Use Powershell to Export Excel to CSV

export_excel_to_csv.ps1

# Export Excel sheet to CSV file
# $File: file path
# $SheetNames: An array, sheet names to export.
Function Export-ExcelToCsv ($File, $SheetNames) {
    $Excel = New-Object -ComObject Excel.Application
    # SaveAs will overwrite existing file
    $Excel.Application.DisplayAlerts = $False

    $wb = $Excel.Workbooks.Open($File)

    $x = $File | Select-Object Directory, BaseName

    foreach ($ws in $wb.Worksheets) {
        # -1 is for xlSheetVisible
        if (($SheetNames -contains $ws.Name) -and ($ws.Visible -eq -1)) {
            $baseName = ($x.BaseName, $ws.Name) -join "_"
            $n = [System.IO.Path]::Combine($x.Directory, (($baseName, 'csv') -join "."))
            # 62: xlCSVUTF8 (UTF8 CSV)
            $ws.SaveAs($n, 62)
        }
    }
    $Excel.Quit()
}

$FilePatterns = @("*.xlsx", "*.xlsm", "*.xml")
$SheetNames = @("a", "b")

Get-ChildItem -Path .\* -Include $FilePatterns |
    ForEach-Object {
        Export-ExcelToCsv -File $_ -SheetNames $SheetNames
}