Motor Drive Inverter PWM Switching for Higher Linear Modulation
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Solution Overview
Problem
Existing drive devices for motor vehicles with electric machines and inverters controlled by pulse width modulation face limitations in drive power due to a restricted linear control range, which is proportional to the locking time of the inverter switches, limiting the drive power provided by the electric machine.
Innovation Solution
The method involves using continuous pulse width modulation at duty cycles below a threshold value and switching to discontinuous pulse width modulation when the threshold is exceeded, increasing the linear modulation range of the inverter by up to half the locking time, allowing for higher drive power by selecting the appropriate type of pulse width modulation based on the duty cycle, such as space vector modulation, and implementing clamping over specific rotation angles to enhance effective voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If continuous pulse width modulation is used to control the inverter, then the electric machine operates efficiently at low duty cycles, but the linear modulation range is limited by the locking time, restricting drive power
Solution Approach 1:
The patent applies dynamics by switching between two different pulse width modulation modes (continuous and discontinuous) based on the duty cycle threshold. This dynamic adaptation allows the system to optimize performance across different operating conditions, expanding the linear modulation range beyond the limitations of a single fixed modulation mode while managing control complexity through condition-based switching.
2Adaptability or versatility
If the duty cycle exceeds the threshold value, then the linear modulation range increases with discontinuous pulse width modulation, but switching between modulation types adds control complexity
Solution Approach 1:
The patent changes the modulation parameter (switching between continuous and discontinuous modes) based on the duty cycle parameter. When the duty cycle exceeds a predetermined threshold, the system transitions from continuous to discontinuous pulse width modulation, thereby adapting the linear modulation range to match the operating conditions and expand the effective control range.
3Power
If the locking time of inverter switches is reduced to increase linear control range, then drive power increases, but the dead time requirements for switch protection become more critical
Solution Approach 1:
The patent uses periodic action through discontinuous pulse width modulation, where switching occurs at specific intervals rather than continuously. This periodic switching pattern allows for adequate dead time between switching events, maintaining switch protection reliability while still achieving an expanded linear modulation range and increased drive power capability.
Data Source
AI summary
A method for operating a drive device for a motor vehicle is provided, wherein the drive device has an electric machine which is electrically connected to a DC power source via an inverter controlled by means of pulse width modulation. The pulse width modulation is performed depending on a predetermined duty cycle. When the duty cycle that is less than a threshold value, a continuous pulse width modulation is used to control the inverter. The pulse width modulation is switched to a discontinuous pulse width modulation when the threshold value is exceeded. A motor vehicle and a drive device for a motor vehicle are also provided.