Combined Load Frequency Control and active distribution network management with Thermostatically Controlled Loads

In this paper, we propose a novel hierarchical control algorithm to enable simultaneous participation of aggregations of Thermostatically Controlled Loads (TCLs) in power system Load Frequency Control (LFC) and active distribution network management in order to increase the integration of Renewable Energy Sources (RES). The algorithm assumes a two-way communication infrastructure and consists of two phases: day-ahead scheduling and real-time operation. In the scheduling phase, the optimal load dispatch is determined by considering demand and RES predictions and solving a robust multi-period AC Optimal Power Flow (AC-OPF). In real-time, a two-step procedure is applied to control the load aggregation to desired set-points that guarantee LFC provision, maximize the absorption of RES power and satisfy Distribution Network (DN) constraints. The effectiveness of the algorithm is illustrated by considering a benchmark Medium Voltage (MV) DN with large shares of photovoltaic (PV) generation and a controllable aggregation of residential Electric Water Heaters (EWHs). The results show that the algorithm properly exploits the demand-side flexibility and guarantees the provision of significant LFC reserves. At the same time, it reduces the curtailed PV energy due to DN stresses and minimizes adverse effects on user comfort.