Impact of Varying Shares of Distributed Energy Resources on Voltage Stability in Electric PowerSystems

The increased power supply of distributed energy resources and the simultaneous reduced power supply or shutdown of conventional power plants are changing the dynamics of the power system. This paper investigates the impact of a varying share of distributed energy resources on system dynamics during a slow voltage collapse. Dynamic simulations are carried out to analyse how system dynamics change in different generation situations. Various reactive power strategies of distributed energy resources as well as reduced power supply of conventional generators are considered. The simulation results show that with a high share of distributed energy resources, their non-existent overload capability lead to a limitation of their reactive power, which can have a negative impact on voltage stability. However, these effects are less pronounced in less voltage-critical regions. Moreover, static reactive power supply as well as partially shut-downs of power plants and their earlier limitation by the overexcitation limiter can further destabilise the system.