Battery Storage Unit Switching for Short-Circuit Current Limits
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Solution Overview
Problem
Large-scale battery energy storage systems are limited by the short circuit current tolerance of components, which restricts the energy capacity due to high prospective short circuit currents that downstream electrical components cannot withstand, and existing protection devices like fuses and circuit breakers are inadequate in managing these currents effectively.
Innovation Solution
Selecting a subset of battery energy storage units with combined short circuit currents below a predetermined limit, allowing only these units to be connected to the DC power connection, thereby controlling and limiting the short circuit current to a safe level, and using a switching arrangement to manage the connection and disconnection of these units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If battery racks are connected in parallel to increase energy capacity, then the energy storage capacity increases, but the prospective short circuit current increases to a level that downstream electrical components cannot withstand
Solution Approach 1:
The system divides the battery energy storage system into multiple groups, where each group contains a limited number of battery racks connected in parallel. The controller selectively activates only the necessary number of groups based on the prospective short circuit current level and the energy storage requirement, thereby segmenting the total capacity into manageable portions that do not exceed component current withstanding limits.
2Quantity of substance
If all battery racks are connected to meet energy storage requirements, then the energy capacity is sufficient, but the short circuit current exceeds the current withstanding level of downstream components
Solution Approach 1:
The system dynamically adjusts the number of active battery rack groups based on real-time conditions. The controller monitors the prospective short circuit current and selectively connects or disconnects groups to maintain operation within safe current limits while maximizing energy storage utilization. This dynamic reconfiguration allows the system to adapt to varying load conditions and component thermal states.
3Object-affected harmful factors
If battery racks are limited to a certain number per group, then the short circuit current is controlled within safe limits, but the energy storage capacity of each group is reduced
Solution Approach 1:
The system transitions from a single-dimension approach (one large group of parallel battery racks) to a multi-dimensional approach by organizing battery racks into multiple hierarchical groups. Each group is limited in size to control short circuit current, but multiple groups can be activated in parallel to achieve the total required energy storage capacity. This group-based organization adds a structural dimension that resolves the contradiction between current limiting and capacity accumulation.
Data Source
AI summary
A method for controlling a battery energy storage system and a battery energy storage system including at least three battery energy storage units, a switching arrangement, and a control arrangement configured to select at least two battery energy storage units such that a sum of short circuit currents of the selected battery energy storage units is below a short circuit current limit, which is less than a sum of short circuit currents of the at least three battery energy storage units, and such that a sum of discharge or charge powers of the selected battery energy storage units equals to or exceeds a power limit, and such that states of charge of the selected battery energy storage units are within a determined range, and to control the switching arrangement to couple only the selected at least two battery energy storage units to a DC power connection.