UPFC状态反馈精确线性化潮流控制策略

统一潮流控制器(unified power flow controller,UPFC)传统线性控制器的性能可能因运行点的大范围变化而恶化,针对该问题提出了一种基于微分几何状态反馈精确线性化理论的UPFC非线性潮流控制策略。通过选择李雅普诺夫型输出函数、适当的非线性坐标变换和状态反馈将UPFC的5阶非线性系统完全转化为一个线性系统,然后采用线性极点配置方法设计了UPFC内部潮流控制器。IEEE 118节点系统的仿真对比结果表明,所提UPFC潮流控制策略改进了传统PI控制近似线性化的缺陷,有效适应了UPFC控制范围的大幅度变化,在提高电力系统暂态稳定性方面的效果明显优于传统PI控制。此外,该控制策略设计过程可以应用于所有基于电压源型换流器(voltage source converter,VSC)的柔性交流输电系统(flexibleAC transmission system,FACTS)装置。     

Nonlinear excitation control of a synchronous generator with implicit terminal voltage regulation

The objective of this paper is to design nonlinear excitation controllers for single-machine infinite-bus power systems. Because of the nonlinear nature of such systems, nonlinear controllers are more effective in providing larger stability margins than their linear counterparts. To take advantage of well-developed linear control techniques, the concept of feedback linearization is used. A characterization of the region over which the linearizing state transformation is guaranteed to be diffeomorphic is provided. Also, a new formulation for the linear controller design is provided to solve the problem of the terminal voltage regulation. Simulation results of a single-machine infinite-bus power system indicate that in the presence of major disturbances the proposed controller outperforms existing linear and nonlinear controllers in maintaining the system's stability, in damping the rotor angle oscillations, and in reaching the desired performance during postfault operations.     

发电机的非线性综合控制

本文在坐标变换和反馈控制理论的基础上，提出了扩展直接反馈线性化的方法。在综合考虑励磁系统和调速系统作用的同时，推导设计了一种实用的发电机非线性综合控制器。计算机仿真研究表明，该控制方式不仅可以有效地改善电力系统的动态响应，而且可以显著地提高系统的暂态稳定极限。     

Power system transient stability enhancement by STATCOM with nonlinear H∞ stabilizer

A robust control design is presented for a single machine infinite bus system (SMIB) with a STATCOM. The controller for the nonlinear system is designed using the recently developed nonlinear H_∞ theory. The approach combines state feedback exact linearization with linear H_∞ principle, which avoids the difficulty of solving Hamilton–Jacoby–Issacs inequality. Simulation results with a number of disturbances like torque pulses and three-phase faults on the generator show that the proposed robust controller can ensure transient stability of the power system over a wide range of operating points     

A decentralized nonlinear feedback controller with prescribed degree of stability for damping power system oscillations

Nonlinear feedback linearization techniques are being used for transforming nonlinear power system dynamics into closed loop systems, whose dynamics are linear over wide range of operating conditions. This facilitates use of linear techniques for designing feedback controllers to damp out oscillations. The advantage of using such feedback controllers is that they do not depend on the system operating conditions unlike the conventional controllers, for example a conventional power system stabilizer. A nonlinear feedback law is proposed in this work, which converts a nonlinear power system into closed loop decentralized linear time varying systems. A feedback controller has been designed using linear quadratic regulator with prescribed degree of stability to stabilize the decentralized linear time varying systems. The performance of the proposed method has been tested on a 16-machine, 68-bus system representing interconnected New England Test system (NETS) and New York Power System (NYPS).     

基于线性最优控制理论的励磁系统的设计及仿真

基于单机无穷大系统的线性化模型,结合线性最优控制理论建立了最优励磁控制器用的系统状态方程,求出线性最优励磁控制电力系统稳定器,用Matlab仿真软件在单机无穷大系统两种不同的运行状态下进行仿真,结果表明最优励磁控制具备了良好的电压性能,且给出了比AVR＋PSS更强的阻尼,表现出良好的动态特性。     

非线性状态PI励磁控制器

利用扩张状态观测将原来的非线性系统变换成线性系统,然后用状态PI控制器的设计思想设计了非线性状态PI控制器;并将其用于发民机励磁控制,以及解决电力系统的强非线性和不确定性问题,避免了反馈线性化非线性励磁控制由于数学模型的误差而影响控制器性能的特点。所得控制规律与系统运行点和网络结构完全无关,同时控制器结构简单。仿真计算表明,非线性状态PI励磁控制器对系统运行点和网络结构变化具有良好的适应能力,可以有效地改善系统的稳定性。     

基于零动态和变结构控制的发电机汽门和励磁非线性综合控制

针对电力系统暂态过程的非线性特性,利用励磁控制和汽门控制的特点,以功角和电压稳定为目标提出一种发电机汽门和励磁综合控制思想。励磁控制以稳定电压为目标,结合基于零动态和变结构控制的概念和原理进行设计,有效地维持了电压水平。汽门控制以功角稳定为目标,通过计算零动态系统的暂态能量函数,利用Lyapunov稳定理论,得到稳定流形作为切换面,然后设计相应的变结构非线性汽门控制律,将零动态系统限制在所设计的稳定流形上。变结构控制的特性使控制律具有一定的鲁棒性。汽门控制设计中未使用任何线性化方法,因而控制律对系统的非线性特性完全适应。试验结果表明所设计的控制器不仅对小干扰和大干扰暂态过程具有很好的稳定作用,而且在动态过程中能很好地稳定电压,动态过程具有更好的供电品质。     

基于暂态能量函数的电力系统非线性鲁棒滑模励磁控制

针对电力系统暂态过程的非线性特性,以功角稳定为目标设计了一种状态反馈非线性滑动模励磁控制器.通过直接计算系统的暂态能量函数,利用Lyapunov稳定理论,得到稳定流形作为切换平面,然后设计相应的滑动模励磁控制律,将系统限制在所设计的稳定流形上.在设计时考虑了对系统参数不稳定性,从而控制律具有一定的鲁棒性.设计中未使用任何线性化方法,因而控制律对系统的非线性特性完全适应.仿真结果表明所设计的控制器不仅具有良好的小干扰稳定性,而且对于大干扰暂态过程也具有很好的抑制作用.     

多机电力系统神经网络最优励磁控制器

针对多机电力系统，提出了一种基于辨识的神经网络实时最优控制器(NNOEC)，在所设计的控制器中，神经网络被用来根据系统状态量的变化实时调整最优控制的反馈增益矩阵，使控制器能够适应不同的运行点和干扰种类。并始终提供最优控制输出。针对多机系统中神经网络训练样本不易获得的问题，提出了一种等效的设计方法，并采用非线性最小二乘辨识法对系统参数进行辨识，在辨识的基础上通过线性最优控制理论计算出用于神经网络训练的样本。三机系统中的数字仿真结果表明，所训练出的NNOEC能够适应系统运行方式的大范围变化，在大小扰动下均表现出良好的控制性能。     

Full-state Variables Control of a Grid-connected Pumped Storage Power Plant Using Non-linear Controllers

Abstract—In this article, a controller based on a multi-variable sliding mode is provided for pumped storage with four goals. (1) Full-state variables of the plant, generator, and hydro turbine are developed to improve transient responses under fault conditions by compensating the fast electrical dynamics. (2) The sliding-mode controller is designed for robustness against uncertainty in both the power system parameters and its topology. (3) Two surfaces (power angle and output voltage) are proposed to coordinate both the turbine and excitation inputs of the generator in transient conditions. (4) The decentralized method is used to decrease the complexity of the controller equations and cost of implementation. To show the effectiveness of the proposed controller, two other controllers—full-state variables feedback linearization and a generic power system stabilizer—are simulated by MATLAB/Simpower (The MathWorks, Natick, Massachusetts, USA). The simulation results show full-state variables feedback linearization cannot be robust against model uncertainty; it is also shown that the power plant with linear controller has unpleasant transient responses in both fault conditions and low-frequency oscillations. In contrast, the proposed method plays an effective role in solving the mentioned problems and limits the stator current magnitude and terminal voltage post-fault.     

带电压调节功能的非线性鲁棒控制器

提出了一种既可增加多机电力系统暂态稳定性又可达到机端输出电压调节功能的非线性鲁棒控制器。该控制器由一个直接反馈线性化（DFL）控制器和一个比例积分（PI）控制器组成。DFL控制器用于降低多机电力系统的非线性程度以及各机之间的相互作用。所提控制器设计方法既可保证系统稳定性又可达到调节电压的目的,同时在实现时不需要测量发电机功角。仿真结果表明,所提出的方案可在很宽的运行范围内增加系统的阻尼及稳定性。     

计及非线性负荷的AC/DC系统控制策略

详细研究了带非线性负荷的交直流并联系统发电机励磁控制和直流系统控制,将M导数、M括号以及MIMO微分代数系统反馈线性化技术应用到交直流并联多机系统非线性控制器设计中,提出了具有微分代数形式的零动态设计.通过合理选择输出量作为坐标变换量,得到微分代数系统模型的Bronovsky标准形式.针对一个含有AC/DC的多机系统进行仿真, 研究结果表明,所设计的非线性控制器与传统的PID控制器相比具有较好的阻尼特性, 该控制器能进一步提高系统的动态稳定性.     

Speed deviation driven adaptive neural network based power system stabilizer

The paper presents an online adaptive artificial neural network (ANN) based power system stabilizer (PSS). The proposed controller is first trained offline using a pole placement based state feedback gain technique at different operating points. The trained ANN parameters (weights and biases) are updated and tuned online using the speed deviation as the reinforcement signal. The proposed PSS is tested at different operating conditions and a variety of regulator gains. The digital results validate the effectiveness and reliability of the new PSS in terms of fast system response under different loading conditions compared with the conventional PI controller and the modern control theory approach of pole placement.     

统一潮流控制器的自适应校正稳定控制器设计

在装设了统一潮流控制器(unified power flow controller,UPFC)的弱阻尼连接多机系统中,综合利用全系统的线性化状态方程和传递函数的信息,设计了线性化的UPFC稳定控制器。为使该稳定控制器能在系统大范围内的运行点提供有效阻尼,文中在UPFC稳定控制器中加入一可调的超前(滞后)环节,利用Prony分析在线辨析系统低频振荡特性。利用在线辨析的结果对稳定控制器的可调环节进行微调,使之针对系统具体运行工况进行自适应校正,从而持续工作在最佳状态。最后利用电磁暂态仿真程序对一个装设有UPFC的两区域弱阻尼连接系统进行了仿真计算。仿真结果表明,文中设计的自适应校正UPFC稳定控制器能够明显提高该系统的阻尼水平。     

Wide area stabilization of a magnetic bearing using exact linearization

An active magnetic bearing (AMB) is a bearing used to suspend a rotor by magnetic forces without any contact. Feedback control is indispensable for a magnetic bearing, because it is essentially an unstable system. To design a feedback control system, a linear mathematical model of the plant is convenient; however, the force of the electromagnet is highly nonlinear. Thus, usually a linear approximation around the operating point is employed, but the obtained linearized model cannot express the exact behavior of the system at any other operating points. In this paper, we discuss the wide area stabilization of magnetic bearings using the exact linearization approach. First, we derive a nonlinear mathematical model for a magnetic bearing, then we show that this nonlinear system belongs to a class of exactly linearizable nonlinear systems. Next, by using the exact linearization method, we transfer the nonlinear model of a magnetic bearing to a linear time‐invariant state model in spite of change of the operating point and the rotational speed of the rotor. Then we construct the state feedback control system by the conventional LQ method. Finally, we evaluate the validity of our proposed method by experiments. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 53–62, 1999     

Improved synergetic excitation control for transient stability enhancement and voltage regulation of power systems

This paper proposes decentralized improved synergetic excitation controllers (ISEC) for synchronous generators to enhance transient stability and obtain satisfactory voltage regulation performance of power systems. Each generator is considered as a subsystem, for which an ISEC is designed. According to the control objectives, a manifold, which is a linear combination of the deviation of generator terminal voltage, rotor speed and active power, is chosen for the design of ISEC. Compared with the conventional synergetic excitation controller (CSEC), a parameter adaptation scheme is proposed for updating the controller parameter online in order to improve the transient stability and voltage regulation performance simultaneously under various operating conditions. Case studies are undertaken on a single-machine infinite-bus power system and a two-area four-machine power system, respectively. Simulation results show the ISEC can provide better damping and voltage regulation performance, compared with the CSEC without parameter adaptation scheme and the conventional power system stabilizer.     

基于模糊滑模控制理论的SSSC控制器的研究

提出了一种静止同步串联补偿器(Static Synchronous Series Compensator,SSSC)的模糊滑模控制器设计方法,控制目标是阻尼系统功率振荡。建立装有SSSC的单机系统数学模型,采用状态反馈精确线性化方法,将非线性的数学模型转化成线性的形式,运用分散滑模控制理论和模糊控制理论进行SSSC模糊滑模控制器的设计。对含有SSSC的单机无穷大系统进行三相短路故障仿真,仿真结果表明本文设计的模糊滑模控制器能快速有效地阻尼系统功率振荡。     

逆系统方法在TCSC稳定控制中的应用

简单介绍了基于坐标变换和反馈控制理论的一种反馈线性化方法－逆系统方法。运用逆系统方法将含可控串联补偿电容器（TCSC）的非线性电力系统线性化,并且对该线性化的系统运用具有二次型性能指标的线性最优控制方法设计了TCSC的稳定控制器,将其与用微分几何法和用直接大范围线性化法设计的控制器进行了比较,结果表明它们具有相同的控制效果,即均能提高电力系统的暂态稳定性。     

基于ESO-backstepping的多机电力系统非线性鲁棒励磁解耦控制

通过构造扩张状态观测器(extended state observer,ESO)对发电机励磁系统模型误差和不确定外扰进行动态补偿,并运用反步法对补偿后的模型设计非线性解耦控制律。由于该方法对系统模型的非线性部分有选择地利用ESO进行动态补偿,既避免了运用反步法设计时自适应参数的引入,又能充分利用系统的特性,减轻ESO的估计负担,有效地兼顾了控制器鲁棒性及控制精度这两方面的要求。仿真表明：该方法鲁棒性强,参数易于选取,与比例–积分–微分(proportion-integration- differentiation,PID)+电力系统稳定(power system stabilizer,PSS)控制器励磁控制器相比较,具有更为优秀的动态品质,方法简单有效。