Battery Rack SOC Control for Continuous Frequency Regulation
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Solution Overview
Problem
Existing energy storage systems face inefficiencies in continuous frequency regulation due to the need to stop charging or discharging when battery systems reach full charge or discharge states, requiring SOC to be reset to 50% for resumed operation.
Innovation Solution
An energy storage system with a power conversion system and a battery management system that uses two battery racks with different discharge rates, where the BMS controls charging and discharging operations based on state of charge thresholds to maintain a 50% SOC for the second battery rack, allowing continuous frequency regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery system is used for continuous frequency regulation by charging and discharging, then the frequency regulation capability is improved, but the battery system reaches full charge or discharge state causing operation to stop
Solution Approach 1:
The battery system is divided into multiple battery racks (first battery rack, second battery rack, etc.) that can operate independently. When one rack reaches full charge or discharge state, other racks can continue to perform frequency regulation, ensuring continuous operation. The rack BMS manages each rack separately, allowing seamless switching between racks.
Solution Approach 2:
When a battery rack reaches full charge or discharge state, it is temporarily taken out of service for frequency regulation (discarded from active duty), and the SOC is reset to 50%. Once reset, the rack is recovered and returned to service. This allows the system to maintain continuous operation by rotating racks in and out of active duty.
2Productivity
If the SOC of the battery system is reset to 50% to resume charging/discharging operations, then the continuous operation is restored, but operational inconvenience and time loss occur
Solution Approach 1:
The system proactively manages the SOC of battery racks before they reach full charge or discharge states. The rack BMS monitors SOC levels and strategically switches between racks or initiates SOC reset operations in advance, minimizing interruptions to frequency regulation and reducing the time loss associated with resetting.
Solution Approach 2:
By having multiple battery racks available and managing them independently, the system ensures that frequency regulation continues without interruption. While one rack is being reset or is at full charge/discharge, another rack takes over, maintaining continuous useful action in frequency regulation.
3Duration of action of stationary object
If multiple battery racks are used with different discharge rates, then continuous charging/discharging operation is enabled, but system complexity increases
Solution Approach 1:
Multiple battery racks with different discharge rates provide functional versatility to the system. Each rack can operate independently with its own characteristics, allowing the system to adapt to different power demands and duration requirements. The rack BMS manages these diverse racks through a unified control interface, hiding the complexity while providing continuous operation capability.
Data Source
AI summary
An energy storage system includes a power conversion system configured to produce a control signal for regulating a frequency of power flowing from a power generation system to an electric-power system, and a battery system including a first battery rack, a second battery rack, a charger/discharger configured to perform a charging/discharging operation of the second battery rack, and a rack BMS configured to control the charging/discharging operation of the first and second battery racks using the control signal, and to control the charger/discharger, thus controlling a state of charge (SOC) of the second battery rack.