Power Conversion Device LC Resonance Suppression
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Solution Overview
Problem
Conventional power conversion devices fail to adequately suppress overvoltage due to the LC resonance phenomenon, especially when flux-weakening control is applied, leading to unstable motor control and potential component damage.
Innovation Solution
A power conversion device with a d-axis current controller, q-axis current controller, and gate signal generation section that includes a voltage detection system, filter, multiplier, and compensation sections to generate gate signals that correct d-axis and q-axis voltage commands, effectively suppressing overvoltage by adjusting the output power of the inverter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flux-weakening control is applied to drive AC motor at high speed, then motor speed range is extended, but overvoltage due to LC resonance occurs causing unstable control
Solution Approach 1:
The patent implements feedback control by detecting DC link voltage, extracting its AC component, and using this information to correct both d-axis and q-axis voltage commands. This closed-loop feedback mechanism dynamically compensates for resonance effects while maintaining flux-weakening control, thereby extending speed range without compromising control stability
Solution Approach 2:
The patent changes control parameters by correcting both d-axis voltage command (vd*) and q-axis voltage command (vq*) based on the detected resonance characteristics. This dual-parameter adjustment allows the system to adapt to resonance conditions while maintaining the flux-weakening control needed for high-speed operation
2Device complexity
If only q-axis voltage command is corrected to suppress resonance, then implementation is simple, but overvoltage suppression is insufficient when flux-weakening control is applied
Solution Approach 1:
The patent segments the voltage control into two independent components: d-axis voltage correction and q-axis voltage correction. Each axis is corrected separately based on the detected resonance characteristics, allowing precise control of each component while maintaining overall system simplicity and effectiveness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reliably prevents overvoltage due to LC resonance, even during flux-weakening control, ensuring stable operation and preventing component damage by accurately controlling the inverter's output power.
Implementation Method 1
a converter for converting AC voltage from an AC power supply to DC voltage
Implementation Method 2
an inverter for converting the DC voltage of the capacitor to AC voltage
Implementation Method 3
an LC resonance circuit is formed by an inductance component L which the AC power supply has and the capacitor C of the DC link section. When the resonance frequency of the LC resonance circuit coincides with the frequency six times as large as the power supply frequency, voltage of the DC link section in the power conversion device greatly oscillates
Data Source
AI summary
A power conversion device includes a high-pass filter for extracting an AC component of voltage Vdc of a DC link section, a multiplier for multiplying output VdcAC of the high-pass filter by a first gain K1 and outputting the result, a multiplier for multiplying output of the multiplier by a second gain K2 and outputting the result as a d-axis voltage correction signal vdcmp*, and a multiplier for multiplying output of the multiplier by a third gain K3 and outputting the result as a q-axis voltage correction signal vqcmp*. The gate signal generation section generates gate signals on the basis of a signal vd1 obtained by adding the d-axis voltage correction signal vdcmp* to a d-axis voltage command value vd* and a signal vq1 obtained by adding the q-axis voltage correction signal vqcmp* to a q-axis voltage command value vq*.