Deadbands and the Dynamic Response and Performance of Large Water Transfer Canal System

An operating simulation mode for multireach canal system in series under gate regulating is established. The discharge feedforward plus water lever feedback PID controller was adopted. And the performance indicators are introduced to evaluate the control effects of canal operation. Influence on dynamic response process and dynamic performance as well as the control actions of canal system are studied according to the variation of the gate deadband and water level deadband. The results showed that the larger the gate deadband, the worse, the control effect of canal system over water level, and so done the stable process of gate discharge, yet the stable process of gate opening was getting better, while the upstream gate regulation of each canal pool was less at the time when canal stabilizes; the closer to downstream end of canal, the lager steady-state error of this canal pool was, and the lager influence of gate deadband on the steady-state error as well as response time of this canal pool was; the canal system can not acquire superiority in both the control performance and control actions when only the water level deadband was established.

Stability analysis and stabilization of wireless networked control systems based on deadband control scheduling

The stability analysis and stabilization problems of the wireless networked control systems(WNCSs) with signal transmission deadbands were considered. The deadbands were respectively set up at the sensor to the controller and the controller to the actor sides in the WNCS, which were used to reduce data transmission, furthermore, to decrease the network collision and node energy consumption. Under the consideration of time-varying delays and signal transmission deadbands, the model for the WNCS was presented. A novel Lyapunov functional which took full advantages of the network factors was exploited. Meanwhile, new stability analysis and stabilization conditions for the WNCS were proposed, which described the relationship of the delay bounds, the transmission deadband bounds and the system stability. Two examples were used to demonstrate the effectiveness of the proposed methods. The results show that the proposed approach can guarantee asymptotical stability of the system and reduce the data transmission effectively.

Signal difference-based deadband H_∞ control approach for networked control systems with limited resources

This paper investigates a signal difference-based dead- band H∞ control approach for networked control systems （NCSs） with limited resources. The effects of variable network-induced de- lays, sampling intervals and data transmitting deadbands are con- sidered simultaneously and the model of the NCS is presented. A Lyapunov functional is adopted, which makes full use of the network characteristic information including the bounds of net- work delay （BND）, the bounds of sampling interval （BSI） and the bounds of transmission deadband （BTD）. In the meanwhile, the new H∞ performance analysis and controller design conditions for the NCSs are proposed, which describe the relationship of BND, BSI, BTD and the system＇s performance. Three examples are used to illustrate the advantages of the proposed methods. The results have shown that the proposed method not only effectively reduces the data traffic, but also guarantees the system asymptotically sta- ble and achieves the prescribed H∞ disturbance attenuation level.

Frequency Control of Power System with Solar and Wind Power Stations by Using Frequency Band Control and Deadband Control of HVDC Interconnection Line

In recent years, environmental problems are becoming serious and renewable energy has attracted attention as their solutions. However, the electricity generation using the renewable energy has a demerit that the output becomes unstable because of intermittent characteristics, such as variations of wind speed or solar radiation intensity. Frequency fluctuations due to the installation of large scale wind farm (WF) and photovoltaics (PV) into the power system is a major concern. In order to solve the problem, this paper proposes two control methods using High Voltage Direct Current (HVDC) interconnection line to suppress the frequency fluctuations due to large scale of WF and PV. Comparative analysis between these two control methods is presented in this paper. One proposed method is a frequency control using a notch filter, and the other is using a deadband. Validity of the proposed methods is verified through simulation analyses, which is performed on a multi-machine power system model.

一起死区故障导致35 kV母差保护动作案例分析

介绍了在AVC切除电抗器过程中,发生的一起35 kV母差保护动作事件,导致35 kVⅡ段母线上所有开关全部跳闸。根据现场采集情况,分析了开关跳闸原因,同时对预控措施做了阐述。

新型高压输电线路低下限死区大功率在线取能装置

为解决覆冰在线监测系统供能问题,研制了一种低下限死区、大功率输出的取能线圈。采用初始磁导率较高的纳米晶材料铁芯,且铁芯的二次绕组有多个抽头输出,利用逻辑控制固态继电器在不同变比间切换,实现在不同的电流范围选取不同的匝数。试验发现,在母线电流为2 A时,取能线圈输出功率可>0.5 W;母线电流达到100 A时,取能线圈饱和程度低;母线电流达到1 000 A时,铁芯被保护不达到磁饱和状态。试验结果表明,特制的取能线圈能够在较低的电流下限取得较大的输出功率,在母线大电流时不致深度饱和损坏铁芯。

光纤陀螺的死区研究

试验验证了光纤陀螺的死区,分析了电路的交叉耦合是产生死区的主要原因。同时,调制器当2π复位电压不准确或者解调信号存在尖峰脉冲时,阶梯波与方波的数字叠加,也容易出现较大死区。提出了抑制死区的具体措施。

单机等值系统调速器死区对频率振荡的影响

实际系统中多次发生一次调频过程不稳定导致的超低频频率振荡事件。调速器死区给系统带来非线性,进而影响系统的频率振荡行为。基于单机等值系统,采用描述函数法分析了无阶跃死区、有阶跃死区和滞环死区这3种死区对频率振荡的影响。在复平面上,给出了死区描述函数的负倒数随振幅变化的轨迹,以及调速器、原动机、发电机构成的开环传递函数随频率变化的曲线,两者相对位置关系决定系统的稳定性。负倒数随振幅变化特性曲线完全位于开环频率特性曲线左侧时,系统稳定。其他情况下2条曲线一般会相交,交点对应极限环,极限环稳定与否决定于交点的具体形态。同时分析了单机等值系统中调速器死区对频率振荡的影响,调速器无阶跃死区和有阶跃死区都不会减弱系统稳定性,但有滞环死区时可能导致原本稳定的系统出现稳定极限环引发的持续等幅振荡。时域仿真结果验证了上述结论。

消除光纤陀螺死区的方法研究

光纤陀螺的工作原理和检测方法使得它从理论上将不存在死区,光纤陀螺的死区是因为电路的交叉耦合以及输出方式造成的。文中阐述了光纤陀螺死区的测量方法,分析和推导了死区产生的机理,提出了通过引入正弦信号减小或消除死区的具体措施,并进行了试验验证。结果表明,该措施可以大大减小或消除光纤陀螺死区,同时对陀螺的静态精度不产生影响。

滑阀中位线性补偿技术研究

滑阀的内泄漏会使阀控缸系统中的油缸活塞产生自行动作,为减小滑阀内泄漏量,在影响滑阀内泄漏的诸多因素中,选择了易于实现且成本较低的方案——增大滑阀阀芯和阀套的搭接量,同时为了弥补死区以及滑阀工作锐边变钝对滑阀性能的影响,基于数字伺服阀,采用分段变增益的流量增益补偿方案对滑阀中位的线性补偿技术进行了研究。经试验表明,降低滑阀内泄漏及滑阀中位线性补偿方案有效的保证了滑阀的低泄漏及空载流量增益的线性特性。

气动比例阀的死区补偿与仿真

针对气动比例阀的死区产生机理及对系统控制性能造成的不良影响,提出了1种新的对比例阀的死区进行补偿方法.首先分析了比例阀的摩擦力是造成其死区的主要原因,并利用神经网络控制对比例阀摩擦力进行软件补偿,消除了比例阀死区对系统稳定性的影响.并通过系统仿真研究,证明该控制方法用于气动比例阀死区补偿的正确性和有效性.该补偿方法具有较高的工程应用价值.

网络控制系统动态死区反馈调度

为了在负载变化的网络环境中合理调度资源,提出了将死区控制与节点优先级分配相结合的调度器。死区控制可以在不严重影响控制质量,以及不改变系统采样率的情况下节省网络资源。结合优先级的合理分配,所设计的网络控制系统可以在网络负载较轻的时候充分利用带宽资源,在网络重负载的时候实现控制质量的逐渐降低。实验仿真结果表明:所设计的在线动态调度方法可以在变化的工作环境中改善网络控制系统的性能,提高应对工作负载变化的能力。

Fault-Tolerant Control Research for Networked Control System under Communication Constraints

Implementing a control system over a communication network induces inevitable time delays that may degrade performance and even cause instability. One of the most effective ways to reduce the negative effect of delays on the performance of networked control system (NCS) is to reduce network traffic. In this paper, adjustable deadbands are explored as a solution to reduce network traffic in NCS. A method of fault-tolerant control of networked control system is presented, which takes into account system response as well as network traffic. The integrity design for a kind of NCS with sensor failures and actuator failures is analyzed based on robust fault-tolerant control theory and information scheduling. After detailed theoretical analysis, the paper also provides the simulation results, which further validate the proposed scheme.

过程参数滋扰报警的一类自适应管理策略

滋扰报警是过程工业报警系统的主要问题,然而,目前报警优化方法一般敏感度低、可靠性差,根据报警变量之间的时间间隔和报警持续时间确定滋扰报警的形式,提出了自适应报警死区和报警延时器的计算方法,利用时间序列ARMA模型预测报警死区来处理高频报警,并利用报警间隔时间更新报警延时器参数n来处理低频报警。通过工业实例数据验证表明,所提出的方法能够有效减少滋扰报警的数量、提高报警系统的性能。

利用曲线拟合对触觉数据的压缩

为减轻离线触觉数据压缩带来的失真变形,提出利用曲线拟合的压缩方法.在假定触觉数据所对应原触觉信号能用分段二次参数曲线表示的前提下,通过反向采样过程来构造触觉数据拟合曲线,该曲线由分段二次曲线组成,在连接处达到切线连续,且每段二次曲线对原触觉信号具有二次多项式逼近精度.为避免保存拟合曲线的所有系数以进一步提高数据减少率,对拟合曲线系数进行了迭代求解,从而只需编码保存部分系数即可解码.实验结果表明,该方法在保持高数据减少率的前提下减轻了压缩失真变形.

参数未知自相关过程的自适应边界调整策略

针对参数未知的自相关过程的质量控制问题,研究了每次调整成本固定下的自适应调整策略。建立了过程的状态空间方程模型以及未知参数的贝叶斯模糊先验分布,利用序贯蒙特卡洛法估计未知参数值进而得到了过程每个阶段的调整边界线,从而确定使过程总体损失最小的边界调整策略;给出了基于序贯蒙特卡洛法的边界调整策略的算法步骤,并通过算例验证了调整策略的有效性。结果表明,该调整策略具有较好的调整效果。

SPWM静态调制误差分析

脉宽调制(PWM)技术是电力电子领域的核心技术,为了分析各种相关因素对PWM输出结果的影响,文中提出了PWM的静态调制误差(PWMSME)的概念。以SPWM为例,在Fourier变换的基础上推导出了其PWMSME随频率变化的精确数学表达式,分析了载波频率、死区及采样方式对PWMSME的影响,并给出了其量化的表达式。指出了在载波频率较低的情况下,由“冲量等面积原理”计算的输出结果会产生一定的误差。最后,通过对PSCAD建立的H桥逆变器模型的仿真结果、实验数据及相应公式的数值计算结果对比分析,验证了文中结论的正确性。

电荷泵锁相环中相位噪声的抑制和讨论

旨在介绍一种抑制电荷泵锁相环 ( CPPL L)中相位噪声 ( Jitter)的电路结构。文章在分析 CPPL L 对 Jitter抑制原理的基础上 ,指出 Jitter虽然无法被环路自身的跟踪作用根除 ,但却可以通过对鉴频鉴相器 ( PF D)的改进而得到较好地抑制。为了验证改进电路的效果 ,文中给出了实验数据 ,实验结果证明新的电路结构可以较好地抑制 Jitter。

长距离明渠调水工程蓄量动态调节控制算法研究

本文阐明了明渠渠池蓄量与节制闸闸前水位之间的单值对应关系,在此基础上提出一套通过动态调节渠池蓄量,实现闸前常水位运行的控制算法。该算法基于流量平衡和蓄量平衡关系推导,前馈控制与反馈控制相结合。前馈控制根据分水口计划主动调节各渠池蓄量,起粗调作用;反馈控制针对前馈控制过程出现的水位偏差,通过动态调节各渠池蓄量实时校正,起细调作用。该算法具有原理简单,参数率定简便,控制规则灵活,实用性强等特点。算法在南水北调东线工程胶东段渠道进行了仿真测试,模拟环境包含水位死区和闸门运动死区。结果表明,所提算法能够有效克服长距离明渠水力滞后的影响,及时有效消除各渠池闸前水位偏差,将水位波动限定在安全范围内。

数字闭环光纤陀螺的死区分析和抑制方案研究

死区现象是闭环光纤陀螺特有的现象,它使陀螺输出具有明显的非线性,严重影响闭环光纤陀螺的测量精度;文章采用了中值滤波的方法消除输入信号中的误差信息,同时,又通过控制D/A转换器的参考电压的方式,对阶梯波2π复位电压进行修正,到达消除死区现象的效果;从实验结果对比可以看出,该方法有效抑制了陀螺死区现象的发生。