EV Drivetrain Charging Control Using Rotor-Based Phase Selection
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Solution Overview
Problem
Current DC-DC conversion in electric vehicle drivetrains during charging results in current ripple, leading to high-frequency losses and heat generation, which are mitigated using capacitors but can be further reduced.
Innovation Solution
The method involves controlling the traction inverter unit to select specific phases of the electric machine based on the rotor position to maximize inductance, thereby reducing current ripple and losses, and using look-up tables to determine optimal phase combinations for efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If DC-DC conversion is performed using the traction inverter and electric machine during charging, then the on-board charger can be omitted reducing weight and costs, but current ripple is generated causing high-frequency losses and heat generation
Solution Approach 1:
The patent changes the operating parameters of the DC-DC conversion by dynamically adjusting the switching frequency and pulse width modulation (PWM) duty cycle based on the rotor position. By optimizing these parameters in real-time, the system reduces current ripple and high-frequency losses while maintaining the weight reduction benefit of omitting the on-board charger
Solution Approach 2:
The system dynamically adapts the DC-DC conversion process by continuously monitoring rotor position and adjusting control parameters accordingly. This dynamic approach allows the system to minimize energy losses during different operating conditions while maintaining the simplified drivetrain architecture without a dedicated on-board charger
2Ease of manufacture
If DC-DC conversion is performed using the traction inverter and electric machine during charging, then the on-board charger can be omitted reducing costs, but current ripple produces losses leading to heat generation
Solution Approach 1:
The patent optimizes control parameters including switching frequency and PWM duty cycle as functions of rotor position to minimize current ripple. By changing these parameters dynamically, the system reduces I²R losses and heat generation while maintaining the cost-effective drivetrain design without an on-board charger
3Loss of energy
If capacitors are used to mitigate current ripple, then high-frequency losses are reduced, but the drivetrain size and cost increase
Solution Approach 1:
The patent replaces the passive mechanical/electrical filtering approach (using large capacitors) with an active control approach. By using dynamic PWM control and switching frequency adjustment based on rotor position, the system achieves current ripple mitigation without requiring additional bulky filtering components, thus reducing drivetrain volume
Solution Approach 2:
The system uses the existing electric machine and inverter components to actively compensate for and mitigate current ripple through intelligent control. The controller utilizes information about rotor position to self-regulate the DC-DC conversion process, eliminating the need for external filtering components and reducing overall system size
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 reduces high-frequency losses, extends component lifetime, and allows for a smaller filter capacitor, resulting in a more compact and cost-effective drivetrain.
Implementation Method 1
the traction inverter together with the N-phase electric machine may be used as a DC-DC converter. Essentially, the power switches of the N-phase traction inverter are used together with the magnetic coils of the N-phase electric machine to perform the DC-DC conversion.
Data Source
AI summary
A method for controlling a drivetrain of an electric vehicle during DC-charging of a traction battery. A corresponding charging circuit includes at least partially a traction inverter unit and at least partially an electric machine. The method includes controlling the traction inverter unit such that it operates as a DC-DC converter. Furthermore, a position of a rotor of the electric machine is received and based thereon, a number out of the phases of the electric machine is selected as components of the charging circuit. Additionally, the traction inverter unit is controlled such that the selected number of the phases forms part of the charging circuit. Moreover, a data processing device having means for carrying out the steps of the above method is presented. Additionally, a drivetrain and an electric vehicle are explained.