用于提高发电机-变流器组出口电压的新型风电变流器及其特性分析

A novel wind power converter for increasing output voltage of generator-converter unit and analysis of its characteristics

文章提出一种新型中低压混合拓扑的风电变流器,该变流器机侧采用两电平变流器级联,网侧采用三电平变流器,提高了网侧变流器电压等级,减少了电缆的数量。首先对新型风电变流器的电压特性进行Simulink仿真验证,表明新拓扑结构不需要提升发电机绝缘要求;然后,对网侧变流器中点电位平衡进行了分析,并提出了一种改进的虚拟空间矢量调制策略,该策略能够在较高调制度下实现中点电位平衡,并通过RTLAB硬件在环实验验证了其中点电位平衡能力;最后,对新型风电变流器的效率与成本进行了分析,指出同功率等级下,新型风电变流器较低压并联型风电变流器有显著的效率与成本优势。

The power of offshore wind power converters is increasing day by day.With the improvement of power levels,the problem of twisted cables in the tower is becoming more and more serious in wind power systems that use low-voltage parallel topology.Therefore,this paper proposes a new type of wind power converter that can increase the output voltage of the generator-converter unit.The new-type converter adopts two-level converter cascade connection on the machine side and threelevel converter on the grid side to form a medium and low voltage hybrid wind power converter.The medium and low voltage hybrid topology still use low voltage generators,but the increase in the voltage level of the grid-side converter reduces the number of cables required,effectively solving the problem of twisted cables.Aiming at the new type of wind power converter,this paper analyzes its voltage characteristics and validates it through simulink simulation,which shows that under the new topology,the generator insulation requirements are not qualitatively improved.After that,this paper analyzes the neutral point potential balance of the grid-side converter,and proposes an improved virtual space vector modulation strategy.This strategy can achieve mid-point potential balance under high modulation degree,and the mid-point potential balance capability is verified by RTLAB hardwarein-the-loop experiments.Finally,this article analyzes the efficiency and cost of the new wind power converter,and points out that under the same power level,the new wind power converter lower voltage parallel wind power converter has significant efficiency and cost advantages.