Algorithm and C code for determining the direction of Voltage and Current Harmonics in a three phase electrical system.

We have a metering hardware which takes simultaneous samples of the three voltage waveforms and three current waveforms in a three phase electrical system. These signed samples are filled in an array of 128 members. Thus , there are six arrays , each filled with 128 signed values. We are presently running FFT code on each of these arrays and arriving at the strength of individual odd harmonics ( normalised against the fundamental ) and represented as percentages. e.g. In case of R phase current , we say that 3rd harmonic is 11% , 5th harmonic is 7% , 7th is 4%.....and so on upto 31st. We also arrive at the THD figure for the six waveforms.
Now , we need to perform an additional task .i.e. to determine the source(direction) of these individual harmonics; because the third harmonic being detected could be caused due to the nature of the load OR it could be present in the line to start with . Thus , we need an algorithm and source code to tell us the direction of the individual harmonic.
Input to the algorithm/code segment : Six arrays , 128 deep , filled with signed samples of voltage and current waveforms.
Output : Individual odd harmonics strength in percentage terms( against fundamental) for all six waveforms , THD figures for all six waveforms AND... direction indication for all odd individual harmonics , which will tell us whether the harmonic is present due to LOAD or it is coming from the LINE.