Selective load control to provide primary frequency response in the wake of introducing new large thermal power plants to Sri Lanka

Abstract

A simple low cost smart socket is proposed to switch off fridges, fans and air-conditioners thus providing primary frequency response. When the power system frequency is dropping, the smart sockets switch off the appliances plugged into the sockets. As these appliances are switched off at higher frequencies than existing loading shedding frequency, the frequency drop after a loss of generation can be reduced. When the frequency drop is reduced, it minimises the risk of cascade tripping of thermal generators that are usually operated at tight frequency limits and the risk of damaging transformers and induction motors in transmission system and in electrical appliances. The effect of the load control is simulated using a model tuned to Sri Lankan system. The model was modified to replicate an actual frequency event occurred in Sri Lanka. The reduced frequency drop minimises the operation of existing load shedding scheme which deny power to all consumers. The appliances switched off in this method are non-critical and hence, unlike existing load shedding schemes. this scheme does not cause economic loss due to loss of production of industry.