Parameter adaptive model predictive control strategy of NPC three-level virtual synchronous generator

The Virtual Synchronous Generator (VSG) emulates the characteristics of a synchronous generator to provide inertia and damping for renewable energy systems. In the case of using the NPC three-level converter structure, traditional control methods require complex dual-loop control and internal PI parameter tuning. Furthermore, although fixed-parameter VSG control can provide inertia and damping when a significant power load is switched in an islanded microgrid, it cannot guarantee frequency regulation performance. To address these issues, this paper proposes an NPC three-level VSG parameter adaptive finite control set model predictive control strategy. This method eliminates the need for dual-loop control and PI parameter tuning. By incorporating angular velocity deviation and its rate of change into adaptive adjustment, a Tracking-Differentiator (TD) is designed to calculate the rate of change of angular velocity. This approach avoids frequent fluctuation of adaptive parameters during load power switching and improves the frequency stability of the microgrid. The effectiveness of the proposed strategy is validated through simulation and experimental verification

liveness analysis of parallel programs petri net models

Wuhan University; Huazhong Normal University; Wuhan University of Technology; National Technology University of Ukraine; Columbia UniversityThe liveness of Petri net models of parallel programs is a very important property . The existing analysis techniques take Petri net models as a whole to study properties,which is subject to the state explosion problem.In this study,we decompose a parallel programs petri net model into multiple process subnets to study liveness preservation instead of taking it as a whole, which thus mitigates efficiently the state explosion problem to some extent. In this paper, the liveness preservation relation between a MPINet and its process subnets is analyzed in detail. A necessary condition of keeping liveness of a MPINet composed of n live process subnets is given.And a class of CR-restricted MPINets is proposed.Liveness preservation can be efficiently verified based on only their net structures for CR-restricted MPINets. ©2009 IEEE