Energy Management Strategies for Second Life Battery Energy Storage Systems in Grid Applications

Energy storage for power systems has been gaining interest recently as the penetration of renewable energy increases. Not only is it essential for the integration of renewable energy into the grid, but it can also provide many other services such as energy arbitrage, voltage support, and frequency regulation. The demand for batteries that are suitable for use in grid storage applications could be met by second life electric vehicle batteries that will be retired in the coming years. This thesis provides a comprehensive examination of Battery Energy Storage Systems (BESS), starting with the fundamental concepts of batteries and the implications of aging and lifecycle management on performance and reliability. The critical components of a BESS, including Battery Management Systems (BMS), Energy Management Systems (EMS), and Power Conditioning Systems (PCS) are reviewed, highlighting their roles in optimizing system performance.

A simulation model of a BESS is developed to study the effects of energy management strategies on the cost of energy while using a BESS. The model can perform 4 operations – timed peak shaving, setpoint peak shaving, load leveling, and load shifting. Studies using this model show that the shape of the load impacts which energy management strategy is most suitable. The number of peaks, duration, and time of day it occurs should be considered when determining the best method. This model allows for any load, irradiance, and pricing structure to be input for easy evaluation. A 40 kW BESS building block is designed, constructed, and tested as part of a joint project with Volkswagen. Each of the main components is selected based on functionality and cost. After component testing, each part is integrated into a test system. The final system demonstrates a fully working state machine with grid connected, islanded, standby, and fault states. In the future, the BMS and measurement devices need to be implemented before scaling up the system to 500 kW.