【作者】 王军；

【导师】 徐龙祥；

【作者基本信息】 南京航空航天大学 ， 机械设计及理论， 2010， 博士

【摘要】 本文的主要研究工作是围绕磁悬浮轴承三电平开关功率放大器建模及其软开关功率放大器技术展开的。磁悬浮轴承开关功率放大器为非线性系统,现有的开关功率放大器模型上存在许多不足,而且电路中的开关功率器件一直工作在硬开关条件下,存在开关损耗及输出电流干扰等方面问题。论文首先阐述了电流型功率放大器的几种结构类型及其工作原理,采用电路分析方法和电感伏秒平衡原理法分别推导出两电平开关功率放大器和三电平开关功率放大器的输出电流纹波表达式。在分析三电平功率放大器控制原理的基础上,提出了采用等效开关模型方法建立磁悬浮轴承三电平开关功率放大器的数学模型,将功率电路分为两个子电路研究,详细分析了两个子电路的数学模型,并推导出三电平开关功率放大器的数学模型,但该方法不能分析输出电流纹波特性,为解决这一问题,提出了一种基于傅里叶分析的方法来建立三电平开关功率放大器的数学模型,详细分析了利用傅里叶方法建立数学模型的过程,模型仿真与实验结果吻合较好,研究表明,采用等效开关模型方法建立的模型可以有效的反映实际功率放大器的交直流特性;基于傅里叶分析的方法建立的模型不仅可以分析功率放大器的交直流特性,而且能分析输出电流纹波特性,可以从数学模型入手来指导设计功率放大器。最后从推导得到的功率放大器的数学模型出发,分析了电路中各参数的变化对三电平开关功率放大器控制系统的影响。为了减小功率放大器电路中开关损耗,减小输出电流干扰,提出一种新的磁悬浮轴承软开关三电平功率放大器,基于并联谐振直流环节原理,在传统的三电平功率放大器前增加一级辅助谐振电路,使得电路中所有开关管均在零电压或零电流开关的条件下工作,详细分析了并联谐振直流环节三电平功率放大器的工作原理,并给出各个工作模式的电路方程,推导了满足软开关工作条件的电路参数,但该电路控制电路较复杂,为此提出一种改进的磁悬浮轴承软开关三电平功率放大器,分析了改进的软开关三电平功率放大器软开关动作时序、各个工作模式原理及电路数学方程,经数学分析得到改进的电路满足软开关工作条件的谐振电路参数。在分析改进的软开关三电平功率放大器工作原理的基础上,推导了该电路输出电压占空比方程式及输出电流纹波方程式。理论仿真与实验表明,并联谐振直流环节三电平功率放大器所有开关器件均在软开关条件下工作,有效减小了传统的三电平功率放大器开关损耗和输出电流干扰。但改进的软开关三电平功率放大器不仅具有前者电路的优点外,而且减小了开关管电压应力,具有传统的三电平功率放大器输出电流纹波小的优点。应用改进的软开关三电平功率放大器成功地实现了磁悬浮轴承系统的静态悬浮和动态高速旋转试验,试验转速达到30000r/min。软开关三电平功率放大器输出电流基频幅值与硬开关三电平开关功率放大器相比,减小了约40%。更多还原

【Abstract】 This paper focus on three-level power amplifier modeling and its soft switching power amplifier technology in magnetic bearing. The switching power amplifier is a nonlinear system. The existing power amplifier model has some drawbacks and switching devices still work under the hard switching conditions. So switching power amplifier has some problems such as large switching loss and output current interference.Firstly, the several structure types and their working principles of power amplifier are analyzed. By using the method of circuit analysis and the method of inductance voltage-second balance principle, it points out that the use of the three-level switching power amplifier has some advantages in magnetic bearing system. Based on the analysis of the three-level control principle, the mathematical model of the three-level power amplifier is established by using equivalent switch model. The power circuit is divided into two sub-circuits and the whole model of three-level power amplifier can be derived by two sub-circuit models. This method can not analyze the characteristics of output current ripple. In order to slove this problem, the Fourier analysis method is proposed to deduce the three-level power amplifier mathematical model. The simulation results of this model are in excellent agreement with experimental results. These results show that the model using the equivalent model can effectively reflect the actual characteristics of power amplifier. The model based on the method of Fourier analysis can be analyzed not only the characteristics of power amplifier, but also the output current ripple. It can be guide to design the circuit parameters of power amplifier from the mathematical model. Based on the derived model, the effect of control system for three-level power amplifier by changing the circuit parameters is discussed.In order to reduce the switching losses and the output current interference in the power amplifier circuit, a new parallel resonant DC link three-level power amplifier of magnetic bearing is proposed. The auxiliary resonant circuit is added into the traditional three-level power amplifier and it makes all devices zero-voltage switching or zero current switching. The working principles of parallel resonant DC link three-level power amplifier are analyzed. Each of the circuit mode equation and the condition of soft-switching circuit parameters are derived. For this circuit needs more complex control circuit, an improved soft switching three-level power amplifier is proposed. The action mode of each principle and circuit mathematical equation are deduced, circuit parameters of meeting the conditions of soft-switching resonant are derived. Output voltage duty cycle and output current ripple equation are derived by mathematical analysis.Theoretical simulation and experimental results show that switching devices of parallel resonant DC link three-level power amplifier work under all soft-switching conditions. It effectively reduces the traditional three-level amplifier switching losses and output current interference. However, the improved soft-switching three-level power amplifier not only has the former advantages but also reduces the switch voltage stress. It has the same small output current ripple as the traditional three-level power amplifier.Based on this improved soft switching three-level power amplifier, the high speed magnetic bearing stably suspends and runs successfully at 30000r/min. Comparing with hard switching three-level power amplifier, the fundamental frequency current amplitude of soft switching three-level power amplifier reduces by forty percent.更多还原