Adaptive Robust Control of Multi-Machine Power Systems with Control Time Delay

The adaptive H_∞ control problem of multi-machine power system in the case of disturbances and uncertain parameters is discussed,based on a Hamiltonian model.Considered the effect of time delay during control and transmission,a Hamilton model with control time delay is established.Lyapunov-Krasovskii function is selected,and a controller which makes the system asymptotically stable is got.The controller not only achieves the stability control for nonlinear systems with time delay,but also has the ability to suppress the external disturbances and adaptive ability to system parameter perturbation.The simulation results show the effect of the controller.

Applications of Localized Phase Compensation Method to Design a Stabilizer in a Multi-machine Power System

为了演示和验证稳定器设计的就地相位补偿法在多机电力系统中的应用,介绍在多机电力系统中,就地补偿设计稳定器的2个应用实例。第1个实例是在多机电力系统中就地补偿设计电力系统稳定器（power system stabilizer,PSS）,阻尼电力系统局部模振荡。第2个实例是就地补偿设计附加在静态同步补偿器（static synchronous compensator,STATCOM）上的稳定器,抑制多机电力系统中的区域模振荡,并给出在一个16机电力系统中的应用计算和仿真结果。

Stability control of multi-parameter adaptive wireless communication systems based on multi-Lyapunov function

With the occurrence of burst interference,bit error rate( BER) stability of the wireless communication system( WCS) always degrades significantly. To cope with it,a stability control algorithm is proposed,utilizing the stability theory of switched systems,which is specifically applicable for multi-parameter adaptive WCS with spectrum sensing ability,and it is capable of stabilizing BER within a reasonable range. Firstly,WCS is modeled as a switched system. Then,based on the multi-Lyapunov function,controlling rules are presented to enable the switched system to satisfy stable condition asymptotically. Finally,analysis and numerical simulation results demonstrate that the switched WCS with the proposed controlling rules is superior to conventional power-controlled WCS with or without state feedback control in terms of stability performance.

Coordinated nonlinear robust control of TCSC and excitation for multi-machine systems

An advanced nonlinear robust control scheme is proposed for multi-machine power systems equipped with thyristor-controlled series compensation (TCSC). First, a decentralized nonlinear robust control approach based on the feedback linearization and H∞ theory is introduced to eliminate the nonlinearities and interconnections of the studied system, and to attenuate the exogenous disturbances that enter die system. Then, a system model is built up, which has considered all the generators’ and TCSC’s dynamics, and the effects of uncertainties such as disturbances. Next, a decentralized nonlinear robust coordinated control law is developed based on this model. Simulation results on a six-machine power system show that the transient stability of the power system is obviously improved and die power transfer capacity of long distance transmission lines is enhanced regardless of fault locations and system operation points. In addition, the control law has engineering practicality since all the variables in the expression of he control strategy can be measured locally.

Machine Learning for Hybrid Line Stability Ranking Index in Polynomial Load Modeling under Contingency Conditions

In the conventional technique,in the evaluation of the severity index,clustering and loading suffer from more iteration leading to more com-putational delay.Hence this research article identifies,a novel progression for fast predicting the severity of the line and clustering by incorporating machine learning aspects.The polynomial load modelling or ZIP(constant impedances(Z),Constant Current(I)and Constant active power(P))is developed in the IEEE-14 and Indian 118 bus systems considered for analysis of power system security.The process of finding the severity of the line using a Hybrid Line Stability Ranking Index(HLSRI)is used for assisting the concepts of machine learning with J48 algorithm,infers the superior affected lines by adopting the IEEE standards in concern to be compensated in maintaining the power system stability.The simulation is performed in the WEKA environment and deals with the supervisor learning in order based on severity to ensure the safety of power system.The Unified Power Flow Controller(UPFC),facts devices for the purpose of compensating the losses by maintaining the voltage characteristics.The finite element analysis findings are compared with the existing procedures and numerical equations for authentications.

An Advanced FMRL Controller for FACTS Devices to Enhance Dynamic Performance of Power Systems

The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.

Design of a Fixed-Order Robust Controller to Damp Inter-Area Oscillations in Power Systems

This paper presents the design of a robust fixed-order H∞ controller to damp out the inter-area oscillations and to enhance the stability of the power system. The proposed H∞ approach is based on shaping the open-loop transfer function in the Nyquist diagram through minimizing the quadratic error between the actual and the desired open loop transfer functions in the frequency domain under linear constraints that guarantee robustness and stability. The proposed approach is robust with respect to multi-model uncertainty closed-loop sensitivity functions in the Nyquist diagram through the constraints on their infinity norm. The H∞ constraints are linearized with the help of a desired open-loop transfer function. The controller is designed using the convex optimization techniques in which the difference between the open-loop transfer function and the desired one is minimized. The two-area four-machine test system is selected to evaluate the performance of the designed controller under different load conditions as well as different levels of wind penetrations.

Dynamic stability enhancement of interconnected multi-source power systems using hierarchical ANFIS controller-TCSC based on multi-objective PSO

Suppression of the dynamic oscillations of tie-line power exchanges and frequency in the affected interconnected power systems due to loading-condition changes has been assigned as a prominent duty of automatic generation control(AGC). To alleviate the system oscillation resulting from such load changes, implementation of flexible AC transmission systems(FACTSs) can be considered as one of the practical and effective solutions. In this paper, a thyristor-controlled series compensator(TCSC), which is one series type of the FACTS family, is used to augment the overall dynamic performance of a multi-area multi-source interconnected power system. To this end, we have used a hierarchical adaptive neuro-fuzzy inference system controller-TCSC(HANFISC-TCSC) to abate the two important issues in multi-area interconnected power systems, i.e., low-frequency oscillations and tie-line power exchange deviations. For this purpose, a multi-objective optimization technique is inevitable. Multi-objective particle swarm optimization(MOPSO) has been chosen for this optimization problem, owing to its high performance in untangling non-linear objectives. The efficiency of the suggested HANFISC-TCSC has been precisely evaluated and compared with that of the conventional MOPSO-TCSC in two different multi-area interconnected power systems, i.e., two-area hydro-thermal-diesel and three-area hydro-thermal power systems. The simulation results obtained from both power systems have transparently certified the high performance of HANFISC-TCSC compared to the conventional MOPSO-TCSC.

基于改进类电磁机制算法的UPFC多目标优化配置

统一潮流控制器(UPFC)能在不改变线路拓扑结构的条件下有效地改善电力系统潮流,从而提高输电能力与电压稳定性。针对系统可用输电能力、电压偏差和L指标等目标,建立了UPFC的多目标优化配置模型,采用结合差分进化算法(DE)的改进差分类电磁机制算法(DEEM)对所建模型进行求解,通过对算法中粒子的带电量、合力计算方式进行改进,同时添加自适应因子,进一步平衡算法的全局搜索与局部搜索能力。配置后的结果表明UPFC对增强系统输电能力、电压质量及电压稳定性的性能均有提高,且改进算法寻优效率的提升也得到了验证。

阻抗模裕度指标在新能源多馈入系统静态电压稳定评估的适应性分析

集中送出的新能源场站大多位于电网末端,随着其有功出力的增加,易出现静态电压失稳。该文将传统的阻抗模指标的应用对象由负荷推广至新能源场站,丰富了该指标在静态电压稳定评估方面的适用性场景,包括含无功补偿的新能源系统、新能源集群馈入系统、以及新能源多机多馈入系统。具体地,首先,分析新能源单馈入系统的临界静态电压稳定条件,并据此给出用于评估新能源场站静态电压稳定性的阻抗模裕度指标及稳定判据;其次,通过将无功补偿设备并入系统阻抗,分析无功补偿对于指标的影响;再次,证明在新能源的集群馈入系统中,公共耦合点(point of common coupling,PCC)的电压失稳将发生在单个新能源场站之前,并据此确定PCC点作为指标的计算节点;之后,为考虑多机多馈入系统中不同新能源场站间的影响,在指标的计算过程中,保留待评估的关键新能源场站,将其他新能源场站等值为阻抗,并入节点阻抗矩阵中,实现方法在多机多馈入系统中的扩展应用。最后,基于PSD-BPA中建立的单机单馈入系统、多机多馈入系统、以及某省实际大电网算例验证指标的有效性。

基于动态虚拟电抗的虚拟同步机系统有功环电压动态补偿策略

为解决新型电力系统中的虚拟同步机(Virtual synchronous generator,VSG)在电网电压跌落时出现的功角暂态失稳和过电流问题,对采用VSG控制的并网换流器暂态控制策略进行了改进。为降低故障期间有功功率的参考值进而实现VSG的功角暂态稳定控制,根据VSG的功角特性、有功功率参考值与功角稳定性之间的关系,引入电压动态补偿,并利用相图曲线理论分析了控制策略参数选取对暂态稳定的影响。为限制故障发生瞬间和故障切除瞬间的冲击电流、保证故障期间VSG系统的暂态功角稳定、实现故障限流,提出了一种以指数形式变化的虚拟电抗模型,确定了虚拟电抗的投切参数。仿真实验结果验证了改进策略的有效性。

可解释机器学习在电网调控领域中的应用

数据驱动的机器学习是新一代人工智能的核心技术,尽管该技术已经在电网调控领域取得了显著成果,但是可解释性差,阻碍了其在对安全可靠性要求极高的电网调控领域的实际工程应用。因此,提升电网调控领域机器学习技术的可解释性对提高其实用性至关重要。首先,从电网调度运行人员的角度,分析了机器学习可解释性的定义、目标和意义;然后,提出考虑可解释性的机器学习在电网调控领域应用的流程,介绍了典型的机器学习解释技术及其在电力系统预测和稳定评估场景的应用,通过实际案例验证了该技术在电网调控领域应用的可行性;最后,对电网调控领域机器学习可解释技术面临的挑战进行了分析和展望。通过该研究,为解决电网调控领域机器学习应用的不可解释问题提供思路和参考,进一步促进机器学习技术在该领域的实际工程应用。

直流同时换相失败对受端暂态稳定影响因素及其协同恢复控制策略

多馈入直流受端系统中多直流同时发生换相失败无法避免,严重威胁系统的安全稳定运行。文章针对多馈入直流受端系统,从理论上研究了直流换相失败后恢复过程对受端系统暂态稳定性影响因素,并进一步提出了多直流协同恢复控制策略,以改善受端系统暂态稳定性。首先,建立了多馈入直流受端系统模型和直流潮流分析模型;其次,理论推导出了直流恢复过程中受端相对功角差关于直流功率的解析表达式,得到了直流恢复过程对受端系统暂态功角影响因素;然后,基于逆变侧直流控制器调节特性,得到了直流恢复过程对受端系统电压稳定影响因素,并基于上述影响因素提出了协同多直流恢复的控制策略。最后,在改进的Kundur's两区系统和IEEE-68节点机电-电磁混合仿真系统中进行测试,通过仿真验证了所提影响因素和协同恢复策略的正确性和有效性。

分布式电源对电力系统电压无功优化影响的研究

为研究分布式电源接入电力系统后的电压和无功优化问题,提出基于多代理系统(MAS)的一种电压无功优化协调控制新方法。以系统网损最小为目标,同时考虑电压稳定性,通过MAS构建以辅助问题原理进行分区分布式计算的电压无功优化协调控制模型,并通过分区并行求解获得全局最优解,得到最优网损和节点电压稳定数据;研究单个和多个分布式电源接入后,系统电压无功变化情况,通过分析得出分布式电源的最佳接入位置,即分布式电源从此点接入对系统电压无功的影响效果最好。最后,利用EPRI-36节点系统进行仿真计算,结果证明了所提方法的合理性与正确性。

电能路由器交流侧模块化变流器分布式一致性协同控制

针对电能路由器交流侧模块化变流器的协同控制,以及孤岛运行模式下提高系统频率稳定性的需求,提出基于虚拟同步机算法的电能路由器交流侧变流器本地控制策略,以及基于一致性算法的变流器分布式二次控制策略,实现了系统频率与电压的二次控制以及有功、无功功率按比例分配控制。所提分布式一致性协同控制策略结合了多智能体理论,只需建立稀疏通信网络完成相邻分布式发电单元的信息交互,系统灵活性高、冗余性好,可做到变流器模块即插即用,不受线路阻抗因素干扰,改进变流器的功率分配精度。最后,结合半实物实时仿真机和DSP控制板搭建了三电平变流器的半实物实验平台,实验结果验证了所提控制策略的有效性。

功率同步控制的构网型变流器多机交互分析与稳定控制研究综述

构网型变流器由于其具有同步电压源运行特性,在新能源直流送出、弱电网并网、微电网组网等场景中得到广泛关注。功率同步控制是构网型变流器的典型同步方式之一。然而,由于电力电子功率变换非线性和多环控制特性,功率同步控制作用下的构网型变流器多机交互作用及其引发的稳定问题不可忽视。该文对功率同步控制的构网型变流器多机交互分析和稳定控制两方面技术进行梳理和总结。首先,将构网型变流器多机系统稳定问题表征划分为有功功率振荡和暂态同步失稳,分别综述了所对应的模型和分析方法;其次,针对以上两类稳定问题,从机组控制和系统控制两个层面梳理了现有致稳控制技术;最后,总结了现有研究的主要结果和局限性,并对未来研究方向进行展望。

基于等值单机非线性模型的多换流器并联直流系统暂态稳定性分析及控制参数整定方法

针对“状态变量多、阶数高”给多换流器并联直流系统暂态稳定性分析带来的困难,提出计及多换流器动态交互的等值单机非线性模型,简化大扰动稳定性分析及控制参数设计复杂度。首先,对每台换流器下垂双环控制中的所有状态变量做等效变换,建立直流系统的等值单机非线性模型;其次,基于等值单机的Takagi-Sugeno(TS)模糊模型刻画出最大估计吸引域,分析系统控制参数设计不合理导致的“小扰动稳定、大扰动失稳”问题;然后,提出基于等值单机的直流系统控制参数整定方法,通过等值单机设计推导系统中每台换流器的控制参数,降低了直流系统控制参数设计的难度,最后,RT-BOX硬件在环实验平台验证等值单机非线性模型及理论分析的准确性。

基于二阶超前滞后环节的电压控制型微电网并网逆变器功率无差同步补偿策略

电压控制型策略可以作为微电网逆变器的并网运行控制策略,其与电网的同步过程为功率无差同步。然而,基本的PI调节器的功率无差同步策略响应速度慢,响应过程超调大,且无法通过PI参数的调配改善响应过程动态。为改善电压控制型逆变器功率无差同步的动态调节过程,提出了基于二阶实极点补偿器(real-polecompensator,RPC)和复极点补偿器(complex-pole compensator,CPC)的超前滞后环节补偿器,作为电压控制型逆变器的功率无差同步补偿策略。基于电压控制型逆变器功率输出模型,分析了2类补偿器的参数设计原则,详细给出了实极点补偿器和复极点补偿器的参数设计过程。通过仿真,验证了所提出的2类补偿器与常用的高通滤波器补偿器的补偿效果。结果表明,提出的2类补偿器在频域上可以有效地提高系统剪切频率,提高相位裕度至60°以上,而在时域上有效加速功率无差同步过程,并降低同步过程超调,使得功率无差同步过程更加平稳。

基于多源数据融合的电网计划安全稳定校核技术研究

安全稳定系统在预防电力系统极端灾害下遭受大面积连锁停电事故中发挥了重要作用,针对现有单一数据来源无法适应当前对外部环境变化的不足,基于气象数据提出了使用时空地理网格的电网多源数据融合方法,研究了基于多源数据融合对电网计划安全稳定校验系统的影响,深入分析了安全稳定校核系统对电网预警计划的提升。该系统以某省级电网进行验证,将广域信息的采集范围从电力系统内部扩大到自然环境,将预警目标从单故障风险延拓到灾害下群发性故障风险。结果表明融合多源数据能有效改善电网安全稳定校核的数据单一化局面,完成系统所涉及的多源数据统一和整合,提升计算数据的可靠性,增强了电网安全稳定运行的能力。