Power Converter Control Device for Torque Pulsation Reduction
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Solution Overview
Problem
Conventional power conversion devices, such as inverters, suffer from torque pulsation and reduced responsiveness due to asymmetry in output voltage and the need to adjust carrier wave frequency in synchronous PWM control, as well as limited feedback control during negative periods in AC current waveform control.
Innovation Solution
A control device for power conversion systems that includes a comparator for generating pulse signals based on voltage command and carrier wave comparisons, and a reset signal unit that synchronizes the carrier wave with the voltage command, reducing torque pulsation and enhancing responsiveness by suppressing sideband waves and maintaining symmetry in PWM signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If synchronous PWM control is used to maintain symmetry in output voltage, then torque pulsation is reduced, but carrier wave frequency adjustment is required which lowers responsiveness
Solution Approach 1:
The invention applies periodic action by resetting the carrier wave to a predetermined value at regular intervals (every cycle or every N cycles). This periodic reset maintains the symmetry of the output voltage waveform, reducing torque pulsation, while the fixed reset timing avoids the need for frequency adjustment, preserving system responsiveness.
2Device complexity
If feedback control is performed only on positive period of AC current waveform, then control complexity is reduced, but responsiveness of current control system is lowered
Solution Approach 1:
The invention segments the control period into positive and negative periods, applying feedback control during the positive period and using the stored and inverted waveform for the negative period. This segmentation allows the system to achieve full-cycle control effectiveness while performing computations only during the positive period, thus maintaining responsiveness without requiring complex simultaneous dual-period processing.
3Speed
If asynchronous PWM control is used with fixed carrier wave frequency, then responsiveness is improved, but symmetry is lost in output voltage causing large torque pulsation
Solution Approach 1:
The invention applies preliminary action by storing the waveform output during the positive period in a storage unit before the negative period begins. This preliminary storage and preparation of the waveform data allows the system to quickly generate the negative period waveform through inversion without complex real-time calculations, maintaining responsiveness while ensuring symmetry.
Data Source
AI summary
There are provided a voltage command calculator that calculates a voltage command value that is a command value of an AC voltage to be applied to a rotary electric machine that is driven by a power conversion device, a carrier wave generator that generates a carrier wave, a comparator that generates a pulse signal to be supplied to the power conversion device on the basis of a comparison result between the voltage command value and the carrier wave, and a reset signal receiving unit that changes a value of the carrier wave into a predetermined value when a predetermined reset signal is input.