链式STATCOM直流侧电压平衡控制策略探讨

随着链式STATCOM成为高压、大容量STATCOM的主流发展方向,链式STATCOM直流侧电容电压难以平衡的问题得到了更深入的研究,其控制策略正逐步完善.本文综合现有文献分析了导致直流侧电容电压不平衡的原因,归纳了最新的较为完善的控制策略,并给出了相关意见,为链式STATCOM的进一步研究提供参考.     

一种新型的三电平逆变器中点电压平衡控制策略

三电平逆变器中直流侧中点电容电压平衡问题直接影响着逆变器及其电机调速系统的可靠性。文章首先介绍了三电平逆变器的SVPWM算法；在此基础上，提出采用动态调整正负空间电压矢量作用时间的方法来实现中点电位平衡，并作了具体的阐述。理论分析和仿真结果表明，此方法能有效地平衡三电平逆变器的中点电压。     

一种改进式三电平逆变器SVPWM控制技术研究

在介绍三电平逆变器基础上,研究了三电平逆变器空间电压矢量二(space vector pulse width modulation,SVPWM)控制,分析了三电平逆变器电压矢量分布情况和直流侧电容中点电位偏移原因.根据SVPWM控制规律,提出了一种基于矢量合成抑制中点电位偏移的SVPWM方法:利用合成矢量在采用周期内向中点注入电流为零,实现中点电位平衡.通过仿真分析,验证了抑制中点电位偏移控制策略的实用性和可行性.实验证明,三电平逆变器中点电位偏移能够被有效抑制,并且具有输出谐波含量低、输出波形好的特性,适合应用于高压大功率变流系统.     

基于矢量调制的维也纳整流器共模电压抑制研究

针对维也纳整流器的安全可靠问题,对维也纳整流器的共模电压高和中点不平衡等方面进行了研究,提出了一种矢量调制方法以及时实现共模电压减少以及直流侧电压平衡控制。首先分析了共模电压产生的原因,通过提出的矢量调制减少了共模电压;然后分析了中点平衡产生的原因,通过所提出的矢量调制同时实现了中点平衡控制;利用维也纳整流器试验台对维也纳整流器的中点平衡控制和共模电压抑制效果进行了测试。研究结果表明:维也纳整流器的共模电压能够有效地得到抑制,而且维也纳整流器的线电压为标准的五电平波形,直流侧电容电压得到有效控制,输入电流的畸变率得到有效控制。     

三电平NPC逆变器中点电位平衡控制研究

介绍了三电平中点箝位型(NPC)逆变器的拓扑结构,分析了空间矢量脉宽调制(SVPWM)的基本原理.针对直流侧电压平衡控制问题,研究了基于中点电荷预估控制的平衡控制策略,并基于MATLAB进行了仿真研究.仿真结果验证了该方法的有效性.     

基于三相四开关AC-DC变换器直流侧电容电压平衡的FCS-MPC策略

三相四开关AC-DC变换器由于开关数量的减少,容易导致直流侧电容电压不平衡,系统的稳定性降低等。为了解决这些问题,提出了三相四开关AC-DC变换器直流侧电容电压平衡的有限控制集模型预测控制(Finite-control-set model predictive control, FCS-MPC)。在该策略中,为了方便计算,建立了坐标系下的系统模型,再通过建立代价函数对所有电压矢量进行评估,整个过程不需要锁相环,也不需要复杂的调制策略。在建立的新的代价函数中,加入了抑制电容电压波动的目标项,消除了电容中性点电压的偏移,提高了系统的可靠性。仿真结果表明,所提策略能使电容电压保持平衡,且具有良好的动、静态性能。     

升压型混合式九电平有源中点钳位逆变器研究

研究了一种适用于低压场合的升压型混合式九电平有源中点钳位逆变器。该逆变器每相由一个T-type三电平单元和一个有源中点钳位三电平单元组成。分析了该逆变器的工作原理与各种工作模态。与传统的九电平逆变器相比,该逆变器具有更少的开关器件和直流电压源,同时可以达到更高的效率。分析了悬浮电容和直流母线电容的电压平衡问题,提出了相应的解决方案。通过实验和仿真,该拓扑的可行性和优点得到了验证。     

基于能量平衡思想的直流侧APF的分析与设计

直流侧APF电容电压反映了输出有功功率的变化,根据能量守恒原理提出了一种基于能量平衡的直流侧有源电力滤波器控制方法,省去了补偿电流参考指令的复杂计算,比传统的桥式逆变器组成的APF控制方法简单,节省功率开关器件.阐述了该方法的原理,分析设计了APF控制系统电流环、电压环控制器,并用MATLAB对该方法进行了动态仿真研究,进一步验证了谐波控制方法的正确性和有效性.     

二极管箝位多电平动态电压恢复器的控制与调制

为解决级联多电平动态电压恢复器(DVR)用于提高配网电压质量时需要多个整流单元的问题,提出了一种基于二极管箝位五电平逆变器的三相DVR方案。相较于普通级联型DVR,该三相DVR在输出电平数增加时只需一个整流单元,就可以达到减少整流单元开关器件的目的。同时,采用比例谐振控制(PR)算法,保证了逆变器输出电压的实时跟踪与谐波补偿。最后,在PSIM中搭建了仿真平台进行验证,仿真结果表明,所提策略用于三相三线10 kV配网系统的电压质量治理是可行的。     

基于前馈解耦的VIENNA整流器矢量控制研究

在详细分析VIENNA三电平整流器工作机理的基础上,引入平均功率的dq前馈解耦控制策略,有效消除了dq间耦合作用,提出了基于SVPWM控制策略下利用直流侧电压与单比例系数实时修正占空比实现直流侧母线中点电位的有效补偿机制,给出了详细的理论分析与PI控制器设计原则,同时构建了完整的三相三线制VIENNA整流器仿真模型与实验平台。仿真实验结果表明,文中设计的控制系统响应速度快,调节范围宽,输出电压纹波小,可有效保持直流侧输出电压平衡。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.