You can get the dell power plan back by restoring factory image. If you did a full format on hard drive than run SupportAssist. It will install SA OS recovery and create that factory image partition.      Although all that efforts would not be worth. Microsoft itself is getting rid of power plans and you control them by using battery slider. (favor performance or battery)  You don't even need that cause , your model you get much more deeper customization of power settings from Alienware command center. 
Hello! I recently bought a Dell G5 15 5500.I made a clean install and installed the necessary drivers. Now miss me the dell power plan and options of extension of battery life. What tool/driver should I install for those back? Thanks
G5 15 5500, Dell power plan missing