Inverter Mode Switching With PWM-Synchronized Dead Time Control
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Solution Overview
Problem
Two-stage inverters in open-end winding machines face safety issues during mode switching due to potential short circuits when transitioning between modes, particularly when mode switching timing synchronization is not accurately synchronized.
Innovation Solution
An apparatus and method for controlling inverters that includes a first and second inverter unit, a mode switching unit, and a control unit to manage mode switching through precise timing synchronization using PWM signals and dead time adjustments based on current magnitude, ensuring safe transitions between one-stage and two-stage inverter modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mode switching is performed in a two-stage inverter system, then the output capacity and efficiency are improved, but short circuits may occur during mode transitions
Solution Approach 1:
The control unit calculates dead time in advance based on the magnitude of electric current flowing immediately before mode switching. This preliminary calculation ensures that the switching transition accounts for the current state, preventing short circuits while enabling mode changes. The dead time is determined before the actual switching occurs, allowing safe transition between one-stage and two-stage inverter modes.
Solution Approach 2:
The system dynamically adjusts the dead time parameter based on the magnitude of electric current. By changing the dead time parameter according to current conditions, the system optimizes the switching process to prevent short circuits while maintaining high output capacity and efficiency during mode transitions.
2Reliability
If dead time is extended to prevent short circuits, then safety is improved, but switching response time increases
Solution Approach 1:
The dead time parameter is dynamically adjusted based on the magnitude of electric current flowing before mode switching. When current magnitude is low, a shorter dead time suffices, reducing time loss. When current magnitude is high, a longer dead time is applied to ensure safety. This adaptive parameter change optimizes both safety and switching response time.
Solution Approach 2:
Instead of applying a fixed excessive dead time in all conditions, the system applies only the necessary dead time based on current magnitude. This partial action approach ensures safety is maintained while minimizing unnecessary time delays during mode switching operations.
Data Source
AI summary
An apparatus for enabling an inverter to switch between modes includes: a first inverter unit; a second inverter unit; a load connected between the first inverter unit and the second inverter unit; a mode switching unit connected between the load and the second inverter unit; and a control unit configured to drive the load in a one-stage inverter mode or a two-stage inverter mode by performing control that turns on or off the mode switching unit. In particular, when an inverter switches between modes, the control unit performs mode switching in accordance with correct mode switching timing synchronization for PWM signal output.