The integration of distributed energy resources (DERs) with conventional systems emerges as an intelligent solution for providing uninterrupted and secure power even at times of high load demand. Better load management with a mature fault handling mechanism makes AC a viable option which has an efficiency of 78.24%. In contrast with less power loss and slightly better efficiency of 84.6%, DC microgrid is a reliable option in a low power environment. In order to accommodate all operating conditions and load types, a hybrid system can be designed with a theoretical efficiency of more than 90%. Bidirectional power flows, low inertia, the transition between different modes of operations are the challenges for the protection of alternating current (AC) and direct current (DC) microgrid systems. Power balance fluctuation, absence of zero‐crossing currents, selection of suitable grounding, and coordination between different rating devices restrict the hybrid system to achieve the said efficiency constantly. This paper reviews in detail of existing protection along with grid‐connected algorithms for both modes of operation. Finally, the limitation, major hurdles, and future course of action for a reliable, efficient, and secure hybrid grid system are figured out.

中文翻译：

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分布式发电AC / DC混合微电网保护：对问题，策略和未来方向的严格审查

分布式能源（DER）与常规系统的集成作为一种智能解决方案出现，即使在高负载需求时也可提供不间断且安全的电源。具有成熟的故障处理机制的更好的负载管理使交流电成为可行的选择，效率为78.24％。与更低的功率损耗和84.6％的更高效率相比，直流微电网在低功率环境中是可靠的选择。为了适应所有工作条件和负载类型，可以将混合系统设计成理论效率超过90％。双向潮流，低惯性，不同操作模式之间的转换是保护交流（AC）和直流（DC）微电网系统的挑战。功率平衡波动 由于没有过零电流，没有选择合适的接地以及不同额定设备之间的配合，限制了混合动力系统不断地实现上述效率。本文详细介绍了两种操作模式下的现有保护以及并网算法。最后，找出了可靠，高效和安全的混合电网系统的局限性，主要障碍和未来的行动方针。