The two main challenges of medium voltage direct current(MVDC)distribution network are the flexible control of power flow(PF)and fault protection.In this paper,the power flow controller(PFC)is introduced to regulate t...The two main challenges of medium voltage direct current(MVDC)distribution network are the flexible control of power flow(PF)and fault protection.In this paper,the power flow controller(PFC)is introduced to regulate the PF and inhibit the fault current during the DC fault.The coordination strategy of series-parallel PFC(SP-PFC)and hybrid DC circuit breaker(DCCB)is proposed.By regulating the polarity and magnitude of SP-PFC output voltage during the fault,the rising speed of fault current can be suppressed so as to reduce the breaking current of hybrid DCCB.The access mode of SP-PFC to the MVDC distribution network and its topology are analyzed,and the coordination strategy between SP-PFC and hybrid DCCB is investigated.Moreover,the emergency control and bypass control strategies of SP-PFC are developed.On this basis,the mathematical model of SP-PFC in different fault stages is derived.With the equivalent model of SP-PFC,the fault current of the MVDC distribution network can be calculated accurately.A simulation model of the MVDC distribution network containing SP-PFC is established in MATLAB/Simulink.The fault current calculation result is compared with the simulation result,and the effectiveness of the proposed coordination strategy is verified.展开更多
Furfural content in oil is considered as an effective parameter to evaluate the ageing state of oil-immersed transformers.In previous thermal ageing experiments at 130℃,we found that moisture increment in oil-paper s...Furfural content in oil is considered as an effective parameter to evaluate the ageing state of oil-immersed transformers.In previous thermal ageing experiments at 130℃,we found that moisture increment in oil-paper system makes more furfural distribute in oil.However,the microcosmic mechanism of moisture effect on furfural diffusion from paper to oil is still unknown,and the furfural equilibrium law at transformers'typical operating temperatures is also unclear,resulting in the unreliability of the existed furfural evaluation model.To elucidate the above problems,molecular dynamics simulation and furfural equilibrium experiments at 60℃ were carried out at different moisture contents.The results show that high moisture content makes part of furfural diffuse from paper to oil indeed.Supposing moisture content increases from 1% to 2%,mass fraction of furfural in oil may increase from 32.98% to 49.83%,leading to furfural content in oil increases from 0.76 mg/L to 1.06 mg/L when the degree of polymerisation of insulation paper is about 524,which increased by 39.5%.The increase in moisture content makes cellulose form hydrogen bonds with H_(2)O preferentially,decreasing the hydrogen bonds interaction between cellulose and furfural.Thus,partial furfural falls off cellulose and diffuses into oil,leading to an increase in furfural content in oil.To eliminate the moisture interference,a corrected furfural assessment model based on the moisture equilibrium curve has been constructed,which can accurately evaluate the ageing state of insulation paper regardless of the moisture influence.展开更多
A new route to prepare zeolitic material was introduced in this work. Compared with traditional methods, the new route showed lower energy consume. The effect of pre-treatment conditions on structure and crystalline p...A new route to prepare zeolitic material was introduced in this work. Compared with traditional methods, the new route showed lower energy consume. The effect of pre-treatment conditions on structure and crystalline phase was investigated, revealing that the mullite crystalline phase in fly ash could be converted to amorphous phase by alkali at low temperature. The removal performance of heavy metal ions on designed material was also investigated, and we found that the intermediate product showed higher adsorption capacity on Ni^(2+) than zeolite A.展开更多
The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transpor...The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transport current,in the low n value area,flux flow voltage becomes lower than in the high n value area,so that the transient characteristics strongly affect its stability.Based on those properties,we propose a new hybrid conductor which is made of low temperature superconductor(LTS) and high temperature superconductor(HTS) with concentric configuration in which the HTS coat is located outside of the LTS core.According to their power-law models,the modified adiabatic and dynamic stability criteria are qualitatively obtained by taking account into not only their critical currents but also n values.As a result,the new hybrid conductors have potential applications with higher engineering current density and improved stability.展开更多
Wireless sensor networks （WSN） provide an approachto collecting distributed monitoring data and transmiting them tothe sink node. This paper proposes a WSN-based multi-hop networkinfrastructure, to increase network ...Wireless sensor networks （WSN） provide an approachto collecting distributed monitoring data and transmiting them tothe sink node. This paper proposes a WSN-based multi-hop networkinfrastructure, to increase network lifetime by optimizing therouting strategy. First, a network model is established, an operatingcontrol strategy is devised, and energy consumption characteristicsare analyzed. Second, a fast route-planning algorithm isproposed to obtain the original path that takes into account the remainingenergy of communicating nodes and the amount of energyconsumed in data transmission. Next, considering the amount ofenergy consumed by an individual node and the entire network,a criterion function is established to describe node performanceand to evaluate data transmission ability. Finally, a route optimizingalgorithm is proposed to increase network lifetime by adjusting thetransmission route in protection of the weak node （the node withlow transmission ability）. Simulation and comparison experimentalresults demonstrate the good performance of the proposed algorithmsto increase network lifetime.展开更多
Organic photovoltaics(OPVs)suitable for application in indoor lighting environments can power a wide range of internet of things(Io T)related electronic devices.The ternary structure has huge advantages in improving t...Organic photovoltaics(OPVs)suitable for application in indoor lighting environments can power a wide range of internet of things(Io T)related electronic devices.The ternary structure has huge advantages in improving the photovoltaic performance of OPVs,including broadening the light absorption,improving the charge transport,manipulating the energy loss(E_(loss))and so on.Herein,we use wide-bandgap photo-active materials,including the benzotriazole-based polymer donor(J52-F),chlorinated polymer donor(PM7)and A_(2)-A_1-D-A_1-A_(2)-structured acceptor(BTA3),to construct ternary OPVs for indoor light applications.Benefitting from the introduction of PM7 as the third component in J52-F:BTA3-based blend,a gratifying PCE of 20.04%with a high V_(OC)of 1.00 V can be obtained under the test conditions with an illumination of 300 lx from an LED lighting source with a color temperature of 3000 K.The excellent device performance is inseparable from the matched spectrum,enhanced light absorption and the reduced E_(loss),while the improved charge transport capability and suppression of carrier recombination also play an indelible role.Our work shows a potential material system to meet the requirement of devices applied under indoor light.Moreover,these findings demonstrate that designing multi-component OPVs is indeed a feasible way to further improve the performances of the photovoltaic energy conversion system for indoor applications.展开更多
Globally, traditional power systems are rapidly transforming towards the adoption of smart grid platforms. Substations which are at the center of the electric power transformation from the power plant are changing to ...Globally, traditional power systems are rapidly transforming towards the adoption of smart grid platforms. Substations which are at the center of the electric power transformation from the power plant are changing to IEC 61850 based digital substations. Therefore, within substation, there is a growing demand for the IEC 61850 based Intelligent Electronic Devices (IEDs). The operation of multiple manufacturers of IEDs in a single digital substation network increases the need for IEC 61850 communications specification conformance diagnosis to ensure interoperability for efficient data exchange between IEDs. The IEC 61850-10 presents test items for diagnosing communication specification conformance. There are many test tools available in the market today to test the compliance of the IEC 61850 communications specifications to the IED. In this paper, we propose a model-based diagnostic method for IED communication conformance testing. The proposed model-based software therefore uses the “drag and drop” technique to select the various IEC 61850 communication services (objects) required to design the test case in a user friendly Graphical User Interface (GUI). This makes the service conformance testing more flexible for test engineers and system integrators especially in situations that require test case modifications. Also, the proposed software tool makes it easy to understand the various IEC 61850 services using the friendly GUI.展开更多
The IEC 61850 standard stipulates the Substation Configuration Description Language (SCL) file as a means to define the substation equipment, IED function and also the communication mechanism for the substation area n...The IEC 61850 standard stipulates the Substation Configuration Description Language (SCL) file as a means to define the substation equipment, IED function and also the communication mechanism for the substation area network. The SCL is an eXtensible Markup Language (XML) based file which helps to describe the configuration of the substation Intelligent Electronic Devices (IED) including their associated functions. The SCL file is also configured to contain all IED capabilities including data model which is structured into objects for easy descriptive modeling. The effective functioning of this SCL file relies on appropriate validation techniques which check the data model for errors due to non-conformity to the IEC 61850 standard. In this research, we extend the conventional SCL validation algorithm to develop a more advanced validator which can validate the standard data model using the Unified Modeling Language (UML). By using the Rule-based SCL validation tool, we implement validation test cases for a more comprehensive understanding of the various validation functionalities. It can be observed from the algorithm and the various implemented test cases that the proposed validation tool can improve SCL information validation and also help automation engineers to comprehend the IEC 61850 substation system architecture.展开更多
The digital substation system consists of an Intelligent Electronic Device (IED) which requires information for the supervision, protection, and control, as well as a client operating system for substation operation. ...The digital substation system consists of an Intelligent Electronic Device (IED) which requires information for the supervision, protection, and control, as well as a client operating system for substation operation. IEC 61850 communication standard has been defined for information exchange between heterogeneous digital devices in such substations. Currently, the Korea Electric Power Corporation (KEPCO) digital substation system uses unbuffered reporting and Generic Object Oriented Substation Events (GOOSE) communication functions for monitoring, protection and control automation. However, it is expected that the Setting Group function will be needed to operate adaptive intelligent substation system. The Setting Group function is advantageous in that it is possible to change the setting of the IED in one unified way through the client operating system, rather than changing the correction value of an IED through different manufacturer-based engineering tools. In order to utilize the Setting Group function of the IED in real substation scenario, it is necessary to test both the communication function with the host operating device and the electric functional test to ensure that correction value is properly changed. In this paper, we introduce the IEC 61850 Setting Group function, and propose a method that can integrate communication function and electrical function test of an IED conforming to the setting group functionality. We also tested the Setting Group function of the actual IED device through the proposed integrated functional test method and analyzed the results. We were able to simplify the process of testing both the electrical and communication signals in digital substations.展开更多
基金supported by the National Key Research and Development Program of China(No.2018YFB0904600)the National Natural Science Foundation of China(No.52077017)。
文摘The two main challenges of medium voltage direct current(MVDC)distribution network are the flexible control of power flow(PF)and fault protection.In this paper,the power flow controller(PFC)is introduced to regulate the PF and inhibit the fault current during the DC fault.The coordination strategy of series-parallel PFC(SP-PFC)and hybrid DC circuit breaker(DCCB)is proposed.By regulating the polarity and magnitude of SP-PFC output voltage during the fault,the rising speed of fault current can be suppressed so as to reduce the breaking current of hybrid DCCB.The access mode of SP-PFC to the MVDC distribution network and its topology are analyzed,and the coordination strategy between SP-PFC and hybrid DCCB is investigated.Moreover,the emergency control and bypass control strategies of SP-PFC are developed.On this basis,the mathematical model of SP-PFC in different fault stages is derived.With the equivalent model of SP-PFC,the fault current of the MVDC distribution network can be calculated accurately.A simulation model of the MVDC distribution network containing SP-PFC is established in MATLAB/Simulink.The fault current calculation result is compared with the simulation result,and the effectiveness of the proposed coordination strategy is verified.
基金National Natural Science Foundation of China,Grant/Award Number:52207152Opening Foundation of MOE Key Laboratory of Special Machine and High Voltage Apparatus,Grant/Award Number:KFKT202203。
文摘Furfural content in oil is considered as an effective parameter to evaluate the ageing state of oil-immersed transformers.In previous thermal ageing experiments at 130℃,we found that moisture increment in oil-paper system makes more furfural distribute in oil.However,the microcosmic mechanism of moisture effect on furfural diffusion from paper to oil is still unknown,and the furfural equilibrium law at transformers'typical operating temperatures is also unclear,resulting in the unreliability of the existed furfural evaluation model.To elucidate the above problems,molecular dynamics simulation and furfural equilibrium experiments at 60℃ were carried out at different moisture contents.The results show that high moisture content makes part of furfural diffuse from paper to oil indeed.Supposing moisture content increases from 1% to 2%,mass fraction of furfural in oil may increase from 32.98% to 49.83%,leading to furfural content in oil increases from 0.76 mg/L to 1.06 mg/L when the degree of polymerisation of insulation paper is about 524,which increased by 39.5%.The increase in moisture content makes cellulose form hydrogen bonds with H_(2)O preferentially,decreasing the hydrogen bonds interaction between cellulose and furfural.Thus,partial furfural falls off cellulose and diffuses into oil,leading to an increase in furfural content in oil.To eliminate the moisture interference,a corrected furfural assessment model based on the moisture equilibrium curve has been constructed,which can accurately evaluate the ageing state of insulation paper regardless of the moisture influence.
基金supported by the 2016 Key Program of China Guodian Corporation,and the grant number is2015G1PU00200
文摘A new route to prepare zeolitic material was introduced in this work. Compared with traditional methods, the new route showed lower energy consume. The effect of pre-treatment conditions on structure and crystalline phase was investigated, revealing that the mullite crystalline phase in fly ash could be converted to amorphous phase by alkali at low temperature. The removal performance of heavy metal ions on designed material was also investigated, and we found that the intermediate product showed higher adsorption capacity on Ni^(2+) than zeolite A.
基金supported in part by the National Natural Science Foundation of China (Grant No. 51077051)
文摘The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transport current,in the low n value area,flux flow voltage becomes lower than in the high n value area,so that the transient characteristics strongly affect its stability.Based on those properties,we propose a new hybrid conductor which is made of low temperature superconductor(LTS) and high temperature superconductor(HTS) with concentric configuration in which the HTS coat is located outside of the LTS core.According to their power-law models,the modified adiabatic and dynamic stability criteria are qualitatively obtained by taking account into not only their critical currents but also n values.As a result,the new hybrid conductors have potential applications with higher engineering current density and improved stability.
基金supported by the National Natural Science Foundation of China(61571068)the Innovative Research Projects of Colleges and Universities in Chongqing(12A19369)
文摘Wireless sensor networks （WSN） provide an approachto collecting distributed monitoring data and transmiting them tothe sink node. This paper proposes a WSN-based multi-hop networkinfrastructure, to increase network lifetime by optimizing therouting strategy. First, a network model is established, an operatingcontrol strategy is devised, and energy consumption characteristicsare analyzed. Second, a fast route-planning algorithm isproposed to obtain the original path that takes into account the remainingenergy of communicating nodes and the amount of energyconsumed in data transmission. Next, considering the amount ofenergy consumed by an individual node and the entire network,a criterion function is established to describe node performanceand to evaluate data transmission ability. Finally, a route optimizingalgorithm is proposed to increase network lifetime by adjusting thetransmission route in protection of the weak node （the node withlow transmission ability）. Simulation and comparison experimentalresults demonstrate the good performance of the proposed algorithmsto increase network lifetime.
基金supported by the National Natural Science Foundation of China(51873007,51961165102,and 21835006)the Fundamental Research Funds for the Central Universities in China(2019MS025,2018MS032,2017MS027,2017XS084)。
文摘Organic photovoltaics(OPVs)suitable for application in indoor lighting environments can power a wide range of internet of things(Io T)related electronic devices.The ternary structure has huge advantages in improving the photovoltaic performance of OPVs,including broadening the light absorption,improving the charge transport,manipulating the energy loss(E_(loss))and so on.Herein,we use wide-bandgap photo-active materials,including the benzotriazole-based polymer donor(J52-F),chlorinated polymer donor(PM7)and A_(2)-A_1-D-A_1-A_(2)-structured acceptor(BTA3),to construct ternary OPVs for indoor light applications.Benefitting from the introduction of PM7 as the third component in J52-F:BTA3-based blend,a gratifying PCE of 20.04%with a high V_(OC)of 1.00 V can be obtained under the test conditions with an illumination of 300 lx from an LED lighting source with a color temperature of 3000 K.The excellent device performance is inseparable from the matched spectrum,enhanced light absorption and the reduced E_(loss),while the improved charge transport capability and suppression of carrier recombination also play an indelible role.Our work shows a potential material system to meet the requirement of devices applied under indoor light.Moreover,these findings demonstrate that designing multi-component OPVs is indeed a feasible way to further improve the performances of the photovoltaic energy conversion system for indoor applications.
文摘Globally, traditional power systems are rapidly transforming towards the adoption of smart grid platforms. Substations which are at the center of the electric power transformation from the power plant are changing to IEC 61850 based digital substations. Therefore, within substation, there is a growing demand for the IEC 61850 based Intelligent Electronic Devices (IEDs). The operation of multiple manufacturers of IEDs in a single digital substation network increases the need for IEC 61850 communications specification conformance diagnosis to ensure interoperability for efficient data exchange between IEDs. The IEC 61850-10 presents test items for diagnosing communication specification conformance. There are many test tools available in the market today to test the compliance of the IEC 61850 communications specifications to the IED. In this paper, we propose a model-based diagnostic method for IED communication conformance testing. The proposed model-based software therefore uses the “drag and drop” technique to select the various IEC 61850 communication services (objects) required to design the test case in a user friendly Graphical User Interface (GUI). This makes the service conformance testing more flexible for test engineers and system integrators especially in situations that require test case modifications. Also, the proposed software tool makes it easy to understand the various IEC 61850 services using the friendly GUI.
文摘The IEC 61850 standard stipulates the Substation Configuration Description Language (SCL) file as a means to define the substation equipment, IED function and also the communication mechanism for the substation area network. The SCL is an eXtensible Markup Language (XML) based file which helps to describe the configuration of the substation Intelligent Electronic Devices (IED) including their associated functions. The SCL file is also configured to contain all IED capabilities including data model which is structured into objects for easy descriptive modeling. The effective functioning of this SCL file relies on appropriate validation techniques which check the data model for errors due to non-conformity to the IEC 61850 standard. In this research, we extend the conventional SCL validation algorithm to develop a more advanced validator which can validate the standard data model using the Unified Modeling Language (UML). By using the Rule-based SCL validation tool, we implement validation test cases for a more comprehensive understanding of the various validation functionalities. It can be observed from the algorithm and the various implemented test cases that the proposed validation tool can improve SCL information validation and also help automation engineers to comprehend the IEC 61850 substation system architecture.
文摘The digital substation system consists of an Intelligent Electronic Device (IED) which requires information for the supervision, protection, and control, as well as a client operating system for substation operation. IEC 61850 communication standard has been defined for information exchange between heterogeneous digital devices in such substations. Currently, the Korea Electric Power Corporation (KEPCO) digital substation system uses unbuffered reporting and Generic Object Oriented Substation Events (GOOSE) communication functions for monitoring, protection and control automation. However, it is expected that the Setting Group function will be needed to operate adaptive intelligent substation system. The Setting Group function is advantageous in that it is possible to change the setting of the IED in one unified way through the client operating system, rather than changing the correction value of an IED through different manufacturer-based engineering tools. In order to utilize the Setting Group function of the IED in real substation scenario, it is necessary to test both the communication function with the host operating device and the electric functional test to ensure that correction value is properly changed. In this paper, we introduce the IEC 61850 Setting Group function, and propose a method that can integrate communication function and electrical function test of an IED conforming to the setting group functionality. We also tested the Setting Group function of the actual IED device through the proposed integrated functional test method and analyzed the results. We were able to simplify the process of testing both the electrical and communication signals in digital substations.
