Parallel Energy Storage Bank Input Order for Cross-Current Control
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Solution Overview
Problem
In energy storage systems with multiple energy storage banks connected in parallel, voltage differences lead to cross currents during input to a trunk line, which can exceed a limit value, causing defects in energy storage banks or protective devices.
Innovation Solution
A system control device mitigates cross currents by executing processes that suppress the voltage difference between energy storage banks to below a threshold before allowing input to the trunk line, and determines an order of input based on voltage differences to minimize cross currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If energy storage banks are caused to input to the trunk line after installation, then the energy storage system becomes operational, but cross current may exceed the limit value causing defects
Solution Approach 1:
The system performs preliminary voltage difference detection and cross current estimation before allowing energy storage banks to input to the trunk line. By calculating the expected cross current based on voltage differences and resistance values in advance, the system prevents excessive cross current from occurring, thus avoiding defects while enabling operational readiness
Solution Approach 2:
The system continuously monitors voltage differences between energy storage banks and uses this feedback to estimate cross current values. Based on the estimated cross current, the system dynamically determines whether to permit input to the trunk line, creating a closed-loop control that prevents defects while maintaining operational efficiency
2Object-affected harmful factors
If voltage difference between energy storage banks is reduced before input, then cross current is suppressed, but monitoring and control complexity increases
Solution Approach 1:
The system uses the existing voltage detection capability and resistance value storage to automatically estimate cross current without requiring additional complex measurement equipment. The control device leverages already-available system parameters (voltage differences and resistance values) to perform cross current estimation, thus suppressing cross current while avoiding significant increases in system complexity
Solution Approach 2:
The system introduces an estimation calculation as an intermediary step between voltage detection and input control. Rather than directly measuring cross current (which would require complex instrumentation), the system calculates expected cross current values based on voltage differences and resistance values, providing a simplified control mechanism that suppresses cross current without adding substantial complexity
Data Source
AI summary
An energy storage system includes a plurality of energy storage banks connected in parallel to a trunk line, and a system management device. When a maximum voltage difference between the energy storage banks is equal to or greater than a first threshold before the energy storage banks are caused to input to the trunk line, the system management device executes a process of mitigating a cross current generated between the energy storage banks to mitigate a cross current accompanying the inputting to the trunk line by the energy storage banks. When the maximum voltage difference between the energy storage banks is less than the first threshold, the system management device causes the energy storage banks to input to the trunk line without limitation of the process of mitigating the cross current.