Influence Analysis of Virtual Impedance on the Stability of Parallel System of Inverters with Different Voltage Levels

doi:10.11930/j.issn.1004-9649.202004204

Abstract

Abstract: Using virtual impedance technology to optimize the double closed-loop control structure can improve the equivalent output impedance of the inverter to be inductive and enhance the accuracy of power distribution by traditional inductive droop control strategies in low-voltage micro-grids, thus inhibiting circulating current. This approach, however, tends to overlook the impact of virtual impedance on system stability. In this regard, the transfer function of a three-loop control structure is derived, which includes virtual impedance, line impedance and common point voltage. A parallel model of inverters with different voltage levels is built, considering virtual complex impedance, and the model is simplified with the Thevenin’s equivalent. According to the Nyquist stability criterion, the effect of virtual impedance on system stability is analyzed under various operating conditions. The results show that the multi-inverter parallel system can maintain stable operation after the virtual impedance is added.

Key words: low-voltage micro-grid, virtual impedance, Thevenin's equivalent, Nyquist stability criterion, stability

MA Wentao, WANG Jinmei, WANG Yongqi. Influence Analysis of Virtual Impedance on the Stability of Parallel System of Inverters with Different Voltage Levels[J]. Electric Power, 2021, 54(9): 135-142,175.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202004204

https://www.electricpower.com.cn/EN/Y2021/V54/I9/135

References

[1] 王凌云, 周璇卿, 李升, 等. 基于改进功率环的微电网对等控制策略研究[J]. 中国电力, 2017, 50(9): 171-177
WANG Lingyun, ZHOU Xuanqing, LI Sheng, et al. Research on peer to peer control strategy for microgrid based on the improved power loop[J]. Electric Power, 2017, 50(9): 171-177
[2] 张国荣, 丁晓通, 彭勃, 等. 交直流混合微电网互联变流器改进控制策略[J]. 电力系统保护与控制, 2020, 48(14): 50-58
ZHANG Guorong, DING Xiaotong, PENG Bo, et al. Improved control strategy for an AC/DC hybrid microgrid interlinking converter[J]. Power System Protection and Control, 2020, 48(14): 50-58
[3] 马宏涛, 周博昊, 贺亚慧, 等. 微网无缝切换控制策略研究[J]. 智慧电力, 2020, 48(5): 53-59
MA Hongtao, ZHOU Bohan, HE Yahui, et al. Seamless switching strategies for microgrid[J]. Smart Power, 2020, 48(5): 53-59
[4] 吕志鹏, 罗安, 蒋雯倩, 等. 多逆变器环境微网环流控制新方法[J]. 电工技术学报, 2012, 27(1): 40-47
LÜ Zhipeng, LUO An, JIANG Wenqian, et al. New circulation control method for micro-grid with multi-inverter micro-sources[J]. Transactions of China Electrotechnical Society, 2012, 27(1): 40-47
[5] 阳敏, 罗安, 肖华根, 等. 多逆变器并联系统环流分析及抑制方法[J]. 电力系统及其自动化学报, 2017, 29(10): 6-11
YANG Min, LUO An, XIAO Huagen, et al. Circulating current analysis and suppression method for multi-inverter parallel system[J]. Proceedings of the CSU-EPSA, 2017, 29(10): 6-11
[6] 关雅娟, 邬伟扬, 郭小强. 微电网中三相逆变器孤岛运行控制技术[J]. 中国电机工程学报, 2011, 31(33): 52-60
GUAN Yajuan, WU Weiyang, GUO Xiaoqiang. Control strategy for three-phase inverters dominated microgrid in autonomous operation[J]. Proceedings of the CSEE, 2011, 31(33): 52-60
[7] 李慧, 张鹏, 刘思嘉. MMC环流抑制策略的暂态分析[J]. 电力系统保护与控制, 2021, 49(2): 30-38
LI Hui, ZHANG Peng, LIU Sijia. Transient analysis of MMC circulating current suppression strategy[J]. Power System Protection and Control, 2021, 49(2): 30-38
[8] 周保荣, 李选平, 杨健, 等. 向无源电网供电的MMC-HVDC稳态运行区域分析[J]. 智慧电力, 2020, 48(6): 98-104
ZHOU Baorong, LI Xuanping, YANG Jian, et al. Analysis of steady operation region of MMC-HVDC connected to passive network[J]. Smart Power, 2020, 48(6): 98-104
[9] 张春刚, 罗璐, 李青璇, 等. 低压微电网多台并联逆变电源的功率分配策略综述[J]. 电气技术, 2018, 19(9): 1-5, 11
ZHANG Chungang, LUO Lu, LI Qingxuan, et al. Research on power allocation strategy of multiple parallel inverters in low voltage microgrid[J]. Electrical Engineering, 2018, 19(9): 1-5, 11
[10] 杨旭生, 陈伟, 吴丽珍. 微电网的电压质量控制方法[J]. 电力系统及其自动化学报, 2018, 30(4): 63-69
YANG Xusheng, CHEN Wei, WU Lizhen. Voltage quality control method for microgrid[J]. Proceedings of the CSU-EPSA, 2018, 30(4): 63-69
[11] WU T, LIU Z, LIU J J, et al. A decoupled current droop control method for parallel inverters in microgrids[C]//2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia (IFEEC 2017 - ECCE Asia). Kaohsiung, Taiwan, China. IEEE, 2017: 2117-2122.
[12] MAHMOOD H, MICHAELSON D, JIANG J. Accurate reactive power sharing in an islanded microgrid using adaptive virtual impedances[J]. IEEE Transactions on Power Electronics, 2015, 30(3): 1605-1617.
[13] 朱永兴. 虚拟负阻抗在微网下垂控制中的应用[J]. 电力系统及其自动化学报, 2014, 26(3): 66-71
ZHU Yongxing. Application of virtual negative resistance on microgrid droop control[J]. Proceedings of the CSU-EPSA, 2014, 26(3): 66-71
[14] NIE B, LI X M. A control method for parallel inverter with adaptive virtual impedance[C]//2018 5th International Conference on Systems and Informatics (ICSAI). Nanjing, China. IEEE, 2018: 171-175.
[15] 缪惠宇, 梅飞, 张宸宇, 等. 含有虚拟阻抗的微源逆变器微网小信号稳定性分析[J]. 可再生能源, 2019, 37(4): 531-537
MIAO Huiyu, MEI Fei, ZHANG Chenyu, et al. Small-signal stability analysis of microgrid distributed generation converter with virtual impedance[J]. Renewable Energy Resources, 2019, 37(4): 531-537
[16] 周林, 张密, 居秀丽, 等. 电网阻抗对大型并网光伏系统稳定性影响分析[J]. 中国电机工程学报, 2013, 33(34): 34-41, 9
ZHOU Lin, ZHANG Mi, JU Xiuli, et al. Stability analysis of large-scale photovoltaic plants due to grid impedances[J]. Proceedings of the CSEE, 2013, 33(34): 34-41, 9
[17] 张彩红. 基于阻抗模型的并网逆变器稳定性分析[D]. 哈尔滨: 哈尔滨工业大学, 2017.
ZHANG Caihong. Stability analysis of grid-connected inverter based on impedance model[D]. Harbin: Harbin Institute of Technology, 2017.
[18] 孙孝峰, 李钦钦. 多机下垂系统并联运行稳定性研究[J]. 太阳能学报, 2017, 38(4): 1013-1023
SUN Xiaofeng, LI Qinqin. Stability assessment for parallel operation of multiple unit droop control[J]. Acta Energiae Solaris Sinica, 2017, 38(4): 1013-1023
[19] 徐玉琴, 马焕均. 基于改进下垂控制的逆变器并联运行技术[J]. 电力系统保护与控制, 2015, 43(7): 103-107
XU Yuqin, MA Huanjun. Parallel operation technology of inverters based on improved droop control[J]. Power System Protection and Control, 2015, 43(7): 103-107
[20] 张继红, 贺智勇, 李华, 等. 基于孤岛模式的双储能微电网下垂协调控制及仿真[J]. 太阳能学报, 2015, 36(1): 146-153
ZHANG Jihong, HE Zhiyong, LI Hua, et al. Droop coordinated control and simulation based on islanded microgrid of dual energy storage[J]. Acta Energiae Solaris Sinica, 2015, 36(1): 146-153
[21] TAYAB U B, ROSLAN M A B, HWAI L J, et al. A review of droop control techniques for microgrid[J]. Renewable and Sustainable Energy Reviews, 2017, 76: 717-727.
[22] JIN L P, HE Z, ZHANG Y C, et al. A new virtual impedance method for parallel inverters with droop control[C]//2016 IEEE Vehicle Power and Propulsion Conference (VPPC). Hangzhou, China. IEEE, 2016: 1-4.
[23] GHOSH S, CHATTOPADHYAY S. Performance verification of a new integrated droop controller with a novel virtual-impedance based PLL for parallel operation of inverters[C]//2018 IEEE Energy Conversion Congress and Exposition (ECCE). Portland, OR, USA. IEEE, 2018: 5865-5872.
[24] ZHANG J W, CHEN J, CHEN X, et al. Modelling, analysis and design of droop-controlled parallel three phase voltage source inverter using dynamic phasors method[C]//2014 IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific). Beijing, China. IEEE, 2014: 1-6.
[25] 李圣清, 李静萍. 基于“虚拟复阻抗”的低压微网下垂控制策略[J]. 电气自动化, 2018, 40(5): 73-76
LI Shengqing, LI Jingping. Droop control strategy for the low-voltage micro-grid based on virtual complex impedance[J]. Electrical Automation, 2018, 40(5): 73-76
[26] 宋绍剑, 阳喜, 刘斌, 等. 基于电网阻抗的并网逆变器准比例谐振控制[J]. 中国电力, 2019, 52(12): 90-96
SONG Shaojian, YANG Xi, LIU Bin, et al. Quasi-proportional resonance control of grid-connected inverter based on grid impedance[J]. Electric Power, 2019, 52(12): 90-96
[27] 李琳, 刘慧, 车凯军, 等. 戴维宁定理的理解与运用[J]. 电气电子教学学报, 2016, 38(4): 61-65
LI Lin, LIU Hui, CHE Kaijun, et al. Comprehension and application of Thevenin's theorem[J]. Journal of Electrical & Electronic Education, 2016, 38(4): 61-65
[28] 赵清林, 宋文璐, 袁精, 等. 弱电网中基于调节器重构的多机并网稳定性研究[J]. 电机与控制学报, 2020, 24(1): 111-118
ZHAO Qinglin, SONG Wenlu, YUAN Jing, et al. Stability analysis of multi-grid-connected inverters based on regulator reconstruction in weak grid[J]. Electric Machines and Control, 2020, 24(1): 111-118
[29] 危杰, 丁宁, 熊峰, 等. 低压微电网平滑切换控制策略研究[J]. 电力学报, 2018, 33(4): 316-321, 339
WEI Jie, DING Ning, XIONG Feng, et al. Research on smooth switching control strategy of low voltage micro-grid[J]. Journal of Electric Power, 2018, 33(4): 316-321, 339