Power Conversion Device Switching Time Control
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Solution Overview
Problem
Existing electric power conversion devices cannot prevent commutation failure, as they only compensate for voltage errors and do not address the underlying switching issues.
Innovation Solution
The introduction of a switching time calculating section and a control signal generating section that manage switching times for the switching elements in the power conversion device, ensuring equal allocation of switching times between the first and second half periods to prevent overlap and commutation failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If compensation quantity calculating means is used to correct output voltage command, then voltage error is compensated, but commutation failure cannot be prevented
Solution Approach 1:
The invention calculates the required commutation time in advance based on the relationship between output voltage command and input voltage, and uses this pre-calculated time to determine switching timing. This preliminary calculation of switching timing prevents commutation failure by ensuring sufficient time for current transfer, rather than merely compensating for voltage errors after the fact.
2Productivity
If switching time is not equally allocated between half periods, then switching operations may overlap, but commutation failure occurs
Solution Approach 1:
The invention introduces asymmetry in the switching timing arrangement by equally allocating the calculated commutation time to both half periods. This symmetric treatment of otherwise asymmetric switching operations prevents overlap between switching events, ensuring reliable commutation while maintaining efficient operation.
3Adaptability or versatility
If switching operations are not synchronized, then operational flexibility is maintained, but switching overlap occurs causing commutation failure
Solution Approach 1:
The invention uses feedback by continuously monitoring the output voltage command and input voltage to calculate the required commutation time, then applies this calculated time to synchronize switching operations. This feedback mechanism ensures that switching timing adapts to changing operating conditions while preventing overlap and commutation failure.
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 calculated first switching time. The second switching time is such that, in one period of the alternating current electric power outputted from the conversion circuit, the second switching time included in a first half period of the one period is equal to the second switching time included in a second half period of the one period.