With the rise of the electric vehicle industry,as the power source of electric vehicles,lithium battery has become a research hotspot.The state of charge(SOC)estimation and modelling of lithium battery are studied in ...With the rise of the electric vehicle industry,as the power source of electric vehicles,lithium battery has become a research hotspot.The state of charge(SOC)estimation and modelling of lithium battery are studied in this paper.The ampere-hour(Ah)integration method based on external characteristics is analyzed,and the open-circuit voltage(OCV)method is studied.The two methods are combined to estimate SOC.Considering the accuracy and complexity of the model,the second-order RC equivalent circuit model of lithium battery is selected.Pulse discharge and exponential fitting of lithium battery are used to obtain corresponding parameters.The simulation is carried out by using fixed resistance capacitance and variable resistance capacitor respectively.The accuracy of variable resistance and capacitance model is 2.9%,which verifies the validity of the proposed model.展开更多
Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, ...Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, such as repetition rate, magnitude and phase of discharges, which makes them not suitable for intensive studies of discharge process. Therefore, using Simulink code, we theoretically ana- lyzed and studied the classical equivalent circuits of cavity discharges, as well as the influence of circuit components on simulation results, and then proposed a novel equivalent circuit, the key parameters of which were determined according to the physical behavior of cavity discharges. In the novel equivalent circuit, the repetition rate can be changed by discharge resistance, inception and residual voltages; meanwhile the phase of discharge can be controlled by adjusting the parameters of shunt resistance. Furthermore, a controlled current source as a function of space charge is introduced in the equivalent circuit. Compared with the former ones, the simulated signals obtained by this novel model are better approximation of real signals. This work could be referred by latter studies of the characteristics and the me- chanisms of cavity discharge in oil-paper insulation.展开更多
With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performan...With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.展开更多
为持续推进国家“双碳”目标,优化储能电池的寿命和经济性,通过建立计及温度和循环次数的电池寿命模型,并结合开路电压测试、混合脉冲功率特性(hybrid pulse power characterization,HPPC)实验、充放电循环实验和日历老化实验等方法,研...为持续推进国家“双碳”目标,优化储能电池的寿命和经济性,通过建立计及温度和循环次数的电池寿命模型,并结合开路电压测试、混合脉冲功率特性(hybrid pulse power characterization,HPPC)实验、充放电循环实验和日历老化实验等方法,研究了储能电池的寿命特性及经济性优化策略。结果表明,采用全寿命周期经济等值为上层优化目标、系统日区间最优运行策略为下层优化目标的双层优化配置模型,可有效提升储能系统的经济性。在内蒙古自治区某牧区风储微电网的算例分析中,优化后风机装机功率由60 kW调整为30 kW,储能电池容量优化为1103 kW·h,储能系统总运行成本减少5.02×10^(5)元,并揭示了温度和循环次数对系统运行成本的影响规律。可见,该优化方法可在确保系统稳定运行的前提下,提升储能系统的经济性与可推广性,为储能技术的工程应用提供理论支撑。展开更多
针对高速电机和飞轮储能系统等对空间利用率要求较高的场合,提出一种新型异极径向混合磁轴承(heteropolar radial hybrid magnetic bearing,HRHMB).首先,建立该磁轴承的等效磁路模型,通过解析磁场得出其电流刚度、位移刚度及电磁力,并...针对高速电机和飞轮储能系统等对空间利用率要求较高的场合,提出一种新型异极径向混合磁轴承(heteropolar radial hybrid magnetic bearing,HRHMB).首先,建立该磁轴承的等效磁路模型,通过解析磁场得出其电流刚度、位移刚度及电磁力,并通过有限元仿真验证其有效性;然后,在相同约束条件下与传统偏置磁轴承进行对比,分析磁轴承的刚度特性和空间利用率;最后,通过有限元仿真研究新型磁轴承径向两自由度间的电磁力耦合,并与传统磁轴承进行对比.研究结果表明:在相同承载力等约束条件下,该新型磁轴承的体积仅为传统磁轴承的0.87倍,其电磁力在控制电流和转子位移影响下的相对误差值为6.5%,而传统磁轴承的电磁力相对误差为13.6%,表明新型磁轴承径向两自由度的电磁力耦合小于传统磁轴承,解耦效果良好.展开更多
中压配电网中的部分瞬时故障在发展为永久故障之前可能会多次发生,而准确辨识这类重复发生的瞬时故障有助于实现故障预警、减少永久性故障的发生并且提高供电可靠性。通过建立瞬时故障的暂态等值电路并对其故障电流进行分析,表明重复性...中压配电网中的部分瞬时故障在发展为永久故障之前可能会多次发生,而准确辨识这类重复发生的瞬时故障有助于实现故障预警、减少永久性故障的发生并且提高供电可靠性。通过建立瞬时故障的暂态等值电路并对其故障电流进行分析,表明重复性瞬时故障在发展为永久性故障的过程中,故障电流具有强相似性。文中提出了一种基于零序电流波形相似度的重复性瞬时故障辨识方法。采用改进动态时间规划(dynamic time warping,DTW)算法计算零序电流的近似波形和暂态波形序列间的距离。而后通过DTW距离获得波形相似度,实现重复性瞬时故障的辨识。通过大量PSCAD/EMTDC仿真数据以及现场实测数据,验证了所提辨识算法在多种影响因素下的准确性和有效性。展开更多
基金Project(51507073)supported by the National Natural Science Foundation of China。
文摘With the rise of the electric vehicle industry,as the power source of electric vehicles,lithium battery has become a research hotspot.The state of charge(SOC)estimation and modelling of lithium battery are studied in this paper.The ampere-hour(Ah)integration method based on external characteristics is analyzed,and the open-circuit voltage(OCV)method is studied.The two methods are combined to estimate SOC.Considering the accuracy and complexity of the model,the second-order RC equivalent circuit model of lithium battery is selected.Pulse discharge and exponential fitting of lithium battery are used to obtain corresponding parameters.The simulation is carried out by using fixed resistance capacitance and variable resistance capacitor respectively.The accuracy of variable resistance and capacitance model is 2.9%,which verifies the validity of the proposed model.
基金Project supported by National Basic Research Program of China(973 Program) (2012CB215205)Fund for Innovative Research Groups of China (51021005)
文摘Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, such as repetition rate, magnitude and phase of discharges, which makes them not suitable for intensive studies of discharge process. Therefore, using Simulink code, we theoretically ana- lyzed and studied the classical equivalent circuits of cavity discharges, as well as the influence of circuit components on simulation results, and then proposed a novel equivalent circuit, the key parameters of which were determined according to the physical behavior of cavity discharges. In the novel equivalent circuit, the repetition rate can be changed by discharge resistance, inception and residual voltages; meanwhile the phase of discharge can be controlled by adjusting the parameters of shunt resistance. Furthermore, a controlled current source as a function of space charge is introduced in the equivalent circuit. Compared with the former ones, the simulated signals obtained by this novel model are better approximation of real signals. This work could be referred by latter studies of the characteristics and the me- chanisms of cavity discharge in oil-paper insulation.
基金Project Supported by National Development and Reform Commission(No.[2006]2709)
文摘With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.
文摘针对高速电机和飞轮储能系统等对空间利用率要求较高的场合,提出一种新型异极径向混合磁轴承(heteropolar radial hybrid magnetic bearing,HRHMB).首先,建立该磁轴承的等效磁路模型,通过解析磁场得出其电流刚度、位移刚度及电磁力,并通过有限元仿真验证其有效性;然后,在相同约束条件下与传统偏置磁轴承进行对比,分析磁轴承的刚度特性和空间利用率;最后,通过有限元仿真研究新型磁轴承径向两自由度间的电磁力耦合,并与传统磁轴承进行对比.研究结果表明:在相同承载力等约束条件下,该新型磁轴承的体积仅为传统磁轴承的0.87倍,其电磁力在控制电流和转子位移影响下的相对误差值为6.5%,而传统磁轴承的电磁力相对误差为13.6%,表明新型磁轴承径向两自由度的电磁力耦合小于传统磁轴承,解耦效果良好.
文摘中压配电网中的部分瞬时故障在发展为永久故障之前可能会多次发生,而准确辨识这类重复发生的瞬时故障有助于实现故障预警、减少永久性故障的发生并且提高供电可靠性。通过建立瞬时故障的暂态等值电路并对其故障电流进行分析,表明重复性瞬时故障在发展为永久性故障的过程中,故障电流具有强相似性。文中提出了一种基于零序电流波形相似度的重复性瞬时故障辨识方法。采用改进动态时间规划(dynamic time warping,DTW)算法计算零序电流的近似波形和暂态波形序列间的距离。而后通过DTW距离获得波形相似度,实现重复性瞬时故障的辨识。通过大量PSCAD/EMTDC仿真数据以及现场实测数据,验证了所提辨识算法在多种影响因素下的准确性和有效性。
