  Economic dispatch and frequency regulation are typically viewed as
fundamentally different problems in power systems and, hence, are typically
studied separately. In this paper, we frame and study a joint problem that co-
optimizes both slow timescale economic dispatch resources and fast timescale
frequency regulation resources. We show how the joint problem can be decomposed
without loss of optimality into slow and fast timescale sub-problems that have
appealing interpretations as the economic dispatch and frequency regulation
problems respectively. We solve the fast timescale sub-problem using a
distributed frequency control algorithm that preserves the stability of the
network during transients. We solve the slow timescale sub-problem using an
efficient market mechanism that coordinates with the fast timescale
sub-problem. We investigate the performance of the decomposition on the IEEE
24-bus reliability test system.
