低开关频率下LCL型并网变流器复矢量分析及改进解耦控制
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摘要
同步旋转坐标系(dq)下的比例积分控制在并网变流器中得到广泛应用。由于滤波器和数字延迟的dq模型均存在轴间耦合并且两者相互影响,低开关频率下LCL型并网变流器的建模和解耦控制变得极具挑战。针对该问题,在对同步旋转坐标系下的LCL型并网变流器采用复矢量进行建模的基础上,通过双边频响特性曲线和零极点图对传统状态反馈和相位补偿进行了系统分析,揭示了不同位置相位补偿对系统相位裕度和解耦性能的影响关系,在此基础上提出了一种改进解耦控制方法,通过在状态反馈环内和调节器输出端依次设计相位补偿,在有效调节和改善动态性能的同时保证系统具有较好的解耦性能。最后,仿真及实验结果表明所提方法具有很好的解耦效果,同时能有效减小系统超调量和调节时间。
Proportional integral(PI) control in synchronous rotating frame(dq) is widely applied in grid-connected converters. As axe-cross-couplings exist both in the filter and delay models of dq frame and the cross-couplings interact each other, modeling and decoupling of LCL-filtered grid-connected converter with low switching frequency become much more challenging. To address this issue, based on modeling of LCL-filter grid-connected converters in dq frame with complex vector, a systematic analysis for traditional state feedback and phase compensation is conducted with double-sided frequency response and pole-zero map, where the effects of phase compensation at different positions on phase margin and decoupling effect are revealed. Based on this, an improved decoupling control strategy is proposed to effectively regulate and improve system dynamic performance and ensure good decoupling effect at the same time by respectively designing phase compensations at output of regulator and within state feedback loop. Finally, simulation and experimental results show that the proposed method can provide good decoupling effect and reduce overshoot and settling time effectively.
Proportional integral(PI) control in synchronous rotating frame(dq) is widely applied in grid-connected converters. As axe-cross-couplings exist both in the filter and delay models of dq frame and the cross-couplings interact each other, modeling and decoupling of LCL-filtered grid-connected converter with low switching frequency become much more challenging. To address this issue, based on modeling of LCL-filter grid-connected converters in dq frame with complex vector, a systematic analysis for traditional state feedback and phase compensation is conducted with double-sided frequency response and pole-zero map, where the effects of phase compensation at different positions on phase margin and decoupling effect are revealed. Based on this, an improved decoupling control strategy is proposed to effectively regulate and improve system dynamic performance and ensure good decoupling effect at the same time by respectively designing phase compensations at output of regulator and within state feedback loop. Finally, simulation and experimental results show that the proposed method can provide good decoupling effect and reduce overshoot and settling time effectively.
引文
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[16]Bae B H,Sul S K.A compensation method for time delay of full-digital synchronous frame current regulator of PWM AC drives[J].IEEE Transactions on Industry Applications,2003,39(3):802-810.
[17]邱长青,黄声华,林珍君,等.基于复矢量PI调节器的四象限级联型变频器PWM整流控制策略[J].中国电机工程学报,2015,35(11):2804-2812.Qiu Changqing,Huang Shenghua,Lin Zhenjun,et al.A PWM rectifier control strategy for four-quadrant cascade converters based on complex vector PI regulators[J].Proceedings of the CSEE,2015,35(11):2804-2812(in Chinese).
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[19]Siddique H A B,Ahmad M J R,De Doncker R W.Optimal control and filter sizing of a multi-megawatt medium-voltage voltage-source converter for future grids[C]//IEEE PEDG.Vancouver,Canada:IEEE,2016:1-8.
[20]Harnefors L.Modeling of three-phase dynamic systems using complex transfer functions and transfer matrices[J].IEEE Transactions on Industrial Electronics,2007,54(4):2239-2248.
[21]Kim H,Degner M W,Guerrero J M,et al.Discrete-time current regulator design for AC machine drives[J].IEEE Transactions on Industry Applications,2010,46(4):1425-1435.
[22]Yepes A G,Vidal A,Malvar J,et al.Tuning method aimed at optimized settling time and overshoot for synchronous proportional-integral current control in electric machines[J].IEEE Transactions on Power Electronics,2014,29(6):3041-3054.
[23]Zhang X,Chen P,Yu C Z,et al.Study of a current control strategy based on multisampling for high-power grid-connected inverters with an LCL filter[J].IEEE Transactions on Power Electronics,2017,32(7):5023-5034.
[2]曾正,赵荣祥,杨欢,等.多功能并网逆变器及其在微电网电能质量定制中的应用[J].电网技术,2013,36(5):58-67.Zeng Zheng,Zhao Rongxiang,Yang Huan,et al.A multi-functional grid-connected inverter and its application to customized power quality of microgrid[J].Power System Technology,2013,36(5):58-67(in Chinese).
[3]孙青松,吴学智,唐芬.考虑中点电位平衡的三电平逆变器断续脉宽调制策略研究[J].中国电机工程学报,2017,37(S):177-185.Sun Qingsong,Wu Xuezhi,Tang Fen.Three-level inverter discontinuous pulse-width modulation strategy considering neutral point potential balance[J].Proceedings of the CSEE,2017,37(S):177-185(in Chinese).
[4]王堃,游小杰,王琛琛,等.低开关频率下SVPWM同步调制策略比较研究[J].中国电机工程学报,2015,35(16):4175-4183.Wang Kun,You Xiaojie,Wang Chenchen,et al.Research on synchronized SVPWM strategies under low switching frequency[J].Proceedings of the CSEE,2015,35(16):4175-4183(in Chinese).
[5]曾正,邵伟华,宋春伟,等.电压源逆变器典型控制方法的电路本质分析[J].中国电机工程学报,2016,36(18):4980-4989,5123.Zeng Zheng,Shao Weihua,Song Chunwei,et al.Circuit-based analysis of typical control schemes of voltage-source inverter[J].Proceedings of the CSEE,2016,36(18):4980-4989,5123(in Chinese).
[6]郭小强,贾晓瑜,王怀宝,等.三相并网逆变器静止坐标系零稳态误差电流控制分析及在线切换控制研究[J].电工技术学报,2015,30(4):8-14.Guo Xiaoqiang,Jia Xiaoyu,Wang Huaibao,et al.Analysis and online transfer of stationary frame zero steady-state error current control for three-phase grid-connected inverters[J].Transactions of China Electrotechnical Society,2015,30(4):8-14(in Chinese).
[7]戴鹏,符晓,袁庆庆,等.基于复矢量调节器的低开关频率PWM整流器研究[J].中国电机工程学报,2011,31(21):25-31.Dai Peng,Fu Xiao,Yuan Qingqing,et al.A novel complex state current controller for PWM rectifier at very low switching frequency[J].Proceedings of the CSEE,2011,31(21):25-31(in Chinese).
[8]伍小杰,袁庆庆,符晓,等.基于复矢量调节器的低开关频率同步电机控制[J].中国电机工程学报,2012,32(3):124-129,6.Wu Xiaojie,Yuan Qingqing,Fu Xiao,et al.A novel complex state current controller for synchronous motor at very low switching frequency[J].Proceedings of the CSEE,2012,32(3):124-129,6(in Chinese).
[9]吴为,丁信忠,严彩忠.基于复矢量的电流环解耦控制方法研究[J].中国电机工程学报,2017,37(14):4184-4191,4298.Wu Wei,Ding Xinzhong,Yan Caizhong.Research on control method of current loop decoupling based on complex vector[J].Proceedings of the CSEE,2017,37(14):4184-4191,4298(in Chinese).
[10]Shen J,Schr?der S,Stagge H,et al.Precise modeling and analysis of DQ-frame current controller for high power converters with low pulse ratio[C]//ECCE.Raleigh,NC:IEEE,2012:61-68.
[11]尹靖元,金新民,吴学智,等.基于带通滤波器的LCL型滤波器有源阻尼控制[J].电网技术,2013,37(8):2376-2382.Yin Jingyuan,Jin Xinmin,Wu Xuezhi,et al.Active damping control strategy for LCL filter based on band pass filter[J].Power System Technology,2013,37(8):2376-2382(in Chinese).
[12]杨苓,罗安,陈燕东,等.LCL型逆变器的鲁棒延时补偿并网控制方法及其稳定性分析[J].电网技术,2015,39(11):3102-3108.Yang Ling,Luo An,Chen Yandong,et al.A robust time delay compensated grid-connected control method for LCL-type inverter and stability analysis[J].Power System Technology,2015,39(11):3102-3108(in Chinese).
[13]屈克庆,李文旗,叶天凯,等.基于状态反馈的LCL型逆变器解耦控制策略[J].电工技术学报,2016,31(20):130-138.Qu Keqing,Li Wenqi,Ye Tiankai,et al.State feedback based decoupling control strategy for grid-connected inverter with LCL filter[J].Transactions of China Electrotechnical Society,2016,31(20):130-138(in Chinese).
[14]Dannehl J,Liserre M,Fuchs F W.Filter-based active damping of voltage source converters with LCL filter[J].IEEE Transactions on Industrial Electronics,2011,58(8):3623-3633.
[15]彭秋波,盘宏斌,刘勇,等.LCL型三相并网逆变器双闭环解耦控制器设计[J].电工技术学报,2014,29(4):103-110.Peng Qiubo,Pan Hongbin,Liu Yong,et al.Design of dual-loop decoupling controller in LCL three-phase grid-connected inverter[J].Transactions of China Electrotechnical Society,2014,29(4):103-110(in Chinese).
[16]Bae B H,Sul S K.A compensation method for time delay of full-digital synchronous frame current regulator of PWM AC drives[J].IEEE Transactions on Industry Applications,2003,39(3):802-810.
[17]邱长青,黄声华,林珍君,等.基于复矢量PI调节器的四象限级联型变频器PWM整流控制策略[J].中国电机工程学报,2015,35(11):2804-2812.Qiu Changqing,Huang Shenghua,Lin Zhenjun,et al.A PWM rectifier control strategy for four-quadrant cascade converters based on complex vector PI regulators[J].Proceedings of the CSEE,2015,35(11):2804-2812(in Chinese).
[18]Zhou S Z,Liu J J,Zhou L Y,et al.DQ current control of voltage source converters with a decoupling method based on preprocessed reference current feed-forward[J].IEEE Transactions on Power Electronics,2017,32(11):8904-8921.
[19]Siddique H A B,Ahmad M J R,De Doncker R W.Optimal control and filter sizing of a multi-megawatt medium-voltage voltage-source converter for future grids[C]//IEEE PEDG.Vancouver,Canada:IEEE,2016:1-8.
[20]Harnefors L.Modeling of three-phase dynamic systems using complex transfer functions and transfer matrices[J].IEEE Transactions on Industrial Electronics,2007,54(4):2239-2248.
[21]Kim H,Degner M W,Guerrero J M,et al.Discrete-time current regulator design for AC machine drives[J].IEEE Transactions on Industry Applications,2010,46(4):1425-1435.
[22]Yepes A G,Vidal A,Malvar J,et al.Tuning method aimed at optimized settling time and overshoot for synchronous proportional-integral current control in electric machines[J].IEEE Transactions on Power Electronics,2014,29(6):3041-3054.
[23]Zhang X,Chen P,Yu C Z,et al.Study of a current control strategy based on multisampling for high-power grid-connected inverters with an LCL filter[J].IEEE Transactions on Power Electronics,2017,32(7):5023-5034.