Inverter Control Threshold Switching for xEV Motor Efficiency
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Solution Overview
Problem
Existing inverter control systems in xEV automobiles have fixed threshold values for switching between sine wave and rectangular wave control, which do not account for varying system conditions such as bus voltage, carrier frequency, and temperature, leading to reduced efficiency and increased switching loss.
Innovation Solution
A method for dynamically adjusting the threshold values for switching between overmodulation and rectangular wave control based on system efficiency, using torque maps and real-time loss modeling to optimize inverter operation across different speed and torque ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed threshold values are used for switching between control methods, then the control system is simple to implement, but system efficiency decreases under varying operating conditions
Solution Approach 1:
The patent applies dynamics by transitioning from fixed threshold values to dynamically adjustable thresholds that adapt to changing operating conditions. The control device calculates optimal threshold values based on real-time parameters such as bus voltage, carrier frequency, and temperature, allowing the switching points between sine wave PWM, overmodulation PWM, and rectangular wave control to move adaptively. This resolves the contradiction by making the control system complex enough to adapt dynamically while maintaining simplicity in the underlying control architecture.
Solution Approach 2:
The patent changes the parameter of threshold values from static to dynamic by calculating optimal switching thresholds based on operating conditions. The control device computes threshold values that optimize system efficiency under varying bus voltage, carrier frequency, and temperature conditions. This parameter change allows the system to maintain high efficiency across different operating points without requiring a completely complex adaptive control architecture.
2Loss of energy
If dynamic threshold adjustment is implemented, then system efficiency improves under varying conditions, but device complexity increases
Solution Approach 1:
The control device implements dynamic threshold adjustment by calculating optimal switching thresholds based on real-time operating conditions including bus voltage, carrier frequency, and temperature. This dynamic calculation allows the system to adapt to changing conditions and maintain high efficiency without requiring overly complex control architecture, as the computation is integrated into the existing control framework.
Solution Approach 2:
The patent changes the threshold parameters from fixed to dynamic values that are recalculated based on operating conditions. The control device computes optimal threshold values that maximize system efficiency under varying bus voltage, carrier frequency, and temperature. This parameter adaptation improves efficiency while keeping the control system complexity manageable through efficient calculation methods.
3Ease of operation
If sine wave control method is used in low-speed range, then output responsiveness and controllability are improved, but output power is reduced
Solution Approach 1:
The patent segments the speed range into distinct regions (low-speed, medium-speed, high-speed) and assigns different control methods to each segment. The control device determines the appropriate control method based on the current operating point, switching between sine wave PWM control for low-speed operation and rectangular wave control for high-speed operation. This segmentation allows the system to optimize both controllability and output power by using the most appropriate control method for each speed range.
Solution Approach 2:
The control device dynamically selects the control method based on real-time speed and torque conditions. Rather than using a fixed control method, the system transitions between sine wave PWM, overmodulation PWM, and rectangular wave control as operating conditions change. This dynamic selection ensures optimal motor controllability at low speeds while maximizing output power at high speeds.
4Power
If rectangular wave control method is used in high-speed range, then output power is increased and switching loss is reduced, but output responsiveness and controllability deteriorate
Solution Approach 1:
The patent segments the operating range and assigns rectangular wave control specifically to the high-speed, high-torque range where its advantages in output power and switching loss reduction are most beneficial. The control device determines when to apply rectangular wave control based on real-time operating conditions, ensuring it is used primarily when high power output is required rather than during low-speed operations where controllability is more critical.
Solution Approach 2:
The control device dynamically adjusts the control method based on real-time speed and torque conditions. The system transitions to rectangular wave control in the high-speed range where output power and switching efficiency are prioritized, while maintaining sine wave or overmodulation control in lower speed ranges where controllability and responsiveness are more important. This dynamic adaptation resolves the contradiction by optimizing for the appropriate performance metric at each operating point.
Data Source
AI summary
In inverter control of a motor, an inverter control method is provided that increases system efficiency in all speed ranges from low speed to high speed based on system efficiency. Specifically, the inverter control method of switching between overmodulation control and rectangular wave control, especially in the medium to high-speed range is provided, with taking system efficiency into consideration.