【作者】 李亮；

【导师】 康勇； 段善旭；

【作者基本信息】 华中科技大学 ， 电力电子与电力传动， 2006， 硕士

【摘要】 UPS广泛应用于国民经济的各个领域。本文是针对UPS系统中PFC整流和三电平逆变器的研究。本文PFC采用平均电流控制芯片LT1248,论述了其工作原理,采用了双Boost的新型拓扑,阐述了功率和控制电路的设计方法。推导了电流内环、电压外环的小信号模型,采用串联校正设计了补偿网络。补偿后的电流环增加了内环的带宽,加大了高频段的衰减,抑制了开关噪声,提高了内环的动态性能;补偿后的电压环减小了外环带宽,加大了中频段的衰减,抑制了输出电压次谐波干扰,提高了外环的稳态性能。经过仿真和实验验证,UPS输入端的功率因数提高到90%以上。本文对三电平逆变器的拓扑和控制做了分类。介绍了功率和控制电路的设计方法。比较了单相SPWM各方法的特点。推导了三电平单相逆变器的数学模型,采用了极点配置PID瞬时值反馈的控制策略,论述了PID串联校正的设计方法。仿真分析了参数ζ,ωn,n的取值不同对系统的影响,得出在系统截止频率要求范围内,ζ,ωn,n越大,系统稳态、动态性能越好的结论。分析了PID瞬时值反馈稳态精度不佳的原因,增加了均值PI外环,使输出电压幅值无静差。本文还对数字化PID做了论述,比较了位置式和增量式算法的特点和适用范围,给出了算法流程图。通过仿真和实验验证,逆变器具有良好的稳态和动态性能。本文针对三电平逆变器的中点平衡问题,分析了中点波动的成因和危害,采用了针对三相SPWM控制的载波浮动的中点平衡控制策略,并论述了PFC母线平衡控制与逆变器直流偏磁控制对于中点平衡的作用。更多还原

【Abstract】 UPS is widely used in many applications. This dissertation researches on PFC rectifier and three-level inverter of UPS system.PFC adopts the chip LT1248 with mean current controlling method. The working principle is noted. A novel double Boost topology is proposed and the designing method of power and control circuit is illustrated. The thesis induces the small signal mode of current and voltage loop. Based on that, a compensative network is designed in series. The compensated current loop increases the band width and attenuation in high frequency period. The noise of switch is restrained and the dynamic characteristic improves. The compensated voltage loop decreases the band width and increases the attenuation in middle frequency period. The second harmonic wave is restrained and the steady-state characteristic improves. Through simulating and experiment, the power factor reaches at 90% above.The topology and controlling method of three-level inverter is classified in this paper. The designing method of power and control circuit is introduced. The math mode of three-level single phase inverter is induced after comparing of varies of SPWM methods. The control scheme which uses PID instantaneous feedback control with pole assignment is explained. The parametersζ,ωn,n have different effects on system when their values differ. A conclusion comes out, which expresses the bigger values, the better performance below the systemic cut frequency. Then this PID feedback method’s shortcoming is announced which is bad for the system steady-state precision. To solve this problem, the system adds another PI mean value loop outside. Furthermore, this thesis focuses on the realization of PID digital control. A comparing of location method and increment method shows the different traits and different applications. Arithmetic flows are made for both methods. Through simulating and experiment, it shows that the inverter has satisfied steady-state and dynamic characteristics.The dissertation illustrates the neutral point balance problem of three-phase inverter. The cause and harm of the neutral point fluctuating is analyzed and a strategy which uses the floating carrier to three-phase SPWM controlling is proposed. In addition, the PFC bus balance control and the invert magnetism compensation is used to control the neutral point balance.更多还原