Study on outlier robustness of minimum variance control performance assessment

Minimum variance (MinVar) method for control performance assessment constitutes one of the most common approaches to the control quality estimation. There are dozens of versions, enriched with numerous reported industrial implementations. MinVar methodology uses the idea of minimum variance, which has been introduced by Kalman. Therefore, it should be remembered that MinVar concept relies on the same assumptions as an idea of the minimum variance control. Among other assumptions, it is essential that the modeled disturbance is an independent random sequence. This article addresses scenarios, when loop noise exhibits non-Gaussian properties and is characterized by outliers having fat-tailed distribution. Sensitivity analysis of minimum variance method against such disturbances is evaluated using commonly used PID SISO control benchmarks. It is shown that MinVar method may be significantly biased in such non-Gaussian situations, which are very frequent in the industrial reality. Reasons of the biased performance are traced and respective solutions are proposed.     

Output power control of wind turbine generator by pitch angle control using minimum variance control

Effective utilization of renewable energies such as wind energy as a replacement for fossil fuels is highly desirable. Wind energy is not constant and wind generator output is proportional to the cube of the wind speed, which causes the power output of wind turbine generators (WTGs) to fluctuate. In order to reduce output power fluctuations of wind farms, this paper presents an output power leveling control strategy for wind farms based on both the mean and the standard deviation of wind farm output power, a cooperative control strategy for WTGs, and a pitch angle control method using a generalized predictive controller (GPC) intended for all operating regions of WTGs. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 10–18, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20247     

基于最小方差基准的励磁系统性能评估

对同步发电机励磁系统性能评价一般通过阶跃响应方法,但该方法无法在线进行,为此提出了最小方差控制基准的性能评估方法。对系统设计最小方差控制器并作为系统控制性能上限,与系统实际性能进行比较而得到性能指标,并对该方法进行系统滤波和相关性分析FCOR(Filtering and Correlation Analysis)算法的改进,避免了Diophantine方程的展开运算。分析表明该评估方法只需利用同步发电机输出端电压数据,结合系统时滞d就可以得到励磁系统的性能指标。仿真结果表明该方法简化了计算过程,能够及时准确地在线评估励磁系统的控制性能。     

A weighted adaptive one-step-ahead minimum variance controller based on the ELS algorithm

This paper deals with the design of a weighted adaptive one-step-ahead minimum variance controller based on the extended least squares (ELS) algorithm for a discrete time stochastic system. The stability of the closed-loop system and the convergence rates of the general adaptive tracking and estimation errors are respectively established under strictly positive real and minimum phase conditions. The best possible convergence rate of the average error between the predicted and desired outputs is obtained given some identifying condition and the above-stated conditions. No modification of the adaptive controller is made. © 1997 by John Wiley & Sons, Ltd.     

基于遗传算法的混沌系统多模型微扰控制

针对基于遗传算法的混沌系统多模型控制问题,为扩大控制器在吸引子中的作用范围,采用遗传算法引导混沌轨道的方法产生多模型控制策略,能使混沌系统在小的扰动作用下迅速从某一初始点到达目标点。对含有不确定参数的Henon混沌系统仿真表明,与其他方法相比能在更短的暂态时间内把系统控制到预定轨道。     

基于自抗扰串级控制的蒸汽发生器水位多模型控制方法

提出了基于自抗扰串级控制的蒸汽发生器水位多模型控制方法,其内回路采用比例控制,以快速消除给水扰动,而外回路采用二阶自抗扰控制,利用扩张状态观测器对系统的内扰和外扰实时估计,采用前馈方式给予补偿,并通过非线性反馈控制改善控制系统的快速性和稳定性。原串级控制结构不变,但外回路采用多模型自抗扰控制,从而实现全工况运行的自适应控制。仿真结果表明所提控制方法能实现大范围内平滑、快速、精确控制,其系统的鲁棒性和抗干扰能力优于常规串级PID控制方法。     

Bilinear models in adaptive control

A key issue, which is addressed in the paper, is the development of an efficient adaptive control algorithm for disturbed, non‐linear objects. A generalized non‐linear model of the controlled plant is proposed. Model of disturbances is assumed to be a bilinear time‐series model. Minimum‐variance control of non‐linear systems with bilinear model of disturbances is considered. For a generalized system model simple, weighed and generalized adaptive control algorithms are proposed. A comparison of different non‐linear adaptive control algorithms is performed. Copyright © 2000 John Wiley & Sons, Ltd.     

A study of decoupling with skeleton matrix in two‐degree‐of‐freedom generalized minimum variance control

There are many multi‐input multi‐output (MIMO) systems in chemical plants, and they have multiple time delays of different length in each input and output pair. This paper explains a two‐degree‐of‐freedom (2DOF) control system based on generalized minimum variance control (GMVC) for MIMO systems. It can improve the tracking performance with respect to the reference signals and the response properties for the disturbance. The states between the sampling period can be expressed by using the modified z transform to take account of multiple time delays. Additionally, a tracking controller is designed to decouple the plant. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(1): 28–36, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21046     

火电厂主蒸汽温度系统的多模型PID控制

针对火电厂主蒸汽温度的时变性特征,设计了基于多模型的串级PID控制系统,并以某电厂锅炉5个局部工作点的主蒸汽温度为对象进行了仿真。仿真结果表明,基于多模型的串级PID控制策略能够较好的解决主蒸汽温度的时变性问题,其控制效果也相对较好。     

三电平PWM整流器多模型预测控制方法

针对PWM整流器滤波电感、等效电阻等参数失配时高性能控制问题,在模型预测控制的基础上引入多模型自适应环节,提出一种三电平PWM整流器多模型预测控制方法。在该方案中,根据整流器模型参数实测值及其波动范围建立多模型集,由各子模型预测输出与整流器系统实际输出偏差,确定与实际系统模型匹配度较高的多个子模型,加权求和后即可确定最优系统参数。针对多模型自适应控制与模型预测控制相结合引起的大负荷在线计算问题,提出一种在线优化多模型预测控制方法,分别设计了在线优化移动子集和多电平快速预测控制方法对其进行简化。最后,实验结果表明所提控制策略的正确性和有效性。     

多模自适应WIFI无线图构建与定位方法

针对室内情况复杂,单一方法难以对WIF1信号强度(RSS)的无线分布图(RM)准确估计建模,导致基于RSS分布模型的WIFI室内定位方法精度无法有效提高的问题,提出多模自适应的WIFI无线图构建与定位方法.创建多项式RSS分布模型并与多种电波室内传播模型结合构成多模候选集,通过最小二乘法计算各模型参数的最优无偏估计值,以模型预测残差为依据自动选择最佳分布模型构建无线图并用于定位.实验表明该方法能更准确估计出WIFI信号的室内分布情况,有效提高WIFI室内定位精度.     

1000MW超超临界机组汽温多模型预测控制研究

针对电厂过热汽温对象大惯性、大滞后及参数随负荷变化显著的特点,利用非线性过程(线性不确定过程)在多个工作点上的线性化模型,把整个对象工作空间划分为若干子空间,而每个子空间可以找到一个较精确的固定模型,再通过加权子模型获得复杂对象的全局近似模型作为预测模型,然后采用线性优化或非线性优化方法计算预测控制器输出进行汽温控制,并给出具体的现场应用实施方案。实际仿真和应用结果证明无论对于稳态过程或负荷变化过程,过热汽温都能维持在要求的控制范围内,能够有效保证机组的安全经济运行。     

Limits of control performance for distributed networked control systems in presence of communication delays

In terms of computational complexity and fault tolerance, distributed networked control systems (DNCSs) is favorable for large‐scale processes. However, it poses additional limitations on the achievable control performance, especially when communication delay is present. The conventional minimum variance (MV) benchmarks mainly consider the limitations caused by the system itself and can give overly estimates of achievable performance when applied to the systems under distributed networked control. This paper proposes a solution to the MV benchmark for DNCSs considering both system time delays and time‐invariant communication delays. Furthermore, lower and upper bounds of the MV benchmark are proposed to assess the performance of DNCSs when there are time‐varying communication delays. These results are useful for evaluating the potential performance improvement if a DNCS is implemented to replace a decentralized control system. The proposed results are illustrated by a simulation example.     

基于LMI方法的VSC-HVDC多重模型阻尼控制器设计

电压源换流器式高压直流输电(VSC-HVDC)具有快速功率调整特性,结合相应附加小信号阻尼控制策略可以提高系统的低频阻尼能力。基于线性矩阵不等式(LMI)的优化方法为电力系统阻尼控制提供了新的设计途径。文中采用2步LMI优化方法,在建立系统多个运行点小信号模型基础上分别设计单一模型和多重模型运行点阻尼控制器,以改善系统阻尼特性。在PSASP中对3机系统的时域仿真分析表明,基于多重模型的阻尼控制器具有较强的适应性,可在大范围运行条件下向系统提供足够的阻尼。     

A design scheme of discrete robust PID control systems and its application

PID controllers have been widely used in many chemical processes. Because they have only three control parameters, we can easily understand their physical meanings. However, it is difficult to tune their parameters in the case where the control system has uncertainties, for example, modeling errors, system fluctuation, and so on. Therefore, we propose a design scheme of discrete robust PID controllers in this paper. That is, we design a PID controller in connection with the generalized minimum variance control (GMVC) scheme, and present a scheme on how to design a weighting factor included in the GMVC criterion from the viewpoint of robust stability. Furthermore, we investigate the behavior of the proposed control scheme by applying it to an air pressure control system. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 77–83, 1999     

基于状态变量多模型的主汽温控制系统

针对主汽温系统大惯性、非线性的特点,提出了基于状态变量多模型的控制方案,即先采用状态反馈补偿主汽温系统的惯性,同时调整状态反馈系数矩阵,使得补偿后被控对象开环稳态增益稳定不变;再针对不同工况下对象特性的变化,对各工况控制子系统进行模态综合,以PID作为控制器,实现大范围控制.对主汽温系统的仿真结果表明,该方案可以较好地解决系统的大惯性和非线性问题.     

球磨机多模型PID型神经元网络控制系统

针对球磨机制粉系统的多变量、强耦合、非线性、时变性等特点,提出了采用基于PID型神经元网络的多模型控制方法,在不同工况下系统的时变特性采用多个模型进行描述,而每个模型的控制器则采用PID型神经元网络进行解耦控制。通过在线计算模型匹配程度,选择相应的模型和控制器,组成闭环系统,切换算法实现多模型间无扰切换,同一工况慢时变采用控制器参数自调整来提高鲁棒性。PID型神经元网络是一种特殊的3层前向神经网络,其隐层单元分别为比例(P)、积分(I)和微分单元(D),各层神经元个数、连接方式、连接权值的初值按PID控制规律确定。仿真结果表明,文中提出的控制方法相比传统控制方法有更好的控制品质,跟踪快、鲁棒性强、解耦好,较好地解决了球磨机系统的时变性、耦合性等问题。     

基于鲁棒方差优化的电力系统频率控制研究

随着新能源发电大规模并网,随机负荷扰动给电力系统稳定优化运行提出了新的挑战。针对自动发电控制过程中存在的随机扰动和参数摄动的问题,提出了一种基于鲁棒方差约束的状态反馈控制器的参数优化方法。根据鲁棒方差控制(Robust Variance Control,RVC)中不等式约束条件,分析了闭环系统在抑制随机扰动和提高阶跃扰动响应动态性能之间的博弈关系。构造了融合稳态状态方差和控制能量输出约束的优化问题,利用线性矩阵不等式(Linear Matrix Inequality,LMI)获得了鲁棒方差控制器参数。在此基础上,对配置的区域极点圆心坐标值和正标量两个参数进行遗传优化,得到性能指标最优的控制策略。以两区域电力系统模型为例,表明该方法能够有效抑制随机扰动并保持良好的控制性能和鲁棒性能。     

Discrete-time combined model reference adaptive control

The discrete-time version of continuous-time combined model reference adaptive control (CMRAC) is presented in this paper. A global stability proof of the overall adaptive scheme is given using arguments similar to those used in discrete-time direct model reference adaptive control (DMRAC) but properly modified to account for the different structure of CMRAC with respect to DMRAC. © 1997 by John Wiley & Sons, Ltd.     

基于动态解耦的模糊多模型协调控制系统应用研究

大型火电单元机组的协调控制对象是一个多变量、强耦合的控制对象,针对此对象设计合适的解耦控制器是急需解决的问题。由于非线性系统可以用多个线性模型来逼近,多模型方法被认为是处理非线性系统常用的方法和技术。该文以330MW单元机组为仿真模型,针对协调控制系统的非线性和耦合等特性,首先建立协调控制系统的非线性模型,然后对此模型在3个工况点下进行线性化,设计与之对应的多变量动态解耦控制器,进而用T-S模糊模型合成出模糊多模型全局控制系统。仿真研究结果证明了这种新型协调控制系统的有效性。