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Economic operation is a major concern for microgrids (MGs). System operation cost is optimized when the incremental costs (ICs) of all distributed generators (DGs) reach equality. Conventionally, economic dispatch of DGs is solved by centralized control with optimization algorithms or distributed control with consensus algorithms. To improve the reliability, scalability, and economy of MGs, a fully decentralized economic power sharing strategy is proposed in this paper. As frequency is a global state in ac MG and dc bus voltage serves as a natural indicator in dc MG, a frequency-IC droop scheme is proposed for ac MG, a voltage-IC droop scheme is proposed for dc MG, and a normalization scheme is proposed for hybrid ac/dc MG. By using the proposed technique, ICs of DGs reach equality with the convergence of the system global indicator (frequency or dc bus voltage). Then power sharing of each DG is automatically achieved based on its relevant IC function and the total operating cost can be optimized without any communication or central controllers. The proposed approach is implemented in an ac MG, a dc MG, and a hybrid ac/dc MG in MATLAB/Simulink to verify its effectiveness. [ABSTRACT FROM AUTHOR]

In dc microgrid, energy storage system (ESS) plays a crucial role to provide short-or-long term and high-quality electric energy. The different control strategies for bidirectional dc-dc converter (BDC) of ESS in grid-tied and islanded modes pose challenges to the coordination control of the dc microgrid. This paper proposes an autonomous control scheme for the BDC in dc microgrid. The proposed control scheme is based on $V^2-P$ droop control and unifies bus voltage regulation and power regulation in a single control structure. Thus, global smooth transition between various operation modes can be achieved without any control strategy changes, which avoids various mode switch detection mechanisms and improves system stability. Furthermore, the proposed control scheme is fully decentralized which reduces the reliance on communication, and enhances the reliability of the microgrid. On the other hand, $V^2-P$ droop approach eliminates the negative effect of widespread constant power loads (CPLs) in dc microgrid. The stability of the proposed control method is illustrated, and the design guideline of some critical control gains is addressed. Finally, the effectiveness of the proposed control scheme is validated by the real-time hardware-in-loop (HIL) platform. [ABSTRACT FROM AUTHOR]