Electric springs have been used previously in stabilizing mains voltage fluctuation in power grid fed by intermittent renewable energy sources. This paper describes a new three-phase electric spring ...circuit and its new operation in reducing power imbalance in the three-phase power system of a building. Based on government energy use data for tall buildings, the electric loads are classified as critical and noncritical loads so that building energy model can be developed. The proposed electric spring is connected in series with the noncritical loads to form a new generation of smart loads. A control scheme for such smart loads to reduce power imbalance within the building's electric power system has been evaluated initially with an experimental prototype and then in a system simulation study. The results have confirmed the effectiveness of the new three-phase electric springs in reducing power imbalance and voltage fluctuation, making the building loads adaptive to internal load changes and external mains voltage changes.
Electric spring (ES) was originally proposed as a distributed demand-side management (DSM) technology for stabilizing power distribution network in the presence of intermittent power generation ...without using communication. This paper explores the practical use of consensus control for a cluster of ESs through a WiFi communication layer for new functions not previously realized in practice. This approach can be considered as a form of DSM for smart grid technology. A novel consensus control is introduced to enable distributed ES circuits to provide local voltage and system frequency regulations in a microgrid with shared responsibility of active and reactive power compensation. The practical implementation details of consensus control for a cluster of ESs are addressed. New plug-and-play functions of ESs are practically demonstrated for the first time under consensus control. Practical results indicate that droop control (without communication) and consensus control (with communication) are complementary. Under normal condition when the communication network is available, distributed ESs can perform with shared power compensation efforts based on consensus control. If the communication network fails, ESs can revert to perform under droop control.
This paper presents the first hardware implementation and control of an electric spring based on a back-to-back converter configuration. Because of its ability to provide both active and reactive ...power compensation, this back-to-back electric spring (ES-B2B) can substantially extend the operating range of the original version of the electric spring (ES-1) and provide enhanced voltage support and suppression functions. The hardware system and control of the ES-B2B have been successfully developed and tested. The experimental results have confirmed the effectiveness of the ES-B2B in supporting and suppressing the mains voltage. Particularly, the voltage suppression ability of the ES-B2B is superior over that of ES-1. The use of ES-B2B in a simulation study of a weak power grid has also been conducted. The ES-B2B has been found to be highly effective in mitigating voltage fluctuation caused by intermittent renewable power generation.
Microplastics (MPs) are abundant in aquaculture water, including in bioflocs aquaculture systems. Compared with other aquaculture systems, biofloc technology systems have the richest microbes and are ...beneficial to cultivated organisms. Therefore, this study provides a comprehensive assessment of the potential effects of MPs on aquaculture organisms in bioflocs systems. Here, Nile Tilapia (Oreochromis niloticus) were exposed to MPs (polystyrene; 32–40 μm diameter) with 0, 80 items/L (30 μg/L), and 800 items/L (300 μg/L) for 28 days in a bioflocs aquaculture system. The results showed that the MPs generally had no apparent effect on water quality, tilapia growth, or digestive enzyme activity. However, MPs accumulated the most in the liver (5.65 ± 0.74 μg/mg) and significantly increased the hepato-somatic index of tilapia and reduced the crude protein and lipid of tilapia muscle (p < 0.05). The levels of the antioxidant enzymes catalase and glutathione S-transferase increased significantly in response to MPs (p < 0.05). In contrast, MPs did not affect the content of glutathione, glutathione peroxidase, oxidized glutathione, and malondialdehyde, or the enzyme activity of Na+/K+-ATPase. Moreover, using an improved integrated biomarker response index, growth performance was found to be less responsive to MPs than to oxidative stress and digestive activity. Exposure to MPs did not significantly influence the microbial communities of the bioflocs and tilapia guts (p < 0.05). These results suggest that MPs barely affected tilapia in the bioflocs system. This study contributes to the evaluation of the ecological risk of MPs in aquaculture systems and a better understanding of the integrated response of cultivated vertebrates to MPs in biofloc technology systems.
Display omitted
•Microplastics concentration in tilapia tissue was liver>gill>gut.•Effect of microplastics on tilapia growth was not significant.•Microplastics reduced the crude protein and lipid of tilapia.•Microplastics did not influence microbial community of bioflocs and tilapia gut significantly.
Summary
Building on Yu and Kumbier's predictability, computability and stability (PCS) framework and for randomised experiments, we introduce a novel methodology for Stable Discovery of Interpretable ...Subgroups via Calibration (StaDISC), with large heterogeneous treatment effects. StaDISC was developed during our re‐analysis of the 1999–2000 VIGOR study, an 8076‐patient randomised controlled trial that compared the risk of adverse events from a then newly approved drug, rofecoxib (Vioxx), with that from an older drug naproxen. Vioxx was found to, on average and in comparison with naproxen, reduce the risk of gastrointestinal events but increase the risk of thrombotic cardiovascular events. Applying StaDISC, we fit 18 popular conditional average treatment effect (CATE) estimators for both outcomes and use calibration to demonstrate their poor global performance. However, they are locally well‐calibrated and stable, enabling the identification of patient groups with larger than (estimated) average treatment effects. In fact, StaDISC discovers three clinically interpretable subgroups each for the gastrointestinal outcome (totalling 29.4% of the study size) and the thrombotic cardiovascular outcome (totalling 11.0%). Complementary analyses of the found subgroups using the 2001–2004 APPROVe study, a separate independently conducted randomised controlled trial with 2587 patients, provide further supporting evidence for the promise of StaDISC.
China has proposed to achieve carbon neutrality by 2060. Although previous studies have assessed net-zero emissions pathways in China, the diversity observed in these studies in terms of model ...construction and parameter setting has led to inconsistent conclusions on some key issues, such as energy transition. This study employs a multi-model comparison method to examine the significance of China's carbon neutrality target on its energy systems by assessing 67 carbon neutrality scenarios in China that are collected from the ADVANCE database, and identifying the differences between energy transition pathways under BEF60 scenarios (i.e. scenarios realising carbon neutrality by 2060) and AFT60 scenarios (i.e. scenarios realising carbon neutrality after 2060). Results show that China needs a larger deployment of low-carbon electricity, a higher electrification rate and more carbon sequestration amount under BEF60 scenarios than those under AFT60 scenarios. Meanwhile, the magnitude of the difference between the two categories of scenarios varies significantly in terms of different outcome indicators. Those that present significant disparities include the deployment scale of solar power (increasing by 160%), the electrification rate of the building sector (increasing by 27%) and the carbon sequestration amount of biomass power with carbon capture and storage (increasing by 380%). In addition, this study selects six indicators to present the technological and economic characteristics of various energy systems of China at the point of net-zero emissions. Exploring the relationships between characteristics, this research identifies the common features among various net-zero energy systems. A great share of non-biomass renewable power generation is always associated with a relatively high per capita energy use, implying that high renewables penetration may relax restrictions on energy consumption, which should be addressed for China when making efforts to promote energy transition.
Use of Smart Loads for Power Quality Improvement Shuo Yan; Siew-Chong Tan; Chi-Kwan Lee ...
IEEE journal of emerging and selected topics in power electronics,
03/2017, Volume:
5, Issue:
1
Journal Article
Peer reviewed
Open access
Electric spring (ES) was originally proposed as a distributed demand-side management technology for making noncritical loads adaptive to the availability of intermittent renewable power generation. ...The second generation of ES, fed with batteries (ES-2) and associated with a noncritical load, can form a new kind of combined smart load and distributed energy storage technology for smart grids. With its four-quadrant operation, ES-2 is able to offer ancillary grid services in addition to its major functions of voltage and frequency regulation. This paper presents the operating principles and the input current control of ES-2 for power quality improvement such as power factor correction and harmonics reduction. The operating principles and the proposed input current control have been verified with the experimental results obtained from a small-scale power grid. Another weak single-phase power system fed by intermittent wind power is set up to prove the combined operation of ES-2 for power quality improvement and ES-1 (ES with capacitor storage) for voltage stabilization. The experimental results show that ES-2 with input current control can carry out power quality improvement as its ancillary function.
DC electric springs (DCES) are emerging technologies for the (i) regulation of mains voltage against the intermittent renewable generations and (ii) harmonic cancellation in dc microgrids. When ...conventional converter topologies (e.g., half-bridge or full-bridge converter) are adopted as DCES, the battery storage of the DCES has to process both the dc power and the ac harmonic power. The pulsating ac power can severely reduce the lifetime of the battery. To address this issue, a hybrid-DCES (H-DCES) is proposed in this paper to perform (i) and (ii) in a decoupled manner. With a modified topology and control method, the H-DCES can divert the ac current to the ground and retains the function of manipulating noncritical load for dc voltage regulation. The immediate benefits of this H-DCES are the reduction of storage capacity and a prolonged lifetime of the battery. Both the operating principle and the mathematical model of the proposed H-DCES are analyzed in this paper. A prototype of the H-DCES is practically tested in a 48-V dc grid. The experimental results show that the H-DCES can realize the decoupled operation of dc voltage regulation and harmonic cancellation. Simulation studies further demonstrate that the H-DCES requires less storage capacity than its counterparts.
Global climate governance is currently at the stage of carbon neutrality. Improving the quality of emissions inventories at different levels has become a critical climate governance task, which not ...only contributes to the Global Stocktake but also helps verify compliance progress and address new trade barriers. This study provides a comprehensive review of international carbon accounting standards and guidelines while assessing the potential impact of upcoming carbon tax policies, such as the EU CBAM and the U.S. CCA. On this basis, the current situation and challenges of China's carbon emission accounting system are systematically analysed, and suggestions for improvement are proposed. The results show that carbon tax policies will increase the requirements for emission inventories and will strengthen the correlation between different levels. The improvement of China's carbon accounting system should be accelerated. Although the regional carbon accounting guidelines are already in line with international guidelines, further improvements are needed at the enterprise and product levels. New boundaries need to be set in China's corporate carbon accounting guidelines, and the speed of developing product carbon accounting guidelines should be increased. The quality of emissions inventories should be comprehensively improved by implementing a combination of policies, including corporate carbon information disclosure, green supply chain construction, activity data statistics and verification, and a dynamic emission factor database.
Abstract
Background
Endovascular recanalization in patients with symptomatic nonacute intracranial large artery occlusion (ILAO) has been reported to be feasible, but technically challenging. This ...study aimed to determine the predictors of successful endovascular recanalization in patients with symptomatic nonacute ILAO.
Methods
The outcomes of endovascular recanalization attempts performed in 70 consecutive patients showing symptomatic nonacute ILAO with hemodynamic cerebral ischemia between January 2016 to December 2022 were reviewed. Potential variables, including clinical and radiological characteristics related to technical success, were collected. Univariate analysis and multivariate logistic regression were performed to identify predictors of successful recanalization for nonacute ILAO.
Results
Technically successful recanalization was achieved in 57 patients (81.4%). The periprocedural complication rate was 21.4% (15 of 70), and the overall 30-day morbidity and mortality rates were 7.1% (5 of 70) and 2.9% (2 of 70), respectively. Univariate analysis showed that successful recanalization was associated with occlusion duration, stump morphology, occlusion length, slow distal antegrade flow sign, and the presence of bridging collateral vessels. Multivariate analysis showed that occlusion duration ≤ 3 months (odds ratio OR: 22.529; 95% confidence interval CI: 1.636-310.141), tapered stump (OR: 7.498; 95% CI: 1.533–36.671), and occlusion length < 10 mm (OR: 7.049; 95% CI: 1.402–35.441) were independent predictive factors for technical success of recanalization.
Conclusions
Occlusion duration ≤ 3 months, tapered stump, and occlusion length < 10 mm were independent positive predictors of technical success of endovascular recanalization for symptomatic nonacute ILAO. These findings may help predict the likelihood of successful recanalization in patients with symptomatic nonacute ILAO and also provide a reference for the selection of appropriate patients. Further prospective and multicenter studies are required to validate our findings.
PDF
