A fuzzy logic based power system stabilizer with learning ability

A fuzzy logic-based power system stabilizer (PSS) with learning ability is proposed in this paper. The proposed PSS employs a multilayer adaptive network. The network is trained directly from the input and the output of the generating unit. The algorithm combines the advantages of artificial neural networks (ANNs) and fuzzy logic control (FLC) schemes. Studies show that the proposed adaptive network-based fuzzy logic PSS (ANF PSS) can provide good damping of power systems over a wide range of operating conditions and improve the dynamic performance of the power system     

Design and analysis of an adaptive fuzzy power system stabilizer

Power system stabilizers (PSS) must be capable of providing appropriate stabilization signals over a broad range of operating conditions and disturbances. Traditional PSS rely on robust linear design methods. In an attempt to cover a wider range of operating conditions, expert or rule-based controllers have also been proposed. Fuzzy logic as a novel robust control design method has shown promising results. The emphasis in fuzzy control design centers around uncertainties in system parameters and operating conditions. Such an emphasis is of particular relevance as the difficulty of accurately modelling the connected generation is expected to increase under power industry deregulation. Fuzzy logic controllers are based on empirical control rules. In this paper, a systematic approach to fuzzy logic control design is proposed. Implementation for a specific machine requires specification of performance criteria. This performance criteria translates into three controller parameters which can be calculated off-line or computed in real-time in response to system changes. The robustness of the controller is emphasized. Small signal and transient analysis methods are discussed. This work is directed at developing robust stabilizer design and analysis methods appropriate when fuzzy logic is applied     

Design of augmented fuzzy logic power system stabilizers to enhancepower systems stability

This paper presents an augmented fuzzy logic power system stabilizer (PSS) for stability enhancement of multimachine power systems. In order to accomplish a satisfactory damping characteristic over a wide range of operating points, speed deviation (Δω) and acceleration (Δω) of a synchronous generator were taken as the input signals to the fuzzy controller. It is well known that these variables have significant effects on damping the generators' shaft mechanical oscillations. A modification of the terminal voltage feedback signal to the excitation system as a function of the accelerating power on the unit, is also used to enhance the stability of the system. The stabilizing signals are computed using the standard fuzzy membership function depending on these variables. The performance of the proposed augmented fuzzy controller is compared to an optimal controller and its effectiveness is demonstrated by a detailed digital computer simulation of a single machine infinite bus and a multimachine power systems     

Development of a 20 kW wind turbine simulator with similarities to a 3 MW wind turbine

As the use of wind power has steadily increased, the importance of a condition monitoring and fault diagnosis system is being emphasized to maximize the availability and reliability of wind turbines. To develop novel algorithms for fault detection and lifespan estimation, a wind turbine simulator is indispensible for verification of the proposed algorithms before introducing them into a health monitoring and integrity diagnosis system. In this paper, a new type of simulator is proposed to develop and verify advanced diagnosis algorithms. The simulator adopts a torque control method for a motor and inverter to realize variable speed-variable pitch control strategies. Unlike conventional motor–generator configurations, the simulator includes several kinds of components and a variety of sensors. Specifically, it has similarity to a 3 MW wind turbine, thereby being able to acquire a state of operation that closely resembles that of the actual 3 MW wind turbine operated at various wind conditions. This paper presents the design method for the simulator and its control logic. The experimental comparison between the behavior of the simulator and that of a wind turbine shows that the proposed control logic performs successfully and the dynamic behaviors of the simulator have similar trends as those of the wind turbine.     

THD reduction with reactive power compensation for fuzzy logic DVR based solar PV grid connected system

Dynamic voltage restorer (DVR) is used to protect sensitive loads from voltage disturbances of the distribution generation (DG) system. In this paper, a new control approach for the 200 kW solar photovoltaic grid connected system with perturb and observe maximum power point tracking (MPPT) technique is implemented. Power quality improvement with comparison is conducted during fault with proportional integral (PI) and artificial intelligence-based fuzzy logic controlled DVR. MPPT tracks the actual variable DC link voltage while deriving the maximum power from a photovoltaic array and maintains DC link voltage constant by changing modulation index of the converter. Simulation results during fault show that the fuzzy logic based DVR scheme demonstrates simultaneous exchange of active and reactive power with less total harmonic distortion (THD) present in voltage source converter (VSC) current and grid current with fast tracking of optimum operating point at unity power factor. Standards (IEEE-519/1547), stipulates that the current with THD greater than 5% cannot be injected into the grid by any distributed generation source. Simulation results and validations of MPPT technique and operation of fuzzy logic controlled DVR demonstrate the effectiveness of the proposed control schemes.     

基于三维时空特性的低压配电网拓扑识别方法

为解决泛在电力物联网的数据融合和数据互通问题,针对目前低压配电网拓扑连接信息更新不及时的拓扑错误问题,提出一种基于三维时空特性的低压配电网拓扑识别方法。该方法首先基于地理信息系统中配变台区和终端用户的经纬度地理信息,结合台区辐射范围限制,利用多空间尺度特性初步确定“变-户”关系;其次,基于辐射重叠区“变”、“户”节点智能电表的电气量序列,利用K-Means和PCA的多序列窗口截面特性实现拓扑校核;再其次,基于电压相关性,提出多时间相关性特性的拓扑变化监控方法。最后,通过仿真算例和现场案例验证了所提出方法的可行性。     

基于模糊层次分析法的混凝土结构耐久性等级评估模型及应用

为客观地评价影响混凝土结构耐久性的多要素间的耦合作用和影响程度,相对准确地评估水工建筑物的服役状态和耐久性等级,以甘肃省景泰川电力提灌灌区二期工程总干渠#5渡槽混凝土结构耐久性评估为例,将影响结构耐久性的要素分解为环境、材料、人为3个子系统,通过构建影响各子系统的多级指标体系,运用模糊层次分析法(FAHP)建立多层次多指标的混凝土建筑物耐久性综合评估模型;定义了水工建筑物服役的Ⅰ～Ⅴ级共5个耐久性状态,基于模糊数学理论将指标定量化,通过可拓区间判断矩阵计算各层指标权重,结合模糊综合评价法进行逐级评估,从而实现了以综合评估值来定量描述混凝土建筑物的耐久性水平。评估结果表明,其综合评估值为65.76,根据等级划分确定耐久性等级为Ⅱ级,准确反映了渡槽的实际服役状态。可见该模型可较好地表征水工混凝土结构耐久性等级,具有一定的实际应用价值。     

Implementation and performance evaluation of advance metering infrastructure for Borneo-Wide Power Grid

In this paper, a supervisory computer network for Borneo-Wide Power Grid system have been proposed and implemented, which includes a renewable power generation and advanced metering infrastructure. An Internet-based communication network running on multiprotocol label switching (MPLS) has been implemented for a smart power grid, with the addition of the renewable energy monitoring system. The centralized supervisory control and data acquisition systems (SCADA) are replaced by a wide area monitoring system(WAMS) comprising of a phasor measurement unit (PMU). The implemented communication network used advanced metering infrastructure that operates on worldwide interoperability for microwave access (WiMAX), wireless fidelity (Wi-Fi) and low power Wi-Fi, which are proposed for the distribution systems of Sarawak Energy. The proposed wide area network (WAN) is simulated using OPNET Modeler and the results are compared with the existing WAN used by Sarawak Energy.     

抽水蓄能机组调速系统健康状态评估

采用层次分析法及模糊综合评判原理评估了响水涧抽水蓄能电站调速系统的健康状态。首先根据行业技术规程和电站试验及运行数据,建立了调速系统层次分析模型,基于油系统性能状态、工况性能状态、历史性能状态3大类及50余项运行指标对调速系统健康状态影响进行权重分析;其次建立了评语集,采用加权平均型模糊算子与合适的隶属度函数对各项指标实际运行数据进行了模糊评判;最后对响水涧机组调速系统性能及状态进行综合评估,确定了该系统的总体健康状态。     

Integrated fuzzy logic generator controller for stabilityenhancement

An integrated fuzzy logic controller is proposed in this paper for the generator excitation and speed governing control. The proposed controller has three control loops: the first one is the voltage control loop which has the function of automatic voltage regulator (AVR), the second one is the damping control loop which has the function of power system stabilizer (PSS), and the last one is the speed governing control loop which has the function of governor (GOV). A simple fuzzy logic control scheme is applied to all these three loops. The control scheme is simple enough so as not to require heavy computation for the controller, therefore, its real time application is feasible. The effectiveness is demonstrated through nonlinear simulations using a one machine infinite bus system. Comparison studies are also performed to show the advantages of the proposed controller with conventional excitation and speed governing control systems     

Risk of Winding Insulation Breakdown in Large AC Motors Caused by Steep Switching Surges Part 1 Computed Switching Surges

The research reported here and sponsored by the Electric Power Research Institute was initiated to demonstrate the applicability and use of the finite element method for probabilistic assessment of the risk of turn insulation breakdown in large AC motors. Computer models were developed for computation of the electromagnetic transients in the AC motor windings. Mathematical models were developed to compute the risk of turn insulation breakdown. The application of the proposed approach was demonstrated for a typical installation. This allowed evaluation of the advantages of using the finite element method in terms of accuracy, efficiency, capability and limitations. It also identified the need for further research to facilitate the use of this risk assessment method by utility engineers.     

Tuning of power system stabilizers using an artificial neuralnetwork

A new approach using an artificial neural network is proposed to adapt power system stabilizer (PSS) parameters in real time. A pair of online measurements i.e., generator real-power output and power factor which are representative of the generator's operating condition, are chosen as the input signals to the neural net. The outputs of the neural net are the desired PSS parameters. The neural net, once trained by a set of input-output patterns in the training set, can yield proper PSS parameters under any generator loading condition. Digital simulations of a synchronous machine subject to a major disturbance of a three-phase fault under different operating conditions are performed to demonstrate the effectiveness of the proposed neural network     

基于信息技术的变电站仿真培训系统研究

介绍了一种基于电力企业信息技术的变电站培训仿真系统。基于变电站实际操作的内容与规程,利用先进的计算机信息技术与电力系统仿真技术,设计了以物理器件模拟仿真作为操作平台,以计算机数字仿真模拟提供后台数据支持,并以信息技术使其结合运行的新型实用化变电站仿真培训系统。实际应用结果表明,系统能较好地满足对电力系统运行人员培训的各项要求。     

基于分形模糊集对分析方法的洪水分类

针对目前洪水分类方法复杂、难以实施和在分类中难以客观确定分类指标权重的问题,基于集对分析原理提出了分形模糊集对分析方法,以反映指标复杂程度的分维来刻画指标权重,同时考虑分类标准边界的模糊性,并将该方法应用于黄河支流秃尾河流域的洪水分类中。与其他分类方法的比较结果表明,分形模糊集对分析方法客观、精确、有效,分类结果符合实际情况。     

Enhancement of micro-grid performance during islanding mode using storage batteries and new fuzzy logic pitch angle controller

Power system deregulation, shortage of transmission capacities and needing to reduce green house gas have led to increase interesting in distributed generations (DGs) especially renewable sources. This study developed a complete model able to analysis and simulates in details the transient dynamic performance of the Micro-Grid (MG) during and subsequent islanding process. Wind speed fluctuations cause high fluctuations in output power of wind turbine which lead to fluctuations of frequency and voltages of the MG during the islanding mode. In this paper a new fuzzy logic pitch angle controller is proposed to smooth the output power of wind turbine to reduce MG frequency and voltage fluctuations during the islanding mode. The proposed fuzzy logic pitch controller is compared with the conventional PI pitch angle controller which usually used for wind turbine power control. Results proved the effectiveness of the proposed fuzzy controller in improvement of the MG performance. Also, this paper proposed using storage batteries technique to reduce the frequency deviation and fluctuations originated from wind power solar power fluctuations. Results indicate that the storage batteries technique is superior than fuzzy logic pitch controller in reducing frequency deviation, but with more expensive than the fuzzy controller. All models and controllers are built using Matlab® Simulink® environment.     

提升西北电网水（火）电机组一次调频性能的措施

为了适应西北电网大规模外送的要求,提高西北电网频率稳定性,西北电力调度通信中心对于西北电网内水(火)电机组的一次调频性能提出了整改措施,该措施将机组一次调频贡献电量、响应行为等指标作为考评发电企业的考评标准,确定了水(火)电机组一次调频性能考评办法、计量计算方法、信息披露方法。实践表明,该整改措施提高了西北电力系统在直流闭锁、大容量机组跳闸时系统频率的稳定性。     

Electric power system reliability criteria determination in adeveloping country-an investigation in Nepal

This paper examines the problems associated with using power system reliability cost/worth techniques in a developing country, and presents methods to develop planning criteria incorporating explicit recognition of reliability worth. The developed methods are illustrated by application to the Nepal Integrated Electric Power System     

基于模糊隶属度的电力设备资产全寿命周期成本模型及评价体系研究

电网企业将LCC理论应用作为提高设备资产效率和质量的有效手段,亟需解决LCC应用中的模型计算和评价体系问题.本文通过构建电网企业资产全寿命周期管理机制,建立了电力设备的LCC的计算模型和方法,采用基于模糊数学中的模糊隶属度方法,改进了技改和大修项目分摊到多个设备资产分摊方法,提出了电力设备的LCC评价模型和评价体系,并...     

Intelligent power management in a vehicular system with multiple power sources

This paper presents an optimal online power management strategy applied to a vehicular power system that contains multiple power sources and deals with largely fluctuated load requests. The optimal online power management strategy is developed using machine learning and fuzzy logic. A machine learning algorithm has been developed to learn the knowledge about minimizing power loss in a Multiple Power Sources and Loads (M_PS&LD) system. The algorithm exploits the fact that different power sources used to deliver a load request have different power losses under different vehicle states. The machine learning algorithm is developed to train an intelligent power controller, an online fuzzy power controller, FPC_MPS, that has the capability of finding combinations of power sources that minimize power losses while satisfying a given set of system and component constraints during a drive cycle. The FPC_MPS was implemented in two simulated systems, a power system of four power sources, and a vehicle system of three power sources. Experimental results show that the proposed machine learning approach combined with fuzzy control is a promising technology for intelligent vehicle power management in a M_PS&LD power system.     

Impact of interconnection photovoltaic/wind system with utility on their reliability using a fuzzy scheme

Reliability analysis has been considered as an important step in any system design process. A reliable electrical power system means a system which has sufficient power to feed the load demand during a certain period or, in other words, has small Loss of Load Probability (LOLP). LOLP is defined as an expected fraction of load not met by its power needs from electrical power system during its lifetime. Photovoltaic (PV)/Wind Energy System (WES) Hybrid Electric Power System (PV/WES HEPS) differs considerably from the Utility Grid (UG) in its performance and operating characteristics. With the interconnection of PV/WES as a HEPS into the UG, the fluctuating nature of the energy produced by these systems has a different effect on the overall system reliability than that of the fluctuating nature of energy produced by UG. Therefore, this paper presents a complete study, from reliability point of view, to determine the impact of interconnecting PV/WES HEPS into UG. Four different configurations of PV/WES/UG have been investigated and a comparative study between these four different configurations has been carried out. The overall system is divided into three subsystems, containing the UG, PV and WES. The generation capacity outage table has been built for each configuration of these subsystems. These capacity outage tables of UG, PV/UG, WES/UG and PV/WES/UG are calculated and updated to incorporate their fluctuating energy production. This paper also presents a fuzzy logic technique to calculate and assess the reliability index for each HEPS configuration under study.