Power system impedance tracking using sliding, finite memory complex recursive least squares

An efficient implementation of the method for tracking time varying power system impedance is presented in the paper. This noninvasive method uses only voltage and current waveforms recorded at the point of common coupling. It does not use any additional disturbance sources. The base of the method is least squares algorithm performing computations in complex space using phasors of voltage and current. In order to allow for tracking time varying impedance the algorithm uses finite memory. A two stage, recursive realization is proposed in order to keep computing requirements as low as possible.