Connect-VIServer -Server <vCenter Server>
$AllHosts = Get-Cluster <Cluster Name>
foreach ($ESXHost in ($AllHosts | Get-VMHost))
{
 Get-VMHost $ESXHost | Get-VirtualSwitch -Name <vSwitch Number> | New-VirtualPortGroup -Name
<Virtual PortGroup Name> -VLanId <VLan ID>
}
Disconnect-VIServer -Confirm:$false