INCREASING ACCURACY OF ACTIVE POWER MEASUREMENT OF NON-COHERENTLY SAMPLED SIGNALS BY TIME DOMAIN SIGNAL PROCESSING

摘要

The paper analyses an effective method of increasing accuracy of active power measurement (and energy measurement) by non-coherent sampling. The measurement bias caused by non-coherent sampling are reduced by windowing the instantaneous power sequence of samples by various generalized cosine windows. Active power is found by processing signal in time domain, without using FFT. Newly obtained analytical formulae are given, a comparison to classical method and numerical simulations verifying the derived formulae are presented. A simple method of compensation multiplexing delay by measurement using multiplexing DAQ plug-in board is explained and verified both in simulation and measurement. Application of windowing for measurement of multifrequency signals is also included, formula for standard uncertainty of active power estimate is given. Basic numerical integration methods applied to quantized input signals in power computation are briefly compared, and numerical values showing decrease in power bias for selected windows are shown.