改进的MMC子模块电容参数设计和均压方法
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摘要
通过对模块化多电平变换器(MMC)的工作原理和主电路结构进行理论分析,推导出其数学模型,研究适用于MMC的脉宽调制技术。在已有的换流器桥臂功率脉动公式基础上,分别对工作时MMC子模块电容瞬时电压的直流和交流分量进行能量分析,推导出子模块电容值的上下限值公式;在最近电平逼近调制方法下,研究电容均压问题,引入延时模块和组内电压差上限,以子模块投入数的改变作为产生触发脉冲的前提,提出一种切实可行的电容电压平衡方法,有效降低功率器件投切频率,达到降低开关损耗的目的。最后,Matlab仿真及硬件实验验证了上述改进方法的有效性和可行性。
Through the theoretical analysis of the working principle and main circuit structure of the modular multilevel converters(MMC), the mathematical model and suitable pulse width modulation methods for MMC is studied.On the basis of the existing power pulsation formula of its phase leg,the direct current and alternating current components of its submodule capacitor instantaneous voltage are studied separately to improve submodule capacitance parameter design method.With the nearest level control method,study of the capacitor voltage balancing is carried out.A delay module and the upper limit of the voltage difference within the group are introduced.The change of numbers of submodules in operation is a precondition to generate the pulses.A scheme to balance the capacitor voltages is proposed to effectively reduce the switching frequency of power devices and switching losses. Finally, the Matlab simulation and experiments are carried out to verify the effectiveness of the improved method.
Through the theoretical analysis of the working principle and main circuit structure of the modular multilevel converters(MMC), the mathematical model and suitable pulse width modulation methods for MMC is studied.On the basis of the existing power pulsation formula of its phase leg,the direct current and alternating current components of its submodule capacitor instantaneous voltage are studied separately to improve submodule capacitance parameter design method.With the nearest level control method,study of the capacitor voltage balancing is carried out.A delay module and the upper limit of the voltage difference within the group are introduced.The change of numbers of submodules in operation is a precondition to generate the pulses.A scheme to balance the capacitor voltages is proposed to effectively reduce the switching frequency of power devices and switching losses. Finally, the Matlab simulation and experiments are carried out to verify the effectiveness of the improved method.
引文
[1]辛业春.基于MMC的高压直流输电系统控制策略研究[D].保定:华北电力大学,2015.
[2]赵成勇,胡静,翟晓萌,等.模块化多电平换流器桥臂电抗器参数设计方法[J].电力系统自动化,2013,37(15):89-94.
[3]谢妍.基于MMC的STATCOM器件选择与控制策略研究[D].武汉:武汉大学,2012.
[4] T Yuan,R Li,0 Alatise,et al.Capacitor Selection for Modular Multilevel Converter[A]. Energy Conversion Congress and Exposition(ECCE)[C].2014:2080-2087.
[5] Barnklau H.Submodule Capacitor Dimensioning for Modular Multilevel Converters[J].IEEE Trans. on Industry Applications,2014,50(3):1915-1923.
[6] Lesnicar A,R Marquardt.An Innovative Modular Multilevel Converter Topology Suitable for a Wide Power Range[A].Power Tech Conference Proceedings[C].2003:23-26.
[7]管敏渊,徐政,屠卿瑞,等.模块化多电平换流器型直流输电的调制策略[J].电力系统自动化,2010,34(2):48-52.
[2]赵成勇,胡静,翟晓萌,等.模块化多电平换流器桥臂电抗器参数设计方法[J].电力系统自动化,2013,37(15):89-94.
[3]谢妍.基于MMC的STATCOM器件选择与控制策略研究[D].武汉:武汉大学,2012.
[4] T Yuan,R Li,0 Alatise,et al.Capacitor Selection for Modular Multilevel Converter[A]. Energy Conversion Congress and Exposition(ECCE)[C].2014:2080-2087.
[5] Barnklau H.Submodule Capacitor Dimensioning for Modular Multilevel Converters[J].IEEE Trans. on Industry Applications,2014,50(3):1915-1923.
[6] Lesnicar A,R Marquardt.An Innovative Modular Multilevel Converter Topology Suitable for a Wide Power Range[A].Power Tech Conference Proceedings[C].2003:23-26.
[7]管敏渊,徐政,屠卿瑞,等.模块化多电平换流器型直流输电的调制策略[J].电力系统自动化,2010,34(2):48-52.