Dynamic Voltage Converter Limit for Regeneration Overvoltage
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Solution Overview
Problem
Existing voltage conversion systems in hybrid and electric vehicles face issues with excessive inverter voltage when the power balance of the AC motor is continuously at the regeneration side, as the control of the boost converter cannot follow the rise in inverter voltage, potentially leading to overvoltage conditions.
Innovation Solution
A voltage conversion apparatus with a control device that senses the power input and output from the DC power source, calculates the integrated value of power change over a predetermined period, and adjusts the upper limit value of the voltage converter to prevent excessive voltage by reducing it when the integrated value becomes lower than a threshold, ensuring the voltage is boosted within safe limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the boost converter continuously boosts voltage to meet power demands, then the power supply capability is improved, but the inverter voltage may exceed safe limits when the motor operates continuously in regeneration mode
Solution Approach 1:
The upper limit value of the voltage converter is made dynamic rather than fixed. The control device continuously monitors the integrated value of power change and adjusts the upper limit value accordingly - reducing it when the integrated value falls below the threshold (indicating continuous regeneration) and maintaining it at normal levels otherwise. This dynamic adjustment prevents overvoltage while preserving power supply capability under normal conditions.
Solution Approach 2:
The system implements feedback control by sensing the power input and output from the DC power source, calculating the integrated value of power change over time, and using this information to adjust the upper limit value of the voltage converter. The control device compares the integrated value against a threshold and modifies the voltage conversion ratio accordingly, creating a closed-loop control system that prevents overvoltage conditions.
2Reliability
If the upper limit value of the voltage converter is reduced to prevent overvoltage, then the safety is improved, but the power supply capability deteriorates
Solution Approach 1:
The upper limit value is dynamically adjusted based on actual operating conditions rather than being fixed at a conservative level. When the motor operates in power running mode or transient regeneration, the integrated value remains above the threshold and the upper limit value is maintained at its normal higher level, preserving power supply capability. Only when continuous regeneration is detected does the upper limit value reduce, balancing safety and performance.
Solution Approach 2:
The system changes the parameter (upper limit value) based on the operational state. By monitoring the integrated value of power change and comparing it to a threshold, the control device switches between different upper limit value settings - a higher value for normal operation to maximize power supply and a lower value for continuous regeneration to ensure safety. This parameter change approach optimizes both safety and power capability.
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 effectively prevents excessive voltage on the driving device by accurately determining the power balance of the electric motor and adjusting the voltage converter's output, thereby maintaining safe operating conditions during regeneration modes.
Implementation Method 1
a voltage converter provided between a DC power source (B) and a driving device (14) that drives at least one AC motor (M1) in one of a power running mode and a regeneration mode
Data Source
AI summary
An upper limit value setting unit of a control device conducts integration on the change in battery power, and determines whether the integrated value is lower than a preset first threshold value (negative value). When determination is made that the integrated value is lower than the first threshold value, and the battery power difference is lower than the second threshold value (negative value), the upper limit value setting unit sets Vup2 that is lower than the general Vup1 as the upper limit value of the inverter input voltage command.