Abstract
The high penetration of distributed energy resources (DERs) in the distribution system brings new challenges related to voltage variations and reverse power flow. The sudden changes in electric power generation from the DERs due to climate conditions or their internal malfunction might cause high fluctuations in system voltage. To enhance the voltage stability when a disturbance occurs, this paper proposes a new reactive power management method to control each DER based on voltage sensitivity analysis. The voltage variation has the different features in both steady-state and transient conditions. In particular, its transient behavior depends on the type of DERs. Therefore, the particular optimal control for improving the dynamic response of voltage is difficult to apply for all types of DERs. In contrast, the voltage variation in steady-state can be controlled with the reactive power management by the sensitivity analysis between reactive power generation and system voltage. Even though this paper focuses on the reduction of voltage variation in steady-state, the relationship between the voltage variations in steady-state and transient conditions is also analyzed. The effectiveness of the proposed method is verified with several case studies on the practical distribution system in South Korea by using the time-domain simulation based on the PSCAD/EMTDC® software. The results show that the proposed reactive power management method can improve the dynamic voltage responses in both steady-state and transient conditions when the distribution system has the high penetration of renewables.
Highlights
To accommodate the large amount of distributed energy resources (DERs), the new transmission system of 70 kV is under construction in South Korea
The instances when the power generation from DERs suddenly stops due to the rapid weather change are focused. This is because the re-connection of new DERs to the distribution system does not cause the serious voltage variations by their ramp-rate control, which limits the rate of change in the magnitude of active power
When several DERs are disconnected at the same time, the simulation results are given to validate the proposed reactive power management method which minimizes the voltage variation
Summary
To accommodate the large amount of distributed energy resources (DERs), the new transmission system of 70 kV is under construction in South Korea. The Q(V) droop control has been widely used for the reactive power management of DERs [6,7,8,9]. A new method to minimize the voltage variation is proposed when several DERs in the practical distribution system are simultaneously disconnected. The proposed method can assign the optimal reactive powers to all DERs by using the voltage sensitivity matrix. It is cost effective in that the high-bandwidth communication is not required to deal with the power fluctuations from DERs. note that the generations and load variations can be measurable by the distribution energy management system (DEMS). This paper focuses on systematically assigning the reactive power set-points to pre-installed DERs without a design of additional controllers. The proposed reactive power management method based on the voltage sensitivity analysis is explained.
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