Nice to use stored procedure to add registered servers.

But if you want to use PowerShell, you can check my article at: http://www.mssqltips.com/sqlservertip/3252/automate-registering-and-maintaining-servers-in-sql-server-management-studio-ssms/

It can be a good complementary reading to the pure t-sql way described in this article.

It will not only handle "Central Management Servers", it can also handle "Local Server Groups", however, I just use configure file for simplicity reason.

Kind regards,

Jeff_yao