应用于STATCOM的级联U-Cell拓扑直流电压控制策略
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摘要
采用级联U-Cell拓扑相比传统级联H桥拓扑,静止同步补偿器(static synchronous compensator,STATCOM)使用的开关器件更少,损耗更小,设备经济性更高。但级联U-Cell同样存在直流侧电容电压不平衡的问题,严重时可使系统无法运行。针对该问题,首先搭建级联U-Cell拓扑数学模型,详细分析了电容充放电以及实现相内电容电压平衡的工作原理。基于此,提出了一种冗余开关状态轮换与基于开关状态叠加有功电压矢量相结合的控制策略,并将该策略应用推广到任意奇数电平。该策略能够使器件损耗更加均匀,实现了级联U-Cell相内电容电压平衡控制,提高了系统的可靠性。最后分别搭建了基于五电平级联U-Cell拓扑的STATCOM仿真和实验平台,验证了所述理论及控制策略的正确性。
Compared with traditional cascade H bridge topology,cascaded U-Cell topology of static synchronous compensator( STATCOM) has few switch devices,low loss and good economic value. However,cascaded U-Cell also exists the problem of unbalanced capacitor voltage,which affects the system reliable operation in severe cases. A mathematical model of cascaded U-Cell is built for this problem,and the principle of capacitor charging and phase-capacitor voltage balance are analyzed in detail. Based on this,a control strategy combining redundant switching states rotation and active voltage vector superimposed by switching state is put forward in the paper,of which is extended to arbitrary odd number level.This strategy can make the device loss more uniform,achieved the balance of the capacitor voltage in the cascade U-Cell,and improve the reliability of the system. Finally,the simulation and experiment platforms of STATCOM based on five-level cascaded U-Cell topology are built to verify the correctness of the theory and control strategy.
Compared with traditional cascade H bridge topology,cascaded U-Cell topology of static synchronous compensator( STATCOM) has few switch devices,low loss and good economic value. However,cascaded U-Cell also exists the problem of unbalanced capacitor voltage,which affects the system reliable operation in severe cases. A mathematical model of cascaded U-Cell is built for this problem,and the principle of capacitor charging and phase-capacitor voltage balance are analyzed in detail. Based on this,a control strategy combining redundant switching states rotation and active voltage vector superimposed by switching state is put forward in the paper,of which is extended to arbitrary odd number level.This strategy can make the device loss more uniform,achieved the balance of the capacitor voltage in the cascade U-Cell,and improve the reliability of the system. Finally,the simulation and experiment platforms of STATCOM based on five-level cascaded U-Cell topology are built to verify the correctness of the theory and control strategy.
引文
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[13] QIANG S,WENHUA L. Control of a cascade STATCOM with star configuration under unbalanced conditions[J]. IEEE Transactions on Power Electronics,2009,24(1):45.
[14] LEE T C,CHEN C H,WANG W C,et al. A flexible DC voltage balancing control based on the power flow management for starconnected cascaded H-bridge converter[J]. IEEE Transactions on Industry Applications,2016,52(6):4946.
[15] SUMMERS J T,BETZ E R,MIRZAEVA G. Phase leg voltage balancing of a cascaded H-Bridge converter based STATCOM using zero sequence injection[C]//13th European Conference on Power Electronics and Applications,Barcelona,2009.
[16]季振东,赵剑锋,孙毅超,等.零序和负序电压注入的级联型并网逆变器直流侧电压平衡控制[J].中国电机工程学报,2013,33(21):9.JI Zhendong,ZHAO Jianfeng,SUN Yichao,et al. DC voltage balancing control for cascaded grid-connected inverters by injecting zero-sequence and negative-sequence voltages[J]. Proceedings of the CSEE,2013,33(21):9.
[2] BETZ R E,SUMMERS T,FURNEY T. Symmetry compensation using a H-bridge multilevel STATCOM with zero sequence injection[C]//Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting,Tampa,FL,2006.
[3] SONG W,HUANG A Q. Fault-tolerant design and control strategy for cascaded H-Bridge multilevel converter-based STATCOM[J].IEEE Transactions on Industrial Electronics,2010,57(8):2700.
[4] SAU S,FERNANDES B G. Cascaded U-Cell multilevel converter for STATCOM applications[C]//2015 17th European Conference on Power Electronics and Applications,Geneva,2015.
[5]王志冰,于坤山,周孝信,等. H桥级联多电平变流器的直流母线电压平衡控制策略[J].中国电机工程学报,2012,32(6):56.WANG Zhibong,YU Kunshan,ZHOU Xiaoxin,et al. DC bus voltage balance control strategy of H bridge cascaded multilevel converter[J]. Proceedings of the CSEE,2012,32(6):56.
[6] BALIKCI A,AKPINAR E. A three-phase four-wire statcom with reduced number of switches for unbalanced loads[C]//10th IET International Conference on AC and DC Power Transmission,Birmingham,2012.
[7] BALIKCI A,AKPINAR E. A novel multilevel converter used for three phase STATCOM under unbalanced load[C]//International Aegean Conference on Electrical Machines and Power Electronics and Electromotion,Joint Conference,Istanbul,2011.
[8]杨擎. H桥级联型STATCOM直流侧电压平衡策略研究[D].徐州:中国矿业大学,2015.
[9]唐剑波. STATCOM控制策略与可靠性研究[D].徐州:中国矿业大学,2015.
[10]徐榕,于泳,杨荣峰,等. H桥级联STATCOM直流侧电容电压平衡控制方法[J].电力自动化设备,2015,35(5):15.XU Rong,YU Yong,YANG Rongfeng,et al. H bridge cascaded STATCOM DC side capacitor voltage balance control method[J].Electric Power Automation Equipment. 2015,35(5):15.
[11]田铭兴,阎宏,赵雨欣,等.级联H桥SVG直流侧电容电压平衡控制方法[J].电网技术,2013,37(9):2632.TIAN Mingxing,YAN Hong,ZHAO Yuxin,et al. A balancing control method of DC capacitor voltage for cascaded H-Bridge SVG[J]. Power System Technology. 2013,37(9):2632.
[12]王松,谈龙成,李耀华,等.链式星型STATCOM补偿不平衡负载的控制策略[J].中国电机工程学报,2013,33(27):20.WANG Song,TAN Longcheng,LI Yaohua. Control strategy for unbalanced load compensation of chain like STATCOM[J]. Proceedings of the CSEE. 2013,33(27):20.
[13] QIANG S,WENHUA L. Control of a cascade STATCOM with star configuration under unbalanced conditions[J]. IEEE Transactions on Power Electronics,2009,24(1):45.
[14] LEE T C,CHEN C H,WANG W C,et al. A flexible DC voltage balancing control based on the power flow management for starconnected cascaded H-bridge converter[J]. IEEE Transactions on Industry Applications,2016,52(6):4946.
[15] SUMMERS J T,BETZ E R,MIRZAEVA G. Phase leg voltage balancing of a cascaded H-Bridge converter based STATCOM using zero sequence injection[C]//13th European Conference on Power Electronics and Applications,Barcelona,2009.
[16]季振东,赵剑锋,孙毅超,等.零序和负序电压注入的级联型并网逆变器直流侧电压平衡控制[J].中国电机工程学报,2013,33(21):9.JI Zhendong,ZHAO Jianfeng,SUN Yichao,et al. DC voltage balancing control for cascaded grid-connected inverters by injecting zero-sequence and negative-sequence voltages[J]. Proceedings of the CSEE,2013,33(21):9.