Method for initializing a DC charging process of a battery by means of an inverter
View Patent ↗A method for charging a battery of an electric vehicle, at a direct-current charging apparatus, wherein the vehicle has an inverter which is connected to the battery, and an electric motor which is connected to the inverter. During the charging process, the inverter and at least one inductor of the electric motor are used for the step-up conversion of a low charging voltage of the direct-current charging apparatus into a higher voltage which is required for charging the battery.
1. A method for charging a battery of an electric vehicle at a direct-current (DC) charging apparatus, wherein the vehicle has an inverter, which is connected to the battery, and an electric motor, which is connected to the inverter, the electric motor having a star point, wherein the method comprises the steps of:
connecting a vehicle-side charging interface to the DC charging apparatus, wherein a first pole of the DC charging apparatus is coupled to a first pole of the battery, and the second pole of the DC charging apparatus is coupled to the star point of the electric motor;
ascertaining a first voltage which corresponds to the voltage of the battery;
driving at least one switch of the inverter, the at least one switch arranged between the first pole of the battery and an inductor of the electric motor, such that the switch moves to clocked operation;
ascertaining a second voltage established between the star point of the electric motor and the first pole of the battery by the clocked operation of the at least one switch of the inverter;
ascertaining a difference between the second voltage and a DC charging voltage provided by the DC charging apparatus; and
adjusting at least one of the DC charging voltage or the second voltage if the ascertained difference exceeds a prespecified limit value.
2. The method as claimed in claim 1 , wherein adjusting the DC charging voltage comprises transmitting at least one message to the DC charging apparatus.
3. The method as claimed in claim 1 , wherein adjusting the second voltage comprises adjusting a switch-on time of the at least one switch.
4. The method as claimed in claim 3 , wherein the switch-on time of the at least one switch is set depending on the first voltage.
5. The method as claimed in claim 1 , further comprising:
deactivating an insulation apparatus for creating a current flow from the DC charging apparatus to the battery when the difference between the second voltage and the DC charging voltage is below the prespecified limit value.
6. The method as claimed in claim 1 , wherein the inverter and the inductor of the electric motor are operated as step-up converters during charging of the battery.
7. The method as claimed in claim 1 , further comprising:
transmitting a precharging request to the DC charging apparatus for setting the DC charging voltage provided by the DC charging apparatus.
8. The method as claimed in claim 7 , wherein the clocked operation of the at least one switch is performed at the same time as or after the first voltage is ascertained.
9. The method as claimed in claim 8 , wherein the clocked driving of the at least one switch is performed by means of a PWM signal.
10. The method as claimed in claim 1 , wherein the first pole of the direct-current charging apparatus and the first pole of the battery are poles of the same polarity.