电力系统风险评估.ppt

电力系统风险评估绪论12什么叫风险？电力系统中存在哪些风险？大规模风电入网给电力系统带来哪些风险？教材及参考文献：1.电力系统风险评估模型、方法和应用李文沅著2.郭永基电力系统可靠性分析3.静铁岩，大规模风电并网条件下的电力系统有功功率平衡理论研究，博士论文第一章绪论部分。4.张丽英，叶廷路等，大规模风电接入电网的相关问题及措施.中国电机工程学报.Vol.30(25)，201031.1 电力系统中的风险风险和可靠性的关系描述同一个事实的两个方面：更高的风险即更低的可靠性本课程的目的：讨论电力系统风险评估的模型、方法及其工程应用电力系统风险的根源：设备的随机故障，负荷的波动，市场环境下多变的市场需求及市场参与者的行为，可间歇性能源入网。4风险管理包括：实施风险的定量评估：建立表征系统风险的指标确定降低风险的措施：意味着投资确认可接受的风险水平：对技术、经济、社会以及环境等因素进行综合评估5电力系统风险评估适用的领域：发、输、配系统的规划电源规划运行风险评估设备维修设备备用分析变电站接线分析输电服务。61.2 电力系统风险评估的基本概念风险=事件发生的概率 X 事件发生带来的损失系统风险评估步骤确定元件停运模型（第二章）选择系统状态，计算发生的概率（两种方法）评估所选择状态的后果（可能是简单的功率平衡分析，网络结构连通性分析，优化潮流，电压稳定分析）计算风险指标（指标的概率分布，随机变量的期望值）7元件停运模型参数由元件停运统计数据计算得到；数据的预处理问题数据的动态特性8评估所选系统状态的后果由评估分类决定具体的运算充裕性分析：表明系统设施是否能充分满足用户的负荷需求和系统运行的约束条件，只涉及到系统的稳态条件，不要求动态和暂态分析。安全性分析：系统对动态和暂态扰动的响应能力。因此通常要进行动态、暂态或电压稳定性分析。基于历史停运统计数据的评估9风险指标反应停电规模，电压的变化或均值，潮流的变化或均值等单位停电损失基于用户损失函数的方法；基于投资核算的方法；基于国民生产总值的方法；10第二章 系统元件的停运模型11可修复强迫失效Component two-state model:Failure rate:Repair rate:Failure rate and repair rate:from statistics of the target component.For example:12Availability A:Mean Time To Failure(MTTF):Mean Time To Repair(MTTR):Unavailability U:Failure frequency f:Mean Time Between Failure(MTBF):MTBF=MTTF+MTTR 13Example:Statistics of a 200MW generator:14The reliability of a system:depends on the reliability of the components involved,and systems topologySeries connected system:15Example:A simple power supply system:the availability of each component is:generator A1=0.990099,transformer A2=0.999933,busbar A3=0.999965,circuit breaker A4=0.999833,transmission line A5=0.999334.what is the availability of the whole system?16Parallel connected system:only when all components fail,the system fails.(a)Parallel connected system(b)Equivalent system17Example:Two transformers are in parallel operation.Statistics are:What is the failure rate of this parallel connected system and the MTTF of the system?18Integrated system:break down into series connected subsystem and parallel connected subsystem19ExampleA:power supply bus;C:load point.Suppose busbar A is always available.Question:what is the failure rate of point C and the total down time;What is the reliability of point cComponent Failure rateRepair rateComponent Failure rateRepair rateL10.57.5L30.17.5L20.57.5L40.67.5Parallel connected 1 series connected 2 Parallel connected 320Parallel connected 1:L1/L2 Series connected 2:L12+L321Parallel connected 3:L123/L422Unavailability:Total down time at busbar C:Reliability at busbar C:23作业：Matlab编程，实现可修复强迫失效相关计算。24计划停运25最简单的蒙特卡洛仿真流程随机生产模拟：元件的投入状态，负荷的随机变化，间歇性电源出力变化26考虑连锁故障的Monte Carlo 仿真流程对系统进行抽样27元件的失效模型参考文献考虑保护的隐性故障 J.Chen,J.S.Thorp,I.Dobson.Cascading dynamics and mitigation assessment in power system disturbances via a hidden failure model.International Journal of Electrical Power and Energy Systems.2005,27:318-326考虑天气变化对导体散热影响 M.Anghel,K.A.Werley,A.E.Motter.Stochastic model for power grid dynamics.The 40th HICSS.2007环境相依失效 卢锦玲，朱永利.基于暂态能量裕度的电力系统脆弱性评估.电工技术学报，2010，25(6)：96-103（看2.1节）28保护的隐性故障当有线路断开时，与此线路两端相连的所有线路的保护均存在发生隐性故障的可能。仅考虑单重隐性故障。29考虑天气变化对导体散热影响随机线路故障模型线路l上发生的随机故障由泊松过程描述。即在时间段t中发生的故障的次数服从泊松分布，均值为30风功率波动建模Wind Turbine Generator ModelingP(SWt):wind turbine outputSWt:Wind speedVci:cut-in wind speedVr:rated speedVco:cut-out speed31P-W characteristic established for 1.5-MW doubly-fed(continuous)and 1.5-MW fixed speed asynchronous wind generators(dotted).32Wind speed modeling:Drawing of an uniformly distributed number u on the interval 0,1;Application of that drawn random number u to the Weibull Cumulative Distribution Function F(W,A,B)in order to determine the associated wind speed W.Note:Cumulative Distribution Function:p(x X)33序贯蒙特卡洛仿真状态时间抽样法第1步：指定所有元件的初始状态（一般假定均处于运行状态）第2步：对每一元件停留在当前状态的持续时间进行抽样。第3步：在所研究的时间跨度内重复第2步，并记录所有元件的每一状态持续时间的抽样值，获得给定时间跨度内每一元件的随机状态转移过程。第4步：组合所有元件的状态转移过程，建立系统时序状态转移循环过程。第5步：对每一个不同系统状态进行系统分析，计算风险指标函数。34负荷的处理负荷保持不变年负荷曲线35年负荷曲线，并考虑随机变化36负荷分区、增长及随机波动假设在蒙特卡罗仿真的每一个循环内，负荷为该循环的平均负荷与某一随机变化量的叠加，且在该循环中保持不变。所有负荷节点按其所处位置划分为NF个区域，处于同一区域的负荷变化幅度相同，不同区域之间负荷的变化幅度不同。代表平均负荷的增长速度，略大于1，可设定。随机因子r在区间 上变化。则对于给定的 ，所引入的负荷波动系数为 。第t+1循环的平均负荷缓慢的负荷增长37P98 负荷曲线模型多级负荷水平模型将各个母线符合按其遵循的不同负荷曲线分类为相同的母线组。每个母线组有其使用的负荷持续曲线。使用聚类技术选择聚类均值Mij的初值，i代表聚类，j代表曲线j利用下式计算每小时负荷点至每个聚类均值的欧拉距离38负荷点分配到最近的聚类，重新编组，并利用下式计算新的聚类均值重复第2步和第3步，直到全部聚类均值在迭代中保持不变为止。使用收敛后的聚类均值Mij作为多级负荷模型中每一曲线每一聚类的负荷水平。39故障分析基于交流潮流的最优潮流模型目标函数：社会效益最大化（等效成发电费用最小），切负荷量最小，网损最小。约束条件：等式约束：功率平衡不等式约束：运行极限4041期望却供电量(EENS)NL:various load levelsTi:the no.of hours that system has the ith load levelC(s):load shed of state sn(s s):the no.of runs that system has a load shed of C(s)Ni:the total no.of runs in the simulation Fi:under the ith load level,the set of runs that have non-zero load shed.42EENS：其中 S 导致切负荷的系统状态集合,Ci 是状态 i下，系统的切负荷量,ti 是系统状态i的蒙特卡洛循环次数,T是蒙特卡洛总的循环次数.43负荷削减频率n(s)：抽样中S状态的发生数；Fi是多级负荷模型中，第i级负荷水平下系统失效状态的集合；Ti是第i负荷水平的时间长度h；T是负荷曲线的总时间区间h；NL是负荷水平分级数44Average line flow limit PerMW served:it is used to show the efficiency of the investment.where Pd(t)is the average load demand of the test system at the tth simulation run.NLine is the no.of transmission lines in the system.Fjmax(t)is the transmission capacity limit of line j at the tth simulation run.The average line flow limit per MW served is used as a measure of grid utilization.Since the grid investment is related to the maximum line flow limits and the societal benefit is related to the power served,the average lineflow limit per MW served is one way to indicate the ratio of societal benefit to the grid investment.45参考文献R.Billionton,and W.Wangdee,“Reliability-based Transmission Reinforcement Planning Associated with Large-scale Wind Farms”,IEEE Trans.on Power Systems,Vol.22,No.1,Feb.2007.6.4例16.5例246指标简介Basic adequacy indicesLOLP:失负荷概率(of an electric power system),the probability of all the outage events leaving the system with an available capacity lower than expected load Lo.47LOLE:the loss of load expectation.Widely accepted LOLE risk criterion:“one day in ten years”Ok:the magnitude of the k-th outage in the systempk:the probability of a capacity outage of magnitude Ok.tk:the number of days that an outage of magnitude Ok would cause a loss of load in the systemdaily peak load curve48Loss of Energy Expectation:the ratio of expected non-served energy to total energy demand over a period of time.Ek is the energy not supplied due to a capacity outage Ok;E is the total energy during the period of time.49期望负荷削减频率50Probability of load curtailment PLCP(s):probability of state sFi:the set of all states under load level i with non-zero load shed.T:total hours of the simulation period,generally a year51Cost per kilowatt-hour:We only consider the cost of transmission upgrades,not the cost of construction of new lines for the connection of wind farms to the transmission system.where Cwi is the cost per kilowatt-hour for wind injection.I is the capital investment of upgraded transmission lines;Ccost is the annually O&M cost of the transmission lines;Pe is the installed capacity of wind farm;Teq is the equivalent full-load utilization hours;r is the discount rate.n is the useful lifetime.52Network Equilibrium Entropy：entropy is then defined as in the following:where nb is the no.of lines in the system.Neglecting the short-run variability of wind power,we treat wind generator as an traditional generator in entropy computation when doing optimal power flow.Their outputs are scaled by their capacity factor.53