Pulse Width Modulation (PWM) Method for Power Components Estimation - Active and Reactive

This paper presents a Pulse Width Modulation (PWM) based method for Active Power (AP) and Reactive Power (RP) measurements in electric sinusoidal and Non-sinusoidal power systems. The method takes advantage of the fact that frequencies present in a power line are of a specific fundamental frequency range ('a range centred around 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 order to estimate the power components in a generalised power line, in the first stage the elimination of any harmonics present and the identification of the power line fundamental frequency are cascaded by the application, in the next step, of a PWM stage at which a Pulse Wave is generated based on the frequency of the fundamental. In the final stage of the method the power components are calculated. In the major advantages of the proposed method are included: a) in contrast to a number of existing methods a time delay or shifting of the input signal is not required, b) the method does not involve a time delay by pi/2 of the Current signal with respect to the Voltage signal, c) the fundamental frequency of the power line is considered as an unknown parameter, simultaneously estimated with the signal's spectrum using the Fast Fourier Technique ('FFT) and so the method is insensitive to fundamental power line frequency changes, and d) complex computations that include multiplication of the Voltage and Current sample values by trigonometric functions are avoided.