There are various website that can provide you wbjee previous year papers with solution.But for entire previous 15 years papers you can also but a books published by arihant publication as it carries all question of past year with solution.
I am providing you a link below where you can download ebook of sample paper of wbjee.
I hope this helps.
IIT/JEE 2020 Online Preparation
Crack JEE 2020 with JEE Knockout Program, If you Do Not Qualify- Get 100% MONEY BACK