The state estimation method based on using control equations for state vector and measurement error computation is considered in the article. This method takes into account the restrictions on operating parameters as equalities and inequalities. To take into account the restrictions as equalities and restrictions disturbances fixation as inequalities an absolutely accurate measurement concept, i.e. the measurement when dispersion is equal to zero, is used. This method enables to calculate the electrical power systems modes considering power flows fixation, frequency maintenance in a system due to specified generating station power control, voltage maintenance in units.