Sensorless tension control in paper machines

Proper operation of the dry end of a paper machine requires some type of sheet tension control. Present systems use either indirect-speed-control-based schemes, or sensor-based direct tension control utilizing load cells or swing rolls. The indirect schemes are inadequate for most newer machines, and both types of the commonly used sensor-based schemes are invasive, expensive, require either special, or extra rolls, and add complexity to the sheet runs. This paper proposes and evaluates sheet tension estimation using only conventional motor and control signals, present in all newer drive controllers, integrated into a process model observer. This observer-based approach eliminates the need for the invasive tension transducers, and may also be used to replace the inaccurate indirect speed control schemes.     

基于双目立体视觉的连铸辊尺寸三维测量方法

针对连铸车间中,扇形段连铸辊尺寸人工测量效率低下的问题,提出了一种基于双目视觉系统的连铸辊尺寸测量方法。首先,对双目相机采集的图像进行预处理并采用Otsu法分割工件前后背景;接着,针对边缘检测精度不高的问题,将传统Canny边缘检测算法的梯度模板增加到8个以提取工件轮廓,结合多项式插值公式提取亚像素级别特征点;然后,在SAD与Census变换融合的立体匹配基础上引入RANSAC算法来消除错误匹配;最后,采用三角测量原理计算出零件的尺寸。实验结果表明,系统测量的平均相对误差为0.14%,测量方法具有较高的精度,其稳定性与精确性满足连铸辊的尺寸自动检测任务。     

A new tension controller for continuous strip processing line

The strip tension as well as the line speed should be controlled tightly for the quality of products and productivity of the continuous strip processing line. In this paper, a new tension control algorithm with tension observer is proposed using observed tension as a regulator feedback. The tension observer as based on the torque balance of a roller stand, including the acceleration torque. Using this estimated tension, a new tension controller can be constructed with faster dynamic response in case of line speed acceleration or deceleration. The proposed scheme needs no additional hardware because the inputs of observer, current and speed, are already being monitored by the motor drive system. As this scheme directly controls torque current of the motor, better control performance can be obtained even without the tension transducer. Through the simulations and experiments with the laboratory setup, the performance of conventional schemes and the proposed one are compared. The results show the effectiveness of the proposed tension controller     

An integrated load forecasting-load management simulator: itsdesign and performance

An integrated load-forecasting-load-management (LFLM) simulator is constructed that can be used by electric cooperatives and electric utilities alike. Rule-based algorithms have been used for implementing various functions of the simulator. The major elements of the simulator are 24 hour load forecasts, water heater and air conditioner load models, direct load control dispatch, and intelligent databases. The system has been provided with adequate amount of intelligence so that it is able to make the right decisions, revise and update its rules and factors, diagnose problems and take corrective actions without the need for operator intervention in most situations. The load-management simulator consists of a central unit, remote unit, and data sources. Five microcomputers, six monitors, two dot-matrix printers, four modems and a terminal are the main components of the system. The central unit consists of an IBM-RT/PC microcomputer and its communication accessories. The design, implementation, and performance evaluation of the simulator are addressed     

考虑可控负荷的多区域电力系统分布式模型预测负荷频率控制

由于同步发电机的惯性较大,导致传统的集中式负荷频率控制模式反应不够迅速,而用户侧具有快速响应能力的可控负荷资源为系统的频率调节提供了新机遇。研究了考虑用户侧可控负荷资源主动参与系统频率调节的多区域互联电力系统分布式模型预测负荷频率控制问题。通过建立的含可控负荷的多区域互联电力系统负荷频率响应模型及自动发电控制模型,基于连续时域交替方向乘子法和分布式模型预测控制方法,提出了一种用户侧可控负荷资源主动参与的多区域互联电力系统分布式模型预测最优负荷频率控制模型。基于修改的IEEE39节点三区域互联电力系统进行仿真验证,结果表明所提考虑可控负荷的分布式模型预测控制策略可显著减少系统恢复至稳态所需的时间。分布式控制策略的控制自由度更高,增强了系统的可控性。     

黑启动过程中的负荷恢复

研究了黑启动中的负荷恢复与系统并网问题,将基于直角坐标的最优乘子牛顿潮流法与灵敏度技术相结合,采用连续线性规划法对负荷恢复阶段出现的N-1潮流不可行和状态越限问题建立了恢复控制的模型和算法。然后建立了负荷恢复阶段仿真各子系统频率变化过程的模型和算法,针对子系统的并网问题建立了基于连续线性规划的并网压差发电调度算法,有效地解决了并网电压差优化控制问题。用标准测试系统和实际电网的数值仿真试验证明了模型和算法的有效性。     

基于PWM技术的功率负荷模拟器

功率负荷模拟器是电力系统动态模拟实验室不可缺少的设备之一。本文运用PWM电压型变流器的基本原理,设计了一种分离控制式交-直-交功率负荷模拟器。交-直控制部分仅负责对功率负荷伏安特性的模拟,负责把功率负荷模拟器内部的直流电压稳定地交给直-交控制部分去完成。同时,为提高功率负荷模拟器的回馈效率,对回馈电流实行单位功率因数控制。试验结果表明,该功率负荷模拟器既能准确模拟功率负荷的伏安特性,又能向外部电网回馈高质量的电能。     

无传感器的带钢分切机张力控制系统

为解决传统带钢分切机分切精度低、存在卷边的缺点,提出一种无传感器的张力控制系统,实现了分切工艺参数的柔性化调整。剪切辊的喂料和出料均采用伺服电机构成主-从牵引模式,通过控制主-从牵引电机之间的速差,可以间接控制分切张力,实现了无传感器的高精度恒张力控制。卷取轴电机采用交流电机变频驱动的线速度闭环控制系统,通过位置传感器和卷径模型实现卷取过程的张力控制。系统适用于剪切厚度0.15～0.35mm、宽度45mm的不锈钢带,将其分切为2～4mm的窄带,最大分切速度60m/min。实际运行证明：新系统具有控制精度高,分切质量好,稳定可靠的优点。     

Dynamic Load Flow Technique for Power System Simulators

This paper presents a dynamic load flow technique for power system simulators. The approach presented can be applied to a system when there is a net accelerating or decelerating power in the system. It possesses all the attractive features and basic structure of the normal fast decoupled method, and it does not depend on the selected reference bus. The modifications to the standard fast decoupled power flow algorithm are derived, and power system simulator implementation considerations are discussed. The algorithm has been tested on standard IEEE test cases and on a metropolitan utility 559 bus model. A numerical example of the above algorithm on the 559 test case is presented which demonstrates convergence characteristics and computation requirements of the proposed algorithm. These results are compared with those of normal fast decoupled load flow.     

Design and modeling of SMES based SAPF for pulsed power load demands

In this article, a Superconducting Magnetic Energy Storage (SMES) based Shunt Active Power Filter (SAPF) topology is proposed to compensate high power pulsating load demands in a power system. The SMES based SAPF is designed and modeled to realize as an efficient compensator for the compensation of pulsed power load demands. The conventional SAPF is efficient to mitigate the power quality problems in a power system unless there is high power pulsating load demands, transient conditions or power fluctuations. Particularly, a Modified Synchronous Reference Frame (MSRF) control algorithm has been implemented to generate proper switching signals for the three-phase Voltage Source Converter (VSC) of the SMES based SAPF. In the simulation, it has been seen that the SAPF is incompetent under high power pulsating load demands whereas the SMES based SAPF has shown excellent performance under such load conditions. Moreover, a comparative analysis has been made between the conventional SAPF and the SMES based SAPF under pulsating load conditions, to check the effectiveness of the SMES based SAPF. The performance of the proposed system is presented by using Sim Power System (SPS)/MATLAB Simulink and real-time digital simulator laboratory (RTDS-Lab).     

基于虚拟DCS的火电仿真机的设计与开发

针对电站仿真培训系统现状,开发出基于虚拟DCS的多功能火电站仿真机,介绍虚拟DCS及其实现方法,并给出仿真机的软、硬件配置。该仿真机可实现电厂DCS控制逻辑和控制策略的全仿真。     

A Framework for Economic Load Frequency Control Design Using Modified Multi-objective Genetic Algorithm

This article deals with the coordination of security-constrained economic dispatch and load frequency control in an interconnected power system. The realistic and performance optimization inherent of the load frequency control (LFC) and security-constrained economic dispatch are fully considered without simplifying assumptions. For this purpose, modeling security-constrained economic dispatch as a discontinuous control action in the continuous frequency response model of a power system is well addressed. Considering conflict behavior of LFC and security-constrained economic dispatch beside the powerfulness of the multi-objective genetic algorithm (GA) to solve high-dimensional problems with conflicted objective functions makes it attractive for the automatic generation control coordination problem. The employed security-constrained economic dispatch utilizes the advantages of dynamic economic dispatch to achieve more realistic results. The GA is used to compute the decentralized control parameters and centralized generation levels of the on-line units to achieve an acceptable operating point. A significant modification in convergence speed has been performed by using LFC model properties in corporation with the genetic algorithm, so the proposed method gives considerable promise for implementation in multi-area power systems. The efficiency of the proposed algorithm and modification is demonstrated on a three control area power system.     

基于迭代学习控制的电动伺服负载模拟器

电气伺服系统在体积、结构、成本和控制性能等方面比电液伺服系统更为优越，由电气伺服系统构成负载模拟器取代电液负载模拟器为被测对象提供模拟负载，将大大提高仿真加载的性能。该文探索了电动伺服负载模拟器的实现问题。针对飞行器舵系统的仿真加载需求，提出了由永磁电机伺服系统组成的电动伺服负载模拟器的系统结构；将PID反馈控制和迭代学习控制相结合构成加载复合控制器，有效地抑制了多余力矩，消除了传动间隙和加载对象参数变化对系统的影响，实现了加载转矩的高精度跟踪控制。     

考虑温控负荷需求响应的电热联合系统多阶段鲁棒调度方法

在发展新型电力系统的背景下,间歇性新能源占比不断增加,对电热联合系统的灵活性提出更高要求。提出了一种考虑温控负荷需求响应的电热联合系统多阶段鲁棒调度方法。首先建立考虑电热转换设备、温控负荷等多种灵活性资源的电热联合系统模型,并提出虚拟储能的概念对温控负荷进行建模。然后,将风电出力预测误差建模为盒式不确定集,以燃料成本、弃风惩罚、需求侧补偿综合成本最低为目标函数,提出了电热联合系统的多阶段鲁棒调度模型,在每一调度时段,均可根据风电的观测值,以最小化当前及后续时刻的总成本最大值为目标,调整后续调度计划,并通过鲁棒对偶动态规划算法求解该模型。最后,通过算例验证了所提方法的有效性。     

液压负载模拟器的分析与设计

对液压负载模拟器进行了深入分析和研究。针对机液负载模拟器、电液负载模拟器和加载液压马达壳体同步反馈型电液负载模拟器3种结构型式,分析了各自的优缺点。最后,以电液负载模拟器为例,提出了按加载梯度选择最佳动力参数的方法和一种能有效减少多余力的复合控制方法     

Model-free hierarchical control with fractional-order sliding surface for multisection web machines

Due to the nonlinearities and dynamical properties of multisection web machines, it is essential to accomplish an appropriate mathematical model as well as design a compatible control scheme. A generalized fully driven web winding model is constructed taking unpredictable changes of moment of inertia and radius of rolls into consideration. In this article, a fractional-order sliding surface algorithm-based hierarchical control frame is applied to multisection web machines to deal with matched and mismatched uncertainties and disturbances. In addition, the Radius Basis Function neural network is deployed to estimate necessary system dynamics and the proposed control scheme taking advantage of first-order low-pass filters to produce virtual control signals without complicated calculation and attenuate the explosion of terms phenomenon. Finally, the semi-global stability of the entire system is determined using Lyapunov's stability theory. The simulation results are presented to clarify the superior performance of robust control algorithm and approximation law in the presence of nonideal elements.     

Firefly Optimization Algorithm for the Reactive Power Control of an Isolated Wind-Diesel System

This paper investigates the application of firefly optimization algorithm to design an optimal control for voltage stability of a stand-alone hybrid renewable generation unit based on reactive power control. The studied renewable generation unit mainly consists of a permanent magnet induction generator driven by wind turbine and a synchronous generator driven by diesel engine. A STATCOM is used to stabilize the terminal load bus voltage via compensating of reactive power. The main control objective aims to stabilize the terminal load voltage against any disturbances in load reactive power and/or input wind power by adjusting the total system reactive power. This is accomplished by controlling STATCOM phase angle and hence to control the load bus voltage and also by controlling the excitation voltage of the synchronous generator. The proposed renewable energy power system based on the proposed optimal controller has been tested through step change in input wind power and load reactive power. The system performance based on the proposed control is compared with model predictive control, a robust H_∞ control, and a classical PI control.     

Development of a hybrid margin angle controller for HVDC continuousoperation

The objective of this paper is to present a new hybrid margin angle control method for HVDC continuous operation under AC system fault conditions. For stable continuous operation of HVDC systems, the margin angle controller must be designed to maintain the necessary margin angle to avoid commutation failures. The proposed method uses the open loop margin angle controller (MAC) as the basic controller, and adds output from the closed loop MAC to correct the control angle. A fast voltage detection algorithm is used for open loop control, and margin angle reference correction using harmonics detection for closed loop control are also developed. The combination of open and closed loop control provides quick responses when faults occur with stable and speedy recovery after fault clearance. The effectiveness of the developed controller is confirmed through EMTP digital simulations and also with the experiments using an analogue simulator     

Microprocessor Application in Substation Control

An operating model of a microprocessor-based system for use in electrical substations is described. The control system performs substation control functions important in continuous process industries? automatic transfer and sequential reacceleration of motors following short duration voltage outputs. The system provides an interface for load shedding and motor control, and has several useful data-gathering features. The model has been rigorously tested using a simulator which mimics substation input/output signals in real time. Performance capabilities and security/reliability aspects of both hardware and software are discussed with reference to conventional hardwired schemes.