Controllable Energy Store Charging via Stator Windings
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Solution Overview
Problem
Conventional energy storage systems in electric vehicles and wind turbines face reliability issues due to the series connection of battery cells, where a single cell failure can cause the entire system to fail, leading to potential safety threats and system breakdowns.
Innovation Solution
A controllable energy storage system with n parallel energy supply branches, each comprising series-connected energy storage modules with coupling units that can interrupt or bypass cells, allowing for charging through the electrical machine's stator windings and freewheeling diodes, enabling efficient and reliable charging of energy storage cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If battery cells are connected in series to achieve high overall voltage, then the voltage requirement is met, but the system reliability deteriorates because a single cell failure causes the entire energy store to fail
Solution Approach 1:
The energy store is divided into multiple independent battery module strands, where each strand contains series-connected battery modules. This segmentation allows individual strands to be isolated or bypassed without affecting other strands, maintaining system operation even when some cells fail.
Solution Approach 2:
Each battery module within a strand is equipped with individual coupling units that can independently control the state of that specific module. This local control capability allows selective bypassing or interrupting of individual modules or cells, preventing local failures from propagating to the entire system.
2Power
If additional battery cells are connected in parallel to increase maximum current, then the current capacity is improved, but the device complexity increases
Solution Approach 1:
The coupling units serve multiple functions: they act as switches for interrupting energy supply branches, as bypass switches for individual battery cells, and as control elements for pulse-width modulation to generate phase signals for the electrical machine. This multi-functionality reduces the need for separate components.
Solution Approach 2:
The inverter functionality is integrated into the battery system through the coupling units, which can generate phase signals for controlling the electrical machine. This merging of the pulse-controlled inverter with the battery structure eliminates the need for a separate inverter unit, reducing overall system complexity.
3Device complexity
If coupling units are used to provide phase signals for controlling the electrical machine, then the need for a separate pulse-controlled inverter is reduced, but the control complexity of the coupling units increases
Solution Approach 1:
The coupling units are designed to perform multiple functions simultaneously: switching individual battery cells in and out of the circuit, providing bypass paths for failed cells, and generating pulse-width modulated phase signals for electrical machine control. This consolidation reduces overall system complexity despite the enhanced control capabilities required.
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 enhances system reliability by allowing for the charging of energy storage cells with minimal additional hardware, reducing costs and space requirements, while ensuring even load distribution and avoiding undesired torques during charging.
Implementation Method 1
using the coupling units and the stator windings of the electrical machine operated as a step-up converter, with energy being supplied to the stator windings and stored there, which energy is then delivered to the energy storage cells to be charged
Implementation Method 2
at least two phases of the electrical machine can be connected to a positive pole of a charging device via at least one freewheeling diode
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a system for charging at least one power cell (5) in a controllable energy store (2) used for controlling and supplying electric power to an n-phase electric machine (1). The controllable energy store (2) has n parallel power supply branches (3-1, 3-2, 3-3), each of which includes at least two serially connected energy storage modules (4). Each energy storage module comprises at least one electric power cell (5) having an associated controllable coupling unit (6). The power supply branches (3-1, 3-2, 3-3) are connected to a reference bus (T-) and to one respective phase (U, V, W) of the electric machine (1). The coupling units (6) disconnect the respective power supply branch (3-1, 3-2, 3-3), bridge the associated power cells (5), or connect the associated power cells (5) to the respective power supply branch (3-1, 3-2, 3-3) in accordance with control signals. In order to allow at least one power cell (5) to be charged, at least two phases (U, V) of the electric machine (1) can be connected to a positive terminal of a charging device (10) by means of at least one respective freewheeling diode (9-U, 9-V), while the reference bus (T-) can be connected to a negative terminal of the charging device (10).