Sinusoid Approximation of Instantaneous Signal for Power System--Theory and Method

This paper presents a novel method to analysis instantaneous signal, which can be used to calculate the amplitude and phase corresponding to each sampling point precisely and efficiently, especially for power system applications. Under fixed frequency assumption, the proposed method is developed based on sinusoid approximation and the physical and mathematic research on power system instantaneous signal characteristics. The fundamental RL and RLC circuits are utilized to test this method by comparing the results of digital simulation and analytic computation which show that they coincide with each other perfectly. The method has been used to select fault feeder in Petersen coil grounded distribution power system successfully and could be applied in ultra high speed protection system and many other fields.