Powershell query to find all SQL Instance names alone and export to .Txt

I am writing a query to find the SQL Servers which are all UP & Running. While doing so, I find that each instance has multiple SQL Instances. How to write a good powershell query to export all the SQL Instance details and export to Excel and .TXT so that at a next step I can check for tge ping status using win32_pingstatus Get-WMIObject class.Please suggest.Thanks in advance