Consensus-based secondary frequency control under denial-of-service attacks of distributed generations for microgrids

In this paper, Denial-of-Service (DoS) attacks on a microgrid (MG), especially on service-provider-edge routers in the MG, are considered and analysed. To increase the tolerance of the MG for DoS attacks with decreased computing time, we present consensus-based secondary frequency controllers with dynamic P-f droop controllers. Then, with the consideration of the impact on these controllers caused by DoS attacks, a state-space model of the MG is established based on which the stability analysis is derived. Finally, the effectiveness of the method is verified by simulation and experimental results.     

New modeling approach of secondary control layer for autonomous single-phase microgrids

In a microgrid (MG) topology, the secondary control is introduced to compensate for the voltage amplitude and frequency deviations, mainly caused by the inherent characteristics of the droop control strategy. This paper proposes an accurate approach to derive small signal models of the frequency and amplitude voltage at the point of common coupling (PCC) of a single-phase MG by analyzing the dynamics of the second-order generalized integrator-based frequency-locked loop (SOGI-FLL). The frequency estimate model is then introduced in the frequency restoration control loop, while the derived model of the amplitude estimate is introduced for the voltage restoration loop. Based on the obtained models, the MG stability analysis and proposed controllers’ parameters tuning are carried out. Also, this study includes the modeling and design of the synchronization control loop that enables a seamless transition from island mode to grid-connected mode operation. Simulation and practical experiments of a hierarchical control scheme, including traditional droop control and the proposed secondary control for two single-phase parallel inverters, are implemented to confirm the effectiveness and the robustness of the proposal under different operating conditions. The obtained results validate the proposed modeling approach to provide the expected transient response and disturbance rejection in the MG.     

Consensus-based economic hierarchical control strategy for islanded MG considering communication path reconstruction

In the islanded microgrid (MG), to improve the control effect of the output voltages of DERs and keep the economical operation of MG, a consensus-based economic hierarchical control strategy is proposed in this paper. The corresponding control structure is divided into physical and cyber layers, where the cyber layer is mainly composed by communicators. In these two layers, there are two main designs: the consensus-based primary control (CBPC) method and the secondary control (CBSC) method. In CBPC: Firstly, the undirected communication path among communicators is designed by path planning. Then, based on the constructed path, an economic P–U droop control method considering with line loss and flexible load is realized by using consensus control. In CBSC: Firstly, a cyber-physical vulnerability assessment method is designed. Based on this method, the DER with the lowest vulnerability is selected to be connected with the “virtual leader”. And when the data transmission behavior of the undirected communication path is selected, the undirected network can be transferred as a directed network. Thus, it can make the virtual leader-following consensus control (VLFCC) and the secondary control on voltage accomplished. Finally, the simulation results show the effectiveness of the proposed strategy.     

Global stability analysis for coupled control systems and its application: Practical aspects and novel control

In this paper, the global stability of coupled control systems (CCSs) is discussed. Assembling the energy of each vertex system with the help of graph theory, a systematic method for constructing a global Lyapunov function of CCSs is proposed. Then, two kinds of stability criteria by Lyapunov-type theorem and coefficient-type theorem with the condition of the system topology are derived. Subsequently, the theoretical results are applied to the microgrid and the criterion of global asymptotical stability of the microgrid is developed. Meanwhile, based on the actual demand of the microgrid, the secondary frequency distributed consistency sliding mode control of the microgrid is proposed using the consensus algorithm. In the presence of a time-varying load, the control can not only quickly stabilize the frequency at the equilibrium point but also dynamically achieve active power sharing. Finally, the simulation of an islanded microgrid is conducted to test the validity and feasibility of our results.     

智能微网在分布式能源接入中的作用与挑战

分布式可再生能源发电由于靠近用户侧直接供能且便于实现多能互补而受到越来越多的重视。而将分布式能源发电以智能微网形式接入到电网中并网运行,与电网互为支撑,是发挥分布式能源效能的最有效方式。文章介绍了智能微网的概念,阐述了智能微网在分布式能源接入中的作用,分析了智能微网的研究现状与发展趋势,提出了基于分布式能源接入的智能微网关键技术及挑战,绘制了智能微网的技术成熟度蛛网图和产业化发展路线图。     

Suppression of DC-link voltage unbalance in three-level neutral-point clamped converters

Two different control approaches for suppressing DC-link voltage unbalance in Three-Level Neutral-Point Clamped Converters (NPCs) are presented in this paper. They both guarantee DC-link voltage equalization over any NPC operating conditions, i.e. when the NPC feeds or is supplied by the main AC grid at different active and/or reactive power rates. The proposed control approaches consist of either a hysteresis or a proportional regulator, each of which synthesizes the most suitable control action based on the actual DC-link voltage unbalance. Particularly, two different PWM techniques have been developed in order to achieve DC-link voltage equalization successfully, preserving NPC voltage and current waveforms at the same time. The performances achievable by means of both the proposed control approaches have been compared to each other through an extensive simulation study in order to highlight their most important advantages and drawbacks, as well as their effectiveness over any operating conditions. Particularly, both control approaches are validated in the Matlab-Simulink environment referring to DC-link voltage equalization of an NPC that represents the point of common coupling between a DC microgrid and the main AC grid.     

Event-triggered asynchronous periodic distributed secondary control of microgrids under DoS attacks

A novel distributed secondary voltage and frequency control strategy is proposed with the Zeno-free event-triggered scheme for an island alternating current (AC) microgrid under Denial-of-Service (DoS) attacks. A DoS attack compensation mechanism and an event-triggered mechanism on the basis of the checking scheme are developed. Then, a secure event-checked based event-triggered secondary control method is explored to guarantee the tracking performance of the microgrid under DoS attacks. Further, some linear matrix inequalities (LMIs)-based sufficient conditions are derived to design the controller. What’s more, the proposed asynchronous periodic triggering method can efficiently save communication resources and further reduce the update number of the controller. Finally, the efficiency of this work is verified by an islanded AC microgrid with comparisons.     

分布式储能的发展现状与趋势

储能技术是解决可再生能源间歇性和不稳定性、提高常规电力系统和区域能源系统效率、安全性和经济性的迫切需要,是发展"安全、高效、低碳"的能源技术、占领能源技术制高点的"战略必争领域",储能在分布式可再生能源应用与智能微网领域具有重大的战略需求、重要的研究价值和巨大的发展潜力。文章分析了分布式储能技术现状、技术创新及其发展对相关产业的带动,并结合分布式储能的技术与产业特点给出了发展储能技术的政策建议。     

重大科技工程体系管理能力评估方法

体系和能力建设是大型工程项目组织与管理的关键。针对当前重大科技工程面临的预先研究与型号研制并行推进、参与主体价值诉求多元化等挑战,本文引入体系管理理论,提出一种体系管理能力评估方法,力图解决重大科技工程组织管理的短板弱项识别问题。主要涵盖以下内容：一是针对体系开放性要求,构建涵盖组织管理、项目控制、系统工程管理三维度的体系管理框架;二是结合组织级项目管理成熟度模型,构建包括管理体制潜能、运行机制潜能、系统工程管理潜能、项目控制能力四方面评估指标;三是基于综合集成思想,构建以“两次定性集成、一次定量集成”为特征的集成评估方法。最后,选取涵盖科学规律探索、关键技术集成、样机实现等完整研发链条的典型案例进行应用性研究,表明方法可行。     

变频调速系统的谐波分析和抑制措施

现在的工业传动领域,大量的变频调速系统取代了传统的传动系统,给电力电网带来了大量的谐波,造成了电力系统污染,存在极大危害。文章阐述了电力系统谐波的基本定义、产生原理、危害和常用抑制措施,并在此基础上对不同结构的变频调速系统的谐波情况进行了定性分析,介绍了适合变频调速系统的几种谐波抑制技术。     

An improved passivity-based control strategy for providing an accurate coordination in a AC/DC hybrid microgrid

This paper proposes an improved passivity-based control (PBC) technique to provide accurate coordination between AC and DC sides of a grid-tied AC/DC hybrid microgrid. The proposed PBC is based on the passive properties of the system and the energy exchange between the subsystems. To this end, three mathematical formulations for the converters are driven in the first step. Then, using the formulations, the impedance injection is applied to shape the error dynamics of all DC/DC and DC/AC converters. The DC link-connected DC/AC converter is used to help the AC side for maintenance of the power quality factors such as, the grid frequency and voltage magnitude in the presence of any unbalanced power load sharing. The first contribution of the paper is the part of impedance injection to the DC/AC converter, which aims to provide more decoupling and faster convergence rate for both the steady states and the dynamical conditions. Secondly, a Lyapunov function is defined for converters’ error dynamics that provide more accurate statement of the proposed damping injections. Besides, as an attractive control feature, decoupling properties of the suggested method are investigated. Then, through achieving several curves, various operating conditions of DC/DC and DC/AC converters under varying the system errors and proposed damping injections are evaluated as well. For the purpose of validation, the system under study is simulated in the MATLAB/SIMULINK software package against a variety of system errors and converters’ operational conditions.     

能源革命中的电化学储能技术

储能技术在可再生能源并网及微电网、电网调峰提效、区域供能、电动汽车等应用中发挥着关键作用,是保障能源安全,落实节能减排,推动全社会绿色低碳发展的重大战略需求,对切实推进能源革命具有不可替代的作用。文章重点介绍具有重要市场前景的电化学储能技术,包括液流电池、锂离子电池、铅炭电池、钠基电池技术,并在分析电化学储能技术发展现状的基础上,阐述中国相关领域未来的发展战略。     

电力系统稳定器在某300MW火力发电机组上的应用及参数优化试验研究

随着全国联网工程的不断实施和快速励磁系统的广泛采用,电力系统的正阻尼变弱,致使电网中弱阻尼震荡时有发生。电力系统稳定器PSS对低频弱阻尼振荡有很好的抑制作用,在电力系统中得到了广泛的应用。文章主要介绍了南瑞继保公司的PCS9410A型电力系统稳定器在300MW火力发电机组上的应用,总结了现场PSS试验方法及流程。并根据现场试验数据,对现场PSS模型的相关参数进行了整定,同时验证了电力系统稳定器对电网弱阻尼振荡起到了良好的抑制作用。     

高能物理实验的数据密集型计算

高能物理一直是信息技术发展的主要推动者之一。现代高能物理产生的海量数据对计算机技术提出巨大的挑战。为了应对这些挑战,国内外高能物理领域的科学家根据数据处理的特点建立新的计算平台用于传输、储存及分析处理PB量级的数据。文章介绍了现代高能物理实验及数据处理的发展,并描述了高能物理的计算模型以及以网格技术为代表的数据密集型计算平台;详细介绍了数据密集型网格平台在LHC实验、BESIII实验中的应用以及中国的数据密集型网格平台。并对云计算等新技术在高能物理领域的应用进行了展望。     

Distributed fixed-Time secondary control for islanded microgrids: Tackling abnormal data

This paper deals with the distributed secondary control problem for multiple distributed generators in an islanded microgrid. A distributed fixed-time secondary controller is designed for each generator using only its neighbors’ information, where saturation functions are introduced to the designed controllers to constrain the adverse influence of abnormal data from neighbors. Several indicator variables are introduced to reformulate the saturation function to reduce conservatism. The objective of this paper is to realize the recovery of the frequency and voltage as well as the active power-sharing within a fixed time. The fixed-time convergence of the proposed distributed control algorithm is analyzed through rigorous analysis. Also, the upper bound of the settling time is derived, which does not depend on the system’s initial state. Finally, a simulation example is utilized to verify the effectiveness of the proposed distributed control scheme by using the MATLAB/SimPowerSystems toolbox.     

Presynaptic Membrane Receptor in Human Brain

Myasthenia gravis (MG) is an autoimmune disease that results from antibody mediated damage of Acetylcholine receptor (AChR) at the neuromuscular junction. The autoimmune character of MG and pathogenic role of AChR antibodies have been established by several workers i.e., the demonstration of anti-AChR antibodies in about 90 % of MG patients. It has been demonstrated that patients with MG also have antibodies against a second protein named presynaptic membrane receptor (PsmR), which is identified by utilizing β-Bgtx, a ligand which binds to PsmR. Using β-Bgtx Sepharose 4B affinity matrix, the PsmR was purified from different regions of human cadaver brain by affinity chromatography. Purified receptor was characterized both by biochemical and immunological procedures. PsmR purified from different regions of the brain shows a specific activity of 0.37 ± 0.01, 0.39 ± 0.02 and 0.43 ± 0.005 nM/ μg of protein in Parietal lobe, Occipital lobe and Frontal lobe respectively. The affinity purified PsmR from the brain of 87 and 68 kd (parietal lobe, occipital lobe and frontal lobe) shows immunoreactivity with myasthenic sera. These findings suggest that PsmR from brain is another antigen against which autoantibodies are developed in Myasthenia gravis patients. Upon treatment with various enzymes we concluded that PsmR from brain is a glycoprotein in which the immunoreactivity resides in the carbohydrate as well as the peptide epitopes. In conclusion the PsmR is another antigen against which autoantibodies are formed in different regions of brain. These can be used as a diagnostic tool for detecting antibodies in the sera or cerebrospinal fluid of MG patients.     

浅谈电网调度自动化技术在县级供电企业的应用

本文在简要介绍电网调度自动化系统的基础上,结合桐乡供电局的实际情况,提出县级电网调度自动化系统的发展方向:应从原来简单的SCADA系统向集数据采集与监视(SCADA)、实时网络拓扑分析、状态估计、调度员仿真系统等各种功能于一体的新一代调度自动化系统向能量管理系统(EMS)方向发展,从而适应不断增长的需求。     

Hierarchical control of hybrid direct current microgrid with variable structure based sliding mode control and fuzzy energy management system

The recent transition in power generation and consumption is based on the integration of renewable energy sources using DC microgrids. To facilitate this integration, a multi-source DC microgrid structure with wind, photovoltaics, fuel cell and hybrid energy storage system including battery and supercapacitor is presented in this paper. These sources are linked to a DC-bus via DC-DC converters. A hierarchical control strategy with a device and a system-level control for coordinated control between energy sources and their storage devices is proposed. In the device-level control, a variable structure based sliding mode control is applied to regulate the DC bus voltage and to ensure global asymptotic stability. Whereas, the system-level control compensates for the supply and demand mismatches by using a rule-based fuzzy system. To verify the effectiveness of the proposed scheme and the superiority of one controller over another, the proposed controllers are simulated and compared in the MATLAB/Simulink environment under varying load and weather data conditions. Results show that super twisting sliding mode control had negligible chattering as well as better convergence as compared to controllers. Furthermore, the efficiency of the developed scheme is validated by controller hardware in loop experiments.     

MG2×70／325-BWD型采煤机电控系统组成及工作原理

通过以实际设计项目为背景,主要介绍MG2×70／325-BWD型采煤机电控系统组成及工作原理,重点阐述主要技术参数、电控箱体结构、变频调速系统和传感器保护系统。     

Adaptive fuzzy sliding mode command-filtered backstepping control for islanded PV microgrid with energy storage system

This study focuses on the control of islanded photovoltaic (PV) microgrid and design of a controller for PV system. Because the system operates in islanded mode, the reference voltage and frequency of AC bus are provided by the energy storage system. We mainly designed the controller for PV system in this study, and the control objective is to control the DC bus voltage and output current of PV system. First, a mathematical model of the PV system was set up. In the design of PV system controller, command-filtered backstepping control method was used to construct the virtual controller, and the final controller was designed by using sliding mode control. Considering the uncertainty of circuit parameters in the mathematical model and the unmodeled part of PV system, we have integrated adaptive control in the controller to achieve the on-line identification of component parameters of PV system. Moreover, fuzzy control was used to approximate the unmodeled part of the system. In addition, the projection operator guarantees the boundedness of adaptive estimation. Finally, the control effect of designed controller was verified by MATLAB/Simulink software. By comparing with the control results of proportion-integral (PI) and other controllers, the advanced design of controller was verified.