DE102012210664A1 - Method for controlling inverter by space pointer pulse width modulation to control electric machine in motor vehicle drive strand, involves switching inverter by first switching state and by last switching state in voltage states - Google Patents

Abstract

The method involves controlling an inverter (10) such that seven switching states of a controllable switch are aligned to provide an electric voltage in form of a voltage space pointer. The inverter is switched within a pulse width modulation period into voltage-free switching states and in voltage states in which the electric voltage is provided. The inverter is switched by a first switching state within the pulse width modulation period and by a last switching state within the pulse width modulation period in the voltage states. Independent claims are also included for the following: (1) a device for controlling an inverter (2) a motor vehicle drive strand.

Description

The present invention relates to a method for driving an inverter by means of space vector pulse width modulation, in particular for driving an electrical machine, wherein the inverter comprises a plurality of components, which are formed by a plurality of controllable switches and a corresponding plurality of free-wheeling diodes, wherein the inverter is adapted is to provide a polyphase electric current, in particular in order to supply the electric machine polyphase with electric current, wherein the inverter is driven such that a plurality of successive switching states of the switches is arranged to provide an electrical voltage in the form of a voltage space vector, said Inverter is switched within a pulse width modulation period by means of at least one of the switching states in a voltage-free switching switching state, and by means of at least one of the switching conditions is switched to a voltage state in which the electrical voltage is provided.

The present invention further relates to an apparatus for driving an inverter, in particular for driving an electrical machine, wherein the inverter comprises a plurality of components, which are formed by a plurality of controllable switches and a corresponding plurality of free-wheeling diodes, and which are connected thereto, to provide a polyphase electric current, in particular to multiphase electric power to the electrical machine, comprising a controller adapted to drive the inverter so that the inverter accepts a plurality of successive switching states of the switches to form an electrical voltage to provide a voltage space pointer, wherein one of the switching states within a pulse width modulation period switches the inverter in a de-energized switching state and one of the switching states within the pulse width modulator period the inverter switches to a voltage state to provide the electrical voltage.

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 known driving method, the electrical loads are controlled by means of an inverter with power semiconductor switches. The adjustment of the eight successive ground voltage pointers for generating the voltage space vector is realized by alternately turning on and off certain power semiconductor switches of the inverters. 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 semiconductors are switched very often or very long and thus thermally stressed 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, for example, 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.

Since the, in particular thermal, load of individual power semiconductor switches of the inverter is dependent on a phase angle of the provided Stromraumzeer or individual power semiconductor switches of the inverter for different phase angles of the provided Stromraumzeer be charged differently, for example in the DE 10393516 T1 proposed to use a certain zero vector in certain angular ranges of the provided Stromraumzeer to reduce the switching losses of the power semiconductor switches.

The disadvantage here is that switching between a voltage-free switching switching state to another voltage-free switching switching state to distribute the burden of the switches and freewheeling diodes, switching operations requires in which the switching states of all switches of the inverter must be changed whereby high switching losses occur and voltage - And / or current fluctuations of the inverter occur that cause large reactive power or affect the targeted power.

Disclosure of the invention

The invention therefore provides a method for driving an inverter by means of space vector pulse width modulation of the aforementioned type, wherein the inverter is switched to one of the voltage states by means of a first switching state within the pulse width modulation period and a last switching state within the pulse width modulation period. In particular, the inverter is switched to a voltage state to provide the electrical voltage.

Furthermore, the invention therefore provides a device for driving an inverter of the type mentioned, wherein the control device is adapted to switch the inverter by means of a first switching state within the pulse width modulation period and a last switching state within the pulse width modulation period in one of the voltage states.

Finally, according to the invention, a motor vehicle drive train is provided 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.

Advantages of the invention

Because the first and the last of the switching states within the pulse width modulation period switch the inverter to a voltage state, the following pulse width modulation period can also start with a switching to a voltage state switching state and thereby form a transition between two different de-energized switching states while reducing the switching losses. As a result, arbitrary switching states within the pulse width modulation period can be used, thus optimizing the drive of the inverter with respect to the, in particular thermal, load distribution, the switching losses and fluctuations of the input voltage and the output current, which generally improves the efficiency of the inverter and the total losses of the inverter Inverter can be reduced.

For the purposes of the present invention, a voltage-free switching state is understood to mean that no supply voltage is present between the phase conductors of the inverter at the output terminal of the inverter, and a voltage state is understood to be present at the output terminals of the inverter between at least two of the phase lines. provided.

Preferably, the first and the last switching state are identical within the pulse width modulation period.

As a result, an optimal switching sequence can be determined for all voltage space phasors in order to determine the performance of the inverter and the controlled power without unnecessary switching of the switches at the transition between two pulse width modulation periods.

It is particularly preferred if the inverter is switched within the pulse width modulation period in a second voltage state in which the switching positions of the switches of at least two phases of the inverter compared to the switching positions of the switch from the switching states of the first voltage state.

For the purposes of the present invention is meant by different switching positions of the switch that in one switching position of the switch, the current flow through the respective switch is interrupted and in the other switching position, the current flow through the respective switch is possible, that is not interrupted.

As a result, current fluctuations at the output of the inverter and voltage fluctuations at the input of the inverter can be reduced, since the switching between the switching states has a stronger effect on a phase angle of the Stromraumze than the amplitude of the Stromraumzeiger.

It is further preferred if the inverter is switched within the pulse width modulation period in a third voltage state in which the switching positions of the switch only one phase of the inverter from the respective switching positions of the switch Switching states of the first state of stress and the second state of stress differ.

As a result, a reactive current in the DC link of the inverter can be reduced and at the same time a voltage vector with a maximum length can be set.

It is furthermore preferred if only one of the voltage-free-switching switching states is switched within the pulse width modulation period.

As a result, the switching losses of the inverter can be further reduced while counteracting a non-uniform load of the inverter.

It is particularly preferred if the voltage-free switching switching state is selected such that when switching between the switching states within the pulse width modulation period, only the switches of a phase of the inverter can be switched.

As a result, the switching losses within the pulse width modulation period can be further reduced.

It is further preferred if the switching states within the pulse width modulation period are connected in series such that when switching between the switching states, only the switches of a phase of the inverter are switched.

As a result, the switching losses can generally be further reduced.

It is further preferred if in each case a voltage-free switching switching state is switched between the first voltage states and the second voltage states.

Thereby, the simultaneous switching of the switches of two phases of the inverter can be avoided, whereby the switching losses can be further reduced.

It is further preferred if a plurality of switching sequences for different voltage space vector and current space vector are predefined and are selected as a function of the voltage space vector and / or current space vector to be set.

As a result, the control engineering effort can be reduced and optimal switching sequences for the different voltage space and / or current space pointers can be determined in advance.

It is furthermore preferred if the switching sequences are selected as a function of an input voltage of the inverter, a rotational frequency of the voltage space vector and / or a rotor position of the electrical machine.

As a result, the control of the inverter can be further optimized.

It is particularly preferred if the sequences are stored in a map. As a result, the computational effort of the associated control unit can be reduced.

It is further preferred if the switching sequences depend on a resulting load distribution of the inverter, a phase shift between the voltage space vector and the current space vector, a resulting variation of the input voltage of the inverter, a resulting fluctuation in the output current of the inverter, in response to resulting losses of the DC link of the inverter , a resulting vibration of the driven electrical load and / or a resulting noise of the driven electrical load for different voltage space pointer and current space pointer are predefined.

This can optimize the performance of the inverter and reduce the losses of the inverter.

It is further preferred if the switching states of the pulse-width modulation period for an angular range of the voltage space vector are determined on the basis of a pulse width modulation period of a reference angle range.

As a result, the sequences for the reference angle range can be determined and, based on the reference angle range, the corresponding sequences for all phase angles of the voltage space vector can be determined with little computation effort.

It is understood that features, properties and advantages of the method according to the invention also apply 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;

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

3 shows in schematic form a course of three phase voltages for setting different voltage space vector;

4 shows in schematic form the course of three phase voltages within a pulse width modulation period, which begins and ends with a voltage state;

5 shows a complex phasor diagram for explaining different adjustment ranges of the stress space vector;

6a , b shows a complex vector diagram for explaining variations of the voltage space vector at different drive sequences.

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 in this case as an electric machine 14 is designed to energize three-phase. The inverter 10 has three half-bridges, which are parallel to the DC voltage source 12 are connected and each have two controllable switch S. Each of the switches (S) can take either a closed or an open switch position, the open switch position prevents current flow through the switch (S) and the closed switch position allows current flow through the 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 DC voltage source 12 is a DC link capacitor 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 SHA, 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 to provide a rotating voltage space pointer and the electric machine 14 to energize accordingly with the phase currents IU, IV, IW. At the same time, the voltage vector is generated by the inverter 10 provided, whereupon the current space pointer adjusts accordingly depending on the controlled load.

In 2 is a complex phasor diagram for explaining the space vector modulation for driving the electrical 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 α 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 * with a maximum length, which in this example has the actuation angle α 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 the voltage indicator V * with a phase angle of 30 ° results for the same duty cycle of the ground voltage vector V1, V2. If a voltage vector V * has to be set with a larger actuation angle α, the duty cycle 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 α.

If the voltage vector V *, as in the in 2 illustrated case with a smaller amount (shorter length) than the Basic voltage space pointer V1, V2 is set, is set in accordance with a zero voltage pointer V0, V7, in which the switches SHA, SHB, SHC on the upper side or SLA, SLB, SLC on the lower side of the inverter 10 are open. The other of the 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.

Depending on the voltage space vector V *, a current space vector I * is established. The current space vector I * has an amplitude and a phase angle, which depend on the driven electrical load 14 to adjust. The phase angle of the current space vector I * can be in phase with the phase angle α of the voltage space vector V * or have a phase shift φ.

For energizing the electrical load 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 at a correspondingly fast rotating voltage space vector V * evenly loaded, in particular phased evenly loaded. 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 freewheeling diodes D of the inverter 10 a phase U, V, W loaded over a long period of time, so that an overload of the respective switches S and the freewheeling diodes D can occur and the switches S and freewheeling diodes D of the inverter 10 are generally unevenly loaded, in particular phased uneven. In order to prevent overloading of each of the switches S and freewheeling diodes D, measures must be taken to distribute the load to different ones of the switches S and freewheeling 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 basic voltage space pointers V0, V1, V2, V7 successively. Within the pulse-width modulation period T, a switch-on duration t0, t1, t2, t7 of the individual base voltage space vector V0, V1, V2, V7 can be varied in order to adjust the voltage space vector V * precisely.

wobei 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 switches 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. Since the distribution of the voltage-free switching switching states V0, V7 has no influence on the voltage vector V *, a load distribution of the switches of the inverter can be achieved by variation between the voltage-free switching switching states V0, V7 10 be set. A corresponding load value m is calculated by the formula

where t0 is the switching time of the zero voltage indicator V0 and t7 is the switching duration of the zero voltage indicator 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 eine weitere Möglichkeit, um einen Belastungswert einstellen zu können. Dabei ist anzumerken, dass der allgemeine Belastungswert lsm gleich bleibt, unabhängig davon welcher der Schalter zur Berechnung herangezogen wird. 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 the minimum possible duty cycle of the switch S, t_max the maximum possible Duty cycle of the switch S is to set the current voltage space vector V * and t_on is the current duty cycle in the corresponding pulse width modulation period T, which adjusts the current voltage space vector V *. This creates another possibility to set a load value. It should be noted that the general load value lsm remains the same, regardless of which of the switches is used for the calculation.

In 4 three phase voltages U, V, W for a pulse width modulation period T are shown schematically. The pulse width modulation period T is like the pulse width modulation period T off 3 divided into individual switching states V2, V7, V6 of the controllable switch S. The switching states V2, V7, V6 of the switch S have a duty cycle t2, t7, t6 accordingly.

The pulse width modulation period T has five switching states, wherein the pulse width modulation period T starts and ends with a voltage state V2 which corresponds to the basic voltage space vector V2. The pulse width modulation period T also has a second voltage state V6, which corresponds to the basic voltage space vector V6. The switching states V2 and V6 are separated from one another in each case by a switching state which switches off without voltage or by the zero-voltage pointer V7.

From the strand voltages U, V, W from 4 becomes clear that when switching between the switching states V2, V7, V6 only one pair of switches of the inverter 10 is switched or only the switches S of the inverter 10 are switched, which are assigned to one of the phases U, V, W. As a result, due to this pulse width modulation period T, particularly low switching losses occur in the inverter 10 on. Due to the fact that the pulse width modulation period T starts and ends with the switching state V2, a following pulse width modulation period can likewise start with the switching state V2 without additional switching losses occurring.

In the pulse width modulation period T off 4 For example, the switching states V2 and V6 corresponding to the fundamental voltage space vector V2, V6 used in the complex phasor diagram are used 20 are not adjacent or in which the switching states of two switch pairs and the switches of two phases are different from each other. The respective switch pairs are formed by the pairs of switches SHA, SLA and SHB, SLB and SHC, SLC. This can advantageously current fluctuations at the output of the inverter 10 and reactive currents at the input of the inverter 10 or in the DC link 15 be reduced, as explained in more detail below.

The switch-on durations t0-t7 are determined or calculated as a function of the voltage space vector V * to be set.

In the following, reference is made to different switching sequences of the switching states V0-V7, wherein the switching sequences are shown only as a sequence of numbers of the individual switching states V0-V7. As an example, the sequence of the pulse width modulation period T will be described below 4 designated as -27672- and commonly referred to as sequence 1.

In 5 is the complex vector diagram 20 schematically illustrated to explain different controls for different voltage space vector V *. Between the ground voltage hands V1, V2 and V6 are two sectors 22 . 24 schematically illustrated, the different drive ranges of the voltage space vector V * form. The first sector 22 is spanned by the ground voltage vectors V2 and V6 and the second sector 24 is spanned by the Grundspannungsraumzeiger V1, V2 and V6. The sectors 22 . 24 are by a line 26 separated from each other, which is formed between the ends of the Grundspannungsraumzeiger V2 and V6.

If the voltage space vector V *, which is in 5 is not shown for reasons of clarity, has a phase angle α and a length V, so that the voltage space vector V * in the first sector 22 is to be set or adjusted, the voltage space vector V * can be adjusted by a combination of the base voltage vector V2 and V6 and one of the zero voltage V0 or V7. If the voltage space vector V * has a phase angle α and a length V, so that the voltage space vector V * in the second sector 24 is or should be set, the voltage space vector V * can be formed by a combination of the base voltage vector V1, V2 and V6 and possibly by one of the zero voltage V0, V7.

Sequence 1, which has the switching state combination -27672-, thus provides a voltage space vector V * located in the first sector 22 located. A sequence 2 with the switching state sequence -21612- provides a voltage space pointer V * located in the second sector 24 located.

Since the sequences 1 and 2 have only four switching operations, the switching losses of these sequences are very low. Furthermore, no further occur between the switching sequences Switching losses, since both sequences 1, 2 each begin with the same Grundspannungsraumzeiger V2 and end.

By combining the basic voltage space vector V2 and V6 in sequence 1 or the combination V1, V2 and V6 in sequence 2, the current fluctuations at the input of the inverter or in the DC link 15 and at the output of the inverter 10 be reduced, as explained in more detail below.

It is understood that the combination of the ground voltage vectors V2, V6 and V1, V2, V6 for the sectors 22 . 24 also corresponding to all other basic voltage space vector V1-V6 or all corresponding sectors of the vector diagram 20 are applicable.

In 6a . 6b is a complex phasor diagram 30 schematically illustrated to explain variations of the resulting current space vector I *.

In 6a is the generation of the current space pointer I * represented by the ground voltage vector V2, V6 and V1, V2, V6. As a result of the fact that the current space vector I * is formed by the fundamental voltage space vectors V1, V2, V6 or V2, V6, a fluctuation of the current space vector I * occurs, which in 6a with an arrow 32 is indicated. Due to the position of V2 and V6, a fluctuation of the phase angle α of the current space vector I *, which is represented by the arrow 32 is indicated. In other words, the current space vector I * adjusts itself with a positive phase angle α if the basic voltage space vector V2 is activated and with a negative phase angle α if the basic voltage space vector V6 is controlled.

In contrast, in 6b a variation of the current space pointer I *, which is set by the conventional driving method. In this case, the current space vector I * is formed by the basic voltage space vector V1 and one of the zero voltage vectors V0, V7. By this type of actuation, a fluctuation of the Stromraumze I * adjusts by an arrow 34 is indicated. By alternately using the basic voltage space vector V1 and a zero voltage vector V0, V7, the amount V of the current space vector I * varies. In other words, a larger amount of the current space vector I * is set, as long as the basic voltage space vector V1 is activated and a smaller amount when a zero voltage vector V0, V7 is activated. By varying the magnitude of the current space pointer I * according to the prior art, only a fluctuating power output of the driven load can be achieved. Furthermore, voltage fluctuations occur at the input terminals of the inverter 10 , increased DC link losses and current fluctuations at the output of the inverter 10 on.

In 7a , b is the complex vector diagram 30 schematically illustrated to explain the effects of the fluctuations of the current space pointer I * in the event that the controlled load 14 the electric machine 14 is. In 7a the current space pointer I * is shown, which is set by the basic voltage space vector V2, V6 or V1, V2 and V6. In 7a two lines are also shown, each representing a generated by the current space pointer I * constant torque M1, M2. This makes it clear that the fluctuation of the current space vector I *, indicated by the arrow 32 is indicated, only causes a small variation between the torques M1 and M2. This makes it clear that a control of the electric machine 14 caused by the Grundspannungsraumzeiger V2, V6 and V1, V2, V6 no significant fluctuation of the output torque M.

In contrast, in 7b shown how the magnitude fluctuations of the current space pointer I * affect according to the prior art. The current space indicator I * fluctuates, as indicated by the arrow 34 is indicated. In 7b two lines each of a constant torque M3, M4 are shown. Out 7b It can be seen that the fluctuations in the amount of current I result in a very large fluctuation of the torque between the torque M3 and the torque M4. This makes it clear that by means of the control by means of V2, V6 or V1, V2, V6 also lower torque fluctuations can be achieved compared to the prior art.

Furthermore, the input current fluctuations of the inverter 10 reduced at the sequences 1 and 2, since either only switched between voltage states of the basic voltage space vector V1-V6 and thus always a current in the inverter 10 flows in or is switched between lower amounts of current, so that the current fluctuations of the input current of the inverter 10 are reduced.

An extension of the sequence 2 is given by sequence 3 with the switching state sequence -2767276- and sequence 4 with the switching state sequence -6727672-. As explained above, these sequences produce less current fluctuation at the input of the inverter 10 and at the output of the inverter 10 , Since sequences 3 and 4 start and end with different switching states, these sequences become preferably alternately used in tandem to minimize the switching losses when switching between sequences 3 and 4. Alternatively, in sequences 3 and 4, V1 can also be used instead of switching state V7. The more frequent switching between the switching states in sequences 3 and 4 can cause fluctuations in the DC input voltage and in the output current of the inverter 10 be achieved.

As an alternative to the sequences 1 and 2, the sequences 5 and 6 with the switching state sequences -10301- or -12321- can also be used. The ground voltage phasors of sequences 1 and 2 were mirrored at an angle bisector between the fundamental voltage space vectors V1 and V2 to arrive at sequences 5 and 6. If the use of sequences 5 and 6 is more favorable than the use of sequences 1 and 2, in this case V1 is used as the start and end switching state. Further, in the sequence 5, the zero voltage pointer V7 was replaced by the zero voltage pointer V0. Correspondingly, the sequences 3 and 4 can be replaced by the sequences 7 and 8 with the switching state sequences -1030103- and -3010301-, respectively. In the sequences 7 and 8, alternatively, the switching state V0 can be replaced by V3. By an appropriate selection of the sequences 1, 2, 5 or 6 or 3, 4, 7 and 8 of the load setpoint m can be selectively adjusted.

6 and 7 refer to the driving situation where φ = 0 and α = 0. In other driving situations, other effects may occur. Depending on the driving situation, such as in a phase shift, certain sequences may be beneficial.

To set the load setpoint m, the sequences 9 and 10 with the respective switching status sequence -27212- or -21012- are given by way of example. By changing between sequences 9 and 10, the load setpoint m can be easily set to any value.

The combination of the sequences 9 and 10 also has the effect that between the zero voltage pointer V7 of the sequence 9 and the zero voltage pointer V0 of the sequence 10 four consecutive basic voltage space pointers are connected. As a result, the current vector is increased and there is a disadvantageous fluctuation of the current at the output of the inverter 10 , If the sequence 1 or 2 is combined with the sequence 10, that is, for example, the switching state sequence -27672- and -21012- is set, the number of consecutive basic voltage space pointers between the different zero voltage space pointers V7, V0 can be reduced to two. The sequence 1 or 2 can also be set as an alternative to the sequence 9. As a result, a load setpoint of m = 1 can be set. As a result, overall the current fluctuation of the inverter 10 be reduced.

Alternatively to the sequences 1 to 10, a sequence 11 with the switching state sequence -2721012- or the sequence 12 with the switching state sequence -2101272- can also be used to reduce current and voltage fluctuations. Alternatively, the symmetrical sequences 13 and 14 with the switching state sequences -1012721- and -1272101- which are mirrored at the angle bisector between the ground voltage vectors V1 and V2 can also be used.

Preferably, all sequences for different voltage space vectors V * together with the effects on the overall system, such as voltage fluctuations at the input of the inverter 10 , Current fluctuations at the input of the inverter 10 and at the output of the inverter 10 , and acoustic and electromagnetic effects stored in a map for each voltage space vector V * and each current space vector I * and the frequency of the phases U, V, W. These values are predefined or measured and stored in the map. If the driven consumer 14 is an electric motor, the rotor position, the torque, the rotational speed of the engine and the variation of the torque are stored in the map. According to the respective requirement, the optimum sequence for driving the inverter is for each drive situation and each voltage space pointer, current space pointer, phase shift, electrical frequency, rotor frequency or rotor speed and / or rotor position 10 selected and used.

Accordingly, the criteria for selecting the appropriate sequence of the desired load setpoint m, voltage fluctuations in the DC link of the inverter 10 , Losses in the DC link of the inverter 10 , Phase current fluctuations and / or torque fluctuations at the output of the inverter 10 or on the driven electrical machine 14 between the voltage space vector V * and the current space vector I *.

If the phase angle α of the voltage space vector V * changes and a sequence is selected which starts with a switching state V1-V6 which differs from the last switching state V1-V6 of the previous pulse width modulation period T, a transition sequence can be used to obtain a pulse width modulation period T to a subsequent pulse width modulation period T to pass.

If the voltage space vector V * lies in the angular range between V1 and V2 and the first switching state of the following pulse width modulation period is T V2, the following sequences can be used:
-6121612- or -6727672- (depending on the voltage space vector V *)
-612- or -672- (depending on the voltage space vector V *)
-61012-
-101272-
-303272-
-327212-
-301272-
-47212-
-47612- or -47672- (depending on the voltage space vector V *)
-501212-
-012-
-01272-
-72-
-7212-
-721012-

If the voltage space vector is in the angular range between V1 and V2 and the first voltage state of the following pulse width modulation period is T V1, the following sequences can be used:
-3212321- or -3010301- (depending on the voltage space vector V *)
-321 - or -301- (depending on the voltage space vector V *)
-32721-
-272101-
-676101-
-610121-
-672101-
-50121-
-50321- or -50301- (depending on the voltage space vector V *)
-472121-
-472101-
-721-
-72101-
-01-
-0121-
-012721-

All sequences are explained here merely as an example for the angular range between V1 and V2, whereby, however, the sequence for this angular range between V1 and V2 can be extended or applied to all angular ranges between the basic voltage space vectors V1-V6. In this case, the phase angle of the voltage space vector V * to be set and the current space vector I * is converted to a reference phase angle α in the angular range between V1 and V2, one of the abovementioned sequences is selected on the basis of the criteria given above and the vectors of the selected sequence are converted accordingly to provide the voltage space pointer V * to be set.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• WO 2010/000548 A2 [0006]
• DE 10393516 T1 [0007]

Claims (15)

Method for controlling an inverter ( 10 ) by means of space vector pulse width modulation, in particular for driving an electrical machine ( 14 ), where the inverter ( 10 ) comprises a plurality of components (S, D), which are formed by a plurality of controllable switches (S) and a corresponding plurality of freewheeling diodes (D), wherein the inverter ( 10 ) is designed to provide a polyphase electric current (IU, IV, IW), in particular around the electric machine ( 14 ) are supplied with electric power in a multiphase manner, the inverter ( 10 ) is controlled such that a plurality of successive switching states (V0-V7) of the switches (S) is set up to provide an electrical voltage in the form of a voltage space vector (V *), wherein the inverter ( 10 ) within a pulse width modulation period (T) by means of at least one of the switching states (V0-V7) in a de-energized switching state (V0, V7) is switched and by means of at least one of the switching states (V0-V7) in a voltage state (V1-V6) is switched in which the electrical voltage is provided, characterized in that the inverter ( 10 ) is switched by means of a first switching state (V0-V7) within the pulse width modulation period (T) and a last switching state (V0-V7) within the pulse width modulation period (T) in one of the voltage states (V1-V6). The method of claim 1, wherein the first and last switching states (V0-V7) are identical within a pulse width modulation period (T). Method according to claim 1 or 2, wherein the inverter ( 10 ) is switched within the pulse width modulation period (T) in a second voltage state (V1-V6), in which the switch positions of the switch (S) of at least two phases of the inverter ( 10 ) differ from the switching states (V1-V6) of the first voltage state (V1-V6) in comparison with the switching positions of the switches (S). Method according to claim 3, wherein the inverter ( 10 ) is switched within the pulse width modulation period (T) in a third voltage state (V1-V6), in which the switching positions of the switch (S) only one phase of the inverter ( 10 ) of the respective switching positions of the switch (S) of the switching states (V1-V6) of the first voltage state (V1-V6) and the second voltage state (V1-V6) differ. The method of claim 1 to 4, wherein within the pulse width modulation period (T) only one of the voltage-free switching switching states (V0, V7) is switched. Method according to claim 5, wherein the de-energized switching state (V0, V7) is selected such that when switching between the switching states (V0-V7) within the pulse width modulation period (T) only the switches (S) of a phase of the inverter ( 10 ). Method according to one of claims 1 to 6, wherein the switching states (V0-V7) within the pulse width modulation period (T) are connected in series such that when switching between the switching states (V0-V7) only the switches (S) of a phase of the inverter ( 10 ). Method according to one of claims 3 to 7, wherein between the first voltage states (V1-V6) and the second voltage states (V1-V6) in each case a voltage-free switching switching state (V0, V7) is switched. Method according to one of claims 1 to 8, wherein a plurality of switching sequences for different voltage space pointer and current space pointer are predefined and are selected depending on the voltage space pointer and / or current space pointer to be set. Method according to claim 9, wherein the switching sequences depend on an input voltage of the inverter ( 10 ), a rotational frequency of the voltage space vector (V *) and / or a rotor position of the electric machine ( 14 ) to be selected. The method of claim 9 or 10, wherein the sequences are stored in a map. Method according to one of claims 9 to 11, wherein the switching sequences in dependence of a resulting load distribution of the inverter ( 10 ), a phase shift between the voltage space vector (V *) and the current space vector (I *), resulting in a fluctuation in the input voltage of the inverter ( 10 ), a resulting fluctuation of the output current of the inverter ( 10 ), resulting losses of a DC link of the inverter ( 10 ), a resulting vibration of the driven electrical load ( 14 ) and / or a resulting noise of the driven electrical load ( 14 ) are predefined for different voltage space and current space hands. Method according to one of claims 1 to 12, wherein the switching states (V0-V7) of the pulse width modulation period (T) for an angular range ( I - VI ) of the voltage space vector (V *) on the basis of a pulse width modulation period (T) of a reference angle range ( I ). Contraption ( 18 ) for driving an inverter ( 10 ), in particular for driving an electrical machine ( 14 ), where the inverter ( 10 ) comprises a plurality of components (S, D) formed by a plurality of controllable switches (S) and a corresponding plurality of freewheeling diodes (D) and connected thereto, a polyphase electric current (IU, IV, IW ), in particular around the electrical machine ( 14 ) to supply multiphase with electric current, with a control unit ( 18 ), which is adapted to the inverter ( 10 ) in such a way that the inverter ( 10 ) assumes a plurality of successive switching states (V0-V7) of the switches (S) in order to provide a voltage in the form of a voltage space vector (V *), one of the switching states (V0-V7) within a pulse width modulation period (T) controlling the inverter ( 10 ) in a voltage-free switching switching state (V0, V7) and one of the switching states (V0-V7) within the pulse width modulation period (T) the inverter ( 10 ) switches to a voltage state (V1-V6) to provide the electrical voltage (V), characterized in that the control device ( 18 ) is further adapted to the inverter ( 10 ) by means of a first switching state (V0-V7) within the pulse width modulation period (T) and a last switching state (V0-V7) within the pulse width modulation period (T) in one of the voltage states (V1-V6) to switch. 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 14.

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