【作者】 杨昊；

【导师】 谷雨；

【作者基本信息】 哈尔滨工业大学 ， 电气工程（专业学位）， 2024， 硕士

【摘要】 多电平DC-DC变换器具备开关管电压应力低,升压电感、滤波电容较小等特点,被广泛应用在航天器一次电源的高压母线中,但由于其开关器件较多,故障率也相对于单管变换器较大。若发生短路故障,不仅存在着难以检测与故障定位困难等问题,而且会产生浪涌电流,破坏正常工作的电子元件,对变换器的正常工作产生危害。本文以常作为卫星一次电源的飞跨电容型Boost三电平变换器作为研究对象,针对开关管短路故障,研究了一种快速而有效地判断短路的检测方法,提出了一种在不引入冗余结构的前提下,尽量减小短路冲击电流的容错策略。研究内容具体如下:首先,针对飞跨电容型Boost三电平变换器,分析其工作模态。对其进行小信号建模,推导了传递函数,并进行环路设计。说明了飞跨电容型Boost三电平变换器相对于Boost变换器具有升压电感与滤波电容更小、开关管电压应力低等优势。针对已有的故障检测方法存在检测速度慢、定位故障不准确、检测元件多等问题,通过分析电感电压的正常值与短路后的异常值,结合电感电压与驱动信号的时序关系,给出了一种检测飞跨电容型Boost三电平变换器短路故障与定位故障开关管的方法,该方法兼具快速性与准确性。利用电感磁芯的辅助绕组,可方便地进行电压采样,无需引入多余的传感器。仿真结果表明该方法可在一个开关周期内完成短路故障的诊断。针对直接短路法冲击电流大的缺陷,本文研究了一种降低浪涌电流的柔性软切换策略。该策略的核心逻辑是利用正常开关管的导通-关断状态,通过几个到几十个开关周期逐步降低或升高飞跨电容的电压,最终达到屏蔽飞跨电容的目的。该策略可使得故障切换状态由瞬时改进为渐变,从而较为平缓地释放飞跨电容所存储的能量。仿真结果证明,该策略可有效抑制浪涌电流,降低故障发生后对系统稳定性的冲击。最后,搭建了实物平台,绘制PCB电路板,利用DSP28335作为实验平台,编写控制程序。实验证明,本文提出的容错策略相对于直接短路法可十倍降低冲击电流。更多还原

【Abstract】 Multilevel DC-DC converters are widely used in the high-voltage bus of spacecraft primary power supply due to their low voltage stress on MOS tubes,small boost inductance,and filtering capacitance.However,due to the large number of switching devices,their failure rate is also relatively high compared to single tube converters.If a short circuit fault occurs,it not only poses difficulties in detection and fault localization,but also generates surge currents that disrupt the normal operation of electronic components and pose a threat to the normal operation of the converter.This article takes the flying capacitor Boost three-level converter,which is often used as a primary power source for satellites,as the research object.A fast and effective detection method for short circuit faults in MOS tubes is studied,and a fault-tolerant strategy is proposed to minimize the short-circuit impulse current as much as possible without introducing redundant structures.The specific research content is as follows:Firstly,the topology evolution steps of the flying capacitor Boost three-level converter were introduced,and waveform diagrams were drawn under different duty cycles,introducing the operating modes.We conducted small signal modeling and analyzed its dynamic performance,demonstrating that the flying capacitor Boost three-level converter has advantages over the Boost converter,such as smaller boost inductance and filtering capacitance,and lower switch voltage stress.In response to the problems of slow detection speed,inaccurate fault location,and multiple detection components in existing fault detection methods,this paper analyzes the normal value of inductance voltage and the abnormal value after short circuit,combined with the temporal relationship between inductance voltage and driving signal,and proposes a method for detecting short circuit faults and locating faulty switching tubes in flying capacitor boost three-level converters.This method combines speed and accuracy.By utilizing the auxiliary winding of the inductor magnetic core,voltage sampling can be conveniently carried out without the need for introducing additional sensors.The simulation results show that this method can complete the diagnosis of short circuit faults within one switching cycle.This paper studies a flexible soft switching strategy to reduce surge current in response to the drawback of high surge current in direct short-circuit method.The core logic of this strategy is to use the conduction off state of the remaining three normal switching tubes,gradually reduce or increase the voltage of the flying capacitor through several to dozens of switching cycles,and ultimately achieve the goal of shielding the flying capacitor.This strategy can improve the fault switching state from instantaneous to gradual,thus releasing the energy stored in the flying capacitor more smoothly.The simulation results demonstrate that this strategy can effectively suppress surge currents and reduce the impact on system stability after faults occur.Finally,a physical platform was built for this study,PCB circuit boards were drawn,and control programs were written using the DSP28335 microcontroller.After power on experiments,it has been proven that the fault-tolerant strategy proposed in this article can reduce the impulse current by ten times compared to the direct short-circuit method.更多还原