单机等值系统调速器死区对频率振荡的影响
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摘要
实际系统中多次发生一次调频过程不稳定导致的超低频频率振荡事件。调速器死区给系统带来非线性,进而影响系统的频率振荡行为。基于单机等值系统,采用描述函数法分析了无阶跃死区、有阶跃死区和滞环死区这3种死区对频率振荡的影响。在复平面上,给出了死区描述函数的负倒数随振幅变化的轨迹,以及调速器、原动机、发电机构成的开环传递函数随频率变化的曲线,两者相对位置关系决定系统的稳定性。负倒数随振幅变化特性曲线完全位于开环频率特性曲线左侧时,系统稳定。其他情况下2条曲线一般会相交,交点对应极限环,极限环稳定与否决定于交点的具体形态。同时分析了单机等值系统中调速器死区对频率振荡的影响,调速器无阶跃死区和有阶跃死区都不会减弱系统稳定性,但有滞环死区时可能导致原本稳定的系统出现稳定极限环引发的持续等幅振荡。时域仿真结果验证了上述结论。
Ultra-low-frequency oscillations caused by the instability of primary frequency regulation process occurr in actual power systems.Governor deadband introduces nonlinearity to the system and affects frequency oscillation.The influence of nonstep deadband,step deadband and hysterisis deadband on frequency oscillation are analyzed with the describing function method in the single-machine equivalent system.The locus of minus reciprocal of the describing function of deadband with oscillation amplitude,and the locus of open-loop transfer function with oscillation frequency are plotted on the complex plane.The relative location of the two loci determines the system stability.When the minus reciprocal locus entirely locates on the left of the open loop frequency characteristic locus,the system is stable.In other cases,the two loci intersect in general and the intersections correspond to limit cycles,and the stability is determined by the specific situation of the intersection.Furthermore,the influence of governor deadband on frequency oscillation in single machine equivalent system is analyzed.Non-step deadband and step deadband do not weaken the stability of the system,but hysterisis deadband may cause continuous oscillation due to stable limit cycle in a system which is initially stable without deadband.Results of time-domain simulations validate the conclusions.
Ultra-low-frequency oscillations caused by the instability of primary frequency regulation process occurr in actual power systems.Governor deadband introduces nonlinearity to the system and affects frequency oscillation.The influence of nonstep deadband,step deadband and hysterisis deadband on frequency oscillation are analyzed with the describing function method in the single-machine equivalent system.The locus of minus reciprocal of the describing function of deadband with oscillation amplitude,and the locus of open-loop transfer function with oscillation frequency are plotted on the complex plane.The relative location of the two loci determines the system stability.When the minus reciprocal locus entirely locates on the left of the open loop frequency characteristic locus,the system is stable.In other cases,the two loci intersect in general and the intersections correspond to limit cycles,and the stability is determined by the specific situation of the intersection.Furthermore,the influence of governor deadband on frequency oscillation in single machine equivalent system is analyzed.Non-step deadband and step deadband do not weaken the stability of the system,but hysterisis deadband may cause continuous oscillation due to stable limit cycle in a system which is initially stable without deadband.Results of time-domain simulations validate the conclusions.
引文
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[2] PICO H V, MCCALLEY J D, ANGEL A, et al. Analysis of very low frequency oscillations in hydro-dominant power systems using multi-unit modeling[J]. IEEE Transactions on Power Systems, 2012, 27(4): 1906-1915.
[3] 陈亦平,程哲,张昆,等.高压直流输电系统孤岛运行调频策略[J].中国电机工程学报,2013,33(4):96-102.CHEN Yiping, CHENG Zhe, ZHANG Kun, et al. Frequency regulation strategy for islanding operation of HVDC[J]. Proceedings of the CSEE, 2013, 33(4): 96-102.
[4] 贺静波,张剑云,李明节,等.直流孤岛系统调速器稳定问题的频域分析与控制方法[J].中国电机工程学报,2013,33(16):137-143.HE Jingbo, ZHANG Jianyun, LI Mingjie, et al. Frequency domain analysis and control for governor stability problem in islanded HVDC sending systems[J]. Proceedings of the CSEE, 2013, 33(16): 137-143.
[5] 刘春晓,张俊峰,陈亦平,等.异步联网方式下云南电网超低频振荡的机理分析与仿真[J].南方电网技术,2016,10(7):29-34.LIU Chunxiao, ZHANG Junfeng, CHEN Yiping, et al. Mechanism analysis and simulation on ultra-low frequency oscillation of Yunnan power grid in asynchronous interconnection mode[J]. Southern Power System Technology, 2016, 10(7): 29-34.
[6] 张建新,刘春晓,陈亦平,等.异步联网方式下云南电网超低频振荡的抑制措施与试验[J].南方电网技术,2016,10(7):35-39.ZHANG Jianxin, LIU Chunxiao, CHEN Yiping, et al. Countermeasures and experiments on ultra-low frequency oscillation of Yunnan power grid in asynchronous interconnection mode[J]. Southern Power System Technology, 2016, 10(7): 35-39.
[7] 路晓敏,陈磊,陈亦平,等.电力系统一次调频过程的超低频振荡分析[J].电力系统自动化,2017,41(16):64-70.DOI:10.7500/AEPS20161208002.LU Xiaomin, CHEN Lei, CHEN Yiping, et al. Ultra-low-frequency oscillation of power system primary frequency regulation[J]. Automation of Electric Power Systems, 2017, 41(16): 64-70. DOI: 10.7500/AEPS20161208002.
[8] 徐敏,涂亮,柳勇军,等.水电机组高占比电网频率振荡问题分析[J].广东电力,2017,30(7):46-52.XU Min, TU Liang, LIU Yongjun, et al. Analysis on frequency oscillation of power grid with high-proportion of hydro-electric generating set[J]. Guangdong Electric Power, 2017, 30(7): 46-52.
[9] 陈磊,路晓敏,陈亦平,等.利用暂态能量流的超低频振荡在线分析与紧急控制方法[J].电力系统自动化,2017,41(17):9-14.DOI:10.7500/AEPS20161208004.CHEN Lei, LU Xiaomin, CHEN Yiping, et al. Online analysis and emergency control of ultra-low-frequency oscillations using transient energy flow[J]. Automation of Electric Power Systems, 2017, 41(17): 9-14. DOI: 10.7500/AEPS 20161208004.
[10] CHEN Lei, LU Xiaomin, MIN Yong, et al. Optimization of governor parameters to prevent frequency oscillations in power systems[J]. IEEE Transactions on Power Systems, 2018, 33(4): 4466-4474.
[11] 周靖皓,江崇熙,甘德强,等.基于值集法对云南电网超低频振荡的稳定分析[J].电网技术,2017,41(10):3147-3152.ZHOU Jinghao, JIANG Chongxi, GAN Deqiang, et al. Stability analysis of ultra-low frequency oscillation of Yunnan power grid based on value set approach[J]. Power System Technology, 2017, 41(10): 3147-3152.
[12] 周靖皓,石鹏,甘德强,等.值集法在大电网鲁棒稳定分析中的实现及与μ方法比较[J].电力系统自动化,2018,42(1):98-104.DOI:10.7500/AEPS20170424007.ZHOU Jinghao, SHI Peng, GAN Deqiang, et al. Implementation of value set approach in robust stability analysis of large power systems and its comparison with μ-based approach[J]. Automation of Electric Power Systems, 2018, 42(1): 98-104. DOI: 10.7500/AEPS20170424007.
[13] 陈磊,路晓敏,陈亦平,等.多机系统超低频振荡分析与等值方法[J].电力系统自动化,2017,41(22):10-15.DOI:10.7500/AEPS20170528001.CHEN Lei, LU Xiaomin, CHEN Yiping, et al. Analysis of ultra-low-frequency oscillations in multi-machine system and equivalent method[J]. Automation of Electric Power Systems, 2017, 41(22): 10-15. DOI: 10.7500/AEPS20170528001.
[14] 李伟,肖湘宁,郭琦.云广特高压直流送端孤岛运行超低频振荡与措施[J].电力系统自动化,2018,42(16):161-166.DOI:10.7500/AEPS20170816006.LI Wei, XIAO Xiangning, GUO Qi. Ultra-low-frequency oscillation and countermeasures in Yunnan-Guangdong UHVDC sending-end system in islanded operating mode[J]. Automation of Electric Power Systems, 2018, 42(16): 161-166. DOI: 10.7500/AEPS20170816006.
[15] 戴忠达.自动控制理论基础[M].北京:清华大学出版社,1991.DAI Zhongda. Theoretical basis of automatic control[M]. Beijing: Tsinghua University Press, 1991.