Variable Voltage Battery System With Module Coupling Units
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Solution Overview
Problem
Conventional battery systems for vehicles and stationary applications face challenges in meeting variable voltage requirements and ensuring safety due to high demands on switches and disconnecting devices, which increase costs and risk for maintenance personnel.
Innovation Solution
A battery system with a DC voltage intermediate circuit, an AC converter, and an electric motor, where a control unit manages a battery module string with coupling units that can switch and disconnect battery cells to set the voltage variable and deactivate defective modules, eliminating the need for separate charging and disconnecting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high number of battery cells are connected in series to meet voltage requirements, then the output voltage increases, but the current carrying capacity is limited by individual cell constraints
Solution Approach 1:
The battery system is divided into multiple battery modules, each containing series-connected battery cells. These modules are then connected in parallel groups to achieve both high voltage (through series connection of modules) and high current capacity (through parallel connection of modules), resolving the contradiction between voltage requirements and current carrying capacity
Solution Approach 2:
A DC voltage intermediate circuit with a capacitor is introduced as an intermediary between the battery and the inverter. This intermediate circuit buffers voltage fluctuations and allows the battery to operate at optimal voltage points while the capacitor handles transient current demands, effectively decoupling the voltage and current constraints
2Reliability
If separate charging and disconnecting devices are provided for safety, then the reliability of the system improves, but the device complexity and costs increase
Solution Approach 1:
The charging switch and disconnecting switch are merged into a single switch per battery module. This integrated switch performs both functions: it disconnects the battery module for safety when needed, and it enables charging current flow when closed. This eliminates the need for separate charging and disconnecting devices, reducing complexity while maintaining safety
Solution Approach 2:
The switch in each battery module is designed to serve multiple functions: it acts as a disconnecting switch for safety, a charging switch for power input, and a control point for isolating defective modules. This multi-functional design reduces the total number of components needed in the system
3Stability of the object's composition
If the capacity of the capacitor in the DC voltage intermediate circuit is increased to stabilize voltage, then the voltage stability improves, but the device complexity and cost increase
Solution Approach 1:
Instead of relying solely on a large static capacitor, the system uses dynamically controllable switches in each battery module that can rapidly connect or disconnect modules in response to voltage fluctuations. This dynamic response allows for effective voltage stabilization with a smaller capacitor, as the active switching compensates for transient demands
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 allows for adaptable voltage settings, increased reliability by isolating defective modules, and enhanced safety without the need for additional disconnecting devices, enabling continued operation with reduced output rather than system failure.
Implementation Method 1
The DC voltage intermediate circuit comprises a capacitor (11)
Data Source
AI summary
A battery system includes a battery, a DC voltage intermediate circuit connected to the battery, an inverter connected to the DC voltage intermediate circuit and an electric motor connected to the inverter. The DC voltage intermediate circuit includes a capacitor, and the battery includes a battery module line having a plurality of battery modules which are connected in series, and a control unit. Each battery module includes a coupling unit and at least one battery cell which is connected between a first input and a second input of the coupling unit. The coupling unit is configured to connect the at least one battery cell between a first terminal of the battery module and a second terminal of the battery module in response to a first control signal, and to connect the first terminal to the second terminal in response to a second control signal.