孤岛微网中虚拟同步发电机不平衡电压控制
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摘要
在孤岛微网中,逆变器采用虚拟同步发电机(virtual synchronous generator,VSG)控制后,有利于提升微网的电压和频率稳定;但现有的VSG控制策略,带不平衡负荷的能力差,降低了供电电压品质。建立了VSG的数学模型,分析了输出电压不平衡的产生机理和抑制措施。基于正序和负序网络阻抗的独立解耦控制,提出一种抑制负序电压的控制方法。采用复系数滤波器快速检测负序电流,利用复系数比例积分控制器实现电压跟踪。研究了滤波器和控制器关键参数的设计方法,实现VSG对正序和负序输出电压的独立控制,便于其正序和负序阻抗的定制化控制。通过对一台VSG样机进行实验,验证了所提控制策略的正确性和有效性,为VSG的运行控制提供了一种新思路。
To stabilize the voltage and frequency in an islanded micro-grid, virtual synchronous generator(VSG) control of renewable energy interfaced inverters is recommended. However, the state-of-art of VSG control strategy is challenged by commonly used unbalance loads, and the resulted unbalance voltage problem degrades the power quality of the micro-grid. In this paper, the mathematical model of VSG was presented. The operation mechanism of VSG in unbalance condition was proposed, and some strategies were derived to maintain the unbalance issues. Based on the decoupling control of positive- and negative-sequence impedances of VSG, an approach was proposed to eliminate the negative-sequence voltage of VSG with asymmetric loads. To ensure accurate voltage detection and tracking, complex filter and complex proportional-integral controller were utilized to identify and suppress the sequence-independent voltages, respectively. The key parameters of these complex control blocks were well designed to confirm the performances of proposed VSG control scheme. Finally, a VSG prototype was built, and the proposed VSG control program was downloaded. Validity and effectiveness of the proposed VSG control were verified by experimental results, compared to traditional VSG control technique.
To stabilize the voltage and frequency in an islanded micro-grid, virtual synchronous generator(VSG) control of renewable energy interfaced inverters is recommended. However, the state-of-art of VSG control strategy is challenged by commonly used unbalance loads, and the resulted unbalance voltage problem degrades the power quality of the micro-grid. In this paper, the mathematical model of VSG was presented. The operation mechanism of VSG in unbalance condition was proposed, and some strategies were derived to maintain the unbalance issues. Based on the decoupling control of positive- and negative-sequence impedances of VSG, an approach was proposed to eliminate the negative-sequence voltage of VSG with asymmetric loads. To ensure accurate voltage detection and tracking, complex filter and complex proportional-integral controller were utilized to identify and suppress the sequence-independent voltages, respectively. The key parameters of these complex control blocks were well designed to confirm the performances of proposed VSG control scheme. Finally, a VSG prototype was built, and the proposed VSG control program was downloaded. Validity and effectiveness of the proposed VSG control were verified by experimental results, compared to traditional VSG control technique.
引文
[1]杨新法,苏剑,吕志鹏,等.微电网技术综述[J].中国电机工程学报,2014,34(1):57-70.Yang Xinfa,Su Jian,LüZhipeng,et al.Overview on micro-grid technology[J].Proceedings of the CSEE,2014,34(1):57-70(in Chinese).
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[10]Zhong Q C,Nguyen P L,Ma Z,et al.Self-synchronized synchronverters:Inverters without a dedicated synchronization unit[J].IEEE Transactions on Power Electronics,2014,29(2):617-630.
[11]侍乔明,王刚,付立军,等.基于虚拟同步发电机原理的模拟同步发电机设计方法[J].电网技术,2015,39(3):783-790.Shi Qiaoming,Wang Gang,Fu Lijun,et al.A Design Method of Simulative Synchronous Generator Based on Virtual Synchronous Generator Theory[J].Power System Technology,2015,39(3):783-790(in Chinese).
[12]D'Arco S,Suul J A.Equivalence of virtual synchronous machines and frequency-droops for converter-based microgrids[J].IEEE Transactions on Smart Grid,2014,5(1):394-395.
[13]Zhong Q C,Hornik T.Control of power inverters in renewable energy and smart grid integration[M].Wiley:IEEE Press,2012:279-282.
[14]蒋雯倩,谭骞,吕志鹏,等.三相四桥臂并网逆变器模拟同步发电机控制策略[J].智能电网,2015(8):683-689.Jiang Wenqian,Tan Qian,Lu Zhipeng,et al.Research of three-phase four-wire grid-connected inverter which mimics synchronous generator characteristic[J].Smart Grid,2015(8):683-689(in Chinese).
[15]周洁,罗安,陈燕东,等.低压微电网多逆变器并联下的电压不平衡补偿方法[J].电网技术,2014,38(2):412-418.Zhou Jie,Luo An,Chen Yandong,et al.Voltage unbalance compensation for low-voltage microgrid with multi parallelly connected inverters[J].Power System Technology,2014,38(2):412-418(in Chinese).
[16]Liu J,Yushi M,Ise T,et al.Parallel operation of a synchronous generator and a virtual synchronous generator under unbalanced loading condition in microgrids[C]//IEEE 8th International Power Electronics and Motion Control Conference(IPEMC-ECCE Asia).Hefei,China:IEEE,2016:3741-3748.
[17]陈天一,陈来军,汪雨辰,等.考虑不平衡电网电压的虚拟同步发电机平衡电流控制方法[J].电网技术,2016,40(3):904-909.Chen Tianyi,Chen Laijun,Wang Yuchen,et al.Balanced current control of virtual synchronous generator considering unbalanced grid voltage[J].Power System Technology,2016,40(3):904-909(in Chinese).
[18]Liu Quanwei,Tao Yong,Liu Xunhao,et al.Voltage unbalance and harmonics compensation for islanded microgrid inverters[J].IET Power Electronics,2014,7(5):1055-1063.
[19]王逸超,罗安,金国彬.微网逆变器的不平衡电压补偿策略[J].中国电机工程学报,2015,35(19):4956-4964.Wang Yichao,Luo An,Jin Guobin.An unbalanced voltage compensation method for parallel inverters in microgrids[J].Proceedings of the CSEE,2015,35(19):4956-4964(in Chinese).
[20]Cheng P T,Chen C A,Lee T L,et al.A cooperative imbalance compensation method for distributedgeneration interface converters[J].IEEE Transactions on Industry Applications,2009,45(2):805-815.
[21]Zhao Xin,Wu Xiaohua,Meng Lexuan,et al.A direct voltage unbalance compensation strategy for islanded microgrids[C]//IEEE Applied Power Electronics Conference and Exposition(APEC).Charlotte,NC,USA:IEEE,2015:3252-3259.
[22]Savaghebi M,Jalilian A,Vasquez J C,et al.Autonomous voltage unbalance compensation in an islanded droop-controlled microgrid[J].IEEE Transactions on Industrial Electronics,2013,60(4):1390-1402.
[23]Wang F,Benhabib M C,Duarte J L,et al.High performance stationary frame filters for symmetrical sequences or harmonics separation under a variety of grid conditions[C]//IEEE Applied Power Electronics Conference and Exposition(APEC).Washington,DC,USA:IEEE,2009:1570-1576.
[24]郭小强.光伏并网逆变器通用比例复数积分控制策略[J].中国电机工程学报,2015,35(13):3393-3399.Guo Xiaoqiang.Generalized proportional complex integral control scheme for pv grid-connected inverters[J].Proceedings of the CSEE,2015,35(13):3393-3399(in Chinese).
[2]王成山,李鹏.分布式发电、微网与智能配电网的发展与挑战[J].电力系统自动化,2010,34(2):10-14.Wang Chengshan,Li Peng.Development and challenges of distributed generation,the micro-grid and smart distribution system[J].Automation of Electric Power Systems,2010,34(2):10-14(in Chinese).
[3]Zeng Z,Zhao R,Yang H,et al.Policies and demonstrations of micro-grids in China:A review[J].Renewable and Sustainable Energy Reviews,2014,29:701-718.
[4]吕志鹏,刘海涛,苏剑,等.可改善微网电压调整的容性等效输出阻抗逆变器[J].中国电机工程学报,2013,33(9):2-9.LüZhipeng,Liu Haitao,Su Jian,et al.Micro-source inverters with capacitive equivalent output impedance for improving micro-grid voltages[J].Proceedings of the CSEE,2013,33(9):2-9(in Chinese).
[5]曾正,李辉,冉立.交流微电网逆变器控制策略述评[J].电力系统自动化,2016,40(9):142-151.Zeng Zheng,Li Hui,Ran Li.Comparison on control strategies of inverters in AC microgrids[J].Automation of Electric Power Systems,2016,40(9):142-151(in Chinese).
[6]Bevrani H,Ise T,Miura Y.Virtual synchronous generators:A survey and new perspectives[J].International Journal of Electrical Power and Energy Systems,2014,54:244-254.
[7]郑天文,陈来军,陈天一,等.虚拟同步发电机技术及展望[J].电力系统自动化,2015,39(21):165-175.Zheng Tianwen,Chen Laijun,Chen Tianyi,et al.Review and prospect of virtual synchronous generator technologies[J].Automation of Electric Power Systems,2015,39(21):165-175(in Chinese).
[8]吕志鹏,盛万兴,钟庆昌,等.虚拟同步发电机及其在微电网中的应用[J].中国电机工程学报,2014,34(16):2591-2603.LüZhipeng,Sheng Wanxing,Zhong Qingchang,et al.Virtual synchronous generator and its applications in micro-grid[J].Proceedings of the CSEE,2014,34(16):2591-2603(in Chinese).
[9]吴恒,阮新波,杨东升,等.虚拟同步发电机功率环的建模与参数设计[J].中国电机工程学报,2015,35(24):6508-6518.Wu Heng,Ruan Xinbo,Yang Dongsheng,et al.Modeling of the power loop and parameter design of virtual synchronous generators[J].Proceedings of the CSEE,2015,35(24):6508-6518(in Chinese).
[10]Zhong Q C,Nguyen P L,Ma Z,et al.Self-synchronized synchronverters:Inverters without a dedicated synchronization unit[J].IEEE Transactions on Power Electronics,2014,29(2):617-630.
[11]侍乔明,王刚,付立军,等.基于虚拟同步发电机原理的模拟同步发电机设计方法[J].电网技术,2015,39(3):783-790.Shi Qiaoming,Wang Gang,Fu Lijun,et al.A Design Method of Simulative Synchronous Generator Based on Virtual Synchronous Generator Theory[J].Power System Technology,2015,39(3):783-790(in Chinese).
[12]D'Arco S,Suul J A.Equivalence of virtual synchronous machines and frequency-droops for converter-based microgrids[J].IEEE Transactions on Smart Grid,2014,5(1):394-395.
[13]Zhong Q C,Hornik T.Control of power inverters in renewable energy and smart grid integration[M].Wiley:IEEE Press,2012:279-282.
[14]蒋雯倩,谭骞,吕志鹏,等.三相四桥臂并网逆变器模拟同步发电机控制策略[J].智能电网,2015(8):683-689.Jiang Wenqian,Tan Qian,Lu Zhipeng,et al.Research of three-phase four-wire grid-connected inverter which mimics synchronous generator characteristic[J].Smart Grid,2015(8):683-689(in Chinese).
[15]周洁,罗安,陈燕东,等.低压微电网多逆变器并联下的电压不平衡补偿方法[J].电网技术,2014,38(2):412-418.Zhou Jie,Luo An,Chen Yandong,et al.Voltage unbalance compensation for low-voltage microgrid with multi parallelly connected inverters[J].Power System Technology,2014,38(2):412-418(in Chinese).
[16]Liu J,Yushi M,Ise T,et al.Parallel operation of a synchronous generator and a virtual synchronous generator under unbalanced loading condition in microgrids[C]//IEEE 8th International Power Electronics and Motion Control Conference(IPEMC-ECCE Asia).Hefei,China:IEEE,2016:3741-3748.
[17]陈天一,陈来军,汪雨辰,等.考虑不平衡电网电压的虚拟同步发电机平衡电流控制方法[J].电网技术,2016,40(3):904-909.Chen Tianyi,Chen Laijun,Wang Yuchen,et al.Balanced current control of virtual synchronous generator considering unbalanced grid voltage[J].Power System Technology,2016,40(3):904-909(in Chinese).
[18]Liu Quanwei,Tao Yong,Liu Xunhao,et al.Voltage unbalance and harmonics compensation for islanded microgrid inverters[J].IET Power Electronics,2014,7(5):1055-1063.
[19]王逸超,罗安,金国彬.微网逆变器的不平衡电压补偿策略[J].中国电机工程学报,2015,35(19):4956-4964.Wang Yichao,Luo An,Jin Guobin.An unbalanced voltage compensation method for parallel inverters in microgrids[J].Proceedings of the CSEE,2015,35(19):4956-4964(in Chinese).
[20]Cheng P T,Chen C A,Lee T L,et al.A cooperative imbalance compensation method for distributedgeneration interface converters[J].IEEE Transactions on Industry Applications,2009,45(2):805-815.
[21]Zhao Xin,Wu Xiaohua,Meng Lexuan,et al.A direct voltage unbalance compensation strategy for islanded microgrids[C]//IEEE Applied Power Electronics Conference and Exposition(APEC).Charlotte,NC,USA:IEEE,2015:3252-3259.
[22]Savaghebi M,Jalilian A,Vasquez J C,et al.Autonomous voltage unbalance compensation in an islanded droop-controlled microgrid[J].IEEE Transactions on Industrial Electronics,2013,60(4):1390-1402.
[23]Wang F,Benhabib M C,Duarte J L,et al.High performance stationary frame filters for symmetrical sequences or harmonics separation under a variety of grid conditions[C]//IEEE Applied Power Electronics Conference and Exposition(APEC).Washington,DC,USA:IEEE,2009:1570-1576.
[24]郭小强.光伏并网逆变器通用比例复数积分控制策略[J].中国电机工程学报,2015,35(13):3393-3399.Guo Xiaoqiang.Generalized proportional complex integral control scheme for pv grid-connected inverters[J].Proceedings of the CSEE,2015,35(13):3393-3399(in Chinese).