Prediction of harmonic distortion and application of power-factor correction in AC power systems

摘要

In a method for predicting harmonic-distortion values for the application of a desired step change of capacitance to an AC system, an initial step change is applied and, from this change, a value of harmonic impedance of the system for each of a number of harmonics is determined. From these harmonic-impedance values corresponding values of damping resistance are, in turn, determined and, using the determined harmonic- impedance and damping-resistance values, corresponding values of an electrical load parameter, preferably load voltage, are determined for the desired step capacitance change. The method is conveniently extended to cover a method and apparatus for applying power-factor correction capacitance, in which the load-voltage values for the various harmonics are evaluated to see if they represent a potential resonance condition and, if so, a step change other than the desired change is applied. Where no resonance is indicated, the originally intended step change is applied.