New-SqlServerAlias.ps1

function New-SqlServerAlias($name, $server='.', $protocol='tcp', $port='1433') {
  $options = New-Object System.Management.ConnectionOptions
  $options.Context.Add('__ProviderArchitecture', 64)

  $path = '\\.\root\microsoft\sqlserver\computermanagement11'
  $scope = New-Object System.Management.ManagementScope($path, $options)
  $scope.Connect()

  $managementPath = New-Object System.Management.ManagementPath('SqlServerAlias')
  $class = New-Object System.Management.ManagementClass($scope, $managementPath, $null)
  $alias = $class.CreateInstance()
  $alias.SetPropertyValue('AliasName', $name)
  $alias.SetPropertyValue('ServerName', $server)
  $alias.SetPropertyValue('ProtocolName', $protocol)
  $alias.SetPropertyValue('ConnectionString', $port)
  $alias.Put()
}