WO2020207619A1

WO2020207619A1 - Method for determining capacitances of bypass capacitors in a charging cable

Info

Publication number: WO2020207619A1
Application number: PCT/EP2020/025021
Authority: WO
Inventors: Karsten Hähre; Marija JANKOVIC; Raoul Heyne
Original assignee: Dr. Ing. H.C. F. Porsche Aktiengesellschaft
Priority date: 2019-04-12
Filing date: 2020-01-21
Publication date: 2020-10-15
Also published as: DE102019109720A1

Abstract

The invention relates to a method for determining capacitances of bypass capacitors in a charging cable during a charging process, in which method an energy store is charged by an energy source (100) via the charging cable, a first output of the energy source being electrically connected to a ground potential (PE) via a first bypass capacitor, a second output of the energy source (100) being electrically connected to the ground potential (PE) via a second bypass capacitor, a first test resistor and a first switch means (S₁) being connected in parallel with the first bypass capacitor, and a second test resistor and a second switch means (S₂) being connected in parallel with the second bypass capacitor. The method comprises the following steps. switching on the first switch means (S₁) so that the first output of the energy source (100) is connected to the ground potential (PE) via the first test resistor; switching on the second switch means (S₂) so that the second output of the energy source (100) is connected to the ground potential (PE) via the second test resistor; measuring a temporal profile of an electrical voltage (v₁) between the first output of the energy source (100) and the ground potential (PE); determining the capacitances of the bypass capacitors using the measured temporal profile.

Description

Process for the determination of capacities of bypass capacitors in one

Charging cable

The invention relates to a method for determining capacities of

Diverting capacitors in a charging cable during a charging process according to Claim 1

During the charging process of electrochemical energy stores, for example rechargeable batteries or accumulators, in motor vehicles, so-called

Bypass capacitors or interference suppression capacitors are used. You direct

high-frequency interference signals to the ground or the neutral conductor or short-circuit them, thus reducing the electromagnetic interference. The IEC 61851-23 and SAE J1772 standards specify limit values for the maximum energy that may be present in the capacitors. This also results in a limitation of the permitted capacitance for the bypass capacitors depending on the applied voltage.

DE 10 2015 016 000 A1 discloses a circuit arrangement for a motor vehicle which enables the Y discharge capacitors to be discharged. The capacities are not monitored during the charging process.

Monitoring the insulation resistances during a charging process is disclosed in FR 3026191 A1.

The insulation resistances are often determined using a resistance bridge. A measuring resistor is alternately switched between the positive and negative output potential of the energy source. This creates an asymmetry in the

Voltage curve, so that the energy present in one of the discharge capacitors can exceed the permissible limit value. In contrast, the present invention is based on the object of creating a method with which a better compatibility of an energy storage device

Motor vehicle can be reached with different charging stations. In addition, a system is to be created which is designed to carry out such a method.

This object is achieved by a method according to claim 1 and by a system according to claim 10. Embodiments of the invention are in the dependent

Claims stated.

While the method is being carried out, a chargeable energy store, preferably of a motor vehicle, is charged from an energy source via a charging cable. The energy source can include, for example, a public power grid or a charging station for an electronically operated motor vehicle. The charging cable can be connecting elements, e.g. Include plugs and / or sockets which are designed to be connected to the motor vehicle and to the energy source.

A first output of the energy source is electrically connected to a ground potential via a first bypass capacitor. A second output of the energy source is electrically connected to the ground potential via a second bypass capacitor.

A first test resistor and a first switching means are parallel to the first

Discharge capacitor switched. Here are the first test resistor and the first

Switching means connected one behind the other in series. A second test resistor and a second switching means are connected in parallel to the second bypass capacitor. The second test resistor and the second switching means are connected in series. In the context of this description, a parallel circuit is understood to mean a parallel circuit in the electrical sense. It is not necessary, but possible, that the relevant components are also arranged parallel to one another in the geometric sense. The same applies accordingly to the connection in series. The first and the second switching means can be switched on and off. In the switched-on state, electrical current can flow through the switching means, while in the switched-off state, no current can flow through the switching means.

The first switching means is switched on. In this state, the first output of the energy source is connected to the ground potential via the first test resistor.

The second switching means is switched on. In this state, the second output of the energy source is connected to the ground potential via the second test resistor.

A time profile of a first electrical voltage between the first output of the energy source and the ground potential is measured. The first output can for example be the positive output of the energy source. In addition, a time profile of a second electrical voltage between the second output of the

Energy source and the ground potential are measured. The second output can be, for example, the negative output of the energy source.

The capacitances of the bypass capacitors are determined using the measured time profile of the first electrical voltage. If the time course of the second electrical voltage was measured, this can also be used to determine the capacitances of the bypass capacitors. With this monitoring, in the event of an asymmetry of the voltage between the outputs compared to the

Ground potential, an excess of the permissible energy stored in the discharge capacitors can be detected. This increases the compatibility of the

Energy storage in the motor vehicle with various charging stations. Asymmetries that were created by measuring the insulation resistance can thus be recognized. If the energy stored in one of the bypass capacitors becomes too great due to such an asymmetry, the charging process can be aborted and the

Discharge capacitor are discharged. According to one embodiment of the invention, the discharge capacitors can be designed as Y discharge capacitors. In the context of this description, this is understood to mean, in particular, a class Y leakage capacitor in accordance with the IEC 60384-1 standard. They are connected between a phase or neutral conductor of the energy source and touchable and protective earthed components and bridge the insulation. With a limited capacity, Y discharge capacitors have a verifiable increased electrical and mechanical safety, as their use can endanger people in the event of a failure due to a short circuit.

According to one embodiment of the invention, it can be monitored whether the capacitances of the bypass capacitors each exceed a threshold value. When the threshold value is exceeded by at least one of the two discharge capacitors, the

Charging interrupted and the affected discharge capacitor discharged. This increases the safety for people in the vicinity of the energy source and the motor vehicle.

According to one embodiment of the invention, the second switching means can be switched off when the first switching means is switched on. This can take place in particular while the time profile of the first voltage is measured.

According to one embodiment of the invention, the first switching means can be switched off while the second switching means is switched on. This can take place in particular while the time profile of the first voltage is measured.

According to one embodiment of the invention, the first and the second switching means can be switched on simultaneously before the first switching means is switched off. This can take place in particular while the time profile of the first voltage is measured.

According to one embodiment of the invention, the second switching means can initially be switched off when the first switching means is switched on. After that it will second switching means switched on, while the first switching means remains switched on. The first switching means is then switched off while the second switching means remains switched on. These steps can in particular be carried out while the time profile of the first voltage is measured.

According to one embodiment of the invention, the first bypass capacitor can be arranged parallel to a first insulation resistor. Alternatively or additionally, the second bypass capacitor can be arranged parallel to a second insulation resistor. The insulation resistances increase the safety for people in the vicinity of the

Energy source and the motor vehicle. In addition, the insulation resistances can be used to determine the capacitance of the discharge capacitors.

According to one embodiment of the invention, resistance values of

Insulation resistances can be determined. The resistance values can be used to determine the capacitance of the discharge capacitors.

The system of claim 10 includes a motor vehicle having the rechargeable

Energy storage, the charging cable and the energy source. The motor vehicle comprises a control device which is designed to implement a method according to one of the preceding

Perform claims while the energy storage device is charged from the energy source via the charging cable.

Further features and advantages of the present invention will become clear on the basis of the following description of a preferred exemplary embodiment with reference to the accompanying figures.

Fig. 1 shows a schematic circuit diagram of a device for determining the

Capacitance of bypass capacitors; and FIG. 2 shows a schematic diagram of a time profile of two measured electrical potentials.

An energy source 100 outputs a voltage VDC via a positive and a negative output, which is used for charging an energy store

Motor vehicle is used.

The positive output is electrically connected to the capacitance C _{y +} , a first insulation resistor R _{S0 +} and a first test resistor Rt _es t ₊ to a ground potential PE via a first Y leakage capacitor. The first bypass capacitor, the first

Insulation resistance R _{S0 +} and the first test resistance Rt _es t ₊ are connected in parallel to one another. A first switching means Si is in series with the first

Test resistor Rt _es t ₊ switched so that the connection of the positive output to the ground potential PE can be switched on and off via the first test resistor.

The negative output is electrically connected to the capacitance C _y , a second insulation resistor R _S0 and a second test resistor Rtest- to a ground potential PE via a second Y leakage capacitor. The second bypass capacitor, the second insulation resistor R _S0 and the second test resistor Rtest are connected in parallel to one another. A second switching means S2 is in series with the second

Test resistor Rtest switched so that the connection of the positive output to the ground potential PE can be switched on and off via the second test resistor.

The voltage between the positive output and the ground potential PE can be measured by means of a first measuring device and is referred to as vi. The voltage between the negative output and the ground potential PE can be measured by means of a second measuring device and is designated as V2.

In order to determine the capacitances of the bypass capacitors C _{y +} and C _y during the charging process, the switching means Si and S2 are switched as follows. First will the first switching means Si switched on, so that the positive output is connected to the ground potential via the first test resistor Rt _es t +. The second switching means S2 is then switched on, while the first switching means Si remains switched on. In this state, the negative output is connected to the ground potential via the second test resistor Rtest. The first switching means Si is then switched off, while the second switching means S2 remains switched on.

In this connection of the two switching means Si and S2, the course of the measured voltages vi and V2 shown in FIG. 2 results. During a first time period 1, the first switching means Si is on and the second switching means S2

switched off. During a second time period 2, the first switching means Si and the second switching means S2 are both switched on. During a third time period 3, the first switching means Si is switched off and the second switching means S2 is switched on. The third period 3 is followed by the first period 1 again.

At the beginning of each period, recharging takes place, after the end of which a constant voltage is established within the respective period. The period of time required for the reloading during the transition from the first period 1 to the second period 2 is denoted by 5x2. The period of time required for the reloading during the transition from the second period 2 to the third period 3 is denoted by 5x ₃ . The period of time required for the reloading during the transition from the third period 3 to the first period 1 is denoted by 5xi.

The resistance values of the two test resistors Rt _es t + and Rtest are known. The resistance values of the two insulation resistances R | _S0 + and R | _S0 can be calculated using the following formulas:

R test + R iso +

R test + + R iso +

Vi (2) = v D, C

Rtest + * Rjso + Rtest— * Rjso-

Rtest + Riso + Rtest- R iso - Riso +

Vi (3) = v D, C

Rtest- Rjso-

R + R iso +

test - Riso-

Here vi (x) denotes the constant voltage in the period x between the positive output and the ground potential PE.

The time spans ti to 13 can be measured. From these, the effective total capacitance C _{e of} the Y discharge capacitors can be calculated using the following formulas. The following applies here: C _e = C _{y +} + Cy.

During the transition from the third period 3 in the first period of the second bypass capacitor 1 having the capacitance C _y up and the first bypass capacitor having the capacitance C _{+ y} is discharged. The effective capacitance C _e is therefore reloaded by connecting Riso +, Riso and Rtest + in parallel. This explains the formula for calculating the first time period ti.

During the transition from the first period 1 to the second period 2, the effective capacitance C _e is reloaded from all resistors by the parallel connection. This explains the formula for calculating the second time period 12. During the transition from the second period 2 to the third period 3, the effective capacitance C _{e is} reloaded via the parallel connection from R _{S0 +} , Rtest Riso. This explains the formula for calculating the third time period 13. The capacities C _{y +} and C _{y of} the two Y leakage capacitors can then be determined from the effective capacitance C _e .

Claims

1. Procedure for the determination of capacities of bypass capacitors in one

Charging cable during a charging process, in which a rechargeable energy store is charged via the charging cable from an energy source (100), the charging cable comprising a first bypass capacitor and a second bypass capacitor, a first output of the energy source (100) having a ground potential via the first bypass capacitor (PE) is electrically connected, a second output of the energy source (100) being electrically connected to the ground potential (PE) via the second discharge capacitor, a first

Test resistor and a first switching means (Si) parallel to the first

Bypass capacitors are connected, a second test resistor and a second switching means (S2) being connected in parallel to the second bypass capacitor, the method comprising the following steps:

- Switching on the first switching means (Si) so that the first output of the energy source (100) via the first test resistor with the

Ground potential (PE) is connected;

- Switching on the second switching means (S2) so that the second output of the energy source (100) via the second test resistor with the

Ground potential (PE) is connected;

- Measurement of a time profile of a first electrical voltage (vi) between the first output of the energy source (100) and the ground potential (PE); and

- Determination of the capacitances of the discharge capacitors using the measured time profile of the first electrical voltage.

2. The method according to claim 1, characterized in that the

Diverting capacitors are designed as Y diverting capacitors.

3. The method according to any one of the preceding claims, characterized in that it is monitored whether the capacities of the diverting capacitors each exceed a threshold value, and if the threshold is exceeded by the first diverting capacitor and / or by the second diverting capacitor, the charging process is interrupted and the respective diverting capacitor is discharged.

4. The method according to any one of the preceding claims, characterized in that the second switching means (S2) is switched off when the first switching means (Si) is switched on.

5. The method according to any one of the preceding claims, characterized in that the first switching means (Si) is switched off, while the second switching means (S2) is switched on.

6. The method according to any one of the preceding claims, characterized in that the first switching means (Si) and the second switching means (S2) simultaneously

are switched on before the first switching means (Si) is switched off.

7. The method according to any one of the preceding claims, characterized in that first the second switching means (S2) is switched off when the first

Switching means (Si) is switched on, and that then the second switching means (S2) is switched on while the first switching means (Si) remains switched on, and that afterwards the first switching means (Si) is switched off while the second switching means (S2) remains switched on .

8. The method according to any one of the preceding claims, characterized in that the first bypass capacitor is parallel to a first insulation resistor and / or the second bypass capacitor is parallel to a second

Insulation resistance is arranged.

9. The method according to the preceding claim, characterized in that

Resistance values of the insulation resistances are determined, whereby the

Resistance values are used when determining the capacitance of the bypass capacitors.

10. System comprising a motor vehicle with the chargeable energy store, the charging cable and the energy source (100), wherein the motor vehicle comprises a control device which is designed to carry out a method according to any one of the preceding claims, while the energy store via the charging cable of the Energy source (100) is charged.