Modelling of Thermostatically Controlled Loads to Analyse the Potential of Delivering FFR DSR with a Large Network of Compressor Packs

This paper presents preliminary work from a current study on large refrigeration pack network. In particular, the simulation model of a typical refrigeration system with a single pack of 6 compressor units operating as fixed volume displacement machines is presented, and the potential of delivering static FFR with a large population of such packs is studied. Tuning of the model is performed using experimental data collected at the Refrigeration Research Centre in Riseholme, Lincoln. The purpose of modelling is to monitor the essential dynamics of what resembles a typical supermarket convenience-type store and to measure the capacity of a massive refrigeration network to hold off a considerable amount of load in response to FFR DSR event. This study focuses on investigation of the aggregated response of 150 packs (approx. 1 MW capacity) with refrigeration cases on hysteresis and modulation control. The presented model captures interconnected dynamics (refrigerant flow in the system linked to temperature control and the system's refrigerant demand and to compressors' power consumption). Type of refrigerant used for simulation is R407F. Refrigerant properties such as specific enthalpy, pressure and temperature at different state points are computed on each time step of simulation with REFPROP.