电力系统暂态分析

电力系统暂态分析讲义PowerSystemTransientAnalysisLectureTeachingMaterial：《电力系统暂态分析》第二版，李光琦编ClassHour：51ApplyingClass：电气工程及其自动化专业2001级Teacher：杭乃善目录绪论············································································1第一章电力系统故障分析的基本知识·············································1第一节概述··························································1第二节标幺制························································1第三节无限大功率电源供电的三相短路分析·····························4第一章小结···························································7第二章同步发电机突然三相短路分析················································8第一节同步发电机突然三相短路的物理过程及短路电流近似分析············8第二节同步发电机的基本方程、参数和等值电路··························12第三节应用同步发电机基本方程（拉氏运算形式）分析突然三相短路电流···22第四节自动调节励磁装置对短路电流的影响·····························37第二章小结··························································37第三章三相短路的实用计算······················································41第一节周期电流起始值的计算·········································41第二节运算曲线法···················································46第三节计算机算法原理···············································47第四章对称分量法及元件的各序参数和等值电路····································48第一节对称分量法···················································48第二节在不对称故障分析中的应用·····································48第三节同步发电机的负序、零序电抗···································51第四节异步电机的正、负、零序电抗···································52第五节变压器的零序电抗和等值电路···································52第六节输电线路的零序阻抗和等值电路·································56第七节零序网络的构成···············································59第五章不对称短路的分析计算···················································60第一节不对称短路时故障处的短路电流和电压···························60第二节非故障处电流、电压的计算·····································65第六章稳定性问题概述和各元件的机电特性········································66第一节概述·························································66第二节同步发电机组的机电特性·······································67第三节自动调节励磁系统的原理和数学模型·····························73第六章小结·························································74第七章电力系统静态稳定························································75第一节简单系统的静态稳定··········································75第二节负荷的静态稳定··············································75第三节小干扰法分析简单系统的静态稳定······························75第四节自动调节励磁系统对静态稳定的影响····························77第五节提高静态稳定的措施··········································80第八章电力系统暂态稳定························································80第一节暂态稳定概述·················································80第二节简单系统的暂态稳定分析·······································80第三节自动调节系统对暂态稳定的影响································84第四节提高暂态稳定的措施··········································87复习·········································································87电力系统暂态分析讲义1绪论(Introduction)TransientAnalysis：暂态分析，瞬变、过渡、暂时物理特点：由一个状态（初始状态）变化到另一状态（终止状态）的过程分析，数学特点：用微分方程描述的过程分析。应用：电力系统设计、规划、控制等；第一章电力系统故障分析的基本知识第一节概述故障，事故，短路故障：正常运行情况以外的相与相之间或相与地之间的连接。1．故障类型（电力系统故障分析中）名称图示符号⑴三相短路f（3）f：fault⑵二相短路f（2）⑶单相短路接地f（1）⑷二相短路接地f（1。1）⑸一相断线⑹二相断线形式上又可称为短路故障、断线故障（非全相运行）分析方法上：不对称故障、对称故障（f（3））计算方法上：并联型故障、串联性故障简单故障：在电力系统中只发生一个故障。复杂故障：在电力系统中的不同地点（两处以上）同时发生不对称故障。第二节标幺制一标幺值(P.U.)标幺值=有名值基准值电力系统暂态分析讲义2二基准值的选取·基准值的选取有一定的随意性，工程中一般选择惯用值（SB=100MVA、SB=1000MVA、UB=UN）·三相电路中基准值的基本关系稳态分析：BBBIUS3，BBBZIU3其中：SB：三相功率UB：线电压IB：星形等值电路中的相电流ZB：单相阻抗短路分析中：ZB：单相阻抗---故障分析中的等值电路计算与稳态分析相同IB：星形等值电路中的相电流UB：相电压？三基准值改变时标幺值的计算已知以设备本身额定值为基准值的标幺值)*(Nx，求以系统基准值SB、UB为基准时的标幺值)*(Bx例如：已知US%，STN，求在系统基准容量SB时的标幺值电抗？100%)*(sNUx22)*(100%BBTNTNsBUSSUUxNBBNNBSSUUxx22)*()*(●额定容量SN小，则电抗x*（B）大，小机组、小变压器的电抗大；●简单网络计算中，选取SB=STN（SN），可减少参数的计算量。四．变压器联系的不同电压等级电网中元件参数标幺值的计算（一）准确计算法①选定SB、UB1②UB2=UB1*121/10.5③UB3=UB2*6.6/110作等值电路：jxG*jxT1jxLjxT2jxR22)*()*(BBGnGNNGBGUSSUxx取基准电压=额定电压，可简化计算222212*1121100%5.10100%BBTNsBBTNsTUSSUUSSUx变压器电抗可由任一侧计算~IIIIII10.5/121110/6.6电力系统暂态分析讲义322212*1215.10BBlBBlLUSlxUSlxx线路电抗就地处理更方便即，准确计算法有3种，⑴阻抗归算法；（阻抗按变压器实际变比归算，简单网络较方便）⑵就地处理法；（基准电压按变压器实际变比归算，大网络计算较方便）⑶在就地处理中，取定各段的基准电压（不一定按变压器实际变比作基准电压归算），则可出现1：k*的理想变压器，然后再将1：k*变压器用π形等值电路表示。（二）近似计算法●平均额定电压Uav=1.05UN,若取SB=100MVA，UB=UavUN61035110220500Uav6.310.537115230550ZBIB成为工程中惯用的基准值。●假定变压器的变比均为平均额定电压的变比，且取各段基准电压均为相应段的平均额定电压，此时的参数计算称为近似计算法，即有以下简单计算GnBNGBGSSxx)*()*(TNBTSSUsx100%*122*BBlLUSlxx电压越高，电抗越小（电抗与电压的平方成反比）习题1：一简单电力系统接线如下图所示，取SB=220MVA，UB（110）=115kV，试用精确法和近似法分别计算其等值电路。GT1lT2240MW300MVA230km280MVA10.5kV10.5/242kVx=0.42Ω/km220/121kVcosφ=0.80Us%=14Us%=1430.0'dx五f、ω、t的基准值fB=fN=50Hz(f*=1)ωB=2ωfB=100πNBBft211容量大，电抗小~电力系统暂态分析讲义4特点：当f=fN=50Hz时，可有x*=L*ψ*=I*x*E*=ψ*sinωt=sint*第三节无限大功率电源供电的三相短路分析●无限大电源：UG=常数、xG=0、ω=常数一暂态过程分析本书中的一些下标说明：|0|：故障前瞬间，相当“电路”中的0-0：故障后瞬间，相当“电路”中的0+p或ω：周期分量（period）、ω：频率为ω的分量α：非周期分量m：模值（mode）M：最大值（maximum）∞：稳态值（t→∞）无互感的三相电路如图1-4：P.11三相电源对称（模相同、相位差120°），三相电路对称（每相阻抗Z=R+jωL）,发生三相短路。称为对称短路。对称短路可仅取一相分析，其他两相有模相同、相位差120°的结果。单相等值电路：短路前：)sin(00tIima短路发生：一阶线性非齐次微分方程)sin(tURidtdiLmaa其解=特解+齐次方程的通解TatmmmaeIItIi)sin()sin()sin(00周期分量：ipa非周期分量：aiua=Umsin(ωt+α)RLR’L’ia电力系统暂态分析讲义50aiai在起点（t=0+）时刻)sin(0mpaIi)()sin(000mmaIIi即0000aapaaiiii结论：由apaaiii，短路电流由周期分量和非周期分量组成，