开关电路中“冒险”现象实例分析

“冒险”现象可影响电路功能甚至破坏整个电路正常运转。当电器元件的动作时间可能影响控制线路动作程序时,必须考虑元件的动作时间及配合方法。以双向染色机控制线路为例,对未考虑“冒险”现象的控制电路进行了故障分析,并给出了相应的改进电路。     

Load Frequency Control via Constant Limited-State Feedback

The design of area controllers for load frequency control is considered. Unlike previous methods where either an optimal state feedback law or a state estimator is used, the technique proposed here uses only the directly measurable system state variables. Therefore the structure of the controllers considered in this paper is much simpler and can be more readily implemented. The performance of the new control scheme is also compared with that obtained via the optimal state feedback law.     

Passivity‐based sliding mode control for nonlinear systems

Passivity with sliding mode control for a class of nonlinear systems with and without unknown parameters is considered in this paper. In fact, a method for deriving a nonlinear system with external disturbances to a passive system is considered. Then a passive sliding mode control is designed corresponding to a given storage function. The passivity property guarantees the system stability while sliding mode control techniques assures the robustness of the proposed controller. When the system includes unknown parameters, an appropriate updated law is obtained so that the new transformed system is passive. The passivation property of linear systems with sliding mode is also analysed. The linear and nonlinear theories are applied to a simple pendulum model and the gravity‐flow/pipeline system, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Reactive current control through SVC for load power factor correction

This paper discusses a new technique for controlling SVCs (Fixed Capacitor–Thyristor Controlled Reactor) in power systems with the aim of canceling the reactive current component of the load. A complete model of the SVC with its control circuit is set up and simulated in the EMTDC program. The generated harmonics from the proposed SVC controller are considered to design simple tuned filters to cancel the undesirable harmonic components. The effect of these filters is considered as well in the SVC control design, so that the reactive current component absorbed by the combination of the load, SVC, and filters is eliminated. The proposed control technique is compared with respect to a standard PI-based SVC controller.     

A functionally complete asynchronous-synchronous digital control system for a valve converter

The implementation of a digital version of an asynchronous-synchronous system for the pulse-phase control of a valve converter is considered. Calculation expressions that define setup values of the main and boundary control angles are presented.     

On the construction of power quality control systems

Some aspects of the construction of power quality control systems in power supply systems are discussed. The basic requirements for quality factors of electric power are determined, the conditions of joint parallel operation of energy consumers are considered, and analysis of traditional ways of solving the emerging problems is carried out. The advantages and disadvantages of power quality control systems related to the capabilities of new technologies with application of high-power semiconductor switching devices (GTO and IGCT thyristors, MOSFET and IGBT transistors) are considered. The application of computer technology in power quality control systems makes it possible to use rather complicated and effective algorithms of numerical processing of signals and significantly increase the accuracy of correction of disturbances in electric networks. The advantages and disadvantages of industrial plants constructed in the form of a controlled reactor with a dc magnetic bias and a reactor with a thyristor key are considered. Two types of devices to compensate for possible disadvantages are identified: devices using fully controlled keys and devices ones using artificial commutation and incompletely controlled power keys. A brief analysis of the known methods of electric power quality control is implemented. Recommendations for the establishment of power quality control systems are suggested in which the parameters of software depend on the solution algorithm of a posed problem, while the algorithm itself depends on the method of control and mathematical laws on which it is based. The method of control determines the structure of the power quality control system, while the software determines the basic operations of information processing, their quantity, the scheme of data processing, the volume data flows, etc.     

Experience gained with development of the instrumentation and control system for the PGU-410 power unit at the Krasnodar cogeneration station on the basis of the tornado-n distributed control system

The development of the instrumentation and control system for the PGU-410 power unit at the Krasnodar cogeneration station is discussed. Problems encountered in designing the process control system of a complex facility are considered, in particular, the need to integrate local control systems. Special attention is paid to the importance of setting up a united control area at such facilities.     

Guaranteed cost control for large‐scale systems under control gain perturbations

The guaranteed cost control problem of the decentralized robust control for large‐scale systems with the norm‐bounded time‐varying parameter uncertainties and a given quadratic cost function is considered. Sufficient conditions for the existence of guaranteed cost controllers are given in terms of linear matrix inequality (LMI). It is shown that decentralized local state feedback controllers can be obtained by solving the LMI. The problem of guaranteed cost control for large‐scale systems under the gain perturbations is also considered. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 43–57, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10265     

针对暂态电压稳定问题的自动电压控制系统与切负荷协调控制策略

建立了暂态电压稳定分析的微分代数方程组,并提出了应对暂态电压稳定问题的自动电压控制(automatic voltage control,AVC)体系下二级电压紧急控制与切负荷协调控制策略。该协调控制策略把低压切负荷作为与AVC体系下二级电压紧急控制并行的一种控制手段,在这种协调控制的过程中优先考虑采用二级电压紧急控制,当计算发现仅依靠二级电压紧急控制不能使系统保持暂态电压稳定的时候再采用切负荷控制。在PSAT仿真环境下建立了含AVC体系下二级电压紧急控制和切负荷控制的电力系统暂态电压稳定仿真模型,对广东电网748节点系统进行仿真,验证了所提出的控制策略和模型的正确性和有效性。     

A static frequency converter in composition of high-speed rectifier drive

The algorithm and structure of a converter for the sensor-free control of a high-speed synchronous motor with constant magnets is considered.     

计及广域信号多时滞影响的电力系统附加鲁棒阻尼控制

针对基于广域测量系统的多时滞电力系统低频振荡阻尼控制的研究不足以作为主要控制方法之一的鲁棒控制方法求解参数步骤复杂的缺陷,提出一种可直接求解控制参数的多时滞广域电力系统阻尼控制器的设计方法。利用Lyapunov-Krasovskii泛函理论推导出的多时滞系统稳定判据,将控制镇定问题转化为线性矩阵不等式的可行性问题,直接求解控制参数,避免了传统方法中利用智能算法迭代求解参数的不便。4机2区域系统的时域仿真结果表明,所提出的多时滞阻尼控制方案能有效抑制区间模式的低频振荡,提高电力系统的稳定性。     

基于观测器的控制时滞线性系统的最优跟踪控制

研究了控制时滞线性系统的二次型最优跟踪控制问题.首先将控制时滞系统转化为无时滞系统,再将最优跟踪问题转化成等价系统的最优调节问题.然后,通过求解Riccati方程,设计含动态观测器的前馈-反馈最优跟踪控制律,利用构造参考输入观测器解决了前馈补偿器的状态物理不可实现问题.仿真实例验证了所设计的最优跟踪控制律的有效性.     

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。     

Achieving more efficient control of boilers by taking technological constraints into account

The structure of a nonlinear system for control the superheated steam temperature taking technological constraints into account is considered. A solution is proposed that allows a larger stability margin of the automatic closed-loop control system to be obtained. The influence of additional tuning parameters on the quality of control is shown. The use of proposed solution makes it possible to make the control process more accurate and smooth, to take into account technological constraints, and achieve robustness of the control system with respect to coordinate and parametric disturbances.     

Scalar control systems for a traction induction motor

A brief review and comparative characteristics of scalar control systems for traction induction motors for using in the traction electric drive are presented. It is shown that, despite the obvious advantages of the systems of vector control and direct torque control, scalar control systems have found wide application. The operation features of scalar control systems with stability0 of absolute slip and a minimum of stator current are considered. Based on the equivalent circuit of an induction motor taking into account the stator and rotor iron loss, a comparative evaluation of the considered scalar control systems based on the criterion of the efficiency coefficient taking into account the temperature of the stator and rotor windings is presented. Simulation results in the MATLAB environment for an 11-kW induction motor are presented. It is established that scalar control systems operating under the principle of a stator current minimum have an advantage, as this maintains the desired torque value with higher values of efficiency coefficient, which decreases electromagnetic loads and power loss. It is shown that it is necessary to take into account the influence of windings temperature on the stator voltage and the parameters of the control system in connection with its affect on the minimum stator current and optimal absolute slip ensuring extremal control by current minimum.     

一种新型光伏逆变器及其控制方法

介绍了一种新型的光伏逆变器,可以工作在独立负载和并网运行两种模式。在两种模式下分别建立了逆变器简化的数学模型。独立负载模式下,主要考虑电压环控制,逆变器主电路的数学模型相当于一个二阶系统。并网运行模式下,主要考虑电流环控制,逆变器主电路可以简化成一个一阶系统。在两种模式下分别设计了相应的控制器,并给出了详细的控制方法。频域仿真结果证明了控制系统的稳定性。在实验室建立了3 kW的样机,运用DSP完成了环路运算及控制,获得了较好的实验结果。     

Analysis of stability and accuracy of a pulse-width current controller of an autonomous three-phase inverter

In this paper, a closed current control loop in a three-phase circuit consisting of electromotive force and inductive loads is considered. Difference equations for the loop are obtained. The stability and accuracy of the loop are investigated. Ways to increase the current control accuracy are found.     

电力系统故障恢复过程中的过电压控制

针对由空载和轻载线路恢复所引起的过电压问题,文中提出了基于灵敏度分析的确定最有效控制变量及其调节量的方法,引入了有效因子的概念,既考虑了控制变量的电压灵敏度,又综合考虑了设备本身和运行条件的约束及当前状态的调节裕度,确保控制过程中不会产生新的电压越限,通过由该方法确定的有效控制变量对过电压进行了校正,从而使所需的操作数目最少.对IEEE10机39节点测试系统的计算结果表明了该方法的有效性.     

Sensorless control of a linear reciprocating switched-reluctance electric machine

It is proposed to use a simple switched-reluctance electric machine that does not have windings or permanent magnets on a movable part to develop a linear reciprocating electric machine intended for use as an electric generator together with a free-piston internal-combustion engine. It is noted that one of the most difficult problems in the development of such a linear electric machine is the development of a control system. A sensorless control algorithm is considered. Information on the stator-phase inductance of the electric machine and its variation is used to determine the position of the movable part. For its estimation, probing voltage pulses of known duration are applied to the phase. The amplitude of the current pulses caused by them will be proportional to the phase inductance. A mathematical model of electromagnetic processes is used to test the efficiency of the proposed control algorithm and determine appropriate control parameters. Since stator phases have separate magnetic circuits and are not magnetically connected, the electromagnetic processes in each phase are considered independently. Model parameters are determined experimentally using an experimental prototype of the considered electric machine, for which the dependences of the phase flux linkage and the generated force on the phase current for different positions of the movable part are obtained. The results of the investigation of processes in the considered electric machine at different frequencies of the movable part are given. It is found that, at frequencies of the movable part close to the nominal frequency, the phase should be connected to the power supply even before the movable part reaches the extreme position. Control using probing pulses applied to the operating phase is impossible, because the level of these pulses does not reach the maximum value until the phase is switched on. In this case, it is necessary to use the probing pulses of another, nonoperating phase to determine the position of the movable part. Such an algorithm makes it possible to control a linear reciprocating switched-reluctance electric machine at both low and high frequencies of the movable part. The obtained results confirmed the correctness of the adopted approaches to the development of a sensorless control algorithm.     

Design of a robust load—frequency controller for interconnected power systems based on the singular-value decomposition method

A robust control scheme is presented for the load—frequency control of an interconnected power system with uncertain parameters. A combination of the singular-value decomposition (SVD) technique and the Riccati equation approach is adopted to design a robust controller. Stability analysis of the closed-loop interconnected system for all admissible uncertainties is considered. The effectiveness of the proposed robust control scheme has been verified through simulation studies on a two-area power system model. The performance robustness of the proposed control algorithm is compared with recent results and found to be much better.