Today, conventional power systems are evolving to modern smart grids, where interconnected microgrids may dominate the distribution system with high penetration of renewable energy and energy storage systems. The hybrid AC/DC systems with DC and AC sources/loads are considered to be the most possible future distribution or even transmission structures. For such hybrid AC/DC microgrids, power management strategies are one of the most critical operation aspects. This paper presents an overview of power management strategies for a hybrid AC/DC microgrid system, which includes different system structures (AC-coupled, DC-coupled, and AC-DC-coupled hybrid microgrids), different operation modes, a thorough study of various power management and control schemes in both steady state and transient conditions, and examples of power management and control strategies. Finally, discussion and recommendations of power management strategies for the further research are presented. Index Terms-AC-coupled hybrid microgrid, AC-DC-coupled hybrid microgrid, Control strategies, DC-coupled hybrid microgrid, Energy management, Hybrid AC/DC microgrid, Power management schemes. I. 0885-8993 (c)

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Today, conventional power systems are evolving to smart grids, which encompass clusters of AC/DC microgrids, interfaced through power electronics converters. In such systems, increasing penetration of the power electronics-based distributed generations, energy storages, and modern loads provide a great opportunity for power quality control. In this paper, an overview of the power quality control of smart hybrid AC/DC microgrids is presented. Different types of power quality issues are studied first, with consideration of real-world hybrid microgrid examples, including data centers, electric railway systems, and electric vehicles charging stations. It shows that compared to traditional centralized power quality compensations, smart interfacing power converters from distributed generations, energy storages, and loads, and the AC and DC subgrids interfacing converters are promising candidates for power quality control. To realize the smart interfacing converters' power quality control, both primary converters control and secondary system coordination are required. In this paper, a thorough review of the primary control of interfacing converters to integrate the power quality compensation are presented, with a focus on the hybrid AC/DC microgrid harmonics compensation and unbalance compensation. For multiple interfacing converters, the secondary control with system-level coordination and optimization for harmonics and unbalance compensation (considering both unbalance and harmonics in single-phase and three-phase systems) are also presented. Challenges like low switching frequency of interfacing converters, parallel interfacing converters operation, and interfacing converters communications are discussed, and typical solutions for primary and secondary controls to deal with them are presented. The paper also includes rich case study results.INDEX TERMS Harmonic compensation, hybrid AC/DC microgrid, interfacing power electronics converters, power quality, primary and secondary control, smart converters, smart grids, unbalance compensation.

Microgrids are being developed as a building block for future smart grid system. Key issues for the control and operation of microgrid include integration technologies and energy management schemes. This paper presents an overview of grid integration and energy management strategies of microgrids. It covers a review of power electronics interface topologies for different types of distributed generation (DG) units in a microgrid, a discussion of energy management strategies, as well as the DG interfacing converter control schemes. Considering the intermittent nature of many renewable energy based DG units, the ancillary services of DGs using the available interfacing converter rating are also discussed in the paper.