Active disturbance rejection based load frequency control and voltage regulation in power systems

An active disturbance rejection controller (ADRC) is developed for load frequency control (LFC) and voltage regulation respectively in a power system. For LFC, the ADRC is constructed on a three area interconnected power system. The control goal is to maintain the frequency at nominal value (60Hz in North America) and keep tie line power flow at scheduled value. For voltage regulation, the ADRC is applied to a static var compensator (SVC) as a supplementary controller. It is utilized to maintain the voltages at nearby buses within the ANSI C84.1 limits (or ±5% tolerance). Particularly, an alternative ADRC with smaller controller gains than classic ADRC is originally designed on the SVC system. From power generation and transmission to its distribution, both voltage and frequency regulating systems are subject to large and small disturbances caused by sudden load changes, transmission faults, and equipment loss/malfunction etc. The simulation results and theoretical analyses demonstrate the effectiveness of the ADRCs in compensating the disturbances and achieving the control goals.     

Model-based analysis for the thermal management of open-cathode proton exchange membrane fuel cell systems concerning efficiency and stability

In this work we present a dynamic, control-oriented, concentrated parameter model of an open-cathode proton exchange membrane fuel cell system for the study of stability and efficiency improvement with respect to thermal management. The system model consists of two dynamic states which are the fuel cell temperature and the liquid water saturation in the cathode catalyst layer. The control action of the system is the inlet air velocity of the cathode air flow manifold, set by the cooling fan, and the system output is the stack voltage. From the model we derive the equilibrium points and eigenvalues within a set of operating conditions and subsequently discuss stability and the possibility of efficiency improvement. The model confirms the existence of a temperature-dependent maximum power in the moderate temperature region. The stability analysis shows that the maximum power line decomposes the phase plane in two parts, namely stable and unstable equilibrium points. The model is capable of predicting the temperature of a stable steady-state voltage maximum and the simulation results serve for the design of optimal thermal management strategies.     

Active disturbance rejection control: Applications in aerospace

Control of uncertain dynamical systems has been an area of active research for the past several decades and to this end,various robust control approaches have been proposed in the literature. The active disturbance rejection control (ADRC) representsone prominent approach that has been widely studied and applied for designing robust controllers in diverse areas of engineeringapplications. In this work, a brief review of the approach and some of its applications in aerospace are discussed. The resultsshow that the approach possesses immense potential to offer viable solution to reallife aerospace problems.     

Modeling,state estimation and nonlinear model predictive control of cathode exhaust gas mass flow for PEM fuel cells

Polymer electrolyte membrane fuel cells are efficient energy converters and provide electrical energy, water and oxygen depleted air with a low oxygen content as exhaust gas if fed with air. Due to their low emission of greenhouse gases and noise they are investigated as replacement for auxiliary power units currently used for electrical power supply on aircraft. Oxygen depleted air, called ODA-gas, with an oxygen concentration of 10–11% and a low humidity can be used for tank-inerting on aircraft. A challenging task is controlling the fuel cell system for generation of dehumidified ODA-gas mass flow while simultaneously keeping bounds and gradients on control inputs. This task is attacked by a nonlinear model predictive control. Not all system states can be measured and some states measured exhibit a significant time delay. A nonlinear state estimation strategy builds the entire system state and compensates for the delay. The nonlinear model predictive control and the state estimation are derived from the system model, which is presented. Simulation and experimental results are shown.     

缸内直喷汽油机的自抗扰轨压跟踪控制器设计

获得期望的共轨压力是保证缸内直喷发动机(GDI)稳定工作和喷油量精确控制的一个重要前提. 本文针对缸内直喷汽油发动机轨压控制问题, 首先通过动力学分析建立了共轨燃油喷射系统的数学模型; 由于系统中存在有较强的非线性和不确定性, 采用基于模型但对模型的精确形式依赖较小的自抗扰控制技术设计轨压跟踪控制器,其中线性扩张状态观测器(ESO) 对系统存在的总扰动和不确定性进行了估计, 非线性误差反馈控制(NLSEF) 则采用反馈补偿实现扰动的抑制. 最后, 通过给定不同的参考轨压对控制器的有效性进行验证, 仿真结果表明控制性能是满意的.     

Decentralized preview control for multiple disturbance rejection in HVAC systems

A decentralized preview controller is designed for temperature control of multizone indoor environmental spaces. A two-zone space heating system is considered. The physical system consists of a boiler, heat pumps, distribution network and two environmental zones. By assuming that the outdoor temperature variations are “previewable”, a decentralized preview controller is designed by using a parameter optimization method. The output responses of the resulting decentralized closed-loop bilinear system acted upon by single and multiple disturbances with and without preview action are compared. Also, results showing the robustness property of the controller, and the 24-hour building operation with unoccupied and occupied setpoint tracking using preview control are given.     

受侧滑和滑移影响的移动机器人自抗扰控制

对存在侧滑和滑移干扰问题的轮式移动机器人轨迹跟踪问题进行研究。首先利用移动机器人系统的运动学模型,通过设计其辅助运动学控制器,使得机器人的辅助速度渐近收敛到期望速度;然后利用反步法思想设计了基于动力学模型的一阶线性自抗扰控制（LADRC）,通过扩张状态观测器（ESO）实时估计和补偿机器人运行过程中的侧滑和滑移干扰,使得机器人的实际速度渐近收敛到辅助速度;最终使得移动机器人的轨迹误差渐近趋近于零。通过仿真及实验验证了所设计方法的有效性。     

凹印机多色套准系统自抗扰解耦控制

针对凹版印刷机对套准控制高精度和高稳定性的要求,提出了一种利用自抗扰控制(active disturbance rejection control,ADRC)技术设计多色套准系统解耦控制器的方法.首先,根据无轴传动模式下多色套准系统的工作机理,建立了多色套准系统的非线性耦合数学模型,并根据ADRC解耦规则推导了套准系统的解耦模型,得到了套准系统的阶数和静态解耦模型.其次,在套准系统阶数和静态解耦模型的基础上,利用ADRC策略对套准系统解耦控制器进行了设计.最后,仿真结果表明,所设计的ADRC解耦控制器能够很好地对各种系统干扰进行补偿,实现了多色套准系统的高精度控制,具有比PID控制器更好的控制性能.     

Disturbance rejection control of a fuel cell power plant in a grid-connected system

Interface of a fuel cell plant to power grid is challenging because of the high nonlinearities of the fuel cell plant and the power conditioning system (PCS). This paper focuses on the control of grid-connected solid-oxide fuel cell (SOFC) power plant that is subject to varying load and uncertain network parameters. To this end, Active Disturbance Rejection Control (ADRC) is utilized to improve the performance of the PCS consisting of a dc-dc converter and a dc-ac inverter. ADRC is used in the dc-dc converter to stabilize the dc link voltage and yield a robust performance against the nonlinearity. Used in the dc-ac inverter, ADRC eliminates the steady-state error and is insensitive to the high-frequency noise. Simulation results show that, for grid current control, ADRC achieves a more robust performance than the conventional proportional-integral (PI) controller. Moreover, the total harmonic distortions (THDs) of the output current controlled by ADRC are always below 5% in spite of the variation in the load demand and network parameters.     

Improved self-oscillating control of a quadratic buck converter for constant voltage applications

A great number of switching power supplies are used to provide a variable voltage for resistive-inductive loads. However, some applications in industry, require a regulated current with a constant voltage such as battery charging systems, LED drivers, and laboratory equipment for power converters connected to PV cells. Additionally, some constant voltage systems are intrinsically unstable, and therefore, they cannot be used without a closed-loop compensatory circuit. Hence, this article describes a novel smooth starter system behaving as a current source for constant voltage applications. The proposed technology is implemented by a quadratic buck converter, and then, a self-oscillating control technique is applied for performing the output current regulation of the converter, which is capable of aiding to improve the system performance, stabilize the overall system, protect the converter from transient current oscillations, and provide an acceptable control performance. In addition to practical aspects, soft starter methods and limitation of the constant voltage power converter are mentioned and described in this article. The designed structure has not only the advantages of smooth response and simplicity to construct but also performs a nearly zero steady-state error regulation. The power stage, the control scheme, and the modulator are explained in detail and validated by experiments.     

基于自抗扰迭代学习控制的开关磁阻电机转矩脉动抑制

针对开关磁阻电机双凸极结构和磁路饱和非线性导致开关磁阻电机转矩脉动大的问题,本文基于一种新型的数据驱动控制方法—–自抗扰迭代学习控制,将开关磁阻电机看成是空间重复运动对象,设计空间迭代域补偿机制用于抑制电机非线性特性所带来的换相转矩脉动,提出了基于空间域扩张状态扰动补偿机制的转矩分配控制策略.在无法精确获取电机非线性模型的情形下,设计了非线性转矩补偿器和电流控制器对各相电流进行精确补偿和精确跟踪控制.仿真研究表明,基于自抗扰迭代学习的控制策略能显著快速地抑制开关磁阻电机的转矩脉动,可望在开关磁阻电机的实际应用中发挥作用.     

Fault tolerant control with disturbance rejection and attenuation performance for systems with multiple disturbances

It is difficult to diagnose and accommodate the faults if disturbances and faults exist simultaneously in the controlled plants. In this paper, an anti‐disturbance fault tolerant control (FTC) scheme is presented for a class of nonlinear systems with both faults and multiple disturbances. The multiple disturbances are supposed to include two types including the uncertain modeled disturbances and norm bounded uncertain disturbances. A composite fault tolerant controller is constructed by integrating a fault accommodation from diagnosis observer with additional disturbance rejection and attenuation performance for two different types of disturbances. As a result, the fault can be accommodated and the multiple disturbances can be rejected and attenuated simultaneously. Simulations for a flight control system are given to show the efficiency of the proposed approach. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Feedforward based transient control in solid oxide fuel cells

In SOFCs, transient control of fuel utilization is achievable via input-shaping. In this paper, the approach is generalized to a feedforward control problem for second-order LTI systems with two inputs and one output. One is a measurable, time-varying, exogenous input and the other is a control input. The problem studied is exact tracking of a constant reference using the plant's DC gain vector. The problem considers plant models that can be divided into known and unknown parts, and where feedback is unavailable. Although SOFCs have nonlinear dynamics, the linear abstraction nevertheless helps predict the observed effectiveness of input-shaping.     

An improved Backstepping technique using sliding mode control for transient stability enhancement and voltage regulation of SMIB power system

The problem of transient stability and voltage regulation for a single machine infinite bus (SMIB) system is addressed in this paper. An improved Backstepping design method for transient stability enhancement and voltage regulation of power systems is discussed beginning with the classical Backstepping to designing the nonlinear excitation control of synchronous generator. Then a more refined version of this technique will be suggested incorporating the sliding mode control to enhance voltage regulation and transient stability. The proposed method is based on a standard third-order model of a synchronous generator connected to the grid (SMIB system). It is basically implemented on the excitation side of the synchronous generator and compared to the classical Backstepping controller as well as the conventional controllers which are the automatic voltage regulator and the power system stabiliser. Simulation results prove the effectiveness of the proposed method which ameliorates to a great extent the transient stability compared to the other methods.     

Adaptive policies for discrete-time stochastic control systems with unknown disturbance distribution

We introduce adaptive policies for discrete-time, infinite horizon, stochastic control systems x₁₊₁ = F(x₁, a₁, ξ₁, T =0, 1, …, with discounted reward criterion, where the disturbance process ξ₁ is a sequence of i.i.d. random elements with unknown distribution. These policies are shown to be asymptotically optimal and for each of them we obtain (almost surely) uniform approximations of the optimal reward function.     

Adaptive control strategy with flux reference optimization for sensorless induction motors

Avoiding mechanical (speed, torque) sensors in electric motor control entails cost reduction and reliability improvement. Furthermore, sensorless controllers (also referred to output-feedback) are useful, even in the presence of mechanical sensors, to implement fault tolerant control strategies. In this paper, we deal with the problem of output-feedback control for induction motors. The solutions proposed so far have been developed based on the assumption that the machine magnetic circuit characteristic is linear. Ignoring magnetic saturation makes it not possible to meet optimal operation conditions in the presence of wide range speed and load torque variations. Presently, an output-feedback control strategy is developed on the basis of a motor model that accounts for magnetic saturation. The control strategy includes an optimal flux reference generator, designed in order to optimize energy consumption, and an output-feedback designed using the backstepping technique to meet tight speed regulation in the presence of wide range changes in speed reference and load torque. The controller sensorless feature is achieved using an adaptive observer providing the controller with online estimates of the mechanical variables. Adaptation is resorted to cope with the system parameter uncertainty. The controller performances are theoretically analyzed and illustrated by simulation.