Direct Power Conversion Apparatus Torque Harmonic Control
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Solution Overview
Problem
Existing direct power conversion apparatuses face challenges in suppressing vibration of load apparatuses connected to motors due to increased motor current peaks, which can exceed the motor's or device's allowable limits, leading to demagnetization or mechanical stress.
Innovation Solution
A direct power conversion apparatus with a converting unit and control unit that generates motor torque waveforms including specific harmonic frequencies, such as fourth and sixth harmonics of the power source frequency, and second and third harmonics of the fundamental frequency, to reduce vibration and peak current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If torque control is performed to suppress vibration by increasing the fundamental frequency component of load torque, then vibration suppression is improved, but motor current peak value increases and may exceed upper limit
Solution Approach 1:
The patent applies parameter changes by introducing harmonic components (4th and 6th harmonics of power source frequency, 2nd and 3rd harmonics of fundamental frequency) into the torque waveform. These harmonic parameters modify the torque characteristics to suppress vibration while controlling current peaks through specific phase relationships between harmonics and fundamental frequency components
Solution Approach 2:
The patent utilizes periodic action by synchronizing harmonic components with specific frequencies related to the power source frequency and load torque fluctuation period. The harmonic components are applied periodically at frequencies that create constructive interference for vibration suppression while maintaining current within acceptable limits through controlled phase relationships
2Strength
If vibration suppressing component is decreased to prevent motor current from exceeding upper limit, then motor current is controlled, but vibration of load apparatus is increased
Solution Approach 1:
The patent employs a composite torque waveform consisting of multiple frequency components (fundamental frequency and harmonic components). This composite approach combines the vibration suppression effect of the fundamental frequency with the current-limiting effect of harmonics, achieving both vibration reduction and current control simultaneously through the synergistic interaction of different frequency components
Data Source
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AI summary
In order to suppress vibration with a motor (5) a load torque of which periodically fluctuates, an output torque of the motor (5) is controlled to be periodically changed. In this case, in order to increase a vibration suppressing component by a direct power conversion apparatus, at least one of first control and second control is performed. In the first control, an output torque having a waveform including a fundamental frequency component of the load torque a fundamental frequency of which is a frequency in accordance with a fluctuation period of the load torque and at least one of a fourth harmonic and a sixth harmonic of a power source frequency of an AC power source (6) is generated. In the second control, the output torque having a waveform including at least one of a second harmonic and a third harmonic of the fundamental frequency of the load torque and a second harmonic of the power source frequency of the AC power source (6) is generated.