共查询到20条相似文献,搜索用时 328 毫秒
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由于在交-直-交电压型的双三电平SVPWM矢量控制系统中整流器和逆变器均采用三电平空间矢量PWM调制,因而不可避免地存在直流侧中点电位波动问题,本文对三电平逆变器和三电平整理器分别进行直流侧中点电位波动分析,提出抑制直流侧中点电位波动的控制方法,在文章的最后给出了仿真结果和实验结果并分别对其进行了分析。 相似文献
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考虑到三电平NPC逆变器在中高压大容量工况下的运用,阐述了七段对称式SVPWM调制方法。在SVPWM调制下三电平NPC逆变器中点电位将产生波动,详细分析了中点电位波动产生的机理,以及在一个开关周期内,通过控制冗余小矢量对中点电位波动的调整能力,同时分析了不平衡负载对中点电位波动的影响。为了解决中点电位波动的问题,提出了一种基于模糊逻辑的平衡三电平NPC逆变器中点电位的SVPWM调制方法。最后通过仿真验证了该方法的有效性。 相似文献
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针对T型三电平逆变器中点电位不平衡问题,提出一种基于无差拍控制的T型三电平逆变器中点电位平衡方法。首先建立中点电位变化量、相电流和开关矢量占空比的数学关系,在此基础上引入描述小矢量调节中点电位能力的评价指标,当两个小矢量同时存在时,通过比较两个小矢量的调节能力选择不同的开关调制方式。根据给出的数学关系和空间矢量调制方式,提出中点电位平衡无差拍控制模型,对调节能力较强的小矢量占空比进行调整,可以快速实现中点电位平衡控制。仿真和实验结果表明该方法具有良好的中点电位平衡控制性能,有效抑制了中点电位波动,同时减小了输出电压电流谐波。 相似文献
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Satoshi Ogasawara Tadashi Sawada Keiichi Abe Hirofumi Akagi 《Electrical Engineering in Japan》1993,113(5):93-101
This paper describes a vector control system of an induction machine using a neutral-point-clamped voltage-source inverter (NPC-VSI) that is one of the double series-connected inverters. The NPC-VSI is able to output five-level step-shaped line-to-line voltage without output transformers or reactors, and it may reduce harmonic currents corresponding to torque ripples. However, the NPC-VSI has a problem in that excessive high voltage is applied to switching devices when a neutral point of two dc capacitors of the NPC-VSI varies from the center of the dc link voltage, because the neutral point is floating. This paper proposes also a current controller to which the space vector theory is applied. This can reduce harmonic currents to one-fourth those of a conventional voltage-source inverter using six switching devices, and regulate the neutral point potential within a preset range. To simplify the current controller, information about voltage space vectors is given from the vector controller to the current controller. The validity of the current controller is confirmed by a prototype using an induction machine of 2.2 kW. 相似文献
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Three-level neutral point clamped (NPC) inverter is a widely used topology of multilevel inverters. However, the neutral point fluctuates for certain switching states. At low modulation index, the fluctuations can be compensated using redundant switching states. But, at higher modulation index and in overmodulation region, the neutral point fluctuation deteriorates the performance of the inverter. This paper proposes a simple space vector pulsewidth modulation scheme for operating a three-level NPC inverter at higher modulation indexes, including overmodulation region, with neutral point balancing. Experimental results are provided 相似文献
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Discrete space vector modulation and optimized switching sequence model predictive control for three-level voltage source inverters 下载免费PDF全文
Sheng Zhou Minlong Zhu Jiaqi Lin Paul Gistain Ipoum‑Ngome Daniel Legrand Mon‑Nzongo Tao Jin. 《电力系统保护与控制》2023,8(4):1065-1080
This paper proposes a discrete space vector modulation and optimized switching sequence model predictive controller for three-level neutral-point-clamped inverters in grid-connected applications. The proposed strategy is based on cascaded model predictive control (MPC) for controlling the grid current while maintaining the capacitor voltage balanced without weighting factor. To enhance the closed-loop performance, the external MPC evaluates 19 basic and 138 virtual vectors (VV) of the proposed space vector method. The optimal control voltage is then selected using an extended deadbeat method to reduce the execution time of the proposed control algorithm. By using the discrete space vector modulation principle, the VV are synthesized based on switching sequence (SS) and are divided into negative and positive SSs considering their impact on the neutral point (NP) potential. The inner MPC evaluates both types of SSs and selects the one that keeps the capacitor voltage balanced. Various controllers are evaluated and compared against the proposed control strategy. The results show that the proposed strategy improves performance without weighting factor, while maintaining a total harmonic distortion of current to be less than 2%. Compared to the modulated MPC which provides the same fxed switching frequency, the proposed controller reduces the computational burden by over 50% while also providing better NP voltage balance accuracy 相似文献
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一种新的三电平中点电位滞环控制法 总被引:17,自引:6,他引:17
该文针对三电平中点电位平衡原理提出了一种中点电位的滞环控制方法,该方法根据当前的PWM组合和各相输出电流方向判断出中点电流方向,通过滞环比较的方式得到中点电压偏向,并由此判断当前PWM对中点电位的作用,将当前的PWM组合中可以实现中点电位平衡的组合重新分配使之有利于中点电位的平衡。该方法独立于具体的PWM调制模式,因此可以胜任各种PWM调制模式下的中点电位调整。而且也可通过调整滞环宽度的方法来调整中点电位的允许波动和开关管开关次数。该文以特定谐波消除PWM方法(SHEPWM)为例,仿真和实验结果显示了很好的中点平衡效果。该方法对三电平中点电位平衡上具有通用性。 相似文献
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在降低NPC式三电平逆变器中点电位波动问题时,传统的VSVPWM算法未考虑直流侧电容电压非对称情况。为此,需从理论上探讨对称时的虚拟矢量形式是否适用于非对称状态下的各虚拟矢量。提出了具有中点电位非对称控制的VSVPWM技术,并在引入中点电位不平衡度的基础上通过改进零矢量的持续作用时间实现直流侧电容电压非对称控制。该方法具有较宽的调制比适用范围,并能够精确地控制直流侧电容电压,提高线电压质量,有效降低中点电位波动幅度。仿真和实验结果验证了该方法的有效性和优越性。 相似文献
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一种新的基于混合空间矢量调制的三电平逆变器直流侧电容电压平衡研究 总被引:3,自引:0,他引:3
针对二极管中点钳位型(neutral point clamped,NPC)三电平逆变器容易造成直流侧电容电压不平衡问题,提出一种新的中点电位平衡控制方法。在该方法中,采用分扇区精细控制,对不同的小矢量设置不同的时间分配因子,以增加相应正或负小矢量对中点电流的控制能力。对于正负小矢量不能成对出现的扇区,根据相电流的变化情况,使调制在传统算法和基于虚拟矢量的算法之间切换,从而削弱中矢量对中点电流不可控的影响。仿真和实验证实了该方法的正确性和有效性。 相似文献
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