Limit preserving equivalent method of interconnected power systems based on transfer capability consistency

A limit preserving equivalent method of interconnected power systems is proposed. Based on the equivalent network keeping the consistency of power flows and sensitivities, the equivalent active power constraints are derived under the condition of retaining the consistency of transfer capabilities before and after equivalence. The transfer capabilities are obtained by an optimisation model in which various limits of original external network are included. Based on the limit preserving equivalent network, an equivalent optimal power flow (EOPF) model for interconnected power systems is presented, which can effectively maintain both sensitivity and limit information of the external network. The accuracy and effectiveness of the proposed equivalent method and EOPF model are demonstrated using the IEEE 39-bus system and an actual 661-bus system.