Randomized Zero-Sequence PWM for Quieter Electric Drive Control
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Solution Overview
Problem
Existing methods for reducing pulse width modulation (PWM) noise in vehicle cabins, such as higher switching frequencies or probabilistic approaches, either rely on masking noise sources or induce power losses, making them inefficient and difficult to calibrate across varying driver behaviors and ambient conditions.
Innovation Solution
Randomizing the zero-sequence voltage of an electric machine's powertrain within a potential range, adjusting the voltage reference signal to decrease ambient acoustic noise without affecting torque production, thereby reducing PWM acoustic emissions across all operating points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If higher switching frequencies are used to reduce audible PWM noise, then acoustic emissions are reduced, but power losses increase and fuel economy deteriorates
Solution Approach 1:
The patent changes the parameter of zero-sequence voltage from a fixed value to a randomized value within a potential range. This randomization disperses the spectral energy of PWM switching noise across a broader frequency spectrum, reducing audible noise without requiring higher switching frequencies, thereby avoiding increased power losses
Solution Approach 2:
The patent introduces dynamic randomization of the zero-sequence voltage parameter during PWM operation. By continuously varying the zero-sequence voltage within its potential range according to a random distribution, the system dynamically shifts the spectral content of switching noise, reducing audible emissions while maintaining efficient operating frequencies
2Object-affected harmful factors
If higher switching frequencies are used to reduce audible PWM noise, then acoustic emissions are reduced, but system costs increase
Solution Approach 1:
The patent modifies the zero-sequence voltage parameter through randomization within its existing potential range, achieving noise reduction without hardware modifications or increased system complexity. The approach uses software-based control to vary the voltage parameter, avoiding additional power circuit costs
3Object-affected harmful factors
If probabilistic PWM switching frequency selection is used, then noise reduction is achieved, but torque production is negatively impacted
Solution Approach 1:
The patent extracts the zero-sequence voltage component from the PWM control and randomizes it independently. This separation allows the fundamental torque-producing components of the PWM signal to remain unchanged while only the zero-sequence component is randomized to achieve noise reduction, preserving torque production
Solution Approach 2:
The patent changes only the zero-sequence voltage parameter through randomization, leaving other PWM parameters that affect torque production unchanged. This selective parameter modification achieves noise reduction without negatively impacting torque production
4Loss of energy
If default PWM mode with lower switching frequencies is used, then power efficiency is maintained, but audible noise increases
Solution Approach 1:
The patent applies randomization to the zero-sequence voltage parameter in the default PWM mode, transforming the spectral characteristics of the switching noise. This allows the system to maintain efficient lower switching frequencies while reducing audible noise through spectral dispersion, eliminating the need to switch to higher frequency noise-reduction modes
Data Source
AI summary
Methods and systems are provided for adapting pulse width modulation with randomized zero-sequence components for control of an electrified powertrain of a vehicle. In one example, a method may include determining a zero-sequence voltage of an electric machine of the vehicle based on a random distribution, and adjusting a voltage reference signal of the electric machine based on the determined zero-sequence voltage to decrease ambient acoustic noise in the vehicle. In this way, spectral energy dispersion of pulse width modulated control of the electric machine may be increased without affecting torque production of the electric machine.