【作者】 李时华；

【导师】 毛承雄； 陆继明；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2007， 硕士

【摘要】 随着电力电子器件、计算机技术以及现代控制理论的迅速发展,大功率电力电子技术在电力系统中的应用已越来越广泛。在电力传动领域已出现交流传动取代直流传动的趋势。高压大功率变频调速技术是解决传统驱动方式带来的能源浪费问题的最有效手段之一,可实现资源节约,对电力工业可持续发展的战略任务具有重要的现实意义。本文首先介绍了高压变频器的基本组成和工作原理,介绍了几种应用广泛的拓扑结构,比较了几种不同结构的优缺点。同时,本文详细介绍了IGCT器件的特性以及IGCT失效的机理。基于IGCT的中性点箝位型三电平高压大功率变频器中,为了获得6kV输出电压等级,需要IGCT的直接串联。为了研究串联IGCT关断时的暂态特性,本文建立了串联IGCT的关断电流数学模型,该模型考虑了所串联的同一型号半导体开关器件物理特性存在的细微差异。基于上述模型,本文提出了用微分方程研究串联IGCT电路关断均压特性的思路。为了验证该思路的有效性,本文建立了基于串联IGCT斩波电路的关断暂态模型。此外,本文研究了直流环节的时间常数和相间换流间隔时间的配合问题。通过简化实验电路来模拟三电平高压大功率变频器换流过程,实验结果验证了当直流限流电路的时间常数小于PWM调制的相间换流间隔时间时,开关管的di/dt较小。同时对相关问题的后续工作进行了展望。更多还原

【Abstract】 With the rapid development of power electronic devices, computer technology and automatic control theory, high power electronic technology has been widely used in the power system this years. In the mechanical and electrical transmission field, the AC drive system will replace the DC drive system. High voltage and high-power variable frequency drive technology, an effective method to resolve the waste of energy of traditional AC drive system, has practical significance to the sustainable development of power system.This paper introduces the buildup and working principle of the high voltage and high-power inverter at first, also several structures widely used now, and points out the advantages and disadvantages of them. At the same time, this paper introduces the basic characteristic and the failure mechanism of the IGCT. Based on the IGCTs, the series connection of power devices is necessary for obtaining 6kV output voltage in neutral point clamped (NPC) three-level high power medium voltage drives (MVDs). As the process of the transient turn-off is very complex for discussing the transient turn-off characteristics of series connected IGCTs, their corresponding turn-off transient current models are developed with the different performances between the connected IGCTs taken into accounts in this paper. According to the current models, the method using differential equations to study the voltage sharing during IGCTs’turn-off transients is proposed. This paper uses a mathematics method to calculate out the turn-off transient voltage of the connected IGCTs. Consequently, the turn-off transient model based on the chopper circuit is deduced to confirm its efficiency, in which the RC-snubbers of IGCT and stray inductance are analysed. Simulation and experimental results show that the model based on the proposed method can well describe the turn-off voltage sharing of series connected IGCTs.In addition, this paper analyses the turn-on and turn-off di/dt of the IGCT when the time constant of the DC-Link is more than or less than the commutated time between two phases. When the time constant of the DC-Link is less than the commutated time between two phases, low turn-on current decay rate can be observed. On the contrary, the turn-on di/dt will be high,which may cause the devices failure. This paper designs a simplified experimental circuit to simulate the switch commutation of the MVDs, the results confirm the analysis in this paper.更多还原