Traction battery charging station

Abstract

Traction battery charging station (10) for direct current charging of a traction battery (24) of a motor vehicle (20) with an electric traction motor, with a power voltage converter (50) which, during charging operation, feeds an electrical DC voltage charging power into a pair of two charging lines (L1, L2), a charging controller (52), and an insulation monitor (30) with two electrical measuring resistors (36, 36') which are each connected to a charging line (L1, L2) and can each be connected to protective earth (38) via a resistance switch (34, 34'), wherein the insulation monitor (30) monitors the electrical insulation of the charging line pair (L1, L2) to protective earth (38) when not charging and when charging the traction battery (24), wherein the insulation monitor (30) has a test mode control (32) which has stored and can control an asymmetrical test mode in which one resistance switch (34, 34') is closed and the other resistance switch (34', 34) is simultaneously open, and a symmetrical load test mode in which both resistance switches (34, 34') are simultaneously closed or simultaneously open, wherein a complete insulation test is mandatory before each charging process by the insulation monitor (30) in both asymmetrical test mode and symmetrical test mode, and wherein during a charging operation reported by the charging control (52) to the insulation monitor (30) the test mode control (32) exclusively activates the symmetrical test mode, so that the resistance switches (34,34') are opened and closed exclusively synchronously with each other.

Description

[0001] The invention relates to a traction battery charging station for charging a motor vehicle traction battery with direct current.

[0002] The traction battery charging station includes a power-to-voltage converter that provides a DC charging voltage during charging and feeds it into a pair of DC charging lines. The charging station has a charging controller that monitors, controls, and regulates the charging process and its preparation. For safety reasons, traction battery charging stations require electrical insulation monitoring, which electrically monitors the insulation or resistance between the charging lines and the protective earth. Such charging stations are known, for example, from DE 10 2015 107 161 A1 and DE 10 2015 110 023 A1.

[0003] German patent DE 10 2015 108 995 A1 describes a charging station for electric vehicles. The charging station has an insulation monitor, whereby interference effects during the operation of the insulation monitor are avoided and the charging station is operated in different operating modes.

[0004] Detection of symmetrical and asymmetrical insulation faults is known from DE 10 2015 117 678 A1, DE 10 2013 226 595 A1, DE 10 2017 113 533 A1 and US 2011 130 421 A1.

[0005] A typical insulation monitoring system for a charging station consists of an insulation monitor with two electrical measuring resistors or circuits, each connected to a charging cable and capable of being connected to the protective earth via a resistance switch. When the resistance switch is closed, the insulation resistance of the respective charging cable can be determined very precisely, for example, via a resistance bridge, of which the measuring resistor is a part. Legal safety regulations require the detection of both so-called symmetrical insulation faults, caused, for example, by the aging of insulation materials, and so-called asymmetrical insulation faults, caused by sudden damage.

[0006] Asymmetrical insulation faults can be detected using a symmetrical test mode in which both resistance switches are closed simultaneously, allowing the insulation resistance of each charging cable pair to be determined individually. However, this method cannot detect symmetrical insulation faults. Symmetrical insulation faults are detected using an asymmetrical test mode in which the resistance switches are only opened and closed alternately, meaning that the insulation resistance of each charging cable is measured individually.

[0007] Typically, both charging cables are continuously and alternately tested in symmetrical and asymmetrical test modes, both before and during the actual charging process. However, the asymmetrical test mode limits the electrical robustness of the charging station and the vehicle during charging. Under certain operating conditions, this can lead to malfunctions, particularly disrupting communication between the charging station and the connected vehicle.

[0008] The object of the invention is therefore to create a traction battery charging station with an insulation monitor that prevents electrical interference between the charging station and the motor vehicle.

[0009] This problem is solved according to the invention by a traction battery charging station with the features of claim 1.

[0010] The traction battery charging station according to the invention is designed for charging a traction battery of a motor vehicle equipped with an electric traction drive. The charging station has a power-to-voltage converter which, during charging operation, feeds a DC charging current into a pair of DC charging lines. The two charging lines are also referred to as the positive charging line and the negative charging line and are part of a closed and electrically ungrounded charging circuit that is galvanically isolated from the protective earth.

[0011] The charging station features an insulation monitor with two ohmic measuring resistors, each connected to a charging cable and, at the other end, connected to the protective earth via a switchable resistor. With the resistor switch closed, the ohmic insulation resistance of the connected charging cable to the protective earth can be determined, for example, using a resistor bridge.

[0012] According to the invention, the insulation monitor has a test mode control that stores and can control an asymmetrical non-charging test mode, in which one resistance switch is closed and the other resistance switch is simultaneously open, or vice versa, and a symmetrical charging test mode, in which both resistance switches are either closed or open simultaneously. This ensures that no asymmetrical test mode is activated during a charging process.

[0013] The insulation monitor receives information from another control element of the charging station as to whether a charging process is active, or whether the vehicle is electrically connected to the charging station. If the insulation monitor receives a notification of an active charging process, or alternatively or additionally, a notification of an electrical connection between the vehicle and the charging station, the insulation monitor switches to charging test mode, in which only a symmetrical insulation measurement can be performed.

[0014] Before each charging process, the insulation monitor performs a mandatory, complete insulation test in both asymmetric and symmetric test modes. This can be done, for example, using a bus-shifting method. This determines the insulation condition of both charging cables up to the charging station's charging plug. As soon as the charging process begins, the test mode control switches to charging test mode, in which only the symmetric test mode is executed. While the symmetric test mode does not detect age-related or systematic deterioration of the electrical insulation of the charging cables relative to the protective earth, a less frequent check, such as a daily check, is naturally sufficient for this purpose.Therefore, omitting the asymmetrical test mode during the charging process does not significantly impair insulation safety monitoring.

[0015] The dDe test mode control activates only the symmetrical charging test mode during the charging operation reported by the charging control to the insulation monitor.

[0016] Alternatively or additionally, the charging station's charging plug, into which the charging cable pair terminates, can have a connection sensor that detects when the charging plug is connected to a vehicle's charging socket. The test mode control is informally linked to the connection sensor. Upon receiving a signal from the connection sensor, the test mode control activates the symmetrical charging test mode. This ensures that the insulation monitor only operates in the symmetrical charging test mode once the charging station is electrically connected to the vehicle in question.

[0017] The insulation monitor can also be designed to regularly perform a self-test, both before and during the connection of the charging station-side charging plug to a vehicle-side charging socket.

[0018] An embodiment of the invention will be explained in more detail below with reference to the drawings. The drawings show: Fig. 1 schematically a traction battery charging station with an insulation monitor and an integrated test mode control in non-charging test mode, as well as a disconnected motor vehicle, and Fig. 2 the arrangement of Fig. 1 with the connected motor vehicle and the test mode control in charging test mode.

[0019] The figures schematically show an arrangement consisting of a traction battery charging station 10 and a motor vehicle 20 with a traction battery 24, which has an electric traction motor.

[0020] The charging station 10 has a power-to-voltage converter 50, which is supplied with alternating current from a public electricity grid 12 and which has galvanic isolation 54. The power-to-voltage converter 50 supplies a pair of charging lines L1, L2 with high-voltage direct current charging power. The charging station 10 also has an electronic charging controller 52, which monitors all processes of the charging station 10, and in particular monitors and controls the charging process and its preparation. The two charging lines L1, L2 terminate in a charging station-side charging plug 21, which can be plugged into a corresponding vehicle-side charging socket 22, as shown in Fig. Figure 2 shows the charging plug 21 having a connection sensor 21' which detects the connection of the charging plug 21 with the charging socket 22.

[0021] When the charging plug 21 is connected to the charging socket 22, the traction battery 24 of the motor vehicle 20 can be charged via the two charging lines L1, L2.

[0022] The charging station 10 also includes an insulation monitor 30 through which the two charging lines L1, L2 pass. Each charging line L1, L2 is connected in the insulation monitor 30 to a measuring resistor 36, 36' and a resistance switch 34, 34' connected in series with the measuring resistor 36, 36'. When the resistance switch 34' is closed, the respective charging line L2 is electrically connected to the protective earth 38 via the respective measuring resistor 36'. The measuring resistor 36, 36' can be configured as part of a resistance bridge, the imbalance of which is measured in order to precisely determine the electrical insulation resistance of the respective charging line L1, L2 with respect to the protective earth 38.

[0023] The insulation monitor 30 has a test mode control 32 which is electrically and / or informally connected to the measuring resistors 36, 36', the resistance switches 34, 34', the charging control 52, and the connection sensor 21'. The test mode control 32 has, among other things, two stored test modes: an asymmetrical non-charging test mode in which one of the two resistance switches 34' is closed and the other resistance switch 34 is open, or vice versa; and a symmetrical charging test mode in which both resistance switches 34, 34' are always closed or open simultaneously.

[0024] As soon as the charging controller 52 registers a charging request, this is also registered by the test mode controller 32, which then starts the non-charging test mode and performs both a symmetrical and a non-symmetrical test of the insulation resistance of the two charging lines L1, L2. In particular, the test mode controller 32 performs the non-symmetrical test in which the two resistance switches 34, 34' are closed and opened several times in a complementary manner according to a so-called bus-shifting procedure, as shown in Fig. Figure 1 shows this. In particular, symmetrical faults or symmetrical changes in the insulation resistance of the two charging lines L1, L2 are detected.

[0025] As soon as the charging controller 52 signals the start of charging or the connection sensor 21' reports the mechanical and electrical connection of the charging plug 21 with the vehicle's charging socket 22, the test mode controller 32 switches to the charging test mode, in which only a symmetrical test of the insulation resistances of the two charging lines L1, L2 is carried out, as shown in Fig. 2 shown. As long as the charging operation continues or the charging station 10 and the motor vehicle 20 are electrically connected, the test mode control 32 does not switch off the charging test mode, so that no asymmetrical measurement of the insulation resistance of the charging lines L1, L2 is carried out during the charging operation or during the exchange of information between the motor vehicle 20 and the charging station 10.

Claims

[1] Traction battery charging station (10) for direct current charging of a traction battery (24) of a motor vehicle (20) with an electric traction motor, with a power voltage converter (50) which, during charging operation, feeds an electrical DC voltage charging power into a pair of two charging lines (L1, L2), a charging controller (52), and an insulation monitor (30) with two electrical measuring resistors (36, 36') which are each connected to a charging line (L1, L2) and can each be connected to protective earth (38) via a resistance switch (34, 34'), wherein the insulation monitor (30) monitors the electrical insulation of the charging line pair (L1, L2) with respect to protective earth (38) when not charging and when charging the traction battery (24), wherein the insulation monitor (30) has a test mode control (32) which has stored and can control an asymmetrical test mode in which one resistance switch (34, 34') is closed and the other resistance switch (34', 34) is simultaneously open, and a symmetrical load test mode in which both resistance switches (34, 34') are simultaneously closed or simultaneously open, wherein a complete insulation test is mandatory before each charging process by the insulation monitor (30) in both asymmetrical test mode and symmetrical test mode, and wherein during a charging operation reported by the charging control (52) to the insulation monitor (30) the test mode control (32) exclusively activates the symmetrical test mode, so that the resistance switches (34,34') are opened and closed exclusively synchronously with each other. [2] Traction battery charging station (10) according to claim 1, wherein the charging line pair (L1, L2) terminates in a charging station-side charging plug (21) which has a connection sensor (21') which detects the connection of the charging plug (21) with a vehicle-side charging socket (22), wherein the test mode control (32) switches on the charging test mode exclusively when a connection is reported by the connection sensor (21').

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