An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency e...An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency error caused by neutral point voltage ripple and high frequency error introduced by space vector synthesis were both taken into account,and the unified error model of output current ripple was established.By taking continuous and discontinuous modulation strategies as examples,the unified error model was validated through Fourier analysis of the experimental results.The proposed evaluation method will be helpful for the switching sequence optimization and the modulation strategy selection.展开更多
In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control se...In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.展开更多
高速磁浮交通牵引变流器采用24 MVA背靠背三电平有源中点钳位拓扑,其中两台整流器和两台逆变器共用直流母线。该文分析整流侧和逆变侧在不同功率因数下中点电压(neutral point voltage,NPV)偏移机理及不同电压矢量对NPV的具体影响。据此...高速磁浮交通牵引变流器采用24 MVA背靠背三电平有源中点钳位拓扑,其中两台整流器和两台逆变器共用直流母线。该文分析整流侧和逆变侧在不同功率因数下中点电压(neutral point voltage,NPV)偏移机理及不同电压矢量对NPV的具体影响。据此,针对高速磁浮逆变器并联和串联两种模式,建立NPV偏移模型,得到在调制比和功率因数同时变化时NPV的可控区域。为在全速范围保证NPV平衡,提出一种基于平移调制波的协同控制策略。为减轻整流器功率因数和调制比对NPV的影响,采用一种具有相电压半波对称性的载波脉宽调制,并证明其具备NPV自平衡能力。仿真和硬件在环实验表明,所提策略具有NPV恢复到平衡状态所需时间短、可控范围大等优点,可在高速磁浮全速工况下保证NPV平衡。展开更多
采用多电平电路构建的双有源桥(dual active bridge,DAB)DC/DC变换器可适用于更高的电压等级并能显著地提高功率密度及性能。基于九开关管五电平有源中点钳位(five-level active neutral point clamed,5L ANPC)电路构建DAB变换器,消除...采用多电平电路构建的双有源桥(dual active bridge,DAB)DC/DC变换器可适用于更高的电压等级并能显著地提高功率密度及性能。基于九开关管五电平有源中点钳位(five-level active neutral point clamed,5L ANPC)电路构建DAB变换器,消除传统的八开关管5L ANPC电路所存在的电平跳变问题。通过分析开关状态之间的切换过程,选取的零开关状态实现所有高压开关管的软开关运行;通过分析不同开关序列对飞跨电容电压和直流侧中点电压的影响,提出一种飞跨电容电压的平衡控制方法。基于1kW样机的实验结果表明,该文构建的5L ANPC DAB变换器获得了优良的性能。展开更多
基金National Natural Science Foundation of China(Grant Nos.51807140 and 51690183).
文摘An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency error caused by neutral point voltage ripple and high frequency error introduced by space vector synthesis were both taken into account,and the unified error model of output current ripple was established.By taking continuous and discontinuous modulation strategies as examples,the unified error model was validated through Fourier analysis of the experimental results.The proposed evaluation method will be helpful for the switching sequence optimization and the modulation strategy selection.
文摘In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.
文摘高速磁浮交通牵引变流器采用24 MVA背靠背三电平有源中点钳位拓扑,其中两台整流器和两台逆变器共用直流母线。该文分析整流侧和逆变侧在不同功率因数下中点电压(neutral point voltage,NPV)偏移机理及不同电压矢量对NPV的具体影响。据此,针对高速磁浮逆变器并联和串联两种模式,建立NPV偏移模型,得到在调制比和功率因数同时变化时NPV的可控区域。为在全速范围保证NPV平衡,提出一种基于平移调制波的协同控制策略。为减轻整流器功率因数和调制比对NPV的影响,采用一种具有相电压半波对称性的载波脉宽调制,并证明其具备NPV自平衡能力。仿真和硬件在环实验表明,所提策略具有NPV恢复到平衡状态所需时间短、可控范围大等优点,可在高速磁浮全速工况下保证NPV平衡。
文摘虚拟同步机VSG(virtual synchronous generator)通过模拟同步机特性为新能源并网提供惯性和阻尼。然而,电力电子开关器件高频开关过程中可能会发生断路故障,导致输出电流波形严重畸变,影响电网安全稳定运行。针对中点箝位型NPC(neutral point clamped)三电平VSG桥臂故障问题,提出一种中点电压均衡的VSG容错模型预测控制策略。分析NPC三电平VSG单相桥臂故障后运行机理,在开关器件故障后利用直流侧电容组成虚拟桥臂,重构为VSG桥臂故障容错结构。建立故障情况下预测电流模型,重构故障状态空间电压矢量,将直流侧中点电容电压引入容错模型代价函数,减小电容电压波动,实现VSG桥臂故障容错运行。实验结果表明,在开关器件发生故障后,NPC三电平VSG能容错连续运行,验证了所提模型预测容错控制策略的有效性,提高了VSG运行可靠性。
文摘采用多电平电路构建的双有源桥(dual active bridge,DAB)DC/DC变换器可适用于更高的电压等级并能显著地提高功率密度及性能。基于九开关管五电平有源中点钳位(five-level active neutral point clamed,5L ANPC)电路构建DAB变换器,消除传统的八开关管5L ANPC电路所存在的电平跳变问题。通过分析开关状态之间的切换过程,选取的零开关状态实现所有高压开关管的软开关运行;通过分析不同开关序列对飞跨电容电压和直流侧中点电压的影响,提出一种飞跨电容电压的平衡控制方法。基于1kW样机的实验结果表明,该文构建的5L ANPC DAB变换器获得了优良的性能。