分布式电源及微网对中压配电网 接线模式影响

对分布式电源及微网接入中压配电网的影响进行研究,从可靠性、经济性2方面定量评估分布式电源及微网对中压配电网典型接线模式的影响,协调分布式电源及微网接入与中压网架建设之间的关系,确定最优的接入位置,探索适用于分布式电源及微网接入的中压配电网的网架建设模式和发展思路。研究结果表明：微网接入架空辐射状电网时对供电可靠性的提升作用较为明显,且远端接入的可靠性提升作用最优;同时,需提高分布式电源及微网接入的经济性。     

分布式光伏电源对配电网网损的影响

当配电网中接入大量的受天气条件影响而出力具有随机性、波动性和间歇性的分布式光伏电源时,必然会对配电网网损产生影响。将分布式光伏电源集中接入配电网的末端,通过仿真研究了在不同的配电网的R/X、负荷水平、负荷功率因数下,分布式光伏电源的有功出力和功率因数对配电网网损产生的影响,并提出了利用网损变化率指标来量化对配电网网损的影响程度,全面总结了含分布式光伏电源的配电网网损的变化规律。     

考虑源-储特性的分布式电源并网阶段优化与评估方法

风光发电的随机性和波动性增大了分布式电源协调供电的难度。针对该问题引入储能电池平抑风光波动,采用阶段式优化与评估方法对含风电、光伏等分布式电源的配电网配置进行研究。第1阶段考虑负荷有功网损灵敏度的影响,确定风光电源的接入位置和容量;第2阶段首先以网损最小为目标确定储能电池的安装位置,然后综合考虑投资成本、电压稳定及弃风弃光率建立多目标函数,采用模拟退火-粒子群混合算法优化储能容量;第3阶段考虑风光出力的不确定性,采用概率潮流对储能平抑前后的电压和网损进行评估。最后,结合东北地区某实际配电系统进行仿真分析,验证该文方法的正确性和有效性。     

计及“源-网-荷”影响的主动配电网可靠性评估

为解决分布式电源、配网自动化系统及柔性负荷等广泛接入后的故障恢复和可靠性计算复杂问题,提出了计及“源-网-荷”影响的主动配电网可靠性计算方法。源侧考虑分布式电源作用,建立了以最大化恢复等值负荷为目标的孤岛划分模型。网侧分析了配网自动化系统对网架联络、负荷转供的影响,并提出了基于浴盆曲线的设备故障率模型。荷侧考虑柔性负载,引入弹性系数矩阵对电价激励型柔性负载进行精确建模。最后,通过对传统可靠性计算的最小路法进行改进,提出了计及“源-网-荷”影响的主动配电网可靠性计算方法。通过仿真分析,说明了所提模型和方法的有效性。     

新型负荷接入环境下的配电网分布式电源规划

随着电动汽车以及储能技术的不断成熟,电动汽车及储能设备等新型负荷的不确定性给分布式电源接入配电网的规划工作带来了新的挑战。基于机会约束,建立了一种考虑新型负荷特性的配电网分布式电源规划模型,该模型既包括电动汽车与储能设备等新型负荷,也包括分布式风电、光伏发电等典型分布式电源,并应用概率潮流和遗传算法对模型进行求解。对IEEE33节点测试系统的测试结果表明,接入新型负荷后系统不确定性增强、总体收益有所下降,验证了所建立的电源规划模型处理负荷及分布式电源不确定性问题的可行性。     

基于生命周期微网的经济性分析

针对微网经济分析指标体系不系统、不科学等问题,提出了基于生命周期综合考虑各分布式能源经济运行状况、对环境和不同种类负荷造成影响等因素,确定了各分布式能源等年值投资、拆卸、治污、负荷停电赔偿费用以及碳贸易、可靠性、政府补贴效益等来量化微网成本与效益的经济性指标。通过对算例4种微网方案进行经济性分析,验证了理论可行性,同时研究结果为微网投资决策提供了科学依据。     

基于电压灵敏度的分布式电源接入规划

考虑分布式电源接入对配电网运行电压和网损的影响,提出基于电压灵敏度的分布式电源规划思路。文章分析节点的负荷与电压之间变量关系,从而引入节点电压灵敏度,建立以DG为等效负荷的分布式电源接入容量模型,结合有功网损敏感度选址准则,规划出DG容量接入方案。采用IEEE33节点系统对方案进行验证,分析结果表明,网络损耗及电能质量均得到了明显改善,验证了该方案的有效性与可行性。     

考虑分布式电源接入的电网源荷时序随机波动特性概率潮流计算

鉴于分布式电源的时序随机波动特性和负荷需求侧的电能质量是分布式电源接入系统的重要影响因素,从风光典型分布式电源和负荷需求的时序波动性出发,建立了综合考虑源荷时序特性的概率潮流计算模型。利用基于模糊特征聚类的概率潮流算法对IEEE 14节点系统进行计算,对比分析负荷需求侧对系统电压波动的影响情况。结果表明,所采用方法能够全面合理地模拟分布式电源接入时电网随机波动过程。     

考虑负荷类型的含分布式电源系统对配电网电压的影响

针对配电系统自身的特点,考虑负荷类型,将恒功率、恒电流和恒阻抗结合起来组成ZIP负荷模型,在传统牛顿法的基础上,提出了一种计及负荷类型的改进的牛顿潮流算法.研究了不同类型分布式电源接入辐射型配电网络前后对系统各节点电压的影响.利用Matlab软件对33节点系统进行仿真,表明了该方法的可行性,比较分析了不同负荷类型,不同DG类型接入对配电网电压的影响,并根据测试结果总结出相关规律,所得结论可为DG接入配电网提供依据.     

基于APDE算法的配电网分布式电源承载力评估

针对分布式电源接入配电网装机容量问题,提出一种基于自适应扰动差分进化算法（APDE）的配电网分布式电源最大承载能力评估方法。首先建立包含有载调压变压器及静止无功补偿器的配电网模型,并优化系统潮流与注入功率的关系表达式,通过考虑分布式电源及负荷的不确定性,建立基于机会约束规划下的源荷不确定性配电网分布式电源最大承载力评估模型;然后对差分进化算法进行改进,形成APDE算法以求解模型;最后基于IEEE-33节点配电系统对所建配电网模型进行分析,验证其满足电力系统分析需求,并进一步对所提配电网分布式电源承载力评估方法进行分析,通过与相关算法比较,证明了所建模型的可行性和改进方法的有效性。     

考虑储能系统的微电网可靠性效益评估模型研究

可靠性效益是指微电网系统达到一定的供电可靠性水平而使用户减少的停电损失,也即获得的效益,储能系统的安装对微电网可靠性效益有着重要影响,为此需分析储能系统在微电网可靠性效益提升方面的作用。首先,基于总电量不足指标E_(ENS)成本的最小化构建微电网可靠性评估模型;其次,提出改进的蚁群算法,通过设置启发式参数改善其收敛性及计算精度;最后,选取典型微电网系统进行测算,分析电池储能系统的安装对微电网闲置容量、E_(ENS)分布及系统运行成本的影响。结果表明,电池储能系统的安装对微电网的可靠性效益带来积极影响;同时改进的蚁群算法在收敛性和计算时间上都有显著提升。     

Multilevel converters control for renewable energy integration to the power grid

The paper deals with the multilevel converters control strategy for renewable energy resources integration in distribution grids. The proposed control scheme ensures the injection of the generated power in the distribution grid with fast dynamic response, while providing an additional active power filtering capability providing the required harmonic and reactive currents to the considered non-linear loads. The proposed control scheme is applicable to a general multilevel converter and to any types of the renewable energy resources. The control scheme is validated by means of simulations with a three-level diode-clamped converter which interfaces a wind power generation system to a distribution grid supplying non-linear loads. From extensive simulation results, high performance of this control strategy in renewable energy application is demonstrated with reduced total harmonic distortion, increased power factor and compensated load’s reactive powers.     

Wind turbine fatigue loads as a function of atmospheric conditions offshore

In recent years, there has been a growing interest by the wind energy community to assess the impact of atmospheric stability on wind turbine performance; however, up to now, typically, stability is considered in several distinct arbitrary stability classes. As a consequence, each stability class considered still covers a wide range of conditions. In this paper, wind turbine fatigue loads are studied as a function of atmospheric stability without a classification system, and instead, atmospheric conditions are described by a continuous joint probability distribution of wind speed and stability. Simulated fatigue loads based upon this joint probability distribution have been compared with two distinct different cases, one in which seven stability classes are adopted and one neglecting atmospheric stability by following International Electrotechnical Commission (IEC) standards. It is found that for the offshore site considered in this study, fatigue loads of the blade root, rotor and tower loads significantly increase if one follows the IEC standards (by up to 28% for the tower loads) and decrease if one considers several stability classes (by up to 13% for the tower loads). The substantial decrease found for the specific stability classes can be limited by considering one stability class that coincides with the mean stability of a given hub height wind speed. The difference in simulated fatigue loads by adopting distinct stability classes is primarily caused by neglecting strong unstable conditions for which relatively high fatigue loads occur. Combined, it is found that one has to carefully consider all stability conditions in wind turbine fatigue load simulations. Copyright © 2016 John Wiley & Sons, Ltd.     

Integrated renewable energy systems for off grid rural electrification of remote area

The off grid electrification by utilizing Integrated Renewable Energy System (IRES) is proposed to satisfy the electrical and cooking needs of the seven-uneletrified villages in the Almora district of Uttarakhand state, India. Four different scenarios are considered during modeling and optimization of IRES to ensure reliability parameters such as energy index ratio (EIR) and expected energy not supplied (EENS). The optimum system reliability, total system cost and cost of energy (COE) have also been worked out by introducing the customer interruption cost (CIC). The four different renewable energy scenarios have been compared for the considered study area using the LINGO software version 10. The fourth renewable energy scenario accounting 44.99% micro hydropower (MHP), 30.07% biomass, 5.19% biogas and 4.16% solar energy along with the additional resources of wind (1.27%) and energy plantation (12.33%) has been found to be the best among the different options considered. Furthermore, the optimal reliability for the fourth IRES system has been found to be 0.95 EIR at the optimized cost of Rs 19.44 lacs with estimated COE of Rs 3.36 per kWh. The COE obtained using LINGO software and HOMER software has also been compared and briefly discussed for all the four scenarios. In order to verify feasibility and cost of system for different biomass fuel prices, a sensitivity analysis has also been carried out and it has been found that the fourth scenario is more sustainable than the other considered options.     

Optimal reserve capacity allocation with consideration of customer reliability requirements

An algorithm for determining optimal reserve capacity in a power market is presented in this paper. Optimization process in the proposed algorithm is based on the cost-benefit trade off. Market clearance is executed with consideration of uncertainties of power system components in an aggregated environment. It is assumed that both generating units and interruptible loads participate in the reserve market. In addition, customers’ reliability requirements are considered as constraints for decision making process of ISO. The rendered method considers random outages of generating units and transmission lines and determined outage of interruptible loads and employs Monte Carlo Simulation (MCS) for scenarios generation. Unlike previous methods in which a constant value is assumed for cost of the energy not supplied, a flexible value for this parameter is applied which shows an important effect in the evaluation results. The performance of the proposed method has been examined on the IEEE-Reliability Test System (IEEE-RTS).     

Optimization modeling method for coal-to-electricity heating load considering differential decisions

Heating by electricity rather than coal is considered one effective way to reduce environmental problems. Thus, the electric heating load is growing rapidly, which may cause undesired problems in distribution grids because of the randomness and dispersed integration of the load. However, the electric heating load may also function as an energy storage system with optimal operational control. Therefore, the optimal modeling of electric heating load characteristics, considering its randomness, is important for grid planning and construction. In this study, the heating loads of distributed residential users in a certain area are modeled based on the Fanger thermal comfort equation and the predicted mean vote thermal comfort index calculation method. Different temperatures are considered while modeling the users’ heating loads. The heat load demand curve is estimated according to the time-varying equation of interior temperature. A multi-objective optimization model for the electric heating load with heat energy storage is then studied considering the demand response (DR), which optimizes economy and the comfort index. A fuzzy decision method is proposed, considering the factors influencing DR behavior. Finally, the validity of the proposed model is verified by simulations. The results show that the proposed model performs better than the traditional method.     

Field experience on solar electric power systems and their potential in Palestine

Palestine has a large number of rural small villages far from the national electric grids. Electrical loads in such villages are mostly small and can be covered by means of photovoltaic (PV) generators, which are economically more feasible than extending the electric grid or using diesel electric generators. Since PV has been rarely used in Palestine, this paper is devoted to investigating the potential of PV applications in Palestine, identifying the barriers for prevalence of PV applications as in other countries and demonstrating the reliability and feasibility of utilizing PV systems by presenting the test results of a PV system by supplying a rural clinic with its power demands. A method for designing the PV power system respecting the local environmental conditions is presented in this paper. The results of the measurements carried out over two years verify the reliability of the applied method. The illustrated test results show how far the PV-power generation can be matched with load demands and state of battery charge even during periods of low solar radiation. This could be achieved by respecting the local weather parameters in the illustrated sizing method. Long term field experience in designing, testing and operation of PV projects outside Palestine is presented in this paper.     

Optimal dynamic load shedding policy for generation load imbalances including characteristics of loads

Modern electrical power systems are highly interconnected and heavily loaded. An emergency may occur as a result of a sudden increase in system load or unexpected partial or total outage of a generator. This paper presents an optimal dynamic load shedding policy for generation load imbalances. The effects of voltage and frequency characteristics of system loads, transmission lines, transformers and reactive power compensator are reported. Equality and inequality system constraints are also considered in the formulation of this nonlinear programming problem. The further effects of system average time constant, speed drop factor, load reduction ratio (load frequency sensitivity factor), system inertia, load shedding and spinning reserve are included. Furthermore a simple load distribution factor is considered in this algorithm. Results of the unified power system of lower Egypt have been presented to validate the algorithm and show its effectiveness. Copyright © 1999 John Wiley & Sons, Ltd.     

Probabilistic hydrogen,thermal and electrical management of PEM-fuel cell power plants in distribution networks

This paper presents a Stochastic Multi-objective Optimal Operation Management (SMOOM) framework of distribution networks in presence of PEM-Fuel Cell Power Plants (FCPPs) and boilers. Operational costs, thermal recovery, power trade with grid and hydrogen management strategies are considered in this model. Furthermore, four objective functions has been considered as criteria for SMOOM, i.e. electrical energy losses, voltages deviations from their nominal values, total emissions emitted by CHP systems and grids, and total operational costs of CHP systems, as well as electrical energy cost of grids. A 2m + 1 Point Estimated Method is used to cope with the uncertain variables i.e. electrical and thermal loads, gas price of FCPPs consumption, fuel cost of residential loads, purchasing and selling tariff of electricity, hydrogen price, operation temperature of fuel cell stack, and the pressures of hydrogen and oxygen of anode and cathode, respectively. A new multi-objective Modified Firefly Algorithm (MFA) is implemented for minimizing the objective functions while the operational constraints are satisfied. Finally, a 69-bus distribution network is utilized to examine the performance of the proposed strategy regarding the rest.     

从标准看智能电网的发展

目前世界各国在什么是智能电网、如何推进智能电网的发展等方面并没有达成一致意见。美国设想的未来电力系统是一个完全自动化的电力传输网络,能够保证从电厂到终端用户整个输配电过程中所有节点之间的信息和电能的双向流动。欧洲智能电网技术平台的目标是提高输配电系统的效率、安全性和可靠性,消除大规模集成配网与可再生能源的障碍。日本将主要以大规模开发太阳能等新能源、确保电网系统稳定作为智能电网建设的主要思路。结合中国的实际情况,我国智能电网业务框架应包含发电、输变电、配电、用户、运行、服务提供者、电力市场及统一信息平台等8个领域。现有标准与智能电网之间存在差距,主要体现在需求响应和电力市场、广域状态测量、电力存储、电力传输、AMI系统、配网管理等6个方面。其中,一部分差距已经有了清晰的发展方向和解决思路;而另一部分的具体发展方向和解决思路尚不明确。智能电网相关标准的开发需要以具体项目实施为载体,标准体系是否完备需要通过具体项目检验和修订,同时具体项目的顺利实施也有赖于标准体系的约束和规范。针对中国某省级电网的特殊性和典型性,建议其智能电网的发展,一是应重点关注标准研究方向,二是由此引出的示范工程项目。