Electric Vehicle Gear Control for LC Resonance Avoidance
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Solution Overview
Problem
Existing electric vehicle technologies face inefficiencies due to LC resonance, which increases current ripple and loss, particularly when a smoothing capacitor is connected between the direct-current power source and the inverter, limiting the usable rotation speed range of the motor.
Innovation Solution
An electric vehicle system with a controller that adjusts the gear stage of the transmission based on specific conditions, such as motor rotation speed and output, to avoid LC resonance by shifting gears when the motor's output exceeds a predetermined threshold, thereby effectively utilizing the motor and preventing resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the capacitor is connected between the direct-current power source and the inverter, then the motor can operate in a particular rotation speed range, but LC resonance occurs increasing current ripple and loss
Solution Approach 1:
The patent applies dynamics by making the gear stage adjustable rather than fixed. The controller dynamically changes the gear stage based on real-time motor rotation speed and output conditions. When the motor rotation speed enters a predetermined range where LC resonance would occur and the motor output exceeds a threshold, the controller automatically shifts to a different gear stage to move the motor operation out of the resonance zone, thereby eliminating energy loss while maintaining adaptability across the rotation speed range.
2Loss of energy
If the gear stage is adjusted to avoid LC resonance, then power loss is reduced, but the motor cannot use certain rotation speed ranges
Solution Approach 1:
The system dynamically adjusts the gear stage based on motor operating conditions. When LC resonance is detected (motor rotation speed in predetermined range and output above threshold), the controller shifts gear stages to avoid resonance. However, when motor output is below the threshold, the controller allows operation in the resonance-prone rotation speed range, thereby maintaining full adaptability. This dynamic approach ensures that the motor can use the entire rotation speed range while minimizing power loss through selective gear shifting only when necessary.
3Object-generated harmful factors
If gearshift is performed to avoid LC resonance, then current ripple is reduced, but system complexity increases
Solution Approach 1:
The controller implements feedback by continuously monitoring motor rotation speed and output, comparing these values against predetermined thresholds for the LC resonance zone, and automatically adjusting the gear stage accordingly. This closed-loop control reduces current ripple by preventing operation in resonance conditions while maintaining simple control logic through threshold-based decision making, avoiding the need for complex resonance detection algorithms.
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
This approach allows for the effective use of the motor across a broader range of rotation speeds by avoiding LC resonance, reducing power loss and improving efficiency by dynamically adjusting the gear stage in response to motor output conditions.
Implementation Method 1
an inverter configured to convert direct-current power output by the battery, into alternating-current power for driving the motor
Implementation Method 2
a capacitor connected between a positive electrode of direct-current input terminals of the inverter and a negative electrode of the direct-current input terminals of the inverter
Implementation Method 3
LC resonance easily occurs when the rotation speed of the motor is in a particular range... The LC resonance increases current ripple, and increases loss
Data Source
AI summary
An electric vehicle includes: a motor for traveling; a transmission connected to the motor; a battery; an inverter configured to convert direct-current power output by the battery, into alternating-current power for driving the motor; a capacitor connected between a positive electrode of direct-current input terminals of the inverter and a negative electrode of the direct-current input terminals of the inverter; and a controller configured to change a gear stage of the transmission when both of a condition i) and a condition ii) are satisfied. The condition i) is a condition that the rotation speed of the motor is in a predetermined range. The condition ii) is a condition that the output of the motor exceeds a predetermined output threshold.