  A generalized model with three active and three sterile neutrinos is
considered on the basis of the experimental data, which allow existence of
anomalies beyond the minimally extended Standard Model with three active
neutrinos with different masses. One of the sterile neutrinos is assumed to be
comparatively heavy versus the two others, that is corresponding to the
$(3+1+2)$-model of neutrino. The model parameters used for the description of
oscillations of both active and sterile massive neutrinos are given. In the
approximation of CP-conservation, the solar neutrino oscillation
characteristics together with the sterile neutrino contributions have been
evaluated taking into account the neutrino interaction with the matter inside
the Sun. The results obtained are in accordance with the observational data and
can further be used for the description of neutrino oscillations in
astrophysical and terrestrial environments and in search of sterile neutrinos.
