Sinusoid Approximation of Instantaneous Signal for Power System--Definiteness Analysis

The definiteness and uniqueness of sinusoid expression is theoretical foundation of sinusoid approximation method for instantaneous signal of power system. In this paper, the uniqueness of sinusoid expression for instantaneous signals of three types of circuits are attested respectively by means of simulating the equivalent one order, two orders, and n orders linear circuits of power system network. Corresponding analysis process is detailed, and figures are illustrated for one order RL and two orders RLC circuits. Results proved that sinusoid expression of instantaneous signal of power system is unique and definite under unchanged source frequency condition which is always true in a short time after disturbance and could be accepted for engineering applications.