Technically, it is simply a series.
Usually, when you look at writers' bibliographies on Wikipedia, multi-cycle series are usually grouped under a heading that refers to what they all have in common. For example, several of the novels of C. J. Cherryh are grouped under "the Alliance-Union universe". In this case, "universe" is the term used to describe the connection between otherwise only vaguely related novels and novel cycles.
But from a technical point of view, that is, disregarding the content of the books, all these books form a series in that they are published one after another and are meant by the author and publisher to be perceived as belonging together.
Wikipedia has an article where what you are talking about is called a "novel sequence", but that is the first time I have encountered that term and am not sure it is actually used except ad hoc. That page also gives the model of
trilogy < sequence < 'saga' grouping (single author) < shared universe < genre, which I find interesting and appropriate, except that I would replace "sequence" with "series" and would maybe drop "saga", because it implies a unity of protagonist, place or topics that is not present in many series' of novels set in the same world.