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system Strength Assessment Based on Multi-task Learning

CSEE Journal of power and Energy systems 2024年第1期10卷 41-50页

作者： Baoluo Li Shiyun Xu Huadong Sun Zonghan Li Lin Yu Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong UniversityJinan 250014China China Electric Power Research Institute Beijing 100192China

Increase in permeability of renewable energy sources(RESs)leads to the prominent problem of voltage stability in power system,so it is urgent to have a system strength evaluation method with both accuracy and practicability to control its access scale within a reasonable ***,a hybrid intelligence enhancement method is proposed by combining the advantages of mechanism method and data driven ***,calculation of critical short circuit ratio(CSCR)is set as the direction of intelligent enhancement by taking the multiple renewable energy station short circuit ratio as the quantitative ***,the construction process of CSCR dataset is proposed,and a batch simulation program of samples is developed accordingly,which provides a data basis for subsequent ***,a multi-task learning model based on progressive layered extraction is used to simultaneously predict CSCR of each RESs connection point,which significantly reduces evaluation error caused by weak *** performance and anti-noise performance of the proposed method are verified on the CEPRI-FS-102 bus system,which provides strong technical support for real-time monitoring of system strength.

关键词： Critical short circuit ratio hybrid intelligence enhancement multi-task learning system strength

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Maximum frequency deviation assessment with clustering based on metric learning

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INTERNATIONAL JOURNAL OF ELECTRICAL power & ENERGY systemS 2020年 120卷 105980-000页

作者： Li, Huarui Li, Changgang Liu, Yutian Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control MOE Jinan Peoples R China

Loss of massive generation caused by HVDC blocking or tripping of large power plants is a severe threat to the frequency security of receiving-end grids, especially those with a high penetration level of renewable generation. Due to the uncertainty of renewable generation, a large number of scenarios need to be checked for hour-ahead frequency security assessment, which is time-consuming if they are assessed with full time-domain simulation. To improve assessment efficiency, a maximum frequency deviation assessment method with clustering based on Metric Learning (ML) is proposed in this paper. The distance measure of samples is firstly adjusted by ML with Kernel Regression to make samples with similar frequency dynamics close to each other. The training process of ML is optimized with Mini-Batch Gradient Descent (MBGD) method. Then fuzzy k-means clustering is used to group the samples into multi clusters by maximizing the membership degree of each training sample with the distance measure adjusted by ML. Finally, corresponding to each cluster, a Support Vector Regression (SVR) model is established to build the relationship between maximum frequency deviation and steady-state power flow features, and Core Vector Regression (CVR) is used to accelerate the training process of SVR. The membership degree of the new scenario to assess with respect to each cluster is calculated according to the distance measure learned by ML to classify it into a specific cluster in the on-line assessment process. The corresponding SVR model is used to assess the maximum frequency deviation of the new scenario. The New England 39-bus system and a simplified provincial power system of China are adopted to verify the validity of the proposed assessment method.

关键词： Frequency security assessment Clustering Metric learning Machine learning power systems

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Efficient Eigen-Analysis for Large Delayed Cyber-Physical power system Using Explicit Infinitesimal Generator Discretization

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IEEE TRANSACTIONS ON power systemS 2016年第3期31卷 2361-2370页

作者： Ye, Hua Liu, Yutian Zhang, Peng Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control Minist Educ Jinan 250061 Peoples R China Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control Minist Educ Jinan 250061 Peoples R China

Time delays significantly compromise the performance of wide-area measurement and control system and thus may jeopardize the stability of cyber-physical power systems (CPPS). A delayed CPPS (DCPPS) has a transcendental characteristic equation, leading to an infinite number of eigenvalues basically unsolvable by traditional eigen-analysis methods. In this paper, an explicit infinitesimal generator discretization (EIGD) approach is presented to tackle the traditionally intractable problem. First, the delayed differential equation of DCPPS is transformed to an ordinary differential equation by using an operator called infinitesimal generator. The operator is then optimally discretized, resulting in a highly structured, sparse and explicit approximant matrix. By exploiting the sparsity of the matrix and that of system matrices, the rightmost eigenvalues of the original DCPPS can be accurately computed. The contributions of the EIGD approach lie in the following: 1) it forms a theoretical foundation for accurately obtaining the critical eigenvalues of a CPPS with multiple delays;2) it constructs a highly structured approximant matrix that enables efficient eigen-analysis of a large DCPPS by making full use of sparsity techniques;and 3) it integrates the shift-invert transformation, Arnoldi algorithm, Newton correction and eigen-sensitivity to form a computational framework for the analysis of large DCPPS. The accuracy, efficiency and scalability of EIGD have been extensively studied and thoroughly validated on the two-area four-machine test system and a practical large transmission grid.

关键词： Cyber-physical system eigen-analysis infinitesimal generator discretization time delay wide-area measurement system

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Multi-stage Dynamic Post-disaster Recovery Strategy for Distribution Networks Considering Integrated Energy and Transportation Networks

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CSEE Journal of power and Energy systems 2021年第2期7卷 408-420页

作者： Xinyi Jiang Jian Chen Ming Chen Zhen Wei Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong UniversityJinan 250061China State Grid Qingdao Power Supply Company Qingdao 266002China

To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transportation network(TN).First,the emergency response quickly increases the output of gas turbines(GTs)in the natural gas network(NGN),and responsively reconfigures the DN in microgrids,to maximize the amount of loads to be *** single-commodity flow model is adopted to construct spanning tree ***,in the second stage of energy storage recovery,mobile energy storage systems(MESSs)are deployed to cover the shortages of power demands,i.e.,to further restore the loads after evaluating the load recovery *** Floyd algorithm based dynamic traffic assignment(DTA)is selected to obtain the optimal path of the *** the third stage,the outputs of various post-disaster recovery measures are adjusted to achieve an economically optimized *** studies demonstrate the effectiveness of the proposed dynamic post-disaster recovery strategy.

关键词： Dynamic post-disaster recovery dynamic transportation network integrated energy system resilience distribution

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Analysis of multi-scale chaotic characteristics of wind power based on Hilbert-Huang transform and Hurst analysis

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APPLIED ENERGY 2015年 159卷 51-61页

作者： Liang, Zhengtang Liang, Jun Zhang, Li Wang, Chengfu Yun, Zhihao Zhang, Xu Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control Jinan 250061 Shandong Peoples R China

The causes of uncertainty in wind farm power generation are not yet fully understood. A method for the scale division of wind power based on the Hilbert-Huang transform (HHT) and Hurst analysis is proposed in this paper, which allows the various multi-scale chaotic characteristics of wind power to be investigated to reveal further information about the dynamic behavior of wind power. First, the time-frequency characteristics of wind power are analyzed using the HHT, and then Hurst analysis is applied to analyze the stochastic/persistent characteristics of the different time-frequency components. Second, based on their fractal structures, the components are superposed and reconstructed into three series, which are defined as the Micro-, Meso- and Macro-scale subsequences. Finally, indices related to the statistical and behavioral characteristics of the subsequences are calculated and used to analyze their nonlinear dynamic behavior. The data collected from a wind farm of Hebei Province, China, are selected for case studies. The simulation results reveal that (1) although the time-frequency components can be decomposed, the different fractal structures of the signal are also derived from the original series;(2) the three scale subsequences all present chaotic characteristics and each of them exhibits its own unique properties. The Micro-scale subsequence shows strong randomness and contributes the least to the overall fluctuations;the Macro-scale subsequence is the steadiest and exhibits the most significant tendency;the Meso-scale subsequence which possesses the greatest variance contribution rate and the maximum largest Lyapunov exponent, is the dominant factor driving the fluctuation and dynamic behavior of wind power;(3) the short-term predictions of these three subsequences based on extreme learning machine (ELM) and least-squares support vector machine (LSSVM) models have validated the above analysis results, which show that the number of steps of look-ahead pre

关键词： Wind power Multi-scale Hilbert-Huang transform Hurst analysis Chaos analysis Short-term forecasting

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Time-domain continuous power flow calculation of electricity-gas integrated energy system considering the dynamic process of gas network

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ENERGY REPORTS 2022年 8卷 597-605页

作者： Cui, Zhaoliang Chen, Jian Liu, Chunyang Zhao, Haoran Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control Jinan 250061 Shandong Peoples R China

The power flow calculation is a significant basis for the optimized operation of integrated energy systems. For two-way coupled electricity-gas integrated energy systems, the dynamic characteristics of the slow time scale of the gas subsystem make the steady-state energy flow calculation unable to accurately obtain its real-time operating status. In this paper, for the electricity-gas integrated energy system, propose a time-domain continuous power flow calculation method considering the dynamic process of the gas subsystem, which can obtain continuous change of the state variables. The Taylor series expansion method is applied to the power subsystem, the unified energy path model and matching calculation method is used in the natural gas subsystem. The solution is realized by alternating the input and output variables of the coupling element. At the same time, the input of the power subsystem derivative information and the natural gas subsystems frequency domain information makes this method obtain continuous solutions in the time domain, which can meet the time scale requirements in different scenarios. Finally, a calculation example is carried out, and the results show that compared with traditional discrete method, this method can greatly reduce the calculation time under the condition of ensuring a certain degree of accuracy, which verifies the effectiveness of the proposed method. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 2021 The 2nd International Conference on power Engineering, ICPE, 2021.

关键词： power flow calculation Time-domain continuity Electric-gas integrated energy system Unified energy path model Taylor series expansion method

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Implementation of Active NPC Circuits in Transformer-Less Single-Phase Inverter With Low Leakage Current

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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS 2017年第6期53卷 5658-5667页

作者： Zhou, Liwei Gao, Feng Xu, Tao Shandong Univ Key Lab Power Syst Intelligent Dispatch & Control Jinan 250061 Shandong Peoples R China

Transformer-less grid-connected photovoltaic (PV) systems face the challenge of keeping low leakage current due to their nonisolation configurations. To better attenuate the leakage current in the single-phase systems, a few neutral-point-clamped (NPC) topologies have been proposed. This paper further proposes an active NPC method by only employing one additional switch to connect the midpoint dc link and the freewheeling circuit of traditional single-phase PV inverters. After exploring the operational principles of freewheeling circuits, the construction method and the implementation of active NPC circuits in transformer-less single-phase inverters are elaborated in detail. Since only the leakage current flows through the additional NPC switch, the presented single-phase NPC inverters could still maintain the high operational efficiency with the further attenuated leakage current. The experimental results verified the theoretical findings.

关键词： Common-mode (CM) voltage leakage current neutral-point-clamping (NPC) circuit photovoltaic (PV) inverter

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Online Preventive control Method for Static Voltage Stability of Large power Grids

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IEEE TRANSACTIONS ON power systemS 2020年第6期35卷 4689-4698页

作者： Yun, Zhihao Cui, Xinhui Shandong Univ Minist Educ Key Lab Power Syst Intelligent Dispatch & Control Jinan 250061 Peoples R China

The real-time preventive control is particularly critical because the integration of renewable energy aggravates the random fluctuation of large power grid operating state. An online preventive control optimization method for static voltage stability is proposed based on the Thevenin equivalent parameter identification. According to the definition of the stability margin, its quantitative relationship with the control variable is derived to meet the real-time and reliability requirements of online applications. The preventive control optimization model is constructed to minimize control cost and consider voltage stability margin and operation constraints under multiple critical contingencies. The generator terminal voltage and shunt capacitor in this paper are taken as continuous and discrete control variables respectively. The derived analytical relationship between stability margin and control variable is linearized to form linear security constraints, and the optimization model is transformed into a mixed-integer linear programming problem, which can be solved by CPLEX quickly and reliably. The accuracy and rapidity of the proposed method are verified on several test systems.

关键词： Large power grid preventive control optimization voltage stability

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Integrated generation–consumption dispatch based on compensation mechanism considering demand response behavior

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Journal of Modern power systems and Clean Energy 2018年第5期6卷 1025-1041页

作者： Yumin ZHANG Xueshan HAN Li ZHANG Bo XU Mingqiang WANG Ming YANG Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong University State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University

Demand response(DR) is important to account for behaviors of the demand side to yield an optimal dispatch result. However, it is difficult for energy suppliers to collect customers' private information unless there is an incentive mechanism for customers to do so. Therefore,this paper proposes a new integrated generation–consumption dispatch based on compensation mechanism considering DR behavior. Firstly, in light of the dayahead load forecast data, we deduce the utility function model of different customers. By subtracting generating units' operation cost from consumers' total utility, the dispatch model has a decentralized demand participant structure based on this utility function. The utility function is used to describe consumers' preferences and energy consumption behaviors. Secondly, an effective compensation mechanism is designed to ensure customers to select the level of compensation appropriate to their willingness to curtail load. Finally, a new dispatch model is proposed that incorporates the DR compensation mechanism into the generation–consumption dispatch model. The new model can improve the interaction of generation and consumption,and benefit both the energy supplier and its customers. The proposed model is piecewise linearized and solved by a mixed-integer linear programming method. It is tested on a six-bus system and the IEEE 118-bus system. Simulation results show that the proposed model can realize both maximum social welfare and Pareto optimal results.

关键词： Compensation mechanism Demand response Demand utility function Integrated generation– consumption dispatch

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Distributed cooperative voltage control of wind farms based on consensus protocol

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INTERNATIONAL JOURNAL OF ELECTRICAL power & ENERGY systemS 2019年 104卷 593-602页

作者： Guo, Yifei Gao, Houlei Wu, Qiuwei Shandong Univ Minist Educ Key Lab Power Syst Intelligent Dispatch & Control Jinan Shandong Peoples R China

The increasing penetration level of wind power brings a number of challenges to power system operations. Voltage/reactive power control is an important task of a wind farm to fulfill the grid requirements and avoid the cascading trip faults of wind turbines (WTs). To address this issue, a distributed cooperative voltage control strategy is proposed for wind farms based on the consensus protocol in this paper. In the proposed voltage control scheme, a droop-based local controller is adopted for the primary voltage control based on the local measurements. A consensus-based distributed secondary voltage controller is proposed, aiming to regulate the voltages within the feasible range while optimizing reactive power sharing among the reactive power sources using the local and neighboring information. The controller parameters are determined by the closed-loop system stability analysis using a linearized model. A wind farm with 20 WTs was used for the case study to validate the proposed control scheme under both steady-state and fault-ride-through (FRT) conditions. Moreover, the robustness against a communication link failure and plug-and-play capability of the proposed voltage controller were tested.

关键词： Consensus protocol Reactive power Voltage control Wind farm

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