High-Voltage Battery Precharge Feedback for Arc-Free Relay Connection
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Solution Overview
Problem
In electric or hybrid vehicles, connecting a high-voltage battery to a high-voltage network using relays risks forming an electric arc due to voltage differences, leading to relay degradation, despite conventional precharging methods which can be inaccurate and fail to prevent arc formation.
Innovation Solution
A method that precharges the high-voltage network to match the battery voltage, measures the voltage difference when connected, and adjusts the precharging setpoint based on this measurement to ensure zero current and prevent arc formation, using voltage sensors and potentially temperature mapping for accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional precharging methods are used to bring the high-voltage network to the same voltage level as the battery, then the inrush current is reduced and electric arc formation is minimized, but sensor inaccuracies due to production tolerances, aging, and temperature exposure cause voltage differences to persist, leading to relay degradation
Solution Approach 1:
The patent implements a feedback mechanism where the actual voltage difference between the battery and high-voltage network is measured during connection, and this measurement is used to update a correction value stored in memory. This correction value is then applied in subsequent precharging operations to compensate for sensor drift and inaccuracies, ensuring consistently accurate voltage matching and preventing electric arc formation that would degrade the relay.
2Reliability
If the voltage difference between the battery and high-voltage network is large, then the inrush current and electric arc intensity increase causing relay wear, but adding complex precharging circuits with resistors and additional relays increases device complexity
Solution Approach 1:
The system uses its own existing voltage sensors and control unit to perform the precharging correction function. The control unit measures the voltage difference during connection, calculates the correction value, stores it in memory, and automatically applies it in subsequent operations. This self-correcting mechanism eliminates the need for additional precharging circuits, resistors, or relays, maintaining system simplicity while ensuring reliable relay operation.
3Extent of automation
If voltage sensors are used to monitor battery and network voltage levels, then precharging control is enabled, but sensor inaccuracies due to temperature, aging, and production tolerances lead to incorrect voltage matching and electric arc formation
Solution Approach 1:
The patent dynamically adjusts the precharging voltage setpoint by applying a correction value to the nominal battery voltage. This corrected setpoint is used to control the DC/DC boost converter during precharging, ensuring that the high-voltage network is charged to the precise voltage level needed to match the battery, compensating for sensor inaccuracies and preventing electric arc formation.
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 method effectively prevents electric arc formation during relay switching, enhancing relay durability by correcting for sensor inaccuracies and ensuring reliable connections between the high-voltage battery and network.
Implementation Method 1
An electromechanical relay is an electrical component that is actuated by an electromagnet and that plays the role of a switch to distribute power when a command is issued by a control
Implementation Method 2
An electric arc may be created through ionization of the insulating medium, which is generally air. Once ionized, the gas creates a conductive channel that extracts the rest of the charge present on the starting surface
Implementation Method 3
voltage sensors associated with the high-voltage battery and with the high-voltage network
Implementation Method 4
The DC/DC boost converter uses the energy of the low-voltage battery to raise the voltage of the high-voltage network, and in particular of its capacitors, to the voltage setpoint received by the master electronic control unit
Data Source
AI summary
A method is for connecting a high-voltage battery to a high-voltage network using at least one relay in a powertrain of an electric or hybrid vehicle. The method includes precharging the high-voltage network according to a preset precharging setpoint; achieving connection between the high-voltage battery and the high-voltage network by closing the relay; measuring the difference between the voltage of the high-voltage battery and the voltage of the high-voltage network when the high-voltage battery and the high-voltage network are connected and the current of the high-voltage battery is zero; and establishing a corrected precharging setpoint depending on the measured difference between the high-voltage battery and the high-voltage network for a subsequent connection.