Power Conversion Apparatus Using Segmented Converters
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Solution Overview
Problem
Conventional power conversion apparatuses face challenges in miniaturization due to the need for multiple silicon carbide elements in series, which increase resistance losses and component count, and multi-leveling methods that require numerous capacitors and switching elements, making it difficult to reduce the size of the converter device while maintaining high voltage withstand and low switching losses.
Innovation Solution
A power conversion apparatus comprising a single-phase 2-level converter and a single-phase 3-level converter connected in series, with a bidirectional bypass switch and an overvoltage suppression circuit, using silicon carbide devices for low switching loss and silicon devices for high breakdown strength, respectively, to reduce the number of parts and switching losses, and control the output voltage through a control module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silicon carbide elements are arranged in series to withstand high voltage, then high voltage capability is achieved, but resistance losses increase and the total number of components increases
Solution Approach 1:
The patent segments the high voltage conversion task into multiple lower voltage level converters connected in series. Each level converter handles a portion of the total voltage, allowing the use of lower voltage-rated switching elements with lower on-resistance, thereby reducing overall resistance losses while achieving the required high voltage capability through the series connection of multiple segmented stages.
2Quantity of substance
If multi-leveling is adopted to reduce the number of capacitors, then the number of capacitors is decreased, but the number of switching elements increases with the number of levels
Solution Approach 1:
The patent employs switching elements that serve multiple functions across different operating modes and voltage levels. The same switching elements are utilized in various switching patterns to achieve different output voltage levels, eliminating the need for additional dedicated switching elements for each voltage level, thus reducing the total count while maintaining multi-level capability.
3Reliability
If protective circuits with discharge resistors are added to suppress capacitor overvoltage, then overvoltage suppression is achieved, but the protective circuit capacity must withstand large electric current causing the circuit to become larger
Solution Approach 1:
The patent incorporates preliminary overvoltage prevention measures through controlled switching sequences and voltage balancing techniques that prevent overvoltage conditions from occurring in the first place. By maintaining capacitor voltages within safe operating ranges through proactive control, the need for large-capacity discharge resistors and protective circuits is minimized, reducing the overall size of protective components.
Data Source
AI summary
A power conversion apparatus comprises a first converter connected to a second converter. The first converter includes a first capacitor and the second converter includes a second capacitor connected in series to a third capacitor. The capacitors are each connected in parallel with a respective resistor. The power conversion apparatus also includes a bypass switch connected in parallel to the first converter and in series to the second converter. A control module is configured to control a single-phase output voltage by operation of the first converter, the second converter, and the bypass switch.