Converter Voltage Control for Torque Accuracy
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Solution Overview
Problem
In hybrid and electric vehicles, the output voltage of the step-up converter in fuel efficiency mode is insufficient for moments requiring high torque, leading to torque control issues when increasing system voltage during rectangular wave voltage control, as the voltage change is not accurately reflected in the switching period, resulting in mismatched torque command and actual output torque.
Innovation Solution
A control device with a first unit controlling the converter's output voltage based on a voltage command, a second unit controlling the inverter to supply rectangular wave voltage based on a torque command, and a third unit adjusting both voltage and torque command values to ensure the difference between the torque command and actual output torque is minimized, with specific increase rates and timing for optimal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the output voltage of the step-up converter is restricted to a smaller value in fuel efficiency mode, then fuel efficiency is improved, but torque becomes insufficient when large torque is required
Solution Approach 1:
The patent applies dynamics by making the converter output voltage variable rather than fixed. The voltage is dynamically adjusted based on the relationship between converter output voltage and inverter switching frequency. When inverter switching frequency increases, the converter output voltage is increased proportionally to maintain torque control accuracy, while still allowing voltage reduction for fuel efficiency optimization when high torque is not required.
Solution Approach 2:
The patent changes the parameter of converter output voltage based on operating conditions. By adjusting the voltage command value according to the inverter switching frequency and the relationship between converter output voltage and switching frequency, the system optimizes both fuel efficiency and torque performance across different operating ranges.
2Force
If the system voltage is increased during rectangular wave voltage control to counteract insufficient torque, then torque availability is improved, but torque control accuracy deteriorates because the voltage change is not accurately reflected in the switching period
Solution Approach 1:
The patent implements feedback control by continuously monitoring the relationship between converter output voltage and inverter switching frequency. The voltage command value is adjusted based on feedback from the actual operating conditions, ensuring that torque control accuracy is maintained even when system voltage changes. This feedback mechanism prevents the mismatch between commanded and actual torque that occurs in conventional rectangular wave control.
Solution Approach 2:
The system dynamically adjusts the converter output voltage in response to changing inverter switching frequency. This dynamic adjustment ensures that the voltage command is always appropriate for the current operating point, maintaining torque control accuracy while allowing flexible voltage changes to meet torque requirements.
3Loss of energy
If the converter output voltage is fixed at a lower value for fuel efficiency, then energy loss is reduced, but the system cannot respond to moments requiring high torque
Solution Approach 1:
The patent makes the converter output voltage dynamic rather than fixed. The voltage command value is continuously adjusted based on the inverter switching frequency and the relationship between converter output voltage and switching frequency. This allows the system to operate at lower voltages for fuel efficiency while automatically increasing voltage when high torque is required, providing both energy efficiency and adaptability.
Solution Approach 2:
The system changes the converter output voltage parameter based on operating conditions. By adjusting the voltage command value according to the relationship between converter output voltage and inverter switching frequency, the system optimizes converter loss while maintaining the ability to respond to varying torque demands.
Data Source
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AI summary
A vehicle includes a converter (12) for stepping up power provided from a power storage device, and an inverter (14) for converting the power output from converter (12) and outputting it to an alternating-current motor (M1) for driving the vehicle. In the vehicle, a rectangular voltage control unit (3300) controls the inverter (14) by means of rectangular wave voltage control that is based on a torque command value (Trqcom) and the like, so as to control an output torque of the alternating-current motor (M1). A system voltage control unit (3400) controls a system voltage (VH), which is an output voltage of the converter (12). The system voltage control unit (3400) lifts a restriction on a system voltage command value (VHcom) based on an accelerator pedal position and the like, and then increases it. When increasing the system voltage command value (VHcom) during the rectangular wave voltage control for the inverter (14), a cooperative control unit (3500) increases the system voltage command value (VHcom) and the torque command value (Trqcom) in a cooperative manner.