Low cost mixed-signal microcontroller based power measurement technique

The design and implementation of a mixed-signal microcontroller-based one-phase measurement technique for fundamental active and reactive power is presented. The Goertzel algorithm, which is a special case of the discrete Fourier transform (DFT), is used to extract features of various distorted waveforms including those containing harmonics. It is no longer necessary or economic to use the Fourier transform for evaluating harmonics that are retrievable from the sampled data. To use the Goertzel algorithm yields minimal computational load for the fundamental active and reactive power measurements. A correction factor is developed for the power measurement inherent errors, which emerge due to alternating sampling of the voltage and current waveforms. At the same time, any fluctuations, which may occur on measurement values, are reduced by L-point running averages. Consequently within the time required for fast Fourier transform (FIT) measurement, averaging and corrections are accomplished.