Energy Storage Pre-Charge Circuit for In-Rush Current Control
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Solution Overview
Problem
In energy storage systems, the asynchronous response of switches in series-connected circuits can lead to in-rush currents when capacitors are discharged, potentially damaging the system, and existing pre-charge circuits require activating each switch individually, which is inefficient and may not account for varying voltage levels across switches.
Innovation Solution
An energy storage circuit with a pre-charge circuit, sensor, and controller that detects voltage polarity and closes a current path based on a received signal, allowing for synchronized pre-charging of capacitors and reducing switch ratings by utilizing a cascaded control mechanism where one controller's action triggers others based on detected voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pre-charge circuit is used for all serially connected energy storage circuits, then the device complexity is reduced, but the switches must be rated to block the sum of voltage levels of all energy storage units, increasing the switch rating requirement
Solution Approach 1:
The patent divides the single pre-charge circuit into multiple independent pre-charge circuits, each associated with a specific energy storage circuit. Each pre-charge circuit includes its own switch that only needs to block the voltage of its local energy storage unit, not the sum of all units. This segmentation resolves the contradiction by distributing the voltage blocking requirement across multiple lower-rated switches while maintaining pre-charge functionality.
Solution Approach 2:
The patent introduces a hierarchical control dimension with master and slave controllers. The master controller coordinates the activation of multiple pre-charge circuits in sequence, while slave controllers execute local switching operations. This dimensional addition to the control architecture enables distributed pre-charging without requiring any single switch to handle the total system voltage.
2Strength
If switches are activated individually in serially connected energy storage circuits, then the switch voltage rating can be reduced, but the asynchronous response of switches can cause in-rush currents when capacitors are discharged
Solution Approach 1:
The patent implements pre-charging of capacitor voltages before closing the main switches. The pre-charge circuits are activated first to charge the output capacitors of each energy storage circuit to appropriate voltage levels. This preliminary action ensures that when the main switches close, there is no voltage difference driving in-rush currents, thus protecting the system while allowing individual switch activation.
Solution Approach 2:
The patent employs voltage detection circuits that monitor the voltage levels across energy storage units and provide feedback to the controllers. This feedback mechanism enables the controllers to determine the correct timing for activating pre-charge circuits and main switches, ensuring synchronized operation that prevents in-rush currents while maintaining low switch ratings.
3Productivity
If the management system controls switches to close conduction paths, then power production can commence, but asynchronous switch response may expose switches to full system voltage
Solution Approach 1:
The patent segments the power production control into distributed slave controllers at each energy storage circuit, each managing its own switch. This segmentation allows rapid local response to commence power production without requiring centralized control of all switches simultaneously, reducing the voltage stress on individual switches while maintaining productivity.
Solution Approach 2:
The patent implements a two-stage switching process: first, pre-charge switches close to charge capacitors; second, main power switches close to commence power production. This preliminary pre-charging action ensures that when main switches close, the voltage difference is minimized, allowing rapid power production commencement without exposing switches to full system voltage.
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
This solution reduces the risk of in-rush currents and lowers switch ratings by enabling synchronized pre-charging across multiple energy storage circuits, enhancing the reliability and efficiency of energy storage systems.
Implementation Method 1
the management system may comprise a capacitor connected across the terminals of the management system. In some cases, each energy storage circuit may comprise capacitance (e.g., parasitic capacitance, or capacitance of a capacitor of the energy storage circuit). Applying a voltage across these capacitors when the capacitors are discharged, may result in an in-rush current
Implementation Method 2
a sensor configured to detect an electrical characteristic; and a control circuit configured to, based on the electrical characteristic indicating that a first polarity of a first voltage between the first terminal and the second terminal is opposite of a second polarity of a second voltage across the energy storage unit
Data Source
AI summary
Various implementations described herein are directed to a system comprising energy storage circuits connected in series. Each energy storage circuit may comprise a first terminal, a second terminal, an energy storage unit, a pre-charge circuit, and/or a bypass diode. The energy storage unit and the pre-charge circuit may be connected in series to form a series connection between the first terminal and the second terminal, while the bypass diode may be connected in parallel to the series connection. The pre-charge circuit may be configured to close a first current path between the first terminal and the second terminal based on receiving a signal. The bypass diode may be configured to, based on the voltage between the first terminal and the second terminal having an opposite polarity to the voltage across the energy storage unit, close a second current path between the first terminal and the second terminal.