A Black-Box External Equivalent Method Using Tie-Line Power Mutation

A new black-box equivalent method by using tie-line power mutation is proposed in this paper, which is especially suitable for a two-port or three-port interconnected grid that does not know any information of the external network. The proposed method, based on the simplified Ward equivalent model of the external network, aims to addresses the following issues: unstable parameter estimation of the existing black-box-based static equivalence method and low accuracy or difficult implementation. Correspondingly, the main features of the proposed method, which makes it as a solution for these existing issues above, are summarized as follows: 1) it is easy to implement, as it only involves the associated measurements of boundary nodes in two adjacent time instants that are before and after a designed large disturbance of the internal grid; 2) it is robust to measurement errors, thus guaranteeing more accurate equivalent modeling; and 3) it can be applied to both the two-port and three-port equivalent networks. The simulation results of the New England 39-node test case and the actual electric grid case in Guangdong of China validate the effectiveness and performance of the proposed method.