【摘要】 船舶直流电网中通常存在大容量的电容,不仅占用空间,而且在直流侧短路故障时产生巨大的放电电流,不利于故障保护,针对此问题,本文提出了一种无电容器设计的船舶中压直流电网结构,以避免直流侧短路时的电容放电过程。与常规直流电网不同的是,该电网电压存在较大波动,为了避免其对负载及变换器调制的影响,所提出的直流电网采用模块化多电平变换器作为接口变换器,实现DC/DC,DC/AC等变换。本文针对直流侧无电容后,增大的电压谐波对变换器的影响进行了分析,对模块化多电平变换器直流侧电压控制提出两种解决方法,并针对所提出的电网结构,分析了故障情况下的特征识别和协同操作的保护策略。最后通过PLECS仿真与实验数据验证了所提电网拓扑与模块化多电平变换器控制方法的正确性。更多还原

【Abstract】 There exist a large number of capacitors in conventional ship DC grid, which not only enlarges the system size, but also generates great current under fault condition, and this deteriorate fault protection. This paper proposed one capacitorless structure for ship medium voltage DC grid(MVDC), and this design avoids the capacitor discharge process during DC grid short circuit fault. Different from conventional DC grid, the DC voltage exists great fluctuations without the capacitor filter, thus the modular multilevel converter(MMC) is employed as interface converter to extenuate this influence, realizing DC/DC, DC/AC conversion. The MMC application problems caused by the abnormal grid voltage are also analyzed, and two control strategies are proposed to resolve this problem. Furthermore, this type DC grid fault features are also discussed, and the protection strategy based on AC side is provided. The proposed DC grid performance is validated by PLECS simulation and experimental results.更多还原