Excel writer error with bi-server

Hi,
I can't execute kettle's transformation including Excel Writer on Bi-server. I know that in previous version of Kettle and bi-server, we need to copy excel writer plugin folder from Kettle to 'pentaho-solutions/system/kettle/plugins/steps/ExcelWriter' to make it work.
But in version 4.4 I can't find this folder.
So what can i need to do to "install" excel Writer on Bi-server.
I just want to point out that the transformation work fine on kettle on the same server.

Thanks for your help.