Real-time power measuring and monitoring for an efficient vector-controlled induction motor drive

Efficient variable-speed drives are becoming more and more common in today's industry. With increasing harmonic pollution in the power system, real-time monitoring and analysis of harmonic variation have become important. To evaluate power quantities, it is necessary to consider the presence of harmonics because the drive is fed by a power electronics converter. In this paper, a fully digital algorithm to measure and evaluate main power definitions (active power, fundamental reactive power, fundamental apparent power, apparent power, nonfundamental apparent power, total power factor, displacement power factor, intensity total harmonic distortion, etc.) is presented and applied to an efficient variable-speed vector-controlled 1.5 kW induction motor drive. The system is useful to evaluate efficiency and harmonic pollution at different speed and load conditions. Besides, it allows other power quantities to be used as control variables in the efficiency controller.