$currentusersid = Get-WmiObject -Class win32_computersystem |
Select-Object -ExpandProperty Username |
ForEach-Object { ([System.Security.Principal.NTAccount]$_).Translate([System.Security.Principal.SecurityIdentifier]).Value }

Invoke-Command -ComputerName 'whatever' -ScriptBlock {
    $currentusersid = Get-WmiObject -Class win32_computersystem |
    Select-Object -ExpandProperty Username |
    ForEach-Object { ([System.Security.Principal.NTAccount]$_).Translate([System.Security.Principal.SecurityIdentifier]).Value }
}

Get-ADComputer -Filter "name -eq 'Computername'" -Properties sid | select name, sid