export Integration Services Catalogs project using powershell

We can manually take backup of existing "Integration Services Catalogs project" by right click on it and give "export" option which will give an .ispac file.
I am trying to automate this export operation by using below powershell script.

Param(
[Parameter(Mandatory=$true,ValueFromPipeline=$true)]
[string]$Datasource = $null,
[Parameter(Mandatory=$true)]
[string]$MasterDBName = $null,
[Parameter(Mandatory=$true)]
[string]$SSISDBName = $null,
[Parameter(Mandatory=$true)]
[string]$FolderName = $null,
[Parameter(Mandatory=$true)]
[string]$ProjectName = $null,
[Parameter(Mandatory=$true)]
[string]$DestinationPath = $null
)

# Load the IntegrationServices Assembly
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.Management.IntegrationServices") | Out-Null;

# Store the IntegrationServices Assembly namespace to avoid typing it every time
$ISNamespace = "Microsoft.SqlServer.Management.IntegrationServices"

Write-Host "Connecting to server ..."

# Create a connection to the server
$sqlConnectionString = "Data Source=$Datasource;Initial Catalog=$MasterDBName;Integrated Security=SSPI;"
$sqlConnection = New-Object System.Data.SqlClient.SqlConnection $sqlConnectionString

# Create the Integration Services object
$integrationServices = New-Object $ISNamespace".IntegrationServices" $sqlConnection

$catalog = $integrationServices.Catalogs[$SSISDBName]

$fld = $catalog.Folders[$FolderName]
$prj = $fld.Projects[$ProjectName]

$ispacfilename = "test.ispac"
$ispacfullpath = Join-Path $DestinationPath $ispacfilename
Write-Host "ispacfullpath    $ispacfullpath"
$xmlwriter = [System.Xml.XmlWriter]::Create($ispacfullpath)
$prj.Serialize($xmlwriter)
$xmlwriter.Close()

 While execution it throws the below error

Exception calling "Serialize" with "1" argument(s): "The parameter 'sink.Action' is invalid."
At C:\T_ISCRMS_SSIS2012_Export.ps1:46 char:1+ $prj.Serialize($xmlwriter)+ ~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException+ FullyQualifiedErrorId : IntegrationServicesException

I understand that Serialize method accepts only System.Xml.XmlWriter object.
Please let me know how i can export/serialize to a ispac file which is based on binary serialization.

Reference:
https://msdn.microsoft.com/en-us/library/microsoft.sqlserver.management.integrationservices.projectinfo(v=sql.110).aspx
https://msdn.microsoft.com/en-us/library/microsoft.sqlserver.management.sdk.sfc.sfcinstance.serialize(v=sql.110).aspx