A simplified model is used to approximate the energies of observed structures in smectic B-2- phase composed of bent-shaped molecules. Twisted, mixed (having alternating layers with twisted and uniform molecular structure) and anticlinic antiferroelectric structures coexist without an applied field having thus nearly the same energies. When an electric field is applied, mixed structure starts to be preferred. The first critical field compensates surface polar anchoring on e.g., upper sample surface and favorites partly unwound structure. The second critical field leads to transition to uniform synclinic ferroelectric structure. The behavior of the energies of B-2-phase structures under an electric field permits the estimation, of model parameters, like e.g., anchoring energies.