Battery String Switch Sequencing for Lower-Cost Bypass Circuits
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Solution Overview
Problem
Existing power storage systems with series-connected batteries require high-cost switches to manage voltage and current during bypass operations, leading to increased costs and complexity.
Innovation Solution
A storage battery control device and method that uses a string switch to disconnect from the power converter before bypassing a storage battery and reconnect after the bypass operation, reducing the need for high-cost switches by setting the rated voltage of the string switch to match the total voltage and lowering the rated voltages of bypass and module switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-cost switches coping with high voltage and large current are used for the first switch and second switch to prevent short circuit during bypass operation, then reliability is improved, but cost increases
Solution Approach 1:
The string switch is switched to the disconnected state before the bypass switch is switched to the connected state. This preliminary disconnection of the string switch isolates the bypass circuit from the power converter, allowing the bypass switch to be a low-cost component that does not need to withstand high voltage and large current during bypass operation.
Solution Approach 2:
The switching function is divided between the string switch and the bypass switch. The string switch handles the high-voltage disconnection before bypass operation, while the bypass switch only needs to handle low-voltage bypass current. This segmentation allows using inexpensive switches for the bypass circuit while maintaining system reliability.
2Reliability
If the bypass switch is switched from connected to disconnected state before releasing bypass, then safety is improved, but device complexity increases
Solution Approach 1:
The switching control logic for the string switch and bypass switch is integrated into a unified control sequence managed by the control device. The control device automatically executes the coordinated switching operations (string switch disconnect first, then bypass switch disconnect) as a single control process, eliminating the need for separate complex control mechanisms while maintaining safety.
Data Source
AI summary
A storage battery control device constructed of a controller and a driver is provided so as to control a power storage system. The power storage system has storage battery strings including a plurality of power storage batteries connected in series and bypass circuits, power converters configured to convert input and output voltages of the storage battery strings, and a string switch configured to connect or disconnect the storage battery strings and the power converters. The string switch is brought into a disconnected state by the storage battery control device before execution of a bypass operation by the bypass circuits, and is brought into a connected state by the storage battery control device after the execution of the bypass operation by the bypass circuit.