大型冷轧管机组的电气控制系统研制

LG720冷轧管机组是世界最大规格冷轧管机组。为该机组研制的电气系统采用了PLC、变频调速、PROFIBUS-DP网络通讯、SIMOTION D、HMI等技术,实现了多机变频调速传动,对大惯量负载的送进和回转机构实现高动态响应、高精度定位和同步控制,满足了大型冷轧管机组的生产要求。     

Convergence analysis of self-tuning Riccati equation for systems with correlation noises

For linear discrete time-invariant stochastic system with correlated noises, and with unknown state transition matrix and unknown noise statistics, substituting the online consistent estimators of the state transition matrix and noise statistics into steady-state optimal Riccati equation, a new self-tuning Riccati equation is presented. A dynamic variance error system analysis (DVESA) method is presented, which transforms the convergence problem of self-tuning Riccati equation into the stability problem of a time-varying Lyapunov equation. Two decision criterions of the stability for the Lyapunov equation are presented. Using the DVESA method and Kalman filtering stability theory, it proves that with probability 1, the solution of self-tuning Riccati equation converges to the solution of the steady-state optimal Riccati equation or time-varying optimal Riccati equation. The proposed method can be applied to design a new selftuning information fusion Kalman filter and will provide the theoretical basis for solving the convergence problem of self-tuning filters. A numerical simulation example shows the effectiveness of the proposed method.     

Some practical aspects of a nonrecursive solution to the discrete Riccati equation

The design of computer-based optimal controllers for synchronous machines has been the subject of a number of recent research papers. The design of such controllers generally involves the solution of the steady-state discrete Riccati equation. A method of checking the solution accuracy of a nonrecursive technique based on the eigen-value properties of the canonical state equation, and an example to illustrate the technique, are presented.     

Analysis of dynamic behaviors of tandem cold mills usinggeneralized dynamic and control equations

A generalized equation set is proposed to investigate dynamic behaviors of tandem cold mills. The system is composed of the intrastands and the interstands equations and the boundary conditions of the first and the last mill stands. The solution provides detailed dynamic effects of disturbance variables such as anneal and entry gauges, hardness, and roll eccentricity. The transportation delay is considered as well. The mill dynamic equations and the control equations can be combined to form a linear system. The mill performance and the actuator response can be solved directly from the linear system     

KR铁水预处理过程控制系统设计与应用

介绍了KR铁水预处理过程控制系统的构成及主要控制方式。综合应用铁水脱硫理论和控制理论,提出电、仪一体化的解决方案。以生产过程中关键设备控制为例,阐述了控制系统在生产过程中的实际应用和效果。     

Hamilton‐based adaptive robust control for the speed and tension system of reversible cold strip rolling mill

The adaptive robust control problem for the speed and tension system of reversible cold strip rolling mill is studied based on the Hamilton theory in this paper. First, the dissipative Hamilton model of the rolling mill system's speed and tension outside loop is built through pre‐feedback control, and then, dissipative Hamilton controllers are designed by utilizing the interconnection and damping assignment and the energy shaping method. Second, in order to realize tensiometer‐free control and adaptive robust control for the perturbation parameters and load disturbance, full‐order state observers and adaptive robust controllers are designed for the rolling mill system's speed and tension outside loop by using the “extended system + feedback” method. Third, robust controllers for the rolling mill system's current inside loop are designed based on the cascade control thought, so as to realize the tracking control for the speed and tension of reversible cold strip rolling mill. Theoretical analyses show that the resulting closed‐loop system is stable. Finally, simulation research is carried out on the speed and tension system of a 1422‐mm reversible cold strip rolling mill, and simulation results verify the validity of the proposed control strategy in comparison with the decentralized overlapping control strategy.     

An approximate reasoning approach for optimal dynamic dispatch ofthermal generating units including auxiliary control

Fuzzy set theory is applied to decision-making in the optimal generation dispatch of thermal generating units. Operational requirements such as unit auxiliary start-up and shutdown create discrete zones of generation output. Plant operators are required to switch units dynamically from one output zone to another in order to keep track of the changing load. The problem arises when making the decision to switch zones for dynamic load dispatch, because of complicated operational conditions. The authors apply approximate reasoning in order to coordinate multiple system requirements and to make effective zone-switching decisions. Membership functions are introduced to measure generation-load balance, fuel cost, and time to stay in a zone. Approximate reasoning using these indices yields information concerning compatibility of output zones. Model analysis is used to demonstrate the flexibility and improved man-machine interface of the approach     

Exact analytical solution for nonuniform multiconductor transmission lines with the aid of the solution of a corresponding matrix Riccati equation

Contents Nonuniform multiconductor transmission lines (NMTLs) are formulated from the telegrapher equations into a first-order supervector/supermatrix differential equation combining the voltage and current vectors. This equation is converted to one for the waves propagating in the two directions of the transmission line. Both equations can be represented in a common general supermatrix form. The supermatrizant describing the solutions of this general equation is evaluated via transformation with an elementary relative matrix and the solution of a matrix Riccati equation simplifying the resulting telegrapher equations to a structure to which the usual sum rules for product integrals can be applied easily. The block elements of the supermatrizant are (mainly) composed by matrizants ofN×N matrices. For a single nonuniform line and for circulant NMTLs the supermatrizants are represented by exponentials.

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Exakte analytische Lösung für ungleichförmige Vielfachleiter mit Hilfe der Lösung einer korrespondirenden Matrix-Riccati-Gleichung

Übersicht Die Telegraphengleichungen für ungleichförmige Vielfachleiter lassen sich als Differentialgleichungen erster Ordnung in Supervektor-/Supermatrixform schreiben. Dazu müssen die Spannungs- und Stromvektoren zu einem neuen Vektor zusammengefaßt werden. Der Übergang auf Wellenvektoren führt auf eine Differentialgleichung derselben Form. Die Lösungen dieser zusammengefaßten Telegraphengleichungen lassen sich durch den Supermatrizanten ausdrücken. Eine Transformation mit einer elementaren Relativmatrix und das anschließende Lösen einer Matrix-Riccati-Gleichung vereinfachen die zu lösenden Telegraphengleichungen derart, daß der gesuchte Supermatrizant mit den üblichen Regeln für Produktintegrale gefunden werden kann. Dieser Supermatrizant setzt sich seinerseits im wesentlichen ausN×N-Matrizanten in seinen Matrixblöcken zusammen. Füreinen nicht-gleichförmigen Leiter und im Falle zyklischer Matrizen für die ungleichförmigen Vielfachleiter können die Supermatrizanten als Exponential-funktionen dargestellt werden.

     

基于最优控制方法的一类不确定非线性系统的鲁棒控制

研究了一类不确定非线性系统的鲁棒控制问题,目的是在未满足不确定性匹配条件的情况下设计稳定系统的状态反馈。通过将设计鲁棒控制器问题转化为设计最优控制器问题以补偿系统中的不确定性,说明了最优控制的解即为鲁棒控制的解,并通过仿真说明这种设计方法的效果。     

Mixed-integer nonlinear approach for the optimal scheduling of a head-dependent hydro chain

This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning a head-dependent hydro chain. We propose a novel mixed-integer nonlinear programming (MINLP) approach, considering hydroelectric power generation as a nonlinear function of water discharge and of the head. As a new contribution to earlier studies, we model the on–off behavior of the hydro plants using integer variables, in order to avoid water discharges at forbidden areas. Thus, an enhanced STHS is provided due to the more realistic modeling presented in this paper. Our approach has been applied successfully to solve a test case based on one of the Portuguese cascaded hydro systems with a negligible computational time requirement.     

Indirect optimal control of a double quantum dot

An indirect optimization method for the dynamic control of non-Markovian open quantum systems is presented. It is demonstrated at the example of a spin-boson model for an electron in a double dot which couples to a bath of phonons. This study reveals strategies for controlling the effective system-bath coupling which become available when the system is addressed in its quantum regime. We give examples for population transfer, trapping and quantum operations.     

Proportional and integral optimal control of a turbogenerator

This paper describes an investigation into the use of integral and proportional optimal control methods to design multivariable controllers which improve the performance of a turbogenerator. It presents the turbogenerator nonlinear mathematical model from which a linearized model is deduced. The theory of optimal control is applied to the linearized model to generate two alternative control schemes. The schemes are then implemented software-wise on the nonlinear simulation model in order to assess their dynamic performance. Results from these modern multivariable control schemes are compared with those of the classical familiar automatic voltage regulator and speed governor systems.     

Digital control and optimization of a rolling rotor switchedreluctance machine

A motor having a rotor which is free to roll on the inside of the stator, without bearings restraining it to a fixed axis, is proposed. Using the axial rather than the tangential forces between rotor and stator, this motor develops considerable torque at low speeds. A digitally based controller and the power electronic implementation which minimizes vibrational effects, torque pulsations, and also increases overall motor efficiency is described. Attention is drawn to the robustness and simplicity of the motor, making it ideal for low-cost applications, where a large torque at low speeds is required from a compact gearless construction. Valuable design considerations have been gained by the use of a finite element analysis on the rolling rotor switched reluctance motor     

Modeling of a large electric power system for optimal control of dynamic stability

This paper describes a general state-variable form of mathematical modeling which may be used to control the dynamic stability of a larger power system optimally. Based on the linearization about the operating point of the system, a complete model for dynamic stability control is obtained by combining transmission network equations, full-order synchronous machine equations, the exciter and voltage regulator model, torque equations, and the governor-hydraulic model in a matrix form which includes supplementary excitation and governor control signals. The complete model may then be simplified as a low-order model by neglecting the governor effects, exciter time constant, and all but the field flux linkage variations of the machines in order to reduce computational requirements.     

An approach of optimal sensitivity applied in the tertiary loop of the automatic generation control

This paper proposes an approach of optimal sensitivity applied in the tertiary loop of the automatic generation control. The approach is based on the theorem of non-linear perturbation. From an optimal operation point obtained by an optimal power flow a new optimal operation point is directly determined after a perturbation, i.e., without the necessity of an iterative process. This new optimal operation point satisfies the constraints of the problem for small perturbation in the loads. The participation factors and the voltage set point of the automatic voltage regulators (AVR) of the generators are determined by the technique of optimal sensitivity, considering the effects of the active power losses minimization and the network constraints. The participation factors and voltage set point of the generators are supplied directly to a computational program of dynamic simulation of the automatic generation control, named by power sensitivity mode. Test results are presented to show the good performance of this approach.     

New control approach for a PV-diesel autonomous power system

A new control scheme for the hybrid photovoltaic-diesel single-phase autonomous power system is proposed. The main advantage of this scheme is that the voltage control is accomplished by the interface inverter without need to the automatic voltage regulator of the diesel-driven generator. Unlike three-phase systems, frequency and voltage control in single-phase autonomous power systems imposes additional complexity. This is due to the pulsating nature of the single-phase loads instantaneous power at twice the rated frequency that may degrade the control efficacy. This obstacle is addressed in this paper and a new scheme is presented. The approach includes three control loops for maximum power tracking, voltage control and frequency control. The generator field current is held constant at its nominal value avoiding the saturation in the field circuit. A robust fuzzy logic controller is adopted for the speed control loop of the diesel engine. The dynamic performance of the system is investigated under different operating conditions.     

轧机液压伺服位置系统的自适应输出反馈控制

针对具有不可测状态、未知参数和非线性的轧机液压伺服位置系统,提出一种基于高增益观测器和参数估计器的自适应输出反馈控制算法.所构造的高增益观测器不依赖于系统输入和参数估计值,它只用于估计系统状态,所设计的动态反馈控制器包括:用于保证系统稳定性的主反馈部分和抵消外部扰动和一些不确定性的补偿部分.理论分析表明,所提出的控制算法能够保证闭环系统的所有信号有界,且系统状态及其估计误差的最终收敛边界依赖于观测器的高增益值.以某650 mm可逆冷带轧机液压伺服位置系统为例进行仿真,仿真结果验证了所提出算法的有效性.     

Neutral-point voltage control for a three-level DC-AC inverterusing equivalent-input-disturbance approach

One problem with a single source three-level inverter is the drafting of its neutral-point voltage. This may occur during transition or when unbalanced loads are connected to the inverter system. Variation of neutral-point voltage may greatly deteriorate