Multi-stage power source and grid coordination planning method considering grid uniformity

Given the increasing uncertainties in power supply and load, this paper proposes the concept of power source and grid coordination uniformity planning. In this approach, the standard deviation of the transmission line load rate is considered as the uniformity evaluation index for power source and grid planning. A multi-stage and multi-objective optimization model of the power source and grid expansion planning is established to minimize the comprehensive cost of the entire planning cycle. In this study, the improved particle swarm optimization algorithm and genetic algorithm are combined to solve the model, thus improving the efficiency and accuracy of the solution. The analysis of a simple IEEE Garver’s 6-node system shows that the model and solution method are effective and feasible. Moreover, they are suitable for the coordinated planning of the power source and grid under a diversified nature of power supply and load.     

考虑无功裕度的受端电网暂态电压稳定性控制方法研究

随着送端电网中大规模可再生能源发电容量的增加,在一定程度上导致外送系统无功支撑容量不足,使得系统电压出现波动。另外,无功功率不能在传输网络中长距离有效传输,增加了受端电网的无功平衡控制的难度。文章针对大规模外送系统中的受端电压波动所导致受端电网电压稳定性降低的问题,提出了一种基于无功裕度的受端电网暂态电压稳定性控制方法。首先,对系统无功裕度以及电压稳定性进行分析,得到系统静态电压稳定极限与无功需求容量的关系;然后,通过分析受端电网各节点无功需求特性,在能够允许受端电网电压最大波动的条件下,进行系统无功裕度的确定;再通过机器学习算法进行无功裕度控制,达到系统电压稳定控制的结果。通过仿真验证表明,采用文章所提出的基于无功裕度的受端电网暂态电压稳定性控制方法,能够精确地得到受端系统电压稳定工况,实现系统电压的稳定控制。     

电网企业内部节能业务构建及应用

为响应国家节能减排号召,电网企业积极探索以合同能源管理的模式实施公司内部节能技术改造,通过高效的内部协同、外部联合,理顺节能项目管理,规范业务实施,开拓电力节能服务市场。电网改造项目以此模式探索实施后,取得了巨大的经济环境效益,促进了节能业务健康发展。     

VSC-HVDC在海上风电输电系统的应用研究

海上风电须进行远距离传输,大规模风电场采用直流输电技术的运营费用比交流输电技术低。为保证风能质量和电网稳定性,提出了应用VSC-HVDC直流输电技术,重点研究该直流输电系统的控制技术特点。在VSC-HVDC稳态数学模型的基础上,提出了用于该系统的闭环PI控制器,并辅以PSCAD/EMTDC建模仿真。仿真结果表明,该控制器简便有效,能够满足稳定运行的需求。     

基于枚举法的地区电网接纳风电能力评估

为准确评估地区电网的最大接纳风电容量,提出一种基于电网调峰能力约束、静态安全约束和暂态稳定约束的风电接纳评估体系。首先利用随机生产模拟技术评估风电并网后对系统备用容量的需求,进而修正传统调峰能力约束下接纳风电容量的评估;然后利用DIg SILENT平台的枚举法对各接入点可能出现的接入容量组合进行潮流计算,实现了全局搜索寻优。通过设置常见的大扰动工况进行机电暂态仿真验证,最终得到满足暂态稳定约束,即整个地区电网的最大接纳风电容量。     

风电系统的无功功率与电网电压稳定

论述了风电容量在占局部电网相当比例时,风电机组的无功功率调整与电网电压之间的关系,对于定速和变速风电机组的运行特性做了分析,提出了在需要做无功功率调整时风电机组应能满足的特殊要求。     

基于交叉权重因子的高比例风电接入电网有功校正控制方法

在重载线路输送功率约束下,充分挖掘轻载线路的输送能力,成为在现有网架结构下提高风电外送的重要途径。文章引用交叉权重思想,从潮流基本方程出发,利用线路潮流与注入有功功率灵敏度的关系,提出基于交叉权重因子的有功校正控制方法,根据交叉权重确定风电场调节顺序,使潮流分布均匀合理。该方法可充分发挥轻载线路功率输送能力,缓解在风电大发时部分线路重负荷问题,进而在电网结构不变的条件下有效提高风电送出功率。     

低压电网单相接地故障保护研究

介绍了TN-C、TN-S、TN-C-S低压配电系统接地形式的优缺点及应用条件;并对系统保护装置与接地方式的配合进行了介绍;推导出了采用过电流保护兼作接地故障保护时最大供电半径值的计算公式.     

基于信息安全约束的可再生能源电网多主体投资风险评估方法

针对电网建设过程中不同利益主体投资风险评估问题,结合物理信息融合的可再生能源电网各主体投资供需平衡和数据流信息安全模型,研究基于信息安全约束的可再生能源电网多主体投资风险评估方法。首先建立包含电网投资运营商、可再生能源投资运营商和电力用户等不同主体的投资模式,然后针对电力物联网环境下信息系统的设备风险、数据风险、物理系统风险和信息安全风险在复杂信息物理融合系统中的作用机理,研究复杂投资模式下系统信息安全风险量化表征模型,并在此基础上建立基于结构熵的信息安全约束的可再生能源电网多主体投资动态风险评估模型。基于IEEE39节点建立可再生能源电网投资风险评估仿真系统,对文章提出的风险评估方法进行验证。仿真结果表明,基于信息安全约束的电网多主体投资风险评估方法,能够有效提升具有不确定性的电网投资规划鲁棒性。     

以空气密度修正风力发电机组上网发电量方法的分析

在风力发电场的设计过程中,一般要根据风能资源和风机的性能对风力发电机组上网发电量进行估算.由于各风电场海拔高度和空气密度不同,使实际上网发电量与理论上网发电量相差较大.文章针对空气密度引起的上网发电量误差进行了分析,对空气密度修正计算方法进行了探讨,提出了更为合理的空气密度修正上网发电量的计算方法--月平均空气密度修正上网发电量法.     

A versatile method for computation of power pulsations in DFIG under grid imperfections

In the context of a Doubly Fed Induction Generator (DFIG) connected to the utility grid under unbalanced voltage conditions, the controller design needs to ensure additional challenges such as restricting the Total Harmonic Distortion (THD) in grid current, minimizing the pulsations in generated power, torque, dc link voltage etc. apart from facilitating the generator power control. Thus the schemes for generating reference currents for rotor converters need to incorporate a measure of power pulsations to what is required for steady state power flow control. This paper proposes a versatile scheme for computing the power pulsations in a DFIG connected to grid under unbalance voltage conditions. The active and reactive power oscillations are computed in a simple and straight forward manner using the measured stator voltage and currents in the positive d-q frame without using flux estimation. The scheme is free from flux integration or differentiation, rotor position computation and independent of machine parameters. Further, the worst case error in computation is bound within 3% considering 30% voltage dip, 7% of harmonics, ±10°phase jump or ±10% dc offset in the grid voltage. The effectiveness of the scheme is validated through PSCAD/EMTDC simulations and experimental results for a 2.3 kW DFIG test setup.     

分布式电源与电网同步的研究

在分布式电源并网系统中,通过获取电网侧的瞬时相位信息,使逆变器输出与电网保持同频、同相。文章分析了单同步坐标系软件锁相环算法和双二阶广义积分器锁相环算法的性能特点,根据优势互补的方法,通过检测电路检测三相电路的状态,正确地对锁相环进行切换,以快速精确的检测出正序电压和相位,保证系统中的逆变器正常工作。同时通过利用单纯形法对其锁相环的控制器参数进行优化。研究结果表明,根据电网侧的工作状态,合理地切换锁相环的工作模式,可以快速精确地追踪电网相位和频率信息。     

可逆流光伏与市电联合供电能量管理研究

针对光伏直流供电系统的能量变动性,提出了使用市电作为直流负载的能量补偿来源。系统由光伏电池、市电、移相全桥变换器、PWM整流器组成。在光伏发电能量大于负载所需时,将多余的能量馈送电网;在光伏发电能量不足时,由市网补充。系统的核心是实现光伏、市电、负载三者之间的能量管理。文章首先对整个供电系统进行了分析,然后讨论了系统的不同工作模式,最后提出了市电的能量补偿控制策略。仿真和实验表明所提的系统结构和控制策略能够实现市电与光伏供电系统的稳定联合供电。     

Electrical transients of wind turbines in a small power grid

This paper presents field measurements and calculations on the disconnection and braking of wind turbines (WT) with rated power 60 kW and 100 kW in the grid of two Greek Islands. By means of a digital acquisition system with sampling frequency of 130 kHz, voltages and currents of the WT installations have been measured and analyzed just before and during the transient period. A simulation program has been used for this purpose. Results of simulation and measurements show in a wide range a good agreement. The simulation program was further used to investigate the disconnection process of WT under various circumstances. It is shown that during the WT disconnection, a sudden increase in stator currents may appear. So voltage dips may distort the power quality of the grid. Self-excitation of WT, with large induced voltage, occurs when they operate at low-load even with relatively small capacitive compensation. The amount of energy, that the brake of a WT absorbs during the disconnection, has been studied under various disconnection procedures. Suggestions are made for the proper moment of brake application, so that the energy absorbed is minimum     

Distributed energy storage aggregation for power grid peak shaving in a power market

随着新一轮电力市场化改革的深入,为了促进分布式储能有效参与电网调峰,提出了对其规模化聚合管理的思路;建立了分布式储能聚合商以竞价形式参与电网调峰调度的优化模型。在日前调度中,聚合商根据电力交易中心公布的次日调峰需求,通过对分布式储能行为特性预测,并按阶梯报价策略参与竞价;电力交易中心以最小化调峰调度成本为目标优化调度计划。在实时调度中,考虑了储能行为特性日前预测误差和电池损耗,聚合商以最大化自身利益为目标优化充放电出力,使得聚合商在满足日前中标出力的同时,利用市场电价差获利。仿真算例表明,分布式储能聚合商以竞价形式参与电网调度既能减少电网调峰调度成本,还可以达到削峰填谷的效果,储能设备的损耗成本是影响充放电出力的关键因素。     

大量分布式光伏电源并网后的区域保护实现方法

研究了光伏电源并网的故障问题,分析了单个光伏电源并网与大量光伏电源并网的故障特性和保护动作特性。基于大量分布式光伏并网的运行特点及故障发生后的动作行为分析,提出了基于装置采集电量的主保护和基于网络通讯的区域后备保护方案。为尽量减少对现有系统的改动以及减少分布式光伏电源并网的投资,方案依托于新一代的分布式光伏并网接口装置来实现。该装置不仅能解决电网区域后备保护问题,还节约了投资,方便了现场设备安装和维护,为分布式光伏电源并网的大面积推广奠定基础。     

Extreme scenario extraction of a grid with large scale wind power integration by combined entropy-weighted clustering method

Large-scale integration of wind power into a power system introduces uncertainties to its operation and planning, making the power system operation scenario highly diversified and variable. In conventional power system planning, some key operation modes and most critical scenarios are typically analyzed to identify the weak and high-risk points in grid operation. While these scenarios may not follow traditional empirical patterns due to the introduction of large-scale wind power. In this paper, we propose a weighted clustering method to quickly identify a system’s extreme operation scenarios by considering the temporal variations and correlations between wind power and load to evaluate the stability and security for system planning. Specifically, based on an annual time-series data of wind power and load, a combined weighted clustering method is used to pick the typical scenarios of power grid operation, and the edge operation points far from the clustering center are extracted as the extreme scenarios. The contribution of fluctuations and capacities of different wind farms and loads to extreme scenarios are considered in the clustering process, to further improve the efficiency and rationality of the extreme-scenario extraction. A set of case studies was used to verify the performance of the method, providing an intuitive understanding of the extreme scenario variety under wind power integration.     

Energy and environmental performance of a heat pump in different power grid scenarios

Electric-driven heat pumps are one of the most encouraging systems that could support the raising of renewables contribution in civil sector energy consumption, especially with reference to the Countries with a high contribution of renewable energy sources in electricity generation mix. However, the evaluation of the effective energy and environmental performance of an electric heat pump meeting the space heating and cooling requests of a building has to consider several factors that affect the results. Among them great attention should be given to the variability of weather conditions in which the system operates, the changeability of the efficiency and environmental indicators of power grid. The analysis becomes more complex if the variation of these parameters is considered in terms of time and geographic location but it leads to the actual evaluation of the energy conversion system performance that is neglected by European Regulations. This paper presents an energy and environmental analysis of an electric-driven air-source heat pump providing the space heating and cooling needs of the same building located in two different geographical locations by means of a dynamic simulation performed in TRNSYS 17. The analysis is carried out considering the average and time-dependent values of the carbon dioxide emission factors for electricity and the power grid efficiency indicators evaluated by means of the real electricity generation data. In addition, the paper proposes the evaluation of the average and hourly energy and environmental parameters referred only to the electricity market zones in which the buildings are located. These indices are considered in the analysis too. The results have highlighted that the assessment based on average and high-resolution parameters, as well the evaluation based on indicators referred to electricity market zones only, could return very different outcomes leading to a significant overestimation or underestimation of the energy and environmental performance of the system based on the electric-driven heat pump. Finally, a further analysis has been carried out to determine how the results can vary considering the average value of the electric efficiency indicator suggested by Italian Regulations and that of other European Countries.     

Electric power grid interconnection in Northeast Asia

In spite of regional closeness, energy cooperation in Northeast Asia has remained unexplored. However, this situation appears to be changing. The government of South Korea seems to be very enthusiastic for power grid interconnection between the Russian Far East and South Korea to overcome difficulties in finding new sites for building power facilities to meet its need for increased electricity supplies. This paper analyzes the feasibility of this electric power grid interconnection route. The issues addressed include electricity market structures; the prospects for electric power industry restructuring in the Russian Federation and South Korea; the political issues related to North Korea; the challenges for the governments involved and the obstacles anticipated in moving this project forward; project financing and the roles and concerns from multilateral and regional banks; and institutional framework for energy cooperation. While there are many technical issues that need to be resolved, we think that the great challenge lies in the financing of this commercial project. Thus, the governments of the Russian Federation and South Korea involved in the project need to foster the development of their internal capital markets and to create confidence with international investors. To this end, on energy side, this involves defining a clear energy policy implemented by independent regulators, speeding up the already started but delayed reform process of restructuring electric power industry and markets, and establishing a fair and transparent dispute resolution mechanism in order to reduce non-commercial risks to a minimum. The paper argues that establishing a framework for energy cooperation in this region will contribute positively towards that end, although views differ regarding its specific form. Finally, given that North Korea has a crucial transit role to play and faces a very unstable political situation, it is concluded that moving the project forward needs to be contingent on a resolution of the North Korea's nuclear crisis.     

基于分布式发电的10kV电网无功优化关键算法的研究与实践

阐述了无功优化理论,介绍了无功优化的数学模型,提出了采用粒子群优化算法对含分布式发电的配电网进行无功优化的研究思路,并用算例进行仿真分析,得到了最终的优化方案。