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In the microgrid, virtual synchronous generator technology can significantly enhance the anti-interference characteristics of the system frequency and bus voltage, as well as solve the problems of insufficient damping and low inertia. However, the system frequency and active power oscillation caused by power fluctuations and grid faults threaten the stable operation of the grid seriously. Therefore, for an alternating current (AC) microgrid multi-virtual synchronous generator (VSG) parallel system, an improved virtual synchronous generator control algorithm based on a fuzzy inference system is proposed, which adjusts the values of virtual inertia and damping coefficient dynamically through fuzzy logic rules to realize the coordinated control of the two. The enhanced VSG algorithm described in this research has a substantial influence on power-frequency oscillation suppression, decreases active power and frequency overshoot, shortens the adjustment time, and improves system frequency stability active power, according to simulation and experimental findings. Published version This research was supported in part by the International Science and Technology Cooperation Project of Jilin Province Science and Technology Department, grant number 20210402080GH, the author hereby expresses his gratitude to the abovementioned institution for their support.

Acupuncture is an emerging alternative therapy that has been beneficial for the pain of osteoarthritis (OA). However, the underlying mechanism of protective effect remains unclear. MCP1/CCR2 axis can be stimulated in various periods of OA, and we hypothesize that acupuncture may treat OA by regulating the MCP1/CCR2 axis. This study aimed to explore the effect of acupuncture at points ST35 and ST36 on the effects of hyperalgesia and cartilage in OA rats including the expression of chemokines, nerve growth factor (NGF), and inflammatory-related proteins. OA was induced in male Sprague–Dawley rats by anterior cruciate ligament transection at the right knee. The first acupuncture intervention was performed on the seventh day after surgery and once a day for seven weeks. The knee-pain-related behaviors, histology, and related protein were examined in this study. We have found that electroacupuncture at ST35 and ST36 can significantly alleviate the hyperalgesia and cartilage degeneration as well as reducing nerve sprouting in OA knee joint. Moreover, acupuncture treatment may inhibit the MCP1/CCR2 axis as well as down-regulate inflaming factor and NGF in cartilage and synovial tissue. The data presented here indicate that acupuncture exerts a protective effect against hyperalgesia and cartilage degeneration, and the mechanism might involve in chemokines and NGF pathway.

Power electronics converters have been widely used in aerospace system, DC transmission, distributed energy, smart grid and so forth, and the reliability of power electronics converters has been a hotspot in academia and industry. It is of great significance to carry out power electronics converters open-circuit faults monitoring and intelligent fault diagnosis to avoid secondary faults, reduce time and cost of operation and maintenance, and improve the reliability of power electronics system. Firstly, the faults features of power electronic converters are analyzed and summarized. Secondly, some AI-based fault diagnosis methods and application examples in power electronics converters are reviewed, and a fault diagnosis method based on the combination of random forests and transient fault features is proposed for three-phase power electronics converters. Finally, the future research challenges and directions of AI-based fault diagnosis methods are pointed out., Comment: Power System Technology

Additional file 1: Table S1. NMR Data for epicoccamide A (1). Table S2. Comparison of the signature residues for amino acid selection by adenylation (A) domains of fungal PKS-NRPS (NRPS). Figure S1. The 1H NMR spectrum of compound 1. Figure S2. The 13C NMR spectrum of compound 1. Figure S3. The 1H-1H COSY spectrum of compound 1 (in DMSO). Figure S4. The HSQC spectrum of compound 1 (in DMSO). Figure S5. The HMBC spectrum of compound 1 (in DMSO). Figure S6. HRESIMS spectrum of compound 1. Figure S7. ESI MS/MS (-) spectrum of compound 1.

The high penetration of renewable energy in power systems significantly increases the difficulty of system modelling. Adequate attention should be paid to the impact of the correlation between renewable energy sources and voltage stability. In this paper, a global sensitivity analysis method is proposed to analyse the sensitivity of correlated renewable energy generation to voltage stability. The established model fully considers the uncertainty of wind speed and solar irradiance. Moreover, the simplified local voltage stability index is used to evaluate voltage stability. The global sensitivity analysis method is used to identify the sensitivity of random factors. In addition, the Monte Carlo method is proposed to calculate Pearson correlation coefficients in different distribution spaces. The Nataf inverse transform is used to sample correlated renewable energy. Finally, the global sensitivity index of renewable energy generations is obtained. Numerical results on the modified IEEE 30-bus system and modified IEEE 118-bus system show that with the enhancement of correlation between renewable energy sources, the sensitivity of renewable energy generations to voltage stability is also increasing.

Background Knee osteoarthritis (KOA) is a common disabling condition and a heavy financial burden to the society. Platelet-rich plasma (PRP) is considered to be an effective method in the repair and regeneration of cartilage and alleviate pain in KOA. But the utilising of PRP to treat KOA in clinical has shown variable results from many studies. The objective of this protocol is to determine the efficacy of PRP in pain control and cartilage repair in KOA animal models. Method We will search the following three electronic databases: MEDLINE, EMBASE and Web of Science. The primary outcome will include the histological score of cartilage and pain score. The secondary outcomes will be the behavioural assessments and cartilage thickness. SYRCLE's risk of bias tool will be used to assessment the risk of bias of including studies. The standardized mean difference and 95% confidence interval will be used to calculate the effect of PRP treatment. The I2 inconsistency values will be used to calculated the heterogeneity between studies. Results The results of this paper will be submitted to a peer-reviewed journal for publication. Conclusion This research will determine the efficacy of PRP of the treatment of knee osteoarthritis model. Prospero registration number CRD42020181589.

Summary Under frequency load shedding (UFLS) is an effective remedy against power system frequency collapses. An optimal approach for designing UFLS schemes of regional power system is presented in this paper. An improved multigenerator frequency response (IMFR) model that incorporates UFLS schemes is built to accurately and quickly evaluate system frequency after generator and load imbalance. Unlike the conventional system frequency response model, IMFR involves a spinning reserve, different types of governors, the static load model, and network influence. The representative operating and contingencies for designing UFLS schemes are selected with the use of IMFR. The optimization object function is defined for minimizing the amount of total load shed and considering UFLS design and performance criteria. Then, the optimal UFLS scheme is designed through IMFR and adaptive simulated annealing algorithm. Finally, the approach is applied to an actual regional power system in China. The effectiveness of the optimal UFLS scheme is investigated through a simulation.

Real power generation dispatch and scheduling become a kind of multi-objective decision problems when fuel costs and emission are needed to be minimized simultaneously. These objectives are usually conflicting. Based on the concept of ideal point, generation dispatch model and generation scheduling model with fuel and emission minimized simultaneously are formulated. It is accomplished by constructing a hyperspace. In the hyperspace, the dimension number of which is that of the goals to be optimized, different coordinates of a space point are of such realistic meanings as costs or emission quantities. Not only the non-commensurable and conflicting problems of different goals could be dealt with, the conclusions also could give us useful insights into the multi-objective real power optimization problems by analyzing the necessary conditions of these models are discussed. These conditions are also helpful when solving these ideal point method models.

At the present time, the country has carried out the measure of energy-saving power scheduling. The main object of this measure is to increase the efficiency and to reduce pollution which is important to the power stations. This paper calculated three kinds of equivalent price coefficient of energy and environment in the case of the lowest bidding price or the least energy or the most minimum pollution to the environment. In this way, the multi-objective optimal problem with different physical units was reformulated into a new single-objective optimal problem. The numerical result shows that only considering economic indicators is unable to meet the development of the market. More considering on saving energy, lower energy consumption and reducing pollutants discharge must be given to put the power suppliers in a favorable position in the future market.

This paper presents a new classifier based on Fuzzy Technique of Order Preference by Sunilarity to Ideal Solution (TOPSIS) for power transformer fault diagnosis in dealing with the dissolved gas analysis(DGA) problem, which is treated as the collision between lowering complex process of the analysis and increasing quantity of monitoring informations. Two methods are employed to ameliorate the diagnosis condition. Firstly, the essential concept of Fuzzy Set using semantic variables is introduced. And this classification approach is then combined with the TOPSIS considering the efficiency in managing imperfect and incorrect datas, and the multiple attribute decision matrix is deduced by fuzzy mapping. Secondly, the vector interval is calculated, which fixes the relative similarity of the possible fault types on the evidence of various gas ratios. Finally, contrasted with IEC Three-ratio method, the new method has been proved rapid and exact in judging the operation states, and therefore the safety, stability and economy of transformer are improved.

An autonomous flight control law applicable to full-envelope was designed in this manuscript for a small-scale unmanned aerial vehicle (UAV) helicopter to fly autonomously. The UAV helicopter was constructed based on a radio-controlled hobby helicopter by assembling an avionic system. The autonomous flight control law applicable to full-envelope was designed using a decentralized design methodology incorporating a newly developed nonlinear control techniques as well as dynamic inversion. The designed autonomous flight control law was implemented and verified in flight tests with the UAV helicopter. The flight test results demonstrate that the designed autonomous flight control law successfully drives the small-scale UAV helicopter to fly autonomously. The scheme of the autonomous flight control is applicable to flight control design of other UAVs.

This paper presents a flexible middle and long term forecasting for the representative daily load curve using the support vector machines. Considering that characteristic parameters of the representative daily load depend on a number of complex factors that have nonlinear characteristics, with the method of SVM, the model of characteristic parameters is established. It gives relatively accurate characteristic parameters which are beneficial for analyzing the variety of loads in the future and providing relatively accurate variables for traditional load curve prediction. Considering that the characteristic parameters have great influence on the precision of the representative daily load curve using the traditional method, with the representative daily load sequence of every hour, the model based on SVM can be established. From the testing result of this forecasting method with the actual data of a power grid in China, its precision has been verified. (5 pages)

This paper proposes a method to calculate the transient energy in electrical power networks on the basis of the topological energy function. For a given unstable mode, a novel technique to evaluate cutsets that critically affect the transient stability of the power system is developed according to the change of first swing transient energy of cutsets during the post-fault period. The network's parameter adjustment and control are discussed. Examples are presented by simulation on a 6-generator, 24-bus power system.

In this paper, the novel quantitative assessment method based on local network dynamic measurements has been developed. Based on the topological energy function given by Bergen and Hill, a new style of stability criterion is suggested which is based on line measurement. The stability indices for lines, cutsets and power system according to features of transient energy in the lines is given, which not only provide reliable and accurate assessment of the transient stability of the power system, but can be used to assess the effect of lines and cutsets on the transient stability and identify the weak transmission segment. The examples are presented by simulation on the IEEE-39 buses test system.