VSG Control Strategy Incorporating Voltage Inertia and Virtual Impedance for Microgrids

Virtual synchronous generator (VSG) control lacks voltage inertia and powerful decoupling capabilities. The voltage of the distributed generator (DG) unit controlled by the VSG will be easily affected by power fluctuations and high-frequency noise, and the DG coupling usually makes the VSG control effect unsatisfactory. In order to effectively reduce power fluctuations, the influence of high-frequency noise on voltage, the influence of coupling on the power regulation, and effectively improve the economy of the economic system, the improved VSG control that combines voltage inertia and virtual impedance is proposed in this paper. The second-order inertia in the proposed VSG control strategy can minimize the voltage change rate and filter high-frequency noise from the excitation and virtual impedance. The virtual impedance in the proposed VSG control strategy can simulate the actual impedance to change the line characteristics, so the coupling of the DG unit can be reduced. Experimental results based on the microgrid platform prove the feasibility of improving the VSG control

Synthesis of a MnO2/Fe3O4/diatomite nanocomposite as an efficient heterogeneous Fenton-like catalyst for methylene blue degradation

Heterogeneous Fenton-like catalysts with the activation of peroxymonosulfate (PMS), which offer the advantages of fast reaction rate, wide functional pH range and cost efficiency, have attracted great interest in wastewater treatment. In this study, a novel magnetic MnO2/Fe3O4/diatomite nanocomposite is synthesized and then used as heterogeneous Fenton-like catalyst to degrade the organic pollutant methylene blue (MB) with the activation of PMS. The characterization results show that the Fe3O4 nanoparticles and nanoflower-like MnO2 are evenly distributed layer-by-layer on the surface of diatomite, which can be readily magnetically separated from the solution. The as-prepared catalyst, compared with other Fenton-like catalysts, shows a superb MB degradation rate of nearly 100% in 45 min in the pH range of 4 to 8 and temperature range of 25 to 55 °C. Moreover, the nanocomposite shows a good mineralization rate of about 60% in 60 min and great recyclability with a recycle efficiency of 86.78% after five runs for MB. The probable mechanism of this catalytic system is also proposed as a synergistic effect between MnO2 and Fe3O4

Orthogeriatric co-managements lower early mortality in long-lived elderly hip fracture: a post-hoc analysis of a prospective study

Abstract Objective To evaluate the clinical effectiveness of orthogeriatric co-management care in long-lived elderly hip fracture patients (age ≥ 90). Methods Secondary analysis was conducted in long-lived hip fracture patients between 2018 to 2019 in 6 hospitals in Beijing, China. Patients were divided into the orthogeriatric co-management group (CM group) and traditional consultation mode group (TC group) depending on the management mode. With 30-day mortality as the primary outcome, multivariate regression analyses were performed after adjusting for potential covariates. 30-day mobility and quality of life were compared between groups. Results A total of 233 patients were included, 223 of whom completed follow-up (125 in CM group, 98 in TC group). The average age was 92.4 ± 2.5 years old (range 90–102). The 30-day mortality in CM group was significantly lower than that in TC group after adjustments for (2.4% vs. 10.2%; OR = 0.231; 95% CI 0.059 ~ 0.896; P = 0.034). The proportion of patients undergoing surgery and surgery performed within 48 h also favored the CM group (97.6% vs. 85.7%, P = 0.002; 74.4% vs. 24.5%, P  0.05). Conclusions For long-lived elderly hip fracture patients, orthogeriatric co-management care lowered early mortality, improved early mobility and compared with the traditional consultation mode