This paper examines the operation of distribution networks that have large
aggregations of thermostatically controlled loads (TCLs) providing secondary
frequency regulation to the bulk power system. Specifically, we assess the
prevalence of distribution network constraint violations, such as over- or
under-voltages and overloading of transformers...
Our goal is to determine the
set of constraints that are at increased risk of being violated when TCLs
provide regulation. We compare network operation in two cases: first with TCLs
operating freely, and second with TCLs controlled to track a regulation signal. Using GridLAB-D, we run power flow simulations of five real distribution
networks. Our results indicate that voltage limits are at increased risk of
violation when TCLs provide regulation because of increased voltage variation. Effects on transformer aging are more nuanced and depend on the method used for
dispatching TCLs. We find that in many distribution networks it may only be
necessary to consider voltage constraints when designing a TCL control strategy
that protects the distribution network.