained inertia emulation (SIE) scheme, which integrates an appropriately-sized supercapacitor (SC) bank with a VSI-based DC system via a bidirectional DC/DC converter. Inertial response provision is enabled by an SIE control loop developed for the DC/DC converter controller to adjust the SC voltage along with the grid frequency. It is further underpinned by adding an inertia adjustment algorithm to cope with potential security risks of VSI overcurrent and DC system overvoltage. The SIE scheme features a plug-and-play advantage without modifying the original system. The SIE controller parameter optimization is also carried out through the small-signal stability analysis. The effectiveness of the SIE scheme is evaluated using a modified IEEE 39-bus test system in the presence of generator outage and grid fault.