Analysis on the voltage stability and the allowed penetration capacity of distributed generations in Yuhang power grid

The increasing amount of the integration of distributed generations (DG) will bring about some adverse effects on the static and transient voltage stability, or even threaten the reliability and the safety of the whole power grid. The integration capacity of DGs is the main fact that contributes to the impact on the voltage stability. As DGs are connected to the grid through electronic interface, different kinds of control methods affect voltage stability significantly as well. This work mainly focuses on the DG integration to Yuhang power grid, and the outside part of this grid can be equivalent to a Thevenin circuit. The analytic expressions of the voltage and the power penetration rate at the DG connected node are derived. On this basis, the stability characteristics of the load voltage under different DG penetration rates are analyzed. Moreover, the effects of different reactive power control strategies on voltage static stability are compared with each other, and the transient voltage stabilities under different DG penetration rates are also discussed. Finally, the allowed penetration rate for Yuhang power grid is determined after checking the static and transient stability. The results show that the system can support more loads if the penetration of DG is increased appropriately.