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.

This study proposes the practical power management of integrated system with photovoltaic (PV) and energy storage system (ESS) to solve the line congestion and voltage problems in a distribution system while considering the electricity price and state of charge (SOC) of ESS. In addition, the proper power management of PV/ESS integrated system (PEIS) enables to increase the hosting capacity of renewable energies in a distribution system and to maximize the profit of independent power producer (IPP). In this study, the real power management of PEIS of 100 kW is implemented in practice and tested with the actual measurements for 3 days. The results show that the proposed method deals with the line congestion problem effectively and efficiently while increasing the profit of IPP by 11%. In particular, the reactive power control based on the international electrotechnical commission (IEC) standard, IEC 61850-90-7 is applied to the PEIS, and it can successfully mitigate the variations of voltage in a distribution system.

The smart inverter (SI) is an emerging technology, which enables the effective integration of distributed energy resources (DERs). Nevertheless, the operation by the only single SI function is not sufficient to deal with various conditions in a distribution system. In other words, all DERs are required to rapidly update the proper mode of SI functions depending on the system conditions. In this article, we propose the new active distribution management system (ADMS) for photovoltaic (PV)/energy storage system (ESS) integrated system based on the SI functions. It effectively regulates the system voltage, and it solves the line congestion problem in a distribution system by adaptively controlling the mode of SI functions. This method enables DER to effectively regulate its generation without the additional controllers. The effectiveness of the proposed ADMS is verified by several case studies on a practical distribution system in South Korea with the real measurements of generation from PV and load consumption based on the electromagnetic transient program. Also, the PV/ESS integrated system prototype of 100 kW is implemented for the experimental verification of the proposed ADMS.