梯级水电站施工导流风险效益补偿机制研究

汛期通过上游已建水电站调蓄可保障下游施工电站的度汛安全。为有效均衡上下游风险,合理分摊合作利益,对梯级水电站施工导流风险效益进行了补偿机制的设计。以总效益可量化为前提,提出补偿是落实风险效益分摊的一种支付行为,分别从补偿主客体的界定、责权利的划分、风险效益计量、补偿实施方式、补偿管理流程设计等方面,构建了梯级水电开发条件下施工导流风险效益补偿框架和程序。针对补偿制度实施存在的难点,提出了相应的对策和建议,可为流域梯级水电站风险效益补偿管理模式和制度的构建提供参考。     

Tele‐Cocooning: Mobile Texting and Social Scope

The present study examines the tele‐cocooning hypothesis in the context of general trust using a nationally representative survey of Japanese youth. We find that although frequency of texting is positively correlated with general trust, this correlation is spuriously caused by how heavy mobile texters interpret the words “most people” in the general trust measurement. Heavy users assume that “most people” only refers to friends, family, and others going to the same school. When the effect of the “most people” assumption is controlled, the positive association between texting and general trust disappears. Further exploration of the data shows that heavy texting nevertheless has negative implications for social tolerance and social caution, both of which are theoretically proximate to general trust.     

Hysteretic Nonlinearity Observer Design Based on Kalman Filter for Piezo-actuated Flexible Beams with Control Applications

Piezoelectric actuators fundamentally possess hysteresis behavior. Estimation of the hysteresis is usually demanded for enhancing the performance of piezo-actuated systems. This paper presents an observer-based scheme to estimate the hysteresis in piezo—actuated flexible beams. The observer is based on a nonlinearity observer method. The discrete-time Kalman-filter algorithm is adopted for determination of the observer gains. The major advantages of the presented scheme include ease of implementation and robustness to uncertainty of hysteresis parameters. Simulation results demonstrate that the observer is able to estimate the hysteresis efficiently and has better robustness compared to the previous scheme existing in the literature. The present scheme was also successfully applied to a real-life system. Moreover, a control application example is included to demonstrate the effectiveness of the scheme.     

受端电网区域无功自动控制调控策略研究

要确保受端电压的稳定性,就要保证有足够的无功补偿。静态无功补偿可以有效降低网损,并提供稳定的无功功率。但在电网系统变得越来越复杂的情况下,静态无功补偿已经很难满足需求,这时,动态无功补偿作为一种更为有效的无功补偿方式应运而生了。     

基于单片机的功率因数补偿控制器硬件的研究

为了减小电网中感性负载造成的电量损耗,在分析了现有功率因数补偿控制器的补偿效果后,设计了一种通过单片机控制四组电容器组,自动控制投切进行补偿的功率因数补偿控制器。     

Frequency analysis and compensation of valve stiction in cascade control loops

Valve stiction is often a common problem in control loops and stiction induced oscillation is the main cause of poor performance in control systems. Cascade control is extensively applied in process industry as an effective strategy to restrain disturbances and compensate process nonlinearities. In recent years many studies have been performed on the detection and quantification of valve stiction in single feedback control loops. However, there is a lack in developing a mechanism which can analyze stiction induced oscillation in cascade control loops. This work focuses on the frequency analysis of stiction induced oscillations in cascade control loops and proposes a mechanism of oscillation compensation through outer and inner controller tuning. The effect of oscillation compensation by changing control strategies is also discussed. The theoretical analysis is evaluated through simulation examples and a pilot-scale flow-level cascade control experiment.     

A robust two degree-of-freedom controller for systems with both model and measurement uncertainty

This paper presents a design method for robust two degree-of-freedom (DOF) controllers that optimize the control performance with respect to both model uncertainty and signal measurement uncertainty. In many situations, non-causal feedforward is a welcome control addition when closed loop feedback bandwidth limitations exist due to plant dynamics such as: delays, non-minimum phase zeros, poorly placed zeros and poles (Xie, Alleyne, Greer, and Deneault (2013); Xie (2013), etc. However, feedforward control is sensitive to both model uncertainty and signal measurement uncertainty. The latter is particularly true when the feedforward is responding to pre-measured disturbance signals. The combined sensitivity will deteriorate the feedforward controller performance if care is not taken in design. In this paper a two DOF design is introduced which optimizes the performance based on a given estimate of uncertainties. The controller design uses H_∞ tools to balance the controlled system bandwidth with increased sensitivity to signal measurement uncertainties. A successful case study on an experimental header height control system for a combine harvester is shown as an example of the approach.     

An analysis,design and tuning of Cascade Control Systems in the presence of constraints in actuator and process outputs

In the presence of rate constraints in actuator, design of cascade controller based on the primary controller conditional integration can result into closed-loop system oscillations. Stability analysis, performed by the describing function technique and confirmed by simulation, demonstrates that the solution based on the Anti-Reset Windup Cascade Control System (ARW CCS) structure is successful. Design and tuning of the ARW CCS secondary controller is a standard ARW single-input single-output problem. In the present paper tuning is proposed for the ARW CCS primary controller. For the serial process modeling simple rules are derived and confirmed by experimental results, obtained on a drum type boiler of a 210 MWe lignite coal fired unit. General design of the ARW CCS is based on the parallel process modeling and optimization of the primary controller. Optimization is performed in the frequency domain, under constraints on the maximum sensitivity, multiplicative uncertainty bound and sensitivity to measurement noise. Simulation and experimental results on a laboratory thermal plant demonstrate effectiveness of the proposed optimization.     

改进控制律的变结构STATCOM无功补偿控制

静止同步补偿器(STATCOM)是柔性交流输电系统(FACTS)的重要组成部件,本文建立了静止同步补偿器在三相静止坐标系下的数学模型,通过PARK变换将ABC坐标转化为d-q坐标。鉴于STATCOM在d-q坐标下的强耦合性,采用状态反馈精确线性化方法将该模型线性化解耦,构造出一个伪线性模型。然后,采用一种改进的指数趋近律变结构控进行了STATCOM无功补偿控制器的设计。最后,使用Matlab/Simulink对所设计的控制器进行了计算机仿真,并与传统的PI控制器比较,说明了变结构控制的STATCOM无功补偿控制器设计的可行性和有效性,同时也证明了改进的指数趋近律变结构控制的优越性。     

ZPW-2000A轨道电路断轨态分析

轨道电路断轨态接受端电压阈值的界定是影响断轨检测系统可行性及可靠性的关键因素。针对ZPW-2000A轨道电路的断轨态进行仿真分析,在轨道电路断轨态数学模型的建立中考虑了电气绝缘节的等效阻抗以及补偿电容等单元对轨道电路传输特性的影响,利用分布参数模型法推导得出其传输矩阵参数。并在不同的道床电阻和断轨点条件下,利用Matlab软件仿真分析了ZPW-2000A轨道电路断轨态接受端轨面电压的变化。结果表明道床电阻和断轨点位置是影响轨道电路接受端轨面电压的两个重要因素,随着道床电阻和断轨点的变化,断轨态接受端电压始终存在着一个极大值。该仿真模型的建立及其分析方法为ZPW-2000A轨道电路断轨检测的阈值确定提供了一定的依据。