Can the power company cut 15 feet into the woods that surround my property?

The answer to your question depends upon the facts.  Probably, there is an easement for a double purpose.  One is to maintain the drainage ditch to control surface water, and the other would be to permit the power company to maintain electrical lines at essentially the same place -- but up above.  The text of the easement would tell whether the power company cut outside its easement.  Ordinarily, power company easements allow the trimming or cutting of growth that is inside the easement area and many also allow the trimming/cutting of growth that threatens the wires even if outside some specified boundary.  Such easements are intentionally vague so as to allow some discretion on the part of the power company to decide what might threaten their lines.  If you truly feel the trimming was excessive, make an appointment to see a good real estate attorney and ask him/her to review the power company's easement.  If the power company has cut outside its easement boundaries, you may have a cause of action against it.  In such event, the big question will probably be proving the "financial" amount of your damages.  In order to be successful in court, you must not only prove that the adversary is guilty of some wrongful conduct, but you must also prove that it damaged you to a specified amount -- and that the amount in controversy is large enough to justify the costs of litigation.