EV Inverter PWM Deadtime Control to Eliminate Small Pulses
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Solution Overview
Problem
Inverters for electric vehicles face degradation due to nonzero turn-on and turn-off times of power semiconductor devices, which can be exacerbated by switching losses, voltage and current ripples, elevated temperatures, and high switching frequencies, leading to potential failure from small pulses that violate minimum pulse width requirements.
Innovation Solution
A system and method that adjusts deadtime configurations to prevent the generation of small pulses by reconfiguring existing deadtime settings, allowing feedback of actual pulse widths to upper software layers while maintaining a full duty cycle range of PWM signals, and leveraging existing deadtime hardware for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deadtime configuration is used to protect switches, then switch degradation is reduced, but small pulses may be generated that damage the switches
Solution Approach 1:
The controller predicts whether a small pulse will be generated based on the commanded PWM signal and current deadtime configuration before actually generating the PWM signal. This preliminary prediction allows the system to adjust the deadtime configuration in advance to prevent small pulse generation, thereby protecting the switches without causing harmful pulses.
Solution Approach 2:
The deadtime configuration is made dynamic rather than fixed. The controller adjusts the deadtime configuration based on real-time conditions and the predicted PWM signal characteristics. This dynamic adjustment allows the system to optimize protection while preventing small pulse generation across different operating conditions.
2Reliability
If minimum pulse width is enforced, then small pulses are prevented, but duty cycle range is limited
Solution Approach 1:
The system uses dynamic deadtime configuration that adapts to different PWM signal requirements. By adjusting the deadtime configuration based on predicted signal characteristics, the system maintains full duty cycle range while preventing small pulses. The dynamic nature allows different deadtime values for different parts of the PWM cycle, enabling both small pulse prevention and full adaptability.
3Device complexity
If existing deadtime hardware is used, then device complexity is reduced, but small pulse detection and prevention capability is limited
Solution Approach 1:
The system implements a feedback mechanism where the controller predicts the outcome of PWM signal generation based on current deadtime configuration and commanded signals. This feedback loop allows the controller to detect potential small pulse conditions and adjust the deadtime configuration accordingly, enhancing the basic deadtime hardware's capability without adding complex external detection circuits.
Data Source
AI summary
A system includes: an inverter including a first switch and a second switch; one or more controllers configured to control the inverter by performing operations, the operations including: generating a minimum pulse width value for a first pulse-width modulated (PWM) signal to control the first switch and for a second PWM signal to control the second switch; determining that an on-time pulse to be generated for the first PWM signal will be less than or equal to the minimum pulse width value for a period based on a first deadtime configuration; and in response to the determining: determining a second deadtime configuration for the first PWM signal and the second PWM signal for the period; and generating the first PWM signal and the second PWM signal based on the second deadtime configuration, to prevent the on-time pulse that is less than or equal to the minimum pulse width value.