Although the impact of persistent perturbation from renewable energy on power system stability has been studied, the effects of slowly varying disturbances remain unexplored. This paper proposes a new stability concept, locally differential input-to-state stability (LDISS), based on the input-to-state stability framework. The new concept enables the characterization of system stability under slowly varying fluctuations in renewable energy output. A Lyapunov-like analysis method provides a stability condition for LDISS. The analytical approach is applied in a single-machine infinite-bus system with additive perturbation to analyze its stability. Experimental results on the same system verifies the theoretical method.

In the existing power system with a large-scale hydrogen storage system, there are problems such as low efficiency of electric-hydrogen-electricity conversion and single modeling of the hydrogen storage system. In order to improve the hydrogen utilization rate of hydrogen storage system in the process of participating in the power grid operation, and speed up the process of electric-hydrogen-electricity conversion. This article provides a detailed introduction to the mathematical and electrical models of various components of the hydrogen storage unit, and also establishes a charging and discharging efficiency model that considers the temperature and internal gas partial pressure of the hydrogen storage unit. These models are of great significance for studying and optimizing gas storage technology. Through these models, the performance of gas storage units can be better understood and improved. These studies are very helpful for improving energy storage efficiency and sustainable development. The factors affecting the charge-discharge efficiency of hydrogen storage units are analyzed. By integrating the models of each unit and considering the capacity degradation of the hydrogen storage system, we can construct an efficiency model for a large hydrogen storage system and power conversion system. In addition, the simulation models of the hydrogen production system and hydrogen consumption system were established in MATLAB/Simulink. The accuracy and effectiveness of the simulation model were proved by comparing the output voltage variation curve of the simulation with the polarization curve of the typical hydrogen production system and hydrogen consumption system. The results show that the charge-discharge efficiency of the hydrogen storage unit increases with the increase of operating temperature, and H2 and O2 partial voltage have little influence on the charge-discharge efficiency. In the process of power conversion system converter rectification operation, its efficiency decreases with the increase of temperature, while in the process of inverter operation, power conversion system efficiency increases with the increase of temperature. Combined with the efficiency of each hydrogen storage unit and power conversion system converter, the upper limit of the capacity loss of different hydrogen storage units was set. The optimal charge-discharge efficiency of the hydrogen storage system was obtained by using the Cplex solver at 36.46% and 66.34%.

Aiming to predict the charging and discharging power of electric vehicles, a Power Prediction method for Electric Vehicle is proposed by considering their real-time State of Charge (SOC) values and desired SOC values. Firstly, targeting weak links in urban power grids, a road network model was constructed based on Markov chains and a spatiotemporal travel chain for electric vehicles, whereby real geographic coordinates of urban areas serve as the research subject. Then a model was established for the charging and discharging load of electric vehicles at weak links in the power grid. Finally, based on real-time State of Charge (SOC) values and desired SOC values, the charging and discharging power of electric vehicles was predicted. The proposed method for predicting the charging and discharging power of electric vehicles can not only mitigate the impact of a large number of electric vehicles connecting to the grid on its weak links and improve the stability of the distribution network, but also significantly meet the actual charging power demand of urban electric vehicles. Through the study of cases, the effectiveness of the method was validated.

Considering the cleanliness characteristics of distributed energy under dual-carbon background, this paper proposes a two-layer optimization method with distributed energy stations based on demand response. Firstly, in the upper level planning model, the optimal allocation scheme of distributed energy is determined with the aim of minimizing the comprehensive cost of the station area. Based on the optimal configuration scheme of the upper layer, the lower operating model optimizes the TOU price with the aim of minimizing the operating cost of the station area. Then, aiming at the problem of insufficient accuracy of gull search algorithm, an improved gull search algorithm is proposed to solve it. Levy flight strategy is introduced to enhance the search direction diversity of the algorithm and the ability to jump out of local optimal. Finally, based on the simulation results and comparative analysis of IEEE33-node system, the rationality and effectiveness of the model and solution method are verified.

已有不少文献从多个方面对同步调相机和STATCOM作出比较,对响应时间的观点却存在显著差异,其原因在于对响应时间的定义及其计算方法的不一致,也在于对电网影响因素界定得不清晰.然而,响应时间又较为重要,以至于有时是一个影响方案能否被推荐的重要技术指标.首先约定阶跃响应时间的定义及其计算方法,接着搭建简单的、便于验证的等值系统,以便清晰地界定电网影响因素的边界条件,最后通过电磁暂态数字仿真技术从三个基本方面分别详细对比同步调相机和STATCOM阶跃响应时间.结果表明:同步调相机仅在电网电压幅值阶跃时,瞬态响应时间才略优于STATCOM.

Proton exchange membrane（PEM） electrolytic hydrogen production is flexible in operation and has excellent adaptability to renewable energy fluctuations. It is a green hydrogen production technology with great development prospects. However, in the actual operation of PEM electrolysis for hydrogen production, there may be ion contamination,which has a great impact on the performance and operating life of the PEM electrolysis stack. In this paper, the source of ion pollution is firstly analyzed. On the one hand, it comes from residual metal cations in water, such as Na + , Ca 2+ , Mg 2+ , etc. On the other hand, trace metal ions may come from chemical or electrochemical corrosion of key materials inside the electrolysis reactor and system water circulation pipelines, such as Fe 3+ ,Cu 2+ , Ni 2+ , etc. Then the effects of different ion contamination on electrolytic performance are reviewed, including ohmic overpotential, cathodic reaction overpotential, and anodic reaction overpotential. Finally, ion pollution mitigation strategies are reviewed to avoid the energy efficiency and cost problems caused by impurity ion pollution during large-scale electrolytic hydrogen production.

Reliable and accurate extraction of ambient modes is an essential means of assessing the safety and stability of smart grids. While previous works have mainly concentrated on the introduction of novel identification tools. In this paper, the isolation forest ( iForest ) was presented to build an intelligent ambient mode extraction scheme with high reliability, which aims at detecting and eliminating abnormal ambient modes from extracted results. As the core technology of the proposed intelligent scheme, iForest exploits the concept of isolation and intends to combine the features of the outliers, which are 'few' and 'different', with the technique of ensemble learning to isolate them precisely. And the abnormal modes can be eliminated according to their anomaly scores in the proposed intelligent ambient mode extraction scheme. The evaluation of the proposed scheme is carried out through the database constructed by an IEEE 16-generator system and a real power system, the results of which indicate that the proposed scheme is intelligent enough to deal with a large amount of data with high accuracy and improve the reliability of existing identification tools.

Fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions. In this case, carbon corrosion occurs. Oxygen evolution reaction (OER) catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage. The mixture of hydrogen oxidation reaction (HOR) and unsupported OER catalyst not only reduces the electrolysis efficiency, but also influences the initial performance of the fuel cell. Herein, Ti4O7 supported IrOx is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode. When the cell reverse time is less than 100 min, the cell voltage of the MEA added with IrOx/Ti4O7 has almost no attenuation. Besides, the MEA has a longer reversal time (530 min) than IrOx (75 min), showing an excellent reversal tolerance. The results of electron microscopy spectroscopy show that IrOx particles have a good dispersity on the surface of Ti4O7 and IrOx/Ti4O7 particles are uniformly dispersed on the anode catalytic layer. After the stability test, the Ti4O7 support has little decay, demonstrating a high electrochemical stability. IrOx/Ti4O7 with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell.

本文建立了混合直流输电系统的小信号模型,通过与时域模型的动态响应进行对比,对其准确性进行验证.基于此模型,采用特征值分析和参与因子分析的模态分析原理,对影响主导模态的主电路参数与对应的控制器参数间的耦合关系进行分析,提出了二者基于拉格朗日拟合法的曲线拟合方法,从而得到不同主电路参数下控制器参数的最优值.研究结果表明,当系统强度减小或直流电容增大时,应当根据拟合曲线适度选择更大的比例系数并减小其积分系数,以增强系统稳定性.

As wind power on a large scale is connected to the grids through direct current transmission, the stability of the receiving-end grids drops off sharply and some of them become weak grids. In this paper, a modified virtual synchronous generator (MVSG) control strategy for receiving-end converter is proposed. Based on the traditional VSG active power-frequency loop control, this control strategy introduces the PI control of frequency deviation. Therefore, the converter can realize the no deviation control of the frequency, which can enhance the voltage and frequency stability of the receiving-end weak grid. On this basis, this paper proposes a coordinated power control method between wind farm and receiving-end grid, which solves the problem of power source of MVSG control. Finally, based on the Matlab/Simulink simulation software, a three-terminal model of wind power connecting to the receiving-end grids is established to verify the effectiveness of the proposed control strategy. The simulation results demonstrate that the proposed control strategy can reasonably allocate power and enhance the stability of the weak grid when load disturbance occurs in it.

A method to evaluate the transient voltage stability of high proportion wind power transmission network is proposed. Starting from the transient overvoltage calculation formula, the calculation formula of the limit short-circuit ratio is derived, and then the limit short-circuit ratio is obtained by taking the transient overvoltage amplitude as the known quantity. Considering the influence of wind farm grid connection on the short-circuit ratio, the calculation formula of the system short-circuit ratio after wind power grid connection is further derived, and then the limit short-circuit ratio is taken as the known quantity, The ultimate wind power permeability corresponding to the ultimate short-circuit ratio is calculated by substituting the formula, which is used as an index to evaluate the transient voltage stability of high proportion wind power transmission terminal system.

氢储能系统具有灵活高效、清洁无污染、不依赖自然环境、可长期存储的优点,在电网侧与用户侧都有广阔的发展前景.电解槽电堆和燃料电池电堆是氢能系统的关键设备,密封性是电堆可靠运行的必要前提.为此梳理了多界面耦合密封机理、密封材料选型、密封结构设计的主要研究进展,对比强调了氟橡胶、聚烯烃类橡胶在耐蚀和耐久方面的优势,分析提出了框架包裹质子膜密封结构在大面积多层电堆上的应用前景,为我国大功率质子交换膜(PEM)电堆性能提升提供了参考与建议.

电网发生大功率扰动时,系统频率在大幅度偏移情况下,还可能存在明显的时空分布现象.通过对单机系统频率响应特性和两机系统的频率差异的分析,提出了大频差下考虑非线性因素的系统频率解析模型,以此来估算故障扰动下系统频率的最大偏移量.提出通过在不同时间选择在不同地点采取紧急控制的协调配合方法,在减小频率最大偏移量的同时,改善频率时空分布现象,从而提高电网的频率安全稳定性.

C 3 F 7 CN/CO 2 gas mixtures is considered to be one of the most potential SF 6 alternative gases on account of its excellent insulation and environmental-friendly performance. The research on the decomposition characteristics of C 3 F 7 CN and Epoxy resin (EP) with insulation defects can provide a reference for formulating the operation and maintenance strategy of environmental-friendly electrical equipment. In this paper, the partial discharge experimental platform of gas-solid insulation system was established, the degradation experiments of C 3 F 7 C N /EP with different discharge intensities were carried out, and the characteristics of products with test time and discharge intensity were obtained. The result showed that the types of gas decomposition products increased with the discharge time increasing. The main decomposition products of C 3 F 7 CN/EP with surface discharge were CF 4 , C 3 F 8 , C 3 F 6 , C 6 F 14 , C 4 F 6 , C 4 F 10 , C 4 F 8 , CF 3 CN, CNCN and C 12 F 7 H 17 O 2 . It can also be found that, with the increase of discharge intensity, the appearance time of some products was advanced and the rate of gas production increased, and the product CNCN appeared.

Membrane water content is of vital importance to the freezing durability of proton exchange membrane fuel cells (PEMFCs). Excessive water freezing could cause irreversible degradation to the cell components and deteriorate the cell performance and lifetime. However, there are few studies on the critical membrane water content, a threshold beyond which freezing damage occurs, for cold storage of PEMFCs. In this work, we first proposed a method for measuring membrane water content using membrane resistance extracted from measured high frequency resistance (HFR) based on the finding that the non-membrane resistance part of the measured HFR is constant within the range of membrane water content of 2.98 to 14.0. Then, freeze/thaw cycles were performed from −50 °C to 30 °C with well controlled membrane water content. After 30 cycles, cells with a membrane water content of 8.2 and 7.7 exhibited no performance degradation, while those higher than 8.2 showed significant performance decay. Electrochemical tests revealed that electrochemical surface area (ECSA) reduction and charge transfer resistance increase are the main reasons for the degradation. These results indicate that the critical membrane water content for successful cold storage at −50 °C is 8.2.

针对现有暂态电压状态的多样化以及暂态电压稳定模型训练速度有待进一步提升的问题,提出一种基于电压轨迹簇和多类间线性判别分析(Multiple Between-class Linear Discriminant Analysis,MBLDA)的交直流系统暂态电压稳定评估方法.首先,获取故障后系统关键节点电压受扰轨迹簇信息,借助轨迹簇的几何属性建立暂态电压稳定评估的原始特征集.进而采用ReliefF算法对原始特征集进行压缩,筛选出与系统暂态电压稳定状态密切相关的特征子集,有效表征暂态电压稳定的四种状态(电压迅速恢复、电压延迟恢复、持续低电压、电压振荡).然后,将高维电压特征空间的特征值方程转化为欠定齐次方程组,提高暂态电压稳定评估模型的训练速度,进而建立大规模系统电压特征集与4种暂态电压稳定状态的映射关系.最后,通过修改后的IEEE39节点系统和修改后的IEEE145节点系统的仿真分析,验证所提方法的可行性与有效性.

The increasing demand for carbon emission reduction has drawn wide attention on the green hydrogen-manufacturing technology. Hydrogen production by water electrolysis based on renewable energies has the lowest carbon emission among the main hydrogen manufacturing methods. This study summarizes the hydrogen demand, hydrogen industry planning, and demonstrations of hydrogen production by water electrolysis. The water electrolysis technology is analyzed, including alkaline water electrolysis and proton exchange membrane (PEM) water electrolysis. Research reveals that improving electrocatalyst activity, catalyst utilization, bipolar plate surface treatment, and electrolytic bath structures helps optimize the performance of PEM electrolytic baths and lower equipment cost. The PEM water electrolysis has high operating current density, low energy consumption, and high output pressure; therefore, it accommodates the fluctuation of renewable energy power generation and can be easily combined with renewable energy consumption. Considering the technical characteristics of hydrogen transportation and electrolytic hydrogen production as well as hydrogen transportation demand in China, a solution for green hydrogen generation and long-distance transportation is proposed. High-

Photovoltaic power (PV) generation systems connected to distribution network are able to effectively absorb local solar energy and improve the reliability of power supply. The virtual synchronous generation (VSG) technology used in inverter of the PV can help it improve the ability of connecting to power system by increasing system inertia and damping. This paper proposes an optimized VSG control strategy which is based on spatial phase analysis to solve the fault problem of PV system facing unbalanced voltage fault in grid so that the reliability of PV system can be improved. In details, the proposed strategy is able to control the fault current and reduce second harmonic component of power of PV system connected to grid by analyzing different vectors affecting different electrical parameters. The simulation carried on PSCAD/EMTDC proves the effectiveness and superiority of proposed improved VSG strategy compared with P/Q and normal VSG strategy.

Due to environmental and energy shortage issues, inverter-interface renewable energy sources, such as photovoltaic and wind generations, has been becoming main power suppliers in modern power system, which compliments with challenges of dynamic stability of power system. Different fault ride through (FRT) control strategies have been presented in literatures for different typical renewable generators to enhance the dynamics of power system. However, there lacks of a general FRT control model to facilitate the characteristics analysis of different renewable generators. By investigating control models of typical renewable generators, this paper proposes a general FRT control mode considering low voltage ride through (LVRT) and high voltage ride through (HVRT) simultaneously for typical inverter interfaced renewable generators. Detailed control diagram and logics of the general control mode based on the FRT standard of inverter interface renewable generators in China has been presented and discussed. Finally, case study based on MATLAB/Simulink has been performed, and the preliminary simulation results verify that the proposed general FRT control mode can adapt to analysis of typical renewable generators during faults successfully.

In this paper, a high-efficient recursive correction state estimation method is proposed for the real-time tracking of power system states. Here, both the field timing measurements and trigger measurements from supervisory control and data acquisition systems are considered. In this regard, timing measurements are processed by a conventional batch mode estimator, while trigger measurements are processed in a novel continuous-data-stream manner, which enables the high refresh rate update of power system states. Each type of measurement runs its own state estimation in parallel, and only the estimated results are exchanged with each other. Extensive numerical results involving several IEEE standard systems validate the timeliness, accuracy, and robustness of the proposed state estimation method.