If the owner of the apartment or block in which you are registered is in Ukraine, you will only need to send him a statement certified by the Consulate that you agree to deregistration. He will have full right to carry out the deregistration procedure even without your presence.
If you are the sole owner of the home in which you are registered, then you have the opportunity at the Consulate to issue a power of attorney for someone who is currently in Ukraine and has the opportunity to carry out the procedure for deregistration of the place of residence for you.