Eli Yablonovitch has spoken extensively about this. Here is one talk (https://www.youtube.com/watch?v=u_K1URyarE0) but I think he makes the point elsewhere that the central government in China told their regional governments that they would need to close down their smaller scale PV production with the result that they all added capacity to meet the minimum causing an even greater production glut.

Edit: I found the source (cued up for 37:25) https://youtu.be/lDxJsa8miNQ?t=2245