Vehicle Control Apparatus Inverter Heating Ripple Management
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Solution Overview
Problem
Existing methods for controlling three-phase AC motors, such as PWM control, face issues with increased ripple in DC voltage and heating of switching elements, particularly at low motor revolutions, leading to malfunction and unstable motor control.
Innovation Solution
A vehicle control apparatus that selectively performs either a center value correction or a third harmonic signal correction based on DC voltage or temperature conditions to manage heating and ripple, using a modulator, correctors, and a controller to generate modulation signals and control the inverter operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the center value of phase voltage command signals is offset-corrected to reduce heating of switching elements, then heating of switching elements is reduced, but ripple in DC voltage increases
Solution Approach 1:
The patent dynamically switches between two correction methods (center value offset correction and third harmonic signal correction) based on operating conditions such as motor speed and DC voltage level. This dynamic adaptation allows the system to optimize performance across different operating ranges, reducing heating at low speeds while managing ripple at higher voltages.
Solution Approach 2:
The patent changes the correction parameters based on operating conditions. When DC voltage is below a threshold, third harmonic signal correction is applied; when DC voltage is above the threshold, center value offset correction is applied. This parameter change strategy resolves the contradiction by adapting the correction method to the specific operating state.
2Object-generated harmful factors
If third harmonic signal correction is applied to reduce ripple in DC voltage, then ripple is reduced, but heating of switching elements increases
Solution Approach 1:
The system dynamically selects which correction method to apply based on real-time operating conditions. At low motor speeds where heating is the primary concern, center value offset correction is used. At higher speeds where ripple becomes more problematic, third harmonic signal correction is applied. This dynamic selection resolves the contradiction by addressing the dominant issue at each operating point.
Solution Approach 2:
The correction strategy changes parameters based on operating conditions including motor speed and DC voltage level. The system transitions between correction methods at defined thresholds, allowing optimal performance across the full operating range while managing both heating and ripple concerns.
3Loss of energy
If center value of modulation signals is corrected to reduce loss in inverter, then loss in inverter is reduced, but zero vector period is extended causing ripple increase
Solution Approach 1:
The patent changes the correction approach based on DC voltage thresholds. When DC voltage is below the threshold, third harmonic signal correction is applied which reduces ripple. When DC voltage is above the threshold, center value offset correction is applied which reduces inverter loss. This parameter-based switching resolves the contradiction between loss reduction and ripple control.
Data Source
AI summary
A vehicle control apparatus is provided with: a modulator configured to generate modulation signals; a first corrector configured to perform a first correction process in which a center value of the modulation signals is corrected to reduce a loss in the inverter; a second corrector configured to perform a second correction process in which an amplitude shift and a phase shift of the third harmonic signal with respect to the voltage command signals are reduced; and a controller configured (i) to control the first corrector to perform the first correction process if the DC voltage is greater than or equal to first predetermined voltage and (ii) to control the second corrector to perform the second correction process if the DC voltage is less than the first predetermined voltage, when a number of revolutions of the AC motor is less than a predetermined number of revolutions.