In regional power grids， substations of a high-voltage level provide power to a low-voltage grid， operating like power sources. This paper first defines the high-voltage buses of those substations as dummy power sources. Different from real generators， the voltage of the dummy power source varies with its power injection. A sensitivity formula for describing the relation between the voltage and the power injection of the dummy generator is proposed. Then considering the requirement for inverse voltage regulation of the substation's control bus and the voltage characteristics of the dummy power sources， a new model for multiple-objective dynamic reactive power optimization in regional power grid is proposed. Relative to the conventional model， the new model also has the characteristics of multi-time periods and nonlinear mixed-integer programming， but without the generator and voltage as independent control variable， but with two constraints added， including the voltage objective of pilot buses and the constraint of the power factor. Hence， it has more practical value.