多电平变换器热管理不平衡相关技术研究

发布时间：2019-06-04 00:29

【摘要】：随着国家节能减排的需求进一步提高,工业生产、航空航天、交通运输、高压柔性输电等场合对变换器的电压等级提出了新的要求。多电平变换器能够解决功率器件耐压等级与变换器电压等级之间的矛盾,输出波形好,容错性能高,各种新型多电平变换器拓扑及调制策略层出不穷。对于多电平变换器,功率器件数目大幅增加,变换器输出开关状态组合数目随着电平数呈立方增长,且存在大量的冗余开关状态组合。器件的损耗功率不平衡度因此对应增加。原本采用理想的周期性正弦脉宽调制策略(理想的正弦输出电流和电网电压、稳定的系统参数、稳定无波动的直流侧电压、固定开关频率的周期性调制策略等)对变换器中功率器件损耗功率进行分析和计算的方法不再适用。本文以典型功率器件IGBT及反并联二极管为研究对象,基于数学拟合数据的方法,通过MATLAB/Simulink软件建立了IGBT及反并联二极管损耗功率简化通用计算模型,考虑了结温等因素的影响,结合变换器的拓扑及调制策略进行仿真,根据器件相关的参数值,计算变换器中各个功率器件的损耗功率。此方法相当于采用离散的方式,根据器件每个离散时间段的状态(通态、断态),结合器件之前离散时间段的状态,判断每个离散时间段内器件的动作(保持通态、保持断态、开通或者关断)及对应产生的损耗能量。此模型更为简单通用,且对于新型多电平拓扑和调制策略具有良好的扩展性,有利于辅助新型多电平变换器进行损耗功率计算,为产品化降低成本,提高器件的寿命及可靠性。模型预测控制是近年来比较受到关注的调制策略。基于一种应用于级联H桥STATCOM系统的快速模型预测控制算法,结合之前建立的损耗功率计算模型,进行了计算,定量分析了电网电压、控制时间和开关损耗权重系数等参数改变对器件损耗功率的影响,为设备产品化热设计提供了参考范围及典型值。以此调制策略为例,从损耗不平衡方面进行了评价和衡量。最后,针对多电平变换器中器件损耗功率不平衡的现象,对热电制冷器件应用于多电平变换器冷却进行建模和研究。功率器件的寿命与其结温幅值、结温波动范围、结温平均值、模块键合线直径、器件电流和阻断电压等因素都有紧密的关系。目前多电平变换器多采用一种冷却方式,功率器件损耗不均就会造成结温分布不均,可能造成成本浪费或者器件寿命和可靠性降低等问题。热电制冷器件易操控、免维护,可以作为一种补充冷却方式,减少功率器件结温波动,降低功率器件工作结温,甚至是当器件过热时,强制冷却的一种补充方式。本文深化分析了热电制冷器件的能量交换机理,建立了更精确的热电制冷器件数学模型,有利于热电制冷器件控制电源的研发,实现温度精确控制,为今后将此冷却方式应用于多电平变换器产品打下基础。
[Abstract]:With the further improvement of the national demand for energy saving and emission reduction, the voltage level of the converter has been put forward new requirements for industrial production, aerospace, transportation, high voltage flexible transmission and other occasions. The multi-level converter can solve the contradiction between the voltage level of the power device and the voltage level of the converter. The output waveform is good, the fault-tolerant performance is high, and a variety of new multi-level converters topology and modulation strategies emerge in endlessly. For multilevel converters, the number of power devices increases greatly, and the number of output switching state combinations increases with the level, and there are a large number of redundant switching state combinations. The loss power imbalance of the device therefore increases correspondingly. The ideal periodic sinusoidal pulse width modulation strategy (ideal sinusoidal output current and grid voltage, stable system parameters, stable DC side voltage, The periodic modulation strategy of fixed switching frequency, etc.) is no longer applicable to the analysis and calculation of the loss power of power devices in the converter. In this paper, taking the typical power device IGBT and anti-parallel diode as the research object, based on the method of mathematical fitting data, the general calculation model of IGBT and anti-parallel diode loss power is established by MATLAB/Simulink software. Considering the influence of junction temperature and other factors, combined with the topology and modulation strategy of the converter, the loss power of each power device in the converter is calculated according to the parameters related to the device. This method is equivalent to the discrete method, according to the state of each discrete time period of the device (on state, break state), combined with the state of the discrete time period before the device, to judge the action of the device in each discrete time period (keep on state, keep off state, Turn on or off) and the corresponding loss of energy. This model is more simple and general, and has good expansibility for the new multi-level topology and modulation strategy, which is helpful to assist the loss power calculation of the new multi-level converter, reduce the cost for the production, and improve the life and reliability of the device. Model predictive control is a modulation strategy that has attracted much attention in recent years. Based on a fast model predictive control algorithm for cascade H-bridge STATCOM system, combined with the loss power calculation model previously established, the power grid voltage is quantitatively analyzed. The influence of control time and switch loss weight coefficient on the loss power of the device provides a reference range and typical value for the thermal design of equipment production. Taking this modulation strategy as an example, the loss imbalance is evaluated and measured. Finally, aiming at the phenomenon of device loss and power imbalance in multi-level converter, the application of thermoelectric refrigeration device in the cooling of multi-level converter is modeled and studied. The lifetime of power devices is closely related to the amplitude of junction temperature, the fluctuation range of junction temperature, the average junction temperature, the diameter of module bond line, the current of the device and the blocking voltage. At present, the multi-level converter adopts a kind of cooling mode, and the uneven loss of power devices will lead to uneven junction temperature distribution, which may lead to cost waste or device life and reliability reduction. Thermoelectric refrigeration devices are easy to operate and maintenance-free, and can be used as a supplementary cooling mode to reduce the fluctuation of junction temperature of power devices, reduce the working junction temperature of power devices, and even force cooling when the devices are overheated. In this paper, the energy exchange mechanism of thermoelectric refrigeration devices is deeply analyzed, and a more accurate mathematical model of thermoelectric refrigeration devices is established, which is beneficial to the research and development of thermoelectric refrigeration device control power supply and the realization of accurate temperature control. It lays a foundation for the application of this cooling method to multilevel converter products in the future.
【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM46

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