计及风电与电动汽车随机性的两阶段机组组合研究

风电出力的随机性以及电动汽车(electric vehicle,EV)充电需求的不确定性给电力系统调度带来了挑战。在传统确定性机组组合模型的基础上,针对电力系统日前调度面临的不确定问题,提出了充分考虑风电与电动汽车双重不确定性的随机优化调度及备用计算模型。首先,对于风电出力不确定性,采用基于场景分析的两阶段随机优化方法,并使用生成对抗网络(generative adversarial network, GAN)来生成风电场景。其次,对于电动汽车充电需求的不确定性,将其分为可调度与不可调度两类。可调度电动汽车根据其出行规律采用随机模拟的方法,并建立了EV充电聚集商模型;不可调度电动汽车通过K-means聚类分析得到其典型负荷曲线,并将其并入系统常规负荷中。最终建立了基于多场景分析考虑EV充电聚集商的两阶段随机机组组合模型,并通过算例分析证明了所提模型的有效性。     

配电系统中电动汽车与可再生能源的随机协同调度

电动汽车和可再生能源发电的快速发展为电力系统的安全和经济运行带来了新的挑战。在此背景下,构建了能够计及可入网混合动力电动汽车(PHEV)和风电、光伏发电系统出力不确定性的随机协同优化调度模型。首先,分析了PHEV的行驶耗电和随机充放电行为。之后,在假设风速服从Rayleigh分布、光照服从Beta分布的前提下,导出了风电机组和光伏发电系统出力的期望、方差及二阶原点矩的表达式。在此基础上,发展了以平抑可再生能源出力波动为目标的电力系统随机协同优化调度模型,并应用交叉熵算法进行求解。最后,以33节点配电系统为例说明了所提出的随机协同优化调度模型的基本特征。     

考虑电动汽车入网技术的电力系统机组组合研究

为了提高电动汽车入网技术（V2G）的电力系统机组组合实用性和经济性,提出一种考虑可入网电动汽车（PEV）的数量变化和电池电荷状态变化的机组组合算法。利用电池电荷状态与充放电电量之间的关系,结合预估的不同时段入网PEV数量,确定每天入网PEV的净充电总需求量。构建考虑电动汽车入网技术的电力系统机组组合模型,以发电成本为目标函数,加入电池电荷状态的罚函数,求解电力系统机组的出力计划和入网PEV的充放电控制计划。分析了不同情景下充放电最优控制和机组组合结果,对比了不同PEV充电模式对电力系统机组组合结果的影响。算例分析结果表明,该方法可以有效的节省机组成本,实现电动汽车的连续调度,证明了该方法的正确性和有效性。     

考虑风电与电动汽车协同作用的动态环境经济调度

针对风电与规模化电动汽车入网给电力调度带来的挑战,建立了基于动态约束处理的风电与电动汽车协同作用的环境经济模糊决策调度优化模型。该模型包含风电机组和入网的电动汽车(vehicle to grid,V2G),以同时降低燃料成本和减少污染排放量为优化目标,在满足系统功率平衡和车主日常出行需求等约束条件下,通过动态调节电动汽车充放电功率和时间来最大限度地消纳过剩风电,平抑风能出力波动对电力系统的冲击;接着对常规机组进行负荷经济分配,以达到协同优化调度的经济性;同时采用多目标纵横交叉优化算法(multi-objective crisscross optimization algorithm,MOSCO)优化算法求解模型,利用模糊决策机制获得最优折中解;最后以10台机组测试系统为算例,仿真结果验证了模型及方法的有效性与合理性。     

计及电动汽车不确定性的虚拟电厂参与AGC调频服务研究EI北大核心CSCD

电动汽车用户出行和响应的不确定性,为调度电动汽车参与自动发电控制(automaticgenerationcontrol,AGC)带来了挑战。基于此,采用经验模态分解法将火电机组调频偏差分解为高频、中频和低频部分,作为超级电容器、蓄电池以及可入网电动汽车(plug-in electric vehicle,PEV)的参考出力功率。建立了基于韦伯-费希纳定律的PEV用户响应模型,并引入PEV响应偏差阈值的概念,实现PEV赔偿风险—收益之间的平衡。以AGC调频效果最好及净收益期望最高为目标,建立含火电机组、混合储能系统及PEV的虚拟电厂参与AGC调频决策模型,采用改进的遗传算法对混合储能系统进行优化配置并优化调度虚拟电厂各部分的出力,制定了各时段PEV充放电补偿电价。算例结果表明,该模型能够显著提高AGC调频效果,且通过合理设置PEV响应偏差阈值,能最大化净收益期望值。     

计及电动汽车不确定性的虚拟电厂参与AGC调频服务研究

电动汽车用户出行和响应的不确定性,为调度电动汽车参与自动发电控制(automaticgenerationcontrol,AGC)带来了挑战。基于此,采用经验模态分解法将火电机组调频偏差分解为高频、中频和低频部分,作为超级电容器、蓄电池以及可入网电动汽车(plug-in electric vehicle,PEV)的参考出力功率。建立了基于韦伯-费希纳定律的PEV用户响应模型,并引入PEV响应偏差阈值的概念,实现PEV赔偿风险—收益之间的平衡。以AGC调频效果最好及净收益期望最高为目标,建立含火电机组、混合储能系统及PEV的虚拟电厂参与AGC调频决策模型,采用改进的遗传算法对混合储能系统进行优化配置并优化调度虚拟电厂各部分的出力,制定了各时段PEV充放电补偿电价。算例结果表明,该模型能够显著提高AGC调频效果,且通过合理设置PEV响应偏差阈值,能最大化净收益期望值。     

计及电动汽车的风水火电力系统联合优化调度

充分考虑了电动汽车充电的不确定性,以实测数据为基础,通过充电起始时间和持续时间,得到电动汽车充电概率的时间分布。针对风电出力和负荷预测的波动性等特点,将风电出力和负荷预测的不确定性表示为一个具有零均值、呈正态分布的预测误差。由此构建了风水火电力系统联合调度模型,调度模型以系统成本最小为目标函数,包含了火电机组煤耗成本、水电站管理成本以及风电场管理成本和预测误差成本,最后采用布谷鸟搜索算法对其进行求解。仿真结果表明,水电站能够在电力系统中发挥较好的调节作用,弥补风电出力的随机波动和电动汽车的无序充电,减少火电机组出力的频繁变化,降低系统备用容量,增加电力系统的安全性、稳定性和供电可靠性。     

含随机风电出力及电网安全的电网调度策略研究

随着风电基地在中国北部和沿海地区大力建设,风电在电网中的比例不断提高,这对电力系统的经济调度运行提出新的考验。特别是风电的间歇性和波动性使得经济调度具有更多不确定性。将风速的概率模型和风机出力相结合,利用风电场出力的概率分布函数将风电场出力的随机模型转化为确定性模型,构建以机组的发电成本最小为目标函数,同时计及电网网络安全约束。在优化算法上,利用量子行为粒子群算法对模型进行求解,最后对调度模型进行敏感性分析。仿真结果表明,所提模型和方法是可行、有效的,具有一定的实用价值。     

含风电的电力系统月度机组组合和检修计划联合优化调度

恰当考虑风电出力的随机性和相关性,进行含风电的电力系统月度机组组合和检修计划联合调度,对于提高风电的接纳能力和系统中期运行的可靠性和经济性都具有重要的意义。根据风速历史数据统计得到风电出力的月度概率分布,构建基于机会约束规划的月度机组组合和检修计划联合调度随机模型,并给出随机模型的确定化转换方法。为实现机组发电调度和检修计划的联合优化,模型中引入了检修费用及检修相关约束,并针对机组组合和检修计划之间的耦合关系,设置相关时段索引变量,建立相互之间的关联矩阵。利用混合整数线性规划法对模型进行求解。通过118节点系统的仿真计算,验证所提模型的合理性和方法的有效性。     

含风电系统的有功和备用协调优化方法

针对风电的随机性、波动性分析应对风电功率预测误差和风电功率波动所需的备用容量,并根据风电功率预测误差概率分布和风电功率波动概率分布建立风电备用需求与风电出力之间的关系,提出了风电备用需求新模型。在此基础上,构建了含风电系统的有功和备用协调优化调度模型,将系统备用容量需求分解为快速备用和事故备用两部分,在得到机组最优出力计划的同时,实现2类备用容量在机组间的优化分配。通过对修订后的IEEE 6节点和IEEE 118节点系统进行仿真计算,验证了所提模型和方法的合理性和有效性。     

Fuzzy Reliability Assessment of Distribution System with Wind Farms and Plug-in Electric Vehicles

Abstract

The equipment failures are highly uncertain in nature and simple average failure rate will not reflect this uncertainty. The uncertainty level further increases in reliability evaluation due to the integration of wind farm (WF) because of the intermittent nature of wind speed and random charging patterns of plug-in electric vehicles (PEVs). In this work, the uncertain variables in the distribution system (failure rate, repair time, WF output, PEVs charging and system load factor) are represented as fuzzy numbers to handle the uncertainty. The available uncertain data are used to find the probability distribution function (PDF) of that parameter and is converted into fuzzy membership function using transformation techniques. Failure rate of equipment is converted into failure probability using Monte Carlo simulation (MCS) method. Sampling method is applied to create the PDF of a variable which has average value. Fuzzy severity index (FSI) is proposed to find the importance of an equipment on reliability and is evaluated by measuring the fuzzy distance between the fuzzy reliability indices. The proposed assessment method is validated on modified RBTS bus 2 by comparing with analytical and MCS methods. The proposed method has been tested with integration of WFs and PEVs.     

An adaptive supervised wide-area backupprotection scheme for transmission linesprotection

Background: The increasing penetration of a massive number of plug-in electric vehicles (PEVs) and distributed generators (DGs) into current power distribution networks imposes obvious challenges on power distribution network operation. Methods: This paper presents an optimal temporal-spatial scheduling strategy of PEV charging demand in the presence of DGs. The solution is designed to ensure the reliable and secure operation of the active power distribution networks, the randomness introduced by PEVs and DGs can be managed through the appropriate scheduling of the PEV charging demand, as the PEVs can be considered as mobile energy storage units. Results: As a result, the charging demands of PEVs are optimally scheduled temporally and spatially, which can improve the DG utilization efficiency as well as reduce the charging cost under real-time pricing (RTP). Conclusions: The proposed scheduling strategy is evaluated through a series of simulations and the numerical results demonstrate the effectiveness and the benefits of the proposed solution.     

A fast time-frequency response baseddifferential spectral energy protection ofAC microgrids including fault location

Background: The increasing penetration of a massive number of plug-in electric vehicles (PEVs) and distributed generators (DGs) into current power distribution networks imposes obvious challenges on power distribution network operation. Methods: This paper presents an optimal temporal-spatial scheduling strategy of PEV charging demand in the presence of DGs. The solution is designed to ensure the reliable and secure operation of the active power distribution networks, the randomness introduced by PEVs and DGs can be managed through the appropriate scheduling of the PEV charging demand, as the PEVs can be considered as mobile energy storage units. Results: As a result, the charging demands of PEVs are optimally scheduled temporally and spatially, which can improve the DG utilization efficiency as well as reduce the charging cost under real-time pricing (RTP). Conclusions: The proposed scheduling strategy is evaluated through a series of simulations and the numerical results demonstrate the effectiveness and the benefits of the proposed solution.     

含风电机组的配网无功优化

研究了分布式电源中发展较为成熟的风力发电机组并网后配电网的无功优化问题，提出一种基于场景发生概率的无功优化综合指标，该指标由网损和静态电压稳定裕度两部分构成。基于该指标，提出一种新的无功优化模型。在该模型中，提出风电机组输出功率典型场景的选取策略，无功优化潮流计算中考虑了风电机组的特点，将其作为电压静特性节点处理。在求解方法上，采用基于自适应权重的遗传算法求解。算例表明，提出的模型和算法是可行的，对风电系统的运行具有一定的参考价值。     

考虑风电波动性的微网中电动汽车分布式协调运行方法

随着风力发电的快速发展,间歇性风电引起的电网功率波动问题日益凸显,而通过制定插入式电动汽车（plug-in electric vehicles, PEVs）的合理充放电策略,可为平衡功率波动和调节系统频率提供有效支撑。文章针对含风电的微网功率波动问题,提出了基于电动汽车参与意愿度和效用函数最大的PEVs协调运行模型,并基于一致性理论设计了PEVs分布式充放电控制方法。所提方法以完全分布式方式最优调整PEVs充放电功率,可有效平抑风电功率波动,并能满足PEVs日常多种充电场景需求,包括PEVs随机到达时间和启程时间、电池荷电状态随机初始值和目标值。最后通过含有5个风电场和2 000台PEVs的微网进行验证,仿真结果表明所提PEVs协调运行模型和分布式控制方法可灵活满足规模化PEVs的充放电需求,并可有效改善微网系统的频率响应特性。     

Evaluation of Probability Distributions of Distribution System Reliability Indices Considering WTG as Alternative Supply

Using wind turbine generators (WTG) as an alternative supply in a rural distribution system will affect both the mean values and the probability distributions of system reliability indices due to the fluctuating characteristics of wind speed. This paper investigates the impacts on the reliability indices and their probability distributions of using WTG as an alternative supply. A time sequential simulation technique is used to simulate the time-varying nature of wind speed and the random failure of system elements. The probability distributions of basic load point and system reliability indices for a modified rural distribution system are presented. The effects of WTG parameters on the index probability distributions are discussed.     

Stochastic optimal power flow incorporating offshore wind farm and electric vehicles

In this paper, an optimal power flow model of a power system, which includes an offshore wind farm and plug-in electric vehicles (PEVs) connected to grid, is presented. The stochastic nature of wind power and the uncertainties in the EV owner’s behavior are suitably modelled by statistical models available in recent literatures. The offshore wind farms are assumed to be composed of doubly fed induction generators (DFIGs) having reactive power control capability and are connected to offshore grid by HVDC link. In order to obtain the optimal active power schedules of different energy sources, an optimization problem is solved by applying recently introduced Gbest guided artificial bee colony algorithm (GABC). The accuracy of proposed approach has been tested by implementing AC–DC optimal power flow on modified IEEE 5-bus, IEEE 9-bus, and IEEE 39-bus systems. The results obtained by GABC algorithm are compared with the results available in literatures. This paper also includes AC–DC optimal power flow model, implemented on modified IEEE-30 bus test system by including wind farm power and V2G source. It has been shown that the uncertainty associated with availability of power from wind farm and PEVs affects the overall cost of operation of system.     

基于概率潮流的风电分布式电源优化配置

由于风电机组输出功率的随机波动性,使得基于风电机组的分布式电源并网后,给配电系统的结构和运行带来巨大变化,影响系统的安全性和可靠性。在含分布式电源的配电网系统规划中,对分布式电源进行合理选择和配置是发挥最大效益的关键。采用Weibull分布来描述风速的随机变化,并计及风电机组强迫停机率的影响,结合功率曲线,建立风力发电的概率分析模型。通过Cornish-Fisher级数交流概率潮流计算方法,分析风电和负荷的随机波动对含分布式电源配电系统的影响,利用混合整数非线性规划方法,确定风电系统的最佳接入点和注入容量使得系统有功网损最小。     

风电电动汽车协同利用对电网风电接纳能力的影响

建立包含电动汽车充、放、耗电约束的风电电动汽车协同利用模型,根据决策变量的不同将充放电模式分为自由充电、不含V2G(Vehicle to grid)和含有V2G的风电电动汽车协同利用。以风电利用率和风电在电网能源结构中电量占比作为衡量水平,分析不同充电模式、电动汽车数量和风电装机容量下的风电接纳能力。含有V2G的风电电动汽车协同利用能够最大限度提高电网风电接纳能力,且在风电装机容量较大时更能显示出含有V2G的协同利用充放电模式的优势,含有V2G的风电电动汽车协同利用是实现大规模风电并网的有效方式,同时一定负荷和风电装机水平的电网存在一个最佳匹配的电动汽车数量。     

Economic analysis of unit commitment with distributed energy resources

Classic unit commitment (UC) is an important and exciting task of distributing generated power among the committed units subject to several constraints over a scheduled time horizon to obtain the minimum generation cost. Large integration of distributed energy resources (DERs) in modern power system makes generation planning more complex. This paper presents the individual and collective impact of three distributed energy resources (DERs), namely, wind power generator as a renewable energy source, plug-in electric vehicles (PEVs) and emergency demand response program (EDRP) on unit commitment. In this paper, an inconsistent nature of wind speed and wind power is characterized by the Weibull probability distribution function considering overestimation and underestimation cost model of the stochastic wind power. The extensive economic analysis of UC with DERs is carried out to attain the least total cost of the entire system. To obtain the optimum solution, Teaching–learning based optimization (TLBO) algorithm is employed to solve the unit commitment problem considering IEEE standard 10 unit test system in this study. It is found that the combined effect of wind power generator, plug-in electric vehicles and emergency demand response program on UC significantly lessen the total cost of the system.