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As the load center in East China, the receiving-end power grid in the Yangtze River Delta is densely distributed with conventional DC and faces great security and stability risks in the context of the development of dual-carbon and new power systems. Based on the existing problems in the Yangtze River Delta power grid, this paper draws up different DC technology routes and compares and selects them based on the safety and stability support capabilities and reactive power support capabilities of the receiving-end power grid, the impact on the short-circuit current of the system, technology maturity, land occupation, and economy, and finally put forward the recommended technical route for a foreign power to enter Shanghai.

With the increase distance of offshore wind farm, the investment proportion of high-voltage delivery submarine cable in the whole project is gradually increasing, so the reasonable selection of cable delivery scheme becomes more and more important. In this paper, for different scales of offshore wind farms, the preliminary selection basis of two delivery schemes of AC high-voltage and flexible DC is proposed, and the economic and technical comparison principles of different AC delivery schemes are further analyzed with engineering example. In general, for medium-sized offshore wind farms, if the AC high-voltage transmission scheme is used, a reactive power compensation station can be set in the middle of the cable to improve the current distribution on the cable.

Samples of PM2.5 were collected at three urban sites and one rural site simultaneously in Chongqing, the only megacity in eastern Sichuan Basin, Southwest China, from October 15 to November 13, 2015. Water-soluble ions (WSIs, i.e., F–, Cl–, NO3–, SO42–, K+, Na+, NH4+, Mg2+ and Ca2+) in PM2.5 were measured to investigate their characteristics and formation pathways. The average concentrations of PM2.5 at the urban sites were 55.5–59.0 µg m–3, which was 62.8–73.0% higher than that at rural site. SO42–, NO3–, NH4+ were the dominant ions, contributing to more than 90% of total WSIs. The coefficients of divergence for SO42– between the urban and rural sites were 0.15–0.17, indicating its relatively uniform distribution across Chongqing. Analysis of the formation mechanisms of SO42– and NO3– in PM2.5 suggested that the heterogeneous reaction was responsible for the high concentrations of sulfate among the four sites, whereas nitrate was formed mainly through homogeneous reactions at the urban sites. Furthermore, the results of trajectory clustering showed that the air pollution were mainly from local sources within the basin. Our findings on PM2.5 composition in Chongqing help to advance the knowledge on PM2.5 pollution in Chinese megacities, and to provide more evidence for further pollution mitigation.

Nowadays, the fine particle pollution is still severe in some megacities of China, especially in the Sichuan Basin, southwestern China. In order to understand the causes, sources, and impacts of fine particles, we collected PM

Carbonaceous aerosols pose significant climatic impact, however, their sources and respective contribution to light absorption vary and remain poorly understood. In this work, filter-based PM

The flow structure and stability of oblique detonation waves (ODWs) affected by shock wave-boundary layer interactions (SBLIs) are investigated based on Reynolds averaging method. ODWs with...

With the expansion of the scale of power grid interconnection, the grid connection is becoming more and more closely, and the grid resistance ratio is also increasing, which slows down the attenuation of the DC component of the short-circuit current, and affects the checking of the breaking capacity of the circuit breaker. At present, in practice, only the periodic component of the short circuit point is considered in checking the breaking capacity of the circuit breaker, and the short-circuit asymmetric current affected by the DC component is not considered. A method is proposed to calculate the DC component of the short circuit current flowing through the circuit breaker directly in this paper. Firstly, the fault point is divided into two parts by node splitting method, and the node impedance matrix is modified based on the branch-adding method. Then, the DC component of the short-circuit current can be obtained by using the transfer impedance obtained by the modified node impedance matrix. Finally, the maximum short-circuit asymmetric current flowing through the circuit breaker branch is calculated and compared with the symmetric component of the short-circuit point. It is suggested that the former should be used to check the breaking capacity of the circuit breaker.

Time-frequency analysis is a prerequisite for intelligent recognition of radar signal types based on deep learning network. Deep learning uses Convolutional Neural Network (CNN) to automatically extract the time-frequency images (TFIs) features of radar signals to achieve intelligent recognition of radar signal modulation methods. However, the quality of TFI generated by different time-frequency conversions is usually different to a certain extent. At present, the selection of time-frequency analysis methods in many pieces of research is mainly done through the feature differences of TFIs. There are certain subjective factors, which cannot provide a reference for subsequent research. This paper proposes a time-frequency analysis method performance evaluation model based on Support Vector Machine (SVM). The simulation results show that the evaluation model can make an objective and optimal choice based on the data, and can provide a valuable reference for subsequent research.

Water-soluble proteinaceous matter including proteins and free amino acids (FAAs) as well as some other chemical components was analyzed in fine particulate matter (PM2.5) samples collected over a period of one year in rural Guangzhou. Annual averaged protein and total FAAs concentrations were 0.79 ± 0.47 μg m–3 and 0.13 ± 0.05 μg m–3, accounting for 1.9 ± 0.7% and 0.3 ± 0.1% of PM2.5, respectively. Among FAAs, glycine was the most abundant species (19.9%), followed by valine (18.5%), methionine (16.1%), and phenylalanine (13.5%). Both proteins and FAAs exhibited distinct seasonal variations with higher concentrations in autumn and winter than those in spring and summer. Correlation analysis suggests that aerosol proteinaceous matter was mainly derived from intensive agricultural activities, biomass burning, and fugitive dust/soil resuspension. Significant correlations between proteins/FAAs and atmospheric oxidant (O3) indicate that proteins/FAAs may be involved in O3 related atmospheric processes. Our ob...

As important pollution gases and represented precursors of both ozone and second organic aerosol (SOA), the component characteristics, source origins, environmental health and emission control of volatile organic compounds (VOCs), are gaining more and more attention in Chinese megacities. In order to understand the concentration, composition and temporal and spatial distribution characteristics of VOCs in the atmosphere of Chengdu, a megacity located in Sichuan basin in southwest China, the offline sampling measurements of VOCs were carried out at 28 different field sites covering all the districts and counties of Chengdu during special periods from May 2016 to January 2017. Speciated VOCs measurement was performed by the GC-FID/MS, and 99 species were identified. The averaged total VOC mixing ratios of each sampling site were in the range from 35.03 to 180.57 ppbv. Based on these observational data, the distribution characteristics of VOCs in different months and different regions of Chengdu were clarified. The VOCs data were used to estimate the potential amount of ozone, secondary aerosol formation and health risk assessment in Chengdu. Furthermore, the positive matrix factorization (PMF) model was used to identify the dominant emission sources and evaluate their contribution to VOCs in the city. The two main sources of VOCs in Chengdu were motor vehicle exhaust and solvent utilization. These accounted for 43% of all emission sources. In the summertime, due to higher temperatures and stronger sunlight, the contribution of natural sources and secondary emissions were also relatively high, which were supported by the regional emission inventories. Finally, the controlling direction of VOCs and O3 pollution in Chengdu was discussed, and the VOCs pollution control strategy was proposed for the near future.

Aerosol proteinaceous matter is comprised of a substantial fraction of bioaerosols. Its origins and interactions in the atmosphere remain poorly understood. We present observations of total proteins, combined, and free amino acids (CAAs and FAAs) in fine particulate matter (PM2.5) samples in urban Beijing before and during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. The decreases in proteins, CAAs and FAAs levels were observed after the implementation of restrictive emission controls. Significant changes were observed for the composition profiles in FAAs with the predominance of valine before the APEC and glycine during the APEC, respectively. These variations could be attributed to the influence of sources, atmospheric processes, and meteorological conditions. FAAs (especially valine and glycine) were suggested to be released by the degradation of high molecular weight proteins/polypeptides by atmospheric oxidants (i.e., ozone and free radicals) and nitrogen dioxide. Besides daytime reactions, nighttime chemistry was found to play an important role in the atmospheric formation of valine during the nights, suggesting the possible influence of NO3 radicals. Our findings provide new insights into the significant impacts of atmospheric oxidation capacity on the occurrence and transformation of aerosol proteinaceous matter which may affect its environmental, climate and health effects.

Demand response (DR) in the wholesale electricity market provides an economical and efficient way for customers to participate in the trade during the DR event period. There are various methods to measure the performance of a DR program, among which customer baseline load (CBL) is the most important method in this regard. It provides a prediction of counterfactual consumption levels that customer load would have been without a DR program. Actually, it is an expected load profile. Since the calculation of CBL should be fair and simple, the typical methods that are based on the average model and regression model are the two widely used methods. In this paper, a cluster-based approach is proposed considering the multiple power usage patterns of an individual customer throughout the year. It divides loads of a customer into different types of power usage patterns and it implicitly incorporates the impact of weather and holiday into the CBL calculation. As a result, different baseline calculation approaches could be applied to each customer according to the type of his power usage patterns. Finally, several case studies are conducted on the actual utility meter data, through which the effectiveness of the proposed CBL calculation approach is verified.

Neutral Polyfluoroalkyl substances (PFASs) in the atmosphere were measured during a cruise campaign over the northern South China Sea (SCS) from September to October 2013. Four groups of PFASs, i.e., fluorotelomer alcohols (FTOHs), fluorotelomer acrylates (FTAs), fluorooctane sulfonamides (FOSAs) and fluorooctane sulfonamidoethanols (FASEs), were detected in gas samples. FTOHs was the predominant PFAS group, accounting for 95.2-99.3% of total PFASs (Sigma PFASs), while the other PFASs accounted for a small fraction of Sigma PFASs. The concentrations of PFASs ranged from 18.0 to 109.9 pg m(-3) with an average of 54.5 pg m(-3). The concentrations are comparable to those reported in other marine atmosphere. Higher concentrations of PFASs were observed in the continental-influenced samples than those in other samples, pointing to the substantial contribution of anthropogenic sources. Long-range transport is suggested to be a major pathway for introducing gaseous PFASs into the atmosphere over the northern SCS. In order to further understand the fate of gaseous PFASs during transport, the atmospheric decay of neutral PFASs under the influence of reaction with OH radicals and atmospheric physical processes were estimated. Concentrations of 8:2 FTOH, 6:2 FTOH and MeFBSE from selected source region to the atmosphere over the SCS after long-range transport were predicted and compared with the observed concentrations. It suggests that the reaction with OH radicals may play an important role in the atmospheric decay of PFAS during long-range transport, especially for shorted-lived species. Moreover, the influence of atmospheric physical processes on the decay of PFAS should be further considered. (C) 2016 Elsevier Ltd. All rights reserved.

This paper proposes a framework for modeling an integrated port energy system (IPES). A configuration and sizing model of energy hub (EH) is built for the port area considering integrated demand response (IDR) and energy interconnection (EI). A comparative study of five different planning scenarios, traditional energy supply solution, EH solution, EH with IDR, EH with EI, and EH with both IDR and EI are conducted to identify the best option for minimizing the total planning cost of an IPES. Furthermore, the daily operating conditions of EHs are discussed and sensitivity analyses with varying energy prices, line loss rates, and IDR participation rates are performed to demonstrate the robustness of the model. The impacts of the uncertainties of ships using shore-side power on planning costs are also analyzed. Based on the proposed methods, numerical simulation results show the effectiveness of the EHs with multiple energy infrastructures in the IPES. In addition, after considering IDR and EI, the total planning cost decreases significantly, which demonstrates the necessity and benefits of IDR and EI.

Under the retail electricity market reform and the development of demand-side integrated energy systems in China, the Integrated Energy Service Agency (IESA) is responsible for purchasing energy from the external market and supplying it to multi-energy users (MEUs). However, with the increase in the types of MEUs, the IESA has gained more sales options. How to meet the required MEU participation level in the integrated demand response (IDR) plan to ensure that the IESA sets the optimal integrated energy price is an urgent problem. In this paper, a bi-level optimal low-carbon economic dispatch model for an industrial park is proposed considering multi-energy price incentives; at the upper level, the model takes the optimal net income of the IESA as the target, and the carbon emission constraints of the real-time unit integrated energy supply are considered, so that the IESA can reasonably dispatch a comprehensive energy supply, optimize the operation of energy conversion equipment, and set reasonable energy selling prices based on energy prices in the external market. At the lower level, the model takes the minimum integrated energy cost to MEUs as the goal. MEUs take the initiative to obtain retail energy price signals, formulate optimal multi-energy use strategies, and actively participate in the IDR plan. At the same time, coordination between the upper and lower levels helps to optimize the price of the energy sold and the power used by the IDR and is therefore used to achieve the overall environmental and economic requirements of the industrial park. The prime dual path following the interior point method is used to solve the nonlinear, multidimensional, and double-iterative optimization model, and three typical examples are used to illustrate that the model and method can improve the net income of the IESA, ensure the economic and environmental protection of the cooperative multi-energy operation, and encourage MEUs to actively participate in the IDR plan.

In order to build a green port and achieve energy conservation and emission reduction in energy internet, the economic problems brought by shore-to-ship power system have attracted more attention than ever. This paper analyzes the construction and operation cost of the whole shore-to-ship power system from the point of view of economics. The corresponding mathematical model is constructed and the cost-effectiveness of grid companies, ports, ships and the government is analyzed by using the economic optimum principle. Then, the optimal shore-to-ship power price is calculated. At last, according to the proposed model, the relationship between the government subsidy rate, the shore-side power utilization time and the profits of all parties is analyzed, which provides reference for power grid company, port and government to promote shore-to-ship power system.

Nine organophosphate esters (OPEs) in airborne particles were measured during a cruise campaign over the northern South China Sea (SCS) from September to October 2013. The concentration of the total OPEs (∑OPEs) was 47.1-160.9 pg m(-3), which are lower than previous measurements in marine atmosphere environments. Higher OPE concentrations were observed in terrestrially influenced samples, suggesting that OPE concentrations were significantly influenced by air mass transport. Chlorinated OPEs were the dominant OPEs, accounting for 65.8-83.7% of the ∑OPEs. Tris-(2-chloroethyl) phosphate (TCEP) was the predominant OPE compound in the samples (45.0±12.1%), followed by tris-(1-chloro-2-propyl) phosphates (TCPPs) (28.8±8.9%). Dry particle-bound deposition fluxes ranged from 8.2 to 27.8 ng m(-2) d(-1) for the ∑OPEs. Moreover, the dry deposition input of the ∑OPEs was estimated to be 4.98 ton y(-1) in 2013 in a vast area of northern SCS. About half of the input was found to relate to air masses originating from China.