OBC Capacitor Branch Layout for Short-Circuit Voltage Stability
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Solution Overview
Problem
Current on-board chargers (OBCs) for electric vehicles face instability and high operating costs due to the limitations of electrolytic capacitors, which can lead to circuit failure when a direct current conversion module is short-circuited.
Innovation Solution
The proposed power conversion apparatus incorporates a first capacitor branch with electrolytic capacitors for voltage stabilization and a second capacitor branch with film capacitors for filtering and voltage division. This configuration ensures that if a direct current converter is short-circuited, the film capacitors can withstand the increased voltage, maintaining the stability of the non-faulty converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electrolytic capacitors are used in direct current conversion modules, then the charging efficiency is improved through voltage conversion, but the reliability deteriorates when a module is short-circuited causing cascading failures
Solution Approach 1:
The patent divides the capacitor system into two independent segments: electrolytic capacitors dedicated to voltage conversion in direct current modules, and film capacitors dedicated to voltage stabilization and filtering in the main circuit. This segmentation ensures that failures in one segment do not cascade to the other, resolving the reliability issue while maintaining charging efficiency.
Solution Approach 2:
The patent introduces film capacitors as intermediary elements between the electrolytic capacitors and the power grid. These film capacitors act as a protective buffer that stabilizes voltage and filters interference, preventing direct voltage spikes from damaging electrolytic capacitors during short-circuit events.
2Power
If multiple electrolytic capacitors are connected in series to handle high voltage, then the voltage conversion capability is improved, but the operating cost increases due to higher replacement costs when damaged
Solution Approach 1:
The patent strategically places inexpensive film capacitors in the main circuit where they bear the brunt of voltage stress and potential failures. While film capacitors may need replacement, their lower cost compared to electrolytic capacitors reduces overall operating expenses. The electrolytic capacitors are protected from direct voltage spikes, extending their service life.
Solution Approach 2:
The patent implements prior cushioning by positioning film capacitors ahead of electrolytic capacitors in the voltage path. These film capacitors absorb voltage spikes and provide filtering before the voltage reaches the more expensive electrolytic capacitors, preventing premature failure and reducing replacement costs.
3Strength
If film capacitors are used instead of electrolytic capacitors in all positions, then the high-voltage withstand capability is improved, but the voltage stabilization capability deteriorates due to smaller capacitance values
Solution Approach 1:
The patent applies local quality by assigning different capacitor types to different circuit positions based on their specific requirements: electrolytic capacitors with large capacitance are placed where voltage stabilization is critical, while film capacitors with high voltage withstand capability are placed where voltage filtering and division are needed. This optimization ensures both stabilization and strength requirements are met.
Solution Approach 2:
The patent creates a composite capacitor system combining electrolytic and film capacitors in a coordinated architecture. The electrolytic capacitors provide bulk energy storage and voltage stabilization, while film capacitors provide high-voltage withstand capability and filtering. The synergistic combination achieves both voltage stabilization and high-voltage strength that neither type could achieve alone.
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
The use of film capacitors with high-voltage withstand characteristics improves the working stability of the power conversion apparatus and reduces operating costs by minimizing damage and replacement needs when faults occur.
Implementation Method 1
The first capacitor branch includes at least one electrolytic capacitor, and is configured to perform voltage stabilization on a voltage received by the power conversion apparatus, to obtain a first voltage
Implementation Method 2
The second capacitor branch includes a plurality of film capacitors connected in series, and is configured to: perform filtering on the first voltage
Implementation Method 3
perform voltage division on a first voltage obtained through filtering, to obtain a plurality of second voltages
Data Source
AI summary
A power conversion apparatus includes: a first capacitor branch, where the first capacitor branch includes at least one electrolytic capacitor, and is configured to perform voltage stabilization on a voltage received by the power conversion apparatus, to obtain a first voltage; a second capacitor branch, where the second capacitor branch includes a plurality of film capacitors connected in series, and is configured to: perform filtering on the first voltage, and perform voltage division on a first voltage obtained through filtering, to obtain a plurality of second voltages, where each film capacitor obtains one second voltage; and direct current converters in a one-to-one correspondence with the film capacitors, where an input end of each direct current converter is connected in parallel to the corresponding film capacitor; and the direct current converter is configured to perform voltage conversion on the second voltage output by the film capacitor.