Power Conversion Device Switching Time Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power conversion devices cannot prevent commutation failure, which occurs due to inadequate compensation for voltage errors during switching operations.
Innovation Solution
Incorporating a switching time calculating section and a control signal generating section to determine and manage the switching times of switching elements in the power conversion device, ensuring a secure interval between switching operations to prevent overlap and commutation failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching operations are performed without adequate time interval management, then switching speed and productivity are improved, but commutation failure occurs due to overlap between switching operations
Solution Approach 1:
The control signal generating section calculates and determines the first switching time and second switching time in advance before the actual switching operations occur. By pre-determining the timing of switching operations and ensuring adequate intervals between them, the system prevents commutation failure while maintaining high switching speed. This preliminary timing calculation eliminates the need for reactive adjustments during switching operations.
2Ease of manufacture
If voltage compensation is applied only after commutation failure occurs, then manufacturing simplicity is maintained, but commutation failure cannot be prevented
Solution Approach 1:
The control signal generating section performs preliminary calculations of the first switching time and second switching time based on voltage magnitude detecting means outputs and polarity determination means outputs. By determining switching timings in advance rather than reacting after commutation failure, the system prevents commutation failure while maintaining relatively simple control architecture. The preliminary timing determination includes calculating adequate intervals between switching operations.
Solution Approach 2:
The system uses feedback from voltage magnitude detecting means and polarity determination means to continuously monitor the actual voltage state and adjust the switching time calculations accordingly. This feedback mechanism ensures that the calculated first switching time and second switching time account for actual voltage conditions, preventing commutation failure while adapting to varying operating conditions.
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 in a form of a time which is a subtraction of the first switching time from a half period of a carrier and, using this time, control signals to switch on and off of the switching elements are generated.