APPARATUS AND METHOD FOR MEASURING A PHASOR OF AN ELECTRICAL POWER SYSTEM SIGNAL

摘要

An apparatus and a method for measuring a phasor of an electrical power system signal (20) is described. The power system signal (20) has a cycle having a predetermined period and is sampled to produce a sample stream (22) of the electrical power system signal (22) The apparatus comprises a processor ( 14) configured to measure a phasor in phase-space by using the value of a first sample from the sample stream (22) to represent the x-coordinate of the phasor and by using the value of a second sample from the sample stream (22) to represent the y-coordinate of the phasor The second sample is delayed by a quarter of the predetermined period from the first sample. In further implementations, the apparatus and method may take into account a DC offset of the power system signal (20) The apparatus may then further comprise a DC offset calculation unit(24) for calculating a DC offset (26) of the sample stream (22) The processor (14) is further configured to subtract the DC offset (26) from the sample stream (22), thereby generating a DC-corrected sample stream The DC-corrected sample stream is then used to determine the x and y coordinates of the phasor