Download all WSP file from Central Admin -SharePoint 2013

Step 1: Save below script  ExtractWSP.PS1 file
---------------------------------------------------start script------------------------

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null)

{

    Add-PSSnapin "Microsoft.SharePoint.PowerShell"

}

$dirName = "F:\JaisonArumugam\WSP"

Write-Host Exporting solutions to $dirName

foreach ($solution in Get-SPSolution) 

{ 

    $id = $Solution.SolutionID

    $title = $Solution.Name

    $filename = $Solution.SolutionFile.Name

    Write-Host "Exporting '$title' to …\$filename" -nonewline 

    try { 

        $solution.SolutionFile.SaveAs("$dirName\$filename")

        Write-Host " – done" -foreground green 

    } 

    catch 

    { 

        Write-Host " – error : $_" -foreground red 

    }

}

--------------------------------------------------end script----------------------------------

Save .bat file and execute run with admin..

cd /d %~dp0

powershell -noexit -file "ExtractWSP.PS1" "%CD%"

pause