DE102016206059A1 - Method and control unit for operating a rotating field machine at a standstill or starting a rotor of the induction machine, as well as vehicle drive train - Google Patents

Abstract

The invention relates to a method and a control device (6) for operating a rotating field machine (1) by means of an inverter (5) at a standstill or starting a rotor of the induction machine (1), wherein a space vector (204, 205, 301) for an electrical Current (iα, iβ; id, iq) or an electrical voltage for generating a magnetic stator field is oscillated to the electric current flowing through the inverter (5) (iu, iv, iw) via alternating power semiconductor switches of the inverter (5) respectively. Here, the vibration of the space vector (204, 205, 301) is a noise vibration.

Description

The invention relates to a method for operating a rotating field machine by means of an inverter at a standstill or starting a rotor of the induction machine. It also relates to a control device for controlling power semiconductor switch of an inverter for a rotating field machine with a determination module to determine a desired current or voltage space pointer for the induction machine, and it also relates to a vehicle powertrain with such a controller.

Electrical machines are, if they are provided as traction drive in a drive train of a motor vehicle, usually designed as a rotating field machines, for example as a synchronous or asynchronous machine. The control is usually carried out in multiple phases via an inverter, which can be designed in particular in a B6 bridge circuit with power semiconductor switch. By driving the power semiconductor switch with a pulse-width modulated drive signal (PWM), a voltage and current profile for operation of the induction machine is generated in the inverter from a DC voltage. Due to the voltage and current course, a magnetic field (stator field) is generated at the stator of the induction machine, which causes a certain torque on the rotor of the induction machine.

In order to calculate the PWM the space-time theory is used regularly. They allow a 3-phase system (uvw coordinate system for the phases of the induction machine) to be replaced by an orthogonal, stator-fixed α-β coordinate system, which simplifies the description and thus the control of the system. Through the introduction of the α-β coordinate system, the physical quantities of current and voltage are given a spatial orientation, which is referred to as space vectors. With the help of the now spatial alignment, they can simply summarize the phase quantities, such as the current and the voltage of the respective motor phase by vector addition to a size. The now calculated size can be represented in the α-β coordinate system. With this representation, the stator field of the induction machine can be easily controlled or controlled. This control method is also referred to as field-oriented control (= FOR) or field-oriented control (= FOS).

When using a rotating field machine as a traction drive of a vehicle, it can happen, especially when starting on the mountain from a standing or when rolling backwards, that the stator field is stationary or at least almost stationary. As a result, a direct current flows via individual power semiconductor switches of the inverter. As a result, the power semiconductor switches in the inverter are extremely unevenly thermally stressed. In the extreme case, this can lead to the destruction of the affected current-carrying semiconductor conductors, and thus to the failure or massive disturbances of the inverter.

From the prior art, such as the DE 10 2013 212 054 A1 or the DE 10 2010 061 897 A1 , It is therefore known to operate the inverter so that the stator field has a frequency not equal to zero or that the space vector is moved between two limits. This distributes the electrical current to the power semiconductor switches of the inverter. The thermal load of individual power semiconductor switches is thus reduced significantly. However, by the vibration of the space hand, the components involved in the system, so for example in the inverter or in the downstream vehicle driveline, be stimulated to noise.

The object of the invention is therefore to improve the state of the art in this regard.

This task is solved by the features of the skin spokes. Preferred embodiments are the dependent claims.

Accordingly, a method for operating a rotating field machine by means of an inverter at a standstill or when starting a rotor of the induction machine is proposed. In the context of the method, a space vector for an electric current or an electric voltage for generating a magnetic stator field is oscillatingly moved in order to guide the electric current flowing through the inverter via alternating power semiconductor switches of the inverter. This reduces the thermal load on the individual power semiconductor switches of the inverter. It is provided that the oscillation of the space vector is a noise oscillation. This reduces the vibration excitation of the components of the system. The noise level is thereby lowered.

The proposed control unit is used for actuating power semiconductor switch of an inverter for operating a rotating field machine. The control unit has a determination module, designed to determine the space vector for the electric current or the voltage for generating the magnetic stator field of the induction machine. This can be done, for example, on the basis of a setpoint torque which is given to the control unit and which is the Rotary field machine to make done. Thus, the space vector is then used to provide the desired torque through the induction machine. The controller also has a noise module designed to generate noise. In addition, it has a modulation module, designed to aufzumodulieren the space vector at a standstill or start-up of a rotor of the induction machine the noise oscillation. The control unit is used in particular for controlling or regulating the inverter or the induction machine. The control unit is then used in particular for field-oriented control or regulation of the induction machine.

The proposed vehicle drive train has an induction machine as a traction drive or actuator and an inverter for operating the induction machine and the above-explained and proposed control unit for actuating the power semiconductor switch of the inverter. The induction machine serves as a traction drive, ie for propulsion of the associated vehicle, d. H. for providing a drive torque. For this purpose, it is mechanically coupled, for example, with one or more vehicle wheels. The induction machine as actuator serves to actuate a component of the vehicle drive train, for example a switching element, such as a clutch or a brake, or another component to be placed in the drive train.

The proposed concept therefore provides that the oscillation of the space vector is not always the same, ie. H. has a fixed frequency, but takes place in the form of a noise. Such noise has a wide non-specific frequency spectrum and possibly amplitude spectrum. As a result, it is not or significantly less often to a stimulation of components in the system, whereby the noise is reduced. Preferably, the vibration is so fast that no noticeable torque vibrations or the like occur in the induction machine, d. H. the movable masses (rotor, etc.) of the induction machine suppress the vibrations sufficiently strong.

The inverter is used to convert a direct current from a direct current source, such as a battery, into an alternating current or quasi alternating current at phases of the induction machine (motor operation) and possibly back (generator operation). For this purpose, it has the power semiconductor switches, which are driven, for example, by a driver circuit. In the inverter, the power semiconductor switches are designed, for example, as a B6 bridge circuit. By a pulse width modulated operation (on / off) of the power semiconductor switch, the space pointer can be made.

The placement of the space pointer takes place in particular when there is a request to generate a torque, that is to say a drive or braking torque, of the induction machine. In the context of the method, it is then in particular recognized that a torque is to be set, for example a specific desired torque. The space vector is then used in particular to provide the requested torque or desired torque through the induction machine. In the context of the method, it is then in particular also recognized that the rotor is standing still or is starting to move, that is, it is starting to rotate. The rotational frequency of the rotor during startup is in particular less than 5 Hz, less than 1 Hz or equal to zero (= standstill).

Preferably, the vibration of the space vector is implemented as white noise. As a result, a noise can be suppressed particularly effective. By white noise is meant in particular a noise with a constant power density spectrum in a certain frequency range. The frequency range is then specified in particular. It is determined, for example, experimentally or analytically.

The oscillation thus preferably has a predetermined oscillation width. Thus, a boundary is set, within which the noise takes place. This is done in particular by specifying an upper limit frequency, which must not exceed the noise and a lower limit frequency, which may not be less than the noise. Thus disturbing frequency ranges can be hidden. Preferably, the oscillation width is specified in the stator-fixed α-β coordinate system or in the rotor or rotor flux-fixed d-q coordinate system of the induction machine. As a result, no cumbersome conversion of the oscillation width is required, since the space vector is normally predefined in the α-β or d-q coordinate system when using a field-oriented control or field-oriented control, as is also preferred in the present case.

The oscillation preferably corresponds in time average to a required setpoint space vector for the current or the voltage for generating the magnetic stator field. The desired room vector can correspond, for example, to the required setpoint torque, ie serve to provide the required setpoint torque by the induction machine. In addition, the oscillation width of the oscillation is preferably a function of the starting fundamental frequency of the induction machine. It is then dependent on the Startor basic frequency, ie from the Startorgrundfrequenz the respective oscillation width is determined calculated, for example. As Startorgrundfrequenz is to be understood in particular the stator current base frequency. This can be taken, for example, from the field-oriented control or via a measuring device, such as beisplelswelse a phase-locked loop (PLL = phase locked loop), are measured.

Preferably, a required setpoint space vector for the electric current or the electrical voltage for generating the magnetic stator field, in particular for providing the required setpoint torque, modulates a noise signal. As a result, the mentioned noise oscillation of the space pointer is formed. The actual room pointer is thus composed of the desired room pointer (for setting the desired torque) and the modulated noise signal. For example, the noise signal is modulated additively or subtractively.

In the following, the invention of figures will be explained in more detail, from which further preferred embodiments and features of the invention can be removed. The figures show in schematic representation:

1 an electric drive system with a rotating field machine,

2 a space vector in a uvw and α-β coordinate system,

3 an oscillating space vector in an α-β coordinate system.

1 shows a typical structure of a field-oriented control (FOR) or field-oriented control (FOS) running drive system with a rotating field machine 1 , For example, a synchronous or asynchronous machine The drive system, a predetermined target torque T is supplied. This torque T is intended by the induction machine 1 are output, ie the induction machine 1 should deliver this target torque T at its output shaft, for example, to drive a vehicle or a machine with this target torque T. The target torque T can be predetermined, for example, by an operator of the drive system, such as a vehicle driver or a machine operator. It can also be requested by a higher-level control or regulation.

It is a discovery module 2 provided, which determines from the target torque T a corresponding d-current and q-current i _d , i _g . If a regulation (FOR) is present, actual values of the d-current and q-current can be used for this purpose i * / d, i * / q be added. If there is a control (FOS), the addition of the actual values is no longer necessary i * / d, i * / q , The d-current and q-current i * / d, i * / q or i _d , i _q lies in a rotor flux-fixed or rotor-fixed dq coordinate system of the induction machine 1 in front. The d-current and q-current i * / d, i * / q or i _d , i _q form the vectorial components of a current space vector in a dq coordinate system. The dq coordinate system thus rotates with respect to the stator of the induction machine 1 when the stator field or the rotor of the induction machine 1 is turned. It stands with respect to the rotor of the induction machine 1 or the magnetic rotor flux.

The currents i _d , i _q become a control module 3 for the field-oriented control or control of the induction machine 1 fed. From this, it determines the decoupled currents i _α , i _β in a stator-fixed α-β coordinate system and feeds them to a PWM generator 4 to (PWM = pulse width modulation, pulse width modulated). This generates from the currents i _α , i _β, the PWM signals PWM1, PWM2, PWM3 for the pulse width modulated control of power semiconductors of an inverter 5 , The α-current i _α and the β-current i _β form the vectorial components of a current space vector in the α-β coordinate system. The α-β coordinate system is thus fixed with respect to the stator of the induction machine 1 ,

According to the currents i _α , i _β and i _d , i _q thereby becomes the inverter 5 by which the PWM signals PWM1, PWM2, PWM3 are operated. In detail, the power semiconductor switches in the inverter 5 actuated (switched on and off), so that the required currents i _d , i _q or i _α , i _β set. The inverter 5 is coupled on the input side with a DC power source, such as a battery or a DC generator, and draws therefrom in an engine operation of electrical energy for operating the induction machine 1 , The output side is the inverter 5 with the phases U, V, W of the induction machine 1 coupled and leads hereby the phase currents i _u , i _v , i _w , which result from the PWM signals PWM1, PWM2, PWM3. In a generator operation is also electrical energy from the induction machine 1 over the inverter 5 traceable to the DC power source.

The modules 2 . 3 . 4 especially in a control unit 6 (Dashed frame) spatially be housed together, for example in the form of an integrated circuit. The control unit 6 For example, from the inverter 5 be physically separated. The control unit 6 can also be on the inverter 5 be placed on, that is arranged or integrated therein. So can the controller 6 and the inverter 5 just share a common cooling circuit. The control unit 6 So serves to actuate the power semiconductor switch of the inverter 5 ,

Problems can, as explained above, then arise when, on the one hand, the induction machine 1 On the other hand, the rotor or the stator field generated by the phase currents i _u , i _v , i _w or an associated current or voltage space vector is stationary or at least nearly stationary. This has the consequence that the phase currents i _u , i _v , i _{w are} quasi DC currents and thus via individual power semiconductor switches of the inverter 5 flow. As a result, these power semiconductor switches in the inverter 5 are extremely unevenly thermally stressed.

This problem is solved in this case by the fact that the space vector, which results from the currents i _u , i _v , i _w or i _α , i _β and i _d , i _q (ultimately always the same space vector in different Coordinate systems of the rotary field machine 1 , as in 2 shown by way of example) is oscillated. As a result, the phase currents i _u , i _v , i _w via changing power semiconductor switches of the inverter 5 guided. In order to avoid suggestions by this vibration, while the vibration of the space vector is designed as a noise, preferably as white noise.

2 shows an example of a current or voltage space pointer 204 . 205 for generating a magnetic stator field in the induction machine 1 and thus a torque through the induction machine 1 , The space vector is on the one hand in a uvw coordinate system before (left side of 2 ), then it has the reference number 204 on, and in an α-β coordinate system (right side of 2 ), then it has the reference number 205 on.

In the uvw coordinate system, one of the currents i _u , i _v , i _{w flows} through the respective phase U, V, W of the induction machine 1 , They clamp together the space hand 204 in the uvw coordinate system, ie by vector addition of the currents i _u , i _v , i _w , i _w , this results in the space vector 204 ,

The space pointer 204 can be simply transferred from the uvw coordinate system to the a-β coordinate system, where it is the reference numeral 205 having. Accordingly, it can also be simply transferred from the α-β coordinate system to the uvw coordinate system. In the α-β coordinate system, the space vector becomes 205 spanned by the currents i _α , i _β , ie by vector addition of the currents i _α , i _β results from the space vector 205 , Therefore, through the in 1 shown system or control unit 6 the required phase currents i _u , i _v , i _{w are} determined simply from the currents i _α , i _β .

In 3 is a current / voltage space pointer 301 represented in the α-β coordinate system. This is used to enable the induction machine 1 provides a required setpoint torque. The space pointer 301 can therefore also be referred to as the desired room pointer (for the setpoint torque). The determination of the space pointer 301 is preferably carried out in a determination module of in 1 shown control unit 6 , The space pointer 301 would be fixed to provide the desired torque, ie not turn. This is due, for example, to the fact that the rotor of the induction machine 1 not yet turning, especially because he is blocked or because he just starts to turn (induction machine starts). Then, as explained above, quasi DC currents in individual power semiconductor switch of the inverter 5 result.

It is therefore provided that the actually asked space vector is moved oscillatingly, that is, around the actual desired space vector 301 around is moved around. The vibration is carried out as noise and has a predetermined oscillation width 302 on. This is particularly in the stator fixed α-β coordinate system of the induction machine 1 specified. In terms of time, the oscillation, ie the actual room pointer, corresponds to the required set room pointer 301 , The oscillation width 302 is a function of the starting fundamental frequency of the rotary field machine 1 ie it is determined from this.

The oscillation is achieved in that the actually desired target space vector 301 a noise oscillation is superimposed, that is aufmoduliert. The noise oscillation is in particular in a noise module of the controller 6 based on the oscillation width 302 generated. Subsequently, this is in a modulation module of the control unit 6 the desired room pointer 301 modulated.

LIST OF REFERENCE NUMBERS

1

Induction machine

2

determination module

3

Control module, control module

4

PWM generator

5

inverter

6

control unit

204

Current or voltage space vector in a uvw coordinate system

205, 301

Current or voltage space vector in an α-β coordinate system

302

vibration width

i

electrical current

i _d , i * / d

Current component in d-direction of a d-q-coordinate system (= d-current)

i _q , i * / q

Current component in q-direction of a d-q-coordinate system (= q-current)

i _α

Current component in α-direction of an α-β-coordinate system (= α-current)

i _β

Current component in the β-direction of an α-β-coordinate system (= β-current)

i _u

Current component in the u direction of a uvw coordinate system (= u current)

i _v

Current component in the v-direction of a uvw coordinate system (= v-current)

i _w

Current component in w-direction of a uvw coordinate system (= w-current)

PWM1

PWM signal

PWM 2

PWM signal

PWM3

PWM signal

AND MANY MORE

phase

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

• DE 102013212054 A1 [0005]
• DE 102010061897 A1 [0005]

Claims (9)

Method for operating a rotary field machine ( 1 ) by means of an inverter ( 5 ) at a standstill or starting a rotor of the induction machine ( 1 ), where a space pointer ( 204 . 205 . 301 ) for an electric current (i _α , i _β ; i _d , i _q ) or an electric voltage for generating a magnetic stator field is vibrated in order to pass through the inverter ( 5 ) thereby flowing electric current (i _u , i _v , i _w ) via alternating power semiconductor switch of the inverter ( 5 ), characterized in that the oscillation of the space vector ( 204 . 205 . 301 ) is a noise vibration. The method of claim 1, wherein the vibration is implemented as white noise. Method according to claim 1 or 2, wherein the oscillation has a predetermined oscillation width ( 302 ) having. Method according to claim 3, wherein the oscillation width ( 302 ) in a stator-fixed α-β coordinate system or in a rotor or rotor flux-proof dq coordinate system of the induction machine ( 1 ) is given. A method according to claim 3 or 4, wherein the oscillation in the time average a required desired space pointer ( 204 . 205 . 301 ) for the electric current (i _α , i _β ; i _d , i _q ) or the electric voltage for generating the magnetic stator field. Method according to one of claims 3 to 5, wherein the oscillation width ( 302 ) of the vibration is a function of the starting fundamental frequency of the induction machine ( 1 ). Method according to one of the preceding claims, wherein a required desired space vector ( 204 . 205 . 301 ) for the electric current (i _α , i _β ; i _d , i _q ) or the electric voltage for generating the magnetic stator field, a noise signal is modulated and thereby the noise oscillation of the space vector ( 204 . 205 . 301 ) is formed. Control unit ( 6 ) for actuating power semiconductor switches of an inverter ( 5 ) for an induction machine ( 1 ), with a determination module to create a space pointer ( 204 . 205 . 301 ) for the electric current (i _α , i _β ; i _d , i _q ) or the electric voltage for generating the magnetic stator field of the induction machine ( 1 ), characterized by a noise module for generating a noise oscillation, and a modulation module for detecting at a standstill or start-up of a rotor of the induction machine ( 1 ) the space hand ( 204 . 205 . 301 ) to modulate the noise oscillation. Vehicle drive train with a rotating field machine ( 1 ) as a traction drive or actuator and with an inverter ( 5 ) for operating the induction machine ( 1 ) as well as with a control unit ( 6 ) for actuating power semiconductor switch of the inverter ( 5 ), characterized in that the control unit ( 6 ) is executed according to claim 8.

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