Primary frequency regulation for a multi-terminal HVDC network via periodically sampling control

In this paper, the problem of primary frequency regulation is investigated for large networks, including various AC areas interconnected by a multi-terminal high-voltage direct current (HVDC) grid. Two control schemes are proposed to guarantee frequency consensus and adapted to the discrete situation in power grid control. The first sampling algorithm modifies the power injections from each AC area into the DC grid as a function of sampling frequency deviations of neighbouring AC areas to share reserves among areas. The second intermittent sampling control has the capability of decreasing the working frequency of the sensors and controllers as an extension of the sampling scheme. For both schemes, corresponding sufficient and necessary conditions for stabilizing the HVDC system asymptotically are further reported. Finally the numerical examples are given to illustrate the theoretical analysis.