采用自适应电力系统稳定器提高输电系统稳定性

对电力系统稳定器的设计方法、性能特点作了讨论。仿真实验表明,高阶、非线性输电系统可用低阶、线性模型来表示,且模型的参数可用最小二乘法来辨识;极点移动的自校正调节器最适合电力系统应用;同传统的PSS相比,自适应电力系统稳定器,提供了更好的阻尼。提出解决干扰出现后辨识器参数不能收敛问题的一种新方法:首先模拟各种可能出现的大干扰,辨识出系统在这些状态下的参数值并存于计算机中;系统一旦出现大干扰时,可借助继电保护信号迅速地判断干扰的类型,然后将相应的参数值调出,设计控制器,计算控制作用。仿真结果表明,这种措施能保证系统在出现大干扰的情况下,具有良好的动态响应。     

Role of CD4+ T Cells in the Control of Viral Infections: Recent Advances and Open Questions

CD4+ T cells orchestrate adaptive immune responses through their capacity to recruit and provide help to multiple immune effectors, in addition to exerting direct effector functions. CD4+ T cells are increasingly recognized as playing an essential role in the control of chronic viral infections. In this review, we present recent advances in understanding the nature of CD4+ T cell help provided to antiviral effectors. Drawing from our studies of natural human immunodeficiency virus (HIV) control, we then focus on the role of high-affinity T cell receptor (TCR) clonotypes in mediating antiviral CD4+ T cell responses. Last, we discuss the role of TCR affinity in determining CD4+ T cell differentiation, reviewing the at times divergent studies associating TCR signal strength to the choice of a T helper 1 (Th1) or a T follicular helper (Tfh) cell fate.     

On the fragility of fractional-order PID controllers for FOPDT processes

This paper analyzes the fragility issue of fractional-order proportional-integral-derivative controllers applied to integer first-order plus-dead-time processes. In particular, the effects of the variations of the controller parameters on the achieved control system robustness and performance are investigated. Results show that this kind of controllers is more fragile with respect to the standard proportional-integral-derivative controllers and therefore a significant attention should be paid by the user in their tuning.     

Data-driven and adaptive control applications to a wind turbine benchmark model

Wind turbines are complex dynamic systems forced by stochastic wind disturbances, as well as gravitational, centrifugal, and gyroscopic loads. Since their aerodynamics are nonlinear, wind turbine modelling is thus challenging. Moreover, accurate models should contain many degrees of freedom to capture the most important dynamic effects. Therefore, the design of control algorithms for wind turbines should account for these complexities. However, these algorithms must capture the most important turbine dynamics without being too complex and unwieldy. The main purpose of this study is thus to give two examples of viable and practical designs of control schemes with application to a wind turbine prototype model. Extensive simulations on the benchmark process and Monte-Carlo analysis are the tools for assessing experimentally the main features of the proposed control schemes, in the presence of modelling and measurement errors. These developed control methods are also compared with other different approaches, in order to evaluate advantages and drawbacks of the considered solutions. Finally, Hardware-In-the-Loop simulations serve to highlight the potential application of the proposed control strategies to real wind turbines.     

Output feedback control of large-scale nonlinear time-delay systems in lower triangular form

This paper is concerned with the stabilization problem for a class of large-scale nonlinear time-delay systems in lower triangular form. The uncertain nonlinearities are assumed to be bounded by continuous functions of the outputs or delayed outputs multiplied by unmeasured states or delayed states. An observer based output feedback control scheme is proposed using the dynamic gain control design approach. Based on Lyapunov stability theory, global asymptotic stability of the closed-loop control system is proved. Contrary to many existing control designs for lower triangular nonlinear systems, the celebrated backstepping method is not utilized here. An example is finally given to demonstrate the effectiveness of the proposed design procedure.     

Subspace Identification of Transfer Function Models for an Unstable Bioreactor

This work deals with the identification of transfer function model of an unstable bioreactor by a subspace-based identification method. The data set is generated from the simulated closed loop system by giving a random signal at the reference signal. The linear system matrices are estimated through the Multivariable Output Numerical algorithms for Subspace State Space System Identification (MON4SID) algorithm. The delay is estimated directly from the input–output data by the impulse response method. The identified First Order Plus Time Delay (FOPTD) model is compared with the locally linearized transfer function model derived around the unstable operating point. A Proportional Integral Derivative (PID) controller is designed for the identified model using the equating coefficient method. The closed loop servo and regulatory responses show that the model identified by MON4SID is similar to the linearized model and the optimization method.     

基于以太网的嵌入式控制器设计

针对传统以太网难以胜任工业控制中硬实时要求的问题,提出了一种确保以太网在工业控制中实时性的措施.介绍了基于以太网的嵌入式控制器设计的整体方案,并以ATMEL公司的AT91M 40800芯片为核心,设计开发了嵌入式控制器的硬件平台,并提出一些设计中存在的问题,以期在今后的研究中逐步完善.     

开关式直流功率变换器的非线性控制器设计

将非线性控制的逆系统方法应用于脉宽调制（ＰＷＭ）控制的变换器，并借助于变换器的非线性无穷大频率平均模型，提出了变换器非线性控制的逆系统设计方法，推导出了变换器的非线性控制规律。通过对升压式变换器的计算机仿真分析，说明了变换器非线性控制的调节性能     

基于dSPACE的大型风电机组系统控制器测试平台的研制

为了解决大型风电机组系统控制器的试验室闭环测试问题，利用硬件在环实时仿真技术，研制了基于dSPACE的全数字化测试平台。以一台1．5MW变速变桨双馈风电机组的控制为例，介绍了硬件在环测试平台的搭建过程。试验结果表明，开发的测试平台能够对系统控制器的起停运转、各种运行状态的控制和切换以及故障保护等功能进行有效的测试。