A novel on-line identification for Thevenin equivalent parameters of power system regarding persistent disturbance condition

This paper presents a novel on-line parameter identification method of Thevenin equivalent circuit that is applicable to the situation when the persistent disturbances occur at the system side. Based on the theoretical derivation that the voltage and current variation at a node are taken as the superposition of the variations respectively caused by the system side and the load side, a new mathematical model that takes into account the variable at the system side is built. Independence of variables at the system side and the load side is used to solve the model. Compared with the existing methods, the proposed method doesn't assume that the equivalent source voltage is constant, so it is more applicable to the situation when persistent disturbances occur at the system side. Simulation and filed tests show that the proposed approach performs better than the least square method when the persistent disturbances occur at the system side. With the persistent disturbances becoming larger, the least square method doesn't work gradually, while the proposed approach can identify the parameters of the Thevenin equivalent circuit as well.