考虑母线故障的低通流损耗多端口整流型混合式直流断路器

混合式直流断路器是当前柔性直流电网最为理想的故障隔离方式,但是投资成本高限制了其大范围的应用。为了降低混合式直流断路器的成本,提出了一种多端口整流型混合式直流断路器拓扑,选择开关采用简单可靠的二极管桥式整流结构,负载转移开关和主断开关采用单向开断子模块,并通过电流转移控制策略的优化,使得直流断路器具备电流双向开断、设备成本低和通流损耗低等优点;同时,增加了一条母线保护支路,实现了直流母线故障隔离和公共母线故障保护。文中首先详细介绍了所提拓扑在不同故障工况下的工作原理以及内部组件的动作策略;然后,与现有拓扑进行了经济性和电气性能的对比分析,突出所提拓扑的优越性;最后,设计并搭建了一台三端口整流型混合式直流断路器样机及其试验系统,通过试验验证了所提拓扑的有效性和可行性。

Modeling of 3-D Losses and Deviations in a Throughflow Analysis Tool

This contribution is dedicated to the modeling of the end-wall flows in a throughflow model for turbomachinery applications. The throughflow model is based on the Euler or Navier-Stokes equations solved by a Finite-Volume technique. Two approaches are presented for the end-wall modeling. The first one is based on an inviscid formulation with dedicated 3-D distributions of loss coefficient and deviation in the end-wall regions. The second approach is directly based on a viscous formulation with no-slip boundary condition along the annular end-walls and blade force modification in the region close to the end-walls. The throughflow results are compared to a series of 3-D Navier-Stokes calculations averaged in the circumferential direction. These 3-D calculations were performed on the three rotors of a low pressure axial compressor, for a series of tip clearance values.