WO2013023803A1

WO2013023803A1 - Actuation method for three-phase machine and three-phase machine device

Info

Publication number: WO2013023803A1
Application number: PCT/EP2012/061073
Authority: WO
Inventors: Wei Hu
Original assignee: Robert Bosch Gmbh
Priority date: 2011-08-18
Filing date: 2012-06-12
Publication date: 2013-02-21
Also published as: DE102011081216A1

Abstract

The invention relates to a method for actuating an electric three-phase machine (14), in particular a synchronous machine (14), the electric three-phase machine (14) being supplied with current in a multiphase manner by means of an inverter (10), the inverter (10) being actuated in a first rotational speed range (46) of the three-phase machine (14) in a first actuation mode and in a second rotational speed range (48) in a second actuation mode, the inverter (10) being actuated in the first actuation mode by means of space vector modulation and being actuated in the second actuation mode by means of block commutation, and the actuation modes being alternated according to the rotational speed (n) of the three-phase machine (14).

Description

Description title

Three-phase machine driving method and device

The present invention relates to a method for controlling a three-phase electrical machine, in particular a synchronous machine, wherein the electric three-phase machine is energized polyphase by means of an inverter, wherein the inverter is driven in a first speed range of the three-phase machine in a first drive mode and in a second speed range in a second Control mode is controlled. Furthermore, the present invention relates to an apparatus for driving a three-phase electrical machine, in particular a synchronous machine, with an inverter having a plurality of power semiconductor switches to energize the electric machine polyphase and with a control unit that drives the inverter.

Finally, the present invention relates to a motor vehicle drive train having at least one electric rotary machine for providing drive power and having a device for driving the electric machine of the above

described type.

State of the art

In the technical field of electrical machines are different

Driving method known. Currently, the method of space vector modulation is preferably used for three-phase machines. In this

Driving method is a continuously rotating space pointer through

successive circuit formed by six basic voltage space pointers. To the continuous rotation of the space pointer and thus a sinusoidal

To achieve commutation, the fundamental voltage space vector are switched pulse width modulated, so that in the mean value a sinusoidal

Drive voltage is generated. To increase the voltage utilization of the space vector modulation usually the overmodulation is used, in which the amount of the resulting generated

Space vector varies and at the angular positions of the six

Basic voltage space pointer corresponds to the amount of this. This results in a correspondingly fluctuating torque of the electric machine. Furthermore, it is disadvantageous in the overmodulation method that by the non-sinusoidal

Control signal disturbing harmonics arise. In the known driving methods, the electrical machines are controlled by means of space vector modulation and in special cases by means of overmodulation. In principle, it is assumed that the sampling frequency or the

Modulation frequency is much larger than the electrical frequency of the

Drive signal. If the electrical frequency is increased by increasing the speed of the machine and approaches the sampling frequency, the

Raumzeigermodulations- or overmodulation operation because of strong distortion of the drive signal not realized or not operated efficiently.

Furthermore, a drive method is known from EP 1 441 436 A2, in which an electric machine is selectively controlled by means of pulse width modulation or block commutation.

Overall, it is disadvantageous in the known driving method that at high speeds and correspondingly high electrical frequencies, which are in the range of the sampling frequency, an energy-efficient driving is not or only possible to a limited extent.

DISCLOSURE OF THE INVENTION According to the invention, therefore, a method for driving an electrical

Three-phase machine, in particular a synchronous machine provided, wherein the electric three-phase machine is energized by a multi-phase inverter, wherein the inverter is driven in a first speed range of the three-phase machine in a first drive mode and in a second

Speed range is driven in a second drive mode, wherein the

Inverter in the first control mode by means of space vector modulation and in the second drive mode is controlled by block commutation, and wherein the drive modes are changed according to a rotational speed of the three-phase machine accordingly. Furthermore, therefore, according to the invention, a device for driving a

A three-phase machine, in particular a synchronous machine, provided with an inverter having a plurality of power semiconductor switches to energize the three-phase machine polyphase and with a control unit that drives the inverter, wherein the control unit is adapted to carry out the method described above.

Finally, according to the invention, a motor vehicle drive train is provided with a three-phase machine for providing drive power and with a device for driving the three-phase machine of the type described above.

Advantages of the invention

By the present invention, a method can be provided by which a three-phase machine is optimally controlled in different speed ranges and thus can be operated efficiently in different speed ranges. Furthermore, the three-phase machine can thereby be optimally operated in a speed range in which the electrical frequency of the modulation frequency of

Space vector modulation approximates. By switching or changing the drive modes, the three-phase machine can always be optimally driven in the entire operating range, especially when the three-phase machine is operated at a high speed and a high electrical frequency associated therewith.

The inverter is in the first control mode using

Controlled space vector modulation in order to provide the three-phase machine in particular a substantially sinusoidal strand voltage and thereby energize the three-phase machine accordingly. The inverter will be in the second

Drive mode driven by block commutation to provide the three-phase machine, a substantially rectangular string voltage and the

Power three-phase machine accordingly. Of particular advantage is when the drive modes are changed directly. In other words, in a transition between the drive modes, the three-phase machine is not driven in another drive mode, in particular not by means of overmodulation.

As a result, the control of the three-phase machine is particularly simple and feasible with little effort.

It is of particular advantage if the rotational speeds of the first rotational speed range are smaller than the rotational speeds of the second rotational speed range.

As a result, the three-phase machine can be driven particularly effectively and optimally at high speeds at which the electrical frequency approaches the space vector modulation frequency.

It is of particular advantage when the drive modes are changed in a predefined speed transition range between the first and the second speed range. As a result, the control modes can be changed continuously, without the output torque changes abruptly.

It is preferred if the three-phase machine is controlled in the speed transition range by means of a combination of the two drive modes.

As a result, overshoot or instability of the control loop can be prevented.

It is of particular advantage when in the speed transition region of the

Inverter is controlled by means of a Übergangsansteuersignals whose

Duty cycle is varied depending on the speed.

This can be realized with technically in particular control technology simple means and effectively a continuous transition from the first drive mode to the second drive mode. It is preferred if the duty cycle of the transition control signal is formed by a combination of duty cycles corresponding to the two drive modes. As a result, the transition between the two modes can be carried out particularly easily and a steady transition of the torque can be achieved.

It is further preferred if the duty cycles of the two drive modes are weighted as a function of the rotational speed.

As a result, the transition can be carried out particularly accurately and precisely.

It is still preferred if the duty cycles of the two

Control modes are weighted linearly depending on the speed.

This allows a technically easy to implement control in the

Transition speed range can be provided.

It is further preferred if the duty cycles of the two drive modes are weighted in opposite directions.

This can be a continuous and steady transition between the

Control modes are realized. It is further preferred if the three-phase machine in the

Speed transition range by means of a pulsed pulse width modulated

Block commutation voltage is driven, wherein a duty cycle or the duty cycle of the individual pulses is varied within an electrical period. Thereby, the three-phase machine can be operated effectively in the transition region, wherein the output torque has a steady course and accordingly torque fluctuations are avoided.

It is understood that the features, properties, advantages of the method according to the invention also apply correspondingly to the device according to the invention or are applicable. Brief description of the drawings

Fig. 1 shows in schematic form an inverter for driving a rotary electric machine;

Fig. 2 shows a complex vector diagram for explaining the

Space vector modulation method for driving an inverter of a

Three-phase machine;

Fig. 3 shows in schematic form the time course of three different drive voltages;

Fig. 4 shows in schematic form a transition between the space vector modulation and the block mode as a function of the rotational speed;

Fig. 5 shows the drive signals of the two drive modes and a combination of the drive signals; 6a-d show the time course of the duty cycles of the three drive modes in the time domain of an electrical period and the resulting phase voltage in

Time range of an electrical period of the three-phase machine.

Embodiments of the invention

In Fig. 1, an inverter for driving an electric machine is shown schematically and generally designated 10.

The inverter 10 is connected to a DC voltage source 12 and serves to energize a three-phase electrical machine 14 three-phase. The inverter 10 has three half bridges 16, 18, 20, which are connected in parallel to the DC voltage source 12 and each having two switches S. Between the switches S a Halbbrückenabgriff 22 is formed, each of which is connected to a phase conductor of the electric machine 14. By alternately opening and closing the switch S is between the

Phase conductors each applied a drive voltage UU, UV, UW, so that in each case a phase current IU, IV, IW sets, which drives the electric machine 14.

The inverter 10 is preferably formed by means of semiconductor switches S, wherein usually in parallel to the half-conductor switches S in each case a freewheeling diode not shown here is connected. The switches S of the inverter 10 are alternately opened and closed by means of a control unit 23, shown schematically, to provide the phase voltages UU, UV, UW with a specific course and to energize the electric machine 14 with the phase currents IU, IV, IW. 2, a complex phasor diagram for explaining the space vector modulation for driving the electric machine 14 is shown and generally designated 30.

In the vector diagram 30 are two voltage vector UA, UB with a

Drive angle od of the electric machine 14 is shown. In the vector diagram 30 six ground voltage pointers U1, U2, U3, U4, U5, U6 are also shown, which result when certain switches S of the inverter 10 are closed and the electric machine 14 is driven accordingly. Thus, for example, the ground voltage pointer U1 results when the switches SU1, SVO and SWO are closed and the other switches S of the inverter are open. In Fig. 2 this is represented by [100]. This is an indication that only the first switch SU1 is closed by the switches SU1, SV1 and SW1. For the efficient operation of the electrical machine and to avoid a short circuit, this inevitably results in the switch position for the switches SUO, SVO and SWO. SVO and SWO are closed. Accordingly, the ground voltage vector U2 [1 10] results when the switches SU1, SV1 and SWO are closed and the remaining switches S of the

Inverter are open. In order to set the voltage vector UA, which in this example has the drive angle od between the ground voltage vectors U1 and U2, this is achieved by alternately driving the inverter 10

realized in accordance with the base voltage vector U1 and the ground voltage vector U2. The two ground voltage vectors U 1, U 2 are alternately set with a predefined switching frequency, so that at the same frequency and the same Duty cycle of the ground voltage pointer U1, U2 exactly the voltage vector UA results. If a voltage vector has to be set with a larger control angle oc, the switch-on duration of the basic voltage vector U2 is correspondingly extended and the on-time of the basic voltage vector U1 is shortened.

Thus, by clocked driving the switch S of the inverter 10, the voltage space pointer UA can be realized with an arbitrary drive angle oc.

If the voltage vector UB is to be set with a smaller amount than the voltage vector UA, a zero voltage vector U0, U7 is accordingly set in which the switches S are opened on one of the two sides of the inverter 10. Accordingly, the voltage vector UB by a combination of

Base voltage pointer U1 and U2 and one of the zero voltage pointer U0, U7 be realized.

In Fig. 2, a unit circle 32 is shown in the vector diagram 30, which corresponds to the length of the voltage vector UA. If the voltage space vector UA is set to be uniformly rotating, a sinusoidal drive voltage UU, UV, UW is output and the electric machine 14 is driven accordingly.

In Fig. 2, a hexagon 34 is shown, which is spanned by the six ground voltage vectors U1 to U6. In a particular embodiment of the

Space vector modulation method, the inverter 10 is driven such that an amount of the voltage space vector UA varies and that according to the hexagon 34. This creates a drive voltage UU, UV, UW, whose flanks are formed sinusoidal and whose central portion is block-shaped as explained in more detail below becomes. This embodiment of space vector modulation is also referred to as overmodulation. A disadvantage of the overmodulation is that 14 harmonics occur in the electric machine, which can cause an oscillating or unstable behavior.

3 shows three different courses of the drive voltage UU, UV, UW for three different drive modes over an electrical period. FIG. 3 shows a sinusoidal drive voltage 36 over an electrical period, which corresponds to a drive voltage by means of space vector modulation. If the

Inverter 10 is increasingly operated in overmodulation, move Flanks 38 of the sine curve 36 to the outside, as indicated by an arrow 40. This results in an overmodulation drive signal as shown at 42. The overmodulation drive signal 42 has sinusoidal edges 38 and a block-shaped center portion 44.

In Fig. 3, a drive voltage signal 45 is further shown, the one

Control by block commutation corresponds. In this case, in a first half cycle of the electrical period, a positive voltage is applied between the phase conductors of the electric machine 14 and applied in a second half cycle of the electrical period, a negative DC voltage to the phase conductors.

The control medium block commutation is particularly well suited for high

Speeds in which the electrical period is near a drive frequency of the space vector modulation method, the voltage utilization in the

Block Kommutierungsbetrieb is optimal and the maximum achievable performance can be achieved.

FIG. 4 shows a combination of two drive methods and a corresponding transition range as a function of a rotational speed n of the three-phase machine 40. In a first speed range 46 below a first speed n1, the electric machine 14 is controlled by means of space vector modulation. In a second speed range 48 above a second speed n2, the electric machine 14 is driven by block commutation. In one

Speed transition region 50 between the first speed n1 and the second speed n2, the electric machine 14 is driven in a combination operation, which is formed by a combination of the space vector modulation and the block commutation.

FIG. 4 shows two weighting factors 52, 54 for space vector modulation and for block commutation for the three speed ranges 46, 48, 50. The

Control signals, the space vector modulation or block commutation

are weighted in the speed ranges 46, 48, 50 corresponding to the weighting factors 52, 54 shown in FIG. 4, to indicate a change of the driving methods and a corresponding transition in the

Speed transition region 50 to realize. Accordingly, the weighting factor 52 of the space vector modulation in the first speed range 46 is 100% and the weighting factor 54 of the block commutation is 0%. Conversely, the weighting tractor 54 is the Block commutation in the second speed range 48 100% and the weighting factor 52 of the space vector modulation 0%. In the speed transition region 50, as the rotational speed n of the electric machine 14 increases, the weighting factor 52 is linearly reduced from 100% to 0% and, at the same time, the weighting factor 54 of the block commutation is linearly increased from 0% to 100%. Thereby, a linear continuous transition from the space vector modulation in the block commutation operation can be realized. Of the

Correspondence between the weighting factors 52, 54 is correspondingly gr = 1-gb, where gr is the weighting factor 52 of the space vector modulation and gb is the weighting factor 54 of the block commutation.

The weighting factors 52, 54 are preferably used as a factor of a space vector modulation on time t1 and a block commutation on time t2 to calculate a resulting combination on time t3. Accordingly, a duty ratio t1 / T, t2 / T, t3 / T can be determined, where T is the period of the

pulse width modulated signal forms.

The calculation of the resulting combination switch-on time t3 takes place according to the formula t3 = t1 - (1-g) + (T-t2) -g, where g = gb = (n-n1) / (n2-n1), where n is the speed of the electric machine 14, g is a uniform weighting factor corresponding to the weighting factor 54 gb for block commutation, and T is a

Period of the pulse width modulation period is.

In Fig. 5 are three control signals 56, 58, 60 and the corresponding on time t1, t2, t3 for space vector modulation, block operation and the combination of the two

Control method within a pulse width modulation period T shown schematically. The drive signal of the space vector modulation 56 has a pulse in the middle of a pulse width modulation period T of the width t1. The drive signal 56 accordingly has a switch-on time within this pulse width modulation period T of the duration t1 and a duty ratio t1 / T. In accordance with the basic method of space vector modulation, the duty cycle t1 varies from one to the next of the pulse width modulation periods T.

FIG. 5 also shows the drive signal for the block commutation 58 within this pulse width modulation period T. In this case, the corresponding control signal 58 changes once from the value 0 to the value 1 and indeed after a period t2 within this pulse width modulation period T. The control signal for the

Block commutation 58 remains constant for several subsequent pulse width modulation periods T and is lowered to zero when the corresponding block drive pulse is completed within that electrical period. The duty cycle is t2 / T.

The combination drive signal 60 has a single pulse within the pulse width modulation period T, which is located in the middle of the period and has a pulse duration t3. The duty cycle is according to t3 / T. The on-time t2 in the block mode is therefore constant within one electrical period, whereas the on-time t1 of the space vector modulation varies from one to the next period T. Consequently, the pulse duration t3 of the

Combination drive signal 60 within one electrical period. In FIGS. 6a-c, the normalized on-time and the duty cycle, respectively, are normalized to 1 over approximately one electrical period of the electric machine 14 for space vector modulation, block commutation, and combination operation.

Correspondingly, in a marked start region 62 of a drive block 64 within the illustrated electrical period in FIG. 6a the duty cycle t1 / T is shown, in FIG. 6b the duty cycle t2 / T and in FIG. 6c the duty cycle t3 / T. The

On time t1 increases in space vector modulation within an electrical period, as shown in Fig. 6a, until the duty cycle is nearly 1.

Accordingly, at the end 66 of the drive block 64, the duty cycle gradually decreases. In Fig. 6b, the drive block 64 has only one stage to the beginning 62 and one stage to the end 66, since the drive signal 58 is changed to 1 only within a specific pulse width modulation period T and is lowered from 1 to 0 within a further pulse width modulation period T.

The course of the switch-on period for the combination mode in FIG. 6c is based accordingly on a combination of the two switch-on time diagrams from FIGS. 6a and 6b. FIG. 6d shows the course of a drive voltage over approximately one electrical period, which corresponds to one of the drive voltages UU, UV, UW from FIG. The drive voltage UU, UV, UW accordingly changes between a negative value -UDC / 2 and a positive value + UDC / 2. According to the resulting switch-on time t3, the drive voltage at the beginning of the drive block 64 is pulsed with a small on-time or a low duty cycle, the

On time t3 increases in the course of Kommutierungsblocks 64 and is equal to 1 in a central portion 68, so that the drive voltage UU, UV, UW is set to a constant value + UDC / 2 constant. Accordingly, the on-time t3 at the beginning 62 of the drive block 64 continuously increases and ends at the end 66 of FIG

Control block 64 continuously from.

As a result, in the speed transition region 50, the electric machine 14 can be controlled in a combination of the space vector modulation and the block commutation.

Claims

Claims 1. Method for controlling an electric three-phase machine (14), in particular a synchronous machine (14), wherein the electric three-phase machine (14) is energized in multiple phases by means of an inverter (10), wherein the inverter (10) in a first speed range (46) of the three-phase machine ( 14) in a first

Drive mode is controlled and in a second speed range (48) is driven in a second drive mode, wherein the inverter (10) is driven in the first drive mode by space vector modulation and is driven in the second drive mode by means of block commutation, and wherein the drive modes in response to a speed (n) the three-phase machine (14) are changed accordingly.

2. The method of claim 1, wherein the drive modes are changed directly.

3. The method according to claim 1 or 2, wherein the rotational speeds (n) of the first

Speed range (46) are smaller than the rotational speeds (n) of the second speed range (48).

4. The method according to any one of claims 1 to 3, wherein in a predefined

Speed transition range (50) between the first speed range (46) and the second speed range (48), the drive modes are changed.

5. The method according to any one of claims 1 to 4, wherein the three-phase machine (14) in the speed change region (50) by means of a combination of the two

Control modes is controlled.

6. The method according to any one of claims 1 to 5, wherein in the speed transition region (50) of the inverter (10) is driven by means of a Übergangsansteuersignals (60) whose duty cycle is varied in dependence of the rotational speed (n).

7. The method of claim 6, wherein the duty cycle of the transition drive signal (60) by a combination of duty cycles corresponding to the two

Ansteuermodi is formed.

8. The method of claim 7, wherein the duty cycles of the two drive modes depending on the speed (n) are weighted.

9. The method of claim 7 or 8, wherein the duty cycles of the two

Control modes depending on the speed (n) are weighted linearly.

10. The method according to any one of claims 7 to 9, wherein the duty cycles of the two drive modes are weighted in opposite directions.

1 1. Method according to one of claims 1 to 10, wherein the three-phase machine (14) is driven in the speed transition region (50) by means of a pulsed pulse width modulated block commutation voltage, wherein the duty cycle of the individual pulses is varied within an electrical period.

12. An apparatus for driving a three-phase electrical machine (14), in particular a synchronous machine (14), comprising an inverter (10) having a plurality of power semiconductor switches (S) to energize the three-phase machine (14) polyphase, and with a control unit (23), which controls the inverter (10), wherein the control unit (23) is adapted to carry out the method according to one of claims 1 to 1 1.

13. Kraftfahrezugantriebsstrang with at least one three-phase machine (14) for providing drive power and with a device for driving the

Three-phase machine (14) according to claim 12.