Effective islanding can help a load recover quickly, which is helpful for improving the resilience of powers grid and reducing the impact of power grid failures, especially large-scale failures. In this paper, according to the actual structural and electrical characteristics of a power grid, a new index, "electrical edge betweenness", is defined, which is used to quantitatively evaluate the importance of each power line. Based on the similarity of the ideas of community structure mining in complex networks and island operation of each unit component in distribution networks, the island division problem is modeled as a power network community structure mining problem, and the Louvain algorithm is adopted to solve it. The maximum total recovery load is the objective function, and multiple constraints of safe operation are considered. Based on a comprehensive analysis, a distribution network island division scheme including a distributed power supply is obtained. Finally, IEEE 118-node system simulation is used to verify the effectiveness of the proposed method compared with other methods. The load recovery rate of the islanding method in this paper is 99.83%, which is higher than that of the methods proposed in references [29] and [30]. Therefore, the method proposed in this paper can be considered meaningful.

Due to the high dimension and redundant features of power system operating data, the disadvantages of manual analysis of power network security region gradually appear. SVM algorithm provides a new solution for mining the boundary of power grid security region. However, the data set of power system safety analysis has the problems of unbalanced samples and unequal misclassification costs. As a result, the traditional SVM algorithm, which takes classification accuracy as the optimization goal, cannot meet the requirements of power grid security region mining. Therefore, this paper solves the above problems by increasing the penalty for misclassification of unstable samples at the algorithmic level. In order to improve the classification accuracy and reduce the missed alarm rate, a dynamic security region algorithm is proposed, which takes into account the imbalance of samples and the difference of misclassification costs. Firstly, by introducing penalty parameters of sample misclassification cost, the influence of penalty parameters on classification accuracy and over-fitting index is analyzed. In order to reduce the rate of missing alarm, the SVM algorithm is modified by increasing the penalty for misclassification of unstable samples. In order to improve the classification accuracy of the algorithm, the concept of gray scale interval is introduced. By introducing grayscale interval into the output category probability, the classification results of samples outside the interval are almost reliable. Samples located within the interval can be further determined by time domain simulation. The balance between classification accuracy and missing alarm rate is realized. Finally, a CEPRI36 nodes system example is used to verify the effectiveness of the model and algorithm.

With the development of energy transition, the complexity of power systems’ structure, planning and operation is continuously increasing. As to quickly and accurately assess the dynamic security region of power system, there are prominent problems with traditional manual analysis method, i.e. the rules’ roughness and a low calculation efficiency while data mining approach could provide a new way to get off such problems. Considering that the performance of SVM algorithm depends on feature selection and the LightGBM, a fast and efficient classification algorithm, can be used for feature selection, this paper proposes a new algorithm based on a fusion model. With the CEPRI-36 bus power system, the results of different algorithms are compared and the proposed algorithm verified.

For real-time reporting of power supply interruption on LV users, there essentially need the availabilities of both the back-up supply for communication module in smart meter and the communication channel between smart meter and main station. This paper studies a real-time reporting solution which embeds super capacitor as the back-up supply of communication module in smart meter and uses micro-power communication scheme for LV users. Field tests of 30 LV distribution areas in Baoji Power Supply Branch verifies the proposed solution. The application prospects of the proposed solution are further discussed, such as interruption diagnosis and fault analysis, under urban and rural LV scenarios.

This paper analyzes the electricity transaction of distributed generation (DG) prosumers under different settlement modes in China. In general, DG prosumers have dual-directional power exchange with power grid and thus participate in both the purchase and sale of electricity, involving in the processes of metering, settlement, and billing. For DG prosumers, this paper presents several metering models, settlement mechanisms, electricity price of feed-in and off-grid. Furthermore, the economic benefits under different settlement modes are compared, including the ‘surplus generation’ and ‘total generation’ feed-in modes in China, and the net energy mode abroad, for DG prosumers, distribution system operator and governmental decision maker. The future challenges about DG prosumer development are discussed.

Power supply reliability on service reflects utility’s power supply level and directly affects the satisfaction of electricity users in the served region. Due to the difference of economic development levels in local areas, grid construction and management are often quite different, and thus it is not suitable to generalize their reliability target and improvement strategy. Through analyzing historical power interruption (PI) events, this paper settles up a reliability calculation model and then accordingly selects a number of indexes directly related to various departments in utility; further establishes a reliability evaluation model. In practical application, reliability targets are determined based on the evaluation of economic development, natural environment and grid infrastructure. Then reliability performance indexes of various departments are determined based on the reliability evaluation model. The proposed method are applicable in different supply area, with the simple and obtainable indexes of business process and the ease of applicable model, which can accurately identify weak parts of power supply reliability management and help to make efficient reliability improvement strategy. The proposed method has been applied to the distribution network in Honghe region since 2016 and achieved remarkable results so far.

欧洲配电行业的改革在全球范围内具有领先地位,配电网运营具有相对独立的特点,售电市场运营已有10年的经验.在欧盟低碳化目标的推动下,分布式资源、新型负荷大量接入配电网,配电运营及售电市场主体面临各种新挑战.基于欧洲能源监管机构、国际供用电会议CIRED 2017和CIRED2019的相关文献,介绍欧洲售电市场机制及其监管政策方面的现状,讨论售电费率结构对配电运营的影响,以及配电运营发展和研究方向.

In recent years, impedance-based methods have been widely used to analyze the stability of grid-connected converters. However, the impedance models in three-phase AC systems are 2 x 2 matrices and a strict stability analysis is based on the generalized Nyquist criterion, which involves eigenvalue computation. Hence many methods only study the diagonal elements of the impedance matrices, but the neglect of the non-diagonal elements may bring hidden dangers to the stability of the system. This letter proposes a stability criterion for grid-connected converters based on impedance models and Gershgorin's theorem. The effect of the non-diagonal elements is considered and the criterion is a strictly sufficient condition of stability, which is conservative but can guarantee the stability of the system.

第25届国际供电会议(CIRED 2019)于2019年6月3～6日在西班牙马德里召开.会议的主要内容包括大会主旨发言、7个专题讲座、19个圆桌会议、6个专业分会的论文宣讲、创新论坛及论文张贴等.CIRED 2019会议的主题是支持能源转型、配电行业的低碳技术,探讨欧盟2018年《清洁能源一揽子法》中2030年能效提高32.5％的新目标对未来配电行业发展的影响.

This paper presents the development history of China’s self-supply power station enterprise (SSPE) and discusses the classification of SSPE with respect to their economic roles and operational characteristics. During the current energy transition, development requirements of regulation and pricing policy for SSPE are analyzed to sort out the main challenges with respect to SSPE, and the issues need to be studied further in the future.

Safety management is essential for production and business enterprise to guarantee the safety of both personnel and property. Safety management practices of power grid enterprises in China have a history of several decades with continuous development and improvement. However, there are still many shortcomings, especially in distribution networks. Distribution network companies in European countries have more mature measures in distribution network safety management, and in particular many of which are applicable to the market-oriented business environments. This paper studies the structure of safety management system for power grid enterprises in China and Europe. Two kinds of management systems are discussed and compared to propose suggestions for future development of power grid safety management in China.

With the increasing penetration of renewable energies and power electronic devices, sub synchronous oscillations occur frequently. Phase-locked loop (PLL) is a key part for renewable energies integrating into power grid. Recent studies have shown that unreasonable setting of PLL parameters of is one of the important reasons for sub-synchronous oscillations. Impedance method is an effective method to study the system stability, but the obtained impedance is a two-dimensional matrix, which makes the analysis inconvenient. In order to preserve the simplicity of impedance method and ensure the accuracy of stability judgment, the Gershgorin disc theorem is applied to the generalized Nyquist criterion in this paper. Sufficient conditions of stability are derived, and the conservativeness of the method is improved. On this basis, the security region of the PLL control parameters is computed. Simulations verify the feasibility of the method.

“Quality of electric energy supply Harmonics in Public Supply Network GB/T 14549”, the first national harmonic standard in China, was released in 1993 and now has an age of 25 without revision. Based on reviewing the development history of Chinese harmonic standards, this paper discusses the main issues on the implementation of GB/T 14549, including harmonic voltage limits, measurement specifications, harmonic allocation principles and methods. This paper aims to clarify these issues so that they can be fully considered in the future development of harmonic standards. DEVELOPMENT HISTORY OF HARMONIC

以水电为主的直流孤岛送出系统中多次出现具有长振荡周期和稳定振幅的超低频频率振荡事件。考虑到水轮机的非线性特性,建立了水电孤岛系统的非线性描述方程进行研究。并对比了非线性系统和其线性化模型下的稳定性和表现,发现了水电孤岛系统中非线性模型下的Hopf分岔和稳定极限环现象。在一定的参数范围内,系统平衡点不稳定,但出现稳定的极限环,系统轨迹收敛到极限环而呈现出等幅振荡。进一步分析得到极限环特性与Hopf分岔参数的关系。分析结果为研究水电直流孤岛中频率稳定问题提供了一种理论上的可能,最后说明了考虑水轮机非线性的重要性。

New application developments in distribution network such as new energy resources, bidirectional interaction with end-users, electric vehicles, require for the safety, real-time, stability and reliability of power data collection. In the paper, the common communication technologies applied in low voltage distribution network and divied into three types (power line carrier, wireless and specific wire), are briefly discussed and compared. Then, a field testing case of BPL (broad power line carrier) application for meter reading in low-voltage networks is presented and analysised in detail.

When a frequency oscillation occurs, effective control measures should be taken to suppress the oscillation as soon as possible to avoid subsequent failures caused by the oscillation. Prime movers, including governors and turbines, with negative damping are the major cause of frequency oscillations, and quitting the primary frequency regulations of these units can increase the damping ratio of the system mode and make the oscillation decay. The dissipation energy flow method is further developed to evaluate the damping of prime movers for emergency control. The dissipation energy flow into the prime movers is computed online using phasor measurement data of 2–3 oscillation periods and is then used to evaluate the damping of the prime movers. The primary frequency regulations of the units with the lowest damping are quit to suppress the oscillation. The procedure of online emergency control is presented. Test results verify the validity of the proposed approach.

Employing thermal energy storage (TES) for combined heat and power (CHP) can improve flexibility in an integrated electric-thermal system (IETS) and therefore is beneficial to the accommodation of variable renewable energy sources (RESs). In general, there are two kinds of thermal storage: active thermal storage (ATS) and passive thermal storage (PTS). Active thermal storage capacity, provided by devices designed for special purposes, is generally fully exploited; passive thermal storage capacity, defined as the TES capacity provided by system components such as pipelines and building envelopes, has yet to be employed. To explore the possibility of using ATS and PTS for flexibility enhancement in the IETS, this paper presents a unified model of an IETS with both ATS and PTS in which heat transfer is included. In the proposed model, ATS is expressed by a phase-change TES device, and PTS is expressed by pipelines and heat consumers. Then, for the operation of the integrated system with both ATS and PTS, a dispatch model is presented, which can be simplified to a system with only ATS or only PTS by setting different boundary conditions. Finally, a test system is set up to verify the proposed model. The impact of factors such as transport time delays and temperature variation ranges in PTS is also analyzed in the test system. Results show that both ATS and PTS can provide extra flexibility in system operation and thus promote wind power accommodation. (c) 2017 American Society of Civil Engineers.

Zhangjiakou regional network belongs to the Jibei power grid in Northern China and locates at the midway of the power transmission corridor from Inner-Mongolia to the rest of Jibei power grid. Zhangjiakou regional network consists of several area networks connected to the main network through 500kV stations. In recent years, renewable energy in rural areas has developed rapidly and electrified railway traffic traction in urban areas is developing rapidly, which cause a significant impact on the power quality of the power supply system and even the main transmission network. In this paper, harmonic standards for power system planning in China are introduced firstly. Then the parameters of the minimum operation mode and the power supply capacity in harmonic planning are discussed. With the present standards, the determination principles and calculation procedures of the two parameters are proposed, to deal with the rapid development of the power grid.

Negative damping of prime movers is a major cause of sustained frequency oscillations in power systems. Increasing the damping torque of prime movers by adjusting governor parameters is an effective measure to prevent frequency oscillations. The oscillation frequency is volatile and turbine parameters change under loading conditions. To guarantee robustness and adaptability, the governor parameters should be adjusted to ensure sufficient damping torque over the entire range of oscillation frequency and under different turbine parameters. An optimization model of governor parameters is proposed. A constraint of the model is that the damping torque of the prime mover over the entire oscillation frequency range, and under different turbine parameters, must be greater than the threshold. The composite dynamic performance of primary frequency regulation under different loading conditions is the optimization objective. Test results validate the proposed method. The stability of the frequency oscillation mode under different conditions can be guaranteed.