Vehicle Drive Control System Managing Boosting Transients
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Solution Overview
Problem
In rotating electrical machine control systems, the rapid increase in boosted voltage during the transition from non-boosting to boosting states leads to response delays and excessive current draw from the battery, causing overcurrent issues due to the transient voltage increase, which existing techniques fail to adequately address.
Innovation Solution
A control system that includes a frequency converting portion and a voltage converting portion, where the shift boundary is set based on the boostable electric power obtained by subtracting increased electric power from the allowable electric power, ensuring that power consumption does not exceed the boostable electric power, thereby preventing overcurrents during the transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the boosting operation is started from a non-boosting state with PWM switching control, then the boosted voltage follows the required voltage in a desirable manner, but a dead time produces a region where the boosting operation cannot be performed in a predetermined voltage range from the battery voltage, causing the boosted voltage to rapidly increase when the boosting operation is started
Solution Approach 1:
The control device determines in advance whether to start the boosting operation by comparing the square wave duty ratio that should be applied during the dead time with a predetermined threshold value. This preliminary determination prevents the harmful rapid voltage increase by anticipating the problem before it occurs, allowing the system to either skip the boosting operation or adjust parameters to avoid the dangerous voltage spike.
2Speed
If the boosted voltage rapidly increases when the boosting operation is started, then the voltage reaches the target value quickly, but a response delay is generated due to transmission time and computation time, causing the rotating electrical machine to output higher torque than target torque and drawing excessive current from the battery
Solution Approach 1:
The control device performs preliminary determination of whether to start the boosting operation by comparing the square wave duty ratio during dead time with a threshold value. This advance decision-making prevents the sequence of rapid voltage increase followed by delayed response and excessive current draw, thereby resolving the energy consumption issue.
Solution Approach 2:
The control device monitors the square wave duty ratio and uses it as feedback to determine whether to initiate the boosting operation. By continuously comparing the duty ratio with the threshold value, the system adjusts its behavior to prevent conditions that would lead to excessive current consumption from the battery.
3Productivity
If the shift boundary is set based on target torque and rotational speed, then the boosting operation can be performed in the appropriate region, but the increased electric power transiently produced during shifting from non-boost control to boost control may cause power consumption to exceed allowable electric power
Solution Approach 1:
The control device determines in advance whether to start the boosting operation by comparing the square wave duty ratio during dead time with a predetermined threshold value. This preliminary action prevents the transient power loss by avoiding the transition that would cause excessive power consumption to exceed allowable limits.
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 approach effectively suppresses overcurrents by setting the shift boundary to manage power consumption within the allowable limits, even during maximum target torque conditions, reducing unnecessary boosting and associated losses.
Implementation Method 1
a voltage converting portion (4) interposed between the DC power source (B) and the frequency converting portion (5), and boosting the output of the DC power source (B)
Implementation Method 2
a frequency converting portion (5) interposed between the rotating electrical machine (MG2) and the DC power source (B), and converting the output of the DC power source (B) to an AC output
Data Source
AI summary
A rotating electrical machine control system includes a frequency converting portion that is interposed between a rotating electrical machine for driving a vehicle and a DC power source for supplying electric power to the rotating electrical machine, and that converts an output of the DC power source to an AC output at least during a powering operation of the rotating electrical machine; a voltage converting portion that is interposed between the DC power source and the frequency converting portion, and that boosts the output of the DC power source based on a boost command value which is set according to a target torque and a rotational speed of the rotating electrical machine; and a control portion for controlling the frequency converting portion and the voltage converting portion.