Thanks for your kindly response.
I'm sorry but I have no idea about the account format required by the vCAC workflow. I've only found a brief introduction of user information needed by vCAC in paragraph vCloud Director Integration in What's New Guide of vCloud Automation Center 5.1. Just as follows, does it make sense?
"The user roles within a vCloud Director organization do not need to correspond with the roles in the vCAC provisioning group. For example, it is not necessary for the vCAC provisioning group manager to have vApp author permissions in order to configure vCloud Director blueprints in vCAC, unless the user also needs the ability to create templates in vCloud Director. The only requirement for vCloud Director integration is that any vCAC user who requests a vApp must be a member of the domain associated with the organization VDC on which the vApp is provisioned and must have permissions to log in to vCloud Director Web console."
It seems that the vCAC doesn't need to use any password to access the vCloud Director, because there is no where to input password for the user roles in the vCAC provisioning group. You may visit this webpage for reference: http://www.vcacteam.info/index.php/articles/vcac-configuration/16-step-8-provisioning-groups.