Power Conversion Device Switching Control for Commutation Failure
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Solution Overview
Problem
Existing electric power conversion devices cannot prevent commutation failure, which occurs during the switching process in power conversion systems.
Innovation Solution
The solution involves controlling the switching elements in the electric power conversion device by transitioning from one switching state to another in a manner that reduces the number of switchings, specifically by turning off one switching element of either the upper arm or lower arm circuit and maintaining the on-state of the other, thereby preventing commutation failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple switching elements are switched during commutation, then the power conversion can be completed, but the commutation failure occurs due to excessive switching operations
Solution Approach 1:
The patent extracts and eliminates unnecessary switching operations from the commutation process. By identifying that only one switching element needs to be switched during commutation rather than multiple elements, the invention removes redundant switching actions that cause commutation failures, thereby maintaining power conversion functionality while improving commutation reliability
Solution Approach 2:
The patent inverts the conventional commutation approach by maintaining the on-state of switching elements instead of repeatedly switching them off and on. This inversion of the switching strategy reduces the number of switching operations from multiple to just one, preventing commutation failure while completing the power conversion process
Data Source
AI summary
An electric power conversion device comprises a conversion circuit having bi-directionally switchable plural pairs of switching elements connected to respective phases and converting an inputted AC power into an AC electric power. A first switching time is calculated using detected voltages detected by voltage sensors and an output command value. A second switching time is calculated using a carrier and the first switching time. A control signal generating section generates control signals to switch on and off of the switching elements using the first switching time and second switching time. In a case where a state is transited from the first switching time to the second switching time, a controller turns off one of on a state switching elements of either one of an upper arm circuit or a lower arm circuit and maintains on state of the other of the on state switching elements of the other arm circuit.