Hybrid Battery Rack Topology for DC Bus Step-Change Stability
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Solution Overview
Problem
Conventional energy storage systems with bidirectional DC-DC converters and battery racks struggle to respond simultaneously to step changes in load or power grid conditions, leading to malfunctions during sudden changes.
Innovation Solution
An energy storage system with a DC bus, first battery racks directly connected to the bus, and energy storage units including second battery racks and DC/DC converters, where a control module manages the operation state of DC/DC converters based on bus and battery rack powers to ensure stable voltage and smooth transitions during load fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bidirectional DC-DC converters and battery racks are connected in series to form energy storage units, then the system structure is well-defined and controllable, but the system cannot respond simultaneously to step changes in load or power grid conditions, leading to converter malfunctions
Solution Approach 1:
The system divides battery racks into two functional groups: first battery racks directly connected to the DC bus for rapid response to step changes, and second battery racks connected through DC-DC converters for controlled energy management. This segmentation allows the first battery racks to immediately absorb or supply power during sudden load changes, protecting the converters while the second battery racks provide sustained energy support.
Solution Approach 2:
The DC bus acts as an intermediary between the first and second battery racks. The first battery racks connect directly to the DC bus to provide immediate response, while the control module manages power flow through the DC bus to coordinate between the two groups, enabling the system to handle step changes without converter malfunction.
2Speed
If all battery racks are connected directly to the DC bus, then the response speed to step changes is maximized, but the system loses the ability to perform controlled electric energy conversion and buffering
Solution Approach 1:
The system segments battery racks into two categories with different connection methods: first battery racks connected directly to the DC bus for rapid response, and second battery racks connected through DC-DC converters for controlled energy conversion. This segmentation enables the system to simultaneously achieve fast response and adaptable energy management.
Solution Approach 2:
The system merges two different connection topologies (direct connection and converter-mediated connection) into a unified hybrid architecture. The first battery racks provide immediate response through direct connection, while the second battery racks provide controlled energy conversion through DC-DC converters, and both work together through the DC bus to achieve comprehensive system performance.
3Reliability
If a hybrid topology with first battery racks directly connected and second battery racks connected through DC-DC converters is used, then the system can respond to step changes and maintain stable voltage, but the device complexity increases
Solution Approach 1:
The DC bus serves multiple functions: it provides a common connection point for both direct-connected and converter-mediated battery racks, acts as a voltage stabilization node, and facilitates coordinated control between the two battery rack groups. This multi-functionality reduces the need for additional dedicated components, managing system complexity while maintaining voltage stability.
Solution Approach 2:
The control module continuously monitors the DC bus voltage and the state of charge of both first and second battery racks, dynamically adjusting the operation of DC-DC converters and power distribution to maintain stable voltage. This feedback control ensures voltage stability while optimizing the use of available battery capacity, reducing the need for overly complex protective circuitry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system maintains stable output and protects DC/DC converters by allowing first battery racks to respond immediately to step changes, allowing the control module to manage energy transitions, ensuring stable operation even with rapid load fluctuations.
Implementation Method 1
The DC/DC converter is configured to perform electric energy conversion between the corresponding second battery rack and the DC bus
Implementation Method 2
The energy storage converter is configured to convert AC electric energy from an AC source into DC electric energy, or convert DC electric energy from the DC bus into AC electric energy
Data Source
AI summary
An energy storage system includes a DC bus, an energy storage converter, n first battery racks and m energy storage units. The DC bus has a positive bus and a negative bus. The energy storage converter is electrically connected to the DC bus. Each of the n first battery racks is electrically connected between the positive bus and the negative bus directly. Each of the m energy storage units includes a second battery rack and a DC/DC converter. The DC/DC converter is electrically connected between the corresponding second battery rack and the DC bus. The DC/DC converter performs electric energy conversion between the corresponding second battery rack and the DC bus.