Accurate modeling of the measurement system is an important guarantee for the precision of power system dynamic state estimation (DSE). The modified measurement covariance matrix is used to represent the characteristics of the actual measuring system more accurately. In the model based on the modified measurement covariance matrix

the method of power system dynamic state updating used to handle the time-delay measuring problem is proposed. The current dynamic state estimate is used to obtain the state estimate reversedly under the delayed measurement cross section. Through the calculation of covariance and cross-covariance matrix among the estimates

the current state is updated by filtering based on the current measurement. Simulation results on the IEEE 14-bus system show that the dynamic state updating method is of definite effect in increasing the precision of DSE during small load fluctuation

while

the errors of updated state estimate are reduced obviously by using the dynamic state update method based on state-reversed simplified model during large load fluctuation with contribution to the precision of DSE. The simulation results have verified the effectiveness of the proposed algorithm. This work is supported by National Natural Science Foundation of China (No. 51277052

No. 51107032 No. 61104045）.