Energy storage system utilisation to increase photovoltaic penetration in low voltage distribution feeders

This work introduces a new droop control for energy storage system (ESS) dispatch commands generation. The droop characteristic generates the ESS dispatch commands as a function of the power surplus at the substation transformer. The ESS with the new droop control aims to increase the level of Photovoltaic (PV) penetration in low voltage (LV) distribution networks, for the most economical solution in terms of ESS placement and sizing. The new droop control maintains two independent modes of operation; the first mode is fixed droop (FD) control, and the second mode is variable droop (VD) control. When FD control is employed, the droop characteristic remains invariable during hours of excessive PV generation, while the dispatch commands maintain the total of the grid parameters within the allowable range at all times. When VD control is performed, the slope of the droop characteristic was modified hourly, providing a sound grid operation at all times, while the accuracy of the dispatch commands was enhanced compared to the FD control mode. For the research, a real-life LV network case study that maintains a loop arrangement was utilised for modelling purposes. The operational grid constraints include transmission lines loading, terminal voltage variation, and substation transformer loading. Simulation results revealed that both of the proposed control modes maintain a sound grid operation for 70% PV penetration. The VD control performed better resulting in a lower cost ESS. The study demonstrated that an ESS located in the LV network performed a number of positive functions, including load management, peak load levelling and voltage support.