No abstract

Seafloor observation network provides limited opportunity for repair due to the atrocious weather on the sea. As a result, reasonable reliability allocation methods are required to assure the network is sufficiently reliable during expected years. In this thesis, betweenness is used for evaluating the importance of component based on binary search algorithm, and residual connectedness reliability is calculated according to Monte Carlo method to avoid combinatorial explosion. This method is applied on meshed seafloor observation network to obtain satisfying reliability allocation for backbone nodes. Further, the relationship between nodes reliability allocation and residual connectedness reliability is discussed, on the basis of which certain suggestions for network improvement are proposed.

No abstract

This paper investigated the characteristics of a novel type of hybrid high voltage direct current (HVdc) converter, which is composed by line commutated converter series with voltage source converter. The system and valve level control strategies are introduced, which can provide ac system voltage support. A novel filter design scheme composed by resonant filers for hybrid HVdc are also proposed, which can decrease the capacity of reactive power compensation equipment without deteriorate harmonic characteristics. The ac voltage of HVdc fluctuation level caused by transmitted power variation will be effectively reduced, with the coordination between filter design scheme and converter control. In addition, the influence of ac grid strength is also analyzed by equivalent source internal impedance represented by short circuit ratio (SCR). Finally, the +800 kV/1600 MW hybrid HVdc system connecting two ac grids under different SCR cases are studied, and the PSCAD/EMTDC simulation results have validated the effectiveness for proposed strategy.