  Recent advances in data sensing and processing technologies enable
data-driven control of high-voltage direct-current (HVDC) systems for improving
the operational stability of interfacing power grids. This paper proposes an
optimal data-driven control strategy for an HVDC system with line-commutated
converters (LCCs), wherein the dc-link voltage and current are optimally
regulated at distinct HVDC terminals to improve frequency regulation (FR) in
both rectifier- and inverter-side grids. Each HVDC converter is integrated with
feedback loops for regulation of grid frequency and dc-link voltage in a
localized manner. For optimal FR in both-side grids, a data-driven model of the
HVDC-linked grids is then developed to design a data-driven linear quadratic
Gaussian (LQG) regulator, which is incorporated with the converter feedback
loops. Case studies on two different LCC HVDC systems are performed using the
data-driven models, which are validated via comparisons with physics-based
models and comprehensive MATLAB/SIMULINK models. The results of the case
studies confirm that the optimal data-driven control strategy successfully
exploits the fast dynamics of HVDC converters; moreover, cooperation of the
HVDC system and synchronous generators in both-side grids is achieved,
improving real-time FR under various HVDC system specifications, LQG
parameters, and inertia emulation and droop control conditions.
