Break On

$xlsFileName = @ScriptDir+"\test.xlsx"
$csvFileName = @ScriptDir+"\test.csv"

$oXL = CreateObject("EXCEL.Application")
$oXL.DisplayAlerts = False
$oXLFile = $oXL.WorkBooks.Open($xlsFileName)
$nul = $oXL.ActiveWorkBook.SaveAs($csvFileName, 6)

$oXL.Quit
$oXL = 0