Analysis of the short-circuit characteristics of SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)is very important for their practical application.This paper studies the SiC MOSFET short-circuit charact...Analysis of the short-circuit characteristics of SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)is very important for their practical application.This paper studies the SiC MOSFET short-circuit characteristics with an improved test setup under different conditions.A high-current Si insulated gate bipolar transistor is used as a circuit breaker in the test circuit rather than the usual short-circuit test conducted without a circuit breaker.The test platform with a circuit breaker does not influence the calculation results regarding the shortcircuitwithstand time and energy,but the SiCMOSFETwill switch off after failure in a very short time.In addition,the degree of failure will be limited and confined to a small area,such that the damage to the chip will be clearly observable,which is significant for short-circuit failure analysis.展开更多
In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding proce...In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding process parameters on the quality of weld forming under short-circuit transition,the design of 3 factors and 3 levels of a total of 9 groups of orthogonal tests,welding current,welding voltage,welding speed as input parameters:effective area ratio,humps,actual linear power density,aspect ratio,Vickers hardness as output paramet-ers(response targets).Using range analysis and trend charts,we can visually depict the relationship between input parameters and a single output parameter,ultimately determining the optimal process parameters that impact the single output index.Then combined with gray the-ory to transform the three response targets into a single gray relational grade(GRG)for analysis,the optimal combination of the weld mor-phology parameters as follows:welding current 100 A,welding voltage 25 V,welding speed 30 cm/min.Finally,validation experiments were conducted,and the results showed that the error between the gray relational grade and the predicted value was 2.74%.It was observed that the effective area ratio of the response target significantly improved,validating the reliability of the orthogonal gray relational method.展开更多
面向对象所具有的类、封装、继承、动态连接等特性,使得面向对象测试步骤的划分以及测试策略的选择有别于传统的测试思想.本文针对面向对象软件的特点,采用基于模型的软件测试方法,对UML(United Model Language)设计模型中的顺序图添加O...面向对象所具有的类、封装、继承、动态连接等特性,使得面向对象测试步骤的划分以及测试策略的选择有别于传统的测试思想.本文针对面向对象软件的特点,采用基于模型的软件测试方法,对UML(United Model Language)设计模型中的顺序图添加OCL(Object Constraints Language)约束,做类间交互的软件测试.本文提出执行图EG生成算法,将顺序图SD转换为执行图EG,解决UML2.0顺序图新增特性中的alt、loop、opt、break四种常见组合片段及其嵌套和多态性问题;为得到最小完备的测试路径,本文提出了EG的遍历策略和测试路径生成算法;最后,根据测试路径确定测试场景,并删除无效场景,生成测试用例.经实验验证,此方法可以基于UML顺序图与OCL约束进行系统地测试.展开更多
由于UML时序图不能够描述多态性,导致根据时序图生成的测试用例存在不足,无法测试多态性方法。提出了一种对多态性时序图的形式化及相应测试用例的生成方法。根据类约束和满意集规则确定类的多态性方法集CSPM(class sets of polymorphis...由于UML时序图不能够描述多态性,导致根据时序图生成的测试用例存在不足,无法测试多态性方法。提出了一种对多态性时序图的形式化及相应测试用例的生成方法。根据类约束和满意集规则确定类的多态性方法集CSPM(class sets of polymorphism methods),并将多态性时序图转换为多态扩展有向无环图PCOMDAG(polymorphism class object method acyclic graph)。使用提出的测试覆盖准则及深度优先算法对PCOMDAG图进行遍历,自动生成多态性时序图的测试用例。通过实例验证方法的有效性,其结果表明,本方法能够生成基于OCL约束时序图的测试用例对多态性方法进行测试,提高时序图测试集的覆盖度。展开更多
Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety perfo...Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety performance and mechanism of high-capacity lithium iron phosphate batteries under internal short-circuit challenges remain to be explored.This work analyzes the thermal runaway evolution of high-capacity LiFePO_(4) batteries under different internal heat transfer modes,which are controlled by different penetration modes.Two penetration cases involving complete penetration and incomplete penetration were detected during the test,and two modes were performed incorporating nails that either remained or were removed after penetration to comprehensively reveal the thermal runaway mechanism.A theoretical model of microcircuits and internal heat conduction is also established.The results indicated three thermal runaway evolution processes for high-capacity batteries,which corresponded to the experimental results of thermal equilibrium,single thermal runaway,and two thermal runaway events.The difference in heat distribution in the three phenomena is determined based on the microstructure and material structure near the pinhole.By controlling the heat dissipation conditions,the time interval between two thermal runaway events can be delayed from 558 to 1417 s,accompanied by a decrease in the concentration of in-situ gas production during the second thermal runaway event.展开更多
Modeling and validation of full power converter wind turbine models with field measurement data are rarely reported in papers. In this paper an aggregated generic dynamic model of the wind farm consisting of full powe...Modeling and validation of full power converter wind turbine models with field measurement data are rarely reported in papers. In this paper an aggregated generic dynamic model of the wind farm consisting of full power converter wind turbines is composed and the model validation based on actual field measurements is performed. The paper is based on the measurements obtained from the real short circuit test applied to connection point of observed wind farm. The presented approach for validating the composed model and fault ride-through （FRT） capability for the whole wind park is unique in overall practice and its significance and importance is described and analyzed.展开更多
基金This work was supported by the Shenzhen Science and Technology Program[Grant No.KQTD2017033016491218].
文摘Analysis of the short-circuit characteristics of SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)is very important for their practical application.This paper studies the SiC MOSFET short-circuit characteristics with an improved test setup under different conditions.A high-current Si insulated gate bipolar transistor is used as a circuit breaker in the test circuit rather than the usual short-circuit test conducted without a circuit breaker.The test platform with a circuit breaker does not influence the calculation results regarding the shortcircuitwithstand time and energy,but the SiCMOSFETwill switch off after failure in a very short time.In addition,the degree of failure will be limited and confined to a small area,such that the damage to the chip will be clearly observable,which is significant for short-circuit failure analysis.
基金supported by Major Special Projects of Science and Technology in Fujian Province,(Grant No.2020HZ03018)Natural Science Foundation of Fujian Province(Grant No.2020J01873).
文摘In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding process parameters on the quality of weld forming under short-circuit transition,the design of 3 factors and 3 levels of a total of 9 groups of orthogonal tests,welding current,welding voltage,welding speed as input parameters:effective area ratio,humps,actual linear power density,aspect ratio,Vickers hardness as output paramet-ers(response targets).Using range analysis and trend charts,we can visually depict the relationship between input parameters and a single output parameter,ultimately determining the optimal process parameters that impact the single output index.Then combined with gray the-ory to transform the three response targets into a single gray relational grade(GRG)for analysis,the optimal combination of the weld mor-phology parameters as follows:welding current 100 A,welding voltage 25 V,welding speed 30 cm/min.Finally,validation experiments were conducted,and the results showed that the error between the gray relational grade and the predicted value was 2.74%.It was observed that the effective area ratio of the response target significantly improved,validating the reliability of the orthogonal gray relational method.
文摘面向对象所具有的类、封装、继承、动态连接等特性,使得面向对象测试步骤的划分以及测试策略的选择有别于传统的测试思想.本文针对面向对象软件的特点,采用基于模型的软件测试方法,对UML(United Model Language)设计模型中的顺序图添加OCL(Object Constraints Language)约束,做类间交互的软件测试.本文提出执行图EG生成算法,将顺序图SD转换为执行图EG,解决UML2.0顺序图新增特性中的alt、loop、opt、break四种常见组合片段及其嵌套和多态性问题;为得到最小完备的测试路径,本文提出了EG的遍历策略和测试路径生成算法;最后,根据测试路径确定测试场景,并删除无效场景,生成测试用例.经实验验证,此方法可以基于UML顺序图与OCL约束进行系统地测试.
文摘由于UML时序图不能够描述多态性,导致根据时序图生成的测试用例存在不足,无法测试多态性方法。提出了一种对多态性时序图的形式化及相应测试用例的生成方法。根据类约束和满意集规则确定类的多态性方法集CSPM(class sets of polymorphism methods),并将多态性时序图转换为多态扩展有向无环图PCOMDAG(polymorphism class object method acyclic graph)。使用提出的测试覆盖准则及深度优先算法对PCOMDAG图进行遍历,自动生成多态性时序图的测试用例。通过实例验证方法的有效性,其结果表明,本方法能够生成基于OCL约束时序图的测试用例对多态性方法进行测试,提高时序图测试集的覆盖度。
基金supported by the National Key R&D Program of China(2021YFB2402001)the China National Postdoctoral Program for Innovative Talents(BX20220286)+1 种基金the China Postdoctoral Science Foundation(2022T150615)supported by the Youth Innovation Promotion Association CAS(Y201768)。
文摘Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety performance and mechanism of high-capacity lithium iron phosphate batteries under internal short-circuit challenges remain to be explored.This work analyzes the thermal runaway evolution of high-capacity LiFePO_(4) batteries under different internal heat transfer modes,which are controlled by different penetration modes.Two penetration cases involving complete penetration and incomplete penetration were detected during the test,and two modes were performed incorporating nails that either remained or were removed after penetration to comprehensively reveal the thermal runaway mechanism.A theoretical model of microcircuits and internal heat conduction is also established.The results indicated three thermal runaway evolution processes for high-capacity batteries,which corresponded to the experimental results of thermal equilibrium,single thermal runaway,and two thermal runaway events.The difference in heat distribution in the three phenomena is determined based on the microstructure and material structure near the pinhole.By controlling the heat dissipation conditions,the time interval between two thermal runaway events can be delayed from 558 to 1417 s,accompanied by a decrease in the concentration of in-situ gas production during the second thermal runaway event.
文摘Modeling and validation of full power converter wind turbine models with field measurement data are rarely reported in papers. In this paper an aggregated generic dynamic model of the wind farm consisting of full power converter wind turbines is composed and the model validation based on actual field measurements is performed. The paper is based on the measurements obtained from the real short circuit test applied to connection point of observed wind farm. The presented approach for validating the composed model and fault ride-through （FRT） capability for the whole wind park is unique in overall practice and its significance and importance is described and analyzed.
