新能源并网三电平逆变器并联系统中点电位平衡及环流抑制
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摘要
虽然三电平并网逆变器并联系统可以提高功率等级,但存在中点电位不平衡及零序环流问题。文章在分析中点电位波动及零序环流产生机理的基础上,提出了基于双调制波载波脉宽调制(DWMPWM)配合零序环流控制器的综合调制算法。通过PI闭环控制零序环流,将所得到的偏置量注入到调制波之中,并将每相调制波进行正负分解得到两组调制波,增加了零状态占空比的调节自由度,解决了零序环流问题和高调制度及任意功率因数范围内的中点电位不平衡问题;无须进行空间矢量调制(SVPWM)的复杂矢量计算,算法更为简单。在Simulink和RTDS中分别搭建了仿真模型,仿真结果表明,采取双调制波载波配合环流控制器综合调制算法,可以快速地使中点电位趋于平衡,有效抑制零序环流。文章所提算法可用于解决高电压、大功率新能源并网三电平逆变器并联系统中点电位平衡问题及零序环流问题。
The three-level grid-connected inverter parallel system can improve the power level,but there exist two problems which are the midpoint potential imbalance and the zero-sequence circulating current. Based on the analysis of the midpoint potential fluctuation and the mechanism of the zero-sequence circulation(ZSCC), an integrated modulation algorithm based on the doublemodulation-wave carrier-based PWM(DWMPWM)and zero-sequence current controller is then proposed. Through PI closed-loop control of the ZSCC,the obtained offset is injected into the modulation wave. Moreover, two sets of the modulation waves can be obtained by the positive and negative decomposition of each phase modulation wave,which can increase the degree of freedom of the adjustment of the zero-state duty cycle. The ZSCC problem and the neutral point potential imbalance problem of high modulation degree and arbitrary power factor are solved simultaneously,the algorithm is more straightforward without the complex vector calculation of SVPWM. Finally,a simulation model was built in Simulink and RTDS respectively. The simulation results show that the adoption of the double-modulation-wave carrier and the circulation controller integrated modulation algorithm can quickly balance the midpoint potential and effectively suppress the zero-sequence circulating current. Also, the proposed algorithm can be applied to solve the problem of the neutral point potential imbalance and the zero-sequence circulating current in high-voltage and high-power new energy grid-connected three-level inverter parallel system.
The three-level grid-connected inverter parallel system can improve the power level,but there exist two problems which are the midpoint potential imbalance and the zero-sequence circulating current. Based on the analysis of the midpoint potential fluctuation and the mechanism of the zero-sequence circulation(ZSCC), an integrated modulation algorithm based on the doublemodulation-wave carrier-based PWM(DWMPWM)and zero-sequence current controller is then proposed. Through PI closed-loop control of the ZSCC,the obtained offset is injected into the modulation wave. Moreover, two sets of the modulation waves can be obtained by the positive and negative decomposition of each phase modulation wave,which can increase the degree of freedom of the adjustment of the zero-state duty cycle. The ZSCC problem and the neutral point potential imbalance problem of high modulation degree and arbitrary power factor are solved simultaneously,the algorithm is more straightforward without the complex vector calculation of SVPWM. Finally,a simulation model was built in Simulink and RTDS respectively. The simulation results show that the adoption of the double-modulation-wave carrier and the circulation controller integrated modulation algorithm can quickly balance the midpoint potential and effectively suppress the zero-sequence circulating current. Also, the proposed algorithm can be applied to solve the problem of the neutral point potential imbalance and the zero-sequence circulating current in high-voltage and high-power new energy grid-connected three-level inverter parallel system.
引文
[1]张俊,赵宇.三电平变流器中点电位平衡的控制策略研究[J].控制工程,2017,24(7):1454-1460.
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[3]Schweizer M,Kolar J W.Design and implementation of a highly efficient three-level T-type converter for lowvoltage applications[J].IEEE Transactions on Power Electronics,2013,28(2):899-907.
[4]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.
[5]Chen T P.Common-mode ripple current estimator for parallel three-phase inverters[J].IEEE Transactions on Power Electronics,2009,24(5):1330-1339.
[6]郑诗程,胡青松,彭勃.T型三电平拓扑及其中点电位平衡控制策略[J].电力系统及其自动化学报,2017,29(12):63-68.
[7]Zhang Di,Wang F F,Burgos R,et al.Common-mode circulating current control of paralleled interleaved three-phase two-level voltage-source converters with discontinuous space-vector modulation[J].IEEETransactions on Power Electronics,2011,26(12):3926-3935.
[8]张厚升,张磊,姜吉顺,等.两并联三相PWM整流器零序环流抑制与均流控制[J].电力自动化设备,2018,38(2):153-160,168.
[9]Ye Z,Boroyevich D,Lee F C.Modeling and control of zero-sequence current in parallel multi-phase converters[A].Power Electronics Specialists Conference[C].Galway:IEEE,2000.680-685.
[10]邢相洋,陈阿莲,张子成,等.基于改进型零序环流抑制方法的T型三电平并联并网系统[J].中国电机工程学报,2017,37(14):4165-4174.
[11]张子成.T型三电平逆变器并联系统控制策略研究[D]济南:山东大学,2017.
[12]田凯.基于双调制波载波PWM策略的中点电位平衡问题研究[D].哈尔滨:哈尔滨工业大学,2010.
[2]谢路耀,金新民,吴学智,等.基于零序电压注入与调制波分解的三电平脉宽调制策略[J].电工技术学报,2014,29(10):27-37.
[3]Schweizer M,Kolar J W.Design and implementation of a highly efficient three-level T-type converter for lowvoltage applications[J].IEEE Transactions on Power Electronics,2013,28(2):899-907.
[4]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.
[5]Chen T P.Common-mode ripple current estimator for parallel three-phase inverters[J].IEEE Transactions on Power Electronics,2009,24(5):1330-1339.
[6]郑诗程,胡青松,彭勃.T型三电平拓扑及其中点电位平衡控制策略[J].电力系统及其自动化学报,2017,29(12):63-68.
[7]Zhang Di,Wang F F,Burgos R,et al.Common-mode circulating current control of paralleled interleaved three-phase two-level voltage-source converters with discontinuous space-vector modulation[J].IEEETransactions on Power Electronics,2011,26(12):3926-3935.
[8]张厚升,张磊,姜吉顺,等.两并联三相PWM整流器零序环流抑制与均流控制[J].电力自动化设备,2018,38(2):153-160,168.
[9]Ye Z,Boroyevich D,Lee F C.Modeling and control of zero-sequence current in parallel multi-phase converters[A].Power Electronics Specialists Conference[C].Galway:IEEE,2000.680-685.
[10]邢相洋,陈阿莲,张子成,等.基于改进型零序环流抑制方法的T型三电平并联并网系统[J].中国电机工程学报,2017,37(14):4165-4174.
[11]张子成.T型三电平逆变器并联系统控制策略研究[D]济南:山东大学,2017.
[12]田凯.基于双调制波载波PWM策略的中点电位平衡问题研究[D].哈尔滨:哈尔滨工业大学,2010.