This work establishes a temperature-controlled sequence function, and a new multi-phase-field model, for liquid- solid-solid multi-phase transformation by coupling the liquid-solid phase transformation model with the ...This work establishes a temperature-controlled sequence function, and a new multi-phase-field model, for liquid- solid-solid multi-phase transformation by coupling the liquid-solid phase transformation model with the solid-solid phase transformation model. Taking an Fe-C alloy as an example, the continuous evolution of a multi-phase transformation is simulated by using this new model. In addition, the growth of grains affected by the grain orientation of the parent phase (generated in liquid-solid phase transformation) in the solid-solid phase transformation is studied. The results show that the morphology of ferrite grains which nucleate at the boundaries of the austenite grains is influenced by the orientation of the parent austenite grains. The growth rate of ferrite grains which nucleate at small-angle austenite grain boundaries is faster than those that nucleate at large-angle austenite grain boundaries. The difference of the growth rate of ferrites grains in different parent phase that nucleate at large-angle austenite grain boundaries, on both sides of the boundaries, is greater than that of ferrites nucleating at small-angle austenite grain boundaries.展开更多
针对电力电子变压器的非线性特性,传统PI控制的单相电力电子变压器整流级具有对参数变化敏感,响应速度慢,抗扰性能差的特点。提出了一种基于线性自抗扰控制(line active disturbance rejection control,LADRC)的电压环控制策略,该控制...针对电力电子变压器的非线性特性,传统PI控制的单相电力电子变压器整流级具有对参数变化敏感,响应速度慢,抗扰性能差的特点。提出了一种基于线性自抗扰控制(line active disturbance rejection control,LADRC)的电压环控制策略,该控制策略具有响应速度快、超调量小、鲁棒性强的特点。在仿真软件MATLAB/Simulink中通过搭建三级联H桥整流器模型进行仿真,并与传统PI控制器相比较,仿真结果表明所采用控制策略的优越性、有效性。展开更多
The Auto-Transformer Rectifier Unit(ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, t...The Auto-Transformer Rectifier Unit(ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.展开更多
12-pulse rectifier is extensively used in high power rectification, and the delta-connected autotransformer and wye-connected autotransformer are its two most popular phase-shift transformers. This paper compares the ...12-pulse rectifier is extensively used in high power rectification, and the delta-connected autotransformer and wye-connected autotransformer are its two most popular phase-shift transformers. This paper compares the 12-pulse rectifiers using the two transformers via calculating the input line current, load voltage, kVA ratings of the two autotransformer, kVA ratings of the auxiliary magnetic devices. From the viewpoint of power quality of AC mains and DC side, the two 12-pulse rectifiers are the same. The kVA rating of the IPR in the two 12-pulse rectifiers are equal, and the kVA rating of the ZSBT in the two 12-pulse rectifier are also equal to each other, under the same load power. However, the kVA of the deltaconnected autotransformer is less than that of the wyeconnected autotransformer under the same load power.Some experimental results are shown to validate the correctness of the theoretical analysis.展开更多
A new continuous multi-phase transformation field model was established for liquid-solid-eutectoid transformation. Taking Fe-C alloy as an example, the model was used to simulate the evolution of the micro-morphology ...A new continuous multi-phase transformation field model was established for liquid-solid-eutectoid transformation. Taking Fe-C alloy as an example, the model was used to simulate the evolution of the micro-morphology of the liquid-solid phase transition, and the effects of temperature, solute and free energy on the nucleation of pearlite after the liquid-solid phase transition were analyzed. The micro-morphology of pearlite was simulated. The simulation results show that the austenite structure has hereditary effect on the pearlite, the morphology of pearlite structure was similar to that of the parent austenite. The eutectoid structure at the front of pearlite grows toward the interior of austenite grains in a bifurcation manner and in the spherical coronal shape. In addition, the growth rate of pearlite was related to the shape of concave-convex interface at the nucleation site, and the growth rate at the convex interface was faster than that at the concave interface.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51661020,11504149,and 11364024)
文摘This work establishes a temperature-controlled sequence function, and a new multi-phase-field model, for liquid- solid-solid multi-phase transformation by coupling the liquid-solid phase transformation model with the solid-solid phase transformation model. Taking an Fe-C alloy as an example, the continuous evolution of a multi-phase transformation is simulated by using this new model. In addition, the growth of grains affected by the grain orientation of the parent phase (generated in liquid-solid phase transformation) in the solid-solid phase transformation is studied. The results show that the morphology of ferrite grains which nucleate at the boundaries of the austenite grains is influenced by the orientation of the parent austenite grains. The growth rate of ferrite grains which nucleate at small-angle austenite grain boundaries is faster than those that nucleate at large-angle austenite grain boundaries. The difference of the growth rate of ferrites grains in different parent phase that nucleate at large-angle austenite grain boundaries, on both sides of the boundaries, is greater than that of ferrites nucleating at small-angle austenite grain boundaries.
文摘针对电力电子变压器的非线性特性,传统PI控制的单相电力电子变压器整流级具有对参数变化敏感,响应速度慢,抗扰性能差的特点。提出了一种基于线性自抗扰控制(line active disturbance rejection control,LADRC)的电压环控制策略,该控制策略具有响应速度快、超调量小、鲁棒性强的特点。在仿真软件MATLAB/Simulink中通过搭建三级联H桥整流器模型进行仿真,并与传统PI控制器相比较,仿真结果表明所采用控制策略的优越性、有效性。
文摘The Auto-Transformer Rectifier Unit(ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.
基金supported by National Natural Science Foundation of China(No.51307034)in part by the Natural Science Foundation of Shandong Province(No.ZR2013EEQ002)
文摘12-pulse rectifier is extensively used in high power rectification, and the delta-connected autotransformer and wye-connected autotransformer are its two most popular phase-shift transformers. This paper compares the 12-pulse rectifiers using the two transformers via calculating the input line current, load voltage, kVA ratings of the two autotransformer, kVA ratings of the auxiliary magnetic devices. From the viewpoint of power quality of AC mains and DC side, the two 12-pulse rectifiers are the same. The kVA rating of the IPR in the two 12-pulse rectifiers are equal, and the kVA rating of the ZSBT in the two 12-pulse rectifier are also equal to each other, under the same load power. However, the kVA of the deltaconnected autotransformer is less than that of the wyeconnected autotransformer under the same load power.Some experimental results are shown to validate the correctness of the theoretical analysis.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.:11504149,51661020)thc Natural Scicnce Toundation of Gansu Province of China(Grant No:18JR3RA147).
文摘A new continuous multi-phase transformation field model was established for liquid-solid-eutectoid transformation. Taking Fe-C alloy as an example, the model was used to simulate the evolution of the micro-morphology of the liquid-solid phase transition, and the effects of temperature, solute and free energy on the nucleation of pearlite after the liquid-solid phase transition were analyzed. The micro-morphology of pearlite was simulated. The simulation results show that the austenite structure has hereditary effect on the pearlite, the morphology of pearlite structure was similar to that of the parent austenite. The eutectoid structure at the front of pearlite grows toward the interior of austenite grains in a bifurcation manner and in the spherical coronal shape. In addition, the growth rate of pearlite was related to the shape of concave-convex interface at the nucleation site, and the growth rate at the convex interface was faster than that at the concave interface.