What Is Positive Sequence Unbalance Current in 3-Phase Power Systems?

I'm a mechanical engineer assigned to a project involving electrical power generation, which is a little out of my field. There are a number of derived parameters involving symmetrical components (representing unbalanced 3-phase phasor data and the sum of a balanced positive sequence phasor, a negative sequence phasor and a zero sequence phasor. This is useful in analyzing unbalanced 3-phase circuits and in particular analyzing faults.
One of the required parameters is "Positive Sequence Unbalance Current". It doesn't make any sense to me and I can't find a reference that covers it.
Can anyone explain "Positive Sequence Unbalance Current" and/or recommend a reference?

Hi Stephen-Sorry for the long delay in responding.  You've stumped us on this one.  The ONLY reference I can find is in this link: Coordinated Control of Power Electronic Converters in an Autonomous Microgrid .  I presume that's where you saw the term. I think the best option would be to try to contact the author of the thesis.Sorry I can't be more help.-Rick