Here you have an example of poweshell execution without opening window. just replace the -File path and assign or remove parameters when needed:
Process.Start("powershell"," -NoLogo -NonInteractive -File C:\Scripts\YouScript.ps1 -Param1 TestBackup");
Simplest example:
Process.Start("powershell.exe","C:\Scripts\MyScript.ps1");
Another one using string formt and single quotes for arguments:
Process.Start("Powershell.exe", @"""ScriptwithArguments.ps1"" 'arg1' 'arg2 asdf'");