Power System Resilience Improvement Provided by VSC-HVDC Link Flexibility

VSC-HVDC links can play a significant role in improving power system resilience due to their inner ability in properly regulating active and reactive powers in effective way. Because of that the dynamic behavior of the whole system can be improved in a remarkably way also by implementing innovative functions not foreseen in the classic power systems. These are necessary due to the growing tendency in using of production systems from renewable sources, as for example the emulation of inertia for counteracting the dramatic reduction of total system inertia. In this paper, a control strategy is tailored that can guarantee the participation of the HVDC link to the frequency regulation and voltage regulation at the point of connection buses, while ensuring the desirable level of synthetic inertia thanks to the DC capacitance installed at the connection buses. The control strategy is derived without loss of generality with respect to a two-area system with AC-DC link but can be easily extended to more complex systems. The control laws of the different loops, which are decoupled over the time, are designed by the well-known open loop shaping technique. The results of the numerical applications allow confirming the validity of the assumptions performed in the procedure of choosing of the various controller parameters.