I was trying to create a term group in SharePoint Managed Meta Data term store through visual studio at the time of feature activation and I faced this issue.
“The current user has insufficient permission to perform this operation”
I have already written my code under SPSecurity.RunWithPrivileges() but I still faced the same problem. After that I have tried to create a term group using PowerShell , but again the same error.
The problem was user does not have the sufficient permission to create group. To solve this problem go to the central admin and Managed Meta Data service user interface. Add the user in “Term Store Administrators” section as shown in below image.