• Energy Research

Energy storage systems (ESS) are widely used in active distribution networks (ADN) to smoothen the drastic fluctuation of renewable energy sources (RES). In order to enhance the scalability and flexibility of ESS, a virtual energy storage system (VESS), which is composed of battery energy storage system (BESS), RES as well as flexible loads (FL), is developed in this paper to realize the functionalities of ESS in more cost-effective way in ADN. Aiming at achieving voltage regulation, dynamic pricing strategies based on system voltage condition are designed for VESS. A distributed real-time power management model containing dynamic pricing strategies is proposed to accomplish the voltage regulation and economic power sharing in VESS. Moreover, a set of distributed algorithms, over time-varying unbalanced directed networks, are designed for dynamic pricing strategies and optimal power management model. Furthermore, the convergence property, optimality and system voltage stability are explained by detailed mathematical analysis. Three various case studies which were ran on a real time digital simulator (OPAL-RT OP5600) were designed to validate the effectiveness of the strategy. Finally, simulation results show that the economic power dispatch and voltage regulation are achieved among VESS simultaneously, even in the presence of time-varying directed and unbalanced communication networks.

Abstract The growing penetration of photovoltaic (PV) sources accommodated in Active Distribution Network (ADN) brings various severe voltage limits violation problems. This paper provides power management strategy for PV inverters in order to achieve power sharing as well as voltage regulation by dispatching PV active and reactive power. The proposed power management method can operate in a fully distributed manner where each unit measures local voltage information and communicates with neighboring units via time-varying directed communication networks to make its decisions, minimize the PV operation costs, drive system voltage into an acceptable range and always meet the active and reactive capacity constraints. The effectiveness and performance of the proposed method are validated by running different simulation scenarios on a real-time simulator (OPAL-RT).

This paper provides a distributed control strategy for battery energy storage systems (BESS) based on multi-agent system. The proposed control laws can guarantee that the state of charge (SoC) is synchronized, and BESS active power can be shared proportionally. Moreover, the heterogeneous characteristics of BESS are considered in modeling BESS and designing control laws, while they are not carefully considered in the existed literature. Besides, the proposed control laws are robust to the changing communication topologies and link broken since they can be applied over the time-varying directed unbalanced communication networks. Simulation studies, which are carried out on matlab/simulink, validate the effectiveness of the control strategy and laws.

Abstract Virtual energy storage systems (VESS) are important new equipment for distribution networks, consisting of battery energy storage systems (BESS) or flexible loads (FL), that improve peak shaving, frequency regulation and energy management. This paper focuses on power management and real-time control for multiple virtual energy storage systems (MVESS). To enhance renewable energy penetration using competing objective functions in MVESS, a distributed multi-objective power management scheme is proposed, where a Nash Bargaining Solution (NBS) is used to find optimal, unique and fair solutions. A distributed integral optimization algorithm, with fast convergence, is designed to solve the NBS-based problem, containing equality and inequality constraints. Distributed real time control for MVESS is proposed to increase system efficiency and control State of Energy (SoE) and proportional power sharing between BESS and FL. The mathematical analysis guarantees optimality and convergence for the two proposed algorithms. To evaluate the performance of the strategy, three different case studies were executed on a real time digital simulator (OPAL-RT OP5600). Finally, the simulation results demonstrate that system power was shared optimally between VESS, with proportional power sharing among BESS and FL and SoE synchronization.