Voltage-Up Converter Damping Control for Hybrid Vehicle Efficiency
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Solution Overview
Problem
The frequent variation in torque command for damping control in motor drive devices leads to increased current flow through voltage-up converters, causing power loss and potentially damaging the switching elements, which degrades the efficiency and reliability of motor drive systems in hybrid and electric vehicles.
Innovation Solution
A motor drive device with a damping control unit that sets a predetermined upper limit for damping torque independent of motor revolution variations, ensuring stable voltage conversion and reducing current flow through the voltage converter by smoothing the voltage command, and includes a charge storage unit to stabilize the voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If damping control is executed by adding damping torque based on motor revolution waviness to the torque command, then vehicle vibration is suppressed, but the torque command varies frequently causing the voltage-up converter to repeat voltage-up and voltage-down operations
Solution Approach 1:
The patent segments the torque command into two independent parts: the primary torque command for motor drive and the damping torque for vibration suppression. By processing these separately and only applying damping torque to the inverter control (not the voltage-up converter control), the system eliminates the coupling that causes frequent voltage conversion operations while maintaining vibration suppression effectiveness.
Solution Approach 2:
The patent extracts the damping torque component from the torque command used for voltage-up converter control. The damping torque is calculated from motor revolution waviness and added only to the inverter's torque command, while the voltage-up converter receives only the primary torque command. This extraction prevents the damping control variations from affecting the voltage conversion process.
2Reliability
If the voltage command of the voltage-up converter is determined based on the torque command with damping torque, then damping control is achieved, but the voltage command varies frequently causing excessive current flow through the voltage-up converter
Solution Approach 1:
The patent segments the control system into two independent control paths: one for voltage-up converter control that uses only the primary torque command, and another for inverter control that uses the primary torque command plus damping torque. This segmentation ensures that damping control variations do not propagate to the voltage-up converter, preventing excessive current flow while maintaining damping control effectiveness through the inverter.
Solution Approach 2:
The patent extracts the damping torque from the voltage command determination process. The voltage command is calculated based solely on the primary torque command without the damping torque component. The damping torque is retained only in the inverter's torque command, effectively removing the source of frequent voltage command variations that cause excessive current flow.
3Reliability
If damping torque is continuously adjusted based on motor revolution waviness, then torque pulsation is canceled, but the voltage-up converter experiences frequent switching between voltage-up and voltage-down operations
Solution Approach 1:
The patent segments the control architecture so that damping torque calculation and application are isolated to the inverter control path only. The voltage-up converter control path receives a stable primary torque command without damping torque variations. This segmentation allows torque pulsation cancellation to be achieved through the inverter while the voltage-up converter operates efficiently without frequent switching.
Solution Approach 2:
The patent extracts the damping torque component from the voltage-up converter's control input. By calculating damping torque from motor revolution waviness and applying it only to the inverter's torque command (not the voltage-up converter's voltage command), the system removes the cause of frequent voltage conversion operations while preserving torque pulsation cancellation benefits through the inverter's controlled torque output.
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 solution reduces power loss and protects the voltage converter by maintaining stable damping control, improving motor drive efficiency and preventing damage from excessive current flow, while ensuring consistent torque output.
Implementation Method 1
a voltage-up converter 12, the DC voltage from the power source B being increased to a motor drive voltage
Implementation Method 2
an inverter 14, the DC voltage being converted into AC voltage by the inverter 14 to be used for motor drive control
Implementation Method 3
a smoothing capacitor must be provided at the output side of the voltage-up converter to stabilize the motor drive voltage
Implementation Method 4
a motor driven by the inverter as the power source... the converted AC voltage is used to rotate the motor to achieve power
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A torque command (Tht) used in the calculation of a voltage command (Vht) of a voltage-up converter is generated by adding an upper limit value value (Tc_max) of damping control that can be set by a motor drive device with a target drive torque (Tbt). Accordingly, the torque command (Tht) exhibits a waveform absent of variation, differing from a torque command (Tcmd) that is generated by adding damping torque generated based on revolution count variation component with the target drive torque (Tbt). Therefore, the voltage command (Vht) calculated based on the torque command (Tht) exhibits a waveform absent of variation. Accordingly, increase in current passing through the voltage-up converter caused by variation in the voltage command (Vht) can be suppressed. As a result, power loss at the voltage-up converter is reduced and operation of the motor at high efficiency can be realized. Further, the voltage-up converter can be protected from element fracture.