海上大容量中压风电变流器的网侧滤波器设计

Design of Grid Side Filter for Offshore High Power Medium Voltage Wind Power Converters

和陆基风电变流器不同,海上风电变流5器属于大容量中压系统,其网侧LCL滤波器的设计难度主要体现在几个方面,即中压变流器开关频率是受限的,而滤波器物理尺寸和重量有严格限制,同时电流谐波也有严格标准,因而传统的小功率、高开关频率低压变流器的滤波器设计将不再适用。针对这个问题,本文以三电平中点钳位型风电变流器为例,采用了基于频域模型分析的方法对其网侧LCL滤波器进行了设计,首先提出了一种虚拟电压谐波频谱的概念来对滤波器设计提供相关的约束,然后利用储能对应体积重量的概念简化了设计过程,同时还使用了被动阻尼技术,为滤波器提供了必要阻尼的同时还保持了低损耗和对高频衰减较小的影响。最后,对滤波器性能进行了仿真试验,试验结果表明,在额定感性和容性输出时,输出谐波均符合标准要求,变流器侧最大电流纹波小于20%,最大附加损耗小于标么的0.5%,滤波器设计较为合理,滤波效果较好,附加损耗较低。

Offshore wind power converter, unlike land-/~ased wind converter,belongs to high power medium voltage system. The design difficulty of its grid side LCL filter is reflected mainly in such aspects as limitation of switch frequency of medium voltage converter,strict limit of physical dimension and weight of filter and strict standard of current harmonics. Therefore the design of filter with traditional small power and high switch frequency low voltage converter is not appropriate any more. As for this issue, in this paper,the grid side LCL filter is designed by the method of frequency-domain model analysis with three-level neutral point clamped converter as an example. Firstly, a kind of concept of virtual voltage harmonic spectrum is proposed to provide related constrain of filter design,then the design process is simplified by the use of the concept of the relationship between energy storage and volume and, at the same time, the passive-damping technology is also used so to provide necessary damping of filter and, at the same time,maintain low loss and minimum influence of high frequency decay. Finally the performance of the filter is simulated and tested. It is shown by the test result that in ease of rated inductive and capacitive output,the output harmonics complies with standard requirement,the ripple of maximum current at the converter side is less than 20% and the maximum additional loss is less than 0.5% of the p. u. The filter has reasonable design, good filtering result and low additional loss.