A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems <s> B. Central Control Concepts <s> This paper describes a coordinated control scheme of battery energy storage system (BESS) and distributed generations (DGs) for electric distribution grid operation. The BESS is designed to stabilize frequency and voltages as a primary control after the electric distribution system enters into the islanding operation mode, while the centralized joint load frequency control (CJLFC) utilizing DGs handles the secondary frequency regulation. The BESS with the associated controllers has been modelled in Real-time digital simulator (RTDS) in order to identify the improvement of the frequency and voltage response. The modified IEEE 9-bus system, which is comprised of several DG units, wind power plant and the BESS, has been employed to illustrate the performance of the proposed coordinated flexible control scheme using RTDS in order to verify its practical efficacy. <s> BIB001 </s> A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems <s> B. Central Control Concepts <s> The widespread installation of distributed generation systems is crucial for making optimal use of renewable energy. However, local distribution networks face voltage fluctuation problems if numerous photovoltaic (PV) systems are connected. Recently, energy storage systems that can be installed at commercial customers have been developed. This paper proposes a concept that solves the voltage fluctuation problem in distribution networks with high penetration of PV systems by using customer-side energy storage systems. The distribution network operator (DNO) is allowed to control the output of the energy storage systems of customers during a specific time period in exchange for a subsidy covering a portion of the initial cost of the storage system. The cost effectiveness of the cooperative operation for both customer and DNO is discussed by numerical simulations based on minute-by-minute solar irradiation data. Our results have clarified the possibilities of making voltage management more economical in distribution networks. <s> BIB002 </s> A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems <s> B. Central Control Concepts <s> In this paper, a coordinated voltage control scheme utilizing electrical energy storage (EES) is presented, for future distribution networks with large, clustered distributions of low carbon technologies (LCTs) in terms of both feeder and phase location. The benefits of the EES integrated scheme over conventional voltage control schemes are demonstrated by realizing a set of network scenarios on a case study network both in simulation and in network in the loop (NIL) emulation at a smart grid laboratory facility. The case study uses a rigorously validated model of an actual GB distribution network with multiple EES installations. It was found that the EES integrated voltage control scheme is able to provide increased capability over conventional voltage control schemes and increase the value of EES to network operation. <s> BIB003
In contrast to autonomous control, central approaches need a functioning control unit and a communication network. Attached components do not make decisions by their own. An algorithm where storages provide voltage control with OLTC simultaneously on the low-and medium-voltage levels is shown in BIB003 . Single actions are rated based on their costs and impact with offline load flow simulations. A central controller optimizes component behavior based on measurements. The authors in BIB001 discussed a central control algorithm for voltage and frequency control for microgrids based on droop control. The battery storage system is the primary control unit for maintaining both voltage and frequency. It is only active when the microgrid changes to islanding mode. When in islanding mode, the battery ESS (BESS) is coordinated with local DERs over a central control unit. Sugihara et al. BIB002 proposed a central control approach where the distribution system operator (DSO) has direct control access to distributed storage systems at customer sides. Access is granted in exchange of a subsidy for the storage system. The described approach takes advantage of the reactive power compensation abilities of the storage converter. Voltage control facilitated by active power control is not included in the proposed approach. Like other control approaches, the decision foundation is based on characterization of the network via load flow calculations. The authors showed that the described approach allows the DSO to maintain acceptable voltage level on a cheaper base than with other measures. The paradigm of the distributed versus centralized control approaches is in the focus of attention, but the trend toward distribution is clearly identifiable. This is the only way out in such complex systems.