Search NASA⌕ Search

Engineering topics

Yu, Hui

Publications and source records attributed to Yu, Hui.

Privacy-Preserving Robust Consensus for Distributed Microgrid Control Applications

Consensus-based distributed control has been proposed for coordinating distributed energy resources (DERs) in microgrids (MGs). As one key component, distributed average observers are used to estimate the average of a group of reference signals (e.g., voltage, current, or power). State-of-the-art distributed average observers could lead to loss of privacy due to information exchange on the communication channels. The DERs' reference signals, which contain private information, could be inferred by an eavesdropper. In this article, a privacy-preserving distributed average observer is proposed that is based on robust consensus and uses the state decomposition method to preserve privacy. Compared to the existing methods, the proposed observer does not require the knowledge of the reference signal's derivative and gives accurate and smooth estimation, and is thus applicable for MG distributed control applications. A detailed analysis regarding the convergence and privacy properties of the proposed observer is presented. Here, the proposed observer is implemented on hardware controllers and validated in the context of distributed MG control applications through hardware-in-the-loop (HIL) tests.

24 POWER TRANSMISSION AND DISTRIBUTION↗

A Novel Grid-forming Voltage Control Strategy for Supplying Unbalanced Microgrid Loads Using Inverter-based Resources

This paper presents a novel grid-forming voltage control strategy for a battery energy storage system to maintain balanced three-phase output voltages when serving unbalanced loads. A stationary reference frame (αβ) based control scheme is proposed to regulate positive-sequence and negative-sequence voltages. Compared with the conventional rotating reference frame (dq) based control scheme, the proposed scheme shows better dynamic performance. Then, we analyze the system zero-sequence network and propose adding a grounding transformer to the Y/Yg connected output transformer to further reduce the voltage unbalance at the point of common coupling. The simulation results demonstrate the effective performance of the proposed voltage control scheme. Based on the results, the power-voltage unbalance curve is derived for different output transformer configurations to establish the relationship between the power unbalance limit and the voltage unbalance limit for microgrid power scheduling.

Xu, Bei↗

Astragaloside IV improved antioxidative stress capacity and related gene expression of the Keap1‐Nrf2 pathway in grass carp ( Ctenopharyngodon idella ) hepatocytes under heat stress

Abstract This study aims to investigate the protective effects of astragaloside IV (AS‐IV) on the hepatocytes of grass carp ( Ctenopharyngodon idella ) on heat stress. Cultured cells were treated with AS‐IV (0, 50, 100 and 200 μg/ml) at 28°C for 24 h and then exposed to heat stress by increasing the culturing temperature (32 ± 0.5°C) for 6 h. The increased temperatures significantly reduced cell viability and superoxide dismutase (SOD) activity, and increased malondialdehyde (MDA) levels in the 0 μg/ml AS‐IV treatment group at 32°C, but the grass carp hepatocytes treated with 100 and 200 μg/ml AS‐IV had significantly increased cell viability and SOD activity and decreased MDA levels. The mRNA levels of keap1a , keap1b , nrf2 , gsh‐px , cat , cu‐zn sod , mgst1 and il‐6 were significantly lower in the 0 μg/ml AS‐IV treatment group at 32°C, while those of keap1a , nrf2 , gsh‐px , cat , cu‐zn sod , gstp1 , ho‐1 and il‐6 were significantly higher in cells treated with 100 or 200 μg/ml AS‐IV. Our findings indicate that AS‐IV could enhance the antioxidative stress capacity of grass carp hepatocytes under heat stress, and its mechanism may be associated with the activation of the Keap1‐Nrf2 pathway. Thus, these results provide new insights into how to alleviate heat stress in grass carp.

Liu, Hua↗