In this paper, a two-layer network and distributed control method is proposed, where there is a top layer communication network over a bottom layer microgrid. The communication network consists of two subgraphs, in which the first is composed of all agents, while the second is only composed of controllable agents. The distributed control laws derived from the first subgraph guarantee the supply-demand balance, while further control laws from the second subgraph reassign the outputs of controllable distributed generators, which ensure active and reactive power are dispatched optimally. However, for reducing the number of edges in the second subgraph, generally a simpler graph instead of a fully connected graph is adopted. In this case, a near-optimal dispatch of active and reactive power can be obtained gradually, only if controllable agents on the second subgraph calculate set points iteratively according to our proposition. Finally, the method is evaluated over seven cases via simulation. The results show that the system performs as desired, even if environmental conditions and load demand fluctuate significantly. In summary, the method can rapidly respond to fluctuations resulting in optimal power sharing.
Battery energy storage system (BESS) is a pivotal component to increase the penetration of renewable generation and to strengthen the stability and reliability of the power system. In this paper, for the purpose of the state of charge (SOC) balancing and reactive power sharing, a multiagent system (MAS)-based distributed control model, which contains a top layer communication network built by agents and a bottom-layer microgrid composed of BESSs, distributed generators (DGs), and Loads, is provided. Next, a systematic method is designed to build the control laws for agents from any given network, where each agent on the top communication network collects the states of BESSs, DGs it connects and exchanges information with its neighboring agents. Moreover, two theorems, which provide guidelines to design distributed control laws for SOC balancing and reactive power sharing between BESSs, are proposed to show the convergent property of the proposed control laws. Furthermore, several simulation cases are employed to validate the effectiveness of the proposed control model when environmental conditions and time-varying load demands are considered. Finally, the simulation results verify the effectiveness of the proposed control model, i.e., the SOC balancing and proportional reactive power sharing are achieved as expected. Furthermore, our approach has the fast convergent speed of SOC balancing of BESSs, compared to the existed method. INDEX TERMS Battery energy storage system (BESS), distributed control, state of charge (SOC) balancing, reactive power sharing, microgrids.
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