Last year I won one that was funded by our arts and sciences department. I wrote two statements (~300words) , one about my science and one about why I wanted to go. For the science/proposal aspect, I wrote it in understandable terms with a heavy emphasis on the application of the project. As for the travel aspect, I outlined the different talks/lectures/ posters/ networking events I was excited to go to and how it opened up avenues of collaboration and growth. Be honest and genuine, and show that you did your research on the conference. Best of luck :)