【作者】 张宇；

【导师】 康勇；

【作者基本信息】 华中科技大学 ， 电气工程， 2005， 博士

【摘要】 三相逆变器作为交流供电电源的主体部分,在办公自动化、医药、通讯及国防等各个方面发挥着及其重要的作用,三相逆变器的并联控制技术以其潜在的巨大市场需求及广泛的应用前景而得到了越来越深入地研究。近年来,高性能的PWM 单相逆变器并联控制技术已经接近成熟,而基于高性能的三相PWM 逆变器构成并联系统正成为广大科技工作者研究的焦点,然而,出于体积和成本的考虑,三相逆变器的滤波电感及输出变压器几乎都采用了三磁柱的铁芯结构,因此三相逆变器的三相间存在着磁路耦合,这使得三相逆变器表现出了与单相逆变器所不同的特性,其建模也因为相间的磁路耦合而比较复杂,因此,目前对于三相逆变器的建模及理论分析通常都忽略了相间的磁路耦合。本文以三相SPWM 逆变器的动态特性及其并联系统为研究对象,将瞬时对称分量变换引入三相逆变器的研究,结合自动控制理论等分析手段,在深入分析SPWM 三相逆变器的动态运行特性的基础上,寻求提高SPWM 三相逆变器并联系统性能的行之有效而又易于实现的控制方案和设计准则。本文紧密结合三相逆变器的研发,首先对实验中出现的逆变器并联系统中死区的环流效应进行了分析,发现传统的逆变器模型由于将死区效应等效为逆变桥输出侧的串联电阻而无法解释这一现象,因此,本文首次将死区效应看作是一种谐波扰动,建立了单相PWM 逆变器基于谐波扰动的数学模型,该模型揭示了影响逆变器输出电压波形质量的因素及瞬时值反馈调节对波形的校正作用,同时,从该模型出发本文进一步建立了单相逆变器并联系统的瞬时环流模型,对谐波环流的产生机理及其抑制进行了研究,并对环流的稳定性进行了讨论。为研究三相逆变器的动态特性,本文借鉴了三相交流电机及三相电力系统的动态分析方法,将瞬时对称分量变换引入到三相逆变器的动态研究中,基于瞬时对称分量变换建立了三相逆变器在K 坐标系中的动态数学模型,通过和abc 静止坐标系及dq0旋转坐标系中的三相逆变器动态数学模型进行比较,发现基于瞬时对称分量的数学模型最为简洁,且瞬时对称分量之间相互解耦,对三相逆变器的动态过程进行求解非常方便,因此本文将瞬时对称分量变换,作为本文分析分析三相逆变器的主要手段。为进一步方便对三相逆变器瞬时对称分量方程的求解,本文讨论了瞬时对称分量的Laplace 变换,以便于在s 域中研究三相逆变器的动态特性。更多还原

【Abstract】 The three-phase inverters, which behave as the main ac power supplies, have played an important role in many areas such as official automatic system, medicine, telecom, national defense, and so on. The parallel systems of three-phase inverters have been researched more and more deeply because of their great markets and wide applications. In recent years, the parallel systems based on high performance PWM single-phase inverter have grown to mature, so the parallel systems of high performance PWM three-phase inverters are taken more attention by the researchers of power supplies. However, the filter inductances and output transformers in three-phase inverters are all three-pole cores for considerations of the cost and size, and this lead to the magnet couples between three phases and different characteristics from single-phase inverters. The dynamic models of three-phase inverters are very complex due to the magnetic coupling, so they are always ignored in the recent researches on three-phase inverters. This dissertation analyses the dynamic performance and the design method of three-phase PWM inverters parallel systems based on the automatic theory and instantaneous symmetric component transformation theory. New systemic theory basis for high quality PWM three-phase inverter design is provided. Novel parallel control schemes are proposed. Firstly, based on the experiments of parallel systems of three-phase inverters, this dissertation analyses the circulating currents caused by the dead time effect. We found that the traditional inverter models could not explain these circulating currents, because the dead-time effects were equivalent to resistant. In fact, the dead time difference between inverters could cause considerable low order harmonic circulating currents. This dissertation established the single-phase inverter model where the dead time effect is considered as a harmonic disturbance. This inverter model interpreted the distortion of inverter output waveform caused by the dead time effect and nonlinear loads, and moreover, the influences of instantaneous voltage feedback regulations on the distortion are researched. From this model, we further established the dynamic model of circulating current between parallel single-phase inverters. Based on the model, the yield of harmonic circulating currents can be explained and then the restrain of them is researched. Furthermore, The stability of circulating current is discussed. To research the dynamic characteristics of three-phase inverters, this dissertation established dynamic model of three-phase inverters in K frame for the first time while referring to the models of three-phase ac motors and three-phase power systems. Compare to the instantaneous models in abc stationary frame and dq0 rotation frame, this model is the simplest and uncoupled, so it is easy to solve the dynamic procedure of three-phase inverters, and it is the main method used in this paper. For the convenience, the Laplace transformation to instantaneous symmetrical components is discussed, and we can study three-phase inverters in s domain. Based on the instantaneous symmetrical components model of three-phase inverters, we researched deeply the dynamic characteristics of three-phase inverters in unbalanced status (such as the single-phase step load) and in fault status (such as the shortcut between phases). Based on the full analytical solution, this paper conclude the facts that lead to the unbalance of three-phase inverters and the restrain of them, which can be referred to when we design and research three-phase inverters. Based on the harmonic disturbance model of single-phase inverters and the instantaneous symmetrical components model of three-phase inverters, this dissertation established for the first time the harmonic disturbance model of three-phase inverters. With this model, we analyzed the dynamic characteristics and the stability of three-phase inverters adopting the instantaneous voltage feedback regulations. The stability judgments of three-phase inverters, which take account of the magnet coupling between phases, are derived. Based on the harmonic disturbance model of three-phase inverters, we further established the dynamic model of circulating currents in three-phase inverters parallel systems. The coupling and stability of three-phase circulating currents are analyzed. The three-phase harmonic circulating currents and the restrain of them are discussed. The zero-sequence circulating currents are a special phenomenon in three-phase inverters parallel systems. Based on the instantaneous zero-sequence component model of three-phase inverters, we found that the magnet coupling between three phases have great influences on zero-sequence circulating currents when the three-pole reactors and transformers are used. These influences are researched comprehensively in this paper.Based on all the above researches on three-phase inverters and their parallel systems, we complete the design and test of 50 kVA and 300 kVA multi-UPS parallel systems. The design considerations of three-phase inverter parallel systems are discussed in this dissertation. Fully considering the intrinsic dynamic characteristics of three-phase inverters, two parallel inverter systems achieved good safety, stability and dynamic quality. At the end, the experiment results are given.更多还原