Hierarchical Mechanism of Voltage Instability with Active Distribution Networks

Distributed generation (DG) transforms passive distribution networks (DN) to active distribution networks (ADNs). While recent studies point out its potential to relieve static voltage stability, there is limited understanding of DG’s role in dynamic voltage instability. To understand the DG’s role, this paper derives the mechanism of hierarchical voltage instability in power systems considering the interaction between transmission network and ADNs. We propose metrics to identify this hierarchical mechanism based on modal analysis and reactive power reserves of DGs. We validate the revealed mechanism and the proposed metrics on a test system. The findings of this paper are significant for the development of countermeasures against voltage instability in power grids with ADNs.