“Has been” and “have been” are both in the present perfect tense. “Has been” is used in the third-person singular and “have been” is used for first- and second-person singular and all plural uses. The present perfect tense refers to an action that began at some time in the past and is still in progress. For example, if I started studying art when I was 13 years old and I am still studying art, I would say “I have been studying art since I was 13 years old.”

“Had been” is the past perfect tense and is used in all cases, singular and plural. The past perfect tense refers to something that began in the past and was still true at another time that also was in the past. So, if I began studying art when I was 13, and I got married when I was 21, and now I am 55, I could say “When I got married, I had been studying art for 8 years.” The “when I got married” part identifies a specific time in the past, and the “had been studying for 8 years” says that the studying was still going on at another time that is alos in the past. Note that it does not matter, in this case, whether I am still studying art in the present – the sentence is correct either way.