Flexible DC Battery Current Control via Modular Switching
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Solution Overview
Problem
Conventional traction batteries in electric vehicles rely on costly and space-intensive contactors and fuses to limit high currents during faults, which are sluggish and inefficient, and require additional components like capacitors for voltage control, leading to high current spikes and slow discharge processes.
Innovation Solution
A flexible DC battery system with interconnectable modules and controllable switches, controlled by a battery control unit, which uses inductance to limit current changes and incorporates a PI controller for rapid current restriction and modulation, eliminating the need for bulky contactors and fuses by electronically managing the battery current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactors and fuses are used to limit high currents during faults, then current protection is provided, but the system becomes costly, space-intensive, and sluggish in response
Solution Approach 1:
The patent replaces mechanical contactors and fuses with an electronic current control system using controllable switches (transistors or IGBTs) in a modular battery pack. The control unit monitors current and actively switches modules in series/parallel configurations to limit current electronically, eliminating sluggish mechanical response and reducing hardware complexity.
Solution Approach 2:
The battery pack modules are dynamically reconfigurable between series and parallel connections based on real-time current conditions. The control unit actively adjusts the circuit topology to limit current during faults, providing adaptive protection rather than static mechanical switching.
2Reliability
If contactors are used to disconnect the battery, then current interruption is achieved, but the response time is delayed by many milliseconds
Solution Approach 1:
The patent replaces mechanical contactors with electronic switches controlled by a control unit that can respond in microseconds. The control unit detects current anomalies and actively reconfigures the battery modules to interrupt current flow electronically, achieving millisecond or microsecond response times compared to the many-millisecond response of mechanical contactors.
3Reliability
If precharge circuits with contactors and discharge resistors are used, then voltage control is achieved, but additional space and cost are required
Solution Approach 1:
The controllable switches in the modular battery pack serve multiple functions: they enable normal power delivery, provide current limiting during faults, and perform precharge/discharge operations. The same electronic switches that protect against overcurrent also manage voltage control and capacitor charging, eliminating the need for separate precharge circuits and discharge resistors.
Solution Approach 2:
The patent merges the functions of contactors, discharge resistors, and precharge circuits into the modular battery pack's electronic control system. The control unit integrates current limiting, voltage control, and capacitor management into a single coordinated system, reducing the number of discrete components and installation space required.
4Stability of the object's composition
If high capacitances are formed in the high-voltage system, then current fluctuations are avoided, but charging and discharging processes become slow
Solution Approach 1:
The patent uses dynamic reconfiguration of battery modules to manage current flow during charging and discharging. By actively switching modules between series and parallel connections, the system can rapidly adjust equivalent capacitance and resistance to optimize both current stability and charging/discharging speed, avoiding the fixed characteristics of passive capacitor banks.
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
Enables quick interruption or restriction of high currents without expensive hardware, improving electromagnetic compatibility and reducing installation space, while maintaining efficient power delivery and modulation for electric motor operation.
Implementation Method 1
the modules are electrically connected to one another to form a section having a first and a second section end and the two section ends are connected to a respective high-voltage connection
Implementation Method 2
The at least two switches of a respective module can interrupt a battery current I or interconnect the respective energy store at least in series or parallel with or to bypass the respective energy store of the respectively adjacent module
Implementation Method 3
at least one inductance L is arranged upstream of at least one high-voltage connection within a circuit of the battery pack, as a result of which the DC voltage V provided by the battery control unit by means of the modules is used to limit a magnitude of a change of current dI/dt in accordance with V=L·dI/dt
Data Source
AI summary
The invention relates to a method and system for electronic current control for a flexible DC battery pack, in which the battery pack has a plurality of flexibly interconnectable modules having a respective energy store and at least two respective controllable switches and the modules are electrically connected to one another to form a section having a first and a second section end and the two section ends are connected to a respective high-voltage connection, in which the at least two switches of a respective module interrupt a battery current I or interconnect the respective energy store at least in series or parallel with or to bypass the respective energy store of the respectively adjacent module, in which the flexible interconnection of the modules is controlled by a battery control unit and hence a prescribed DC voltage V is provided.