Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for power...Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.展开更多
Modular multilevel converters(MMCs) operate in the low modulation index region in many applications.However, when utilized at the low modulation index region, large harmonics appear in the output voltage, which degrad...Modular multilevel converters(MMCs) operate in the low modulation index region in many applications.However, when utilized at the low modulation index region, large harmonics appear in the output voltage, which degrade the performance of the MMC. To improve the harmonic characteristic in the low modulation index, the carrier dynamic overlapping switching frequency optimal pulse width modulation(CDOSFOPWM) method is proposed for the MMC here. The whole modulation index region is divided into three regions: high modulation index region, middle modulation index region, and low modulation index region. The carrier amplitude, carrier overlap ratio, and frequency of triangular carriers are chosen dynamically according to the modulation index region of the modulation signals, to achieve the optimal harmonic characteristic in the whole modulation index region and maintain the switching loss. The number of on-state submodules(SMs) can be calculated by CDOSFOPWM, and the selection of SMs is performed by a reducing switching frequency voltage balancing algorithm. Finally, the proposed method is verified by simulation and experimental results.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
由N个相同H桥功率模块(H-bridge power module,HBPM)组成的传统级联H桥功率放大器(cascaded H-bridge power amplifier,CHB-PA)最多可输出2N+1的电平数,输出电平数直接影响功率放大器的正弦特性和保真性能。在级联HBPM数量相同的情况下...由N个相同H桥功率模块(H-bridge power module,HBPM)组成的传统级联H桥功率放大器(cascaded H-bridge power amplifier,CHB-PA)最多可输出2N+1的电平数,输出电平数直接影响功率放大器的正弦特性和保真性能。在级联HBPM数量相同的情况下,首先提出了一种非对称级联多电平功率放大器(asymmetrical cascaded multilevel power amplifier,ACM-PA);其次,为了与传统CHB-PA有相同HBPM数目的ACM-PA,提出一种虚拟载波移相脉宽调制(virtual carrier phase shift pulse width modulation,VCPS-PWM)策略,将输出电平数提高到6N-3;最后,通过仿真对比验证了所提出的ACM-PA和VCPS-PWM可以显著提高输出电平数,降低负载电流的总谐波失真,提高功率放大器的保真性能。展开更多
Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed c...Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed control of surface-mounted permanent magnet synchronous motor(SPMSM)has been attempted.SPMSM wants a digital inverter for its precise working.Hence,this study incor-poratesfifteen level inverter to the SPMSM.A sliding mode observer(SMO)based sensorless speed control scheme is projected to determine rotor spot and speed of the multilevel inverter(MLI)fed SPMSM.MLI has been operated using a multi carrier pulse width modulation(MCPWM)strategy for generation offif-teen level voltages.The simulation works are executed with MATLAB/SIMU-LINK software.The steadiness and the heftiness of the projected model have been investigated under no loaded and loaded situations of SPMSM.Furthermore,the projected method can be adapted for electric vehicles.展开更多
文摘Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.
基金supported by National Natural Science Foundation of China(No.51477045)
文摘Modular multilevel converters(MMCs) operate in the low modulation index region in many applications.However, when utilized at the low modulation index region, large harmonics appear in the output voltage, which degrade the performance of the MMC. To improve the harmonic characteristic in the low modulation index, the carrier dynamic overlapping switching frequency optimal pulse width modulation(CDOSFOPWM) method is proposed for the MMC here. The whole modulation index region is divided into three regions: high modulation index region, middle modulation index region, and low modulation index region. The carrier amplitude, carrier overlap ratio, and frequency of triangular carriers are chosen dynamically according to the modulation index region of the modulation signals, to achieve the optimal harmonic characteristic in the whole modulation index region and maintain the switching loss. The number of on-state submodules(SMs) can be calculated by CDOSFOPWM, and the selection of SMs is performed by a reducing switching frequency voltage balancing algorithm. Finally, the proposed method is verified by simulation and experimental results.
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Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed control of surface-mounted permanent magnet synchronous motor(SPMSM)has been attempted.SPMSM wants a digital inverter for its precise working.Hence,this study incor-poratesfifteen level inverter to the SPMSM.A sliding mode observer(SMO)based sensorless speed control scheme is projected to determine rotor spot and speed of the multilevel inverter(MLI)fed SPMSM.MLI has been operated using a multi carrier pulse width modulation(MCPWM)strategy for generation offif-teen level voltages.The simulation works are executed with MATLAB/SIMU-LINK software.The steadiness and the heftiness of the projected model have been investigated under no loaded and loaded situations of SPMSM.Furthermore,the projected method can be adapted for electric vehicles.
