In PLECS, the offline simulation results of the same simulation model differ greatly from the HIL simulation results. How can this problem be solved?

I have built a model that can run successfully in RT-BOX 1. When running purely in PLECS offline, all simulation waveforms are normal. However, when the model is executed in RT-BOX 1, the waveforms are completely inconsistent with those from the offline simulation.

There isn’t enough information here to help you. The issues could range from model construction, application, HIL implementation, signal mapping, etc. You will have to post a model for additional guidance.