  In this paper, we analyze the impact of communication failures on the
performance of optimal distributed frequency control. We consider a
consensus-based control scheme, and show that it does not converge to the
optimal solution when the communication network is disconnected. We propose a
new control scheme that uses the dynamics of power grid to replicate the
information not received from the communication network, and prove that it
achieves the optimal solution under any single communication link failure. In
addition, we show that this control improves cost under multiple communication
link failures. Next, we analyze the impact of discrete-time communication on
the performance of distributed frequency control. In particular, we will show
that the convergence time increases as the time interval between two messages
increases. We propose a new algorithm that uses the dynamics of the power grid,
and show through simulation that it improves the convergence time of the
control scheme significantly.
