Change SQL server Port by power shell

import-module sqlps;
$MachineObject = new-object ('Microsoft.SqlServer.Management.Smo.WMI.ManagedComputer') "computername"
$instance = $MachineObject.getSmoObject(
   "ManagedComputer[@Name='computername']/" + 
   "ServerInstance[@Name='instancename']"
)

$instance.ServerProtocols['Tcp'].IPAddresses['IPAll'].IPAddressProperties['TcpPort'].Value = "1433"
$instance.ServerProtocols['Tcp'].IPAddresses['IPAll'].IPAddressProperties['TcpDynamicPorts'].Value = ""
$instance.ServerProtocols['Tcp'].Alter()