Methods and systems for controlling an energy storage system to provide a frequency regulation service

An energy storage system controller configured to perform an operation of controlling an energy storage system to provide a frequency regulation service for a power network, to which the energy storage system is connected, by controlling the energy storage system, according to one or more regulations of the power network, to counteract frequency deviations within a frequency contingency deadband of the power network for a service period, the energy storage system being one of a plurality of energy storage systems connected to the power network, each being operated to counteract the frequency deviations according to the one or more regulations of the power network, the operation comprising:

• determining an estimate of stored energy for each energy storage system at a start of the service period;
• and
• during the service period:
• obtaining a measurement indicative of a frequency level of the power network;
• detecting a frequency deviation requiring counteraction by the plurality of energy storage systems based on the indicated frequency level;
• estimating a remaining amount of stored energy at each energy storage system by applying a model to (i) the estimate of stored energy for each energy storage system at the start of the service period and (ii) the frequency deviation;
• and
• detecting a fault condition if the estimate of the remaining stored energy at each energy storage system is indicative of an inability of the plurality of energy storage systems to counteract a subsequent frequency deviation;
• and
• increasing or reducing an amount of stored energy for the energy storage system in response to detecting the fault condition.