Synchronous phasor correction under frequency offset

Since frequency offset may cause amplitude and phase angle error in discrete Fourier transform, a method of synchronization phasor correction is put forward, which solves the problem of 0/0 data for deviation in frequency. By uniform approximation using linear and quadratic function the correction equation is simplified and practical amplitude modification expression is derivated. Frequency offset turns round properties to oval properties in amplitude and phase space, and elliptic polar equation is rationally simplified, which avoids the angle mutations caused by discontinuity of tangent function. The mathematical error of this correction was analyzed, and the results show that after correction the errors of amplitude and phase are less than 0.3%, which can meet the engineering requirement. Besides, simulation of signal with noise shows that the correction effect is getting worse when the signal to noise ratio increases. Therefore reasonable design of low pass filter is indispensable.