2012/11/211电力系统分析理论电力系统分析理论T THEORYHEORY OFOFP POWEROWERS SYSTEMYSTEMA ANALYSISNALYSIS李萍李萍1. 1.电压调整的电压调整的必要性必要性Essentiality Essentiality of voltage of voltage control/regulationcontrol/regulation2. 2. 无功平衡与电压水平的无功平衡与电压水平的关系关系Voltage levels and reactive power balanceVoltage levels and reactive power balance3. 3.电压调整的范围及电压调整的范围及方法方法The acceptable limits and methods of voltage controlThe acceptable limits and methods of voltage control4. 4. 发电机和发电机和变压器调变压器调压压Controlling voltage levels by generating units or tapControlling voltage levels by generating units or tap- -changing transformerschanging transformers5. 5. 无功功率无功功率补偿补偿Reactive power compensationReactive power compensation*6. *6. 电力系统无功功率的最优分配电力系统无功功率的最优分配optimal allocation of reactive poweroptimal allocation of reactive power第五章第五章 电力系统无功功率和电压调整电力系统无功功率和电压调整 Reactive power and voltage control Reactive power and voltage control 事故区域：美国加拿大东部互联系统所属东北 部电网 事故损失：负荷6180万千瓦，影响5000万人， 300亿美元美加大停电事故分析大停电概况美加大停电事故分析大停电概况200MW400-500MWVV2200MW200-2800MW图图5 5- -2 2“电压崩溃”现象“电压崩溃”现象5.1 5.1 电压调整的必要性电压调整的必要性 Essentiality Essentiality of voltage of voltage control/regulationcontrol/regulation再看美加大停电再看美加大停电U.S/Canada power outage/blackout august 14U.S/Canada power outage/blackout august 14，2003 2003 5.2 5.2 电力系统的无功功率平衡电力系统的无功功率平衡1. 1.无功负荷和无功无功负荷和无功损耗损耗Absorption of reactive powerAbsorption of reactive power2. 2.无功无功电源电源Production of reactive powerProduction of reactive power3. 3.无功无功平衡平衡The reactive power balanceThe reactive power balance4. 4.无功平衡与电压水平的关系无功平衡与电压水平的关系Voltage levels and reactive power balanceVoltage levels and reactive power balance1. 1.无功负荷和无功无功负荷和无功损耗损耗reactive power absorbed by equipmentsreactive power absorbed by equipmentsXIXVQQQmmM22 V sRI0ImjXjXQV07 . 08 . 09 . 00 . 18 . 06 . 03 . 0无功负荷无功负荷reactive power reactive power absorbed by loadsabsorbed by loads与电压与电压 成成正比正比与电压与电压 成成反比反比P PMM= =I I2 2R R(1 (1s s)/ )/s s= =常数常数V Vs sI I2012/11/212无功损耗无功损耗22 0220)(100% 100%)(VV SSVSIXVSBVQQQNNS NTTTLT(1) (1) 变压器变压器的无功损耗的无功损耗Reactive power absorbed by Reactive power absorbed by transformerstransformers与电压与电压 成成正比正比与电压与电压 成成反比反比(2) (2) 线路线路的无功的无功损耗损耗Reactive power Reactive power lossloss of transmission linesof transmission linesAbsorptionAbsorption and and production production of reactive power on of reactive power on transmission linestransmission lines2Bj 2Bj1V2V11jQP 22jQP jXRXVQPXVQPQL2 22 22 2 2 12 12 1)(22 22 1VVBQBBVVXVQPQQBL22 22 1 2 12 12 12. 2. 无功电源无功电源发电机发电机Synchronous generators Synchronous generators can generate or absorb reactive can generate or absorb reactive power depending on the power depending on the excitation.excitation.NGNNGNGNtgPSQsin过励磁过励磁 提供无功提供无功supply reactive powersupply reactive power欠励磁欠励磁 吸收无功吸收无功absorb reactive power absorb reactive power NGNNGNGNtgPSQsinNNVAGNQQPC EGNPNENVdjXNINdIjXP P- -Q Q极限极限发电机发电机 无功无功输出限制输出限制 reactive capability limitsreactive capability limitsNI其它无功其它无功电源电源Other source of reactive powerOther source of reactive power同步调相机同步调相机synchronous condensersynchronous condenserOverexcitedOverexcited- -supply reactive powersupply reactive powerUnderexcitedUnderexcited- - absorb reactive powerabsorb reactive power静电电容器静电电容器capacitorscapacitors静止补偿器静止补偿器SVCSVC-Static Static varvar compensatorscompensators图图5 5- -6 6 静止无功补偿器的原理图静止无功补偿器的原理图(a)(a)可控饱和电抗器型；可控饱和电抗器型；(b)(b)自饱和电抗器型；自饱和电抗器型；(c)(c)可控硅控制电抗器型；可控硅控制电抗器型；(d) (d) 可控硅控制电抗器和可控硅投切电容器组合型可控硅控制电抗器和可控硅投切电容器组合型2012/11/2133. 3.无功无功平衡平衡 the reactive power balancethe reactive power balanceresLLDGCQQQQ无 功 电 源无 功 负 荷无 功 损 耗无 功 备 用Q Qr re es s0 0 无功可以平衡无功可以平衡, ,且且 有备用有备用Q Qresres0 0 无功不足无功不足, ,应加补应加补 偿装臵偿装臵321CCCGCGGC QQQQQQQBlTLQQQQ4. 4.无功平衡与电压水平的关系无功平衡与电压水平的关系 Voltage levels and reactive power balanceVoltage levels and reactive power balanceThe control voltage levels is accomplished by The control voltage levels is accomplished by controlling the controlling the production, absorption production, absorption and and flow flow of of reactive power.reactive power.XV XEVVIQXEVVIP2 cossinsincosjXVIP+jQPLD+jQLDEsincosEXIEI VsinEcosXI jXIVEXIcossinVoltage levels and reactive power balanceVoltage levels and reactive power balanceXVPXEVQ2 22)(2VVaVaac1jXVIP+jQPLD+jQLDEQ2140X PjQ1V2VLDLDPjQ22 0110)(VQQLD XVPXEVQ2 2222 )(例例5 5- -1 1 某输电系统的等值电路如图所示，已知电压某输电系统的等值电路如图所示，已知电压 V V1 1=115kv=115kv维持不变，负荷有功功率维持不变，负荷有功功率P PLDLD=40MW=40MW保持恒定，无保持恒定，无 功功率与电压平方成正比，即功功率与电压平方成正比，即求求Q Q0 0=20Mvar=20Mvar和和Q Q0 0=30Mvar=30Mvar两种情况按无功功率平衡的条两种情况按无功功率平衡的条 件确定节点件确定节点2 2的电压的电压V V2 2。22 0110)(VQQLD （1 1）用式）用式5 5- -1414计算线路送到负荷节点的无功功率计算线路送到负荷节点的无功功率2 222 22 22222 22220250160026568404040115VVVV XVPXEVQ.)()( （2 2）求得无功电源和无功负荷的电压静特性）求得无功电源和无功负荷的电压静特性 （3 3）找到）找到Q Q- -V V曲线分别与曲线分别与 Q QLD(1)LD(1)和和Q QLD(2)LD(2)的交点，求的交点，求 得对应两种负荷情况下的电压得对应两种负荷情况下的电压V V2 22012/11/214MvarQkVV3025201510102104106108110LD-1( )QV