【作者】 赵敏；

【导师】 林桦；

【作者基本信息】 华中科技大学 ， 电气工程， 2022， 硕士

【摘要】 近年来碳化硅(Silicon Carbide,SiC)金属氧化物半导体场效应晶体管(Metal Oxide Semiconductor Field Effect Transistor,MOSFET)凭借其高压、高温、高频、高效的优势成为研究的热点。串联是解决其电压等级不足的主流思想,而不均压是限制串联广泛应用的主要原因。本文针对有源驱动延时均压控制方式,就SiC MOSFET串联均压模型、控制策略以及串联在Buck电路中的应用进行了详细的研究。首先,为准确描述延时对串联器件关断稳态漏源极电压的控制作用,基于N漂移区电荷抽取理论,建立了关断过程的电压方程组,并分析不同负载电流、母线电压、器件参数、对地寄生电容下器件关断稳态漏源极电压差与延时之间的定量关系。利用线性拟合得到两器件电压差与延时的小信号模型,结果表明电压差与延时成正比关系,且比值受负载电流影响很大。将此建模方式应用在多器件串联场合中,提出了基于虚拟器件的多器件串联均压模型。最后通过仿真和实验验证了理论模型的准确性。其次,对有源驱动延时均压控制系统进行建模,分析了传统比例-积分(Proportional-Integral,PI)控制器存在的问题,即在负载电流变化的工作场合下,无法兼顾均压系统的稳定性和动态性能。为了解决这个问题,提出一种能根据负载电流实时调整控制器参数的自适应PI控制方式。将该方式推广到多器件串联系统中,并提出了一种基于虚拟器件的控制策略,实现了对所有串联器件的同时控制和快速均压。最后,将基于自适应有源驱动延时均压的串联SiC MOSFET应用于Buck变换器中,其控制系统包括Buck变换器输出电压的电感电流双闭环控制以及SiC MOSFET的均压控制两部分。详细阐述了该控制系统的整体架构、工作原理、协调及时序问题、两控制系统结构及相互影响,得到了控制系统的模型并设计了控制器参数。仿真和实验验证结果表明该系统在保证整体Buck变换器稳定输出的同时,又能维持内部串联器件的良好均压,说明了本文研究的有源驱动延时均压方式在实际电路应用中的可行性。更多还原

【Abstract】 In recent years,Silicon Carbide(SiC)Metal Oxide Semiconductor Field Effect Transistor(MOSFET)has attracted wide attention due to its advantages of high voltage,high temperature,high frequency and high efficiency,Using devices in series is the main way to solve this problem of insufficient voltage level,but the voltage unbalance has become the main problem that limits its wide application.Based on the active driving signal time delay control,this paper conducts a detailed study on voltage balancing model,control strategy,and application in Buck converter of series-connected SiC MOSFETs.First of all,in order to describe control effect of the delay on the turn-off steady state drain-source voltage of the series-connected device accurately,based on the charge extraction theory of the N drift region,the voltage equations during the turn-off process are established,and the quantitative relationship between the differential voltage and delay time under different device parameters,load current and bus voltage is analyzed.Small-signal model of differential voltage and delay of two series-connected devices is obtained by linear fitting.The results show that the devices’ differential voltage is proportional to the delay time,and the ratio is greatly affected by the load current.On this basis,the modeling method is applied to the occasion of multiple series-connection SiC MOSFETs,and multiple seriesconnection devices model based on virtual device is proposed.Finally,the accuracy of the theoretical model is verified by simulation and experiment.Secondly,the active driving signal time delay control voltage balancing system is modeled.The problems using the traditional Proportional-Integral(PI)controller are analyzed,the result shows that the stability and dynamic performance of the voltage balancing system cannot be taken into account in the working situation where the load current changes.In order to solve this peoblem,an adaptive PI controller is proposed,which can adjust the parameters in real time according to the load current.Extending this method to the system consist of multiple series-connection devices,a control strategy based on virtual devices is proposed in this paper,which can realize simultaneous control and fast balancing for all devices connected in series.Finally,series-connected SiC MOSFETs based on adaptive active driving signal time delay voltage balancing are applied to Buck converter.The control system consists of voltage and current double cosed-loop control for Buck converter’s output voltage and SiC MOSFET’s voltage balancing control.The overall structure,working principle,coordination,timing issues,control structure and the interaction of the two control systems are described in detail.The overall model of the control system is obtained and controller parameters is designed.Simulation and experimental results show that the system can maintain a good voltage balancing of the series-connectd devices while ensuring the stable output of the Buck converter.It proves the feasibility of the active driving signal time delay method studied in this paper in practical circuit applications.更多还原