基于随机PWM调制的变流器研究
发布时间：2018-08-16 08:50
【摘要】：PWM技术在变流器中得到越来越广泛的应用,该技术以固定的开关频率控制开关器件的开通和关断,变流器输出的电压电流在开关频率处及开关频率的整数倍附近含有丰富的高次谐波,这些不期望的谐波会降低PWM变流器的电磁兼容品质,产生很强的宽带电磁发射源,导致电磁干扰。针对上述问题,本文以APF变流器为研究平台,引入随机PWM调制技术将集中在开关频率处的高频谐波连续均匀地分布在一个较宽的频率范围内,降低电磁干扰和减小LCL滤波器的体积。本文主要在以下几方面开展了工作:首先,分析二极管中点箝位(Neutral Point Clamped,NPC)型三电平拓扑APF变流器的工作原理,建立数学模型,揭示了网侧电流与交流侧电压之间的数学关系,分析了PWM调制在变流器的作用。其次,介绍了随机PWM调制基本原理,重点介绍了随机开关频率PWM调制技术,并通过一个周期PWM波形的傅里叶展开,得到了随机SPWM调制输出相电压的频谱分布,为后续LCL参数优化设计提供基础。进一步,本文给出随机开关频率PWM调制的设计和实现方法,并针对常规随机频率PWM调制技术存在的问题提出混合随机开关频率调制和基于马尔科夫(Markov)链随机开关频率调制两种改进型调制方法。再次,定性地分析了LCL滤波器各个参数对系统的滤波性能的影响,重点介绍了LCL滤波器各个参数设计方法,并针对固定开关频率和随机开关频率SPWM调制的不同约束条件设计出对应满足并网要求的APF变流器LCL滤波器参数。最后,对固定、随机和两种改进型随机开关频率SPWM调制策略进行仿真,在得到相应的输出相电流频谱后,对得到的不同相电流频谱进行对比和分析,得出采用随机开关频率SPWM调制既可以将集中在开关频率及其倍频处的高次谐波连续均匀地分布在一定的范围内,降低电磁干扰,又可以减小LCL滤波器的电感值,减小滤波器的体积和降低设备成本。
[Abstract]:PWM technology is more and more widely used in converters. The switching devices are switched on and off at a fixed switching frequency. The output voltage and current of the converter contain abundant high-order harmonics near the switching frequency and the integer multiple of the switching frequency. These undesirable harmonics will reduce the electromagnetic compatibility of the PWM converter. In this paper, the APF converter is used as the research platform, and the random PWM modulation technology is introduced to distribute the high frequency harmonics concentrated at the switching frequency in a wide frequency range continuously and evenly, so as to reduce the electromagnetic interference and reduce the volume of the LCL filter. The following work should be carried out: Firstly, the working principle of the three-level topology APF converter with diode-neutral-point-clamped (NPC) is analyzed, the mathematical model is established, the mathematical relationship between grid-side current and AC-side voltage is revealed, and the function of PWM modulation in the converter is analyzed. Secondly, the random PWM modulation base is introduced. In this paper, the random switching frequency PWM modulation technique is mainly introduced, and the spectrum distribution of the output phase voltage of the random SPWM modulation is obtained by the Fourier expansion of a periodic PWM waveform, which provides the basis for the subsequent optimization design of LCL parameters. The problems of machine frequency PWM modulation technology are pointed out. Two improved modulation methods are proposed, which are mixed random switching frequency modulation and Markov chain random switching frequency modulation. Thirdly, the influence of each parameter of LCL filter on the filtering performance of the system is qualitatively analyzed, and the design method of each parameter of LCL filter is emphatically introduced. According to the different constraints of SPWM modulation with fixed switching frequency and random switching frequency, the LCL filter parameters of APF converter are designed to meet the requirements of grid connection. By comparing and analyzing the current spectrum, it is concluded that SPWM modulation with random switching frequency can not only distribute the high-order harmonics concentrating on the switching frequency and its frequency doubling continuously and evenly in a certain range, reduce the electromagnetic interference, but also reduce the inductance value of LCL filter, reduce the size of filter and reduce the cost of equipment.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46
本文编号：2185492
[Abstract]:PWM technology is more and more widely used in converters. The switching devices are switched on and off at a fixed switching frequency. The output voltage and current of the converter contain abundant high-order harmonics near the switching frequency and the integer multiple of the switching frequency. These undesirable harmonics will reduce the electromagnetic compatibility of the PWM converter. In this paper, the APF converter is used as the research platform, and the random PWM modulation technology is introduced to distribute the high frequency harmonics concentrated at the switching frequency in a wide frequency range continuously and evenly, so as to reduce the electromagnetic interference and reduce the volume of the LCL filter. The following work should be carried out: Firstly, the working principle of the three-level topology APF converter with diode-neutral-point-clamped (NPC) is analyzed, the mathematical model is established, the mathematical relationship between grid-side current and AC-side voltage is revealed, and the function of PWM modulation in the converter is analyzed. Secondly, the random PWM modulation base is introduced. In this paper, the random switching frequency PWM modulation technique is mainly introduced, and the spectrum distribution of the output phase voltage of the random SPWM modulation is obtained by the Fourier expansion of a periodic PWM waveform, which provides the basis for the subsequent optimization design of LCL parameters. The problems of machine frequency PWM modulation technology are pointed out. Two improved modulation methods are proposed, which are mixed random switching frequency modulation and Markov chain random switching frequency modulation. Thirdly, the influence of each parameter of LCL filter on the filtering performance of the system is qualitatively analyzed, and the design method of each parameter of LCL filter is emphatically introduced. According to the different constraints of SPWM modulation with fixed switching frequency and random switching frequency, the LCL filter parameters of APF converter are designed to meet the requirements of grid connection. By comparing and analyzing the current spectrum, it is concluded that SPWM modulation with random switching frequency can not only distribute the high-order harmonics concentrating on the switching frequency and its frequency doubling continuously and evenly in a certain range, reduce the electromagnetic interference, but also reduce the inductance value of LCL filter, reduce the size of filter and reduce the cost of equipment.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46
【参考文献】
相关期刊论文 前1条
1 陈国柱,吕征宇,钱照明;典型工业电网谐波及其混合有源滤波抑制[J];电网技术;2000年05期
，本文编号：2185492
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