I had an issue related to IP change. Is it typical for a raspberry pi to randomly change the IP? When I ran the command ifconfig, I noticed that under wlan0 inet, my IP address changed. I was made aware of this when I noticed I couldn't connect via SSH. I'm not sure if this was a result of me touching the wlan0 settings to set power management off and also adding and removing these 2 lines in the /etc/network/interfaces file:

 1. source-directory /etc/network/interfaces.d  
 2. wireless-power off

My ultimate goal before all this happened, was to get the power management setting for wifi to be permanently off. My raspberry pi disconnects from the wifi network every few days. 

Im hoping someone can shed some light on what happened and how to successfully stop the wifi dropping connection.