Hybrid Load Drive Overvoltage Prevention
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Solution Overview
Problem
Existing load driving apparatuses in hybrid vehicles fail to prevent overvoltage at the inverter input side when excessive rotation of the electric load occurs, leading to potential damage and instability in the power supply system.
Innovation Solution
A load driving apparatus with a control system that reduces the torque of the rotating electric machine and adjusts the boosting rate of the up-conversion device when excessive rotation is detected, ensuring the voltage level of the power supply line remains within safe limits to prevent overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque of the rotating electric machine is rapidly reduced to prevent excessive rotation damage, then the motor protection is improved, but overvoltage occurs at the inverter input side due to sudden power consumption decrease
Solution Approach 1:
The control device reduces the boosting rate of the up-conversion device in advance when the revolution count exceeds a predetermined sub-limit value (before excessive rotation occurs). This preliminary action prevents the sudden power supply-demand imbalance that would otherwise cause overvoltage when torque is rapidly reduced to protect the motor from excessive rotation damage.
Solution Approach 2:
The control device applies a counter-action by reducing the boosting rate before the harmful effect (overvoltage) can occur. When excessive rotation is detected or anticipated, the up-conversion device's boosting rate is reduced in advance to offset the upcoming power consumption decrease, thereby preventing overvoltage at the inverter input side.
2Power
If the boosting rate of the up-conversion device is maintained at high level, then the power supply voltage is sufficient for motor operation, but overvoltage occurs when motor torque is rapidly reduced
Solution Approach 1:
The boosting rate of the up-conversion device is made dynamic rather than fixed. The control device adjusts the boosting rate based on the revolution count of the rotating electric machine, reducing it when the revolution count exceeds a predetermined sub-limit value. This dynamic adjustment allows the system to maintain sufficient power supply voltage during normal operation while preventing overvoltage when motor torque is rapidly reduced.
Solution Approach 2:
The control device changes the operating parameter (boosting rate) of the up-conversion device based on the revolution count. When the revolution count exceeds a predetermined sub-limit value, the boosting rate is reduced from its normal high level to a lower level, thereby preventing overvoltage while still maintaining adequate power supply for motor operation.
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
Effectively prevents overvoltage at the inverter input, protecting the electric load and maintaining a stable power supply by reducing the torque and adjusting the boosting rate in response to excessive rotation, thereby enhancing the reliability of the vehicle's power system.
Implementation Method 1
an up-conversion device (10) arranged between a second power supply line (PL1) connected to a DC power source (B) and the first power supply line (PL2) to boost the voltage of the second power supply line (PL1) for output to the first power supply line (PL2)
Data Source
AI summary
When an ECU determines that the motor count of a motor generator exceeds a predetermined limit value, control is effected to set the torque of motor generator to zero. Further, when the ECU determines that motor count exceeds the predetermined limit value, voltage control of inverter input voltage is reduced by a predetermined level.