i was updating my macintosh hd my power went out in my house do to a power outage and now my computer keeps cutting on and off. can anyone help?

Your computer uses macOS 10.x.x, not iOS 11.x.x. If you have a Late-2010 or later model you can do a Network Recovery. This will erase and reformat the drive.

Clean Install of El Capitan or Later on a Clean Disk

1. Restart the computer. Immediately after the chime hold down the Command-Option-Rkeys until a globe appears.
2. The Utility Menu will appear in from 5-20 minutes. Be patient.
3. Select Disk Utility and click on the Continue button.
4. When Disk Utility loads select the drive (usually, the out-dented entry) from the side list.
5. Click on the Erase tab in Disk Utility's main window. A panel will drop down.
6. Set the partition scheme to GUID.
7. Set the Format type to Mac OS Extended (Journaled.)
8. Click on the Apply button, then click on the Done button when it activates.
9. Quit Disk Utility and return to the Utility Menu.
10. Select Reinstall OS X and click on the Continue button.

This should install the version of OS X that was currently installed. To install the original factory version when the computer was new use Command-Option-Shift-R.