分布式电源和电动汽车大量接入配电网，打破了配电网的三相平衡状态，致使传统的配电网保护方案无法适应时代的发展需求。为此，在现有平衡系统故障恢复策略的基础上，提出了一种基于电动汽车充电站的不平衡配电网灾后两阶段故障恢复策略。第一阶段以故障恢复成本最小为目标确定故障后的孤岛运行方案。第二阶段综合考虑电动汽车充电站及各分布式电源机组的折旧、运维、弃负荷惩罚等成本，以配电网运行收益最大为目标建立协同优化模型，以确定故障时各充电站出力情况。最后通过改进的IEEE 33节点系统验证所提两阶段故障自愈模型及优化运行策略的有效性。结果表明，所提方法较传统的孤岛划分法弃负荷率更低，为解决不平衡配电网的故障恢复问题提供了新思路。

 The three-phase equilibrium state of a distribution network is broken owing to the large number of distributed power sources and electric vehicles connected to the distribution network, resulting in the traditional distribution network protection scheme illegally adapting to current development needs. Therefore, this study presents a two-stage fault recovery method for imbalanced distribution networks based on electric vehicle charging stations using an existing balancing system fault recovery technique. The island operation strategy after the fault is determined in the first stage to reduce the fault-recovery cost. In the second stage, a collaborative optimization model is established to determine the output of each charging station when a fault occurs, with the goal of maximizing the operating income of the distribution network, considering the cost of depreciation, operation and maintenance, and the load abandonment penalty of electric vehicle charging stations and distributed generation units. Finally, the enhanced IEEE 33 node system validates the effectiveness of the two-stage fault self-healing model and the optimal operating method suggested in this study. The results reveal that the proposed technique has a lower load rejection rate than the classic island division method, thereby providing a novel solution to the fault-recovery problem of an imbalanced distribution network.

日益增加的户用光伏发电系统改变了配电网的潮流分布,同时对配电网的线损产生显著影响。为了便于量化分布式光伏电源(distributed photovoltaic generation,DPG)接入三相四线制低压配电网的运行经济性,文章以三相不平衡线损为研究目标,首先建立了适用于低压配电网平衡态和不平衡态的线损计算模型;通过引入DPG接入模式、位置及容量3种要素,建立DPG不同接入模式下的线损变化量模型;以此为基础,提出一种考虑DPG接入模式的有源低压配电网的三相不平衡线损计算方法。在进行计算时,所提方法既可利用实时电流数据,也可利用易采集到的有功电量数据进行计算。最后,以低压配电网的典型参数为例验证了该方法的准确性与可行性,说明此方法可为DPG单相、三相接入低压配电网的线损计算提供参考依据。

The increasing number of household photovoltaic power generation systems has changed the power flow distribution of the distribution network, and at the same time has a significant impact on the line loss of the distribution network. In order to quantify the operating economy of distributed photovoltaic generation (DPG) connected to the three-phase four-wire low-voltage distribution network, this paper takes the three-phase unbalanced line loss as the research objective, and firstly establishes a balanced and unbalanced line loss calculation models suitable for low-voltage distribution network. By introducing three influencing factors of DPG access mode, location and capacity, the line loss variation model under different DPG access modes is established. A model for estimating the three-phase unbalanced line loss of the active low-voltage distribution network considering the DPG access mode is proposed. This method can be calculated by using both real-time current data and easily collected active power data. The accuracy and feasibility of this method is verified by taking typical parameters of low-voltage distribution network as an example, and the method can provide reference basis for line loss calculation of DPG single-phase and three-phase access to low-voltage distribution network.

With the extensive use of the new generation of synchronous condensers, the security issues of condensers have become increasingly prominent. The inter-turn short circuit of excitation winding is a common fault, which directly affects the normal operation of the synchronous condenser. In this paper, aiming at the analysis of the fault characteristics of the inter-turn short circuit of the excitation winding of the synchronous condensers in the unbalanced state of the grid voltage, the unified mathematical characterization of the air gap flux density and the unbalanced magnetic pull of the rotor under the four working conditions of the normal operation of the synchronous condensers and the occurrence of the inter-turn short circuit fault of the excitation winding, the failure of the unbalanced voltage synchronous condensers and the occurrence of the inter-turn short circuit fault of the excitation winding is established. The rotor vibration characteristics of the synchronous condensers under different working conditions are analyzed, and the harmonic content and harmonic amplitude are compared and analyzed, and the fault mechanism of the condenser is revealed. Based on the TTS-300-2 new synchronous condenser of a station, the finite element simulation model under four working conditions is established, and the experimental verification is carried out in the dynamic simulation laboratory with the MJF-30-6 fault simulation synchronous motor to simulate the operation of the condenser.The results indicate that under unbalanced voltage conditions, a decrease in air gap magnetic density occurs during faults, and the rotor experiences three harmonic components of magnetic imbalance forces. Through simulation analysis and experimental verification, the accuracy of the theoretical research results has been fully confirmed, which lays a solid theoretical foundation for the fault diagnosis of the synchronous condenser.

电动汽车（electric vehicle，EV）充电站利用其剩余无功功率容量向电网提供辅助服务，既能帮助电网实现自动电压控制（automatic voltage control，AVC），也能为充电站带来额外的收益。因此，提出了EV充电站调压辅助服务的市场机制，建立了充电站内充电桩的电路拓扑结构，并分析了充电桩进行无功功率支撑的基本原理。在此基础上，利用概率统计学和蒙特卡洛法，考虑电动私家车、电动出租车各自对应的充电需求，分别模拟了其充电行为；并结合充电桩的功率约束和变压器容量约束，预测出了充电站日内负荷分布曲线；进而评估出充电站日内无功功率支撑能力，并计算出日内充电站参与调压辅助服务所取得的收益。对充电站内快充充电桩的相关参数进行灵敏度分析，体现出不同参数对应的EV充电站无功功率支撑能力的差异，为充电站申报参与调压服务容量并获取相关补偿收益提供技术分析手段。

Electric vehicle （EV） charging stations utilize their remaining reactive power capacity to provide auxiliary services to the power grid, assisting in achieving automatic voltage control （AVC） and generating additional revenue for the charging stations. In this paper a market mechanism for the voltage regulation auxiliary services of EV charging stations is proposed, the circuit topology of charging piles within the charging station is established, and the basic principles of reactive power support by charging piles are analyzed. Based on this, using probability statistics and the Monte Carlo method, considering the charging demands of electric private cars and electric taxis, the charging behaviors of each are simulated. Combined with power constraints of the charging piles and transformer capacity constraints, the daily load distribution curve of the charging station is predicted. Furthermore, the reactive power support capability of the charging station within a day is evaluated and the revenue obtained from the participation of the charging station in voltage regulation auxiliary services within a day is calculated. Sensitivity analysis of relevant parameters of fast-charging piles within the charging station is conducted, highlighting the differences in reactive power support capabilities corresponding to different parameters of EV charging stations. This provides technical analysis tools for charging stations to declare their participation capacities in voltage regulation services and obtain relevant compensation benefits.

针对充电站聚合电动汽车充/放电调度问题，提出了一种计及车主需求的电动汽车聚合商（electric vehicle aggregator，EVA）能量优化调度策略，以最小化EVA长期购电成本。首先，充分考虑车主需求和外部电网电价的时变性，建立起EVA能量调度框架；其次，根据车主充电需求差异性设计了3种充电模式：双向调度模式、单向调度模式和快速充电模式，并分别建立负荷模型；然后，基于强化学习设计EVA的实时能量调度策略；最后，通过真实数据的仿真算例以及同其他贪婪算法的对比，验证了所提策略的合理性和有效性。结果表明，基于所提策略前两种调度模式较贪婪算法下的调度模式在一个月内可分别为EVA节省54.1%和47.5%的购电成本。

Aiming at the charging/discharging scheduling problem for charging station aggregation of electric vehicles, an optimal energy scheduling strategy is proposed for a electric vehicle aggregator (EVA) that takes into account the demands of vehicle owners with the goal of minimizing the long-term power purchase cost of EVA. Firstly, adequate consideration of vehicle owners demands and the time-varying nature of external grid tariffs, an operational framework for EVA energy scheduling management is established. Secondly, the electric vehicles (EVs) are classified into three charging modes according to the difference of users' charging demands, that is, two-way-dispatch EVs, one-way-dispatch EVs and fast-dispatch EVs, and load models are established respectively. Then, based on reinforcement learning theory the real-time energy scheduling strategy is designed for EVA. Finally, the reasonableness and effectiveness of the proposed algorithm are verified by simulation examples of real data and comparing with other greedy algorithms. The results show that the first two scheduling modes based on the proposed strategy can save 54.1% and 47.5% of the cost of EVA in one month, compared with the scheduling mode under the greedy algorithms.

The transition from internal combustion engines to electric vehicles (EVs) has received significant attention and investment due to its potential in reducing greenhouse gas emissions. The integration of EVs into electric and transport systems presents both benefits and challenges in energy management. The scheduling of EV charging can alleviate congestion in the electric system and reduce waiting times for EV owners. The use of renewable energy sources (RESs) for EV charging and supporting the grid can help mitigate the uncertainty of these energy resources. Vehicle-to-grid (V2G) technology can be used as an alternative approach in the event of sudden high consumption of the grid. Additionally, cost minimization through large-scale coordinated planning is crucial for the future of e-mobility systems. This review paper focuses on the latest trends considering the various approaches and features in coordinated EV scheduling, as well as the influence of different stakeholders, categorized as single- and multiple-charging stations (CS) and aggregator levels. By implementing coordinated EV scheduling, various methods are presented to better manage the needs and satisfaction of EV owners as well as the profit of CS and the market trends of e-mobility systems. In this regard, EV charging strategies considering V2G, uncertainty evaluation of parameters, coordinated charging management, congestion of CSs and electrical lines, route mapping, and technical and economic aspects of the system hierarchy, including consumers, CSs and aggregators, are reviewed and discussed.