DE102015201543A1 - Control method for standstill assurance of an electrical machine - Google Patents

Abstract

The present invention relates to a method for driving an inverter (2, 5) which is designed to supply an electrical machine (1), in particular an electric machine (1) in a drive train of a vehicle, with the following steps: a) detecting at least one standstill signal for the electric machine (1) and b) outputting a first and a second drive signal to the inverter (2, 5), wherein - the first drive signal comprises a signal for Nichtbestromen the electric machine (1), in particular a signal to Generating an inverter lock (WRS) and / or an active short circuit (AKS) of the electric machine (1), and - the second drive signal comprises a signal for generating a voltage vector (Ures) and / or a pulse width modulation (PWM).

Description

The present invention relates to a method for driving an inverter at a requested and / or detected standstill of an electric machine, in particular an electric machine in a drive train of a vehicle, wherein the inverter is adapted to energize the electric machine.

For powering an electrical machine usually an inverter, in particular a converter or a six-pulse bridge is used. Inverter switching units, by means of which the electrical voltage is applied to the electric machine, are thereby operated digitally and alternately an operating voltage in positive and negative directions is applied to supply terminals of the electrical machine. In order to be able to apply voltages deviating from the operating voltage, the inverter switching units are controlled in such a way that, on average, a desired voltage is applied to the electrical machine. The electric current that results according to this voltage is limited by the inductance of the electrical machine. In this case, the current in the electric machine begins to oscillate in such a method according to the switch positions of the inverter to a mean current. This commutation of the current is usually referred to as harmonics of the inverter, which can lead to problems in a requested vehicle standstill.

In the case of a requested vehicle standstill, it is known that undesired power transmission by the electric machine, in particular the generation of a torque above a predetermined safety threshold, must be prevented. For this purpose, in the prior art as a monitoring measure, the electric current flowing through the electric machine is detected and compared with a threshold under which the torque is assumed safe. In the inverter operation described above, however, it is a known problem that a measuring device that detects the current in the electrical machine at predetermined, randomly defined times, instead of the sought average current detects a deviating, distorted by the harmonics current. This in turn can lead to an unwanted start-up even if a requested or recognized standstill of a vehicle operated by an electric machine occurs.

However, such unintentional startup of a vehicle from standstill can endanger people who are in the vicinity of the vehicle. If, for example, an electrically driven bus stops at a stop and the driver does not apply the parking brake, even slight torques, for example, only 10 Nm, on the gear train suffice for the bus to set slowly and imperceptibly in motion for the driver.

Therefore, in the current monitoring of a stationary vehicle's electrical machine, it must be taken into account that, on the one hand, a functional safety risk analysis may yield a relatively low current limit, such as 8 A, that already corresponds to a dangerous condition. On the other hand, any measurement errors may cause this current limit to be exceeded without a dangerous state of the electrical machine being at standstill. Such measurement errors may occur in particular due to the harmonics of the inverter due to tolerances of the current sensor, such as due to a current drift up to 5 A in a temperature interval and / or during the lifetime, or due to the effects of a control on the zero torque M = 0 Nm , Without further precautions, this conflict can only be resolved either to the detriment of security or to the detriment of the system's availability, d. H. a reliable identification of a dangerous condition against a possible misdiagnosis with a better availability of the system is considered.

From the prior art, for example the publication DE 10 2010 053 624 A1 , a vehicle and a method for operating a vehicle with an inverter controlled by an electric motor is known, wherein upon detection of a dangerous condition or for disengaging or during gear change, the inverter receives a shutdown signal from a controller. This shutdown signal causes the powered by the inverter stator winding of the electric motor is de-energized. The controller generates the shutdown signal in response to values sensed by vehicle state sensors and / or entered via input means. To increase security, it is additionally proposed in this publication that, upon receipt of the shutdown signal, no further pulse width modulated control signals should be output.

In the publication EP 1 036 936 A1 is a device for monitoring a starting device in a motor vehicle with an electric machine serving as a starter and generator, an inverter for converting the current generated or required in the electric machine and a control unit for controlling the operation of the unit consisting of the electric machine and the inverter disclosed in response to input signals, the control unit also at not in operation vehicle is activated at intervals. In order to prevent inadvertent departure of the vehicle as a result of this activation, it is proposed in this document to use an additional control that controls the inverter in dependence on vehicle operating information such. B. a speed signal of the motor and a clutch actuation signal or a P / N signal of an automatic transmission, activated or deactivated.

In the event that the deactivation of the inverter or the interruption of the power supply of the electric machine should fail despite a requested vehicle standstill, such as a malfunction in the responsible electronics, but also in the known from the prior art devices, an unwanted startup the electrical machine occur.

The present invention is therefore based on the object, a method for controlling an inverter, which supplies an electric machine with electric current, indicate which at a detected and / or intentional standstill of a vehicle driven by the electric machine reliably an unwanted start of the electric machine prevented.

This object is achieved by a method for driving an inverter according to claim 1.

Although the invention will be described below to illustrate the method according to the invention in relation to a vehicle, the method can be applied correspondingly to any device which can be set in motion by an electric machine.

According to the invention, a method is provided with which an inverter is controlled, wherein the inverter is designed to power an electric machine, in particular an electric machine of a vehicle. Among other things, the method according to the invention comprises the step of the standstill detection according to the invention, whereby at least one standstill signal for the electrical machine is detected. In order to ensure a reliable standstill of the electric machine, in a further step, a first and a second drive signal to the inverter is output, wherein the first drive signal comprises a signal for Nichtbestrom the electric machine, in particular a signal for generating an inverter lock and / or active electrical short circuit of the electric machine. In contrast, the second drive signal additionally comprises a signal for generating a voltage vector on the electric machine and / or a pulse width modulation, ie. H. a particular voltage pulse pattern, which is delivered to the designated inverter switching units, in particular switches, semiconductors or power semiconductors.

In this case, causes the first drive signal, for example, the inverter lock, d. H. the opening of all inverter switching units, a rapid interruption of the power supply of the electric machine. The first drive signal thus makes it possible, in the standstill detection instead of a control to a torque equal to 0 Nm or to a current equal to 0 A, the switching off of the electrical machine by the inverter simply. Due to the resulting omission of the clocking of the inverter also eliminates the above-mentioned harmonics, so that the current can now be detected without disturbing distortions. As a result, the limits for current monitoring here can be drawn much narrower, whereby the initially mentioned conflict between the safety and the availability of the electric machine is at least partially reduced.

The additionally and independently of the first drive signal output second actuation signal causes according to the invention that in the case of a missed or failed first drive signal, an automated control of the inverter for generating a pulse width modulation or a voltage vector takes place, which in turn leads to a shutdown of the electric machine.

In this case, the second drive signal can be designed, for example, such that the pulse width modulation or the voltage vector causes the application of a resulting voltage in one direction, which does not lead to any effective torque of the electric machine.

Alternatively, by means of the pulse width modulation or the voltage vector, such a high voltage can be generated at the electric machine that it clearly contradicts the desired standstill signal, which in turn results in an emergency shutdown of the electrical machine. For this purpose, in particular a safety unit can be provided, which is activated by the presence of a detectably high voltage on the electric machine. It may even be sufficient to output only a signal for applying a constant operating voltage to an inverter-switching unit pair. Pulse width modulation is not necessary in this case. Other options of a suitable Pulse width modulation or a suitable voltage vector are given below.

Advantageously, therefore, the inventive method reliably prevents unwanted startup of the electric machine in the presence of a standstill signal, d. H. Even if the specially provided for this purpose first drive signal for Nichtbestromen the electrical machine fails for any reason, fails or not recognized or can not be implemented by the inverter.

In a further advantageous embodiment, two parallel, d. H. independent, drive lines for the inverter provided. Since in this embodiment, the first and the second control signal are transmitted in each case by means of a separate control line to the inverter, there is an increased robustness and flexibility of the inverter control according to the invention. It can also be provided more, but also less than two control lines for outputting the control signals according to the invention.

Preferably, the first drive signal and the second drive signal become parallel to each other, i. H. At least partially temporally overlapping, but preferably at the same time, output to the inverter, so abut in the presence of at least one standstill signal both control signals to the inverter. This has the advantage that both the first and the second control signal are available to the inverter for the entire duration of the standstill detection according to the invention. In particular, in the case of a malfunction in connection with a control signal, the respective other control signal from the inverter can be automatically converted at any time, so that the inverter secures the standstill detected according to the invention without any delay.

Alternatively, the two drive signals can also be output one after the other, for example immediately following one another, in particular alternately, to the inverter. In this case, in particular, the same drive line can be used for the two drive signals.

In a preferred embodiment, the inverter has a selection unit, which monitors the two drive signals according to the invention and is designed such that it passes on either only the first or only the second drive signal for driving the inverter, and thus leads to its actual implementation in the inverter. This has the advantage that the two different control signals can be present at the same time, preferably for the entire duration of the standstill detection, without leading to a contradictory control of the inverter switching units. In particular, the selection unit can pass on the control signal selected by it directly to the inverter switching units or to an optionally provided additional safety unit provided for the safety shutdown of the electrical machine.

Which of the two control signals is selected by the selection unit and to which conditions a corresponding preference regulation is linked may vary depending on the apparatus and functional configuration of the respective application. Since both the first and the second drive signal are suitable for the purpose of standstill protection, the two drive signals in the actual implementation in the inverter are basically mutually replaceable. In other words, the selection unit can also be designed, as a rule, d. H. if no malfunctions occur and thus both drive signals are available to pass on the second drive signal for actual conversion and to ignore the first drive signal. Further examples and preferred embodiments with regard to the selection unit are given below.

According to a preferred embodiment, the signal contained in the second drive signal for generating the pulse width modulation comprises a signal for applying a resultant electrical voltage U _res to the electric machine. This means that the pulse width modulation leads to a time average U _{res of} the voltage at the electrical power supply terminals of the electric machine, which results in the case of several inverter switching unit pairs from the vector sum of the average output voltages at the individual inverter switching unit pairs. By means of such a pulse width modulation, the electric machine is impressed with a suitable voltage or current vector, which represents a technically different and therefore independent measure for standstill assurance in addition to the non-current driving according to the first activation signal. In particular, the pulse width modulation vector U _{res may have} a desired, preferably as high, modulation as possible. The resulting voltage U _res may change in direction and / or magnitude as a function of time or be time-independent.

As an alternative to applying a resulting voltage U _res, it is also possible to generate a pulse width modulation which results in a short circuit of the supply terminals of the electrical machine.

In an advantageous further development of the above embodiment, the signal for applying the resulting voltage U _{res is} a signal for applying the resulting electrical voltage U _res in the direction of a magnetic field of the electric machine. As a rule, this is the direction of the rotor flux of the electric machine, ie the field-forming direction, which is referred to below as the d-direction. As a result of a resulting voltage U _res , which lies on the d-axis of the electric machine, sets in the electric machine, a detectable current without an effective torque. In a rotating rotor, it is possible to rotate the voltage vector U _res accordingly.

This method also has the advantage that the electrical machine is supplied with a non-negligible resulting voltage, without causing the driven by the electric machine vehicle in motion. In particular, the amount of the resulting voltage U _{res can} basically be arbitrarily high.

Furthermore, both in this exemplary embodiment and in other embodiments with the generation of a voltage vector can be advantageous if the resulting voltage U _{res is} sufficiently high for the activation of an additional safety shutdown of the electric machine with independent means known to those skilled in the art, for example address predetermined _threshold voltage _threshold U _threshold .

The direction of the magnetic field of the electrical machine, in particular the d-direction, can also be determined, for example, by means of a magnetic field sensor, a rotor position sensor and / or a model calculation. A combination of two or even three of these or other techniques results in increased accuracy and reliability of the method of the invention.

According to a further advantageous embodiment, the signal for generating the pulse width modulation and / or a voltage vector can in particular also comprise a signal for generating a resulting electric current I _res in the electric machine. In the case of pulse width modulation, what has been said above with respect to the formation and the direction of the resulting voltage U _res also applies correspondingly with respect to the resulting current I _res . In this case, the amount of the resulting electrical current I _res is preferably selected so that it does not fall below a predetermined current _{threshold value} I _threshold . This can, as already mentioned, be used for a safety _{shutdown of} the electrical machine with additional _threshold- responsive means I responsive.

Preferably, in the method according to the invention, an electrical current I flowing in the electric machine is monitored by means of one or more current sensors, whereby upon reaching or exceeding a predetermined safety current _{threshold value} I, a safety _{shutdown of} the electrical machine takes place with the means known to the _person skilled in the art. This constitutes a standstill safeguard which is technically independent of the non-energizing according to the first activation signal. The safety shutdown preferably takes place by means of an additional independent security unit, for example spatially separated from other units, which monitors the one or more current sensors.

As an alternative or in addition to the monitoring of the current I flowing in the electrical machine, an electric current I flowing in the inverter, in particular in one or more inverter switching units, and / or one present in the inverter, in particular at one or more inverter switching units electrical voltage U are monitored by means of at least one current and / or voltage sensor. Upon reaching or exceeding a predetermined safety current _{threshold value} I _threshold or a predetermined safety voltage _{threshold value} U _threshold , a safety _{shutdown of} the electrical machine can take place.

In the method according to the invention, the at least one standstill signal may further include a signal which transmits a request to stop the electrical machine. This stop request signal can z. B. by the disengagement in a vehicle, by the reading of a stop signal input device and / or by a zero torque request, M = 0, a hybrid coordinator are generated. The detection of such a signal in the standstill detection according to the invention has the advantage that it is not or at least not exclusively determined by the actual state of motion of the electrical machine or the vehicle. In particular, this prevents a standstill assurance being carried out despite a deliberate startup of the electrical machine.

Alternatively or additionally, the standstill detection according to the invention may comprise a signal which is generated as a result of the readout of a motion state sensor, which a detected current state of motion of the electric machine and / or a vehicle driven by this vehicle. As a result, the actual movement state is provided as a component of the standstill detection which is independent of the retention request. Among other things, this can be effected that a shutdown of the electric machine for standstill security is performed only at one / an actual or at least almost stationary electric machine or vehicle. In particular, by detecting such a signal, it can be prevented that the electric machine is switched off during operation or while driving. For such unclear requirements, it could, for example, then come without the described measure, when the electric machine is to remain in operation during disengagement.

In particular, rotational speed sensors for the rotational speed n of the electric machine, a transmission output shaft and / or a vehicle wheel, and / or speed sensors for the speed v of the vehicle can be used as motion state sensors. In these cases, it is particularly advantageous for the above reasons, if the corresponding motion- _{dependent standstill} signal is generated only when reaching or _{falling below} a predetermined threshold n _threshold for the speed n and / or a predetermined threshold v _threshold for the speed v.

In general, in the method _according to the invention, the one and / or another standstill signal can be generated upon reaching or _{falling below} , or when a predetermined threshold value x is reached or exceeded for a parameter x of the electrical machine and / or of the vehicle driven by the electric machine. As a result, a state which can be characterized by the parameter x is provided as a component of the standstill detection which is independent of the holding request. In addition, states in an interval, which is different from zero if necessary, of the parameter x are made accessible for the standstill backup according to the invention.

In a preferred embodiment, the output of the two drive signals according to the invention is terminated as soon as or after no standstill signal is detected. As a result, the power supply of the electric machine is automatically resumed, and the electric machine is immediately ready for use.

In an advantageous development of this embodiment, at least one standstill signal is generated upon reaching or exceeding a predetermined threshold value x _threshold for a parameter x. However, this standstill signal is only canceled again when the parameter x _{falls below a} threshold value (x _{threshold -x hyst} ) reduced by a predetermined hysteresis value x _hyst . The same applies correspondingly reversed in the cases when a standstill signal was generated when reaching or falling below a parameter x. For example, the _{standstill signal generated} upon reaching or _{falling below} the threshold value n _threshold for the speed n and / or the threshold value v _threshold for the speed v is canceled only when the speed n or the speed v respectively increased by a predetermined hysteresis threshold (n _threshold + n _hyst ) or (v _threshold + v _hyst ) exceeds. The provision of such Parameterhysterese prevents an undesirable off and turning on of the electric machine, when a critical parameter for this varies to its threshold x x _schwell around.

In the method according to the invention, at least one first standstill signal and a second standstill signal independent of it are preferably detected. This means a stricter requirement for the inventive standstill detection in comparison to the cases also encompassed by the invention, in which only a single standstill signal is detected. The detection of at least two independent standstill signals therefore leads to a more precise distinction between a standstill with backup demand and a state in which no standstill backup is required. For example, an abovementioned hold request signal can serve as a first standstill signal and a second standstill signal can be generated by reading a motion sensor. For increased precision of the standstill detection and three or more independent standstill signals can be detected, for. B. when in the example mentioned various stop request signals or different motion sensors are used.

Preferably, the above-mentioned selection unit may be configured such that, in the presence and / or recognition of the first activation signal according to the invention, it transmits only the first activation signal for driving the inverter and ignores the second activation signal according to the invention. In this embodiment, therefore, the power supply of the electric machine is immediately suppressed in a standstill detection as a rule, ie in the presence of the first drive signal. In this case, the signal contained in the second drive signal for generating a pulse width modulation and / or a voltage vector is not passed on to the inverter switching units and is therefore not effective. Such a preference rule has the The advantage of a usually simple and rapid shutdown without further intermediate steps, by the power supply to the electric machine is immediately stopped.

In an advantageous further development of this embodiment, the selection unit is designed in such a way that, in the absence, failure or other malfunction of the first activation signal, it passes on the second activation signal for controlling the inverter in its place. As a result, a reliable standstill assurance is ensured even in the case of a failure of the first drive signal by means of the second drive signal.

As an alternative to the inverter lock described above, the first drive signal may also include a signal for generating an active electrical short circuit of the electric machine. The active short circuit of the electric machine may be effected, for example, by short-circuiting two or more inverter switching units, thereby short-circuiting the associated power supply lines of the electric machine. As a result, not only the power supply of the electric machine is suppressed, but it can be further degraded internal currents and voltages between the power supply lines of the electric machine, whereby the electric machine can be brought quickly to a standstill.

According to a further preferred embodiment, the inverter has six inverter switching units, which form three inverter-switching unit pairs each having an outer conductor / phase conductor and an inner conductor / neutral conductor for generating a three-phase current. In this case, the active short circuit of the electrical machine can preferably be generated by short-circuiting the three outer conductors / phase conductors or the three inner conductors / neutral conductors and opening the respective remaining three inverter switching units. With this technique, the internal currents and voltages in the electric machine are broken down particularly effectively, which in turn leads to a rapid and complete stoppage of the electric machine.

Further advantages and advantageous embodiments are defined in the subclaims, the description and the drawings.

In the following the invention will be described with reference to embodiments illustrated in the drawings. The embodiments are purely exemplary in nature and do not specify the scope of the application. This is defined solely by the appended claims. The features described below on the basis of exemplary embodiments can also be used in combinations other than those explicitly mentioned in the context of the invention.

Show it:

1 a schematic diagram of an inventive control of an electric machine by an inverter by means of an inverter lock;

2a a schematic diagram of an inventive control of an electric machine by an inverter by means of a suitable pulse width modulation;

2 B a schematic representation of the electrical switching states of the inverter switching units in an inventive control after 2a ;

2c a schematic vector diagram for a voltage applied to the electric machine voltage U _res in a drive according to the invention 2a and 2 B ;

3a a flowchart of a first embodiment of the method according to the invention and

3b a flowchart of a second embodiment of the method according to the invention.

Hereinafter, the same or equivalent elements are denoted by the same reference numerals.

1 shows a system in an exemplary schematic circuit diagram 100 with an electric machine 1 and one the electric machine 1 energizing inverter 2 , where the system 100 is designed to carry out the driving method according to the invention. In the illustrated embodiment, an electric machine is located in a drive train of a vehicle, in particular an electric vehicle or a hybrid vehicle 1 with associated on-board electronics, the system 100 but also for other uses of the electric machine 1 is usable. The electric machine 1 may be configured in particular as any powered with DC or AC electromechanical transducer.

As in 1 pictured is the electric machine 1 an induction machine with power supply lines 11 . 12 and 13 that are electrically over supply terminals 14 . 15 and 16 with the inverter 2 are connected, wherein the supply terminals are illustrated schematically as nodes.

The inverter 2 also has six inverter switching units 21 to 26 for energizing the electric machine 1 on, the three inverter switching unit pairs 21 - 22 . 23 - 24 and 25 - 26 form. The inverter switching units 21 to 26 can be designed in particular as switches, semiconductors or power semiconductors. A supply source 20 the electric machine 1 outputs an operating voltage U _zk , so that at the supply _terminals 14 . 15 and 16 Supply voltages U, V and W according to the respective switch positions of the inverter-switching unit pairs 21 - 22 . 23 - 24 and 25 - 26 issue.

Further shows 1 an arithmetic unit 4 , which is designed to perform a standstill detection. For this purpose, the arithmetic unit 4 via a first signal line 41 with a control unit (not shown), in particular an on-board computer, and via a second signal line 42 with a motion condition sensor 6 , in particular a rotary encoder, the electric machine 1 connected. According to the invention the Recheneiheit 4 by means of the signal lines 41 and 42 at least one standstill signal. In the present example, a zero torque request signal M = 0, that is, a stop signal based on a stop request, from an on-board electronics, in particular from a hybrid coordinator, via the signal line 41 to the arithmetic unit 4 be transmitted. To determine if a movement of the electric machine 1 present, can continue via the signal line 42 a speed n of the electric machine 1 to the arithmetic unit 4 be transmitted. For this example, the signal of the encoder 6 be tapped. Preferably, the arithmetic unit leads 4 a comparison of the obtained speed value n with a predetermined threshold n _threshold , which defines a standstill _interval for the speed n, and generates / detects a standstill _{signal when falling below} this threshold. An example of this will be given below with reference to 3 described. Alternatively or in addition to the speed n of the arithmetic unit 4 also other state parameters x of the electric machine 1 or the vehicle.

Furthermore, the arithmetic unit 4 designed in the case of standstill detection, the drive signals for the inverter according to the invention 2 issue. These are in 1 for example, two parallel independent drive lines 51 and 52 intended. By means of the control line 51 a first drive signal is output, which in the present example represents an inverter lockout signal (WRS). By means of the control line 52 a second drive signal is output, which in the present case represents a signal for generating a suitable pulse width modulation (PWM) with modulation.

Further shows 1 a selection unit 5 containing the two drive signals WRS; Reads PWM and makes a preference decision as to whether the first or the second drive signal WRS; PWM in the inverter 2 actually be implemented. In this case, the selection unit 5 , as in 1 shown to be formed as a separate unit, but it is also common, the selection unit 5 functional as part of the inverter 2 train.

Furthermore, the selection unit 5 have an electronic logic module, which performs a logical rounding of the two drive signals WRS, PWM and in the presence of both control signals WRS, PWM only one of them to the inverter 2 passes. In this case, usually the first drive signal WRS, selected as the main signal and the second drive signal PWM only used as a hedge.

The selection unit 5 In the example shown, the WRS signal is sent by means of the control lines 3 to the inverter switching units 21 to 26 for implementation. In doing so, the in 1 at the entrance of the selection unit 5 Simultaneously existing PWM signal not to the control lines 3 passed on and is therefore not effective.

Represents the selection unit 5 however, a malfunction in the WRS signal fixed, the PWM signal to the inverter switching units 21 to 26 passed on and is thus effective. An example of this is in the 2a to 2c and will be described below.

Im in 1 The example shown generates this via the control lines 3 transmitted WRS signal, the inverter lock, ie a digital release of the inverter 2 by opening all six inverter switching units 21 to 26 , Alternatively or additionally, the first drive signal could be a signal for generating an active electrical short circuit (AKS) of the electrical machine 1 or another signal to shut off the power supply to the electrical machine 1 include. In the illustrated system 100 For example, an AKS could be by closing the upper inverter switch units 21 . 23 and 25 with lower inverter switching units open 22 . 24 and 26 or vice versa.

Furthermore, in 1 a security unit 8th shown when exceeding safety-relevant parameters, in particular in the presence of a in the electrical machine 1 and / or E-machine side in the inverter 2 flowing phase current I, by means of one or more current sensors 7 is detectable, can initiate a shutdown of the electric machine. On the operation of the security unit 8th and the safety-relevant parameters will be discussed in more detail in particular with reference to the other figures.

Preferably, the additional security unit 8th apparatusically separate from the other electronic units, in particular from the arithmetic unit 4 and the selection unit 5 , arranged to be unaffected, for example, in the event of overheating of one of the remaining electronic units. It also monitors the safety unit 8th preferably also the control lines 3 in terms of malfunction and can also in an emergency, a safety shutdown of the electric machine 1 cause.

2a schematically shows a section of the system 100 out 1 , In the illustrated drive example, a suitable pulse width modulation PWM is implemented according to the second drive signal for standstill assurance according to the invention. As described above, however, this is done at the output of the arithmetic unit 4 output PWM signal is not effective when the first drive signal is operational.

However, if the first drive signal WRS fails due to a malfunction or an error, the second drive signal PWM is automatically sent to the inverter 2 passed. In the 2 illustrated PWM control then causes the example in 2 B shown electrical switching states on the inverter switching units 21 to 26 , Here are the at the upper inverter switching units 21 . 23 and 25 in 2a corresponding voltages as UH, VH and WH respectively and to the lower inverter switching units 22 . 24 and 26 applied voltages as UL, VL and WL. 2 B shows the mentioned switching states during a PWM period T _pwm , which repeats as a pulse train during the entire duration of the PWM generation. As a result, this pulse width modulation leads in each case with a corresponding voltage U, V and W at a DC link capacitance to a mean voltage U _U , U _V and U _W at the respective supply terminals 14 . 15 and 16 the electric machine 1 ,

The vectorial sum of the mean voltages U _U , U _V and U _W, in turn, gives a resultant voltage U _res in a d-direction, which corresponds to the rotor flux of the electrical machine 1 corresponds, ie in the direction of the magnetic field of the electric machine 1 , as in 2a indicated. As a result, an easily recognizable current I _{res flows} , which in turn flows from the safety unit 8th or the current sensor 7 is detectable, but does not generate effective torque. For the generation of a torque, however, a voltage component would be required in a direction perpendicular to the magnetic field direction q-direction. In the case of a residual rotation of the machine 1 and thus a rotating magnetic field of the electric machine 1 The U _res pointer can also be guided in the d direction. The direction of the magnetic field can be z. B. by means of a rotor field aligned position sensor or a model calculation can be determined.

Furthermore, it is provided that, if the adjusting current I _res exceeds a predetermined safety current _threshold I threshold, from the arithmetic unit 4 and / or the security unit 8th an active short circuit AKS of the electric machine 1 or another safety function is performed, which is to shut off the electrical machine 1 leads. This is as fast as you like, because of the in 2c shown PWM pointer, the current I _{res increases} in the electric machine 1 almost immediately.

As an alternative to the illustrated PWM pointer, it is also possible by means of the second activation signal according to the invention to apply a pulse width modulation which forms an electrical short circuit of the electrical machine 1 result, for example, by alternately all upper switching units 21 . 23 and 25 closed / opened and all lower switching units 22 . 24 and 26 be opened / closed.

As an alternative to the PWM signal, the second drive signal could also be a signal for generating a detectable voltage vector U _res on the electric machine 1 without pulse width modulation, for example by the time-independent application of the operating voltage U _zk on the inverter-switching unit pair 21 - 22 at the open remaining inverter-switch unit pairs 23 - 24 and 25 - 26 , represent. This would also result in a detectable voltage / current that would result in an immediate emergency shutdown of the electrical machine at a requested stall.

Hereinafter, the driving method according to the invention will be described with reference to exemplary flowcharts in FIG 3a and 3b explained in more detail.

The flowchart in 3a illustrates an example of a standstill fuse according to the invention, wherein as a rule the inverter lock WRS and in case of a functional error in the WRS generation, a suitable pulse width modulation PWM be generated. The method may be, for example, a system 100 out 1 and 2a be executed, the associated description also applies here.

As 3a The standstill detection is defined by the detection of two independent standstill signals. The first stop signal "stop desired" can be generated in particular by the requirement of a torque equal to 0 Nm by the hybrid coordinator of a hybrid vehicle. The second standstill signal is generated _{when falling below} a threshold for the detected speed n of the electric machine, for example, n _threshold = 300 revolutions / min. If both standstill signals are detected in this example, the inverter lock WRS is generated. Parallel to the signal "turn on WRS" according to the invention is the signal "PWM turn on" before and is selected by the selection unit 5 then implemented if the check "WRS effective?" results in the detection of a WRS signal or WRS generation malfunction. If one of the standstill signals disappears, the standstill protection, ie the inverter lock or the standstill backup PWM, is canceled. The process is automated and runs as in 3a shown, cyclically.

In 3b is the example 3a Added a further condition to cancel the WRS or the standstill backup PWM. In this case, this condition further requires that the rotational speed n exceeds a threshold value increased by a hysteresis _value n _hyst = 100 revolutions / min. As a result, a switching back and forth of the control _{signals according to} the invention is avoided at a threshold n n = 300 revolutions / min fluctuating speed n.

Overall, in a standstill detection of an electric machine energized by an inverter, the output of a first, directly to the Nichtbestromen of the electric machine directed drive signal and a second, directed to the generation of a suitable pulse width modulation and / or a suitable voltage vector driving signal two technically different and independent Because of the mutual substitutability of the two drive signals in case of possible malfunctions thus a reliable standstill assurance against accidental start-up of the electric machine is guaranteed.

LIST OF REFERENCE NUMBERS

100

System that carries out the method according to the invention

1

electric machine

2

inverter

3

Control cables of the inverter switching units

4

computer unit

5

selector

6

encoders

7

Current or voltage sensor (s)

8th

additional independent security unit

11 to 13

Power supply lines of the electric machine

14 to 16

Supply terminals of the electric machine

20

Supply source of the electric machine

21 to 26

Inverter switching units

41, 42

Standstill signal lines

51

Drive line for the first drive signal

52

Drive line for the second drive signal

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102010053624 A1 [0006]
• EP 1036936 A1 [0007]

Claims (20)

Method for controlling an inverter ( 2 . 5 ), which is designed to be an electrical machine ( 1 ), in particular an electrical machine ( 1 ) in a drive train of a vehicle, comprising the following steps: a) detecting at least one standstill signal for the electric machine ( 1 ) and b) outputting a first and a second drive signal to the inverter ( 2 . 5 ), wherein - the first drive signal is a signal for non-energizing the electric machine ( 1 ), in particular a signal for generating an inverter lock (WRS) and / or an active short circuit (AKS) of the electrical machine ( 1 ), and - the second drive signal comprises a signal for generating a voltage vector (U _res ) and / or a pulse width modulation (PWM). Method according to Claim 1, in which the two activation signals are sent to the inverter (parallel to one another, preferably simultaneously). 2 . 5 ). Method according to Claim 1 or 2, in which the signal for generating the pulse width modulation (PWM) comprises a signal for applying a resulting electrical voltage (U _res ). Method according to Claim 3, in which the application of a resultant electrical voltage (U _res ) in the direction of a magnetic field (d-direction) of the electrical machine ( 1 ) he follows. Method according to Claim 4, in which the direction of the magnetic field (d-direction) of the electric machine ( 1 ) is determined by means of a magnetic field sensor, a rotor position sensor and / or a model calculation. Method according to one of the preceding claims, in which the generation of the voltage vector (U _res ) or the pulse width modulation (PWM) generates a resulting electrical current (I _res ) in the electrical machine ( 1 ), wherein preferably the amount of the resulting electric current (I _res ) does not fall below a predetermined current _{threshold value} (I _threshold ). Method according to one of the preceding claims, wherein a in the electrical machine ( 1 ) flowing electrical current (I) by means of at least one current sensor ( 7 ) is monitored and on reaching or exceeding a predetermined safety current _threshold (I _threshold ) a safety _{shutdown of} the electric machine ( 1 ) preferably by means of an additional independent security unit ( 8th ) he follows. Method according to one of the preceding claims, wherein a in the inverter ( 2 . 5 ), in particular in one or more for energizing the electric machine ( 1 ) inverter switching units ( 21 - 26 ), flowing electrical current (I) and / or one in the inverter ( 2 . 5 ), in particular in one or more for energizing the electric machine ( 1 ) inverter switching units ( 21 - 26 ), present electrical voltage (U) by means of at least one current and / or voltage sensor ( 7 ) is monitored and upon reaching or exceeding a predetermined safety current _threshold (I _threshold ) or a predetermined safety voltage _threshold (U _threshold ), a safety _{shutdown of} the electric machine ( 1 ) preferably by means of an additional independent security unit ( 8th ) he follows. Method according to one of the preceding claims, wherein the at least one standstill signal a desire / command for stopping the electric machine ( 1 In particular, this is generated by the disengagement in a vehicle, by the reading of a stop signal input device and / or by a zero torque request (M = 0) of a hybrid coordinator. Method according to one of the preceding claims, wherein the at least one and / or another standstill signal comprises the step of reading out a motion state sensor ( 6 ), which detects a current state of motion of the electric machine ( 1 ) and / or a vehicle, wherein the movement condition sensor ( 6 ) in particular as a speed sensor for the rotational speed (n) of the electric machine ( 1 ), a transmission output shaft and / or a wheel of a vehicle and / or as a speed sensor, which detects the speed of a vehicle (v) is formed. Method according to one of the preceding claims, _wherein the at least one and / or another standstill _signal upon reaching or _{falling below} a predetermined threshold value (x _threshold ) for a parameter x of the electric machine ( 1 ) and / or a vehicle, in particular on reaching or _{falling below} a predetermined threshold value (n _threshold ) for the speed (n) and / or a predetermined threshold value (v _threshold ) for the speed (v) is generated.  Method according to one of the preceding claims, further comprising the step: c) canceling the drive signals output in step b) if at least one of the standstill signals detected in step a) is canceled again. Method according to claims 11 and 12, in which the at least one and / or the further standstill signal in step c) is canceled by the fact that / when the parameter x increases / decreases by a predetermined hysteresis value (x _hyst ) threshold value (x _{threshold /} x _hyst ) or (x _threshold - x _hyst ) exceeds / _falls below, in particular that / when the rotational speed (n) and / or the velocity (v) increases the respective threshold value (n _hyst ) increased by a predetermined hysteresis value (x _hyst ) + n _hyst ) or (v _threshold + v _hyst ).  Method according to one of the preceding claims, wherein in step a) at least a first standstill signal and a second, from the first independent, standstill signal are detected. Method according to one of the preceding claims, in which the inverter ( 2 . 5 ) a selection unit ( 5 ), which monitors the first and the second drive signal and is configured such that it only one of the two drive signals for driving the inverter ( 2 ), in particular to one or more for energizing the electrical machine ( 1 ) inverter switching units ( 21 - 26 ) and / or to a safety shutdown of the electrical machine ( 1 ) additional independent security unit ( 8th ). Method according to Claim 15, in which the selection unit ( 5 ) is configured in such a way that, in the presence / recognition of the first control signal, it is used to control the inverter ( 2 ) and ignores the second drive signal. Method according to Claim 15 or 16, in which the selection unit ( 5 ) is configured such that, in the absence of the first drive signal, the second drive signal for driving the inverter ( 2 ) passes on. Method according to one of Claims 15 to 17, in which for energizing the electric machine ( 1 ) at least one, preferably two or more, inverter switching units ( 21 - 26 ) is provided and the inverter lock (WRS) by opening the at least one, possibly all existing, inverter switching units ( 21 - 26 ) is produced. Method according to one of Claims 15 to 18, in which the inverter ( 2 ) at least two inverter switching units ( 21 - 26 ) for energizing the electrical machine ( 1 ) and the active short circuit (AKS) of the electrical machine ( 1 ) by short-circuiting the at least two inverter switching units ( 21 - 26 ) is produced. Method according to Claim 19, in which the inverter ( 2 ) six inverter switching units ( 21 - 26 ), the three inverter switching unit pairs ( 21 - 22 . 23 - 24 . 25 - 26 ) each of an outer conductor / phase conductor and an inner conductor / neutral conductor to generate a three-phase current, and the active short circuit (AKS) of the electric machine ( 1 ) by short-circuiting the three outer conductors / phase conductors ( 21 . 23 . 25 ) or the three inner conductors / neutral conductors ( 22 . 24 . 26 ) and the opening of the remaining three inverter switching units ( 22 . 24 . 26 ; 21 . 23 . 25 ) is produced.

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