Boost Converter Control for Motor Drive Overvoltage Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing boost converter systems in hybrid and electric vehicles fail to effectively manage voltage changes during transitions from slipping to gripping states, leading to potential overvoltage issues when the motor rotation speed decreases.
Innovation Solution
A control device and method for a boost converter that reduces the output voltage instruction value when the motor rotation speed decreases and its variation rate becomes significant, specifically controlling the inverter in rectangular wave or overmodulation PWM control modes, and utilizing a detection unit to adjust the voltage reduction rate based on capacitor state and rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotation speed of the motor rapidly decreases from slipping state to gripping state, then the motor comes into contact with the road surface again, but excessive electric power is supplied from the boost converter to the inverter causing overvoltage
Solution Approach 1:
The control device predicts the gripping state before it actually occurs by monitoring the rotation speed variation rate. When the absolute value of the variation rate exceeds a threshold, the control device proactively reduces the target voltage of the boost converter in advance, preventing excessive power supply to the inverter before the overvoltage condition can develop.
Solution Approach 2:
The control device continuously monitors the rotation speed of the motor and calculates its variation rate. This feedback mechanism allows the system to detect the transition from slipping to gripping state and automatically adjust the boost converter's target voltage accordingly, creating a closed-loop control system that responds to real-time conditions.
2Reliability
If the target voltage of the boost converter is lowered immediately when rotation speed decreases, then overvoltage is prevented, but the response time and control precision are compromised
Solution Approach 1:
The control device applies preliminary anti-action by reducing the target voltage before the overvoltage condition actually occurs. By monitoring the rotation speed variation rate and predicting the gripping state in advance, the system reduces the target voltage proactively, preventing the harmful overvoltage effect before it can manifest, rather than reacting after the problem occurs.
3Speed
If the boost converter supplies excessive electric power to the inverter during rapid deceleration, then the motor drive system can respond quickly to gripping state, but overvoltage occurs in the inverter
Solution Approach 1:
The control device dynamically adjusts the target voltage of the boost converter based on real-time rotation speed conditions. During rapid deceleration when the absolute value of the rotation speed variation rate exceeds a threshold, the system automatically reduces the target voltage, creating a dynamic control strategy that adapts to changing operational conditions rather than using a fixed voltage setting.
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
Prevents overvoltage in the inverter by dynamically adjusting the boost converter's output voltage in response to changes in motor rotation speed, ensuring efficient power management and preventing excessive electric power supply during state transitions.
Implementation Method 1
the DC voltage from the power supply is boosted by a boost converter
Implementation Method 2
an inverter converting an output voltage of the boost converter into an AC voltage
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A boost converter (12) boosts a DC voltage of a DC power supply (B). An inverter (14) converts the output voltage of the boost converter into an AC voltage. An AC motor (M1) is driven by the output voltage of the inverter (14). A control device (30) which controls the boost converter (12) reduces an output voltage instruction value of the boost converter (12) in the case where the rotation speed of the AC motor (M1) is decreased and an absolute value of a variation rate of the rotation speed is not less than a predetermined value. The inverter (14) is controlled in the control mode selected from a plurality of control modes including three modes of a sine wave PWM control mode, an overmodulation PWM control mode and a rectangular wave control mode. The control device (30) of the boost converter reduces the output voltage instruction value of the boost converter (12) only in the case where the control mode of the inverter (14) is the rectangular wave control mode or the overmodulation control mode.