Hi Raj,
The system will indeed not allow you to close 2013 without posting planned depreciation and without closing 2013 you will not be able to open 2015.
Assuming that there is a planned depreciation still to be posted (something you can check from the asset explorer), I suggest that you run the depreciation posting program in a productive (repeat) run then write up the posted depreciation amount using transaction ABZU. You may have to re run the depreciation after while but it should not create any posting.
I suggest that you first test this process in a test system.
Good luck and best regards
Thomas