采用耦合电抗器的兆瓦级永磁直驱风电变流器仿真研究

SIMULATION RESEARCH OF MEGAWATT PERMANENT-MAGNET DIRECT-DRIVE WIND TURBINE CONVERTERS WITH INTERPHASE INDUCTORS

提出一种采用耦合电抗器的独立直流母线型永磁直驱风电变流器,分析其去耦等效电路和高阻抗环流路径,阐明耦合电抗器抑制环流的根本机理,并分别建立机侧变换器和网侧变换器的数学模型,根据所得模型分别设计控制策略,实现了永磁直驱风电变流器的并联运行,抑制了环流,解决了环流引起的不均流、波形畸变等问题,提高了系统的可靠性和效率。最后,对一组采用耦合电抗器的1.5 MW永磁直驱风电变流器进行了仿真验证,结果证明上述分析及控制策略的正确性。

The permanent magnet synchronous generator is connected to the grid through full power converter. Due to the limitation of power devices and switching frequency, the parallel operation of converters is usually used in megawatt-level wind turbine system. The circulating-current impedance of the parallel topology with separate dc buses is larger than one with common dc buses. Moreover, the interphase inductor has the advantages of supporting current sharing and small size. Therefore, the novel topology of permanent-magnet direct-drive wind turbine converter with interphase inductors and separate DC buses was proposed. Its decoupling equivalent circuits and circulating-current route with high impedance were derived. The circulating-current suppression mechanism of interphase inductors wes illustrated and the models of the generator-side converters and the grid-side converters were obtained respectively. Then the control strategy of the system is designed according to the models. The parallel operation of wind turbine converters is achieved. The circulating-currents are suppressed well and the problems of current discrepancy and distortion are overcome. Therefore, the reliability and efficiency of the system are improved. Finally, the 1.5 MW wind turbine converters with interphase inductors are simulated, which verifies the validity of the above analysis and control strategy.