Background Electric utility companies are concerned with the potential difficulties caused by the large-scale penetration of photovoltaics (PVs) and EVs in the power grid. Various challenges may stem from the intermittent nature of solar PVs and unpredictable EV loads that may cause supply-demand imbalances, such as reverse power flow, malfunctioning network protectors, fluctuating voltage and frequency. These difficulties will especially affect the distribution side of the grid where households and buildings directly connect to PVs and EVs.
The deployment of energy storage systems offers a practical and effective solution to improve the behavior of renewable energy sources from a grid perspective. Among feasible types of energy storage technologies, battery storage systems are widely used and fairly developed. As a result, battery energy storage systems (BESS) are prime targets of research to accompany distributed generation with the goal of enhancing power quality.
Scope of Research
The SMERC Battery Storage Integration and Aggregation program aims to integrate an energy storage system into a micro-grid to research the following benefits:
Peak shaving: The intermittency of solar energy sources and the increasing use of EVs with variable and random consumption profiles can create energy imbalances within the power grid, causing notable differences in the peaks and valleys of the load profile. A grid-connected energy storage system can help eliminate these peaks and valleys through load leveling, peak shaving, and power demand management.
Local load leveling: Battery energy storage systems (BESS) can provide load balancing services for local grids, by acting as a reserve load that charges during periods of low energy demand to increase energy demand, and discharges power during high loads to help balance peak demand.
Improve power reliability of the grid: Energy storage systems and solar energy sources can help improve the reliability of electric service by providing the required electricity during power outages, through the micro-grid's islanded operation mode; thus, helping to reduce the ratio of electric power interruption over a specific period of time.
Improve the Duck Curve Challenge: The rapid growth of solar energy deployment presents two challenges known as the Duck Curve. First, over generation can occur around noon when there is a high penetration of solar energy. Second, a load-generation imbalance occurs during the evening when solar generation is decreasing and the demand is increasing. Both challenges can be mitigated by utilizing energy storage on the grid.
Support and regulate the voltage of the grid: The integration of PVs and EVs into the distribution system can cause voltage variations due to the intermittent output of solar resources and the variability of EV load profiles. Energy storage systems can help maintain voltages within an acceptable range by providing the required active/reactive power for the electric distribution grid.
Support and regulate the frequency of the grid: Energy storage systems can help reduce large and sudden load-generation imbalances by controlling active power to maintain the frequency of the grid within the allowable tolerance level.
Improve power quality: Energy storage systems can change the shape and magnitude of current and voltage variations to improve power quality quantities, such as power factor, voltage and current harmonics, sag and swell, transients, flicker, etc.
Improve transient stability of the grid: Grid dynamics and stability rely on the amount of stored energy in a micro-grid. Therefore, energy storage will have significant stabilizing effects on the system by storing energy and feeding it to micro-grids in the event of drastic load changes or disturbances.
Compensate unbalanced load: Energy storage systems can separately control and transfer power for each phase to supply unbalanced loads.