Since version 1.3.4 of the IG, the frequencyPerDay is defined as "This field indicates the requested maximum frequency for an access without PSU involvement per day. For a one-off access, this attribute is set to "1". The frequency needs to be greater equal to one. If not otherwise agreed bilaterally between TPP and ASPSP, the frequency is less equal to 4."
The PSU-IP-Address is therefore an indicator that a recurring consent can be used more frequently than permitted by the frequencyPerDay.