"have had to" and "had had to" are the perfect forms of "have to"/"has to"/"had to", so it operates very similarly to the difference between the simple and perfect in other cases:

I have to eat before noon

compared to

I have had to eat before noon every day this week

The first is an obligation one time; the second specifies a recurring obligation started in the past but with current relevance.

The difference between "had to" and "had had to" is similar but in the past instead of the present; the past perfect "had had to" would express a past obligation starting before another past event with continued relevance to the second past event.

"have had to" and "had had to" are the perfect forms of "have to"/"has to"/"had to", so it operates very similarly to the difference between the simple and perfect in other cases:

I have to eat before noon

compared to

I have had to eat before noon every day this week

The first is an obligation one time; the second specifies a recurring obligation started in the past but with current relevance.

The difference between "had to" and "had had to" is similar but in the past instead of the present; the past perfect "had had to" would express a past obligation starting before another past event with continued relevance to the second past event.

I had to eat before noon last Friday to be able to catch my bus

compared to:

I had had to eat before noon every Friday last year to be able to catch my bus