Preventing overvoltage in a distribution grid with large penetration of photovoltaic power
(English)Manuscript (preprint) (Other academic)
The global market for photovoltaics (PV) has increased rapidly during the last years: during 2014, 44 times more was installed than in 2004, partly due to a price reduction of 60-70% during the same time period. Considerable amounts of intermittent distributed generation (DG) such as PV and wind power in a distribution grid can lead to a deterioration of the power quality, both in the power grid and for end-users. In this study, methodologies for overvoltage prevention in a medium-voltage distribution grid using centralized battery storage and power curtailment of grid-connected PV systems were developed. A 10 kV grid in the Swedish municipality of Herrljunga with a yearly electricity consumption of 56.9 GWh and a simulated total PV electricity production of 24.2 GWh was used as case study. In the base case overvoltage occurred during 2.0% of the hours of the year in at least one transformer. Overvoltage, in this case defined as hourly voltage levels exceeding 10.5 kV, was eliminated with battery storage at 5 locations in the grid with a total storage capacity of 2.4 MWh. With power curtailment of the PV panels one of 161 transformers in the power grid was affected by overvoltage during 0.64% of the hours of the year, with a maximum voltage of 10.504 kV. With a battery round-trip efficiency set to 81% the total losses due to charging and discharging were 102 MWh. With PV power curtailment, the total electricity production from PV systems was lowered with 25 MWh. This shows a potential for storage and PV power curtailment to reduce stress on a distribution grid, although roughly 40% of the electricity demand from solar, as in this study, is unrealistic for a whole synchronous power system with today's storage technology.
Photovoltaics, Solar energy, Grid integration, Distributed generation, energy storage, curtailment, Power system
IdentifiersURN: urn:nbn:se:uu:diva-283615OAI: oai:DiVA.org:uu-283615DiVA: diva2:919410
FunderSwedish Energy Agency