直驱型变速恒频风力发电系统的独立直流母线并联策略

为了提高直驱型变速恒频风力发电系统的功率等级,提出一种多组变流器相互并联且直流母线相互独立的并联策略。针对零序环流问题,分别在三相静止坐标系和同步旋转坐标系下进行了分析,得出了所采用拓扑的数学模型及等效电路,揭示了零序环流产生的根本机理,即它是由并联变流器之间三相占空比零轴分量的不一致及直流母线电压的不一致造成的,并证明了机侧零序环流与网侧零序环流是互相耦合的,进而设计了零序环流控制器,很好地抑制了零序环流,解决了不均流、三相电流畸变等问题。最后对一组直驱型风力发电实验平台进行了仿真及实验验证,证明了上述分析及控制策略的正确性。

Parallel Strategy of Direct-driven Variable-speed Constant-frequency Wind Turbine System With Separate DC Buses

To increase the power rating of the direct-driven variable-speed constant-frequency wind turbine system,the paper presented a new parallel strategy with multiple converters which are parallel with each other.Each converter had its own separate DC bus.The phenomenon of zero-sequence circulating-currents were analyzed in the three-phase stationary coordinates and the synchronous rotating coordinates respectively.The mathematical model and equivalent circuit were got.It could be seen that the zero-sequence circulating-currents were caused by the zero-axis component discrepancy of three-phase duties and the DC bus voltage discrepancy.Besides,the generator-side zero-sequence circulating-currents were coupled with the line-side ones.Then the zero-sequence circulating-current controllers were designed based on the above analysis.They suppressed the zero-sequence circulating-currents effectively and the problems of the current discrepancy and the three-phase current distortion were overcome well.At last,the simulation and experiment were done based on a direct-driven wind turbine system and the results verified the validity of the above analysis and control strategy.