AT510025A4 - DRIVE UNIT OF AN ELECTRIC VEHICLE - Google Patents

Description

201009186 * »a ·· · ·« ·· •

Drive unit of an electric vehicle

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The invention relates to a drive unit of an electric vehicle, comprising an electric machine, which is connected via a bidirectionally designed converter to an energy store.

The drive of an electric vehicle usually includes a trained as a DC voltage energy storage. In the ferry mode, energy is transmitted from the energy store via an inverter operated as an inverter to an electric machine for driving the vehicle. In the case of a braking force recovery, the electric machine operates during a braking operation in the generator mode. Mechanical energy is converted into electrical energy and passed through the drive operated as a rectifier in the energy storage.

The inverter thus operates depending on the operation of the electric machine as an alternator or as a rectifier. The inverter converts either AC or AC to DC, or vice versa, to DC or AC. The energy store is located in a voltage intermediate circuit.

Multicellular rechargeable batteries are usually used as energy stores, optionally with a precharge circuit. When charging or discharging the energy storage various aspects are to be considered, which depend primarily on the selected battery type. For example, precautions must be taken against over-discharge or, after extended periods of inactivity, short periods of discharge should be provided, as required for lithium-ion accumulators to avoid damaging chemical processes. Discharge operations are important even if they do not exist ·, | ♦ ♦ * * · »» ··· »*» · · »····················································· 4 *

Energy storage in vehicles as storage stations within an intelligent energy network, also called Smart Grid, are used.

Various known charging concepts are briefly explained below. The easiest way to make a vehicle with an empty energy storage ready to drive is to replace the battery at a corresponding service point. A charging of the energy storage is then carried out in a known manner outside the vehicle.

Furthermore, external charging stations are known which contain the entire charging technology. In this case, the energy store is left in the vehicle, but is disconnected electrically from the other components of the drive system and connected to such an external charging station. This variant has the disadvantage that each charging station to be newly built is complicated and expensive. Public charging stations must be suitable for different types of energy storage, for example, have different data protocols, charging voltages, connectors and, if necessary, filter designs and limit currents.

To overcome this disadvantage, one also knows solutions which provide a simply constructed charging station and a charger in the vehicle. The simple charging station consists essentially of a mains connection, which is optionally provided with filter components. During a charging or discharging process, the charger in the vehicle is supplied with mains power via a charging cable. The energy storage is separated from the components of the drive system and connected to the charger. The charger will take charge or discharge management until the vehicle is disconnected from the mains. The disadvantages here are the weight and space requirement of the charger as well as the need for power dissipation in the vehicle, as well as the cost of an additional power converter. 2 201009186

The invention has for its object to provide an improvement over the prior art for a drive unit of the type mentioned.

According to the invention this object is achieved by a drive unit according to claim 1. Improvements are given in the dependent claims.

It is envisaged that in the generic drive unit of an electric vehicle with an electric machine, which is connected via a bidirectionally designed inverter to an energy storage, the energy storage for charging or discharging by means of this inverter to an external charging station is switchable. So there is no separate charger provided in the vehicle, but the inverter of the drive unit is used with a connected charging station as a charging or discharging for energy exchange between energy storage in the electric vehicle and externally located charging station. The charging station is connected either to a supply network or to another source of energy such as an emergency generator. A control of the drive unit, which is set up to control the converter in the ferry mode, preferably also assumes the charge or discharge management. The current drawn from the grid or fed there is practically sinusoidal with a resulting extremely low harmonic load of the network.

In addition to the advantage that a suitable external charging station has low complexity, there is no additional space or weight problem in the vehicle due to the consistent use of the inverter by a separate charger. The reduction of components compared to the prior art also leads to increased reliability due to lower failure risk. Apart from that, a defect 3 201009186 of the inverter not only appears in the ferry service, but also when the vehicle is connected to the charging station.

In charging mode, the inverter works as an active rectifier, which practically causes no harmonic load on the connected supply network.

Advantageously, the electric machine is designed as a three-phase machine. Such machines are virtually maintenance free and inexpensive compared to other types. In addition, in the case of a synchronous machine excited by means of permanent magnets, a high power density with low weight is provided.

In a simple embodiment, a disconnecting device is provided for switching off the electric machine during a charging or discharging process of the energy store. It is thus safely avoided that a torque is generated at the electric machine, as long as the vehicle is connected to a charging station.

It is advantageous if separations within a stator and / or a rotor of the electric machine can be separated by means of a separating device. The windings of the stator can then be used as damping filter elements during a charging or discharging process of the energy accumulator.

One embodiment provides that the stator comprises three windings which are arranged in a star connection and that detachable electrical contacts of the separation device are provided for separating a neutral point.

Another embodiment provides that the stator comprises three windings, which are arranged in a delta connection and that detachable electrical contacts of 4 201009186

Separating device are each arranged in series with a winding. For additional protection, it is favorable if a vehicle socket for connecting the drive unit to the external charging station is mechanically coupled to the disconnecting device in such a way that in the connected state the electric motor is switched off by means of a disconnecting device.

In this way, there is an inadvertent lock which prevents the vehicle from erroneously starting with a connected charging cable. Cable break, risk of injury, destruction of the charging station or vehicle socket are thus avoided.

An alternative to this provides that the separating device is controlled by means of a control circuit. In the simplest case, the control of the inverter has the additional function of activating the disconnecting device when it is connected to a supply network. For this purpose, for example, the vehicle socket is provided with a sensor. This sensor detects whether a charging cable is connected to the vehicle socket and reports each change of state to the controller.

If no or only insufficient filter elements are provided in the charging station, filter elements are also used within the drive unit for sufficient avoidance of harmonics. In an advantageous embodiment, the stator windings of the electric machine are used as filter throttles. This is done by a charge or discharge path leads from the energy storage device via the inverter to the electric machine and further from taps of the stator windings to a vehicle socket. The positioning of the taps within the windings allows a tuning of the filter properties. 5

201009186 In the event that the rated current of the motor for a charging or. Unloading the energy storage sufficient, the entire stator windings are used without taps as filter elements. Then leads a charging or discharging path from the energy storage device via the inverter and the stator windings of the electric machine to a vehicle socket.

An alternative variant provides that a charging or discharging path leads from the energy storage device via the converter to a vehicle socket and that a separate filter arrangement is provided in this path. This allows independent of the electric machine Filterdimensionierung or filter adaptation to be complied harmonic loading of the network or to an adjustable charging current limit of the battery.

Throttle filters in the charge or discharge path have the effect, in addition to the damping effect, that the converter operating as a controlled rectifier acts as a voltage booster. Thus, the charging voltage can be adapted to the requirements of the energy storage, even at a low supply voltage.

An advantageous further development provides that a circuit breaker is arranged in a charging or discharging path between the energy store and a vehicle socket. Network faults or short circuits within the system will result in an immediate interruption of the current flow before extensive damage can occur.

The invention will now be described by way of example with reference to the accompanying drawings. In a schematic representation:

Fig. 1 drive unit and charging station with charging cable

Fig. 2 stator windings as filter elements with taps 6 201009186

Fig. 3 stator windings as filter elements

The drive unit 1 illustrated in FIG. 1 essentially comprises an electric machine 2, a converter 3 embodied as a three-phase bridge circuit, and an energy store 4. A controller is not shown for the sake of clarity. Switches of the converter 3 are controlled either as elements of an inverter or as elements of a controlled rectifier, also known as Active Line Module (ALM). As a rule, these switches are formed by transistors with parallel-connected diodes (preferably IGBT).

The energy store 4 preferably forms a multicellular battery. To reduce the peak current load on the battery, it is conveniently combined with supercapacitors, these elements then forming a DC link. Optionally, the battery is provided with a precharge circuit.

In the ferry mode, the direct current drawn from the power source 4 is converted by means of converter 3 into an alternating current and supplied to the electric machine 2. The electric machine 2 is preferably designed as a three-phase machine. This has a stand 6 and a rotor, not shown. Each of the three phases of the three-phase current is assigned to a stator winding. The variant shown in Fig. 1 shows a star connection of these stator windings. A triangular arrangement of the stator windings is selected if a different motor characteristic or voltage adjustment is desired.

In order to switch off the electric machine 2 during a charging or discharging process at a charging station 12, a separating device 5 is provided. In the present example of a star connection of the stator windings, the separation device 5 comprises two detachable electrical contacts to 7 201009186

Separation of the star point. In the case of a delta connection, a detachable electrical contact is provided in each case in series with a stator winding. If the stator windings are not required as filter elements during a charging or discharging process, the separating device 5 can also be arranged in a connecting line between the converter 3 and the electric machine 2.

For charging or discharging the energy storage 4, the three-phase output of the inverter 3 via a charging or. Discharge path 8 connected to a vehicle socket 7.

In this loading or unloading path 8, a circuit breaker 10 is conveniently arranged. The automatic circuit breaker 10 protects the drive unit against impermissible voltage peaks and short circuits as well as their consequences.

As shown in FIG. 1, a simple embodiment of the invention provides that a separate filter unit 9 is arranged in the loading or unloading path 8. In each strand of the three-phase line, a filter choke is provided. In addition to the reduction of harmonics, these chokes are used to operate the inverter 3 as a boost converter. To charge the energy storage 4 is then a higher charging voltage than the voltage available, which would normally result from a connected supply network LI, L2, L3. An alternative to this is a transformer, which can be integrated into the charging station 12. In addition to the adaptation of the charging voltage can be achieved in this way, a galvanic isolation between the drive unit 1 and the supply network LI, L2, L3. In addition, the stray inductances of the transformer act as filter elements.

Without separating transformer are in the charging or discharging at a charging station 12 of the energy storage 4, the inverter 3 and the electric machine circuit mains-powered. It is then a corresponding 8 4 4 · t 201009186

Insulation and cover of all live components required.

To the vehicle socket 7, a charging line 11 is connected. This is conveniently provided with a grounded shield. The charging line 11 connects as a flexible intermediate element, the charging station with the electric vehicle. It is advantageous if the vehicle socket 7 has a mechanical coupling with the separator 5. The function of this coupling then consists in triggering the separating device 5 as soon as the charging line 11 is connected to the vehicle socket 7. The separator 5 interrupts so long connections of the stator 6 and / or rotor of the electric machine 2, until the charging line 11 is disconnected from the vehicle socket 7 again. The vehicle can therefore not be put into operation as long as a charging or discharging takes place at a charging station.

Alternatively, the vehicle socket 7 has a sensor for detecting an infected charging line 11. A corresponding sensor signal is then fed to a controller for activating the separating device 5.

The charging station 12 optionally comprises filter throttles 13, which either supplement or replace the filter unit 9 of the drive unit 1. Possibilities to use the stator windings of the electric machine 2 as filter elements are shown in FIGS. 2 and 3. In Fig. 2, the individual windings of the stator 6 are tapped. From the taps leads a loading or. Discharge path to the vehicle socket 7, optionally with an intermediate circuit breaker. In order to avoid transformer effects, the stator winding circuit must also be open during landing or discharging of the energy accumulator 4. 9

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The location of the tap determines which portion of the stator windings act as filter chokes. If the respective entire stator winding is used as a filter choke, the taps are omitted, as shown in FIG. Then usually the rated current of the electric machine 2 is sufficient to charge the energy store 4. 10 10

Claims (12)

1. Drive unit (1) of an electric vehicle, comprising an electric machine (2), which is connected via a bidirectionally designed converter (3) to an energy store (4), characterized in that the energy store {4) for charging or discharging by means of inverter (3} to an external charging station (12) is switchable. 2. Drive unit according to claim 1, characterized in that the electric machine (2) is designed as a three-phase machine. 3. Drive unit according to claim 1 or 2, characterized in that a separating device (5) for switching off the electric machine (2) during a charging or discharging of the energy storage device (4) are provided. 4. Drive unit according to claim 3, characterized in that by means of separating device (5) connections within a stator (6) and / or a rotor of the electric machine (2) are separable. 5. Drive unit according to claim 4, characterized in that the stator (6) comprises three windings, which are arranged in a star connection and that detachable electrical contacts of the separating device (5) are provided for separating a star point. 6. Drive unit according to claim 4, characterized in that the stator (6) comprises three windings, which are arranged in a delta connection and that releasable electrical contacts of the separating device (5) are each arranged in series with a winding. 7. Drive unit according to one of claims 3 to 6, characterized in that a vehicle socket (7) to 11 201009186 · «#» (l · »« Φ * ΐ; Φ II Φ »* tt ι» • * * 4 · ν Connecting the drive unit (1) to the external charging station (12) is provided and that the vehicle socket (7) is mechanically coupled to the separating device (5) in such a way that in connected state, the electric machine (2) by means of separation device (5) is turned off. 8. Drive unit according to one of claims 3 to 6, characterized in that the separating device (5) is controlled by means of a control circuit. 9. Drive unit according to one of claims 4 to 8, characterized in that a charge or discharge path (8) from the energy storage device (4) via the inverter (3) to the electric machine (2) and further from taps of the stator windings to a vehicle socket (7). 10. Drive unit according to one of claims 4 to 8, characterized in that a charge or discharge path (8) from the energy store (4) via the inverter (3) and the stator windings of the electric machine (2) leads to a vehicle socket (7) , 11. Drive unit according to one of claims 1 to 8, characterized in that a charge or discharge path (8) from the energy store (4) via the inverter (3) leads to a vehicle socket (7) and that in this path a filter arrangement ( 9) is provided. 12. Drive unit according to one of claims 1 to 11, characterized in that in a loading or unloading path (8) between the energy storage (4) and a vehicle socket (7) a circuit breaker (10) is arranged. 12