EV Power-On Precharge Control for High-Voltage Bus Safety
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Solution Overview
Problem
Existing power-on and power-off processes in electric vehicles are inefficient, slow, and pose safety risks due to energy management challenges and potential battery over-discharge or electrical fires.
Innovation Solution
An electrical system for electric vehicles that includes a main controller, low-voltage battery pack, high-voltage bus, DC-DC converter, precharging capacitor, and local controller, which manages the connection and disconnection of high-voltage battery electrodes to the bus, and performs insulation detection during power-off, using capacitor precharging for efficient voltage stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional power-on process is used with sequential relay closing, then safety is maintained through step-by-step voltage buildup, but the process is slow and inefficient
Solution Approach 1:
The precharging capacitor is charged to a target voltage before the main positive relay is closed. This preliminary action prepares the electrical system in advance, allowing the main relay to close without causing large impulse currents, thus both speeding up the process and maintaining safety.
Solution Approach 2:
The precharging capacitor acts as an intermediary element between the low-voltage battery pack and the high-voltage bus. It mediates the voltage transition by absorbing charge gradually and releasing it smoothly when the main relay closes, eliminating the need for slow sequential relay operations.
2Reliability
If traditional power-off process is used with simple disconnection, then operation is simple, but safety risks such as battery over-discharge and electrical fires occur
Solution Approach 1:
The main controller monitors the voltage of the precharging capacitor and the state of the high-voltage battery pack in real-time. Based on this feedback, it dynamically adjusts the control signals to the relays and DC-DC converter, ensuring safe disconnection and preventing over-discharge or electrical hazards.
Solution Approach 2:
The power-off process maintains continuous monitoring and controlled discharge through the precharging capacitor. Instead of simple disconnection, the system continuously manages the energy dissipation to ensure safety while the vehicle is shutting down, preventing hazardous conditions.
3Use of energy by moving object
If DC-DC converter is used for precharging, then voltage conversion efficiency is improved, but energy loss during conversion increases
Solution Approach 1:
The DC-DC converter operates only partially during the precharging process, charging the precharging capacitor to a target voltage rather than fully converting all available energy. This partial action reduces conversion losses while still achieving the necessary precharge voltage for safe 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
Enhances the efficiency and safety of power-on and power-off processes by stabilizing voltage quickly and reducing the risk of large impulse currents and electrical hazards.
Implementation Method 1
a precharging capacitor connected between the high-voltage bus and the negative bus
Implementation Method 2
enabling the low-voltage battery pack to charge the precharging capacitor to a target precharging voltage through the DC-DC converter
Data Source
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AI summary
The disclosure relates to the field of vehicle control technologies, and in particular to an electrical system of an electric vehicle, and methods for controlling a power-on process and a power-off process of an electric vehicle. According to an aspect of the disclosure, an electrical system of an electric vehicle is provided. The system includes: a main controller; a low-voltage battery pack; a high-voltage bus and a negative bus; a high-voltage unit including a high-voltage battery pack connected to the high-voltage bus and to the negative bus; a DC-DC converter connected between the high-voltage bus and the negative bus; and a precharging capacitor connected between the high-voltage bus and the negative bus, wherein the main controller is configured to perform the following operations: A. enabling the low-voltage battery pack to charge the precharging capacitor to a target precharging voltage through the DC-DC converter in response to a power-on event; and B. sending to the high-voltage unit a first command to connect a positive electrode of the high-voltage battery pack to the high-voltage bus after it is determined that a bus voltage reaches the target precharging voltage.