Battery Inverter Control for Homogeneous Cell Current Balancing
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Solution Overview
Problem
Existing battery architectures for electromobility and stationary energy storage face challenges in maintaining balanced state of charge across cells, particularly when generating a line voltage, leading to potential imbalances and reduced battery performance.
Innovation Solution
A method for controlling electrochemical batteries that involves classifying and dynamically balancing the state of charge of individual cells by processing the classification of basic modules according to a circular permutation, ensuring homogeneous charging and discharging and readjusting balancing as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing is used to discharge the most charged cells by connecting resistors, then the state of charge of cells can be balanced, but energy is lost as heat and balancing time increases significantly
Solution Approach 1:
The patent introduces an intermediary energy storage device (capacitor or small battery) that acts as a mediator between the series-connected cells. This intermediary device temporarily stores energy from overcharged cells and transfers it to undercharged cells, enabling balancing without direct resistive discharge and minimizing energy loss.
Solution Approach 2:
The patent changes the operating parameters by using high-voltage switches to dynamically reconfigure the cell connections. Instead of maintaining fixed series connections, the system alternates between different series groupings, allowing cells to be selectively charged or discharged at controlled rates, thereby reducing excessive heat generation in balancing resistors.
2Loss of energy
If passive balancing uses low current values to avoid excessive heating, then energy loss is reduced, but balancing time increases significantly
Solution Approach 1:
The patent implements periodic switching between different cell groupings in series. By alternately connecting different sets of cells in series and using high-voltage switches to rapidly reconfigure connections, the system enables higher balancing currents to flow periodically without causing continuous excessive heating, thus reducing overall balancing time while maintaining acceptable energy loss.
Solution Approach 2:
The patent introduces dynamic reconfiguration of cell connections through high-voltage switches that can rapidly change the series groupings. This dynamic approach allows the system to adapt the current flow paths in real-time, enabling higher currents during brief intervals when safe, thereby accelerating the balancing process without sustained excessive heating.
3Power
If cells are connected in series to increase battery voltage, then voltage is increased, but the same current passes through all cells preventing individual state of charge adjustment
Solution Approach 1:
The patent segments the series-connected cells into multiple groups that can be independently controlled through high-voltage switches. By dividing the cell string into manageable segments and allowing selective connection of different segments, the system maintains high voltage operation while enabling individual or group-based state of charge adjustment for each segment.
Solution Approach 2:
The patent employs dynamic switching mechanisms that allow the series connection configuration to change over time. High-voltage switches enable the system to reconfigure which cells are in series at any given moment, allowing cells that would normally be constrained by series connection to have their current flow dynamically adjusted, thereby achieving individual state of charge control while maintaining high voltage output.
Data Source
AI summary
The present invention relates to a method for controlling a battery with integrated inverters comprising n basic cell modules (MEk) which supply a basic voltage Vcell and allow the application of a homogenous current to all the cells. More specifically, the method comprises a step of controlling the control signals (uik) from the basic modules (MEk) so as to provide the voltage waveform (VM1) on the basis of a selection of a group of q basic modules (MEk) according to a reference voltage setpoint Vref, where Vref=qVcell, determining a classification of the n basic modules, processing the classification of the plurality n according to a circular permutation of the positions of the basic modules (MEk) such that each basic module (MEk) of the plurality n is involved in producing the voltage waveform over a period that is the same for each module. The invention is applicable in the fields of electromobility and stationary energy storage.