Power Converter Mode Switchover Timing for Stable 2-Level/3-Level Control
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Solution Overview
Problem
Conventional power conversion devices experience instability and increased switching loss during mode switchover between 2-level and 3-level operations due to instantaneous off-switching of switching elements, leading to current disturbances and torque variations.
Innovation Solution
A power conversion device with a control unit that executes first switchover control between 2-level and 3-level operations at a timing when a set semiconductor element is ON, based on the polarity of the voltage command, using a level switchover determination unit to stabilize the mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switchover control is executed when switching between 2-level and 3-level operations, then operation mode can be optimized for efficiency, but current disturbances and torque variations occur due to instantaneous off-switching of semiconductor elements
Solution Approach 1:
The control unit determines the switchover timing in advance by monitoring the ON state of semiconductor elements before executing the mode switch. This preliminary determination ensures that switchover occurs at an appropriate moment when current flow through intermediate potential switches is minimized, preventing current disturbances and torque variations while maintaining conversion efficiency optimization.
Data Source
AI summary
A controlling circuitry of a power converter has a 3-level operation mode of outputting AC voltage composed of 3-level voltages of a DC circuit by performing ON/OFF control of semiconductor elements, and a 2-level operation mode of outputting AC voltage composed of 2-level voltages of the DC circuit by performing ON/OFF control of the semiconductor elements. The controlling circuitry executes first switchover control for switching between the 2-level operation mode and the 3-level operation mode, at a timing when, among the semiconductor elements, a set semiconductor element according to a polarity of a voltage command for controlling the power converter is continuing to be ON.