My university requires me to hand in 3 candidature assessment reports over the course of my PhD (the third being essentially the thesis, I'm on my first one). The report has the structure of a thesis (this isn't a requirement, but is how I'm structuring it). My thesis topic is actually fairly broad, so the actual journal papers will be on subtopics within the field. I have a main Introduction which introduces the broad topic, then separate sections that basically reproduce a draft paper and placeholder for a second paper which I will be starting on. Each section will have its own "mini-introduction" to introduce the reader to that subtopic. So my question is, is it normal to have multiple introductions in a report?
It is good writing practice to think of any document as having a hierarchical -- even fractal, if you're into these things -- structure: Every section contains a mini-introduction that spells out how what you're going to discuss in the following connects to what you've done before, and a mini-summary at the end that sets the stage for how what you just did leads to the next question.
At the sub-sub-subsection level, these mini-introductions and mini-summaries may be just a sentence or two long, but it's good to get into the habit of seeing that every section could be read on its own by connecting it explicitly to material before and after.
As such, it is entirely appropriate to have the mini-introductions you talk about in your question.