Abstract-In this paper, a multilayer control is proposed for inverters able to operate in parallel without intercommunications. The first layer control is an improved droop method by introducing power proportional terms into a conventional droop scheme, which let both the active and reactive power to be shared among the modules. The second layer is designed to compensate the voltage droop caused by the droop control mentioned and improve the load regulation performance of the system. The third layer is a quasi-synchronization control aiming to adjust roughly and ensure the phase deviation among the inverters within a limited margin with the help of the phase signal sensed from the shared ac output power bus. The operational principle and implementation are analyzed with design consideration given in detail. Experimental results with a prototype system of two 35kVA inverters verify the analysis and design.

Anapole mode is excited by the destructive interference between the toroidal-and electric-dipole moments, resulting in a highquality (Q) factor. In this paper, we designed a high-Q-factor metamaterial that shows anapole behaviors in the terahertz region. Through the introduction of graphene, the destructive interference condition is disturbed and tunability can be realized. This pattern reflects a brilliant tunability performance in which frequency movements above 250 GHz per 0.1 eV can be verified. Ingenious adjustment by the position of graphene offers the possibility of diversified tuning capabilities. Such a tunable terahertz metamaterial has great potential in reconfigurable sensors.

Inspired by the development of terahertz (THz) technology, the demand for THz sensors with high quality and high sensitivity is significantly increasing. In this study, one-dimensional metallic metamaterials based on cavity mode resonance are proposed for sensing applications in the THz regime. Owing to the strong energy concentration in the cavity, metamaterials with a high quality factor were obtained. Thus, the presented device not only achieved narrowband selective absorption but also exhibited excellent refractive index sensing with high sensitivity, figure of merit, and quality factor. The physical mechanism was verified by comparing the simulation results with that of the coupled mode theory. The polarization dependence of absorption and dual-band sensing, which can be actively tuned by the broken symmetry between two adjacent units, were also discussed. Consequently, this study may open up new avenues for the development of biosensing and imaging applications.

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