Object Oriented Modeling of Thermostatically Controlled Devices for Cold Load Pick-up

Problem statement: During service restoration, the power level at buses can significantly differ from the one presented under steady-state conditions, demanding an amount of electric power significantly higher than the normal load. Hence, their post-outage behavior must be adequately forecasted in order to permit the development of reliable restoration plans, or to avoid inadequate actions that may lead to a subsequent shutdown of the electric power system. This problem is known in the literature as cold load pick-up and the thermostatically controlled loads can be pointed as the main responsible for this behavior. Approach: This study proposes a methodology to model the thermostatically controlled load behavior during the reenergization process, based on object oriented programming and the physical modeling of individual loads, avoiding the explicitly modeling of the electric distribution feeder. In this context, the load aggregation is also implemented using “feeder” classes in an hierarchical structure. Results: The methodology was tested considering distinct devices distributed along a hypothetical feeder and the results show the impacts of interruption duration and environmental temperature in the load behavior. Conclusion: The Cold-load phenomena can be successfully simulated based on physical parameters of thermostatically controlled loads using objectoriented programming, yielding satisfactory results. In special, the impacts of the environmental temperature in the load to be restored can be assessed in detail.