Characters of head of low head pump station and the pump shaft power areanalyzed. Influence of each single factor on pump shaft power is expressed as change of specificshaft power. (non-dimensional) and the probabilit...Characters of head of low head pump station and the pump shaft power areanalyzed. Influence of each single factor on pump shaft power is expressed as change of specificshaft power. (non-dimensional) and the probability density function is determined. Influences ofmultiple factors on pump shaft power are analyzed. Method of calculating none over-loadedprobability of motor by integration by successive reductions is put forward and then relationbetween power spare coefficient and none over-loaded reliability of electric motor is established.Influences of all factors on pump shaft power being considered completely; power spare coefficientsof motor are calculated in three kinds of heads (changing and unchanging), two kinds of dirty-outconditions. Electrical motor power spare coefficients should be chosen as 1.20 approx 1.44, 1.11approx 1.19, 1.09 approx.14 respectively when pump heads are 4, 7, 9.5 m. The results mean much toreasonable choose of electrical motors in large pump stations, increasing reliability of pump unitsand saving equipment investment.展开更多
The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and s...The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and some innovations on the theory and engineering technique have been realized.They have been applied to rolling mills,mine hoists,and so on,and remarkable economic and social benefit has been achieved.The development of AC drive fed by large power IGCT(integrated gate commutated thyristors)AC-DC-AC converter is also introduced.It has excellent performance and reliable operation,and has been used in traction.展开更多
A new 300 MVA/1350 MJ motor generator （MG） will be built to feed all of the poloidal field power supplies （PFPS） and auxiliary heating power supplies of the HL-2M tokamak. The MG has a vertical-shaft salient pole ...A new 300 MVA/1350 MJ motor generator （MG） will be built to feed all of the poloidal field power supplies （PFPS） and auxiliary heating power supplies of the HL-2M tokamak. The MG has a vertical-shaft salient pole 6-phase synchronous generator and a coaxial 8500 kW induction motor. The Ohmic heating power supply （OHPS） consisting of 4-quadrant DC pulsed convertor is the one with the highest parameters among the PFPS. Therefore, the match between the generator and the OHPS is very important. The matching study with Matlab/Simulink is described in this paper. The simulation results show that the subtransient reactance of the generator is closely related to the inversion operation of the OHPS. By setting various subtransient reactance in the simulation generator model and considering the cost reduction, the optimized parameters are obtained as xd＂ = 0.405 p.u. at 100 Hz for the generator. The models built in the simulation can be used as an important tool for studying the dynamic characteristics and the control strategy of other HL-2M PFPSes.展开更多
This paper reports the converter topologies which are employed for better Power Factor Correction at the input side. The Power Factor Correction is an important factor when considering the Power Quality. Based on the ...This paper reports the converter topologies which are employed for better Power Factor Correction at the input side. The Power Factor Correction is an important factor when considering the Power Quality. Based on the converter topologies, the Bridgeless converters are preferred in order to reduce the number of switching devices, losses associated with it and improve the Power Quality further more. This paper investigates about the Power Factor performances and conduction losses of the Bridgeless Power Factor Corrector Converters which see through the benefits and limitations by analyzing the Bridgeless Buck-Boost Converter, Bridgeless SEPIC converter and Bridgeless CUK converter. The resultant voltage is fed to the BLDC motor which is rapidly replacing the Induction motor for its better operating characteristics. These strategies are being analyzed using the MATLAB/Simulink software and the results are verified through the experimental analysis. The converter choice is preferred through the performance characteristics and Power Factor Correction at the supply. The Power Factor obtained should be within the acceptable limits under IEC 61000-3-2 standards.展开更多
We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement w...We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement with the experimental data. Our study not only reveals that the maximum efficiency depends on elasticity and is independent of transition rates but also indicates that the parameters fitted to fast muscle are different from those fitted to a slow one. The latter may imply that the structure of the fast muscle is different from that of the slow one. The main reason that our model succeeds is that velocity in this model is an independent variable.展开更多
In industries DC motor drives are very essential due to their high performance applications such as its reliability, ease of control, low cost and simplicity. And speed control of these motors is very easy due to powe...In industries DC motor drives are very essential due to their high performance applications such as its reliability, ease of control, low cost and simplicity. And speed control of these motors is very easy due to power electronic AC-DC converters. These power electronic converters are with prominent low power factor and higher Total Harmonic Distortion (THD). These converters operate only for short time resulting non-sinusoidal waveform. This problem of harmonic distortion can be mitigated by reshaping the non-sinusoidal waveform to pure sine wave. Different wave shaping techniques have been developed by using different filters among which one is tuned passive filter. This paper proposed power factor improvement and harmonic mitigation of AC-DC converters based on separately excited DC motor using tuned passive filter. In this context experimental model is designed and results are analyzed by power quality analyzer.展开更多
Dynamic equivalence can not only largely reduce the system size and the computation time but also stress the dominant features of the system [1]-[3]. This paper firstly recommends the basic concept of dynamic equivale...Dynamic equivalence can not only largely reduce the system size and the computation time but also stress the dominant features of the system [1]-[3]. This paper firstly recommends the basic concept of dynamic equivalent and the status of both domestic and abroad development in this area. The most existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors. In addition, the existing polymerization method which is based on the frequency domain algorithm of induction electric machines parameters takes a long time to equivalent for the large system, then the new method based on the weighted is proposed. Then, the basic steps for dynamic equivalence with the weighted method are introduced as follows. At first, the clustering criterion of motor loads based on time domain simulation is given. The motors with similar dynamic characteristics are classified into one group. Then, the simplication of the buses of motors in same group and network is carried out. Finally, parameters of the equivalent motor are calculated and the equivalent system is thus obtained based on the weighted. This aggregation method is applied to the simple distribution system of 4 generators. Simulation results show that the method can quickly obtain polymerization parameters of generator groups and the aggregation model retains the dynamic performance of the original model with good accuracy, the active and reactive power fitting error is smaller as well.展开更多
针对电网电压不平衡下电流平衡及功率恒定问题,提出改进型光储虚拟同步发电机(virtual synchronous generator,VSG)控制策略,该策略通过引入虚拟阻抗技术和双二阶广义积分器(double second order generalized integrator,DSOGI)实现正...针对电网电压不平衡下电流平衡及功率恒定问题,提出改进型光储虚拟同步发电机(virtual synchronous generator,VSG)控制策略,该策略通过引入虚拟阻抗技术和双二阶广义积分器(double second order generalized integrator,DSOGI)实现正负序分量的有效分离,并基于瞬时功率理论优化电流和功率的协调控制,显著提高了系统在不平衡电网条件下的电流平衡性和功率稳定性。首先,构建基于电机瞬态模型的光伏储能VSG系统的数学模型,以深入理解和模拟VSG在实际电网中的动态行为。通过应用双二阶广义积分器技术,实现了正序与负序分量的有效分离,并基于瞬时功率理论和负序虚拟复阻抗技术,进一步实现电流和功率的协调控制,确保电流平衡及功率恒定。最后,利用MATLA/Simulink软件构建仿真模型,模拟光伏储能系统在不平衡电网状态下的运行情况,仿真结果表明所提控制策略显著提高了控制策略的精度和响应速度,可确保动态电网环境中的操作效率和可靠性。展开更多
The heating calculation of three-phase squirrel- cage asynchronous motor on the condition of starting for a prescribed rotary angle is firstly studied with time dissection method and its corresponding algorithm is pro...The heating calculation of three-phase squirrel- cage asynchronous motor on the condition of starting for a prescribed rotary angle is firstly studied with time dissection method and its corresponding algorithm is provided. Then based upon the algorithm, a new method for motor power selection is established. Motor initial power determined by load power ischecked and modified in terms of time crit erion, heating criterion,and starting torque criterion.An appropriate motor power which meets three criterions is obtained at last, in the meantime, working displacement matrix andfrequency matrix used for control are acquired. Lifting motor of MDJ1800 low-level high- speed palletizer is taken as a reaI case in the paper.展开更多
文摘Characters of head of low head pump station and the pump shaft power areanalyzed. Influence of each single factor on pump shaft power is expressed as change of specificshaft power. (non-dimensional) and the probability density function is determined. Influences ofmultiple factors on pump shaft power are analyzed. Method of calculating none over-loadedprobability of motor by integration by successive reductions is put forward and then relationbetween power spare coefficient and none over-loaded reliability of electric motor is established.Influences of all factors on pump shaft power being considered completely; power spare coefficientsof motor are calculated in three kinds of heads (changing and unchanging), two kinds of dirty-outconditions. Electrical motor power spare coefficients should be chosen as 1.20 approx 1.44, 1.11approx 1.19, 1.09 approx.14 respectively when pump heads are 4, 7, 9.5 m. The results mean much toreasonable choose of electrical motors in large pump stations, increasing reliability of pump unitsand saving equipment investment.
文摘The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and some innovations on the theory and engineering technique have been realized.They have been applied to rolling mills,mine hoists,and so on,and remarkable economic and social benefit has been achieved.The development of AC drive fed by large power IGCT(integrated gate commutated thyristors)AC-DC-AC converter is also introduced.It has excellent performance and reliable operation,and has been used in traction.
文摘A new 300 MVA/1350 MJ motor generator （MG） will be built to feed all of the poloidal field power supplies （PFPS） and auxiliary heating power supplies of the HL-2M tokamak. The MG has a vertical-shaft salient pole 6-phase synchronous generator and a coaxial 8500 kW induction motor. The Ohmic heating power supply （OHPS） consisting of 4-quadrant DC pulsed convertor is the one with the highest parameters among the PFPS. Therefore, the match between the generator and the OHPS is very important. The matching study with Matlab/Simulink is described in this paper. The simulation results show that the subtransient reactance of the generator is closely related to the inversion operation of the OHPS. By setting various subtransient reactance in the simulation generator model and considering the cost reduction, the optimized parameters are obtained as xd＂ = 0.405 p.u. at 100 Hz for the generator. The models built in the simulation can be used as an important tool for studying the dynamic characteristics and the control strategy of other HL-2M PFPSes.
文摘This paper reports the converter topologies which are employed for better Power Factor Correction at the input side. The Power Factor Correction is an important factor when considering the Power Quality. Based on the converter topologies, the Bridgeless converters are preferred in order to reduce the number of switching devices, losses associated with it and improve the Power Quality further more. This paper investigates about the Power Factor performances and conduction losses of the Bridgeless Power Factor Corrector Converters which see through the benefits and limitations by analyzing the Bridgeless Buck-Boost Converter, Bridgeless SEPIC converter and Bridgeless CUK converter. The resultant voltage is fed to the BLDC motor which is rapidly replacing the Induction motor for its better operating characteristics. These strategies are being analyzed using the MATLAB/Simulink software and the results are verified through the experimental analysis. The converter choice is preferred through the performance characteristics and Power Factor Correction at the supply. The Power Factor obtained should be within the acceptable limits under IEC 61000-3-2 standards.
基金Project supported by the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.Y7Y1472Y61)the National Natural Science Foundation of China(Grant Nos.11205123,11574329,11774358,11747601,and 11675017)+3 种基金the Joint NSFC–ISF Research Program(Grant No.51561145002)the CAS Biophysics Interdisciplinary Innovation Team Project(Grant No.2060299)the CAS Strategic Priority Research Program(Grant No.XDA17010504)the Fundamental Research Funds for the Central Universities(Grant No.2017EYT24)
文摘We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement with the experimental data. Our study not only reveals that the maximum efficiency depends on elasticity and is independent of transition rates but also indicates that the parameters fitted to fast muscle are different from those fitted to a slow one. The latter may imply that the structure of the fast muscle is different from that of the slow one. The main reason that our model succeeds is that velocity in this model is an independent variable.
文摘In industries DC motor drives are very essential due to their high performance applications such as its reliability, ease of control, low cost and simplicity. And speed control of these motors is very easy due to power electronic AC-DC converters. These power electronic converters are with prominent low power factor and higher Total Harmonic Distortion (THD). These converters operate only for short time resulting non-sinusoidal waveform. This problem of harmonic distortion can be mitigated by reshaping the non-sinusoidal waveform to pure sine wave. Different wave shaping techniques have been developed by using different filters among which one is tuned passive filter. This paper proposed power factor improvement and harmonic mitigation of AC-DC converters based on separately excited DC motor using tuned passive filter. In this context experimental model is designed and results are analyzed by power quality analyzer.
文摘Dynamic equivalence can not only largely reduce the system size and the computation time but also stress the dominant features of the system [1]-[3]. This paper firstly recommends the basic concept of dynamic equivalent and the status of both domestic and abroad development in this area. The most existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors. In addition, the existing polymerization method which is based on the frequency domain algorithm of induction electric machines parameters takes a long time to equivalent for the large system, then the new method based on the weighted is proposed. Then, the basic steps for dynamic equivalence with the weighted method are introduced as follows. At first, the clustering criterion of motor loads based on time domain simulation is given. The motors with similar dynamic characteristics are classified into one group. Then, the simplication of the buses of motors in same group and network is carried out. Finally, parameters of the equivalent motor are calculated and the equivalent system is thus obtained based on the weighted. This aggregation method is applied to the simple distribution system of 4 generators. Simulation results show that the method can quickly obtain polymerization parameters of generator groups and the aggregation model retains the dynamic performance of the original model with good accuracy, the active and reactive power fitting error is smaller as well.
文摘针对电网电压不平衡下电流平衡及功率恒定问题,提出改进型光储虚拟同步发电机(virtual synchronous generator,VSG)控制策略,该策略通过引入虚拟阻抗技术和双二阶广义积分器(double second order generalized integrator,DSOGI)实现正负序分量的有效分离,并基于瞬时功率理论优化电流和功率的协调控制,显著提高了系统在不平衡电网条件下的电流平衡性和功率稳定性。首先,构建基于电机瞬态模型的光伏储能VSG系统的数学模型,以深入理解和模拟VSG在实际电网中的动态行为。通过应用双二阶广义积分器技术,实现了正序与负序分量的有效分离,并基于瞬时功率理论和负序虚拟复阻抗技术,进一步实现电流和功率的协调控制,确保电流平衡及功率恒定。最后,利用MATLA/Simulink软件构建仿真模型,模拟光伏储能系统在不平衡电网状态下的运行情况,仿真结果表明所提控制策略显著提高了控制策略的精度和响应速度,可确保动态电网环境中的操作效率和可靠性。
基金This project is supported by National 863 Foundation (863-512-9801-06)
文摘The heating calculation of three-phase squirrel- cage asynchronous motor on the condition of starting for a prescribed rotary angle is firstly studied with time dissection method and its corresponding algorithm is provided. Then based upon the algorithm, a new method for motor power selection is established. Motor initial power determined by load power ischecked and modified in terms of time crit erion, heating criterion,and starting torque criterion.An appropriate motor power which meets three criterions is obtained at last, in the meantime, working displacement matrix andfrequency matrix used for control are acquired. Lifting motor of MDJ1800 low-level high- speed palletizer is taken as a reaI case in the paper.
