By default, Hyper-V tries to figure out which Virtual Machines were powered on at the time that your PC had its power cut. It uses this list to automatically turn Virtual Machines back on when your PC powers on. Here is how to change what gets switched back on.
Unfortunately, Virtual Machine startup behavior is configured at the Virtual Machine level and therefore needs to be set for each Virtual Machine separately. So go ahead and right click on the first virtual machine and choose to open its settings from the context menu.