Addressing the unreliability and inaccuracy of current offline fault location methods for overhead distribution networks,this study proposes an offline fault location method based on satellite timing.To locate the fault,an AC voltage signal of fixed frequency and phase is injected at the fault line's origin after power isolation.Subsequently,the fault line is manually surveyed with a portable signal receiver.Synchronous sampling,enabled by satellite timing,allows for the determination of the zero-sequence impedance angle at each monitoring point without voltage data.The precise fault location is deduced by analyzing the variance in zero-sequence impedance angles across multiple monitoring points.Moreover,the study examines how the injected signal's frequency,the fault point's transient resistance,and clock synchronization discrepancies affect the accuracy of fault localization.Simulations validate the approach's precision in identifying fault locations.
Wideband oscillation emergency control is one of the"bottom line"measures to ensure the safe operation of wind power systems.It is difficult to establish an accurate mathematical model to assess this risk,due to the complex and variable nature of wind power systems.To address this issue,a new emergency control strategy has been proposed that is based on data analysis.Firstly,a wideband phasor monitoring algorithm has been developed to detect and assess wideband oscillation.Secondly,the largest Lyapunov exponent(LLE)is used to measure the dynamic evolution trend of wideband oscillation and identify its source.The oscillation source is identified by analyzing the negative resistance characteristic of the wind turbine.Based on the identification results,an online risk assessment method for wideband oscillation has been proposed and applied to the emergency control strategy.The effectiveness and reliability of the proposed method have been verified using a real-time digital simulator(RTDS)hardware-in-the-loop platform.
With the increasing complexity of power systems in recent years,transformer operation safety has become a key issue that affects the stable operation of the power system.Currently,calculation methods of short-circuit current through transformers are mostly based on the power grid topology and transformer equivalent impedance.These methods have low flexibility and real-time performance and do not consider the actual operation mode of the system,making it difficult to meet the requirements of real-time operation of power systems.In this paper,a transformer short-circuit current calculation method considering flow conditions is proposed based on a graph convolutional neural network.By introducing the features of transformer bus and regional topology,a transformer short-circuit current calculation model is trained.This method introduces attention mechanisms to make the model more sensitive to dynamic power flow conditions under different operating conditions.Verified by an actual power grid example in a region,the calculated short-circuit current using this method has a small error compared to the reference value,and the distribution of calculation errors is concentrated,which can basically meet the requirements of short-circuit current calculation in practical operation.
英国是世界上新能源发电接入率最高的国家之一，新型电力系统的特点在英国已经较为明显。英国总调在频率管理方面的成果和经验对中国新型电力系统建设有很高的借鉴价值。首先研究分析了英国总调在新型电力系统建设中，在频率管理方面遇到的风险及其产生机理。然后研究分析了英国总调应对风险的方案和实践经验。最后，研究分析了英国总调在频率管理方面的方案和实践经验对中国新型电力系统建设中频率管理的启示。参照英国的频率管理体系和辅助服务市场建设路径，中国应当重点关注频率管理体系的完善、系统惯量需求的研究和频率支撑技术的研发及应用。此外，应提前布局相关标准，避免分布式电源大面积脱网的风险。
随着台风、暴雪等极端恶劣环境的不断常态化，单相接地故障（如单相断线、单相击穿等）频繁发生，严重危害了电网安全。单相断线故障是引发森林火灾的常见故障之一，导线断线坠落至地面附近，在极短间隙内对地放电引燃地表附着的易燃物，最终引发森林火灾，对社会经济和自然环境危害严重。针对森林火灾风险下的配电线路单相断线对地放电发展过程研究建立短间隙放电模型，可以获得断口对地放电过程中的电场分布、电子平均能量分布、电子密度分布，以及不同断口外形对放电过程的影响机理。研究结果表明，随着断口半径从0.5 mm降至0.3 mm，流注头部的电场强度从80 kV/cm升高到110 kV/cm，电子平均能量从10 eV升高到11 eV，流注贯穿间隙时电子密度的最大值由1.5×1020 m-3升高到2.7×1020 m-3。断口半径越小、曲率越大，导致流注头部的电场强度和电子平均能量升高，流注头部电子密度和放电电流增加，更容易导致流注贯穿间隙。而断口不规则时由于具有更大半径，间隙击穿需要更长时间，因此放电电流峰值由9 A升高至15 A。如果考虑松针等含油量较高的地表附着物影响，该放电电流极易点燃地表附着物并形成电弧、引发火灾。该研究结果对于极端天气下的配电线路安全防护、预防森林火灾具有重要意义。
In the context of the current"double carbon"goal,we vigorously advocate energy transformation,and the development of renewable energy is rapid.Pumped-storage power stations play an important role in energy storage.How to evaluate its operating energy efficiency comprehensively and quantitatively under the actual large-scale wind and electricity grid connection is the premise of providing scientific decision-making variables for the construction investment,operation design and economic optimization of pumped storage power stations.For this reason,this paper first establishes the energy efficiency evaluation index of the power station from different dimensions according to the multiple functions of the pumped storage power station,and analyzes the typical scenario and intensity of the efficiency of the pumped storage power station in the actual system operation.Then,a set of comprehensive efficiency quantitative evaluation systems is constructed by using the fuzzy comprehensive evaluation method,and a multi-layer evaluation set is set up by combining the evaluation indicators to realize the energy efficiency evaluation of the pumped storage power station from part to the whole.Finally,based on the simulation of an actual power grid system in the northwest region,the comprehensive efficiency of the pumping and storage power stations in the region is quantitatively evaluated at different time scales such as season/year.
The diode rectifier unit can improve the economy and reliability of the long-distance large-capacity offshore wind power DC transmission system.This paper presents an optimal configuration method for AC filters in offshore wind power integration systems based on the 24-pulse diode rectifier unit.Firstly,the structure of the offshore wind power transmission system based on the 24-pulse diode rectifier unit is defined,and the basic principle of the 24-pulse diode rectifier unit is expounded.Then,the reactive power requirement of the 24-pulse diode rectifier unit is calculated.For the 24-pulse diode rectifier unit,the complicated AC filter can be simplified into a capacitor.By scanning the filtering effect of capacitors with different capacities in the range of active power variation,the reactive power capacity optimization method of the capacitor is proposed,which takes the filtering effect and the filter capacity into consideration.Finally,in PSCAD/EMTDC,the harmonic analysis and AC filter optimization design of the offshore wind power test system based on the 24-pulse diode rectifier unit are carried out.
Source and load prediction is an important basis for virtual power plant(VPP)to make future dispatching plans.A collaborative optimization scheduling method of VPP generation side and user side based on multi-frequency combination short-term source load prediction is proposed.First of all,ensemble empirical mode decomposition(EEMD)is performed on the load data of the time series and reconstructed into two kinds of frequency,which is then predicted by the graph convolution network and long short-term memory(GCN-LSTM)fusion algorithm.The prediction results obtained from the multi-frequency model are aggregated into an uncertain fuzzy set.Considering the demand response,the VPP day-ahead two-layer optimal scheduling model is established.The upper layer takes the user benefit maximization as the goal,comprehensively utilizes the scheduling function of demand response,and optimizes multiple types of controllable loads based on the established time-of-use price.The lower layer aims to minimize the output cost of distributed power supply and take into account the interests of both sides of supply and demand,so as to optimize the internal resources of VPP.The above model is decomposed into main and sub-problems for solving by using the improved column reduction generation algorithm.The economy,robustness,and effectiveness of the proposed model are verified by a case analysis.
To address the problems of large load peak and high operating costs brought by the large-scale charging of electric trucks to the power grid,a two-layer coordinated optimal dispatch method is proposed for peak shaving and valley filling.Firstly,load prediction of electric trucks is carried out by considering logistic characteristics,acquiring the driving behaviour of electric trucks,and obtaining charging load curves.Fuzzy C-mean clustering is used to divide the charging loads into dispatchable and non-dispatchable categories,and the schedulable potential is measured.Secondly,the minimum variance of total load is selected as the objective function.The upper layer optimization model is constructed,and the daily charging scheme of electric trucks is formulated.Then,the optimal daily charging scheme of the upper layer is transferred to the lower layer,and the lower layer optimization model with the lowest operating cost of the electric trucks as the objective function is constructed by considering the flexible time window constraints.The two-layer optimization dispatch is implemented with the variance of charging loads and the operating cost.Finally,the two-layer optimization model is solved by an adaptive particle swarm algorithm under the master-slave game framework,and the simulation verification is carried out using actual electric truck data in a logistics park.The results show that the proposed two-layer optimization dispatch method can effectively achieve smoothing the load profile of the grid while reducing the operating costs of electric trucks.
随着风电、光伏的大规模并网，电力系统面临灵活调节能力不足的挑战。水电运行灵活，通过与风光协同规划、互补运行，能有效平抑新能源出力波动，保障并网消纳。水风光协同规划的关键之一在于对水电灵活调节能力进行准确建模，其中振动区约束不容忽略。为此，提出了考虑水电振动区的水风光协同规划模型。该模型首先利用组合数学技术将水电机组振动区合成为电站振动区；然后，综合考虑振动区约束及梯级水力联系、水力发电方程等各项约束，实现对水电系统的准确建模；最后，耦合水电系统与新能源、联络线等相关运行约束形成水风光协同规划模型，并采用混合整数线性规划进行求解。以乌江流域某水风光互补系统为例，验证所提模型的有效性。
Distributed rooftop photovoltaic(PV)is spread geographically and affected by geographic shading and weather factors.It causes differences in distributed PV power output characteristics,making it challenging to predict distributed rooftop PV power at the substation level accurately.This paper proposes a day-ahead power prediction method of distributed rooftop PV based on a double attention mechanism-transformer model.Firstly,the similarity between the output characteristics of distributed PV users is determined using the dynamic time warping method and classified using the agglomerative hierarchical clustering approach.Secondly,the self-attention mechanism is used to learn the temporal correlation characteristics between each time step,and the channel convolution attention mechanism learns the correlation between multiple feature variables,and a day-ahead power prediction model is constructed.Finally,the day-ahead prediction results of each class are summed up to achieve the day-ahead power prediction at the substation level.The example results show that the proposed method in this paper significantly improves the prediction accuracy compared with Transformer,long short-term memory neural network,and time series convolution network under various weather conditions.
Most of the traditional controllers used in the frequency control function of isolated island microgrid are fractional order PID(FOPID)controller and fuzzy fractional order PID(FFOPID)controller,both of which have limitations in control performance.To solve this problem,a variable universe hybrid fuzzy FOPID hybrid controller is designed to improve the frequency control performance of isolated microgrid.By comparing the performance of FOPID,FFOPID and variable domain hybrid FFOPID controller,it is demonstrated that variable domain hybrid FFOPID controller has better control performance than other controllers in the frequency control of islanded microgrid.At the same time,the disturb of measurement noise is considered,which reduces the control performance of the controller and increases the frequency fluctuation of the islanded microgrid.To solve this problem,the dynamic data reconciliation(DDR)based filtering technology is used.The time-domain simulation results of the output of the frequency fluctuation of the islanded microgrid when FOPID,FFOPID and variable universe hybrid FFOPID controller is used respectively,the effectiveness of DDR filtering technology on improving the control performance of the various controllers in islanded microgrid is validated.
Due to the rapid development of power elec-tronics technology,medium-voltage DC transmission has attracted more and more attention in DC confluence occasions of photovoltaic,offshore wind power and other new energy stations due to its suitability for long-distance transmission.In the case of low-voltage input and medium-voltage confluence output of new energy power generation,in order to increase the DC transmission voltage and further reduce device stress,the input-parallel output-series(IPOS)structure is often used.Although this modular series-parallel structure has many advantages,due to the device parameter error between modules,there is a problem of unbalanced voltage and current in each module,which affects the stable operation of the entire power conversion system.For this reason,this paper proposes an IPOS multi-module improved droop control equalization method for medium-voltage DC confluence applications.It can realize the complete balance of output voltage and power of each module without adding communication between modules,which improves the traditional droop control the problem that the voltage does not match the reference value,and further improve the dynamic response performance of the system.Based on this control method,a three-way modular IPOS system prototype is built,and the equilibrium effect of the proposed droop control method on the IPOS system is verified through experiments.
面对新型电力系统的低惯量趋势，规模庞大而位置分散的温控负荷在参与电力系统频率响应的同时，能够为电网提供虚拟惯量和一次调频支撑将是提升电网频率安全的新思路。为此，以集中-分布式调控框架下的温控负荷集群为研究对象，首先在详细分解控制层调控中心、协调层聚合商、响应层温控负荷终端三者在辅助调频过程中的采样、计算、控制、执行一系列实时任务的基础上，设计了事件触发与时间触发相结合的温控负荷集群终端异步响应机制，实现温控负荷集群功率遵从综合惯性控制律的效果。随后，对所提综合惯性控制下温控负荷集群参与调频的电力系统进行频率响应建模，并进一步利用改进劳斯近似实现系统降阶，从而获得系统频率响应关键特征的时域解析表达式。最后，通过仿真算例验证了所提基于时间触发机制的温控负荷集群综合惯性控制的有效性，并分析了采用改进劳斯近似对系统模型降阶的可行性。
With the continuous increase in the penetration rate of new energy generation such as wind power and photovoltaic,the equivalent inertia level of the power system is continuously decreasing,and the uneven spatial distribution is becoming increasingly prominent.The ability of the power system to maintain frequency stability is closely related to the level of equivalent inertia of the system,so it is of great significance to clarify the spatiotemporal evolution trend of equivalent inertia in the power system.This paper analyzes the spatiotemporal evolution trend of equivalent inertia in China's power system based on a system dynamics model.First,clarify the concept of equivalent inertia and effective inertia composition of the new energy power system,and analyze the inertia response process.Then,based on system dynamics models,the installed capacity of photovoltaic,wind power,thermal power,hydropower,and nuclear power in various regions of China from 2025 to 2060 is predicted,taking into account multiple factors such as region,technological progress rate,and comprehensive cost.Finally,based on the predicted data,analyze the spatiotemporal evolution trend of equivalent inertia in China's power system.The predicted installed capacity results in this paper are in line with the long-term development goals set by China.The calculated equivalent inertia level of the power system intuitively reflects the overall and regional changes in China under the scenario of considering virtual inertia or not.This can provide references for planning new energy development in various regions,determining inertia compensation measures in low inertia areas,and ensuring frequency safety in China.
为应对气候变化和顺应第三次工业革命的大趋势，全球能源架构转型的新趋势将清洁能源发展提升至新高。从项目财务效益、宏观经济效益、社会效益、环境效益及政治效益共5个方面构建海外清洁能源和电网联网项目效益的针对性评价模型；然后采用组合赋权法与物权可拓法两种方法测算不同类型的清洁能源项目或电网联网项目的效益，包括商业类项目与示范类项目；最后以146个国家（地区）作为研究对象，对海外清洁能源与电网联网项目进行效益量化评测。结果表明，加纳、肯尼亚、苏里南、多哥、卡塔尔、斯洛伐克、厄瓜多尔、伊拉克等国家评测结果居于前列。该效益评估模型为建立海外清洁能源与电网联网项目的效益动态跟踪机制提供了一定理论基础，并从综合效益维度为海外能源投资项目的区域选择提供了决策参考。
With the transformation of the regional balancing modes of new-type electric power systems and markets,the balancing demand of electricity generation and consumption entities is increasing while participating in market transactions.There is an urgent need to explore new balancing service modes under new-type power systems.Initially,based on the analysis of domestic and international balancing mechanism practices,this paper proposes the concept and operation mode of the independent balancing service providers aimed at regional multiple entities balancing.It delves into the similarities and differences between the operational modes of new type entities in electricity markets and independent balancing service providers.Subsequently,a double-layer optimization model is constructed,targeting maximum revenue for the independent balancing service provider and minimal balancing cost for the electricity generation and consumption entities.Finally,the proposed model is validated through an analysis of a case study involving daily typical deviations in electricity generation and consumption in a certain region.The results demonstrate that the operation mode of the independent balancing service provider can reduce the balancing costs of market entities while ensuring the provider's revenue,considering the interests of both parties.This provides a valuable exploration of the balancing modes of new-type power systems.
The construction of a new energy system dominated by renewable energy and energy storage has become the development trend of energy transformation.Aiming at the problems of the poor economy of electrochemical energy storage technology and the mismatch between supply and demand of energy quality,based on the concept of energy cascade utilization and the business model of the sharing economy,this paper explores the new technologies and new business forms of shared energy storage stations for cogeneration and discusses the basic operation principles,technical and economic characteristics and business models of this energy storage mode.The case analysis of a typical cogeneration shared energy storage power station consisting of high-temperature solid heat storage,waste heat boiler,and steam turbine shows that under the current market environment,the internal rate of return is 10.6%and the payback period is 8.2 years when the solid heat storage as energy storage equipment is optimized for economic optimization.Meanwhile,the study reveals the influence rules of capacity leasing ratio,ancillary service price,heating,and energy storage unit investment on the technical and economic performance of the shared energy storage station.Finally,key issues such as equivalent energy storage capacity and multiple income models of cogeneration shared energy storage stations are discussed from technical and market perspectives.
传统配电网可开放容量评估未充分考虑电动汽车充电负荷与常规负荷的时空相关性，导致评估过于保守，难以指导配电网实际规划。为此，提出了一种考虑电动汽车（EV） 充电负荷与常规负荷时空相关性的配电网可开放容量评估方法。首先通过考虑EV充电负荷与常规负荷的时空相关性选取负荷典型日；接着构建可开放容量评估鲁棒随机优化模型，并采用KKT条件将其转化成单层模型；最后，在改进IEEE 33节点系统上仿真，验证了所提方法的优点。结果表明，相较于传统方法，所提方法基于对负荷相关性的量化，可获得更准确合理的配电网可开放容量。研究结果可为配电网规划提供科学依据。
