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Distinct characteristics of transmission and distribution power grids typically necessitate different control algorithms, especially at the primary control level where quick responses are required. Accordingly, various droop control schemes have been developed due to specific types of power grid impedances. Therefore, controllers at higher levels often have to be redesigned whenever a different power grid is considered, hence, incurring higher cost and effort. As a way to overcome that problem, in this work, a unified secondary controller using distributed control theory is designed for different droop schemes associated with distributed battery storage in different grid conditions. The control design follows the consensus theory, originally designed for multi-agent systems, to control the frequency and voltage at the point of common coupling (PCC), synchronize energy levels, and proportionally share active and reactive powers of battery storage systems. A sufficient condition for the upper bound of communication delays between storage systems is derived to ensure system stability. Several scenarios are studied using a modified IEEE 118-bus benchmark to support the theoretical results of the proposed approach. [ABSTRACT FROM AUTHOR]

Energy, building, and water networks are three interlinked critical infrastructures that need to be operated cooperatively to maximize the smart grid’s economic benefits. In this paper, a mixed-integer linear programming (MILP) formulation is proposed to approach the economic dispatch (ED) problem for smart grids embedded with interdependent water and energy networks. Energy management of various building applications is considered by intelligently controlling the indoor temperature during occupied and unoccupied hours. To optimize the demand of water distribution system, pump’s nonlinear scheduling and hydraulic factors and daily water usage of buildings are added to the proposed model. Piecewise linear approximation of univariate and bivariate nonlinear functions is used to convert the nonlinear problem to an MILP formulation. Several case studies were conducted to examine the impact of indoor temperature settings of the buildings, speed of pumps, battery efficiency, and end of day (EoD) battery and tank constraints on economic dispatch of the microgrid system. [ABSTRACT FROM AUTHOR]

Hybrid storage system composed of battery energy storage systems (BESSs) and supercapacitors is a promising solution to mitigate the high frequency power fluctuations of pulsed power loads (PPLs) in medium voltage DC (MVDC) shipboard power systems. Due to the presence of multiple storage units, a power sharing algorithm needs to be considered within the energy management system (EMS) in the shipboard power system. In this paper, an optimal power flow problem is formulated for MVDC shipboard power systems with hybrid energy storage systems. Battery energy storage systems (BESSs) and conventional generation units are enhanced with virtual resistive droop controllers to share the steady-state power fluctuations. Supercapacitors are enhanced with virtual capacitive droop controllers to share the high frequency fluctuations in the load. The optimal flow accounts for minimizing the operational cost of the generation units in the shipboard power system considering the constraints of network, load balance, voltage profile, and power/energy limits. Second-order cone programming (SOCP) relaxation is used to approximate the nonconvexity of the optimal flow formulation and necessary conditions for global optimality of the solution are discussed. Results confirm the effectiveness of the proposed formulation in load support and managing the energy between storage units. [ABSTRACT FROM AUTHOR]

This paper proposes a distributed control architecture for battery energy storage systems (BESSs) based on multi-agent system framework. The active/reactive power sharing, the frequency/voltage, and the energy of BESSs are synchronized by exchanging local information with a few other neighboring BESSs. Two consensus algorithms namely leaderless and leader–follower are proposed. The proposed control architecture offers unique features. First, the heterogeneous nature of BESSs is explicitly taken into account in BESS models and consensus designs, while it is usually ignored in the literature. Second, the proposed designs bring the plug-and-play capability to the smart grid system by operating in both islanded and grid-connected modes. Next, the nominal frequencies and nominal voltage magnitudes of BESSs are used in the consensus design instead of their frequencies and voltage magnitudes. This makes the proposed structure much easier to be implemented in the real power grids. Lastly, an additional control input is designed to synchronize the energy levels of BESSs directly, whereas the energy levels of BESSs are synchronized indirectly through their powers in other existing research. Time-domain simulations on a modified IEEE 57-bus power system are then carried out to validate the proposed control structure and the consensus designs. [ABSTRACT FROM AUTHOR]

In this paper, consensus integral control is applied for energy storage in microgrids to synchronize the state-of-charge (SoC) and power levels of batteries with limited information exchange. Both local information (SoC and power level) and neighbors’ information (SoC and power level) will be fed into an integral control installed at every battery converter. The design is based on consensus control and takes into consideration of real-world battery coordination requirements, e.g., all batteries should work in the same charging or discharging mode. Compared with the consensus control in the existing literature for voltage consensus or battery SoC/power consensus, this paper offers a simple design. The major assumption of this paper is that each converter should possess an integral control. This assumption is valid since indeed integral controls exist if converters are equipped with secondary frequency control. The designed consensus control is validated by simulations on 14-bus microgrid and IEEE 57-bus power system. Simulation results demonstrate the effectiveness of the consensus integral control for variety modes of operation: 1) charging; 2) discharging; and 3) load variation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel distributed control architecture for synchronization of the active/reactive power sharing, energy levels, frequency/voltage of distributed battery energy storage systems (BESSs) using inter-BESS communications. The local information of each BESS is exchanged with a few other neighboring BESSs to achieve a consensus. The consensus speed is significantly improved by introducing an inner control loop for energy levels. The droop frequency/voltage control is also added to regulate the active/reactive power sharing and the frequency/voltage of BESSs. Furthermore, self delays and communication delays are explicitly considered in the design. As a result, the derived consensus algorithms are fully distributed with fast consensus speed in both contexts of nonexistence and existence of time delays, which have not been addressed in the existing research for BESSs. To validate the design, several simulation case studies are carried out. [ABSTRACT FROM AUTHOR]