基于深度学习的配变停电电量损失预测

停电电量损失预测可为电网调度及规划提供参考,有利于为用户提供可靠供电服务。针对当前配变停电过程中的电量损失问题,先基于模糊C均值聚类算法实现对配变负荷曲线的分类处理及精细化分析,挖掘配变负荷数据规律;在此基础上,运用皮尔逊相关系数算法提取选择输入特征,构建基于门控循环单元神经网络的预测模型,从而得到停电时间负荷值,进而分析预测负荷曲线得到损失电量;最后,基于停电管理工作分析,实现基于粒子群优化的台区用电行为停电优化问题求解。算例测试验证了所提方法的正确性和有效性。     

考虑源-荷发展不确定性的电网扩展规划模型

在城市电网的发展过程中,随着可再生能源及储能等可控负荷的大规模接入,系统内源-荷实时功率供需关系与未来容量发展的不确定性将会增加,导致可再生能源利用率降低,并给上级电网带来调峰压力。为解决这一问题,文章充分考虑源-荷发展不确定性对系统的影响,以总规划成本最小为目标,建立了基于多重不确定性的电网模糊扩展规划模型及其求解方法。通过仿真算例验证了所提模型可有效地提升电网规划的经济性。     

Difference between grid connections of large-scale wind power and conventional synchronous generation

In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.     

A methodology for analysis of impacts of grid integration of renewable energy

Present electricity grids are predominantly thermal (coal, gas) and hydro based. Conventional power planning involves hydro-thermal scheduling and merit order dispatch. In the future, modern renewables (hydro, solar and biomass) are likely to have a significant share in the power sector. This paper presents a method to analyse the impacts of renewables in the electricity grid. A load duration curve based approach has been developed. Renewable energy sources have been treated as negative loads to obtain a modified load duration curve from which capacity savings in terms of base and peak load generation can be computed. The methodology is illustrated for solar, wind and biomass power for Tamil Nadu (a state in India). The trade-offs and interaction between renewable sources are analysed. The impacts on capacity savings by varying the wind regime have also been shown. Scenarios for 2021–22 have been constructed to illustrate the methodology proposed. This technique can be useful for power planners for an analysis of renewables in future electricity grids.     

微网能量管理方案研究

为协调微电网分布式电源、储能单元、负荷与电网之间的能量流及实现系统运行的经济效益最大化,同时保证可靠供电,需要考虑合理可行的能量管理策略,给出了微网能量管理的系统结构图,从能量管理策略、优化目标、约束条件及优化求解算法等四方面优选多种微网能量管理方案,并进行了比较分析。     

The economics of large-scale wind power in the UK A model of an optimally mixed CEGB electricity grid

Previous calculations of the economics of large-scale wind power have been generally limited to the evaluation of the marginal cost of energy, assuming that the addition of a wind farm to an electricity grid does not change the mix of base, intermediate and peak load plant in that grid. Here a simple but powerful numerical generation planning model has been constructed for grids containing wind farms and three classes of thermal power station, but no storage. Electricity demand and available power are specified by empirically based probability distribution functions and the plant mix which minimizes the total annualized costs of the generating system is determined. Capacity credit of wind power is automatically taken into account in the optimization. Using the model, the breakeven costs of wind energy in a model British CEGB grid, containing coal, nuclear, oil and wind driven power plant, are evaluated under various conditions. For a wide range of parameter values, large-scale wind power is likely to be economically competitive in this grid.     

电动汽车参与受阻风电消纳的源荷优化控制方法

大规模的电动汽车负荷可增加电网系统的调峰能力,消纳受阻风电。文章首先根据系统负荷和风电出力特性分析其受阻原因;其次,通过对电动汽车充放电特性、可时移特性和SOC模型的分析,建立了电动汽车充放电模型,并提出相应策略;然后,以电动汽车消纳后的风电剩余受阻量最小为目标,建立电动汽车参与受阻风电消纳的源荷优化控制模型,并利用差分进化算法对模型进行求解;最后,以某地区电网实际数据进行仿真计算,验证电动汽车参与受阻风电消纳协调控制的可行性与有效性。     

含冷、热、电、气的园区综合能源系统选址定容规划案例分析

为实现含冷、热、电、气的园区综合能源系统的多能互补优势和能量梯级利用,以某园区综合能源系统项目实例为基础,从资源评估、负荷预测、综合能源系统建模、优化算法求解、区域供能站和管网规划原则等方面进行详细的案例分析。构建上层网损最小,下层全寿命周期内经济性最优的双层选址定容规划模型,通过改进粒子群算法进行优化求解,得到近景和远景区域供能站和各能源管网的最优选址定容方案,并结合项目数据验证了其合理性。将综合能源规划方案和传统分供规划方案进行对比,结果表明前者具有更好的经济性和节能性,可为园区级综合能源系统规划项目提供参考和思路。     

A hybrid optimization technique for proficient energy management in smart grid environment

Electrical energy is one of the key components for the development and sustainability of any nation. India is a developing country and blessed with a huge amount of renewable energy resources still there are various remote areas where the grid supply is rarely available. As electrical energy is the basic requirement, therefore it must be taken up on priority to exploit the available renewable energy resources integrated with storage devices like fuel cells and batteries for power generation and help the planners in providing the energy-efficient and alternative solution. This solution will not only meet electricity demand but also helps reduce greenhouse gas emissions as a result the efficient, sustainable and eco-friendly solution can be achieved which would contribute a lot to the smart grid environment. In this paper, a modified grey wolf optimizer approach is utilized to develop a hybrid microgrid based on available renewable energy resources considering modern power grid interactions. The proposed approach would be able to provide a robust and efficient microgrid that utilizes solar photovoltaic technology and wind energy conversion system. This approach integrates renewable resources with the meta-heuristic optimization algorithm for optimal dispatch of energy in grid-connected hybrid microgrid system. The proposed approach is mainly aimed to provide the optimal sizing of renewable energy-based microgrids based on the load profile according to time of use. To validate the proposed approach, a comparative study is also conducted through a case study and shows a significant savings of 30.88% and 49.99% of the rolling cost in comparison with fuzzy logic and mixed integer linear programming-based energy management system respectively.     

A framework to determine optimal offshore grid structures for wind power integration and power exchange

This paper presents a framework to find optimal offshore grid expansions using a transportation model of the power grid. The method extends the standard mixed‐integer linear programming approach to the solution of the transmission expansion planning problem to account for fluctuations in wind power generation and load; this makes the method especially suited to identify optimal transnational offshore high‐voltage direct current grid structures for the integration of large amounts of offshore wind power. The applicability of the method is demonstrated by a case study of the North Sea region. Copyright © 2011 John Wiley & Sons, Ltd.     

含冷、热、电、气的园区综合能源系统选址定容规划案例分析

为实现含冷、热、电、气的园区综合能源系统的多能互补优势和能量梯级利用,以某园区综合能源系统项目实例为基础,从资源评估、负荷预测、综合能源系统建模、优化算法求解、区域供能站和管网规划原则等方面进行详细的案例分析。构建上层网损最小,下层全寿命周期内经济性最优的双层选址定容规划模型,通过改进粒子群算法进行优化求解,得到近景和远景区域供能站和各能源管网的最优选址定容方案,并结合项目数据验证了其合理性。将综合能源规划方案和传统分供规划方案进行对比,结果表明前者具有更好的经济性和节能性,可为园区级综合能源系统规划项目提供参考和思路。     

Implementation of repowering optimization for an existing photovoltaic‐pumped hydro storage hybrid system: A case study in Sichuan,China

For a remote area or an isolated island, where the grid has not extended, a standalone hybrid energy system can provide cheap and adequate power for local users. However, with the development of society, the load demand will increase and the original system cannot completely meet the load demand. This situation occurs in Xiaojin, Sichuan, China. The existing photovoltaic‐pumped hydro storage (PV‐PHS) hybrid system in this area as the original system cannot completely meet the load requirements at present. The term “repowering” aims to maximize the reliability of power supply and the utilization of the PV‐PHS hybrid energy system that differs from traditional planning optimization to build all components. The repowering strategy is to integrate wind turbines (WTs) and battery into the original system. For the repowering system, a power management strategy is proposed to determine the operating modes of the PHS and battery. Three objectives, which are minimizing percentage of the demand not supplied, levelized cost of energy, and curtailment rate of renewable energy, are considered in the optimization model. Simulation is conducted by single‐objective, biobjective, and triobjective particle swarm optimization (PSO) techniques. For the single‐objective optimization, the comparison of PSO and genetic algorithm (GA) is made. For the double‐objective optimization, multiobjective PSO (MOPSO) is compared with weighted sum approach (WSA), and fuzzy satisfying method is utilized to find the win‐win solution. The results reveal that the repowering strategy can help to achieve maximum reliability of power supply after load demand increases significantly, and the battery plays an important role in such a hybrid system.     

输配电协调的网架规划方法

为使输电网规划与配电网规划互相协调、提高电网整体供电可靠性和投资效益,提出了输配电协调的网架规划方法。在传统网架规划模型的基础上,在输电网规划模型中引入配电网转供需求约束和输电网可靠率约束;在配电网规划模型中引入输电网N-2转供需求约束和线路平均负载率约束。并采用自适应搜索离散萤火虫算法求解输配电网网架规划模型,最后以华东某地区输配电网规划作为算例进行方案对比。结果表明,所提方法可行、有效,能提高电网规划的可靠性和投资效益。     

Optimal decentralized charging control algorithm for electrified vehicles connected to smart grid

Electrified vehicles (EV) and renewable power sources are two important technologies for sustainable ground transportation. If left unmitigated, the additional electric load could over-burden the electric grid. Meanwhile, a challenge for integrating renewable power sources into the grid lies in the fact their intermittency requires more regulation services which makes them expensive to deploy. Fortunately, EVs are controllable loads and the charging process can be interrupted. This flexibility makes it possible to manipulate EV charging to reduce the additional electric load and accommodate the intermittency of renewable power sources. To illustrate this potential, a two-level optimal charging algorithm is designed, which achieves both load shifting and frequency regulation. Load shifting can be realized through coordination of power generation and vehicle charging while reducing power generation cost and carbon dioxide emissions. To ensure practicality, a decentralized charging algorithm for load shifting is formulated by emulating the charging pattern identified through linear programming optimization solutions. The frequency regulation is also designed based on frequency droop that can be implemented in a decentralized way. The two control objectives can be integrated because they are functionally separated by time scale. Simulation results are presented to demonstrate the performance of the proposed decentralized algorithm.     

On the aggregate grid load imposed by battery health-conscious charging of plug-in hybrid electric vehicles

This article examines the problem of estimating the aggregate load imposed on the power grid by the battery health-conscious charging of plug-in hybrid electric vehicles (PHEVs). The article begins by generating a set of representative daily trips using (i) the National Household Travel Survey (NHTS) and (ii) a Markov chain model of both federal and naturalistic drive cycles. A multi-objective optimizer then uses each of these trips, together with PHEV powertrain and battery degradation models, to optimize both PHEV daily energy cost and battery degradation. The optimizer achieves this by varying (i) the amounts of charge obtained from the grid by each PHEV, and (ii) the timing of this charging. The article finally computes aggregate PHEV power demand by accumulating the charge patterns optimized for individual PHEV trips. The results of this aggregation process show a peak PHEV load in the early morning (between 5.00 and 6.00 a.m.), with approximately half of all PHEVs charging simultaneously. The ability to charge at work introduces smaller additional peaks in the aggregate load pattern. The article concludes by exploring the sensitivity of these results to the relative weighting of the two optimization objectives (energy cost and battery health), battery size, and electricity price.     

Electric power grid interconnections in Northeast Asia: A quantitative analysis of opportunities and challenges

Power grid interconnection has gained attention in Northeast Asia (NEA) as a means to build an economically efficient power system and to effectively utilize renewable energy, such as wind and solar resources in the Gobi Desert and hydro resources in Eastern Russia.In order to quantify the potential economic and environmental benefits from connecting power grids and developing renewables in NEA, we build an NEA-wide multi-region power system model using linear programming techniques. Our analysis considers power system characteristics, such as the seasonal and daily electric load curves of the various NEA economies.Compared to a “no grid extension” scenario, increased access to renewables contributes significantly to emissions reductions and fuel cost savings. However, the results imply modest benefits in lowering total cost because of the large initial investments needed in developing the renewables and the transmission lines. These limited total cost savings are likely to pose an implementation challenge for NEA grid interconnections. Our results also suggest that grid interconnections become more economically attractive in higher fuel price or lower initial cost situations. The relevant planning organizations should carefully consider the initial cost and future fuel price trends when considering how to interconnect power girds in an economical manner.     

On the ability of pem water electrolysers to provide power grid services

Water electrolysis is considered as a cornerstone technology for the large scale storage of energy and for carbon abatements in the frame of the energy transition. The purpose of this research work was to analyze power grid operational constraints, to design specific load profiles of interest for power grid management and then to use these protocols for the characterization and qualification of polymer electrolyte membrane (PEM) water electrolysers in view of grid balancing services. In the first section, management constraints of European power grids are described and analyzed. Using a typical regulation mechanism as an illustrative example, power specifications for primary and secondary reserve management are specified. The economics of such management procedures is also analyzed. In the second section, some key technical characteristics of PEM water electrolysis stacks are described. Test specifications designed for the qualification of water electrolysers to both primary and secondary reserve markets are defined. In the last section, selected test results are reported and the ability of PEM water electrolysis stacks to provide the services of interest is analyzed. In particular, a set of key performance indicators, designed for the characterization of PEM water electrolysers operating in transient power conditions of interest for grid services, are defined. Test results show the ability of PEM water electrolysis stacks to satisfy the most stringent grid constraints, but remaining limitations are identified. The main innovative contributions of this research work were to design test protocols for both primary and secondary power reserves management, and to demonstrate that PEM water electrolysers can be used for such applications.     

Low voltage ride-through strategies for doubly fed induction machine pumped storage system under grid faults

Pumped storage units bring stability to the electrical power system, so they must remain connected to the grid even during grid faults. In this paper, the authors propose efficient and simple solutions for a doubly fed induction machine pumped storage (DFIMPS) system during grid faults. In case of balanced grid faults, a control reconfiguration strategy is introduced and a hardware solution is applied in the case of unbalanced grid faults. The reconfiguration strategy consists of a commutation between different control strategies; when a balanced grid voltage fault occurs during pumping mode, the control algorithm switches to the synchronization one but based on the new grid conditions. So the proposed reconfiguration method reduces the negative impacts of grid fault occurrence on the DFIMPS system by cancelling rotor and stator over-currents and decreasing the electromagnetic torque and stator power oscillations. Simulation results carried out on a 4 kW DFIMPS system illustrate the effectiveness of the proposed approach.     

基于系统动力学的输配电网投资规划仿真分析

鉴于电网企业正从以最大程度满足用户侧需求为目的,逐步向同时追求保障供电安全和合理的投资经济效益的投资模式转变,通过确定电网投资与负荷增长、投资效益、政策因素和市场作用之间的相互影响关系及设定投资规划各子系统之间及系统内部的参数方程关系,构建了基于系统动力学方法的投资规划动态仿真模型,并以某地区电网发展数据为模型输入,对所建立的模型进行了多情景模拟分析,分别获得基准情景、负荷增长趋缓情景和市场力影响增加情景的仿真结果,验证了模型的有效性。     

Aggregator-based demand response mechanism for electric vehicles participating in peak regulation in valley time of receiving-end power grid

With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles (EVs), an aggregator-based demand response (DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator (ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.