The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finit...The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.展开更多
This study analyzes the stability and reactive characteristics of the hybrid offshore wind farm that includes gridforming(GFM)and grid-following(GFL)wind turbines(WTs)integrated with a diode rectifier unit(DRU)based h...This study analyzes the stability and reactive characteristics of the hybrid offshore wind farm that includes gridforming(GFM)and grid-following(GFL)wind turbines(WTs)integrated with a diode rectifier unit(DRU)based high-voltage direct current(HVDC)system.The determination method for the proportion of GFM WTs is proposed while considering system stability and optimal offshore reactive power constraints.First,the small-signal stability is studied based on the developed linear model,and crucial factors that affect the stability are captured by eigenvalue analysis.The reactive power-frequency compensation control of GFM WTs is then proposed to improve the reactive power and frequency dynamics.Second,the relationship between offshore reactive power imbalance and the effectiveness of GFM capability is analyzed.Offshore reactive power optimization methods are next proposed to diminish offshore reactive load.These methods include the optimal design for the reactive capacity of the AC filter and the reactive power compensation control of GFL WTs.Third,in terms of stability and optimal offshore reactive power constraints,the principle and calculation method for determining the proportion of GFM WTs are proposed,and the critical proportion of GFM WTs is determined over the full active power range.Finally,case studies using a detailed model are conducted by timedomain simulations in PSCAD/EMTDC.The simulations verify the theoretical analysis results and the effectiveness of the proposed determination method for the proportion of GFM WTs and reactive power optimization methods.展开更多
基于涉网变流器开展电能质量问题治理可以有效利用变流器的剩余容量,提高治理效益,但其往往只考虑跟网型(grid-following,GFL)控制,未能充分发挥多种类变流器的调控潜力。文中基于GFL和构网型(grid-forming,GFM)涉网变流器并联系统,提...基于涉网变流器开展电能质量问题治理可以有效利用变流器的剩余容量,提高治理效益,但其往往只考虑跟网型(grid-following,GFL)控制,未能充分发挥多种类变流器的调控潜力。文中基于GFL和构网型(grid-forming,GFM)涉网变流器并联系统,提出谐波补偿、电压跌落抑制等协同控制策略。首先,介绍涉网变流器的基本控制原理及数学模型。其次,针对并联系统公共耦合点(point of common coupling,PCC)的谐波补偿问题,提出谐波分次补偿方法,增强谐波补偿的灵活性,实现谐波电流在不同容量变流单元间的合理分摊。针对PCC电压跌落问题,将并联系统状态总结为正常运行、仅GFL变流单元参与电压支撑、GFL和GFM变流单元共同支撑3种工况。经补偿容量计算和无功功率分配,PCC电压可始终保持在额定电压附近。最后,通过仿真验证所提策略的可行性与优越性。展开更多
文摘The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.
基金supported by the Research Project of China Southern Power Grid Co.,Ltd.(No.030400KK52220008(GDKJXM20220327))。
文摘This study analyzes the stability and reactive characteristics of the hybrid offshore wind farm that includes gridforming(GFM)and grid-following(GFL)wind turbines(WTs)integrated with a diode rectifier unit(DRU)based high-voltage direct current(HVDC)system.The determination method for the proportion of GFM WTs is proposed while considering system stability and optimal offshore reactive power constraints.First,the small-signal stability is studied based on the developed linear model,and crucial factors that affect the stability are captured by eigenvalue analysis.The reactive power-frequency compensation control of GFM WTs is then proposed to improve the reactive power and frequency dynamics.Second,the relationship between offshore reactive power imbalance and the effectiveness of GFM capability is analyzed.Offshore reactive power optimization methods are next proposed to diminish offshore reactive load.These methods include the optimal design for the reactive capacity of the AC filter and the reactive power compensation control of GFL WTs.Third,in terms of stability and optimal offshore reactive power constraints,the principle and calculation method for determining the proportion of GFM WTs are proposed,and the critical proportion of GFM WTs is determined over the full active power range.Finally,case studies using a detailed model are conducted by timedomain simulations in PSCAD/EMTDC.The simulations verify the theoretical analysis results and the effectiveness of the proposed determination method for the proportion of GFM WTs and reactive power optimization methods.
文摘基于涉网变流器开展电能质量问题治理可以有效利用变流器的剩余容量,提高治理效益,但其往往只考虑跟网型(grid-following,GFL)控制,未能充分发挥多种类变流器的调控潜力。文中基于GFL和构网型(grid-forming,GFM)涉网变流器并联系统,提出谐波补偿、电压跌落抑制等协同控制策略。首先,介绍涉网变流器的基本控制原理及数学模型。其次,针对并联系统公共耦合点(point of common coupling,PCC)的谐波补偿问题,提出谐波分次补偿方法,增强谐波补偿的灵活性,实现谐波电流在不同容量变流单元间的合理分摊。针对PCC电压跌落问题,将并联系统状态总结为正常运行、仅GFL变流单元参与电压支撑、GFL和GFM变流单元共同支撑3种工况。经补偿容量计算和无功功率分配,PCC电压可始终保持在额定电压附近。最后,通过仿真验证所提策略的可行性与优越性。
