Motor Regeneration V/F Control Across High and Low Speed Ranges
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Solution Overview
Problem
Existing power conversion devices face challenges in maintaining high regenerative torque during deceleration in high speed ranges while minimizing electric motor loss in low speed ranges, as previous methods either reduce regenerative torque or increase electric motor loss.
Innovation Solution
The power conversion device adjusts the V/F characteristic during regeneration time to be higher in high output frequency regions and lower in low output frequency regions compared to powering time, allowing for increased regenerative torque and reduced electric motor loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the V/F characteristic during regeneration time is set to a smaller value than during powering time, then regenerative torque is improved in high speed range, but electric motor loss increases in low speed range
Solution Approach 1:
The patent divides the output frequency range into two segments: a first frequency range (lower frequencies) and a second frequency range (higher frequencies). For the first frequency range, the V/F characteristic during regeneration is set equal to or smaller than powering to reduce motor loss. For the second frequency range, the V/F characteristic during regeneration is set larger than powering to improve regenerative torque. This segmentation allows optimization of different frequency regions independently.
Solution Approach 2:
The patent applies different V/F characteristic strategies to different frequency regions. In the low frequency region, a smaller or equal V/F ratio is applied locally to reduce motor losses. In the high frequency region, a larger V/F ratio is applied locally to enhance regenerative torque. This local quality approach allows the system to optimize performance characteristics for specific operating conditions rather than using a uniform strategy across all frequencies.
2Power
If the V/F characteristic is uniformly set smaller during regeneration time, then regenerative performance is improved, but motor efficiency deteriorates across all speed ranges
Solution Approach 1:
The patent segments the frequency spectrum into two distinct ranges with different V/F characteristic strategies. The first frequency range uses a conservative V/F setting (equal to or smaller than powering) to maintain motor efficiency, while the second frequency range uses an aggressive V/F setting (larger than powering) to maximize regenerative performance. This segmentation resolves the contradiction by applying appropriate strategies only where needed.
Solution Approach 2:
The patent changes the V/F characteristic parameter dynamically based on the output frequency range. Instead of using a single uniform V/F ratio, the system adjusts the V/F parameter according to the operating frequency, selecting different values for different frequency ranges to balance regenerative performance and motor efficiency.
3Loss of energy
If the V/F characteristic is uniformly set larger during regeneration time, then electric motor loss is reduced, but regenerative torque decreases in high speed range
Solution Approach 1:
The patent divides the operating frequency range into two segments and applies different V/F strategies to each. In the first frequency range, a smaller or equal V/F characteristic is applied to reduce motor loss. In the second frequency range, a larger V/F characteristic is applied to improve regenerative torque. This segmentation allows the system to avoid the drawback of uniform settings.
Solution Approach 2:
The patent applies local quality by tailoring the V/F characteristic to the specific needs of each frequency region. In regions where motor loss is the primary concern (low frequencies), a conservative V/F setting is applied locally. In regions where regenerative torque is the primary concern (high frequencies), an aggressive V/F setting is applied locally.
Data Source
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AI summary
Provided is a control method for, when decelerating an electric motor, ensuring regenerative torque in a high speed region and reducing electric motor loss in a low speed region. In a power conversion device of the present invention, during deceleration time, a V/F characteristic is set higher in a high speed region than during powering time and the V/F characteristic is set lower in a low speed region than during the powering time, thereby providing a control method for enhancing a regeneration performance in the high speed region during deceleration time and reducing electric motor loss in the low speed region. This makes it possible to provide a power conversion device in which both improvement of regeneration ability and improvement of electric motor efficiency can be achieved.