风电全功率变流器参数对可靠性的影响分析

Analysis of Effect of the Converter Parameters on Full-Rated Wind Power Converters Reliability

风速的随机变化使得风电变流器处理变化的功率,导致器件的温度产生波动,影响变流器的可靠运行。现有的基于一个工作状态下的风电变流器可靠性评估,无法反映负载随机变化造成器件温度波动对变流器可靠性的影响。功率器件失效的主要形式为铝键合线失效与焊料层疲劳,本文综合考虑这两种失效因素,给出了可靠性评估模型和评估方法,分析了开关频率、功率因数及散热热阻的变化对风电全功率变流器可靠性的影响,并以1MW永磁同步风力发电机为例结合实际的风速及气温数据进行了验证。实例结果表明,开关频率与散热热阻的变化对变流器可靠性的影响比较大。根据分析结论,讨论了针对风电变流器的实际工作环境,考虑风速的概率分布,对利用变频或变散热条件的控制措施以提高变流器可靠性的可行性。结果表明,可通过根据风速等工况来改变开关频率和散热条件来提高变流器的可靠性。

Random change of the wind speed makes the wind power converter process changeable power, leading to temperature variation for power devices, which affects the converter reliability. Existing methods evaluate the converter reliability based on one operating point, where the impact of temperature fluctuation of power devices on the converter reliability can＇t be shown. Given that the main failure mechanisms of power devices are wire bond off and solder fatigue, the corresponding model and method for reliability evaluation is presented considering both these failures to analyze the effect of switching frequency, power factor and thermal resistance of heat sink on the reliability of full size converter in the wind turbine. Then combined with actual wind speed and air temperature, a 1MW wind turbine of permanent magnetism synchronous generator（PMSG） is illustrated and the result is verified. The result shows that the switching frequency and thermal resistance of heat sink have relatively great influence on the converter reliability. According to the conclusion analyzed, considering the distribution of the wind speed, the feasibility of increasing the wind power converter reliability based on the change of switching frequency or thermal dissipated condition is discussed in view of actual work condition of the converter. The result indicates that the increase of the converter reliability can be achieved by changing them based on the wind condition.