DE102012210665A1 - Method for controlling inverter mounted in drive train of motor vehicle, by space vector modulation, involves selecting one of sequences depending on specific time period for driving the inverter according to predefined load set point - Google Patents

Abstract

The method involves arranging inverter (10) with several controllable switches (SHA-SHC), to provide polyphase electric current to electrical machine (14). The inverter is controlled in predefined sequences of different switching states of the switches, to provide voltage in the form of voltage space vector. One of sequences is selected depending on specific time period for driving the inverter according to predefined load set point. Independent claims are included for the following: (1) device for controlling inverter; and (2) drive train of motor vehicle.

Description

The present invention relates to a method for controlling an inverter by means of space vector modulation, in particular for driving an electrical machine, wherein the inverter has a plurality of controllable switches and which is adapted to provide a multi-phase electric current, in particular around the electric machine polyphase with electric current wherein the inverter is driven to establish a plurality of successive different switching states of the switches and to provide a voltage in the form of a corresponding voltage space vector.

Furthermore, the present invention relates to an apparatus for driving an inverter, in particular for driving an electrical machine, wherein the inverter comprises a plurality of controllable switches which are connected to provide a multi-phase electric current, with a control unit which is adapted to the To drive inverters such that the inverter takes a plurality of successive different switching states of the switches to provide a corresponding voltage space pointer.

Finally, the present invention relates to a motor vehicle drive train with at least one electric machine for providing drive power, an inverter for driving the electric machine and with a device for driving the inverter of the type described above.

State of the art

In the technical field of three-phase current consumers in general and three-phase electrical machines in particular, different driving methods are known. Currently, the method of space vector modulation for controlling the three-phase current consumer is currently preferred. In this driving method, a space pointer is formed by sequentially setting eight ground voltage hands. In order to provide the string voltage, the ground voltage phasors are switched pulse width modulated, so that a corresponding drive voltage is generated in the mean value.

In the known driving method, the electrical loads are controlled by means of an inverter with power semiconductor switches. The setting of the eight ground voltage pointer for generating the voltage space pointer is realized by alternately turning on and off certain power semiconductor switches of the inverter. At very low rotational speeds of the space hand or, if the three-phase load is an electrical machine, at low speeds of the driven electrical machines, individual power semiconductor switches are very common or switched on for a very long time and thus thermally loaded by a very long or very frequently flowing electric current. Therefore, the power semiconductor switches must be designed for very long turn-on times and for very large currents, whereby the inverter is generally technically complex.

In order to counteract one, in particular thermal, overloading of the power semiconductor switches is in the WO 2010 / 000548A2 proposed to omit one of two de-energized switching states in certain pulse width modulation periods in order to reduce the switching losses of the power semiconductor switches.

The disadvantage here is that one, in particular thermal, load distribution of the power semiconductor switch can not be targeted and thus peak loads of individual power semiconductor switch must be taken into account.

Disclosure of the invention

According to the invention, therefore, a method is provided for driving an inverter by means of space vector modulation of a type mentioned, in which the inverter is controllable by means of two predefined sequences of switching states having different switch-on times of the switching states, wherein for at least one of the two sequences a time period is detected over the the inverter is controlled by means of the sequence, and wherein one of the sequences is selected as a function of the determined time duration for driving the inverter in order to load the switches according to a predefined load setpoint.

Furthermore, according to the invention, there is therefore provided a device for driving an inverter of the aforementioned type, wherein the inverter can be controlled by means of at least two predefined sequences of switching states having different switch-on times of the switching states, and wherein the control device is designed for at least one of the two sequences to detect a period of time over which the inverter is driven by the sequence and wherein the controller is adapted to select one of the sequences in response to the determined time duration for driving the inverter to load the switches according to a predefined load setpoint.

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

Advantages of the invention

By means of the present invention, a method and a device can be provided in which the switches can be loaded with simple means in accordance with a predetermined load setpoint in order to avoid corresponding overloads, in particular thermal overloads, of the power semiconductor switches. By knowing the load values of the two drive sequences and measuring the time duration over which the inverter is driven by at least one of the two sequences and selecting one of the sequences for driving the inverter on the basis of the time duration, the power semiconductor switch is almost loaded adjustable. In this case, the sequences can be formed as desired and in particular have different lengths, since the time duration of the use of the respective sequence is used to control the inverter. As a result, the inverter can be controlled flexibly by means of arbitrary sequences and, with little technical effort, a load distribution can be set in accordance with an almost arbitrary load setpoint. As a result, with the inventive method and the device according to the invention at low speeds, the power semiconductor switch of the inverter can be loaded more uniformly and overloading of individual semiconductor switches can be avoided. As a result, the power semiconductor switches can thus be made smaller, making the manufacture of an inverter generally less expensive and less expensive. Furthermore, the control effort or control effort for driving the inverter is thereby reduced, since fewer parameters have to be taken into account, whereby, in particular, a device for driving the inverter can be provided more cost-effectively and with technically simpler means due to the reduced computing effort.

Preferably, the respective time duration is detected for both sequences, via which the inverter is controlled by means of the respective frequency.

As a result, the activation duration of both sequences can be taken into account, as a result of which the activation of the inverter can generally be carried out more precisely.

It is particularly preferred if a set time duration for the at least one sequence is determined and one of the sequences is selected as a function of a deviation of the detected time duration from the set time duration for driving the inverter.

As a result, a desired value can be taken into account by simple means in order to set the predefined load on the switches, as a result of which rapid and targeted adjustment of the load distribution becomes possible.

It is furthermore preferred if the time duration is detected over a period of time.

As a result, the selection of the drive sequence can take place at arbitrary points in time, which makes the method more flexible, reduces the complexity of the control technology and generally allows the load on the switches to be set faster.

Preferably, the time period has a predefined or a variable duration.

It is further preferred if in each case the time duration is detected for both sequences and a deviation value of the respective detected time duration from the respective target time duration is determined and wherein one of the sequences for driving the inverter is dependent on the ratio of the deviation values is selected. In other words, it is detected which of the two sequences has a drive duration that deviates most strongly from the desired value.

As a result, it is possible to intervene quickly and in a targeted manner, even with slight deviations from the corresponding setpoint values, in order to achieve the load according to the load setpoint within a short period of time.

It is further preferred if the sequences have a different number of switching states.

As a result, any control sequences can be used, with the length of the respective sequences not having to be coordinated with one another.

This makes the driving method particularly flexible, since no corresponding pairs of sequences have to be formed.

It is further preferred if the inverter is controlled by means of pulse width modulation and wherein the predefined sequences have a different number of pulse width modulation periods.

As a result, the inverter can be controlled particularly effectively, wherein the method is particularly flexible due to the possible different number of pulse width modulation periods of the sequences and the control engineering effort is reduced.

It is further preferred if the two predefined sequences each set a voltage space vector with identical amplitude and phase position.

As a result, it is possible to change between the predefined sequences as desired, without the respective change having an effect on the controlled load.

It is furthermore preferred if the switch-on times of the switching states of the two sequences are selected such that the controllable switches are differently loaded by the respective sequence.

As a result, a load can be set precisely according to the predefined load setpoint by simple means by switching between the two sequences.

It is further preferred if the inverter is switched by means of two switching states in a voltage-free switching switching state and wherein the two predefined sequences have different turn-on of the two voltage-free switching switching states.

As a result, the load on the switches can be set particularly quickly in accordance with the predefined load setpoint value, since the switch-off switching states have a particularly high effect on the load on individual switches.

It is further preferred if one of the predefined switching sequences has only one of the voltage-free switching switching states.

Thus, by selecting this sequence, a large deviation from the load set point can be compensated quickly and precisely.

It is further preferred if a ratio value is determined as a function of the load setpoint and reference load setpoint values of the predefined sequences, and wherein the deviation value is adapted as a function of the ratio value.

Thereby, the detected deviation value can be continuously adjusted based on the load target value, thereby making the method more precise overall.

It is furthermore preferred if the ratio value is also determined as a function of the respectively detected time periods and the entire time period.

As a result, a particularly stable control of the drive of the inverter is possible overall, since short-term fluctuations can be compensated by averaging.

It is furthermore preferred if the switching states for different phase angles are mapped to corresponding reference switching states.

In other words, switching states or sequences of switching states are reshaped by corresponding switching states or sequences of switching states in order to be able to compare the individual sequences and their reference load states with little computational effort. As a result, the computational effort can be reduced, whereby the control unit can be made less expensive and can be manufactured in accordance with cost.

As mentioned above, according to the invention, a method is provided in which a period of time over which the inverter is driven by means of one or the other sequence is detected over a certain period of time, whereby the load of the semiconductor switches of the inverter can be estimated accordingly. On the basis of the period of time thus detected, it is possible to switch between the two sequences or to control the inverter by means of one of the two sequences in order to set a load on the switches in accordance with the predefined load setpoint. Preferably, the measured durations are compared with target durations for a corresponding period of time in order to be able to estimate which time duration of the respective sequence deviates more strongly from the corresponding desired value. In general, therefore, it is possible with simple means to set an almost arbitrary load distribution, which resorts to different sequences of switching states whose length may differ from one another.

It is understood that the features, properties and 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

1 shows in schematic form an inverter for driving an electrical load, in particular a three-phase machine;

2 shows a complex phasor diagram for explaining a space vector modulation method for driving the inverter;

3 shows in schematic form the voltage curve of three phases of the inverter within a pulse mode modulation period for setting a voltage space vector;

4 shows in schematic form a drive sequence by means of two drive sequences;

5 shows in schematic form a flowchart for selecting a sequence for driving the inverter;

6 Fig. 12 shows in schematic form an alternative flow chart for selecting a sequence for driving the inverter; and

7 shows the complex phasor diagram 2 for explaining a method for substituting switching states.

Embodiments of the invention

In 1 is an inverter for driving an electrical load, in particular an electric machine shown schematically and generally with 10 designated.

The inverter 10 is with a DC voltage source 12 connected and serves to the electrical consumer 14 , which in this case as a three-phase electric machine 14 is designed to energize three-phase. The inverter has three half-bridges, which are parallel to the DC voltage source 12 are connected and each have two controllable switch S. Between the switches S is in each case a half-bridge tap 16 formed, each with a phase conductor of the phases U, V, W of the electric machine 14 are connected.

Parallel to the switches S, a freewheeling diode D is in each case connected, which allows a current flow in the opposite direction.

In 1 are the switches S corresponding to the phase U, V, W, they provide and according to the assignment to a high potential of the DC voltage source 12 or a low potential of the DC voltage source 12 denoted by SAH, SLA, SHB, SLB, SHC, SLC. Accordingly, the freewheeling diodes are designated DHA, DLA, DHB, DLB, DHC, DLC.

By alternately opening and closing the switch S, a drive voltage is applied in each case between the phase conductors U, V, W, so that in each case a phase current IU, IV, IW adjusts, which sets the electric machine 14 drives. The inverter 10 is preferably formed by means of semiconductor switches. The switches of the inverter are by means of a control unit shown schematically 18 alternately opened and closed, to provide the phase voltages with a certain gradient, and provide a corresponding voltage space pointer and the electric machine 14 to energize accordingly with the phase currents IU, IV, IW.

In 2 is a complex phasor diagram for explaining the space vector modulation for driving the load 14 or the electric machine 14 represented and generally with 20 designated.

In the pointer diagram 20 is a voltage vector V * with a drive angle alpha of the electric machine 14 shown. In the pointer diagram 20 Also shown are six ground voltage indicators V1, V2, V3, V4, V5, V6, which result when one or two of the switches S of the inverter 10 be closed and the electric machine is controlled accordingly. In order to set the voltage vector V *, which in this example has the driving angle alpha between the ground voltage indicators V1 and V2, this is achieved by alternately driving the inverter 10 realized in accordance with the base voltage vector V1 and the ground voltage vector V2. The two ground voltage vectors V1, V2 are alternately set with a predefined switching frequency, so that at the same duty cycle of the ground voltage vector V1, V2, the voltage vector V * results in a phase angle alpha of 30 °. If a voltage vector V * has to be set with a larger activation angle alpha, the on-time of the basic voltage vector V2 is correspondingly extended and the on-time of the basic voltage vector V1 is shortened. Thus, the switch S of the inverter can be controlled by pulsed driving 10 the voltage space vector V * realize with an arbitrary drive angle alpha.

If the voltage vector V *, as in the in 2 In the case shown with a smaller amount (shorter length) than the basic voltage space vectors V1, V2 is to be set, a zero voltage pointer V0, V7 is set in accordance with which the switches SHA, SHB, SHC on the upper side and SLA, SLB, SLC on the lower side of the inverter 10 are open. The respective other switches S are closed accordingly. Accordingly, the voltage vector V * can be realized by a combination of the basic voltage space vector V1 and V2 and one of the zero voltage V0, V7.

For energizing the three-phase current consumer 14 or the electric machine 14 the voltage space vector V * is provided by sequentially adjusting the different fundamental voltage space vectors V1-V6 and the zero voltage pointers V0, V7 in a fast sequence. As a result, the different switches S and the different freewheeling diodes D of the inverter 10 evenly loaded at a correspondingly fast rotating voltage space vector V *. If the rotational frequency of the voltage space vector V * is very low or zero, for example, at low speeds of the electric machine 10 , the corresponding switches S and the diodes D of the inverter 10 loaded over a long period of time, so that an overload of the corresponding switches S and the diodes D may occur and the switches S and the diodes D of the inverter 10 generally unevenly loaded. In order to prevent overloading of each of the switches S and diodes D, measures must be taken to distribute the load to different ones of the switches S and the diodes D.

In 3 are waveforms of the phase voltages of the three phases U, V, W within a pulse width modulation period T shown to set the voltage vector V0, V1, V2, V7 successively. Within the pulse width modulation period T, the duration of the individual voltage vectors can be varied in order to be able to precisely set the voltage space vector V *.

wobei m der Belastungswert ist, t0 die Schaltdauer des Nullspannungszeigers V0 und t7 die Schaltdauer des Nullspannungszeigers V7. Der Belastungswert m kann folglich zwischen dem Wert 1 und dem Wert 0 eingestellt werden, wobei bei einem Wert 1 die oberen Schalter SHA, SHB, SHC bzw. die oberen Freilaufdioden DHA, DHB, DHC des Wechselrichters 10 stärker belastet werden und bei einem Wert 0 die unteren Schalter SLA, SLB, SLC bzw. unteren Freilaufdioden DLA, DLB, DLC des Wechselrichters 10 stärker belastet werden. Dies gilt speziell für die Berechnung des Belastungswertes m sofern zwei benachbarte Grundspannungsraumzeiger V1–V6 und wenigstens ein Nullspannungszeiger V0, V7 verwendet wird, wie beispielsweise für eine Ansteuerungssequenz nach 3.Since the zero voltage pointer V0 only the switches SLA, SLB, SLC, the low potential of the voltage source 12 are assigned, loaded, and there according to the zero voltage pointer V7 only the Switch SHA, SHB, SHC, the high potential of the DC voltage source 12 are assigned, can be compensated by a targeted distribution of the zero voltage pointer V0, V7 uneven load between the upper switches THA, THB, THC and the lower switches TLA, TLB, TLC. A corresponding load value m is calculated by the formula

where m is the load value, t0 is the duty cycle of the zero voltage pointer V0 and t7 is the duty cycle of the zero voltage sense V7. The load value m can thus be set between the value 1 and the value 0, with a value 1, the upper switch SHA, SHB, SHC or the upper freewheeling diodes DHA, DHB, DHC of the inverter 10 more heavily loaded and at a value 0, the lower switches SLA, SLB, SLC and lower freewheeling diodes DLA, DLB, DLC of the inverter 10 be charged more heavily. This is especially true for the calculation of the load value m if two neighboring basic voltage space vector V1-V6 and at least one zero voltage vector V0, V7 is used, as for example for a drive sequence 3 ,

und für einen der Schalter SLA, SLB, SLC der unteren Seite des Wechselrichters 10 durch:

wobei t_min die minimal mögliche Einschaltdauer des Schalters S, t_max die maximal mögliche Einschaltdauer des Schalters S ist, um den aktuellen Spannungsraumzeiger V* einzustellen und t_on die aktuelle Einschaltdauer in der entsprechenden Pulsweitenmodulationsperiode T ist, die den aktuellen Spannungsraumzeiger V* einstellt. Dadurch entsteht ein weiterer Freiheitsgrad, um lsm einstellen zu können. Dabei ist anzumerken, dass der allgemeine Belastungswert lsm gleich bleibt, unabhängig davon welcher der Schalter zur Berechnung herangezogen wird. Dadurch kann die Belastung eines Schalters S des Wechselrichters 10 berücksichtigt werden. Dabei kann der Belastungswert m durch den allgemeinen Belastungswert lsm ersetzt werden.In general, a general load value lsm can be determined on the basis of the general switch-on time t of one of the switches S. In this case, one of the switches S is selected, such as the one that is heavily loaded. The load value lsm is for one of the switches SHA, SHB, SHC the upper side of the inverter 10 calculated by:

and for one of the switches SLA, SLB, SLC of the lower side of the inverter 10 by:

where t_min is the minimum possible duty cycle of the switch S, t_max is the maximum duty cycle of the switch S to set the current voltage space pointer V * and t_on is the current duty cycle in the corresponding pulse width modulation period T setting the current voltage space pointer V *. This creates another degree of freedom to set lsm. It should be noted that the general load value lsm remains the same, regardless of which of the switches is used for the calculation. This allows the load of a switch S of the inverter 10 be taken into account. In this case, the load value m can be replaced by the general load value lsm.

According to the invention, two sequences of consecutive switching states V0-V7 are used to generate a given voltage space vector V * having a certain magnitude and angle alpha. The different sequences have different sequences of switching states V0-V7, so that the switches S of the inverter 10 be charged differently. For each of the two sequences, a corresponding load value is determined as the reference load value m1, m2. The inverter is set to set the determined voltage space vector V * 10 controlled alternately with the first of the two sequences and the second of the two sequences, wherein both sequences A, B set the same voltage space vector V *. The inverter 10 is driven for a certain period of time by means of the first of the two sequences A, B and driven for a certain period of time by means of the second sequence. As a result, a desired load value m, which lies between the reference load values m1, m2, can be set by the known different reference load values m1, m2 of the two sequences.

In 4 is a drive sequence by means of two different drive sequences A, B shown schematically. This will be the inverter 10 or the electric machine 14 controlled over different durations by means of a first sequence A and a second sequence B. The sequences A, B are formed by an arbitrary number of consecutive switching states V0-V7 of the controllable switches S and have any desired number of pulse width modulation periods T. As in 4 is shown, the inverter is 10 is controlled by means of the sequence A over a period tA1 and controlled by means of the sequence B over a second time period tB2. Furthermore, in 4 shown that before the period tA1 of the inverters 10 is controlled by the sequence B and after the period tB2 of the inverter 10 is controlled by the sequence A. Further, a measurement period TM in 4 which extends over the periods tA1 and tB2 and each time period before and after the two periods tA1, tB2. The periods before the two periods tA1, tB2 are designated tB1 and tA2.

In the course of the method according to the invention is detected over the measuring period TM, by means of which of the two sequences A, B of the inverter 10 is driven and accordingly a period tA, tB determined during the inverter 10 is controlled by means of the respective sequence A, B. The measurement period TM may have a predefined or a variable time duration. In 4 During the measurement period TM, the inverter will become the inverter 10 via the period tA = tA1 + tA2 by means of the sequence A and over a period of time tB = tB1 + tB2 driven by the sequence B.

For the sequences A, B, the respective load reference value m1, m2 is known, so that on the basis of the respective time duration tA, tB a speaking load value of the inverter 10 can be determined.

According to the invention, a load setpoint m of the inverter 10 defined and a temporal relationship of durations tAS, tBS on the inverter 10 is to be controlled by the sequence A or the sequence B, determined to adjust the load setpoint m accordingly. The thus determined set time durations tAS, tBS determine the time over which one of the sequences A, B must be used to set the predefined load setpoint m.

From the measured time periods tA, tB and the target time durations tAS, tBS, corresponding deviation values ΔIA, ΔIB are determined, according to the formula ΔIA = tAS - tA ΔIB = tBS - tB where ΔIA, ΔIB are the corresponding deviation values for the sequences A, B, tA, tB are the measured time durations, and the tAS, tBS are the set time durations to set the corresponding load target value m1. From the deviation values ΔIA, ΔIB, it is determined whether the inverter 10 is to be controlled by the sequence A or by the sequence B or must, as explained in more detail below.

In 5 is a method for driving the inverter 10 generally with 30 designated.

First, it is added 32 determines whether the deviation value ΔIA is greater than the deviation value ΔIB. If the deviation value ΔIA is greater than deviation value ΔIB, the inverter becomes 10 controlled by the sequence A, as in 34 is shown. Further, the deviation values ΔIA, ΔIB become 36 recalculated accordingly. The deviation value ΔIA is adjusted by means of the formula: ΔIA = ΔIA + r * tA-tA

wobei m der Belastungssollwert und m1, m2 die Belastungsreferenzwerte der Sequenzen A, B sind. Ferner wird der Abweichungswert ΔIB entsprechend angepasst mittels der Formel: ΔIB = ΔIB + (1 – r)*tB – tB, wobei (1 – r)·tB der Sollzeitdauer tBS entspricht. Sofern bei 32 festgestellt wird, dass ΔIB größer ist als ΔIA, wird bei 38 der Wechselrichter 10 mittels der Sequenz B angesteuert, wie es bei 38 gezeigt ist und parallel bei 40 der Abweichungswert ΔIA berechnet mittels der Formel: ΔIA = ΔIA + r·tB, wobei r*tB der Sollzeitdauer tAS entspricht. Der Abweichungswert ΔIB wird neu berechnet mittels der Formel ΔIB = ΔIB + (1 – r)·tB – tB wobei jeweils tB die gemessene Zeitdauer ist, die der Wechselrichter 10 mittels der Sequenz B angesteuert wird und (1 – r)·tB der Sollzeitdauer tBS entspricht.Where r · tA corresponds to the set time duration tAS, tA is the time duration over which the inverter 10 is driven by the sequence A and where r is a deviation value calculated by means of the formula

where m is the load setpoint and m1, m2 are the load reference values of the sequences A, B. Furthermore, the deviation value ΔIB is adjusted accordingly by the formula: ΔIB = ΔIB + (1-r) * tB -tB, where (1-r) · tB corresponds to the set time period tBS. If at 32 it is found that ΔIB is greater than ΔIA, is at 38 the inverter 10 controlled by the sequence B, as in 38 is shown and parallel at 40 the deviation value ΔIA is calculated using the formula: ΔIA = ΔIA + r * tB, where r * tB corresponds to the set time period tAS. The deviation value ΔIB is recalculated using the formula ΔIB = ΔIB + (1-r) * tB -tB where each tB is the measured time duration that the inverter 10 is controlled by the sequence B and (1 - r) · tB of the target time tBS corresponds.

In 6 is another method of controlling the inverter 10 shown schematically and generally with 50 designated.

It is at 52 determines whether the deviation value ΔIA is greater than ΔIB + k, where k is a constant. If at 52 has been found that the deviation value ΔIA is greater than ΔIB + k, is at 54 the inverter 10 controlled by the sequence A and parallel thereto at 56 the deviation values ΔIA, ΔIB recalculated, according to the formulas given above.

If at 52 it is found that ΔIA is smaller than ΔIB + k, is at 58 the inverter 10 controlled by the sequence B and parallel to the deviation values ΔIA, ΔIB recalculated according to the formulas given above.

wobei lsm1, lsm2 die allgemeinen Belastungswerte für die Sequenz A und die Sequenz B sind.The procedure 50 uses the above-mentioned general load value Ism based on the general on-time of one of the switches S. Other than the method 30 will in the process 50 the ratio r calculates by means of the formula

where lsm1, lsm2 are the general loading values for sequence A and sequence B.

As a result, different sequences A, B of arbitrary length and design can be used by the method according to the invention, wherein only the duration of use within the measurement period TM is determined, such as the load value m, lsm of the inverter 10 is set. On the basis of the thus detected load value m, lsm or on the thus detected activation duration tA, tB for the sequences A, B, it is decided by means of which of the sequences A, B the inverter 10 to be controlled.

As a result, an almost arbitrary load setpoint m, lsm can thus be set.

In 7 is the pointer diagram 20 out 2 shown schematically. In the pointer diagram 20 Six sectors are shown between the respective ground voltage vectors V1-V6 and generally designated I, II, III, IV, V, VI. To simplify the method according to the invention, the corresponding switching states V0-V7 can be mapped to a corresponding reference switching state or substituted by it. This facilitates the comparison between the different switching sequences. Different substitutions are made for the different sectors, as shown below: Sector II 2 → 1 3 → 2 0 → 7 7 → 0 Sector III 3 → 1 4 → 2 7 → 7 0 → 0 Sector IV 4 → 1 5 → 2 0 → 7 7 → 0 Sector V 5 → 1 6 → 2 7 → 7 0 → 0 Sector VI 6 → 1 1 → 2 0 → 7 7 → 0

It turns out that corresponding to the sectors I-VI, the corresponding switching states V0-V7 are mapped to corresponding reference switching states or substituted by them. As a result, the computational effort can be reduced since only the reference sector sequences are compared with one another.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• WO 2010/000548 A2 [0006]

Claims (14)

Procedure ( 30 ; 50 ) for driving an inverter ( 10 ) by means of space vector modulation, in particular for driving an electrical machine ( 14 ), where the inverter ( 10 ) has a plurality of controllable switches (S) and which is designed to provide a polyphase electric current (IU, IV, IW), in particular around the electric machine ( 14 ) to supply multiphase with electric current (I), whereby the inverter ( 10 ) in order to set up a plurality of consecutively different switching states (V0-V7) of the switches (S) and to provide a voltage in the form of a corresponding voltage space vector (V *), characterized in that the inverter ( 10 ) by means of at least two predefined sequences (A, B) of switching states (V0-V7) which have different switch-on times (t0-t7) of the switching states (V0-V7), wherein for at least one of the two sequences (A, B) a period of time (tA, tB) is detected, via which the inverter ( 10 ) is controlled by means of the sequence (A, B), and wherein one of the sequences (A, B) as a function of the determined time duration (tA, tB) for driving the inverter ( 10 ) is selected to load the switches (S) according to a predefined load setpoint (m, lsm). Method according to Claim 1, wherein a set time period (tAS, tBS) is determined for the at least one sequence (A, B) and one of the sequences (A, B) is determined as a function of a deviation (ΔIA, ΔIB) of the detected time duration (tA, tB ) from the set time duration (tAS, tBS) for driving the inverter ( 10 ) is selected.  Method according to claim 1 or 2, wherein the time duration (tA, tB) is detected over a period of time (TM). Method according to one of claims 1 to 3, wherein for both sequences (A, B) respectively the time duration (tA, tB) is detected and a deviation value (ΔIA, ΔIB) of the respective detected time duration (tA, tB) from the respective target time period ( tAS, tBS) and, depending on the ratio of the deviation values, one of the sequences (A, B) for driving the inverter ( 10 ) is selected.  Method according to one of claims 1 to 4, wherein the sequences (A, B) have a different number of switching states (V0-V7). Method according to one of claims 1 to 5, wherein the inverter ( 10 ) is controlled by means of pulse width modulation and wherein the predefined sequences (A, B) have a different number of pulse width modulation periods (T).  Method according to one of claims 1 to 6, wherein the two predefined sequences (A, B) each set a voltage space vector (V *) with identical amplitude and phase position.  Method according to one of claims 1 to 7, wherein the turn-on times (t0-t7) of the switching states (V0-V7) of the two sequences (A, B) are selected such that the controllable switch (S) by the respective sequence (A, B) are charged differently. Method according to one of claims 1 to 8, wherein the inverter ( 10 ) by means of two switching states (V0, V7) in a voltage-free switching switching state (V0, V7) is switched and wherein the two predefined sequences (A, B) have different switch-on (t0-t7) of the two voltage-free switching switching states (V0, V7) ,  The method of claim 9, wherein one of the predefined switching sequences (V0-V7) has only one of the voltage-free switching switching states (V0, V7).  Method according to one of Claims 1 to 10, a ratio value (r) being determined as a function of the load setpoint value (m; lsm) and reference load setpoint values (m1, m2; lsm1, lsm2) of the predefined sequences (A, B), and the deviation value ( ΔIA, ΔIB) is adjusted as a function of the ratio value (r).  Method according to one of Claims 1 to 11, wherein the switching states (V0-V7) for different phase angles are mapped to corresponding reference switching states (V0-V7). Contraption ( 18 ) for driving an inverter ( 10 ), in particular for driving an electrical machine ( 14 ), where the inverter ( 10 ) has a plurality of controllable switches (S) connected to provide a polyphase electric current (IU, IV, IW) having a Control unit ( 18 ), which is adapted to the inverter ( 10 ) in such a way that the inverter ( 10 ) assumes a plurality of consecutively different switching states (V0-V7) of the switches (S) in order to provide a corresponding voltage space vector (V *), characterized in that the inverter ( 10 ) can be controlled by means of at least two predefined sequences (A, B) of switching states (V0-V7) which have different switch-on times (t0-t7) of the switching states (V0-V7), and wherein the control device ( 18 ) is adapted to detect for at least one of the two sequences (A, B) a period of time (tA, tB) over which the inverter ( 10 ) is controlled by means of the sequence (A, B), and wherein the control unit ( 18 ) is adapted to one of the sequences (A, B) as a function of the determined time duration (tA, tB) for driving the inverter ( 10 ) to load the switches (S) in accordance with a predefined load setpoint (m; lsm). Motor vehicle drive train with at least one electric machine ( 14 ) for providing drive power, an inverter ( 10 ) for driving the electric machine ( 14 ) and with a device ( 18 ) for driving the inverter ( 10 ) according to claim 13.

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