Bilateral Inertia and Damping Emulation Control Scheme of VSC-HVDC Transmission Systems for Asynchronous Grid Interconnections

This paper proposes a novel bilateral inertia and damping emulation (BIDE) control scheme for VSC-HVDC transmission systems that can autonomously provide inertial and damping responses to two VSC-HVDC interconnected asynchronous AC grids in a similar fashion of synchronous generators. For each VSC station, the energy for inertia emulation comes from augmented DC link capacitance whereas the energy for damping emulation comes from the interconnected grid on the other side. This proposed approach is communication-free as the essential information of two grid frequencies for inertia and damping emulation can be obtained from the locally measured variables dictated by the BIDE control algorithms. Modal analysis is carried out to investigate the impacts of BIDE-emulated inertia time constants and damping factors on system small-signal stability, and to obtain the optimal control parameters. The effectiveness of the proposed BIDE scheme is verified through controller hardware-in-the-loop experiments, in the presence of load changes and grid faults. The results show that the BIDE scheme can effectively enhance the stability and damp the frequency oscillations for both AC grids.