Powershell command to convert all xlsx files in a directory to csv files.

excel2csv.ps1

$excelApp = New-Object -ComObject Excel.Application;`
$excelApp.DisplayAlerts = $false;`
Get-ChildItem -File -Filter '*.xlsx' | ForEach-Object { `
    $workbook = $excelApp.Workbooks.Open($_.FullName);`
    $csvFilePath = $_.FullName -replace "\.xlsx$", ".xlsx.csv";`
    <# If Microsoft.Office.Interop.Excel.XlFileFormat, try running from Visual Studio Developer Powershell #>`
    $workbook.SaveAs($csvFilePath, [Microsoft.Office.Interop.Excel.XlFileFormat]::xlCSV);`
    $workbook.Close();`
}