CN216467384U

CN216467384U - Charging device and electric drive system comprising such a charging device

Info

Publication number: CN216467384U
Application number: CN201990001065.4U
Authority: CN
Inventors: 不公告发明人
Original assignee: Hannah Electric Drive Co ltd
Current assignee: Hannah Electric Drive Co ltd
Priority date: 2018-10-08
Filing date: 2019-10-04
Publication date: 2022-05-10
Anticipated expiration: 2029-10-04
Also published as: DE102018124787A1; DE212020000285U1; WO2020074383A1

Abstract

The application relates to a charging device for charging a battery (7) of a motor vehicle designed with an electric drive motor (2), comprising at least one inductance and a drive converter (3) which, in a drive mode of the motor vehicle, changes the DC voltage of the battery (7) for the electric drive motor (2) and has an intermediate circuit center (5), wherein the at least one inductance together with the drive converter (3) acts as a step-up converter for a charging mode of the battery (7). For power optimization, the intermediate circuit center (5) is permanently or temporarily electrically connected or connectable to the input voltage and/or the inductance of the charging source (8).

Description

Charging device and electric drive system comprising such a charging device

Technical Field

The present application relates to a charging device for charging a battery of a motor vehicle designed with an electric drive motor and an electric drive system comprising such a charging device.

Background

Different charging concepts are used to charge electric vehicles. Charging by ac through a household socket is almost everywhere available, but it has only low charging power below 5 kW.

In contrast, in the case of rapid charging (DC charging) on a direct current power supply, it is possible to achieve much higher powers (50kW and higher), for example via special charging posts. However, when the voltage level of the charging post (typically 400V dc) is lower than the voltage level of the vehicle battery, particularly the vehicle battery, which typically has 800V dc, the voltage needs to be regulated.

For regulating the voltage level, a boost converter, which is also referred to as "boost chopper", "boost converter" or "boost converter", can be used as a separate structural unit. However, it is also possible to use an Inverter (also called "Inverter" in english) of a traction motor or an electric motor, which is known per se, as a boost converter for dc voltage conversion. In order to avoid having to use an additional inductance in the inverter for boost conversion, it is known to be possible to use the winding of the traction motor as a charging inductance:

DE 102016209905 a1 shows a quick charging unit for an electric vehicle, in which the inverter of the traction motor is used as a step-up converter in combination with the motor winding.

DE 102009052680 a1 shows the preconnecting of the buck converter upstream of the inverter.

DE 102016218304B 3 shows a three-level inverter in an NPC configuration ("neutral point clamped") for an electric vehicle, which can be operated as a boost converter in the fast charging mode, wherein an external inductance is used for the boost conversion.

In addition to two-level inverters with two voltage levels (e.g. 0V and 800V), there are also three-level inverters for electric vehicles, which additionally have third voltage levels, e.g. 0V, 400V and 800V.

In particular in three-level inverters with NPC topology, the voltage present at the switching elements of the half-bridge decreases in the blocking direction, for example to half the nominal voltage, for example 400V. These are correspondingly designed only for the cut-off voltage. Meanwhile, the off-voltage is allowed to inhibit the switching state in which the voltage is higher than the off-voltage is allowed. This impermissible state exists, for example, when only one switching element is switched off, while all other switching elements are switched to the on-state. This also applies to operation as a boost converter. Since it is virtually impossible to switch on both switching elements simultaneously, it is necessary to switch the switching elements to the target state over time, for example first switching the internal switching element and then the external switching element. During this time, current flows to the center of the intermediate circuit and accidentally charges it (or its capacitor) and further charges it with each switching cycle. If the voltage in the center of the intermediate circuit exceeds the permissible cut-off voltage of the switching elements or diodes, or if the voltage in the center of the intermediate circuit exceeds the permissible voltage of the capacitors, the relevant elements malfunction and the inverter fails. This must be avoided. In order to now charge the battery of an electric vehicle via an existing DC charging station, a control element in the form of a DC/DC converter is desired on the vehicle side. If a three-level NPC inverter is now used as a switching topology and it is desired to use it simultaneously as a DC/DC converter, a solution for voltage balancing of the intermediate circuit center voltage (in the intermediate circuit center between the two intermediate circuit capacitors C1 and C2), i.e. a solution for maintaining or maintaining the intermediate circuit center voltage, must be sought.

SUMMERY OF THE UTILITY MODEL

The object of the present application is therefore to provide an improved charging device for charging a battery of a motor vehicle designed with an electric motor. In particular, it should be noted that, in the charging operation, the voltage in the center of the intermediate circuit is not shifted to a technically relevant extent, in particular not exceeding the permissible semiconductor cut-off voltage.

To this end, a charging device according to the present application is provided. In particular, a charging device for charging a battery of a motor vehicle designed with an electric drive motor is specified, comprising an inductance and a drive converter which, in a drive mode of the motor vehicle, varies the dc voltage of the battery for the electric drive motor and has an intermediate circuit center, wherein, for a charging mode of the battery, the inductance together with the drive converter serves as a step-up converter. In the charging operation, the center of the intermediate circuit is permanently or temporarily electrically connected or connectable to the input voltage and/or the inductance of the charging source via the compensation line. A permanent or temporary electrical connection is understood here to mean, for example, that no or no switch is present for interrupting the compensation line. In this way, it is avoided that the capacitors of the intermediate circuit for symmetrical voltage distribution are charged to too different degrees during the charging process and that damage to the capacitors and/or switching elements or diodes occurs. The compensation current can flow out via the compensation line, which otherwise could accumulate in the capacitor and in the extreme case charge it to the battery voltage.

In order to use the drive converter as a step-up converter, it (in particular its transistor-type switching units) should be controlled accordingly during the charging operation in order to increase the input voltage (input voltage of the charging source) to a higher output voltage (output voltage of the vehicle battery). Wherein the switching unit is periodically opened and closed. According to the present application, the center of the intermediate circuit is electrically connected so that the compensation current can flow out while maintaining the precharge voltage. This can be achieved, for example, by connecting a compensation conductor to the inductance from the center of the intermediate circuit.

The compensation line is preferably embodied so as to be separable, for example, by means of a disconnector. In this way, the compensating lines can be separated for the driving operation, so that no leakage currents flow during the driving operation.

The center of the intermediate circuit is preferably connected or connectable to the input voltage circuit via a resistor. Thus, it is noted that the current to the intermediate circuit center and the charging source and/or inductor is limited.

Preferably, the resistor is embodied as a PTC resistor (positive temperature coefficient) so that the current flowing through the compensation line is limited, in particular in the event of a fault.

It has also proven to be advantageous if the inductance comprises or is at least formed by at least one winding of the electric drive motor. Therefore, additional components can be omitted, and cost and space requirements can be reduced.

Preferably, a plurality of inductances are provided, which are more preferably all designed as coil windings or windings for the excitation of the drive motor in the form of wave windings. Since the aim is to provide an efficient voltage conversion in the charging mode in addition to the control of the electric motor for the driving mode, the drive converter comprises a three-level inverter for the three voltage phases, which comprises in particular a half bridge for each of the three phases. Each three-level inverter is connected to one of the three windings of the electric drive motor. This also has the advantage that all three windings provided for the boost converter can be used individually or simultaneously, and thus the maximum possible charging power can be increased.

Preferably, the three half-bridges have the same middle circuit center. Preferably, the windings of the motor windings for the boost converter flow have a common star junction. It is thus possible to achieve a circuit connection between the center of the intermediate circuit and the inductor or the motor winding by means of only one line, whereby components and material are again saved.

In a further advantageous embodiment, the center of the intermediate circuit is arranged between two capacitors connected in series. In addition, at least one further capacitor can be switched in parallel and/or in series with at least one of the capacitors in order to change the size of the capacitors during charging operation and/or driving operation.

Preferably, the charging device has a control circuit for controlling the drive converter, in particular the half bridge thereof, wherein the drive converter is used as a boost converter for charging operation and as an inverter for driving operation. The control circuit can thus operate the drive converter in two operating modes, thereby saving costs for additional components.

Advantageously, the disconnection switch can be opened and closed cyclically during the charging operation. Thereby, a cyclic shift (rise and fall) of the intermediate circuit center voltage can be achieved without exceeding the allowed cut-off voltage in the process. On average, this increases the center voltage of the intermediate circuit. The increase in the voltage in the intermediate circuit during charging operation can have a favourable effect on the efficiency. For this reason, an intermediate circuit center voltage that is raised but still lower than the permissible cutoff voltage can be expected.

Preferably, the intermediate circuit voltage is around 800V, and the symmetrical intermediate circuit center voltage is 400V. In the charging mode, the intermediate circuit center voltage is preferably increased periodically, for example by 20%, since changes in the operating cycle have a positive effect on the efficiency.

The present application also contemplates an electric drive system comprising a charging device according to the present application and a vehicle battery.

When using a charging device according to the present application or as a charging method according to the present application, it has proven advantageous if at least the following steps are carried out, in particular in this order:

1. as soon as the motor is stopped, the intermediate circuit automatically discharges, whereby the intermediate circuit capacitor automatically discharges.

2. The charging device is connected to a charging post having a voltage level less than that of the vehicle battery as a direct voltage source: in this case, the charging post precharges the intermediate circuit capacitor of the drive system or of the charging device to the voltage level of the charging post.

3. The isolation switch between the center of the intermediate circuit and the inductor or charging source is closed only when the intermediate circuit capacitor has been precharged.

4. The charging process of the vehicle battery may be started.

Another charging method according to the present application is preset when the capacitor of the charging post has to be pre-charged by the vehicle. This method is preset for china, for example, because unlike in europe and the united states, charging posts precharge their own intermediate circuit and the vehicle intermediate circuit. The corresponding charging process presets at least the following steps, in particular in this order:

1. the motor is stopped and the intermediate circuit or capacitor is discharged autonomously.

2. The charging device is connected to a charging post having a voltage level less than that of the vehicle battery as a direct current voltage source.

3. The isolation switch in the compensation conductor is closed so that the center of the intermediate circuit is connected to the inductor and the charging source.

4. The intermediate circuit of the vehicle is precharged by means of a precharging resistor of the charging device, wherein the precharging resistor is preferably arranged between the vehicle battery and the intermediate circuit capacitor and can be bridged for the driving operation by means of a switch. At the same time, the intermediate circuit of the charging pile is precharged to the voltage of the central voltage of the intermediate circuit via the closed compensation conductor.

If necessary, the three-level inverter may be used as a buck converter or a boost converter.

5. The charging process is started.

Drawings

The following drawings illustrate preferred embodiments of the charging device according to the present application, wherein these are not to be considered limiting of the present application, but are mainly for illustration.

The figures show that:

fig. 1 shows a circuit diagram of an electric drive system comprising a charging device according to the present application;

FIG. 2 shows a circuit diagram of the electric drive system according to FIG. 1, in this case in a charging mode;

fig. 3A shows a detailed diagram of the circuit diagram of the half bridge of the drive converter of the electric drive system according to fig. 1 and 2;

fig. 3B shows a signal diagram of the currents of the individual components of the half bridge according to fig. 3A;

fig. 4 shows an equivalent circuit diagram of a half bridge, which includes corresponding control elements for the transistors, in order to function as a boost converter; and is

Fig. 5 shows a circuit diagram of an electric drive system comprising a charging device according to the present application according to a further preferred embodiment.

Detailed Description

Fig. 1 shows an electric drive system 1 equipped with an electric motor 2. The electric motor 2 comprises three inductances L1, L2 and L3 in the form of windings connected in circuit to star junctions, which are each supplied with current by means of half-bridges 4a, 4b and 4c of the drive converter 3 and can rotate the electric motor 2, in particular the rotor (not shown) thereof. The control of the half-bridges 4a, 4b and 4c is effected in such a way that the currents of the individual half-bridges are each phase-shifted by 120 ° relative to one another. Each half bridge 4a, 4b and 4c has the following components: four transistors (e.g. MOSFETs or IGBTs) T1, T2, T3 and T4 with diodes D1, D2, D3 and D4 respectively, and two diodes D5 and D6 connected to the middle circuit center 5 of the drive converter 3. The intermediate circuit center 5 is located between two intermediate circuit capacitors C1 and C2 arranged in parallel to the three half bridges 4a, 4b and 4C. The intermediate circuit center 5 is electrically connected to each half bridge 4a, 4b and 4c via a respective diode D5 and D6. The three inductances L1, L2 and L3 of the electric motor 2 are connected in a star connection with one another. Furthermore, the compensation line 9 runs from the center 5 of the intermediate circuit via a disconnecting switch S1 and a decoupling resistor R1 to the center of the star connection of the inductances L1, L2 and L3 of the electric motor 2 and to the plug connection 6 for a charging source (not shown). The plug connection 6 comprises two lines and can be separated from the drive system 1 via a first plug connection switch S2 and a second plug connection switch S3, as shown in fig. 1 in this case. The switch S2 is connected to the negative pole of the battery 7, the intermediate circuit capacitor C2 and the half-bridges 4a, 4b and 4C. The voltage level of the battery is, for example, 800V. The switch S3 is connected to the center of the star connection of the electric motor 2 and to the compensation line 9 or the decoupling resistor R1. The vehicle battery 7 is connected to the drive converter 3 and supplies it with a dc voltage. For the drive mode, the electric drive system 1 comprises control means (not shown) designed to control the half-bridges 4a, 4b and 4c and thus the transistors T1, T2, T3 and T4 thereof, so as to generate a current phase-shifted by 120 ° with respect to the other two currents, respectively. During the drive mode or driving mode, the switches S1, S2, and S3 are turned on.

Fig. 2 shows a circuit diagram of the electric drive system according to fig. 1. Here, the electric drive system 1 is in a charging mode, in which, unlike in fig. 1, the switches S1, S2 and S3 are closed and a charging source 8, for example in the form of a charging post, is connected as a dc voltage source to the plug connection 6. Since the voltage of the charging source 8 is 400V (compared to a battery voltage of 800V), the drive system 1, in particular the windings L1, L2 and L3 and the half bridges 4a, 4b and 4c, are used as a step-up converter or are operated accordingly.

Fig. 3A and 3B show a half bridge 4a comprising intermediate circuit capacitors C1 and C2 and five signal diagrams for in particular steering transistors T3 and T4, whereby the half bridge acts as a boost converter in combination with the inductance L1 of the motor (not shown). As can be seen from the signal diagram, the alternating current flows through an inductance L1 connected to the half bridge 4a. To control the current from the inductor L1 to the vehicle battery 7 (see fig. 1 or fig. 2), the transistors T3 and T4 are periodically closed. Since the transistors are not designed to switch off the full voltage of the vehicle battery and simultaneous switching of the transistors cannot be achieved at the same time, transistor T4 is first switched off and subsequently transistor T3 is switched off, or switched on again in the reverse order (see falling signal edge). During the short time that the transistor T3 is turned on and the transistor T4 is turned off or on, a short pulse of current flows through the diode D6 to the capacitor C2. Although the transistors T3 and T4 are thus protected against overvoltages; but on the other hand the current charges the capacitor C2 and thereby changes the voltage level at the intermediate circuit center 5. In order to prevent the voltage of the center voltage of the intermediate circuit from rising above the permissible cut-off voltage, a compensation line 9 (see fig. 1 and 2) is used, which is connected to the voltage source via a switch S1 and a resistor R1 and thus completes the voltage compensation. Once the two transistors T3 and T4 are turned off, the charging current flows to the vehicle battery 7 (see fig. 1 and 2) via the diode D2 and thus via D1. The transistors T1 and T2 are turned off all the time.

Fig. 4 shows a simplified circuit diagram of the electric drive system of the present application. Here, only the half bridge 4a comprising the intermediate circuit capacitors C1 and C2 is shown. Further, as an example of a winding of an electric drive motor, an inductance L1 is shown. By means of the step signal O1, the switch S1 is opened and closed, wherein the switch S1 may send a corresponding signal to the control circuit 12 to control the half bridge 4a as a boost converter. If switch S1 is closed, the control circuit 12 is supplied with a rectangular signal having a frequency of 20kHz (see element A2) instead of the 0V signal (see element A1). Here, the switch S1 controls the corresponding signal converter B1. The rectangular signal from a2 is passed to a first signal modifier Z1 and a second signal modifier Z2, respectively. The signal modifier Z1 is connected to transistor T3 and the signal modifier Z2 is connected to transistor T4. Here, the signal is modified, for example by a time shift of the signal, such that the transistor T4 is first switched off and subsequently the transistor T3 is switched off.

Fig. 5 shows a further electric drive system 1a comprising a charging device according to the present application according to a further preferred embodiment. The drive system 1a differs from the drive system 1 according to fig. 1 and 2 in that a pre-charge resistor 10 is arranged between the transistor C1 and the vehicle battery 7, which can be bridged via the shunt switch 11. Thus, the capacitors C1 and C2 may be charged before the charging process and the intermediate circuit center raised to the corresponding voltage level. During the driving mode, the switch 11 is closed. Before the charging operation, the switch 11 is turned on to precharge the capacitor; subsequently, for the charging process of the vehicle battery, the switch 11 is closed again. In conjunction with the compensation line 9 (with the switch S1 closed), the external inductance of the charging post can thus be precharged to an intermediate circuit center voltage which is lower than the battery voltage, for example.

List of reference numerals

1 electric drive system

1a electric drive system of another embodiment

2 electric motor/electric drive motor

3 inverter/drive converter

4a first half-bridge for a first phase

4b second half bridge for second phase

4c third half bridge for third phase

5 center of the intermediate circuit

6 plug connection

7 vehicle battery

8 charging source or charging pile

9 compensating conductor

10 pre-charging resistor

11 shunt switch for pre-charging resistor

12 control circuit

L1 first motor winding

L2 second motor winding

L3 third motor winding

C1 first capacitor

C2 second capacitor

T1 first transistor

T2 second transistor

T3 third transistor

T4 fourth transistor

D1 first freewheeling diode

D2 second freewheeling diode

D3 third freewheeling diode

D4 fourth freewheeling diode

D5 first intermediate diode

D6 second intermediate diode

R1 decoupling resistor

S1 isolating switch

S2 first plug connection switch

S3 second plug connection switch

A10V signal

Rectangular signal with constant A2 frequency

B1 controlled signal converter

Z1 Signal reducer-starting from the beginning of the Signal

Z2 Signal reducer-starting from the end of the Signal

O1 step signal.

Claims

1. A charging device for charging a battery (7) of a motor vehicle designed with an electric drive motor (2), comprising:

-an inductance of the inductor,

a drive converter (3) which, in a drive mode of the motor vehicle, changes the DC voltage of the battery (7) for the electric drive motor (2) and has an intermediate circuit center (5),

wherein for charging operation of the battery (7), the inductance together with the drive converter (3) acts as a boost converter,

it is characterized in that the preparation method is characterized in that,

the intermediate circuit center (5) is permanently or temporarily electrically connected to the input voltage of the charging source (8) and/or the inductance via a compensation line (9).

2. The charging device according to claim 1, wherein the charging device,

it is characterized in that the preparation method is characterized in that,

the intermediate circuit center (5) can be connected to the inductive circuit via a resistor (R1).

3. The charging device according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the inductance (L1) is formed by at least one winding of the electric drive motor (2).

4. The charging device according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the drive converter (3) has a half-bridge (4 a; 4 b; 4c) for each of the three voltage phases, wherein each half-bridge is connected to one of the three windings (L1; L2; L3) of the electric drive motor (2).

5. The charging device according to claim 4, wherein the charging device,

it is characterized in that the preparation method is characterized in that,

each half-bridge (4 a; 4 b; 4c) has the same intermediate circuit center (5).

6. The charging device according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the intermediate circuit center (5) is arranged between two capacitors (C1; C2) connected in series, wherein the battery (7) can be switched parallel to the capacitors (C1; C2).

7. The charging device according to claim 1 or 2,

it is characterized in that

Comprising a control circuit (10) for controlling the drive converter (3) used as a boost converter.

8. The charging device according to claim 1 or 2,

it is characterized in that

Comprising an isolating switch (S1) for electrically connecting the intermediate circuit center (5) with the input voltage of the charging source (8) and/or the inductance (L1).

9. The charging device according to claim 8, wherein the charging device,

it is characterized in that the preparation method is characterized in that,

the isolating switch (S1) is designed to be closed when a charging source (8) is connected to the charging device and thereby to electrically connect the intermediate circuit center (5) to the input voltage of the charging source (8) and/or the inductance (L1).

10. The charging device according to claim 8, wherein the charging device,

it is characterized in that the preparation method is characterized in that,

the isolating switch (S1) is designed to be opened and closed periodically during the charging operation.

11. The charging device according to claim 1 or 2,

it is characterized in that

Comprising a control circuit (10) for controlling the half-bridges (4 a; 4 b; 4c) of the drive converter (3) used as a boost converter.

12. An electric drive system (1), characterized in that it comprises a charging device according to any one of the preceding claims.