A novel framework for photovoltaic energy optimization based on supply–demand constraints

Introduction: Distributed power supply has increasingly taken over as the energy industry’s primary development direction as a result of the advancement of new energy technology and energy connectivity technology. In order to build isolated island microgrids, such as villages, islands, and remote mountainous places, the distributed power supply design is frequently employed. Due to government subsidies and declining capital costs, the configured capacity of new energy resources like solar and wind energy has been substantially rising in recent years. However, the new energy sources might lead to a number of significant operational problems, including over-voltage and ongoing swings in the price of power. Additionally, the economic advantages availed by electricity consumers may be impacted by the change in electricity costs and the unpredictability of the output power of renewable energy sources.Methods: This paper proposes a novel framework for enhancing renewable energy management and reducing the investment constraint of energy storage. First, the energy storage incentive is determined through a bi-level game method. Then, the net incentive of each element is maximized by deploying a master–slave approach. Finally, a reward and punishment strategy is employed to optimize the energy storage in the cluster.Results: Simulation results show that the proposed framework has better performance under different operating conditions.Discussion: The energy storage operators and numerous energy storage users can implement master–slave game-based energy storage pricing and capacity optimization techniques to help each party make the best choices possible and realize the multi-subject interests of energy storage leasing supply and demand win–win conditions

Prioritized High-Confidence Risk Genes for Intellectual Disability Reveal Molecular Convergence During Brain Development

Dissecting the genetic susceptibility to intellectual disability (ID) based on de novo mutations (DNMs) will aid our understanding of the neurobiological and genetic basis of ID. In this study, we identify 63 high-confidence ID genes with q-values < 0.1 based on four background DNM rates and coding DNM data sets from multiple sequencing cohorts. Bioinformatic annotations revealed a higher burden of these 63 ID genes in FMRP targets and CHD8 targets, and these genes show evolutionary constraint against functional genetic variation. Moreover, these ID risk genes were preferentially expressed in the cortical regions from the early fetal to late mid-fetal stages. In particular, a genome-wide weighted co-expression network analysis suggested that ID genes tightly converge onto two biological modules (M1 and M2) during human brain development. Functional annotations showed specific enrichment of chromatin modification and transcriptional regulation for M1 and synaptic function for M2, implying the divergent etiology of the two modules. In addition, we curated 12 additional strong ID risk genes whose molecular interconnectivity with known ID genes (q-values < 0.3) was greater than random. These findings further highlight the biological convergence of ID risk genes and help improve our understanding of the genetic architecture of ID

Simulation and Protection of Reignition Overvoltage in Wind Farm Considering Microscopic Dielectric Recovery Process of Vacuum Circuit Breaker

The high amplitude and steep overvoltage generated by the breaking of the vacuum circuit breaker in the wind farm damages the inter-turn insulation of the transformer. There is a certain difference between the simulation results of the traditional reignition model and the measured overvoltage. It is necessary to improve the simulation model to simulate the overvoltage condition of the transformer more accurately and then select appropriate overvoltage protection measures. In this paper, based on the physical process of dielectric recovery during the opening process of the vacuum circuit breaker, a model of dielectric strength recovery is built to simulate the arc reignition of the vacuum circuit breaker. The model was applied to compare the overvoltage protection effects of RC snubbers, surge arresters, and choke coils. The simulation results show that the overvoltage amplitude and reignition times calculated by the model proposed in this paper are closer to the measured values. Compared with the traditional linear curve reignition model, the accuracy was increased by 24% and 51.2%, respectively. The parameter value of RC snubbers, the connection mode of surge arresters, and the combination mode of choke coil have an influence on overvoltage suppression. Finally, a suitable suppression scheme is proposed by installing a combined arrester on the high-voltage side of the transformer and connecting a choke coil in series, which can limit the phase-to-ground voltage and the phase-to-phase voltage to 2.43 p.u and 3.24 p.u, respectively, and reduce the steepness from 157.2 kV/μs to 22.3 kV/μs

Suppression of Chattering in the Real-time Simulation of the Power Converter

International audienceThe achievement of the time-step below 500-ns in the field-programmable-gate-arrays (FPGAs)-based real-time simulation is of importance for the power converters having high switching frequencies. However, most of the existing focus on addressing the power converter modeling under the continuous conduction mode (CCM). Nevertheless, towards practical applications, the modeling of discontinuous conduction mode (DCM) with a light-load is of a greater challenge due to the chattering around zero point. In order to solve the chattering problem under the light-load, this paper proposes a zero-regulation (ZR) method for FPGA-based real-time simulation. The proposed ZR method can not only represent CCM and DCM with a unified formula but also solve the chattering problem and improve accuracy and stability. In addition, results using different switch models are also given to demonstrate the feasibility and the generality of the proposed method. Finally, a case study of the series load resonant (SLR) converter is presented. Simulation results are validated against a reference model at a 100-ns time step and a 10-kHz switching frequency

Inter-Turn Breakdown Fault Analysis and Winding Structure Optimisation of Winding of Dry-Type Transformers in Wind Farms

To address the problem of winding turn-to-turn breakdown faults in 35 kV dry-type transformers in wind farms under overvoltage conditions, this paper establishes a simulation model based on the structural dimensions and material parameters of the transformer windings. The winding distribution parameters were calculated using the finite element method. The transient processes inside the high-voltage coil were calculated by constructing a multi-conductor transmission line model (MTL) that took into account the influence of the secondary winding. The voltage distribution of the winding was analysed for both lightning shock and extra-fast transient overvoltage conditions. The simulation results show that the maximum overvoltage between turns of the transformer winding under lightning shock is 5.282 kV; the maximum overvoltage between turns of the winding under very fast transient overvoltage is 11.6 kV, which occurs between the first 2–3 layers of the section, close to the insulation breakdown margin. On this basis, the transformer winding structure was optimised and the maximum inter-turn overvoltage after optimisation was 9.104 kV, reducing the likelihood of insulation breakdown by 24.1%. Finally, the accuracy of the winding structure optimisation simulation study was verified by testing the transformer’s impulse voltage before and after optimisation, providing a reference for the stable operation of 35 kV dry-type transformers in wind farm practical applications

Port reduction operation of a three?port nonagonal modular multilevel converter as soft open point

Nonagonal modular multilevel converter (MMC) is a three-port AC/AC converter promising as a soft open point (SOP) to connect different AC feeders or buses in distribution networks, owing to its flexible power control, transformerless structure, and low power component count and its capability of accommodating multiple AC ports of different frequencies. An SOP should be able to work under port reduction condition, which is often encountered when maintenance is required or the network structure is reconfigured. However, as a component reuse converter of circular structure, nonagonal MMC cannot turn off one or some of its branches to achieve this. To address this issue, a control scheme is proposed in this paper to enable nonagonal MMC to operate under port reduction condition by switching the nonagonal MMC to a hexagonal MMC, which is an AC/AC topology of a similar circular structure but has only two ports. Without inserting extra switches, the nine branches of nonagonal MMC is redistributed into six branches. By alternately operating the submodules, no submodules need to be shut down, reducing the submodule capacitor voltage fluctuation during port reduction operation. RTlab results verify the feasibility of the quasi-hexagonal topology and the effectiveness of port reduction control

Study of tissue engineered vascularised oral mucosa-like structures based on ACVM-0.25% HLC-I scaffold in vitro and in vivo

AbstractPurpose To explore the feasibility of constructing tissue-engineered vascularised oral mucosa-like structures with rabbit ACVM-0.25% HLC-I scaffold and human gingival fibroblasts (HGFs), human gingival epithelial cells (HGECs) and vascular endothelial-like cells (VEC-like cells).Method Haematoxylin and Eosin (H&E) staining, immunohistochemical, immunofluorescence, 5-ethynyl-2′-deoxyuridine (EdU) staining and scanning electron microscope (SEM) were performed to detect the growth status of cells on the scaffold complex. After the scaffold complex implanted into nude mice for 28 days, tissues were harvested to observe the cell viability and morphology by the same method as above. Additionally, biomechanical experiments were used to assess the stability of composite scaffold.Results Immunofluorescence and Immunohistochemistry showed positive expression of Vimentin, S100A4 and CK, and the induced VEC-like cells had the ability to form tubule-like structures. In vitro observation results showed that HGFs, HGECs and VEC-like had good compatibility with ACVM-0.25% HLC-I and could be layered and grow in the scaffold. After implanted, the mice had no immune rejection and no obvious scar repair on the body surface. The biomfechanical test results showed that the composite scaffold has strong stability.Conclusion The tissue-engineered vascularised complexes constructed by HGFs, HGECs, VEC-like cells and ACVM-0.25% HLC-I has good biocompatibility and considerable strength

Step-up switched-capacitor multilevel inverter employing multiple inputs with reduced switches

A large device count, weak boosting capability, and DC voltage imbalance are common issues in conventional multilevel inverters. In this paper, a novel multilevel inverter is presented that can generate the desired number of output levels with reduced devices by using new switched-capacitor circuits (SCCs). The two input sources and capacitors in the SCC can be switched in parallel and series modes. In the parallel mode, the capacitor voltage of the SCC is charged to the DC source voltage, which inherently solves the capacitor voltage imbalance issue without any auxiliary circuits. In the series mode, the capacitor can be used as an alternative source, which helps achieve a high voltage gain. The multiple input sources of the SCC make the proposed topology suitable for application in renewable energy generation systems where several DC sources are available. Instead of an H-bridge module, a structure with two half-bridges and two switches is used as a polarity generation circuit at the load terminal. The input sources of two SCCs can be selected as symmetric and asymmetric patterns, which can result in a great number of output voltage levels. The circuit topology, operational principle, modulation strategy, capacitor analysis, and performance comparisons of the inverter are described in this paper. In addition, experimental results verify the feasibility and validity of the inverter

Vibrational dephasing of self-assembling monolayer on gold surface

Ultrafast vibrational dephasing processes of ODT (1-Octadecanethiol) on Au surface had been investigated with time-resolved broadband vibrational sum frequency generation spectroscopy. Vibrational dephasing time constants obtained from different visible wavelength varying from 470 nm to 810 nm. The results showed that electronic structure of the gold substrate plays an important role in surface molecule dephasing dynamics. (C) 2013 Elsevier B.V. All rights reserved