$ftpServer = "RandomFTPServer"
$ftpUser = "Username"
$ftpPassword = Read-Host "Password" -AsSecureString

$credentials = New-ObjectSystem.Net.NetworkCredential($ftpUser, $ftpPassword)

function Get-FtpRequest($ftpPath) {
    $ftpRequest = [System.Net.FtpWebRequest]::Create("$ftpServer/$ftpPath")
    $ftpRequest.Credentials = $credentials
    $ftpRequest.UseBinary = $true
    $ftpRequest.KeepAlive = $true
    $ftpRequest.UsePassive = $true
    return $ftpRequest
}

# Load WinSCP .NET assembly
Add-Type -Path "WinSCPnet.dll"

# Setup session options
$sessionOptions = New-Object WinSCP.SessionOptions -Property @{
    Protocol = [WinSCP.Protocol]::Ftp
    HostName = "ftp.example.com"
    UserName = "username"
    Password = "password"
}

try
{
    # Connect
    $session = New-Object WinSCP.Session
    $session.Open($sessionOptions)

    # List files
    $remotePath = "/remote/path"
    $directoryInfo = $session.ListDirectory($remotePath)

    # Find old files
    $limit = (Get-Date).AddDays(-15)

    $oldFiles =
        $directoryInfo.Files |
        Where-Object { -Not $_.IsDirectory } |
        Where-Object { $_.LastWriteTime -lt $limit }

    # Delete them
    foreach ($oldFileInfo in $oldFiles)
    {
        $oldFilePath =
            [WinSCP.RemotePath]::EscapeFileMask($remotePath + "/" + $oldFileInfo.Name)
        $session.RemoveFiles($oldFilePath).Check()
    }

    Write-Host "Done"
}
finally
{
    # Disconnect, clean up
    $session.Dispose()
}

: delete files older than 7 days from ftp://my.ftpsite.net/folder/subfolder
ftpuse F: my.ftpsite.net password /USER:username
timeout /t 5
forfiles -p "F:foldersubfolder" -s -m *.* -d -7 -c "cmd /C DEL @File /Q"
ftpuse F: /DELETE