基于自适应虚拟谐波阻抗控制的孤岛微电网谐波均流策略
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摘要
孤岛微电网中非线性负载带来了大量谐波,若各并联逆变器连接至公共交流母线的馈线阻抗与其额定容量失配,将使得谐波电流不能在各逆变器间均匀分配。固定虚拟谐波阻抗方法可以有效地提高谐波电流分配精度,但会影响公共交流母线电压质量。因此,提出了一种自动调节虚拟谐波阻抗实现谐波均流的控制策略。各逆变器根据其谐波电流的有效值构造实时变化的虚拟谐波阻抗,建立起谐波电流与虚拟谐波阻抗的自调整关系,重塑系统在谐波域的输出阻抗以匹配馈线阻抗,动态调整谐波电流分配,有效地提高了谐波均流精度,且兼顾了公共交流母线的电压质量,无需检测线路阻抗信息。仿真和实验结果验证了所提策略的可行性。
In islanding microgrid high harmonic current exists due to nonlinear loads. When the feeder impedances connected to the common AC bus for parallel inverters mismatch with their rated capacities, the harmonic current will not be shared evenly among the distributed generating(DG) units. The fixed virtual harmonic impedance method can effectively improve accuracy of harmonic current sharing, but affect the voltage quality at the point of common coupling(PCC). Therefore, an adaptive virtual harmonic impedance method is proposed to improve accuracy of harmonic power sharing among the DG units. In this method, a variable virtual harmonic impedance in real time is constructed by introducing harmonic current information. An adaptive relationship between the harmonic current and the virtual harmonic impedance is established, and the output impedances of the system at harmonic frequencies are reconstructed. Thus the voltage quality at PCC is improved. In addition, the DG feeder impedance does not need to be detected. Simulation and experimental results demonstrate effectiveness of the proposed scheme.
In islanding microgrid high harmonic current exists due to nonlinear loads. When the feeder impedances connected to the common AC bus for parallel inverters mismatch with their rated capacities, the harmonic current will not be shared evenly among the distributed generating(DG) units. The fixed virtual harmonic impedance method can effectively improve accuracy of harmonic current sharing, but affect the voltage quality at the point of common coupling(PCC). Therefore, an adaptive virtual harmonic impedance method is proposed to improve accuracy of harmonic power sharing among the DG units. In this method, a variable virtual harmonic impedance in real time is constructed by introducing harmonic current information. An adaptive relationship between the harmonic current and the virtual harmonic impedance is established, and the output impedances of the system at harmonic frequencies are reconstructed. Thus the voltage quality at PCC is improved. In addition, the DG feeder impedance does not need to be detected. Simulation and experimental results demonstrate effectiveness of the proposed scheme.
引文
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[15]Zhou J G,Kim S,Zhang H,et al.Consensus-based distributed control for accurate reactive,harmonic and imbalance power sharing in microgrids[J].IEEE Transaction on Smart Grid,2018,9(4):2453-2467.
[16]He J W,Li Y W,Blaabjerg F.An enhanced islanding microgrid reactive power,impedance power,and harmonic power sharing scheme[J].IEEE Transactions on Power Electronics,2015,30(6):3389-3401.
[17]陈燕东,罗安,龙际根,等.阻性逆变器并联环流分析及鲁棒下垂多环控制[J].中国电机工程学报,2013,33(18):18-29.Chen Yandong,Luo An,Long Jigen,et al.Circulating current analysis and robust droop multiple loop control method for parallel inverters using resistive output impedance[J].Proceedings of the CSEE,2013,33(18):18-29(in Chinese).
[18]Vandoorn T,Meersman B,De Kooning J,et al.Controllable harmonic current sharing in islanded microgrids:DG units with programmable resistive behavior toward harmonics[J].IEEE Transactions on Power Delivery,2012,2(27):831-841.
[19]林燎源,林钊,刘伟,等.基于阻性下垂的逆变器无线并联均流控制[J].电工技术学报,2016,31(8):43-50.Lin Liaoyuan,Lin Zhao,Liu Wei,et al.Wireless current sharing scheme for parallel operation of inverters using resistive output impedance[J].Transactions of China Electrotechnical Society,2016,31(8):43-50(in Chinese).
[2]吕志鹏,吴鸣,黄红,等.一种具有网络自适应能力的分布式电源改进下垂控制策略[J].电网技术,2018,42(9):2948-2957.LüZhipeng,Wu Ming,Huang Hong,et al.An improved droop control with network self-adaptability for distributed generation[J].Power System Technology,2018,42(9):2948-2957(in Chinese).
[3]孙孝峰,杨雅麟,赵巍,等.微电网逆变器自适应下垂控制策略[J].电网技术,2014,38(9):2386-2391.Sun Xiaofeng,Yang Yalin,Zhao Wei,et al.An adaptive droop control method for inverters in microgrid[J].Power System Technology,2014,38(9):2386-2391(in Chinese).
[4]孙孝峰,郝彦从,赵巍,等.孤岛微电网无通信功率均分和电压恢复研究[J].电工技术学报,2016,31(1):55-61.Sun Xiaofeng,Hao Yancong,Zhao Wei,et al.Research of power sharing and voltage restoration without communication for islanded microgrid[J].Transactions of China Electrotechnical Society,2016,31(1):55-61(in Chinese).
[5]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(in Chinese).
[6]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 low delay robust droop control method[J].Transactions of China Electrotechnical Society,2016,31(11):1-12(in Chinese).
[7]任碧莹,赵欣荣,孙向东,等.不平衡负载下基于改进下垂控制策略的组合式三相逆变控制[J].电网技术,2016,40(4):1163-1168.Ren Biying,Zhao Xinrong,Sun Xiangdong,et al.Improved droop control based three-phase combined inverters for unbalanced load[J].Power System Technology,2016,40(4):1163-1168(in Chinese).
[8]De D,Ramanarayanan V.Decentralized parallel operation of inverters sharing unbalanced and nonlinear loads[J].IEEE Transactions on Power Electronics,2010,25(12):3015-3025.
[9]Zhong Q C.Harmonic droop controller to reduce the voltage harmonics of inverters[J].IEEE Transaction on Industrial Electronics,2013,60(3):936-945.
[10]Vandoorn T,Meersman B,Kooning J D.Controllable harmonic current sharing in islanded microgrids:DG units with programmable resistive behavior toward harmonics[J].IEEE Transaction on Power Delivery,2012,27(2):831-839.
[11]He J W,Li Y W,Guerrero J M.An islanding microgrid power sharing approach using enhanced virtual impedance control scheme[J].IEEETransactions on Power Electronics,2013,28(11):5272-5281.
[12]吕志鹏,盛万兴,蒋雯倩,等.具备电压稳定和环流抑制能力的分频下垂控制器[J].中国电机工程学报,2013,33(36):1-8.LüZhipeng,Sheng Wanxing,Jiang Wenqian,et al.Frequency dividing droop controllers with the function of voltage stabilization and circulation control[J].Proceedings of the CSEE,2013,33(36):1-8(in Chinese).
[13]Sreekumar P,Khadkikar V.A new virtual harmonic impedance scheme for harmonic power sharing in an islanded microgrid[J].IEEETransactions on Power Delivery,2016,31(3):936-945.
[14]张平,石健将,李荣贵,等.低压微网逆变器的“虚拟负阻抗”控制策略[J].中国电机工程学报,2014,34(12):1844-1852.Zhang Peng,Shi Jianjiang,Li Ronggui,et al.A control strategy of‘virtual negative’impedance for inverters in low-voltage microgrid[J].Proceedings of the CSEE,2014,34(12):1844-1852(in Chinese).
[15]Zhou J G,Kim S,Zhang H,et al.Consensus-based distributed control for accurate reactive,harmonic and imbalance power sharing in microgrids[J].IEEE Transaction on Smart Grid,2018,9(4):2453-2467.
[16]He J W,Li Y W,Blaabjerg F.An enhanced islanding microgrid reactive power,impedance power,and harmonic power sharing scheme[J].IEEE Transactions on Power Electronics,2015,30(6):3389-3401.
[17]陈燕东,罗安,龙际根,等.阻性逆变器并联环流分析及鲁棒下垂多环控制[J].中国电机工程学报,2013,33(18):18-29.Chen Yandong,Luo An,Long Jigen,et al.Circulating current analysis and robust droop multiple loop control method for parallel inverters using resistive output impedance[J].Proceedings of the CSEE,2013,33(18):18-29(in Chinese).
[18]Vandoorn T,Meersman B,De Kooning J,et al.Controllable harmonic current sharing in islanded microgrids:DG units with programmable resistive behavior toward harmonics[J].IEEE Transactions on Power Delivery,2012,2(27):831-841.
[19]林燎源,林钊,刘伟,等.基于阻性下垂的逆变器无线并联均流控制[J].电工技术学报,2016,31(8):43-50.Lin Liaoyuan,Lin Zhao,Liu Wei,et al.Wireless current sharing scheme for parallel operation of inverters using resistive output impedance[J].Transactions of China Electrotechnical Society,2016,31(8):43-50(in Chinese).
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