Below is the control to output transfer function of a boost converter. (source: Switching Power Supplies A - Z by Sanjaya Maniktala here at page 286)
And this is one part talking about the RHP zero the book. I don't understand the last part from "Eventually...".
When output voltage dips, the controller adjusts to increase duty cycle. However, by increasing duty cycle the time to transfer energy to load decreases.
If everything goes on like this, finally the duty cycle will go to 1 and no time for transferring energy to load.
But the note below says that eventually the inductor current ramps up to the right level and the strange behavior gets corrected.
Why duty cycle not go to 1?
Note: Intuitively, the RHP zero is often explained as follows — if we suddenly increase the load, the output dips slightly. This causes the converter to increase its duty cycle in an effort to restore the output. Unfortunately, for both the boost and the buck-boost, energy is delivered to the load only during the switch off-time. So, an increase in the duty cycle decreases the off-time, and there is now, unfortunately, a smaller interval available for the stored inductor energy to get transferred to the output. Therefore, the output voltage, instead of increasing as we were hoping, dips even further for a few cycles. This is the RHP zero in action. Eventually, the current in the inductor does manage to ramp up over several successive switching cycles to the new level consistent with the increased energy demand, and so this strange situation gets corrected — provided full instability has not already occurred!