DE102012024573A1 - Method for operating internal combustion engine of electric car, involves controlling prime mover in state in which maximum producible electrical power from current braking torque is larger than electrical power receptible in energy store - Google Patents

Abstract

The method involves converting produced braking torque into electrical power by using a prime mover in generator mode of the prime mover. The electrical energy is partly stored in an energy store i.e. heavy-duty battery. The prime mover with a four-quadrant control is controlled in a state in which maximum producible electrical power from current braking torque is larger than the electrical power receptible in the energy store, so that electrical efficiency in generator mode is smaller than maximum possible electrical efficiency.

Description

The invention relates to a method for operating an electric drive machine of a vehicle, wherein a braking torque generated by the drive machine is converted into electrical energy in a generator operation of the drive machine and stored at least partially in an energy store.

From the prior art vehicles with electric drive machines and electrical energy storage devices are generally known. During operation of the vehicles occur driving situations in which the electric drive engine converts kinetic energy into electrical energy. Such driving situation are a so-called recuperation or a reversing operation. In these driving situations, the vehicle is braked by means of the electric drive machine, wherein the prime mover operates in a generator mode and supplies electrical energy to the energy store.

From the WO 2005/048446 A1 a method for braking a synchronous machine is known, are short-circuited in the armature windings of the synchronous machine with the interposition of at least one braking resistor. The short-circuit current is controlled by a pulse width modulation as a function of a difference between a nominal value of a braking torque corresponding setpoint and an actual value of the short-circuit current.

Furthermore, from the DE 100 60 368 B4 a method for controlling an asynchronous motor with a control device known. The asynchronous motor is provided with an inverter for controlling a current. For this control, when the asynchronous motor is started, a starting current component (ids) is supplied to the stationary asynchronous motor in a first method step, while a torque current component (iqs) remains equal to zero. In a second process step, the excitation current component (ids) is decreased while simultaneously increasing the torque current component (iqs) to a level given by iqs * = (Imax ² - ids ^{* 2} ) ^1/2 , where Imax represents a maximum allowable current ,

Furthermore, the describes DE 10 2004 018 945 A1 A method of operating a switched reluctance machine for a vehicle having a rotor and a number of coils, wherein an actual torque exerted by the coils on the rotor is maintained by applying a positive voltage to the coils in a first torque band. The actual torque is maintained by applying a negative voltage to the coils in a different second torque band from the first, with a transition of the actual torque from one to the other torque band in response to a flow of energy between the rotor and the coils. To decelerate the vehicle in forward travel, a positive torque is transmitted from the wheel of the vehicle to the reluctance machine. The reluctance machine is then in regenerative operation and transmits a negative torque to the wheel.

The invention is based on the object to provide a comparison with the prior art improved method for operating an electric drive machine of a vehicle.

The object is achieved by a method having the features specified in claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

In the method for operating an electric drive machine of a vehicle, a braking torque generated by the drive machine is converted into electrical energy in a generator operation of the drive machine and stored at least partially in an energy store.

According to the invention, the drive machine is controlled such that an electrical efficiency in the generator mode is smaller than a maximum possible electrical efficiency, at least in a state in which a theoretically maximum generated by a current braking torque electrical energy is greater than the recordable energy storage.

In vehicles with electric drive machines, such as electric vehicles, fuel cell vehicles and hybrid vehicles, electrical energy storage, such as high-performance batteries, flywheels, electrical capacitors and other memory used. These energy storage are characterized by the fact that they are at certain boundary conditions, such. As low temperatures, full state of charge or a high degree of aging, no or very little electrical energy during a charging, ie charging power record. The electric drive machine is operated as a generator during the so-called recuperation or reversing. In this generator mode kinetic energy is converted into electrical energy. However, the energy storage can not or only partially absorb this energy, for example, in the aforementioned boundary conditions. In such a situation, however, only a braking torque is applied in such a height that the electrical energy in recuperating Brakes can be absorbed by the energy storage or other consumers, there is a risk that the generated braking torque is too low. This means that the electric drive machine can not set a controlled braking torque or a braking power demanded by the driver by means of a brake pedal, so that an additional use of a mechanical brake of the vehicle is disadvantageously required.

By means of the method according to the invention, a control and / or regulation of the electric drive machine is realized, which allow the generation of the required braking torque, but provide the electrical energy only to the extent available, which can also be absorbed by the energy storage.

This results in a particularly advantageous manner, an increase in the life of the energy storage. This increase in the service life results from a reduction in the charging power conversion, in particular even at low ambient temperatures, since braking operations of the vehicle are not carried out exclusively by means of recuperation, but by means of the efficiency control. Furthermore, a high reproducibility of the vehicle behavior, in particular in driving conditions in which this is to be braked feasible. Such driving conditions are, for example, a start on a slope in which a rollback situation occurs opposite to the desired direction of travel, a reversing, in which a gear change or reversing occur, and a recuperation, in which a regenerative braking occurs.

Embodiments of the invention are explained in more detail below with reference to drawings.

Showing:

1 schematically direction of action directions of a rotational speed and a torque of an electric drive machine in a so-called four-quadrant operation,

2 schematically a torque curve in the case of a three-phase short circuit of the drive machine as a function of a rotational speed of the drive machine,

3 schematically a control circuit of the prime mover during the three-phase short circuit,

4 schematically a control circuit of the prime mover during idling of the prime mover,

5 schematically a torque-speed curve during recuperation, and

6 schematically a torque-speed curve during a recuperation and a limit characteristic of a torque-speed curve in three-phase short circuit of the prime mover.

Corresponding parts are provided in all figures with the same reference numerals.

In 1 are schematic direction of action directions of a speed and a torque in the 2 and 3 schematically illustrated electric drive machine 1 a vehicle in a so-called four-quadrant operation shown.

The vehicle is a purely electrically driven vehicle or a hybrid vehicle, wherein the vehicle comprises at least one energy store, in which electrical energy generated during a generator operation of the prime mover 1 is generated by this is stored. In a motor operation of the prime mover 1 Energy is taken from the energy storage, which is the prime mover 1 into kinetic energy.

When four-quadrant operation or in the so-called four-quadrant control is between the engine operation and the generator operation of the prime mover 1 distinguished. The engine operation, ie the electrical power consumption of the prime mover 1 , takes place in the first quadrant I and in the third quadrant III. The generator operation, ie the electrical power output, takes place in the second quadrant II and in the fourth quadrant IV.

In the first quadrant I becomes the prime mover 1 operated in the state of so-called "driving". In this case, the vehicle from the prime mover 1 driven and accelerated. Both the speed n and the torque M of the prime mover 1 act in a clockwise direction, ie clockwise. The vehicle moves in the forward direction.

Also in the third quadrant III is the prime mover 1 operated in the state of "driving". However, both the speed n and the torque M of the prime mover act 1 counterclockwise, ie in reverse. The vehicle is moving in the reverse direction.

In the second quadrant II and fourth quadrant IV is the prime mover 1 operated in contrast in the state of "braking". Here, the vehicle brakes and leads the prime mover 1 kinetic energy too. That is, the rotational speed n and the torque M of the prime mover 1 act in opposite directions. In the second quadrant II, the vehicle moves in the forward direction, in the fourth quadrant IV in the reverse direction.

The energy storage can under certain conditions, such. B. at low temperatures, full state of charge or a high degree of aging, no or very little electrical energy during generator operation of the prime mover 1 take up. In order to avoid that, consequently, the prime mover 1 a controlled or one of the driver of the vehicle, for example by means of a brake pedal in the 5 and 6 Described requested braking torque M _W or so-called desired braking torque can not set, in a state in which a theoretically maximum of a current braking torque of the drive motor can be generated electrical energy is greater than the recordable from the energy storage electrical energy, the prime mover 1 controlled such that an electrical efficiency in the generator mode is less than a maximum possible electrical efficiency.

For carrying out this method, a possible power consumption of the electrical energy store is detected by means of a first control unit (not shown), for example a battery control device of the energy store, and provided as signal _{P_el_zul_Energiespeicher} .

By means of the first control unit or a second control unit, a resulting electric power _{P_el_zul_Antrieb} , which of the _{prime mover} 1 may be generated in generator _mode , taking into account a power consumption P _{_el_Nebenverbraucher determined} by auxiliary electrical consumers of the vehicle according to the following equation. P _{_el_zul_Antrieb} = P _{_el_zul_Energiespeicher} + P _{_el_Nebenverbraucher} (1)

By means of a third control unit, the desired by the driver of the vehicle, in particular by means of a brake pedal requested braking torque M _W as a function of various information, such. B. an accelerator pedal position, a brake pedal pressure, information of an engaged gear or a gear, a direction of travel, a driving speed and other information determined.

A fourth control unit, for example an engine control unit of the prime mover 1 , determined from the size of the requested braking torque M _{W to be set} and the permissible electric power P _{_el_zul_Antrieb} the _{prime mover} 1 the possibilities for the best possible implementation of requested braking torque M _W while maintaining the permissible electrical power P _{_el_zul_Antrieb} the _{prime mover} 1 , For this purpose, different driving methods of the prime mover 1 used, which by the 2 to 6 be explained in more detail.

By means of the control method determined by the fourth control unit, a maximum implementable torque M _{max of} the drive _machine resulting from the permissible electrical power _{P_el_zul_Antrieb} 1 generated by means of which the vehicle is braked accordingly. A possible course of the maximum implementable torque M _max is in 6 shown in more detail.

Remains the amount of the maximum implementable torque M _{max of} the prime mover 1 below the amount of the requested braking torque M _W , an optical and / or audible warning is preferably generated within the vehicle, which indicates to the driver that the requested braking torque M _{W is} not or only partially from the prime mover 1 can be implemented.

Since the sizes of the maximum implementable torque M _{max of} the prime mover 1 the requested braking torque M _W dynamically depending on different sizes, such as the driving speed of driver actions, including accelerator pedal and brake pedal operations, and system changes, such as the state of charge of the energy storage, change, the maximum implementable torque M _{max is} continuously calculated and adjusted if necessary ,

Based on the following 2 to 6 is described as the requested braking torque M _W in generator mode by means of the prime mover 1 is generated, even if one of a current braking torque theoretically maximum generated electrical energy is greater than the recordable by the energy storage electrical energy.

2 shows a torque curve at three-phase short circuit of the prime mover 1 depending on the speed n of the prime mover 1 , wherein it is the prime mover 1 in particular is a permanently excited synchronous machine. The 3 and 4 show a control circuit 2 the prime mover 1 during the three-phase short circuit and during idling of the prime mover 1 ,

In such permanently excited synchronous machines, a speed-dependent braking torque M _{B is} generated by the three-phase short circuit via power amplifiers of a power converter.

The realization of a first operating state of the prime mover 1 with the three-phase short circuit takes place by means of the power converter and thus with the switching frequency of the power converter, which usually moves in the range of several kHz. These are circuit breakers 2.1 to 2.3 the control circuit 2 switched such that the three phases of the prime mover 1 are shorted. This switching state is in 3 Shown in more detail by the dashed line.

This allows a permanently pending braking torque M _B according to 2 be generated.

Also may be less than that in 2 shown brake torque M _{B are} generated. This takes place in that with a duty cycle set in dependence on the requested braking torque M between the first operating state and a second operating state, in which the driving machine 1 idle, is switched. That is, by setting the duty ratio between the activation of the three-phase short circuit according to FIG 3 on the one hand and a shutdown of the circuit breaker 2.1 to 2.3 the control circuit 2 according to 4 is switched, wherein the duty cycle between the first operating state and the second operating state is selected depending on the efficiency to be realized, wherein the duty cycle is increased to increase the efficiency and the duty cycle is reduced to reduce the efficiency.

This leads to a very fast switching between the braking torque M _B generated during the three-phase short circuit and a zero torque, so that, depending on the duty cycle, an average braking torque which is smaller than the braking torque M _B generated in the case of a three-phase short circuit is established.

Due to the high-frequency switching between the operating states and the inertia of the prime mover 1 this filters the high-frequency oscillation resulting from the fast switching, so that it is not noticeable to the driver of the vehicle or at least only to a small degree.

In a further embodiment of the method, the efficiency of the prime mover 1 if this is designed as a permanently excited synchronous machine, adjusted by impressing a first electric current in the field direction referred to as the so-called d-direction and a second electric current shifted by a predetermined angle in the so-called q-direction. In this case, an amount of the currents and the angle are selected such that the efficiency to be realized is generated.

This imprints a moment. Not only the height, but also the orientation of the current determines the resulting torque M. Preferably, d-components and q-components of the electric current are chosen so that a maximum torque M is generated at the smallest possible amount of current and thus minimal losses , This results in moments M in the second quadrant II and fourth quadrant IV to a maximum energy recovery in the energy storage, since the moments M mechanical braking power minus the losses in the drive machine 1 and in the associated power converter.

In order to adjust the height of the generated torque M to the requested braking torque M _W and the maximum implementable torque M _max , the current in the field direction is impressed in such a way that defined power loss is generated.

Depending on the requested braking torque M _B in the second quadrant II or fourth quadrant IV while the amount of current and its orientation are chosen such that the power loss is as large as the requested braking torque M _W beyond theoretical maximum possible of the prime mover 1 Generable braking torque. In this case, no energy recovery takes place in the energy storage.

The energy storage is in a state in which this can store electrical energy, the amount of the current and its orientation is chosen such that the power loss is as large as the sum of the above the requested braking torque M _W beyond theoretical maximum possible producible braking torque and the energy consumable by the energy storage. The power loss is infinitely adjustable.

In a further embodiment, the setting of the means of the prime mover 1 generated braking torque M _B and their efficiency by means of a combination of the operation with permanent or pulsed operation in three-phase short circuit and the targeted generation of power loss based on the defined impression of the current in magnitude and angle.

Thus, operating points can be realized in which low electrical power to the terminals of the drive machine 1 arise. In particular, a combined application of permanent or pulsed operation in three-phase short circuit and the targeted generation of power loss provided when the energy storage device can not absorb electrical energy, but the electrical auxiliary consumers, such as an electric vehicle interior heater, can absorb electrical energy. By means of a dynamic switchover between permanent or pulsed three-phase short circuit and the targeted generation of the power loss, it is possible to set exactly the electrical power that the consumer picks up.

Also, the combination of the operation with a permanent or pulsed three-phase short circuit and the targeted generation of power loss on the basis of the defined impression of the current in operating conditions applicable, in which the energy storage can absorb low power, all charging power to be adjusted are continuously generated.

Both the power generated during the generation of the three-phase short circuit as well as the impressing of the defined current is generated in the form of heat. This heat is in a particularly advantageous manner for rapid warming of a cooling circuit of the prime mover 1 , the power electronics used to control the same and / or a cooling circuit of another drive machine 1 of the vehicle, for example, an internal combustion engine in a hybrid vehicle usable.

Furthermore, the targeted generation of the power loss by means of the aforementioned driving methods can also be used for a cold start of the vehicle to the prime mover 1 and quickly heat up the power electronics. Indirect and protracted heating via the cooling circuit could be omitted.

To a driving behavior using the above-mentioned driving methods of the prime mover 1 For the driver in different operating and driving conditions reproducible and thus perform comprehensible, depending on a current operating and driving condition different control and / or regulation interventions in the drive system, in particular the prime mover 1 , performs.

One possible operating and driving state of the vehicle is a rollback situation occurring on a slope during a start-up process counter to the desired direction of travel, in which a gear or a drive step is engaged for driving in the intended direction.

The actual state predetermined by the driver in this situation is characterized in particular by a constant gear lever position and an actuation of the accelerator pedal and / or brake pedal for braking the vehicle. For example, the driver tries to slow down a roll back on the mountain.

A desired state of the energy storage is characterized in that the working by means of generator operating in the prime mover 1 generated electrical energy is to be absorbed as charging power.

An actual state of the energy storage, on the other hand, is characterized by the fact that it is already fully charged and can not absorb any further electrical energy.

An actual state of the prime mover 1 is characterized in that its operating point is in the fourth quadrant IV in the generator mode.

As a target state of the prime mover 1 is provided that this is to slow down the vehicle.

The control and / or regulation of the drive machine 1 takes place according to the described driving methods, wherein a suitable braking torque M _{B is} set. Depending on the permissible charging power of the energy storage, the permanent or pulsed three-phase short circuit is generated and / or the current is impressed correspondingly for targeted generation of the power loss. Thus, by means of the control and / or regulation of the prime mover 1 prevents an unrestrained downhill rolling of the vehicle.

It is also possible, without the operation of the accelerator pedal in the said situation slowly with brake assistance of the prime mover 1 roll back. Thus, a slow reverse drive, for example, for parking in a parking space, with engaged forward gear or inserted, provided for forward driving gear with an always same braking torque M _{B is} possible without an operation of the brake pedal is required.

Another possible operating and driving state of the vehicle is a so-called reversing process. This is, for example, a turning maneuver or a parking maneuver in which the driver arrives in forward motion and, during the forward travel, for example during coasting, changes into reverse or a corresponding driving position, in order then to drive the vehicle without actuating the accelerator pedal and the brake pedal by the drive machine located in generator mode 1 decelerate.

The reversing process can also be characterized by a change to a forward gear or a corresponding gear during a reverse drive. The control and / or regulation of the drive machine 1 in such a driving situation will be described below.

The vehicle is in a reverse driving situation with reverse gear engaged or gear engaged to reverse. This is the prime mover 1 operated in the third quadrant III.

The nominal state of the vehicle is that it should be braked from the reversing situation, possibly to a standstill. Optionally, the target state is that the vehicle is to be further accelerated forward from the backward movement when the accelerator pedal is further actuated.

The actual state of the driver specification is that the driver changes the gear lever position from the reverse gear or the corresponding gear stage into the forward gear or the corresponding gear stage with the accelerator pedal constantly pressed. The accelerator pedal is for example 50% actuated.

The desired state of the energy storage is characterized in that the working by means of generator operating in the prime mover 1 generated electrical energy is to be absorbed as charging power.

The actual state of the energy storage, on the other hand, is characterized by the fact that it is already fully charged and can not absorb any further electrical energy.

The actual state of the prime mover 1 Is characterized in that the operating point is in reverse gear engaged or corresponding gear, ie before switching to the forward gear or the corresponding gear, in the third quadrant III.

The nominal state of the prime mover 1 is that it should brake the vehicle after the gear shift. That is, it should be a change of the operating point of the prime mover 1 from the third quadrant III into the fourth quadrant IV.

In order to realize the desired states, the control and / or regulation of the drive machine takes place 1 according to the described driving methods, wherein after the gear change a suitable braking torque M _{B is} set. Depending on the permissible charging power of the energy storage, the permanent or pulsed three-phase short circuit is generated and / or the current is impressed correspondingly for targeted generation of the power loss. Thus, it is possible to provide the driver of the vehicle, the driving function "reversing" available.

Another possible operating and driving state of the vehicle is the so-called recuperation, in which in the generator mode of the prime mover 1 generated electrical energy is supplied to the energy storage. This process is schematic in 5 based on a curve of the requested braking torque M _W as a function of the rotational speed n of the drive machine 1 shown in the second quadrant II.

The actual state of the vehicle is that the vehicle is in a forward driving situation in forward driving position with engaged forward gear or corresponding driving position and the accelerator pedal is not actuated.

The prime mover 1 is operated here in the second quadrant II.

The desired state of the vehicle is that this is to be decelerated with a constant delay with continuously decreasing allowable electrical charging power of the energy storage, as this approach, for example, a full charge state. This is the case, for example, when driving on a downward slope.

The actual state of the driver's specification is characterized by the fact that this has chosen a constant gear lever position and the accelerator pedal is not actuated to allow the so-called engine brake and recuperation.

The desired state of the energy storage is that of the operated in the generator mode prime mover 1 generated electrical power is to be recorded as charging power.

The actual state of the energy storage, on the other hand, is characterized by the fact that it is already fully charged and can not absorb any further electrical energy.

The actual state of the prime mover 1 is characterized in that its operating point is in the generator operation in the second quadrant II.

The nominal state of the prime mover 1 is that it should slow down the vehicle.

In order to realize the desired states, the control and / or regulation of the drive machine takes place 1 according to the described Control methods, wherein a suitable braking torque M _B and the requested braking torque M _{W is} set. Depending on the permissible charging power of the energy storage, the permanent or pulsed three-phase short circuit is generated and / or the current is impressed correspondingly for targeted generation of the power loss. Thus, it is possible for the driver of the vehicle, a reproducible deceleration or deceleration of the vehicle within the technical limits of the prime mover 1 to enable. Thus, the vehicle always behaves the same from the perspective of the driver in the operating mode "recuperation".

This control and / or regulation of the prime mover 1 during the recuperation is through the 6 clarified, the means of the three-phase short circuit of the prime mover 1 can be implemented in generator mode convertible torque M _max in comparison to the requested braking torque M _W generated by means of the described control methods.

LIST OF REFERENCE NUMBERS

1

prime mover

2

control circuit

2.1 to 2.3

breakers

I

first quadrant

II

second quadrant

III

third quadrant

IV

fourth quadrant

M

torque

M _B

braking torque

M _W

requested braking torque

M _max

maximum feasible moment

n

rotation speed

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2005/048446 A1 [0003]
• DE 10060368 B4 [0004]
• DE 102004018945 A1 [0005]

Claims (6)

Method for operating an electric drive machine ( 1 ) of a vehicle, one of the engine ( 1 ) generated braking torque (M _B ) in a generator operation of the prime mover ( 1 ) is converted into electrical energy and stored at least partially in an energy store, characterized in that at least in a state in which one of a current braking torque (M _B ) theoretically maximum producible electrical energy is greater than the recordable by the energy storage electrical energy, the Drive machine ( 1 ) is controlled such that an electrical efficiency in the generator mode is smaller than a maximum possible electrical efficiency. A method according to claim 1, characterized in that a height of the generated braking torque (M _B ) in dependence of a particular requested by means of a brake pedal braking torque (M _W ) is set. A method according to claim 1 and 2, characterized in that for setting the efficiency, a first operating state of the drive machine ( 1 ) is set, wherein for generating the first operating state, a three-phase short circuit of the prime mover ( 1 ) is produced. A method according to claim 3, characterized in that between the first operating state and a second operating state in which the driving machine ( 1 ) is switched, wherein a duty cycle between the first operating state and the second operating state is selected depending on the realized efficiency, wherein for increasing the efficiency of the duty cycle is increased and to reduce the efficiency, the duty cycle is reduced. Method according to one of the preceding claims, characterized in that in a permanent-magnet drive machine ( 1 ) are impressed a first current in the field direction and a shifted by a predetermined angle to this second current, wherein an amount of the currents and the angle are chosen such that the realized efficiency is generated. Method according to one of the preceding claims, characterized in that - the drive machine ( 1 ) is controlled with a four-quadrant control, wherein - in a first quadrant (I) during a clockwise rotation of the drive machine ( 1 ) in the direction of rotation of this one torque (M) is impressed, - in a second quadrant (II) during a clockwise rotation of the drive machine ( 1 ) opposite to the direction of rotation of these a torque (M) is impressed, - in a third quadrant (III) in a reverse rotation of the drive machine ( 1 ) in the direction of rotation of this a torque (M) is impressed, - in a fourth quadrant (IV) in a reverse rotation of the drive machine ( 1 ) opposite to the direction of rotation of this torque (M) is impressed.

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