  This paper proposes a novel non-iterative method to solve power system
differential algebraic equations (DAEs) using the differential transformation,
a mathematical tool that can obtain power series coefficients by transformation
rules instead of calculating high order derivatives and has proved to be
effective in solving state variables of nonlinear differential equations in our
previous study. This paper further solves non-state variables, e.g. current
injections and bus voltages, directly with a realistic DAE model of power
grids. These non-state variables, nonlinearly coupled in network equations, are
conventionally solved by numerical methods with time-consuming iterations, but
their differential transformations are proved to satisfy formally linear
equations in this paper. Thus, a non-iterative algorithm is designed to
analytically solve all variables of a power system DAE model with ZIP loads.
From test results on a Polish 2383-bus system, the proposed method demonstrates
fast and reliable time performance compared to traditional numerical methods.
