Re: Set expiration of accessToken through powershell

For Power BI embedded, you can get an token that never expires by using this sample in github. 

Generate an accesstoken that never expires(not recommended).

var embedToken = PowerBIToken.CreateReportEmbedToken(this.workspaceCollection, this.workspaceId, report.Id,Convert.ToDateTime("2099-12-31"));

For Power BI Service, I think there shall be some approach though I'm not aware of any, but you could quickly get a valid token by following

1. Log in Power BI Service and load some report.
2. With the help of Chrome dev tool(F12), click on some network request and you'll see the token there.