You can not set the value of a person type column using the workflow

In my sharepoint application, when a list is saved, it will call a workflow. In the workflow, I am trying to configure the field assigned to (type of person) with a value in Approver Name (this is the string value that is the display name of the name field that is type of person). But this value is not being established. There is no error, but the value in the field assigned to is null