Residual load models for power system restoration: High shares of residential thermal loads and volatile PV generators

The residual load power gradients over high-voltage-medium-voltage (HV-MV) power transformers after re-energization of long-lasting interrupted MV-grids are investigated. In this paper, the MV-grids are assumed to serve only residential areas with high thermal load capacities whose diversity factors are significantly influenced by power interruption durations causing the cold load pick-up (CLPU) phenomenon. Increasing shares of volatile renewable energy source (RES) generation with automatic-synchronization characteristics in MV-grids and their underlying grids influence the abovementioned residual load gradients. This paper investigates possible ways of regulating the residual load gradients especially for the frequency-sensitive HV-grid islands to reach a successful power system restoration.