Impact of delays on a consensus-based primary frequency control scheme for AC systems connected by a multi-terminal HVDC grid

This paper addresses the problem of sharing primary frequency control reserves among non-synchronous AC systems connected by a multi-terminal HVDC grid. We focus on a control scheme that modifies the power injections from the different areas into the DC grid based on remote measurements of the other areas´ frequencies. This scheme is proposed and applied to a simplified system in a previous work by the authors. The current paper investigates the effects of delays on the control scheme´s effectiveness. The study shows that there generally exists a maximum acceptable delay, beyond which the areas´ frequency deviations fail to converge to an equilibrium point. This constraint should be taken into account when commissioning such a control scheme.