不平衡负载工况下三相变流器有源功率解耦控制
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摘要
三相电压源型变流器(VSC)对于微电网的稳定运行有着重要的作用。然而,孤岛工况下带三相不平衡负载运行时,交流侧产生的二次脉动功率耦合至直流侧,导致系统的工作性能降低并影响系统的寿命。针对该问题,在二次功率脉动分析的基础上,提出了一种基于虚拟三相瞬时功率的解耦控制策略,通过控制虚拟三相瞬时功率脉动分量为0,在不增加开关器件的情况下,利用LCL滤波器中电容提供负载所需二次脉动功率,实现交直流侧二次脉动功率解耦。在此基础上进一步分析了该拓扑结构直流侧所需的最低电压以及电流应力影响因素。最后仿真和实验结果均表明所提控制策略可以较好地实现功率解耦控制,直流侧源电流二次脉动分量大大减小,有利于提高系统控制性能和实现直流侧电容轻量化。
Three-phase voltage source converter(VSC) plays important role in stable operation of microgrid. However, when operating with a three-phase unbalanced load under island condition, the secondary pulsating power generated on AC side is coupled to DC side, resulting in system performance degradation and affecting system life. Aiming at this problem, based on secondary power pulsation analysis, a decoupling control strategy based on virtual three-phase instantaneous power is proposed. By controlling the virtual three-phase instantaneous power pulsation component to zero, the secondary pulsating power required by the load is provided by the capacitors in LCL filter to realize secondary pulsation power decoupling between AC and DC sides without adding switching devices. Based on this, the influence factor of the minimum voltage on DC side of the topology and current stress are further analyzed. Finally, simulation and experimental results show that the proposed control strategy can achieve better power decoupling, and the ripple component in DC side source current is greatly reduced, which is beneficial to improve system control performance and realize weight reduction of DC side capacitor.
Three-phase voltage source converter(VSC) plays important role in stable operation of microgrid. However, when operating with a three-phase unbalanced load under island condition, the secondary pulsating power generated on AC side is coupled to DC side, resulting in system performance degradation and affecting system life. Aiming at this problem, based on secondary power pulsation analysis, a decoupling control strategy based on virtual three-phase instantaneous power is proposed. By controlling the virtual three-phase instantaneous power pulsation component to zero, the secondary pulsating power required by the load is provided by the capacitors in LCL filter to realize secondary pulsation power decoupling between AC and DC sides without adding switching devices. Based on this, the influence factor of the minimum voltage on DC side of the topology and current stress are further analyzed. Finally, simulation and experimental results show that the proposed control strategy can achieve better power decoupling, and the ripple component in DC side source current is greatly reduced, which is beneficial to improve system control performance and realize weight reduction of DC side capacitor.
引文
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[14]祝国平,阮新波,王学华,等.两级式单相逆变器二次纹波电流的抑制与动态特性的改善[J].中国电机工程学报,2013,33(12):72-80,188.Zhu Guoping,Ruan Xinbo,Wang Xuehua,et al.Suppression of the second harmonic current and improvement of the dynamic performance for two-stage single-phase inverters[J].Proceedings of the CSEE,2013,33(12):72-80,188(in Chinese).
[15]Krein P T,Balog R S,Mirjafari M.Minimum energy and capacitance requirements for single-phase inverters and rectifiers using a ripple port[J],IEEE Transactions on Power Electronics,2012,27(11):4690-4698.
[16]刘健犇,陈乔夫,代少君,等.串联混合型有源滤波器直流母线电压控制策略[J].电工技术学报,2012,27(9):54-61.Liu Jianben,Chen Qiaofu,Dai Shaojun,et al.DC-link voltage control strategy of series hybrid active power filter[J].Transactions of China Electrotechnical Society,2012,27(9):54-61(in Chinese).
[17]Tang F,Zhou J Y,Xin Z,et al.An improved three-phase voltage source converter with high-performance operation under unbalanced conditions[J].IEEE Access,2018,6(1):15908-15918.
[18]沈瑶,罗安,陈燕东,等.基于功率前馈的光伏并网控制方法及稳定性分析[J].电网技术,2014,38(9):2449-2454.Shen Yao,Luo An,Chen Yandong,et al.A power feedforward-based control approach for grid-connection of photovoltaic generation and its stability analysis[J].Power System Technology,2014,38(9):2449-2454(in Chinese).
[19]孙驰,马伟明,鲁军勇.三相逆变器输出电压不平衡的产生机理分析及其矫正[J].中国电机工程学报,2006,26(21):57-64.Sun Chi,Ma Weiming,Lu Junyong.Analysis of the unsymmetrical output voltage distortion mechanism of the three-phase inverter and its corrections[J].Proceedings of the CSEE,2006,26(21):57-64(in Chinese).
[20]丁浩,魏艳君,何宇,等.基于带不平衡度非线性正反馈的负序电流扰动孤岛检测方法[J].电工技术学报,2016,31(14):211-218.Ding Hao,Wei Yanjun,He Yu,et al.Negative-sequence current perturbation islanding detection method with nonlinear positive feedback of unbalance degree[J].Transactions of China Electrotechnical Society,2016,31(14):211-218(in Chinese).
[21]Zhou J Y,Tang F,Xin Z,et al.Differences between continuous single-phase and online three-phase power-decoupled converters[J].IEEE Transactions on Power Electronics,DOI:10.1109/TPEL.2018.2856830.
[2]梁建钢,金新民,荆龙,等.微电网系统准同期并网改进控制策略[J].电网技术,2014,38(11):3071-3078.Liang Jiangang,Jin Xinmin,Jing Long,et al.An improved control strategy for quasi-synchronous grid-connection of microgrid[J].Power System Technology,2014,38(11):3071-3078(in Chinese).
[3]赵冬梅,张楠,刘燕华,等.基于储能的微网并网和孤岛运行模式平滑切换综合控制策略[J].电网技术,2013,37(2):301-306.Zhao Dongmei,Zhang Nan,Liu Yanhua,et al.Synthetical control strategy for smooth switching between grid-connected and islanded operation modes of microgrid based on energy storage system[J].Power System Technology,2013,37(2):301-306(in Chinese).
[4]周小平,罗安,陈燕东,等.直流微电网中双向储能变换器的二次纹波电流抑制与不均衡控制策略[J].电网技术,2016,40(9):2682-2688.Zhou Xiaoping,Luo An,Chen Yandong,et al.Secondary ripple current suppression and imbalance control strategy in bidirectional storage converter of DC microgrid[J].Power System Technology,2016,40(9):2682-2688(in Chinese).
[5]彭力,白丹.三相逆变器不平衡抑制研究[J].中国电机工程学报,2004,24(5):174-178.Peng Li,Bai Dan.Research on three-phase inverter with unbalanced load[J].Proceedings of the CSEE,2004,24(5):174-178(in Chinese).
[6]周啸,金新民,唐芬,等.αβ0坐标系下带不平衡负载的三相四桥臂变流器控制策略[J].中国电机工程学报,2014,34(19):3105-3113.Zhou Xiao,Jin Xinmin,Tang Fen,et al.Control of a three-phase fourleg converter powering unbalanced load inαβ0 frame[J].Proceedings of the CSEE,2014,34(19):3105-3113(in Chinese).
[7]周啸,金新民,唐芬,等.不平衡负载条件下三相四桥臂变流器的改进分序控制[J].高电压技术,2014,40(8):2504-2512.Zhou Xiao,Jin Xinmin,Tang Fen,et al.Improved sequence decomposition control strategy for three-phase four-leg inverter with unbalanced load[J].High Voltage Engineering,2014,40(8):2504-2512(in Chinese).
[8]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器控制[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).
[9]于明总,唐芬,吴学智,等.单/三相混合微网中虚拟组合式三相变流器功率协调控制[J].电力系统自动化,2018,42(7):192-198.Yu Mingzong,Tang Fen,Wu Xuezhi,et al.Coordinated power control of virtual combined three-phase converter in single-phase/three-phase hybrid microgrid[J].Automation of Electric Power Systems,2018,42(7):192-198(in Chinese).
[10]王恒利,付立军,肖飞,等.三相逆变器不平衡负载条件下双环控制策略[J].电网技术,2013,37(2):398-404.Wang Hengli,Fu Lijun,Xiao Fei,et al.A double-loop control strategy for three-phase inverter with unbalanced load[J].Power System Technology,2013,37(2):398-404(in Chinese).
[11]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 microgrid[J].Proceedings of the CSEE,2015,35(19):4956-4964(in Chinese).
[12]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).
[13]Qi W L,Wang H,Tan X G,et al.A novel active power decoupling single-phase PWM rectifier topology[C]//IEEE Applied Power Electronics Conference and Exposition.Fort Worth,TX,USA:IEEE,2014:1048-2334.
[14]祝国平,阮新波,王学华,等.两级式单相逆变器二次纹波电流的抑制与动态特性的改善[J].中国电机工程学报,2013,33(12):72-80,188.Zhu Guoping,Ruan Xinbo,Wang Xuehua,et al.Suppression of the second harmonic current and improvement of the dynamic performance for two-stage single-phase inverters[J].Proceedings of the CSEE,2013,33(12):72-80,188(in Chinese).
[15]Krein P T,Balog R S,Mirjafari M.Minimum energy and capacitance requirements for single-phase inverters and rectifiers using a ripple port[J],IEEE Transactions on Power Electronics,2012,27(11):4690-4698.
[16]刘健犇,陈乔夫,代少君,等.串联混合型有源滤波器直流母线电压控制策略[J].电工技术学报,2012,27(9):54-61.Liu Jianben,Chen Qiaofu,Dai Shaojun,et al.DC-link voltage control strategy of series hybrid active power filter[J].Transactions of China Electrotechnical Society,2012,27(9):54-61(in Chinese).
[17]Tang F,Zhou J Y,Xin Z,et al.An improved three-phase voltage source converter with high-performance operation under unbalanced conditions[J].IEEE Access,2018,6(1):15908-15918.
[18]沈瑶,罗安,陈燕东,等.基于功率前馈的光伏并网控制方法及稳定性分析[J].电网技术,2014,38(9):2449-2454.Shen Yao,Luo An,Chen Yandong,et al.A power feedforward-based control approach for grid-connection of photovoltaic generation and its stability analysis[J].Power System Technology,2014,38(9):2449-2454(in Chinese).
[19]孙驰,马伟明,鲁军勇.三相逆变器输出电压不平衡的产生机理分析及其矫正[J].中国电机工程学报,2006,26(21):57-64.Sun Chi,Ma Weiming,Lu Junyong.Analysis of the unsymmetrical output voltage distortion mechanism of the three-phase inverter and its corrections[J].Proceedings of the CSEE,2006,26(21):57-64(in Chinese).
[20]丁浩,魏艳君,何宇,等.基于带不平衡度非线性正反馈的负序电流扰动孤岛检测方法[J].电工技术学报,2016,31(14):211-218.Ding Hao,Wei Yanjun,He Yu,et al.Negative-sequence current perturbation islanding detection method with nonlinear positive feedback of unbalance degree[J].Transactions of China Electrotechnical Society,2016,31(14):211-218(in Chinese).
[21]Zhou J Y,Tang F,Xin Z,et al.Differences between continuous single-phase and online three-phase power-decoupled converters[J].IEEE Transactions on Power Electronics,DOI:10.1109/TPEL.2018.2856830.