Career
Kupenov made his unofficial debut for the first team of Botev Plovdiv on 15 November 2014. On 23 May Kupenov was included in the squad for the 1-2 away defeat from Beroe Stara Zagora but remained an unused substitute. On 24 February 2016 it was reported that he would be sent on loan until the end of the season to Septemvri Sofia.
Two days later it was confirmed that he was sent on loan, but to Dobrudzha Dobrich.
Kupenov has earned several caps for the Bulgarian U18 team In March 2016 Kupenov was in the starting lineup of Bulgaria U19 for the 0-1 defeats from Belgium U19 and Croatia U19.