Diode Neutral-Point-Clamped Inverter Current Limiting Control
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Solution Overview
Problem
Current current limiting methods for diode neutral-point-clamped three-level inverters result in excessive voltage stress on switching tubes, leading to potential failure when exiting a current-limiting state due to high voltage stress.
Innovation Solution
A current limiting control method that gradually turns on inside switching tubes after an overcurrent signal turns invalid, allowing only one tube to initially turn on, followed by the other after a delay, and then restores normal drive sequences, ensuring that both inside and outside switching tubes bear single bus voltage, reducing voltage stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all switching tubes are turned on simultaneously when exiting current-limiting state, then the inverter returns to normal operation quickly, but the switching tubes bear double bus voltage causing excessive voltage stress and potential failure
Solution Approach 1:
The patent divides the switching tube turn-on process into sequential stages rather than simultaneous activation. When exiting current-limiting state, the controller first turns on only the inside switching tube that has been off longest, waits for a delay period, then turns on the other inside switching tube. This segmentation prevents both tubes from bearing double bus voltage simultaneously, resolving the contradiction between quick response and voltage stress reduction.
2Use of energy by moving object
If normal drive sequence is restored immediately when current-limiting state exits, then system efficiency is maximized, but voltage stress on switching tubes exceeds safe limits
Solution Approach 1:
The patent implements preliminary action by introducing a delay period before restoring the normal drive sequence. When exiting current-limiting state, the controller activates only one inside switching tube during this delay period, allowing voltage stress to remain at safe single bus voltage levels. After the delay, the other switching tube is activated and normal operation resumes. This preliminary staged activation protects switching tube reliability while transitioning to efficient normal operation.
Data Source
AI summary
The present disclosure discloses a current limiting control method for a diode neutral-point-clamped three-level inverter and a related circuit. When a current in switching tubes is lowered to a value not greater than a first preset current value, the current limiting control method for a diode neutral-point-clamped three-level inverter and the related circuit drive an inside switching tube of the switching tubes to be turned on; after a first delay time, drive another inside switching tube to be turned on; after a second delay time, control an inside switching tube to be turned off and the other inside switching tube to be normally turned on; and control all the switching tubes to be turned on or off according to a control time sequence of the diode neutral-point-clamped three-level inverter circuit.