FPGA-based compensation of current transformers

Voltage and current transformers are the most installed transducers in electrical power system and typically they are constructed to operate at industrial frequency, 50/60 Hz. On the other hand power quality analyses in the last years has assumed more and more heaviness in industrial environments, due to the presence of non-linear loads: they require measuring instrumentation with large bandwidth. Therefore in this paper a real-time digital technique for the compensation of current transformers, based on field programmable gate array, is presented: it implements a digital filter with a frequency response equal to the inverse one of CT. The compensated CT continues to be an analog device since the FPGA board is opportunely equipped with analog to digital and digital to analog converters. Experimental results have shown that the compensated CT improves performances of the original CT of a factor 24.