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To keep the frequency stable in a synchronous electric grid, power sources providing primary frequency control (PFC) are needed. Today, hydro power dominates the PFC market in the Nordic countries. However, if PFC can be offered as an ancillary service from PV-battery systems, the hydro power could be used more efficiently for low-cost electricity production. This can also improve the profitability of PV-battery systems. In this study of 2231 detached houses in Sweden, the potential to use residential PV-battery systems for PFC is examined. The results show that prices of up to 500 EUR/kWh excluding VAT for a 2.5 kW/5 kWh battery storage system can make enough PV-battery systems profitable to replace existing PFC sources in Sweden. The results are based on hourly electricity and PFC prices from 2015-2017 and a discount rate of 0%. If the prices for PFC are reduced by 50% and the discount rate is 5%, a system price of roughly 100 EUR/kWh excluding VAT would be enough to reach the same goal. The battery storage needs to be replaced during the lifespan of the PV system, meaning that the battery system prices are the average of the expected prices during the coming 25 years. [ABSTRACT FROM AUTHOR]

Renewable distributed generation and electric vehicles (EVs) are two important components in the transitions to a more sustainable society. However, both distributed generation and EV charging pose new challenges to the power system due to intermittent generation and high-power EV charging. In this case study, a power system consisting of a low- and medium-voltage distribution grid with more than 5000 customers, high penetration of roof-top mounted photovoltaic (PV) power systems and a fully electrified car fleet is used to assess the impact of the intermittent PV generation and highpower EV charging loads. Two summer weeks and two winter weeks with and without EV charging and a PV penetration varying between 0% and 100% of the annual electricity consumption are examined using measured and simulated data. Results show that the electricity consumption increases with 9% and 18% during the studied periods, and that EV charging only marginally can contribute to lowering the risk of overvoltage for customers resulting from PV overproduction. The most significant result is the increase in undervoltage in the winter when EV charging is introduced. The share of customers affected by undervoltage increases from 0% to close to 1.5% for all PV penetration levels. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) power generation is an important component in the future energy system. High penetration of PV power in a distribution power grid might however lead to overvoltage, i.e. +10% of rated voltage, for end-users. This study compares PV power curtailment and decentralized energy storage for overvoltage prevention in a 400V/10 kV distribution grid with large penetration of PV. LiDAR analysis is used to identify rooftops suitable for PV in a Swedish distribution grid with more than 5000 end-users. Results show that power curtailment allows 22% PV electricity (19 GWh yr-1) relative to total consumption on a yearly basis without overvoltage. PV production is reduced with 0.35 GWh due to curtailment. Decentralized energy storage of in total 86 MWh capacity achieves the same result. [ABSTRACT FROM AUTHOR]