An enhanced consensus-based distributed secondary control for voltage regulation and proper current sharing in a DC islanded microgrid

A centralized secondary control is utilized in a DC islanded microgrid to fine-tune voltage levels following the implementation of droop control. This is done to avoid conflicts between current allocation and voltage adjustments. However, because it introduces a single point of failure, a distributed secondary control is preferred. This paper introduces a consensus-based secondary distributed control approach to restore critical bus voltages to their nominal values and properly distribute current among converters. The critical bus takes the lead in voltage adjustments, with only connected energy resources contributing to regulation. The microgrid is represented as an undirected graph to facilitate consensus building. Two adjustment terms, δv and δi, are generated to assist in returning voltage to its nominal level and correctly allocating current among energy resources. To enhance consistency and improve controller performance compared to those reported in existing literature, all buses are connected to a leader node. In the event of the failure of all converters except one, voltage can still be effectively restored. MATLAB-Simulink simulations are conducted on two medium-voltage DC (MVDC) microgrids to validate the efficiency of the proposed control method. The results confirmed that the proposed control method can effectively maintain voltage stability and enhance the precise distribution of current among agents by 8%

Investigation on bistability and fabrication of bistable prestressed curved beam

The writers investigated the bistability of bistable prestressed curved beam based on the theory of Euler buckling and the principle of the least energy. The bistability was found to be much affected by the ratio of the initial apex to the thickness of the curved beam. Using a standard silicon process, we fabricated curved beams made of single crystal Si. Voltage was then applied to the fabricated curved beams to generate capacitive electrostatic actuation force. The snap-through was confirmed in the range of 20 to 30 V apply voltage

Fabrication of Bistable Prestressed Curved-Beam

Bistable curved-beams are micro electro mechanical systems (MEMS) that can switch over two stable bending states and maintain these states without consuming power. One of the most attractive applications of these structures is memory devices. A prestressed curved-beam of single crystal Si is fabricated through the sequences of the standard CMOS process using SOI. The theoretical analysis procedure for the bistable operation is established. The miniaturized bistable curved-beam is applied to memory devices

Analysis and Fabrication of Ampere-Force Actuated Bistable Curved Beam

An actuation scheme of bistable curved beam by Ampere force was proposed. Analysis showed that the actuation force distribution on the curved beam by this current-based method can improve the switching force to snap the curved beam lower than the one of the conventional actuation scheme by capacitive electrostatic force. To observe the snap action, vertical snap type SiO2 curved beams were fabricated with Cr deposited on to provide current conductivities. The Cr layer was considered to affect the original bistability characteristics of SiO2 curved beam, which in turn alter the switching force from the theoretical prediction

Residual Stress in Lithium Niobate Film Layer of LNOI/Si Hybrid Wafer Fabricated Using Low-Temperature Bonding Method

This paper focuses on the residual stress in a lithium niobate (LN) film layer of a LN-on-insulator (LNOI)/Si hybrid wafer. This stress originates from a large mismatch between the thermal expansion coefficients of the layers. A modified surface-activated bonding method achieved fabrication of a thin-film LNOI/Si hybrid wafer. This low-temperature bonding method at 100 °C showed a strong bond between the LN and SiO2 layers, which is sufficient to withstand the wafer thinning to a LN thickness of approximately 5 μm using conventional mechanical polishing. Using micro-Raman spectroscopy, the residual stress in the bonded LN film in this trilayered (LN/SiO2/Si) structure was investigated. The measured residual tensile stress in the LN film layer was approximately 155 MPa, which was similar to the value calculated by stress analysis. This study will be useful for the development of various hetero-integrated LN micro-devices, including silicon-based, LNOI-integrated photonic devices

Performance Investigation of Power Inverter Components Submersed in Subcooled Liquid Nitrogen for Electric Aircraft

Investigating the performance of power electronics devices and thus power inverters at cryogenic temperatures for electric aircraft systems are of great interest. Accordingly, the purpose of this study is to examine the inverter circuit technologies used in cryogenically-cooled electric aircraft applications from three perspectives: inverter topologies, power capabilities, and electromagnetic interference (EMI) that may occur. At a cryogenic temperature, the characteristics of five power semiconductor switches with different technologies (Si MOS, SiC MOS, and GaN HEMT) used in cryogenically-cooled electric aircraft inverters were tested and the results were presented. Furthermore, the low-temperature performance of three types of capacitors commonly used in power electronics inverters was investigated. The research findings provide crucial considerations for the research and development of power inverters cooled by sub-cooled liquid nitrogen for modern electric aircraft