【作者】 佟强；

【导师】 徐殿国； 张东来；

【作者基本信息】 哈尔滨工业大学 ， 电力电子与电力传动， 2010， 博士

【摘要】 航天器中载荷设备的性能在不断提高,对供电电源品质的要求也越来越高。目前使用的模拟电源技术已不能很好地满足其要求,主要表现在两个方面:首先是传统的拓扑结构无法满足新型用电设备的需求。目前航天用DC-DC模块多采用正激、反激或者推挽拓扑,这些拓扑不具备多路精确稳压输出能力,也不适合低压大电流应用。它们的反馈方式为光耦反馈或磁反馈,光耦器件可靠性差,容易受环境干扰。磁反馈电路复杂,带宽较低;其次,模拟电源控制芯片功能单一,不具备通讯、监测和电源管理功能,容易受环境影响产生参数漂移,造成不稳定工作甚至损坏。可见,电源已经成为制约航天器平台发展的瓶颈。本文研究目标首先就是从拓扑结构和控制器两方面对现有的航天器DC-DC电源技术进行改进,使其满足未来航天器系统发展的需求。本文采用具有中间母线的两级拓扑结构,前级采用开环工作的推挽拓扑,后级采用多个同步Buck拓扑实现多路精确稳压输出。每路同步Buck在后级独立闭环调节,避免了由隔离反馈器件带来的问题,因此这种拓扑结构适合多路精确输出,并且还具备低压大电流输出的能力。此拓扑结构优化、效率高,适用于大部分航天器中小功率电源。本文采用一款自主研发的数字电源控制芯片完成对此拓扑的控制,以三路输出电源为例研制了一款满足航天器指标要求的数字控制电源模块,为后续研究提供了验证平台。数字电源芯片通常都不具备大电流驱动能力,无法直接驱动功率开关。本文对传统的变压器隔离驱动电路进行改进,提高了驱动电路的响应速度。此驱动电路解决了传统变压器驱动电路存在的缺陷,在输入PWM信号占空比快速变化时仍能进行准确跟踪,为实现数字电源控制的准确性和快速性提供保障。研究了多相Buck拓扑参数和相位数的优化设计方法,建立了相位数和输入输出电流纹波的对应关系。基于此方法,采用数字电源芯片完成对多相Buck拓扑的控制,并在稳态性能和动态性能两方面与传统的单相Buck拓扑进行对比。为了提高数字DC-DC电源的动态响应能力,在数字控制器的基础上加入模拟补偿电路构成数模混合补偿器,显著提升了电源系统控制环路的相角裕量,达到高阶补偿器的补偿效果,满足高速负载点电源的需求。对阻抗负载下电源环路特性进行预估,分析了大容量电容组的电容量和等效串联电阻(ESR)对电源环路特性的影响,给出了量化的计算方法。在变换器输出端并联大容量电容组的情况下重新设计补偿器使电源达到较好的性能。采用理论分析和实验结合的方法对Buck型DC-DC变换器输出阻抗的小信号模型、影响因素及优化设计方法进行研究,为制定分布式电源系统中变换器的阻抗标准提供了参考依据。本文给出了一种实用的电流扰动测试法可以测量变换器的输入、输出阻抗以及级联变换器的阻抗比。采用此方法对本文搭建的一个级联式DC-DC变换器系统的输入输出阻抗以及阻抗比进行测量,并根据阻抗比禁止区对系统的稳定性进行判断。更多还原

【Abstract】 The increasing performance of load equipment in spacecraft has significantly increased the requirement for high quality power supplies. However, the off-the-shelf power supplies with analog controllers are difficult to meet this requirement. There are mainly two drawbacks: first, the topology of the power supply can not meet the requirement for new load equipment. Topologies such as Forward, Flyback and Push-pull are now widely used in the DC-DC converters for the spacecraft. These topologies are not capable of supplying multiple outputs with precisely regulated voltage and they cannot handle the application with low-voltage high-current as well. Moreover, the feedback methods for these topologies normally use optical coupler feedback or magntic feedback. Optical coupler does not have high reliability, and its current transfer ratio drifts with the changing of the temperature. Magnetic feedback circuit is complicated and the bandwidth is low. Second, analog DC-DC controllers can not realize communication, monitoring and power management functions. They are susceptible to the interference of the working environment, and their parameters are llikely to drift. This will make the converters unstable or even cause them damage. Therefore, power supplies have become the bottleneck that limits the development of the spacecraft platform.One of the main goals of this dessertation is to improve the structure of the current DC-DC converters for the spacecraft in the aspects of topology and controller, so that it can meet the requirement for the future spacecraft. A two stage topology with intermediate DC bus is adopted. Open-loop Push-pull topology is adopted for the first stage. Several parralleled synchronous Buck converters are used for the second stage for the multiple outputs. Since each Buck converter is regulated independently, it eliminates the problems brought by the isolated feedback devices. So this topology can provide mutliple accurate outputs and has low-voltage high-current handling capability. This topology has an optimized structure and can achieve high efficiency. Thus it is suitable for most small and medium rating power supplies in the spacecraft. Furthermore, a digital controller chip for this topology is proposed and developed. A three output DC-DC converter is built here, which aims at providing a platform for the futher research.Digital controllers usually can not drive MOSFETs because they can not provide high trasient currents. An improved transformer coupled gate driver is proposed in this dissertation. It solves the defects caused by the conventional transformer coupled gate driver scheme. When the duty cycle of the input PWM signal changes drastically, the output of the driver can follow this signal rapidly and accuratly. This proposed driver scheme can be widely used in the high frequency switching power supply and motion control applications.An optimized design method for the topology parameters and the phase number of a multi-phase Buck converter is researched. Relationship between the phase number and the input/output current ripple is derived. Based on the proposed method, a multi-phase Buck converter is controlled by a digital controller chip. The steady-state performance and dynamic performance are compared with a traditional single-phase Buck converter.To improve the dynamic performance of the DC-DC converter., an analog compensation circuit is added into the digital control loop. It can improve the control loop phase margin and get the same compensation performance which is normaly achieved by using a high order compensator. So the peak to peak output voltage deviation caused by the changes of load or line voltage can be decreased to achieve a high quality Point-of-Load (POL) converter.The loop gains of DC-DC converters with load impedance is predicted. The influence of the large-capacitance capacitor and its equivalent series resistor (ESR) to the loop gain of the DC-DC converters is analyzed. A method to calculate a new loop gain for the DC-DC converters is derived. The compensator can be revised to improve the loop performance when a large-capacitance output capacitor is used..In this paper small-signal modeling, effect factors and optimized design methods for the output impedance of Buck type DC-DC converters in continuous conduction mode (CCM) are investigated theoretically and verified in experiment. The results will provide references for the standard of setting converters’impedance. A practical impedance measurement approach by using an external small-signal sinusoidal perturbation current is proposed. It can be used to measure the input and output impedance as well as the impedance ratio of cascased converter systems. A simple cascaded converter system is built and the impedance ratio between the source converter and the load converter is measured. According to the concept of the forbidden region, the stability of the system is analyzed.更多还原