EV Charging Relay Voltage Matching to Prevent Inrush Fusing
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Solution Overview
Problem
In electrified vehicles, the charging relay is prone to fusing when turned on, especially when using high-rated voltage power storage devices, due to inrush current, which existing technologies fail to adequately suppress.
Innovation Solution
Incorporating a buck-boost converter between the charging relay and the power storage device, controlled by a control device that adjusts the voltage on the converter side of the second power line based on the connector side voltage, using feedforward and feedback control to minimize the voltage difference and prevent fusing when the relay is activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a buck-boost converter is added to enable high-rated voltage power storage devices, then charging power and voltage are improved, but the complexity of the system increases and the charging relay becomes more prone to fusing due to inrush current
Solution Approach 1:
The control device performs preliminary voltage adjustment by controlling the buck-boost converter before the charging relay is turned on. This preliminary action equalizes the voltage between the connector-side portion and converter-side portion of the power line, preventing inrush current when the relay closes, thereby suppressing relay fusing while enabling high-rated voltage charging
2Productivity
If the charging relay is turned on with high voltage difference, then charging speed is improved, but the relay fuses due to inrush current
Solution Approach 1:
Before turning on the charging relay, the control device activates the buck-boost converter to adjust the converter-side voltage to match the connector-side voltage. This preliminary voltage equalization eliminates the voltage difference that would cause inrush current, allowing the relay to be turned on safely while maintaining high charging power capability
Solution Approach 2:
The control device dynamically changes the voltage parameter on the converter-side portion of the power line by controlling the buck-boost converter. This parameter adjustment equalizes the voltage between both portions of the power line before relay activation, preventing inrush current while enabling subsequent high-power charging
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
The solution effectively suppresses fusing of the charging relay during activation, allows for increased charging power by raising the voltage after relay turn-on, and reduces costs by avoiding the need for higher withstand voltage, thereby shortening charging time while maintaining safety.
Implementation Method 1
a buck-boost converter that exchanges electric power, accompanied by voltage conversion, with a first power line to which the power storage device is connected and a second power line to which the connector is connected
Data Source
AI summary
The electrified vehicle includes a power storage device, a connector, a buck-boost converter that exchanges power with voltage conversion between a first power line to which the power storage device is connected and a second power line to which the connector is connected; A charging relay provided on the second power line, and a control device that controls the buck-boost converter and the relay, and the control device is connected to the connector and the external power supply device and before turning on the charging relay. The voltage of the converter side portion of the second power line that is closer to the buck-boost converter than the charging relay is adjusted based on the voltage of the connector side portion of the second power line that is closer to the connector than the charging relay. The buck-boost converter is controlled so that the