Multi-Level Converter Circuit for Battery Cell Balancing
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Solution Overview
Problem
Existing circuit arrangements for electric vehicles and hybrid vehicles face challenges in efficiently converting DC voltage from battery cells to AC voltage while managing voltage variations and preventing battery degradation, particularly due to the complexity added by DC/DC converters and the need for cell balancing schemes.
Innovation Solution
A multi-level converter circuit arrangement that includes multiple converter units connected in series, each with a switch arrangement and a control circuit generating pulse-width modulated output voltages based on control signals, allowing for adaptive duty cycles to manage voltage variations and balance charge states across battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC/DC converter is connected between the battery arrangement and the DC/AC inverter to provide constant DC supply voltage, then voltage variations are compensated, but system complexity increases
Solution Approach 1:
The patent combines the DC/DC converter and DC/AC inverter into a single multi-level converter unit. The converter integrates both voltage regulation functionality and AC inversion functionality, eliminating the need for separate DC/DC converter and inverter components while maintaining voltage stability and reducing overall system complexity.
Solution Approach 2:
The multi-level converter is designed to perform multiple functions simultaneously: it regulates DC voltage from the battery arrangement, converts DC to AC voltage for the motor, and provides cell balancing capabilities. This multi-functional design replaces what would traditionally require separate dedicated components for each function.
2Reliability
If cell balancing schemes are applied to prevent improper discharging of individual accumulator cells, then battery degradation is prevented, but additional circuit arrangements are required
Solution Approach 1:
The cell balancing functionality is integrated into the multi-level converter's control system. The converter uses its existing switch arrangement and control circuitry to perform cell balancing by selectively charging or discharging individual battery cells through the same power electronic components used for main power conversion, eliminating the need for separate balancing circuits.
Solution Approach 2:
The multi-level converter is designed to simultaneously handle main power conversion and cell balancing operations. The control system monitors individual cell voltages and adjusts switching patterns to redistribute charge among cells, providing battery protection as an additional function of the primary power conversion system.
3Reliability
If multiple converter units are connected in series to generate AC output voltage, then voltage stability and charge balancing are improved, but device complexity increases
Solution Approach 1:
The multi-level converter is divided into multiple converter units (first converter unit, second converter unit, etc.), each with its own charge storage unit and switch arrangement. These segmented units are connected in series to generate the AC output voltage, with each unit contributing a portion of the total voltage while maintaining independent control for stability and balancing.
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 effectively generates a stable AC output voltage with reduced complexity, efficient charge balancing, and lower power losses, enabling continuous oscillating signals like sinusoidal waves with minimal Total Harmonic Distortion, while preventing battery degradation.
Implementation Method 1
the switch arrangement being adapted to provide a pulse-width modulated output voltage having a duty cycle at the output terminals dependent on the control signal
Data Source
AI summary
In accordance with an embodiment, a method of operating a multi-level converter includes detecting a charge state of charge storage units of series connected converter units, assigning parameter sets to the converter units based on the detected charge states, and generating control signals coupled to switch arrangements of the converter units based on the parameter sets.