Power Conversion Device Capacitor Segmentation for Loss Reduction
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Solution Overview
Problem
Conventional power conversion devices fail to adequately reduce total loss in inverter and motor systems, particularly in electric vehicle applications, as they prioritize inverter loss reduction over motor loss, leading to increased high-frequency iron loss and capacitor size issues.
Innovation Solution
A power conversion device with an inverter, parallel-connected capacitors, and a switch circuit controlled by a control circuit to switch between 2-level and 3-level operations based on torque and rotational speed commands, minimizing total loss by optimizing capacitor usage and operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 2-level operation is performed using only 3-level operation capacitors connected in series, then inverter operation is maintained, but capacitor size increases
Solution Approach 1:
The patent segments the capacitor configuration into two distinct paths: one using only the series-connected 3-level operation capacitors for 3-level operation, and another using both the series-connected capacitors and additional capacitors for 2-level operation. This segmentation allows the system to use the minimal necessary capacitor configuration for each operation mode, preventing unnecessary capacitor size increase while maintaining reliable inverter operation.
Data Source
AI summary
An inverter is provided for driving a motor. A first capacitor, and a second capacitor including capacitors connected in series, are connected in parallel to a DC power supply. A switch circuit having switching elements is connected between the inverter and the second capacitor. A control circuit is provided for controlling the inverter and the switch circuit. The control circuit performs control to switch the switch circuit so as to supply current from the second capacitor to the inverter during 3-level operation, and supply current from both of the first capacitor and the second capacitor to the inverter during 2-level operation.