EV Power Supply Voltage Control for Unintended Discharge
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Solution Overview
Problem
In electric vehicle power supply systems with two electrical storage devices, unintended discharge occurs from a high-voltage first electrical storage device to a low-voltage second device when the drive motor requests high power, leading to potential degradation and reduced performance.
Innovation Solution
A power supply system that includes a first and second power circuit with respective storage devices, a voltage converter, and a power control unit that acquires and compares voltage parameters to prevent unintended discharge by ensuring the second device's voltage remains below the first device's voltage, and actively manages discharge to limit power output from the second device when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the drive motor requests high power during acceleration, then the power output from the first electrical storage device increases, but the closed circuit voltage of the first device may become lower than the static voltage of the second device, causing unintended discharge from the second device
Solution Approach 1:
The control device performs preliminary action by actively discharging the second electrical storage device before the voltage imbalance occurs. This preventive discharge ensures that the static voltage of the second device remains below the closed circuit voltage of the first device, preventing unintended reverse discharge during high-power operation
Solution Approach 2:
The control device implements feedback control by continuously monitoring the closed circuit voltage of the first electrical storage device and the static voltage of the second electrical storage device. Based on this feedback, the control device adjusts the discharge amount of the second device to maintain proper voltage relationship and prevent unintended discharge
2Power
If the second electrical storage device is connected with higher output density, then the driving performance is improved, but the risk of unintended discharge increases when voltage parameters are not properly managed
Solution Approach 1:
The control device changes the voltage parameter of the second electrical storage device by actively controlling its discharge amount. This parameter adjustment ensures that the static voltage of the second device remains appropriately below the closed circuit voltage of the first device, preventing harmful unintended discharge while utilizing the high output density capability
Solution Approach 2:
The control device acts as an intermediary between the two electrical storage devices, mediating their voltage relationship through active discharge control of the second device. This intermediary action prevents direct harmful interaction (unintended discharge) while allowing both devices to contribute to driving performance
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 unintended discharge from the second electrical storage device, maintains driving performance, and extends travel distance by effectively utilizing the power stored in both devices.
Implementation Method 1
a voltage converter (5) which converts voltage between the first power circuit and the second power circuit
Implementation Method 2
a power converter (43) which converts power between the first power circuit and a rotary electrical machine (M)
Data Source
AI summary
A power supply system includes: a first power circuit having a first battery, a second power circuit having a second battery, a voltage converter which converts voltage between the first power circuit and the second power circuit, a power converter which converts power between the first power circuit and the drive motor, a power control unit which controls charge/discharge of the first and second batteries by operating the voltage converter and the power converter, a first voltage parameter acquisition unit which calculates an effective value for the closed circuit voltage of the first battery as a first voltage parameter, a second voltage parameter acquisition unit which calculates the static voltage of the second battery as a second voltage parameter, in which the power control unit causes power to discharge from the second battery so that the second voltage parameter becomes no more than the first voltage parameter.