have been to和had been to的区别

到现在为止去过某个地方
到过去的某个时间为止去过某个地方

前一个是现在完成时的被动语态，后者是过去完成时的被动语态

现在完成时和过去完成时
前者发生在现在的过去
后者发生在过去的过去

have been to现在完成时
had been to过去完成时
I have been to Beijing before.
I had been to Beijing before I came to Tianjing.

have been + Ving ==I have been taking my exam.

had been + Ving ==He had been taking his exam.