基于同步补偿的孤岛微电网无功均分研究
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摘要
交流微电网孤岛运行时,由于分布式电源(DG)的等效线路阻抗存在差异,导致传统下垂控制无功均分精度较低,进而产生环流问题。为此,提出了一种基于同步补偿的改进下垂控制策略。当DG运行在无功均分模式时,同步补偿下垂特性曲线的参考电压,可以提高无功功率均分的精度。当有DG输出电压降至限定最小值时,各个DG均切换至电压恢复模式,同步恢复电压至参考电压。同时设计控制策略协调无功均分模式和电压恢复模式,使得系统稳定运行,最终实现DG输出的无功功率均分且输出电压在额定值附近。最后设计Matlab仿真和RTDS实验方案,结果验证了所设计的控制策略的有效性,且对通信带宽要求较低,具有较强的鲁棒性,仍保持了微电网各DG的"即插即用"的特点。
In the islanded AC microgrid, the line impedance between the DG units are always different, which can result in circulating current and low precision of power sharing among inverters by using the traditional droop control method. Therefore, an improved droop control strategy is proposed based on synchronous compensation for reactive power sharing in microgrid. The reference voltage of droop characteristic curve can be compensated synchronously when DG units operate at reactive power sharing mode, meanwhile the accuracy of the sharing of reactive power can also be improved. And then when the output voltage of a DG unit drops to the minimum value, each DG unit switches to the voltage recovery mode, and its voltage will recover to the reference voltage synchronously. The improved coordinated operation strategy is designed for reactive power sharing mode and voltage recovery mode, which can ensure that the accurate sharing of reactive power and the output voltage is near the rated value, and then the system can operate stably. Finally, simulations and experiments are performed in MATLAB and real-time digital simulator(RTDS) respectively to verify the validity of the proposed control strategy. It is proved that the method has low communication bandwidth requirement and strong robustness, and maintains the characteristic of"plug and play" of each DG.
In the islanded AC microgrid, the line impedance between the DG units are always different, which can result in circulating current and low precision of power sharing among inverters by using the traditional droop control method. Therefore, an improved droop control strategy is proposed based on synchronous compensation for reactive power sharing in microgrid. The reference voltage of droop characteristic curve can be compensated synchronously when DG units operate at reactive power sharing mode, meanwhile the accuracy of the sharing of reactive power can also be improved. And then when the output voltage of a DG unit drops to the minimum value, each DG unit switches to the voltage recovery mode, and its voltage will recover to the reference voltage synchronously. The improved coordinated operation strategy is designed for reactive power sharing mode and voltage recovery mode, which can ensure that the accurate sharing of reactive power and the output voltage is near the rated value, and then the system can operate stably. Finally, simulations and experiments are performed in MATLAB and real-time digital simulator(RTDS) respectively to verify the validity of the proposed control strategy. It is proved that the method has low communication bandwidth requirement and strong robustness, and maintains the characteristic of"plug and play" of each DG.
引文
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[13]Li Y W,Kao C N.An accurate power control strategy for power electronics interfaced distributed generation units operating in a low-voltage multibus microgrid[J].IEEE Transactions on Power Electronics,2009,24(12):2977-2988.
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[15]徐海珍,张兴,刘芳,等.基于虚拟电容的微网逆变器无功均分控制策略[J].电力系统自动化,2016,40(19):59-65.Xu Haizhen,Zhang Xing,Liu Fang,et al.Reactive power sharing control strategy for microgrid inverters based on virtual capacitor[J].Automation of Electric Power Systems,2016,40(19):59-65.
[16]Xu Haizhen,Zhang Xing,Liu Fang,et al.A reactive power sharing strategy of VSG based on virtual capacitor algorithm[J].IEEE Transactions on Industrial Electronics,2017,64(9):7520-7531.
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[18]刘尧,韩华,粟梅,等.一种并联分布式微源的无功功率均分控制策略[J].中南大学学报(自然科学版),2015,46(2):525-533.Liu Yao,Han Hua,Su Mei,et al.A control strategy of reactive power sharing for parallel distributed microsources[J].Journal of Central South University(Science and Technology),2015,46(2):525-533.
[19]吕振宇,苏晨,吴在军,等.孤岛型微电网分布式二次调节策略及通信拓扑优化[J].电工技术学报,2017,32(6):209-219.LüZhenyu,Su Chen,Wu Zaijun,et al.Distributed secondary control strategy and its communication topology optimization for islanded microgrid[J].Transactions of China Electrotechnical Society,2017,32(6):209-219.
[20]刘尧,林超,陈滔,等.基于自适应虚拟阻抗的交流微电网无功功率-电压控制策略[J].电力系统自动化,2017,41(5):16-21.Liu Yao,Lin Chao,Chen Tao,et al.Reactive powervoltage control strategy of AC microgrid based on adaptive virtual impedance[J].Automation of Electric Power Systems,2017,41(5):16-21.
[21]胡寿松.自动控制原理[M].北京:科学出版社,2013.
[22]刘一欣,郭力,李霞林,等.基于实时数字仿真的微电网数模混合仿真实验平台[J].电工技术学报,2014,29(2):82-92.Liu Yixin,Guo Li,Li Xialin,et al.Real-time digital simulator based digital-analog hybrid simulation exprimental platform for a microgrid[J].Transactions of China Electrotechnical Society,2014,29(2):82-92.
[2]Liu Xiaonan,Wang Peng,Loh P C.A hybrid AC/DCmicrogrid and its coordination control[J].IEEETransactions on Smart Grid,2011,2(2):278-286.
[3]周念成,金明,王强钢,等.串联和并联结构的多微网系统分层协调控制策略[J].电力系统自动化,2013,37(12):13-18.Zhou Niancheng,Jin Ming,Wang Qianggang,et al.Hierarchical coordination control strategy for multimicrogrid system with series and parallel structure[J].Automation of Electric Power Systems,2013,37(12):13-18.
[4]芦思晨,潘再平.无储能风电微网系统的下垂控制策略[J].电工技术学报,2016,31(18):169-175.Lu Sichen,Pan Zaiping.Droop control strategy of wind power microgrid system without energy storage device[J].Transactions of China Electrotechnical Society,2016,31(18):169-175.
[5]袁昊哲,杨苹.串联结构多微网并离网模式切换控制策略[J].电力系统保护与控制,2017,45(19):94-100.Yuan Haozhe,Yang Ping.Grid-connected and off-grid mode switching control strategies of multi-microgrid with series structure[J].Power System Protection&Control,2017,45(19):94-100.
[6]万玉建,蒋成杰,陆华军.一种微电网并转孤模式切换时功率平衡计算方法[J].电气技术,2015,16(11):40-43.Wan Yujian,Jiang Chengjie,Lu Huajun.The algorithm for power balance of microgrid to solving the problem of grid-connected mode transferring to islanding mode[J].Electrical Engineering,2015,16(11):40-43.
[7]王明玥,罗安,陈燕东,等.三相逆变器的双模式及其平滑切换控制方法[J].电工技术学报,2016,31(16):124-134.Wang Mingyue,Luo An,Chen Yandong,et al.The dual-mode control and seamless transfer control method of three-phase inverter[J].Transactions of China Electrotechnical Society,2016,31(16):124-134.
[8]唐昆明,王俊杰,张太勤.基于自适应下垂控制的微电网控制策略研究[J].电力系统保护与控制,2016,44(18):68-74.Tang Kunming,Wang Junjie,Zhang Taiqin.Research on control strategy for microgrid based on adaptive droop control[J].Power System Protection&Control,2016,44(18):68-74.
[9]周乐明,罗安,陈燕东,等.一种低延时鲁棒功率下垂控制方法[J].电工技术学报,2016,31(11):1-12.Zhou Leming,Luo An,Chen Yandong,et al.A lowdelay robust droop control method[J].Transactions of China Electrotechnical Society,2016,31(11):1-12.
[10]金国彬,罗安,陈燕东,等.基于P-V下垂系数修正的并联逆变器输出功率成比例分配实现[J].电工技术学报,2016,31(2):112-120.Jin Guobin,Luo An,Chen Yandong,et al.Proportional load sharing for parallel inverter systems based on modified P-V droop coefficient[J].Transactions of China Electrotechnical Society,2016,31(2):112-120.
[11]陈晓祺,贾宏杰,陈硕翼,等.基于线路阻抗辨识的微电网无功均分改进下垂控制策略[J].高电压技术,2017,43(4):1271-1279.Chen Xiaoqi,Jia Hongjie,Chen Shuoyi,et al.Improved droop control strategy based on line impedance identification for reactive power sharing in microgrid[J].High Voltage Engineering,2017,43(4):1271-1279.
[12]陈晓祺,贾宏杰,陈硕翼,等.基于线路观测器的孤岛运行微电网改进下垂控制策略[J].高电压技术,2016,42(7):2174-2183.Chen Xiaoqi,Jia Hongjie,Chen Shuoyi,et al.Improved droop control strategy based on line impedance observer in islanded microgird[J].High Voltage Engineering,2016,42(7):2174-2183.
[13]Li Y W,Kao C N.An accurate power control strategy for power electronics interfaced distributed generation units operating in a low-voltage multibus microgrid[J].IEEE Transactions on Power Electronics,2009,24(12):2977-2988.
[14]马添翼,金新民,梁建钢.孤岛模式微电网变流器的复合式虚拟阻抗控制策略[J].电工技术学报,2013,28(12):304-312.Ma Tianyi,Jin Xinmin,Liang Jiangang,et al.Multiple virtual impedance control method of micro-grid converter under island mode[J].Transactions of China Electrotechnical Society,2013,28(12):304-312.
[15]徐海珍,张兴,刘芳,等.基于虚拟电容的微网逆变器无功均分控制策略[J].电力系统自动化,2016,40(19):59-65.Xu Haizhen,Zhang Xing,Liu Fang,et al.Reactive power sharing control strategy for microgrid inverters based on virtual capacitor[J].Automation of Electric Power Systems,2016,40(19):59-65.
[16]Xu Haizhen,Zhang Xing,Liu Fang,et al.A reactive power sharing strategy of VSG based on virtual capacitor algorithm[J].IEEE Transactions on Industrial Electronics,2017,64(9):7520-7531.
[17]孙孝峰,王娟,田艳军,等.基于自调节下垂系数的DG逆变器控制[J].中国电机工程学报,2013,33(36):71-78.Sun Xiaofeng,Wang Juan,Tian Yanjun,et al.Control of DG connected inverters based on self-adaptable adjustment of droop coefficient[J].Proceedings of the Csee,2013,33(36):71-78.
[18]刘尧,韩华,粟梅,等.一种并联分布式微源的无功功率均分控制策略[J].中南大学学报(自然科学版),2015,46(2):525-533.Liu Yao,Han Hua,Su Mei,et al.A control strategy of reactive power sharing for parallel distributed microsources[J].Journal of Central South University(Science and Technology),2015,46(2):525-533.
[19]吕振宇,苏晨,吴在军,等.孤岛型微电网分布式二次调节策略及通信拓扑优化[J].电工技术学报,2017,32(6):209-219.LüZhenyu,Su Chen,Wu Zaijun,et al.Distributed secondary control strategy and its communication topology optimization for islanded microgrid[J].Transactions of China Electrotechnical Society,2017,32(6):209-219.
[20]刘尧,林超,陈滔,等.基于自适应虚拟阻抗的交流微电网无功功率-电压控制策略[J].电力系统自动化,2017,41(5):16-21.Liu Yao,Lin Chao,Chen Tao,et al.Reactive powervoltage control strategy of AC microgrid based on adaptive virtual impedance[J].Automation of Electric Power Systems,2017,41(5):16-21.
[21]胡寿松.自动控制原理[M].北京:科学出版社,2013.
[22]刘一欣,郭力,李霞林,等.基于实时数字仿真的微电网数模混合仿真实验平台[J].电工技术学报,2014,29(2):82-92.Liu Yixin,Guo Li,Li Xialin,et al.Real-time digital simulator based digital-analog hybrid simulation exprimental platform for a microgrid[J].Transactions of China Electrotechnical Society,2014,29(2):82-92.