Acquisition system for power measurements and harmonics determination

This paper presents a practical power and energy measuring and monitoring system using microcontrollers from the PIC 16Fxxx family, conditioning circuits for current and voltage acquisition and a virtual instrument developed in LabWindows/CVI. The developed system can be used in a single-phase power system, but it can be enlarged very easy for three-phase power system. The conditioning circuits shift the current and voltage signal in the A/D converter signal domain. The microcontroller is responsible for the data acquisition and the communication with the computer. Measured data from the sensors is represented in real time, with the possibility of saving the measured data set for later evaluation. For data representation and harmonic analysis in distorting cases a virtual instrumentation based on LabVIEW was developed. The designed virtual instrument calculates from the acquired data the active and reactive power, the power factor and the frequency and level of the harmonics in case of nonsinusoidal signals.