Application of eigen- decomposition of signals to harmonic noise detection and cancellation, in electric power systems

A new technique for estimating the frequency contents in a signal is applied to a three-phase shunt active power filter (APF) to compensate the harmonics and reactive power introduced by the nonlinear loads. The technique utilizes two sets of measured samples: samples from the signal itself and samples from a filtered signal obtained by passing the original signal through a continuous-time filter. The estimates of the frequencies contained in the signal are obtained from the eigenvalues of the generalized eigenproblem of two matrices formed from the two sets of samples. Upon detecting the harmonic components of the load currents by the proposed technique, an APF injects these harmonic current components with same magnitude but opposite phase into the power system to eliminate these harmonics and keep the utility line current sinusoidal and in phase with the utility voltage. Simulation results with different nonlinear loads are presented to confirm the validity of the proposed technique.