I just created a pull request with some code on an implementation of a Z-bus Gauss power flow solver for MATPOWER.
https://github.com/MATPOWER/matpower/pull/40 <https://github.com/MATPOWER/matpower/pull/40> It is a work-in-progress that I wrote some time ago. It seems to work fine for distribution systems without PV buses, but I know the PV bus handling is not correct. For example, case141 solves fine, but not case118. I pushed it because it came up recently in the context of someone asking me about MATPOWER and distribution power flow. If anyone familiar with PV handling in Z-bus Gauss power flow would like to have a look and give me a hand, that would be great. Thanks, Ray
