We study effects of periodic fields on charge transport in macromolecules and show that solitons acquire complex dynamics induced by the interplay between the periodic in time external field, energy dissipation, and depends on the molecule symmetry. Soliton dynamics is a superposition of the oscillations of the soliton c.m.c. with the frequency of the external field and directed current. Even unbiased periodic in time fields can cause drift of solitons (the ratchet effect) in the Peierls-Nabarro periodic potential. This effect has a threshold with respect to the intensity and frequency of the field. We calculate the dependence of the amplitude of soliton oscillations and the velocity of the drift on the intensity of the field, its frequency, and energy dissipation. Thus, we show that nonlinear charge transport processes in a field which is periodic in time acquire completely different dynamics than linear processes. This clearly plays a role in metabolism of biosystems.