Loss-Minimizing Generation Unit and Tie-Line Scheduling for Asynchronous Interconnection

Asynchronous interconnection of two power systems by high voltage direct current transmissions (HVDCs) is a judicious choice to enhance the reliability of system operation and evade some risks. As one of the pioneers of asynchronous interconnection, the southern China power system encounters the challenge of coordinating generation of the sending-end and demand of the receiving-end. The day-ahead generation unit and tie-line scheduling problem is formulated as a two-stage mathematical optimization, in which the first-stage problem minimizes the variance of the remaining load series of receiving-end and generates a near-optimal interarea power transmission schedule, whereas the second-stage problem decides the production level of generation units and power flow of HVDC tie-lines with the objective of minimizing transmission losses. In the second-stage problem, discrete characteristics of HVDC power profile is explicitly modeled, and a quadratic loss function derived from historical data is used to calculate the overall loss of each HVDC, which is then piecewise linearized to form a tractable mixed integer linear programming. Numeric experiments based on realistic data of China Southern Power Grid are carried out. The feasibility and effectiveness of the proposed method is verified through comparing the optimized generation and transmission schedules with original ones which are generated based on expert knowledge.