The response of a bipolar transistor （BJT） under a square-wave electromagnetic pulse （EMP） with different injecting voltages is investigated. Adopting the curve fitting method, the relationship between the burnout...The response of a bipolar transistor （BJT） under a square-wave electromagnetic pulse （EMP） with different injecting voltages is investigated. Adopting the curve fitting method, the relationship between the burnout time, the damage energy and the injecting voltage is obtained. Research shows that the damage energy is not a constant value, but changes with the injecting voltage level. By use of the device simulator Medici, the internal behavior of the burned device is analyzed. Simulation results indicate that the variation of the damage energy with injecting voltage is caused by the distribution change of hot spot position under different injection levels. Therefore, the traditional way to evaluate the trade-off between the burnout time and the injecting voltage is not comprehensive due to the variation of the damage energy.展开更多
In this paper,a model of a large-scale optimal power flow(OPF)under voltage grading and network partition and its algorithm is presented.Based on the principles of open loop operations,the node injecting current metho...In this paper,a model of a large-scale optimal power flow(OPF)under voltage grading and network partition and its algorithm is presented.Based on the principles of open loop operations,the node injecting current method is used to divide the large-scale power grid into voltage grading and district dividing structures.The power network is further divided into a high-voltage main network and several subnets according to voltage levels of 220 kV.The subnets are connected by means of boundary nodes,and the partition model is solved using the improved approximate Newton direction method,which achieves complete dynamic decoupling simply by exchanging boundary variables between the main network and the subnets.A largescale power grid thus is decomposed into many subnets,making the solution of the problem simpler and faster while helping to protect the information of individual subnets.The system is tested for correctness and effectiveness of the proposed model,and the results obtained are matched in real-time.Finally,the algorithm is seen to have good convergence while improving calculation speed.展开更多
重点分析了静态同步串联补偿器(Static Synchronous Series Compensator,SSSC)向系统注入的电压及串补线路保护安装处的测量电压的谐波成分,并研究了SSSC安装位置和注入电压大小不同时其注入电压所产生的谐波对测量电压的影响程度。研...重点分析了静态同步串联补偿器(Static Synchronous Series Compensator,SSSC)向系统注入的电压及串补线路保护安装处的测量电压的谐波成分,并研究了SSSC安装位置和注入电压大小不同时其注入电压所产生的谐波对测量电压的影响程度。研究结果表明,SSSC注入电压的主要谐波成分与载波比有关,若载波比为27,则主要含有25次和29次谐波,并且在SSSC注入电压的各种谐波分量中,25次谐波对测量电压的影响最大,特别是当SSSC安装在线路中间时,测量电压的25次谐波含量较大,且随着SSSC注入电压的增大而增大。展开更多
With the power grid load increasing, the problem of grid voltage stability is increasingly prominent, and the possibility of voltage instability is also growing. In order to improve the voltage stability, this paper a...With the power grid load increasing, the problem of grid voltage stability is increasingly prominent, and the possibility of voltage instability is also growing. In order to improve the voltage stability, this paper analyzed how the voltage stability was influenced by different reactive power injection based on the simplified L-indicator of on-line voltage stability monitoring. According to the basic differential property of the simplified L-indicator, a general and normative analytical algorithm about reactive power optimization was deduced. The analytical algorithm can calculate the load node injected reactive power, and then the network can run in the optimal steady state on the basis of the calculation results. According to the simulation results of IEEE-14, IEEE-30, IEEE-57 and IEEE-118, the feasibility and effectiveness of the proposed algorithm to improve voltage stability and reduce the risk of grid collapse were verified.展开更多
分析了三电平中点箝位(Neutral Point Clamping,简称NPC)逆变器的中点电位平衡问题,讨论了通过注入零序电压实现中点电位控制的载波PWM方法,并在此基础上对一种实时控制中点电位平衡的方法进行了改进,提出一种基于零序电压注入的载波交...分析了三电平中点箝位(Neutral Point Clamping,简称NPC)逆变器的中点电位平衡问题,讨论了通过注入零序电压实现中点电位控制的载波PWM方法,并在此基础上对一种实时控制中点电位平衡的方法进行了改进,提出一种基于零序电压注入的载波交叠PWM方法。仿真及实验结果验证了该方法良好的中点电位控制能力及输出电压谐波特性。展开更多
基金supported by the National Natural Science Foundation of China(No.60776034).
文摘The response of a bipolar transistor （BJT） under a square-wave electromagnetic pulse （EMP） with different injecting voltages is investigated. Adopting the curve fitting method, the relationship between the burnout time, the damage energy and the injecting voltage is obtained. Research shows that the damage energy is not a constant value, but changes with the injecting voltage level. By use of the device simulator Medici, the internal behavior of the burned device is analyzed. Simulation results indicate that the variation of the damage energy with injecting voltage is caused by the distribution change of hot spot position under different injection levels. Therefore, the traditional way to evaluate the trade-off between the burnout time and the injecting voltage is not comprehensive due to the variation of the damage energy.
基金supported by National Basic Research Program of China(973 Program)under Grant 2013CB228205National Natural Science Foundation of China under Grant 51541707.
文摘In this paper,a model of a large-scale optimal power flow(OPF)under voltage grading and network partition and its algorithm is presented.Based on the principles of open loop operations,the node injecting current method is used to divide the large-scale power grid into voltage grading and district dividing structures.The power network is further divided into a high-voltage main network and several subnets according to voltage levels of 220 kV.The subnets are connected by means of boundary nodes,and the partition model is solved using the improved approximate Newton direction method,which achieves complete dynamic decoupling simply by exchanging boundary variables between the main network and the subnets.A largescale power grid thus is decomposed into many subnets,making the solution of the problem simpler and faster while helping to protect the information of individual subnets.The system is tested for correctness and effectiveness of the proposed model,and the results obtained are matched in real-time.Finally,the algorithm is seen to have good convergence while improving calculation speed.
文摘重点分析了静态同步串联补偿器(Static Synchronous Series Compensator,SSSC)向系统注入的电压及串补线路保护安装处的测量电压的谐波成分,并研究了SSSC安装位置和注入电压大小不同时其注入电压所产生的谐波对测量电压的影响程度。研究结果表明,SSSC注入电压的主要谐波成分与载波比有关,若载波比为27,则主要含有25次和29次谐波,并且在SSSC注入电压的各种谐波分量中,25次谐波对测量电压的影响最大,特别是当SSSC安装在线路中间时,测量电压的25次谐波含量较大,且随着SSSC注入电压的增大而增大。
文摘With the power grid load increasing, the problem of grid voltage stability is increasingly prominent, and the possibility of voltage instability is also growing. In order to improve the voltage stability, this paper analyzed how the voltage stability was influenced by different reactive power injection based on the simplified L-indicator of on-line voltage stability monitoring. According to the basic differential property of the simplified L-indicator, a general and normative analytical algorithm about reactive power optimization was deduced. The analytical algorithm can calculate the load node injected reactive power, and then the network can run in the optimal steady state on the basis of the calculation results. According to the simulation results of IEEE-14, IEEE-30, IEEE-57 and IEEE-118, the feasibility and effectiveness of the proposed algorithm to improve voltage stability and reduce the risk of grid collapse were verified.
文摘分析了三电平中点箝位(Neutral Point Clamping,简称NPC)逆变器的中点电位平衡问题,讨论了通过注入零序电压实现中点电位控制的载波PWM方法,并在此基础上对一种实时控制中点电位平衡的方法进行了改进,提出一种基于零序电压注入的载波交叠PWM方法。仿真及实验结果验证了该方法良好的中点电位控制能力及输出电压谐波特性。
