【作者】 王鑫；

【导师】 刘平；

【作者基本信息】 湖南大学 ， 电气工程， 2023， 硕士

【摘要】 电动汽车、轨道交通、光伏发电和航天航空等领域的发展对电力电子设备提出了更高效率、更高功率密度以及更高可靠性的要求。为了满足上述要求,需要将SiC MOSFET器件进行并联使用,以达到所需的功率等级和热性能。然而,由于生产工艺不成熟以及应用布局不对称,SiC MOSFET器件在并联应用过程中总是不可避免存在热应力和电应力不均衡等问题。另外,SiC MOSFET器件的开关速度快,开关瞬态过程的电流不均衡会产生过大的电应力使得器件失效,而长期的热应力不均衡又会导致各个并联器件间的寿命不一致,使得有的器件会先失效并剧烈加速其他器件失效,极大降低了电力电子设备的安全性与可靠性。为了实现并联分立SiC MOSFET器件的安全可靠运行,平衡并联器件间的热应力差异,本文首先对SiC MOSFET的器件结构和工作原理进行了深入分析,并以型号为C2M0080120D的分立SiC MOSFET器件为研究对象,揭示了SiC MOSFET相关器件特性的变化规律,然后将SiC MOSFET的开关过程进行了详细研究,推导了各个开关阶段的等效电路模型以及数学关系式。在此基础上,建立了并联SiC MOSFET器件的解析模型,并基于Pspice仿真平台搭建了器件并联仿真电路模型,研究了并联器件各项参数不一致对其运行状态的影响规律,为后续并联器件结温均衡控制方案设计提供参考。目前大多数研究均是针对并联器件电流不均衡问题,较少有涉及热应力均衡的研究,而温度又是影响器件安全可靠运行的重要因素。针对上述问题,本文从并联器件结温均衡的角度出发,提出了一种基于驱动电压和驱动电阻调节的并联器件结温均衡控制方法,并设计了可变驱动电压与驱动电阻的栅极驱动电路。同时,在PLECS仿真平台搭建了基于并联SiC MOSFET器件的BUCK变换器仿真模型,在并联器件分别运行在各项参数不一致的情况下,对所提并联器件结温均衡控制方法进行了仿真验证。最后,搭建了分立SiC MOSFET器件并联的实验测试平台。在不同负载电流和不同开关频率等多种实验工况下对并联器件进行测试,并对比分析了加入本文所提出的并联器件结温均衡控制方法前后的稳态结温和漏极电流。实验结果表明,本文所提结温均衡控制方法能够很好地平衡并联器件间的结温不均衡,提升了并联器件的寿命与运行可靠性。更多还原

【Abstract】 Developments in electric vehicles,rail transport,photovoltaic power generation,and aerospace have demanded higher efficiency,higher power density,and higher reliability for power electronics.To meet these requirements,SiC MOSFETs need to be used in parallel to achieve the required power level and thermal perfo rmance.However,due to immature production processes and asymmetric application layouts,SiC MOSFETs are always subject to thermal and electrical stress imbalance s in parallel applications.In addition,the fast switching speed of SiC MOSFETs and the imbalanced current in the switching transient process will generate excessive electrical stress and make the devices fail,while the long-term unbalanced thermal stress will lead to the inconsistent life of each parallel device,making some devices fail first and dramatically accelerate the failure of other devices,which greatly reduces the safety and reliability of power electronics.To achieve safe and reliable operation of parallel discrete SiC MOSFETs and balance the thermal stress difference between parallel devices,this thesis firstly analyzes the device structure and working principle of SiC MOSFETs in-depth,and takes the discrete SiC MOSFET with model number C2M0080120 D as the research object to reveal the variation law of device characteristics relat ed to SiC MOSFETs,then the switching process of SiC MOSFETs is studied in detail,and the equivalent circuit model of each switching stage and the mathematical relationship equation are derived.On this basis,the analytical model of the parallel SiC MOSF ETs was established,and the simulation circuit model was built based on the Pspice simulation platform.The influence law of various parameter inconsistencies on the running state of the parallel devices was studied,which provided a reference for the sub sequent design of the junction temperature balance control scheme of parallel devices.Most of the current research is aimed at the current imbalance of parallel devices,and there are few studies involving thermal stress equalization,while the temperature is an important factor affecting the safe and reliable operation of devices.To address the above problems,this thesis proposes a junction temperature balance control method for parallel devices based on the drive voltage and drive resistance regulation,and designs a gate drive circuit with variable drive voltage and drive resistance from the perspective of junction temperature balance of parallel devices.At the same time,a BUCK converter simulation model based on parallel SiC MOSFETs is built on the PLECS simulation platform,and the proposed parallel device junction temperature balance control method is simulated and verified under the condition that the parallel devices are operated separately with di fferent parameters.Finally,the experimental testing platform of parallel discrete SiC MOSFETs is built.The parallel devices are tested under various experimental conditions such as different load currents and different switching frequencies,and the steady-state junction temperature and drain currents are compared and analyzed before and after adding the junction temperature balance control method proposed in this thesis.The experimental results show that the proposed junction temperature balance control method can well balance the junction temper ature imbalance among the parallel devices,which improves the lifetime and operational reliability of the parallel devices.更多还原