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RSS2020 Vol. 7, No. 1
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2020, 7(1): 1-7.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.001
Abstract:
[Introduction] Supercritical CO2 (sCO2) Brayton cycle is a promising technology to improve the efficiency of concentrated solar power systems. [Method] This paper presented an equation-based nonlinear programming model for the analysis and optimization of the power tower concentrated solar power (CSP) coupled with supercritical CO2 (sCO2) Brayton cycles. The model included CSP subsystems, sCO2 Brayton cycle, and high accuracy equation of state, enabling simultaneous optimization of the systems with arbitrary number of decision variables. Case studies of the integrated CSP-simple sCO2 Brayton cycle and CSP-recompression sCO2 Brayton cycle systems were carried out to determine their optimal design. [Result] The results show that thermal efficiency of the CSP-recompression cycle system can reach a maximum of 29.4%, higher than the 24.9% of the CSP-simple cycle system. The optimal turbine inlet temperature is 901 K for the CSP-recompression cycle system, 826 K for the CSP-simple cycle system. The optimal expansion ratios of the CSP-simple cycle system are greater than 3.2 at the investigated temperature range, and are approximately equal to 3 for the CSP-recompression cycle system. [Conclusion] There are optimal turbine inlet temperatures and compression ratios for the integrated systems.Additionally, the compression ratio has a greater impact on the thermal efficiency of the CSP-simple cycle system.
2020, 7(1): 8-20.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.002
Abstract:
[Introduction] Floating offshore wind turbines technology is developing rapidly in Europe, America and Japan, and other developed countries, because of its advantages, such as non-restriction of water depth, easy installation, maintenance, transport, etc.This paper reviews the key technologies and engineering cases of floating offshore wind turbines, in order to provide references for research works and projects in this field. [Method] This paper introduced the background of floating wind turbines technology,and then provided detailed introduction on its key technologies, for instance, stability checking, mooring sysytem, dynamic cable,hydrodynamics, aerodynamics, integral calculation, model basin tests, manufacture, installation, engineering challenges and cases.Finally, the paper summarized potential market and applications of floating wind turbines technologies. [Result] The paper summarizes the state of art of the key technologies and future development of floating wind turbines. [Conclusion] This review presents the key technologies and engineering cases of floating wind turbines. There are quite a few technology challenges and problems which worried industry. Hence, the solution to reduce project cost and to facilitated the growth of the industry is multipath, for instance, the more active policy support, making technological breakthrough, and cultivation of the industrial chain.
2020, 7(1): 21-26.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.003
Abstract:
[Introduction] The paper proposes and implements an architecture scheme of regional integrated energy control and service management system to meet the actual demands of regional comprehensive energy management and service of various types such as electricity, heat, gas and water. [Method] Combined with new technologies and new concepts such as big data, cloud platform, internet of things, mobile internet and smart city, the regional integrated energy control and service management system was maily designed six functional applications. The applications included energy monitoring, energy analysis, energy management, operation and maintenance, transaction settlement, and value-added services. [Result] The application of practical cases illustrates that the system can meet the comprehensive energy management and service requirements for energy supply side and demand side of three typical application scenarios of enterprise level, park level and regional level. [Conclusion] This system can effectively support regional integrated energy control and service management. And it is expected to tap the potential of energy conservation, improve energy efficiency, enhance energy management level, and make the environment better.
2020, 7(1): 27-32.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.004
Abstract:
[Introduction] The paper aims to excavate the potential physical significance of the large load data of distribution network users in the park, and provide the basis for optimizing the decision-making of the park operators, the characteristics and potential of peak and valley of distribution network are studied in this paper. [Method] Based on the research of time-sharing tariff division method, this paper used the theory of fuzzy mathematics, used membership function and constructed a fuzzy similarity matrix to divide the peak-to-valley period of user load curve with the potential of peak shifting and valley filling. [Result] Through comparison and verification, the result of partition is highly consistent with the actual situation, which proves the effectiveness of this method. On this basis, the peak-valley characteristics and the potential of peak-valley shifting and valley filling of the park distribution network are analyzed and studied. [Conclusion] The research conclusion has theoretical significance and practical value for making safe, economic and reliable operation strategies of the park distribution network.
2020, 7(1): 33-39.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.005
Abstract:
[Introduction] Grouted connections are widely used to connect the support structure and the foundation of offshore wind turbines. Therefore, their mechanical properties are very important to the reliability of the whole structure. In order to find a proper method to evaluate the stresses of grouted connections, numerical simulations were conducted. [Method] Numerical models were established to investigate the stress distribution of a grouted connection under given compression and bending loads. The conceptions of nominal average stress and stress correlation coefficient were then proposed, which were used to evaluate the overall stress level of the grouted connection. Moreover, parameter studies were carried out, and the range of stress correlation coefficients were determined. [Result] It was found that both the Mises stresses of steel tubes and Tresca stresses of the grout were dominated by the locations of shear keys in the grouted connection. And there was an inverse negative correlation between the thickness of steel pipes and the maximum stresses of them. At the same time, the maximum Tresca stresses of the grout were only sensitive to the change of its thickness rather than the change of the thickness of steel tubes. Finally, the stress correlation coefficients all fell between 3 to 6 according to the parametric studies. [Conclusion] The result of parametric studies can partly guide the preliminary designs of grouted connection, and the stress correlation coefficients can be used to approximately evaluate the mechanical properties of grouted connections under combined loads.
2020, 7(1): 40-46.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.006
Abstract:
[Introduction] Large diameter monopile is the most common used foundation in offshore wind projects. The Self Weight Penetration (SWP) usually takes up a large component of total penetration. To better predict the SWP of monopiles, three methods employing design parameters as well as CPT data have been studied in this paper and the preliminary back analysis have been carried out on the basis of the monitoring data on site. [Method] In detail, the method calculating the soil resistance during driving from design parameters, the SWP prediction method recommended in DNV manual and a directly derived CPT method were adopted to predict the SWP of monopiles and the interpretation to the difference between predicted and real penetration depth were made after the analyses. [Result] The results indicate that the SWP prediction with design parameters have better theoretic background but the result are strongly influenced by human factor, the latter CPT methods are based on CPT test data that are more objective but the key coefficients are heavily depend on local experience. [Conclusion] The real SWP depth are also significantly affected by fluctuation of subsoil layers, penetration rates and pile installation procedures; Not a single method can accurately predict the SWP under all conditions; Comprehensive interpretation of analysis results from different methods can improve the reliability of prediction.
2020, 7(1): 47-52.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.007
Abstract:
[Introduction] As a new topic in the field of offshore wind farm, the management, command and dispatch of personnel and vessels is attracting significant interest. This paper introduces an intelligent vessel dispatching and personnel management system for offshore wind farm, which is first creation of its kind in China. [Method] It mainly included three aspects: (1) Efficient command and dispatch system. Efficient command and dispatch was achieved by very high frequency (VHF) marine intercom system, which realized steady intercom communications. The marine intercom system based on maritime high-frequency VHF can be achieved the steady intercom communications. With the automatic identification system (AIS) receiver and the maritime radio station, the identity information and geographical location of the surrounding vessels can be obtained. Meanwhile, the records of the vessels entering the warning zone can be archived and those vessels will also be interrogated. If any drowning staff was spotted, alerting signal would be immediately sent to the onshore command center; (2)The sea area real-time monitoring contained two parts. A far-infrared thermal imaging camera was used to realize remote monitoring for operating conditions of the wind farms. Meanwhile, two cameras and meteorological sensors were mounted on the anemometer tower, which could be used to monitor marine and surge conditions of the neighboring sea area of the wind farm; (3)An accurate marine weather forecasting sub-system was also adopted, which was capable of forecasting on-site environmental conditions such as wind speed, waves, and surges a week ahead. In addition, it can also realized tracking and forecasting of typhoon. [Result] The results suggest that the system is reliable and can realize effective management of personnel as well as vessels, and hence reduces the costs of construction, operation and maintenance concerning the offshore wind farm. [Conclusion] Therefore, the system plays an important role in enhancing the safety production management as well as improving the operation and maintenance efficiency of the offshore wind farm.
2020, 7(1): 53-58.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.008
Abstract:
[Introduction] The construction of offshore wind power projects is in the ascendant, but there is no good regulation as the basis for the selection of exploration methods. The selection of exploration methods at various stages of offshore wind power engineering exploration is under debate. [Method] Based on the induction of offshore wind power engineering survey practice in recent years in China, two factors, such as. the aim and task during the exploration stage and the geological conditions of the site,have the most common influence on the exploration method, which was more suitable for the induction. We selected appropriate exploration methods by classifying the survey stage and classifying the coverage area. [Results] The current classification of offshore wind power engi-neering surveys , the classification of field cover layers and choice of exploration platform were discussed. Based on the influence of various influencing factors on the selection of exploration methods, practical suggestions for the exploration methods applicable in each survey stage were made. [Conclusion] The proposed proposal is suitable for the current actual situation of offshore wind power engineering survey in China. It can provide guidance for the selection of exploration methods at various stages of offshore wind power engineering survey.
2020, 7(1): 59-64.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.009
Abstract:
[Introduction] High slope terrain is easily formed around the turbine site in complex terrain for constructing wind turbine platform, which changes the distribution characteristics of the wind resources and affects the generating capacity and safety performanc.The paper aims to get influence factors of high slope and protect wind turbine. [Method] The numerical simulation method was applied for the high slope terrian for actual wind farm based on STAR-CCM+ software, the wind influence degree of the site selection, the slope grade and the excavation depth were studied in the paper. [Result] It’s shown that the high slope will changes the wind acceleration effect of origin terrain resulting in large-scale fluid separation; When the high side slope is located in the upwind direction of the turbine, the large wind shear is easily generated in the lower blade tip, and the turbulence intensity exceeds the standard value, but the wind resource parameters have good performance when the high side slope is located in the downwind direction of the terrain; The gradient of high slope has no great influence on the wind parameters for the terrain in front of high slope;When the height of the turbine tip is lower than the slope’s, the wind shear will excess standard value. [Conclusion] The results can provide reference for the turbine platform design and tower height of the high slope terrain.
2020, 7(1): 65-69.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.010
Abstract:
[Introduction] Taking the simulated wastewater of desulfurization and denitrification tailings in thermal power plant as the substrate, the effect of sulfide on shortcut nitrification and denitrifying granular sludge on wastewater treatment and the variation of granular sludge are observed. [Method] By changing the oxygen supply conditions of the reactor, the shortcut nitrification process was achieved by using high concentration of salinity and sulfate in the desulfurization and denitrification tail liquid under low oxygen conditions, and the self-supporting denitrification was achieved by using sulfide as an electron donor under anaerobic conditions. [Result] During the adaptation stage, the granular sludge is broken, and the degree of granulation slightly decrease. As the experiment progressing, the removal efficiency increase, and granulation of the sludge recover. Under the condition of HRT of 10 h, the total nitrogen removal rate of 90% was stably achieved. [Conclusion] It shows that the granular sludge can adapt to the desulfurization and denitrification tail liquid in a short time, and can better cope with the complicated water inlet.
2020, 7(1): 70-75.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.011
Abstract:
[Introduction] The phenomenon of false water level in the operation of the thermal power unit deep-peak peak operation seriously affects the safe operation of the unit. Accurately predicts the timing and amplitude of the false water level can optimize the control system design. [Method] Research ideas: the actual water level was regarded as the superposition of the real water level and the false water level. Firstly, the water level model was established according to the energy balance and material balance to calculate the real water level, and then the actual water level was used to reduce the real water level to obtain the false water level,and then used wavelet to analyze the correlation between the fuel quantity, steam drum pressure and other signals and the false water level signal at different time and space scales. [Result] By analyzing the operation data of the deep peak load section of a 600 MW unit, it is found that the influence of feed water flow and steam flow on the false water level signal is effectively eliminated by mechanism modeling; in the frequency band of 0.062 5 Hz to 0.125 Hz, the fuel quantity and the steam drum pressure are strongly correlated with the false water level signal, respectively. [Conclusion] It can help determine the occurrence of false water level and its fluctuation range.
2020, 7(1): 76-83.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.012
Abstract:
[Introduction] The spallation target is an key device of the acceleration driven sub-critical system (ADS). A suitable spallation target structure was designed through the study of the existing target structure, combining the advantages of each type of targets. [Method] MCNPX code was used to calculate the spallation target, CFD code FLUENT was used to the thermal-hydraulic analysis. In order to check the correctness of the thought and methods of calculation, The others works have been repeated, and the results good accord with the results of the article which been repeated. the thermal-hydraulic behavior of the target designed have been calculated by FLUENT. [Result] Obtaining the results of different inlet velocity、different diameter of beam side and the different intensity of beam on the condition of the same thickness of target window, obtaining the allowable intensity of beam under the different thickness of target windows. The operating condition which meet the criterion of thermal-hydraulic and having enough margins have been organized. The formula of the current intensity which changed with the angle have been deducted. The maximum allowable also been obtained from the result of FLUENT. [Conclusion] The results have great important significance for initial designing of target.
2020, 7(1): 84-89.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.013
Abstract:
[Introduction] Essential service water system is responsible for providing cooling water to the nuclear island and bringing heat to the ultimate heat sink,implementing safety classification is helpful to achieve the optimal safety function under the premise of economy. [Method] SSG-30 was the method to classify items according to the importance of their safety functions and the severity of their failure consequences.The security functions of the items were decomposed according to the system process,different functions of the same system could be classified and graded differently, different devices of the same function could be classified differently, and different components of the same equipment could be further graded,functional redundancy could be used to satisfy the single failure criterion. [Result] Grading results can be used to review system functions,for example, the safety level components must meet the seismic requirements and be equipped with emergency power supply before they can be put into operation.The safety level of items can not be reduced according to the mature "engineering experience" in the design of existing PWR. [Conclusion] The method of item classification by functional decomposition can provide references for other PWR project design.
2020, 7(1): 90-94.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.014
Abstract:
[Introduction] There are abundant solar irradiation resources in Guangdong coastal areas. In order to make good use of the light resources, we need to develop and build photovoltaic power stations in these areas, so it is important and necessary to study the typhoon resistance design of photovoltaic supporting bracket system, which is an important structure of photovoltaic power stations.The design parameters of the supporting system have a great influence on the safety and economy of the project. [Method] Taking a photovoltaic power station along Guangdong coast as an example, this paper introduced the key points and practical experience of typhoon resistance design of the supporting system of photovoltaic power station from the aspects of typhoon load parameters,structural shape coefficient and structural measures, combined with numerical simulation of finite element software and post-typhoon disaster assessment. [Result] After the completion of the project, it experiences the test of typhoon "Hato" (Level 17) and"Mangosteen" (Level 14) . After the typhoon, the whole photovoltaic array suffers less damage. [Conclusion] After the completion of the project, several typhoons above grade 12 hit the front of the project, which does not cause serious losses. The structural design of the bracket system is relatively successful, and the design concept and method are confirmed, which can provide guidance for practical application.
2020, 7(1): 95-100.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.015
Abstract:
[Introduction] The“Internet plus”Project between urban and industrial park in support of the revolution of power consumption(abbr.“Internet +”project) successfully pilots multi-voltage multi-terminal flexible DC distribution network technology. [Method] In this article, the overall design plan was discussed. The principle of JS I converter station, which applied self fault clearance MMC based on cross clamped of IGCT devices, and JS II, TJ converter station, which applied half-bridge topology MMC and DC circuit breaker were described. The layout of JS I and JS II, which shared identical converter capacity was introduced.Their covered area and costs were compared. [Result] The results show that both JS I and JS II converter station are functional available and JS I station is slightly more land-saving and cost-saving. [Conclusion] As an important part of the“Internet +”project,the implementation of JS I, JS II and TJ converter station successfully test both the IGCT converter valve with fault self-cleaning capability and the half-bridge IGBT converter valve, successfully test DC breakers with different principles, which can be regarded as an important basis for device standardization.
2020, 7(1): 101-106.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.016
Abstract:
[Introduction] Researches already done on AC/DC interactions in power grid mainly focuses on certain aspects by means of theoretical analysis or digital simulation. With systematic analysis absent, it is not conducive to get a comprehensive understanding of interactions between AC and DC systems. [Method] Based on a large number of studies, this paper established a analysis framework for load center power grids with multiple HVDC infeeds. Firstly, occurrence, development, recovery of HVDC commutation failures and blocking were analyzed, and typical parameters were given. Then meanings and mechanisms of AC/DC interactions were studied,commonly used analysis methods and criteria used in practice were summarized. [Result] The essence of AC/DC interactions are defined. AC/DC interaction analysis framework for load center grids with multiple HVDC infeeds is proposed schematically for the first time. [Conclusion] This paper provides useful reference for further study on AC/DC interaction related problems.
2020, 7(1): 107-112.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.017
Abstract:
[Introduction] Optimizing equipment selection is the basis of realizing intensive layout of converter station and an important part of building green converter station. [Method] Based on the model of conventional and typical converter stations,combined with the production capacity of main equipment and the research & development of new equipment of converter stations at home and abroad, this paper analyzed the characteristics of equipment in different distribution device areas. [Result] This paper presents the construction concept of intensive converter station and puts forward some suggestions on distribution device layout in different areas. [Conclusion] This work provides reference for optimizing the design of converter station and building intensive green converter station.
2020, 7(1): 113-117.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.018
Abstract:
[Introduction] STATCOM is the state-of-the-art equipment for static reactive compensation. This paper focuses on STATCOM design study and key equipment selection principle for engineering applications. [Method] Five implementation approaches currently utilized to achieve large capacity STATCOM were analyzed and their advantages/disadvantages were concluded,from various perspectives including capacity, efficiency, reliability, volume and cost. [Result] Principles for selecting STATCOM switchgear were proposed and the application of the principles in 35 kV ± 200 MVA cascade STATCOM switchgear selection was also presented in this paper as an example. [Conclusion] The principles can also be used as reference in large capacity STATCOM design and manufacture.
2020, 7(1): 118-123.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.019
Abstract:
[Introduction] In order to solve the problem of heavy load 220 kV transmission line loss. [Methods] Based on the development of large cross-section conductor technology and new materials, a new type of single large cross-section conductor was proposed to replace the conventional double split conductor in the heavy-duty 220 kV transmission line. The 220 kV transmission line with heavy load adopts a new type of single large section energy-saving conductor, which can greatly save power loss and reduce annual cost. [Results] Taking the 220 kV new transmission line project from Tafeng to Linwu with high transmission capacity as an example, the technical differences between the new large section single conductor and the conventional double bundle conductor in terms of electrical and mechanical characteristics are compared and analyzed, and the economy is evaluated by using the annual cost method. [Conclusion] The calculation results demonstrate the feasibility of using new large section single conductor instead of double bundle conductor in heavy load line, and provide reference for the popularization and application of large section conductor.
2020, 7(1): 124-127.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.020
Abstract:
[Introduction] In order to increase the capacity of a 220 kV transmission line, conventional conductor and various heat-resistant conductors are selected to make comprehensive comparison. [Method] This article calculated the maximum operating temperature and power loss, compared effects of mechanical load and wire sag variation on tower foundation, analyzed difficulty of construction and maintenance, and calculated investment and annual cost. [Result] The results show that all selected conductors can meet the need of increasing capacity and maximum operating temperature; towers and foundations need rebuilding if using conventional conductor; mechanical load and wire sag of heat-resistant conductors meet the design conditions of original transmission line; conventional conductor and Aluminum Conductor Multi-strand Carbon Fiber Core (ACMCC Conductor) have lower annual costs and more convenience for maintenance. [Conclusion] Our work shows that ACMCC Conductor has excellent comprehensive performance and is suitable for enhancing transmission capability of transmission lines in operation without rebuilding, especially in urban or suburban areas where it is difficult to build new towers.
2020, 7(1): 128-132.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.021
Abstract:
[Introduction] In order to manage the safety of the rapidly developing offshore wind farm projects effectively, this paper untangles the safety risks and management points of the whole process of offshore wind farm from all aspects of construction, and puts forward the corresponding measures. [Method] Based on the safety management during the implementation of the first EPC offshore wind farm project in China, this paper analyzed the risk points in the pre-survey of offshore wind farm, the installation of wind turbines and booster stations,the laying of submarine cables, and the process of debugging. This paper drawed lessons from the relevant national standards and industry specifications in marine engineering, also maked a comprehensive analysis and summary from the perspective of EPC general contractor,and focuses on the characteristics of sea conditions and defense measures against typhoons in the South China Sea. The safety management ideas summarized in this paper provide practical examples and experience for the safety management of offshore wind farm projects, which is generally accompanied by great risks. [Results] This paper also provides support for the top-level design of national and industrial standards for the safety management of offshore wind farm projects. [Conclusion] The results of this paper will strongly promote the development of wind farm resources in the South China Sea.
2020, 7(1): 133-139.
doi: 10.16516/j.gedi.issn2095-8676.2020.01.022
Abstract:
[Objective] The research on virtual power plants with multiple green energy sources is becoming a hotspot of smart grid research, but how to optimize the scheduling resources, ensure that resources to participate in the enthusiasm and sustainability,and achieving the subsidy system cost minimum, is a key problem for virtual power pricing mechanism. [Methods] Based on user flexible load, electric vehicle, energy storage, distributed power supply, analysis of participation mode and participation cost,separately set cost model according to resource and business model differences; by measuring the actual participation marginal cost of different resources, with the method of similar to the spot market clearing, according to the system load demand, adjustable resource sorting, ultimately determine the subsidy price ceiling. [Results] The pricing mechanism is used to realize the priority of users with low power economic value and great response potential from the economic point of view, to realize the reasonable distribution of power resources, to ensure that the cost of participating resources is subsidized and the system compensation cost is the smallest. [Conclusion] Based on the actual calculation, it proves that the pricing mechanism and method of this paper are accurate and effective, and can provide support for the future subsidy policy of virtual power plants.
