【作者】 唐春森；

【导师】 孙跃；

【作者基本信息】 重庆大学 ， 控制理论与控制工程， 2009， 博士

【摘要】 非接触电能传输(CPT)技术是一种新兴的基于电磁感应原理,综合利用电力电子技术、磁场耦合技术及控制理论,实现用电设备以非电气接触方式从电网获取电能的技术,具有安全、便捷、易维护、可靠性高及环境亲和力强等优点。在CPT系统中,由于原副边的松耦合特性,通常采用谐振的方式提高传输功率,因此软开关谐振变换电路也就成为CPT系统的常见主电路形式。在设计和分析CPT系统时,选定参数下,系统软开关工作点及其稳态特性是设计人员最为关心的问题。但是通过文献检索发现,目前尚无一种系统的方法可以快速确定系统所有可能的软开关工作点的周期及稳态响应波形,人们只能通过繁琐的数值运算去找寻可能的软开关工作点,或者借助仿真软件对系统反复进行仿真分析,既费时又费力。本文针对CPT系统的软开关工作点分析问题,旨在提出一种可适用于一般负载谐振变换器软开关工作点的周期及稳态波形分析方法,并将该方法应用到实际CPT系统的分析与研究中。在研究过程中,作者主要作了以下工作:1.提出了一种软开关工作点精确计算方法基于频闪映射方法及不动点理论建立了可分段线性化的自治振荡非线性系统的通用频闪映射模型。在此基础上,针对CPT系统中广泛应用的电压型及电流型负载谐振变换器,分别建立了它们的周期不动点函数模型及软开关边界条件表达式,推导出了确定负载谐振变换器的软开关工作点周期及稳态波形的解析函数表达式,总结了软开关工作点计算方法的步骤及特点。并以LCR串联谐振电路为例,分析了系统软开关工作点的周期不动点函数曲线与系统参数间的内在联系。2.分析了CPT系统多软开关工作点特性以LCL型CPT系统为例,应用本文提出的负载谐振电路软开关工作点精确计算方法确定了其软开关工作点,并详细分析了各软开关工作点的特性及参数变化对软开关工作点个数的影响,仿真及实验结果验证了理论结果及分析方法的正确性。通过对原副边谐振电压电流波形特性的讨论,发现了多软开关工作点下的一些有趣现象及其潜在应用价值,如系统的次谐波振荡可为低频开关实现高频振荡提供有效的解决途径,而多软开关工作点的功率传输特性差异则可能被用来设计一种新的功率调节器。3.研究了CPT系统谐振点(一种特殊软开关工作点)及其稳定性问题以推拉式CPT系统为例分析了CPT系统多谐振点及其自治振荡稳定性问题。文中给出了CPT系统中谐振点的定义及判断条件,建立了系统的庞加莱映射模型,并根据隐函数及复合函数求导法则,推导出了系统庞加莱映射周期不动点的雅可比矩阵,根据雅可比矩阵的特征值分布情况,即可判断各不动点的自治振荡稳定性。在实例分析中,文中研究了一个存在三个谐振点的推拉式CPT系统,判断了其谐振点的稳定性,并基于PLECS平台对该CPT系统进行了仿真研究,验证了其三个谐振点在定频控制模式下的软开关工作特性,给出了定频控制模式的软启动方法;分析了系统在浮频控制模式下的稳态谐振工作点,验证了三个谐振点的局部稳定性,并研究了拾取端短路解耦控制引起的稳定谐振点之间的相互跳动问题。4.提出了一种新型功率控制策略根据CPT系统多软开关工作点的功率传输特性差异提出了一种新的基于多软开关工作点的功率控制策略,其核心思想就是让系统根据误差反馈信息在其多软开关工作点之间来回切换,从而实现对功率的控制。文中以原副边均串联谐振型CPT系统为例,研究了这种控制策略的工作原理、实现思路以及控制特性等。仿真及实验结果验证了该控制策略的可行性。本文的创新性贡献在于:1.针对CPT系统所有可能的软开关工作点周期及稳态波形的快速准确求解问题,提出了一种基于频闪映射方法和不动点理论的软开关工作点精确计算方法,该方法极大地简化了系统稳态分析过程,并可推广应用于一般负载谐振变换电路;2.针对非接触电能传输系统的高阶非线性特性所带来的多谐振工作点问题,提出了一种基于庞加莱映射模型及其雅可比矩阵的系统谐振点稳定性判据,发现多谐振工作点的存在及其稳定性差异可能引起系统多谐振点跳转现象;3.基于非接触电能传输系统多软开关工作点的功率传输特性差异,提出了一种多软开关工作点功率控制策略,该策略可以在不添加额外辅助开关电路的情况下,通过切换系统工作点,在动态软开关模式下实现传输功率的连续可调。更多还原

【Abstract】 Contactless Power Transfer (CPT) is a novel techonology developed to deliver power contactlessly from power supply to one or more movable loads using modern power electronics, control theory and magnetic coupling techniques. The main advantages of this technology are safe, flexible, easy to maintain, highly reliable and environmentally friendly.In CPT systems, because of the loosely coupling condition between the primary and secondary sides, resonant technology is usually employed to increase power transfer capability. Therefore, soft-switching resonant technology is usually used in the main circuit of a CPT system. In CPT system design and analysis, the soft-switching operating points and their steady-state characteristic are the most concerned points. However, it has been shown from literature reveiew that there is not such one method so far which can accurately and quickly determine all the possible soft-switching operating points and steady-state response waveforms. In order to get all the possible operating points, complicated numerical analysis or repetitive simulation is unavoidable. But both methods are very time-consuming and low efficiency.For the soft-switching operating points analysis of a CPT system, this paper is devoted to proposing a method suitable for analyzing the periods and steady-state response waveforms of all the soft-switching operating points of a common resonant converter. And the method is applied in practical CPT systems.The main works of this paper are as follows.1. Proposed an accurate analysis method for soft-switching operating pointsA general stroboscopic mapping model of an autonomous nonlinear oscillating system which can be piecewise linearized is derived based on stroboscopic mapping method and fixed points theory. And then, both the voltage-fed and current-fed load resonant circuits which widely used in CPT systems are studied respectively. Their periodic fixed point functions and soft-switching boundary condition equations are derived, based on which, the equations for calculating the periods and the steady-state waveforms of the soft-switching operating points have been obtained. The steps and characteristics of the proposed soft-switching operating point analysis method have been summarized briefly. Afterwards, the relationship between the periodic fixed point function and the system parameters has been studied in a LCR series tuned resonant circuit.2. Analyzed the characteristics of multiple soft-switching operating points of a CPT systemThe proposed method has been applied to analyze an LCL-type CPT system. The steady-state characteristics of the soft-switching operating points have been investigated in detail. Bifurcation diagrams are employed to study the influence of the system key parameters on the soft-switching operating points. The theoretical results and the proposed method have been verified by both simulation results and experimental results. More interesting phenomena and potential practical applications have been found by studying the waveforms of multiple soft-switching operating points. For example, the subharmonic oscillation characteristic at the low frequency operating points can be used to achieve high frequency oscillation by relatively low frequency switching. And the power transfer capability difference among the operating points can be used to design a novel power flow controller.3. Analyzed the resonant operating points (a special soft-switching operating point) and their stability of a CPT systemTo study the existence of multiple resonant operating points and their autonomous oscillation stability of a CPT system, a push-pull CPT system has been taken as an example. The definition and stability criterion of resonant operating points in a CPT system have been described. A Poincarémapping model has been built up and its Jacobian matrix has been derived with the implicit function derivative rule and chain rule. Then the stability of the fixed points can be determined according to the eigenvalues of the the Jacobian matrix. It has been used to study an example push-pull CPT system with three resonant operating points. The results have been verified by PLECS simulation results. The steady-state response waveforms of the three resonant operating points under fixed frequency operating mode have been simulated and analyzed. A soft start-up method for fixed frequeny operating mode is proposed to solve the over-voltage problem of the conventional method. The floating frequency operating modes of the three points have also been studied and the results verified their local stability obtained from the Jacobian matrix. Particularly, an operating point jumping phenomenon has been studied when the system is under pick-up short-circuit decoupling control.4. Proposed a novel power flow control methodAs the difference of power transfer capability among the soft-switching operating points is concerned, a novel power flow control method has been proposed. The essential idea is to control the system switching among the selected soft-switching operating points according to the feedback error information. This method has been applied to a series tuned CPT system. The main concerned aspects, such as operation principle, design procedure and control characteristics etc., have been studied in detail. Both simulation results and experimental results have verified the proposed control method.The main contributions of this paper are listed as follows.1. To accurately and quickly explore all possible soft-switching operating points of a CPT system, based on stroboscopic mapping method and fixed points theory, an accurate method for calculating soft-switching operating points has been proposed. This method simplifies the steady-state analysis significantly and can be applied to general load resonant circuits.2. To analyze the multiple resonant operating points of a CPT system brought by its high order nonlinear characteristic, a stability criterion of resonant operating points has been proposed based on the Jacobian matrix eigenvalues of the Poincarémapping model. It is found that the existence of multiple resonant operating points and their stability difference may cause operating points jumping phenomenon in a CPT system.3. Based on the power transfer capability difference among the multiple soft-switching operating points, a Multiple Soft-Switching Points (MSSP) power flow control method has been proposed. The transferred power can be adjusted continuously by switching the soft-switching operating points of the system without any additional switching circuit.更多还原