Pulse width modulation (PWM) method for power components estimation under harmonic distortion conditions

In this paper a Pulse Width Modulation (PWM) based method for the measurements of both Active Power (AP) and Reactive Power (RP) under harmonic distortion conditions in power systems is proposed. The method takes advantage of the fact that frequencies present in a power line are of a specific fundamental frequency range (a range centred on the 50Hz or 60Hz) and that in case of the presence of harmonics the frequencies of those dominating in the power line spectrum can be specified on the basis of the fundamental. In contrast to a number of existing methods a time delay or shifting of the input signal is not required by the method presented and the time delay by π/2 of the Current signal with respect to the Voltage signal required by many of the existing measurement techniques, does not apply in the case of the PWM method as well. Another advantage of the presented method is that the fundamental frequency of the power line is considered as an unknown parameter simultaneously estimated with the signal's spectrum, so the method becomes insensitive to fundamental power line frequency changes. Complex computations that include multiplication of the Voltage and Current sample values by trigonometric functions are also avoided.