Electricity Adjustment by Aggregation Control of Multiple District Heating and Cooling Systems

Introduction of wind energy is proceeding all over the world. However, output fluctuation due to inherent intermittency reduce stability of the power system. Therefore, electricity adjustment (EA) auction was introduced in Japan recently. In this auction, power grid companies make a one-year contract with various power generation companies and procure electric power at the time of supply-demand tightness. One candidate for the auction is a District Heating and Cooling system (DHC) with a Combined Heat and Power (CHP). To investigate the usefulness of using DHCs for the EA, two operations are defined in this paper: normal operation and EA capacity (EAC) provision operation. The EAC provision operation always keeps the EAC of contract so that it can provide EA according to directives from the power grid company. In the previous study, the usefulness of the EA by a single DHC was evaluated. In order to realize more efficient EA, aggregation control of multiple DHCs is proposed. For this control, the EACs by each DHC are combined to ensure the EAC of aggregator's contract. At first, two DHCs are modeled assuming actual DHCs. Using these models, the running costs of the normal operation (Op.1) and the EAC provision operation (Op.2) of each DHC are calculated by the particle swarm optimization (PSO). Furthermore, an additional cost for the EAC provision operation are estimated by calculating the difference between the running costs of the two operations. The assigned EACs to each DHC are determined so that the sum of the additional costs of each DHC is minimized. Finally, by comparing additional costs of the conventional single control to that of the aggregation control, it was found that the total additional cost of the proposed method was reduced. In case of 6,000 kW of the total EAC of contract, reduced cost rate was 54.3%. By using this proposed method, the operator can more efficiently operate DHCs for EA, and further stability of the power system can be expected.