Uncertainty analysis of power system time-domain simulation is mainly concerned with the study of the influence of uncertainty factors in power system on time-domain simulation results. It provides an important reference for analyzing the transient stability of power system under uncertain conditions. A method based on generalized polynomial chaos(gPC)is proposed for uncertainty analysis of time-domain simulation. Approximately

the method assumes that there exists a polynomial relationship between variables and random factors at any time. The solution procedure is as follows. Firstly

the optimal orthogonal polynomial basis function is acquired to approximate the random input variables and unknown variables. Then

by Galerkin method

the stochastic equations which describe the system's transient process are transformed into the corresponding deterministic equations. Finally

by solving these equations

the polynomial approximation coefficients of unknown variables are obtained

which can be used to calculate the statistical results and probability distribution of relevant variables at any time. Case study results from a single-machine infinite bus(SMIB)system and IEEE 9-bus system show the effectiveness of our method.