A comparison of policies on the participation of storage in U.S. frequency regulation markets

Because energy storage systems have better ramping characteristics than traditional generators, their participation in frequency regulation should facilitate the balancing of load and generation. However, they cannot sustain their output indefinitely. System operators have therefore implemented new frequency regulation policies to take advantage of the fast ramps that energy storage systems can deliver while alleviating the problems associated with their limited energy capacity. This paper contrasts several U.S. policies that directly affect the participation of energy storage systems in frequency regulation and compares the revenues that the owners of such systems might achieve under each policy.

I. Introduction

Frequency regulation service involves the injection or with-drawal of active power from the power grid to maintain the system frequency [1]. In the United States, frequency regulation is equivalent to secondary frequency control, while primary frequency control is more commonly known as frequency response. The most common mean for a unit to provide frequency regulation is following a system operator's automatic generation control (AGC) signal, which computes the area control error (ACE) from frequency deviations and interchange power imbalances.