DE102021127127A1 - Method for sensorless operation of a switched reluctance machine and system comprising at least one switched reluctance machine and at least one converter - Google Patents

Abstract

The invention relates to a method for sensorless operation of a switched reluctance machine and a system comprising a switched reluctance machine and a converter. A desired current value for applying at least one stator coil is determined by means of a speed controller based on a desired speed value and an instantaneous speed. At least one switch-on signal is determined by means of a current controller for at least one current phase based on a desired current value and an actual current value output by the converter and taking into account a relative rotor position. A phase current is then output by a driver circuit of the converter for at least one current phase to a stator coil as a result of the switch-on signal. The output phase current is regulated by the current controller between an upper and a lower switching threshold. The relative rotor position is determined based on an initial rotor position and/or a current rate of change of the output phase current between the upper and lower switching thresholds.

Description

FIELD OF THE INVENTION

The invention relates to a method for sensorless operation of a switched reluctance machine and a system comprising at least one switched reluctance machine and at least one converter.

TECHNICAL BACKGROUND

Switched reluctance machines include rotors with rotor teeth and stators with stator teeth. The stator typically includes electromagnetic coils that are arranged and set up according to multiple power phases. The number of current phases corresponds to the number of closed magnetic circuits that are required to cover a full revolution of the electrical angle. By sequentially energizing a suitable part of the stator coils, an electromagnetic field can be generated in such a way that a reluctance force is exerted on the rotor, which causes the rotor to rotate because it wants to align itself accordingly with the electromagnetic field.

A converter is used to correctly energize the current phases with regard to the rotor position with regard to the current amplitude and the switching times. The determination of the switch-on and switch-off times for at least one current phase is a prerequisite for a controlled movement of the rotor. In order to determine the switch-on and switch-off times, position sensors and speed sensors are usually used, by means of which the instantaneous position and the instantaneous speed of the rotor are detected. The detected variables are then supplied to the converter in a suitable manner for the underlying current control.

However, such position sensors and speed sensors require additional wiring and mechanical connections via the rotor shaft on the reluctance machine, as a result of which the respective reluctance machine has increased complexity and also increased costs. In addition, the sensors are exposed to the environment of the reluctance machine, whose environmental conditions are often harsh. This puts a lot of strain on the sensors. A failure of a sensor means that the current control can no longer be carried out. The machine is then generally unusable, resulting in unwanted downtime. Maintenance work is also usually complex and cost-intensive.

Alternative methods for determining position and speed are based on applying additional detection signals to the current phases of the reluctance machine (e.g. "pulse injection method"). The position and the speed of the rotor are then determined by evaluating the magnetic flux linkage and/or evaluating the inductance. Feeding in and evaluating these additional signals usually requires additional hardware, which in turn increases the effort and susceptibility to errors. The application of additional detection signals can also fundamentally result in increased interference, for example the generation of radio interference emissions or the generation of counter-torques, which increases the torque ripple. The underlying evaluation methods also have a comparatively high level of complexity and therefore place increased demands on the control technology. Another disadvantage is the increased technical effort involved in generating and detecting the additional signals.

The invention is therefore based on the technical task of creating a method for operating a reluctance machine that avoids additional external sensors and at the same time has a reduced complexity, in particular that does not require any additionally fed-in detection signals.

DESCRIPTION

The object is solved by the subject matter of the independent patent claims. Advantageous configurations are specified in the dependent patent claims and the following description, each of which can represent an aspect of the invention on its own or in (sub)combination. Individual aspects are explained with regard to methods, others with regard to devices. However, they are mutually transferable.

In accordance with one aspect, a method for sensorless operation of a multi-phase switched reluctance machine is provided. The switched reluctance machine is controlled by a converter.

The method comprises at least the step of determining a desired current value for applying at least one stator coil. The current setpoint is determined using a speed controller. The current setpoint is determined based on at least a speed setpoint and an instantaneous speed.

The method also includes the step of determining at least one switching signal by means of a current controller for at least one current phase. The switching signal is determined based on at least the desired current value and an actual current value output by the converter. A relative rotor position with respect to a rotation angle of an electromagnetic rotating field of the switched reluctance machine is preferably taken into account.

Furthermore, the method includes the step of outputting a phase current through a driver circuit of the converter for at least one current phase to at least one stator coil. The phase current is output as a result of the at least one switching signal. The output phase current is regulated by the current controller between an upper switching threshold and a lower switching threshold.

The relative rotor position is determined at least based on an initial rotor position and/or a current rate of change of the phase current output by the converter.

Since the phase inductance changes as a function of the rotor position, the rotation of the rotor means that the switching times for the subsequent switching cycle can be determined based on the output phase current. This is because the feedback from the changing phase inductance generally leads to varying rates of current change per switching cycle. In other words, the instantaneous phase inductance influences the change in the impressed current in a phase coil, which is why the current can have gradients that vary in terms of absolute value. This dependency also means that the switching times per switching cycle can be determined and adjusted accordingly.

In the case of the present method, the absolute rotor position does not have to be taken into account. Rather, the determination of a relative rotor position with respect to a rotation angle of an underlying electromagnetic rotating field of the reluctance machine is sufficient.

The regulation also benefits from the fact that the period length of the current regulation is very much shorter than a period length of the rotational speed of the rotor. In other words, the speed of the rotor changes only insignificantly during the switching cycles for applying the current phases of the reluctance machine. The method is then used to impress quasi-constant phase currents between corresponding switching thresholds, so that the instantaneous speed of the rotor can ultimately be adapted to a speed setpoint.

The method makes it possible to operate the reluctance machine without the need for position sensors or speed sensors for the rotor for the underlying control. As a result, the complexity of the reluctance machine together with the converter is reduced. The reluctance machine is operated without sensors. The method also does not require feeding additional detection signals into the underlying signal lines of the stator coils. As a result, the signal quality can advantageously be improved. In addition, the regulation is simplified. With regard to the regulation, the present method is based solely on the evaluation of the phase currents and/or the switching signals output by the converter anyway in conventional operation. It is therefore only necessary to detect the phase currents output by the converter in order to drive the reluctance machine in accordance with the method explained above.

The method can react to both load changes and speed changes. Load changes are expressed in a changing phase inductance as a function of the impressed current, which influences the current rate of change.

The number of current phases is variable and only has to be taken into account in the switching sequence. A special design of the stator coils (stator windings) is not required. Feedback of signals other than those conventionally used to drive the reluctance machine to the converter for the purpose of regulation can advantageously be avoided. The input variables on which the control is based can be derived from the current controller itself.

In principle, the method can be used both for the operation of reluctance machines in accordance with a motor function and in a corresponding manner for the operation of reluctance machines in accordance with a generator function. However, the method is preferably used for the operation of a reluctance machine that is used in accordance with a motor function.

Optionally, the method can also include the step of determining an intermediate circuit voltage of the converter in order to create an additional possibility of influencing the output phase current. However, this would require an additional control circuit, which would increase the complexity of the method. A general variation and regulation of the intermediate circuit voltage can therefore be of interest, especially for specific applications. In general, a constant intermediate circuit voltage can be used.

Furthermore, the method can provide for taking into account a time difference between when the upper switching threshold and the lower switching threshold are reached by the phase current that is output, in order to determine the relative rotor position with respect to the rotating electromagnetic field. In other words, the driver circuit can output a phase current in relation to a desired current value in such a way that the phase current is increased until the upper switching threshold is reached. The output phase current then falls due to the phase inductance to the lower switching threshold, after which it is increased again. A quasi-constant output phase current is thus output for at least one current phase to at least one stator coil. The times at which the upper switching threshold and the lower switching threshold are reached result in a corresponding time difference per switching cycle. Due to the dependence on the phase inductance, the time difference per switching cycle will generally change. The time difference that results from the times when the upper switching threshold and the lower switching threshold are reached can therefore be used to determine the position of the rotor with respect to its relative rotor position.

Optionally, the current rate of change can be determined by a time difference between the upper switching threshold and the lower switching threshold of the rising and/or falling phase current output by the converter. In particular, the time difference can be determined by the points in time at which the upper and lower switching shafts are reached. This means that the time difference can also be viewed as a corresponding measure of the generally varying rate of current change. This is because current rates of change that differ in terms of absolute value lead to different time differences between when the upper switching threshold and the lower switching threshold of the output phase current are reached. The current rate of change can then be determined from the time difference. At the same time, this enables the relative rotor position to be determined in relation to the electromagnetic rotating field of the reluctance machine. The difference between the two switching thresholds, i.e. the difference between the upper switching threshold and the lower switching threshold, is used to determine the current change (Delta I) that occurs in the recorded time difference (Delta t) in order to calculate the current change rate (Delta I / Delta t) to be determined accordingly.

The time difference can preferably be determined by a count value of a time counter. The time counter starts counting repeatedly when the phase current controlled by the current controller reaches the upper switching threshold. The time counter stops counting when the phase current controlled by the current controller reaches the lower switching threshold. The time counter then provides a particularly simple implementation for determining the underlying time differences, which generally differ from switching cycle to switching cycle due to the influence of the varying phase inductance. The time counter also makes it possible in a particularly simple manner to avoid being subjected to additional detection signals.

Alternatively or cumulatively, the current controller has a continuous or discontinuous control behavior. For example, the current controller can include a two-point controller and/or a multi-point controller and/or a hysteresis controller and/or a controller that specifies a current differential band. Other controller types can also be used. Such regulators are easy to implement and can regulate the phase current output efficiently between the upper switching threshold and the lower switching threshold in order to provide a quasi-constant phase current output. The controller types mentioned can also be easily adapted with regard to the control behavior.

In addition, the at least one stator coil to which the phase current is applied by the converter can be in a freewheel state as soon as the phase current regulated by the current controller reaches the upper switching threshold. The stator coil is short-circuited while it is freewheeling. This means that the contacts of the stator coil are coupled with low resistance. The impressed phase current then falls relatively slowly, starting from the upper switching threshold.

Furthermore, the freewheeling of the stator coil that has been acted upon can be ended and the phase current can be output and/or amplified again as soon as the phase current regulated by the current regulator reaches the lower switching threshold. Thus, the relatively slow drop in the phase current is used for the time of freewheeling. This improves the signal quality and reduces the switching frequency, which in turn reduces power consumption.

Optionally, the instantaneous speed can be determined based on a number of switch-on edges and/or switch-off edges of at least one current phase per unit time interval. Since the rotor geometry and the stator geometry are fundamentally known, conclusions can be drawn about the rotational speed of the rotor from the number of switch-on edges and/or switch-off edges per unit time interval. For example, the number of switch-on edges per second can be determined. Here exploits the fact that the control mechanism used for the drive has a much shorter period than the mechanical period of the rotor.

If only one current phase is used to determine instantaneous speed, there is a relatively long dead time (the time other current phases are applied) within which the instantaneous speed cannot be updated. The instantaneous speed can then be assumed to be constant, based on the value last determined. This can be sufficient for various application scenarios, since the speed of the rotor changes only slowly in relation to the period length of the control mechanism.

The instantaneous speed can preferably be determined based on the number of switch-on edges and/or switch-off edges of several or all current phases per unit time interval. As a result, the accuracy of the instantaneous speed can be improved since the instantaneous speed is determined with respect to the complete angle of rotation of the underlying electromagnetic rotating field of the reluctance machine. As a result, the accuracy of the regulation is also improved since the current setpoint can be determined more precisely.

It is optionally possible to switch from a first current phase used to drive the switched reluctance machine to a second current phase used to drive it as soon as a change threshold value for the current rate of change specified for the first current phase is reached or exceeded (alternatively undershot). For example, it can be evaluated whether the current rate of change, in particular the (average) increase in the phase current within a switching cycle, reaches, falls below or exceeds a predetermined change threshold value. This condition can be met through the dependence on the varying phase inductance for a specific relative rotor position with respect to the rotating electromagnetic field. It may then be the case that an output of the phase current to the first current phase adversely affects and counteracts the speed of the rotor. Therefore, it then becomes necessary to switch to a second current phase. The sequential triggering advantageously reduces the effort involved in switching between the current phases.

Alternatively or cumulatively, an output of the phase current can be ended by a driver circuit of the converter for the respective current phase after a switch-off signal. The switch-off signal is then determined in that the count value of the time counter for the respective current phase exceeds a predetermined switching threshold value. If, for example, the count value of the time counter varies from switching cycle to switching cycle due to the changing phase inductance, in particular increases, a corresponding switching threshold value can be defined in a particularly simple manner, and when it is reached or exceeded, the switch-off signal to end the output of the phase current for the corresponding current phase is triggered . The time counter can therefore be used in a particularly simple manner to define corresponding switchover threshold values.

In particular, it is possible to switch from a first current phase used to drive the switched reluctance machine to a second current phase used to drive it as soon as a switching threshold value specified for the first current phase is reached or exceeded. Analogous to a changing speed of current change with a corresponding change threshold value, the changeover threshold value can be used to specify whether a subsequent current phase is energized. The sequential triggering depending on the control of the previously applied current phase simplifies the overall control effort.

Furthermore, it is also possible to switch from a first current phase used for driving the switched reluctance machine to a second current phase used for driving based on a count value difference between count values of repeated count processes of the time counter. As previously explained, the counts of the repeated counts vary due to the changing phase inductance. The phase inductance fluctuates between extreme values, ie a minimum phase inductance and a maximum phase inductance. Since the phase inductance between these extreme values generally exhibits a monotonically increasing or monotonically decreasing behavior (depending on the overlap of rotor teeth and stator teeth), the count value differences between count values of successive counting processes will also generally be monotonically increasing or monotonically decreasing, at least until the following extreme value of the phase inductance is reached. The count differences between counts of consecutive counts therefore provide a measure to determine when to switch from applying one phase of current to a subsequent phase of current. For this purpose, the counter value differences of the count values of consecutive counting processes can be evaluated and a corresponding threshold value can be defined. It is also conceivable that not every counter value difference is recorded, but rather an interpolation method is used at least partially in order to determine the switchover time.

Optionally, the count value difference between count values of repeated and/or consecutive count processes of the time counter can also be used to determine the instantaneous speed of the rotor. For this purpose, for example, each determined counter value can be used in order to determine an inductance that corresponds to the respective determined counter value. As already explained, there is a direct connection between the relative rotor position and the inductance, which can be used to determine the instantaneous speed. By determining each individual relative rotor position as a function of the respective inductance value, a new instantaneous rotor speed can be determined with each new measurement.

Alternatively or cumulatively, all count value differences of a current phase can also be determined, ie from repeated and/or consecutive counting processes of the time counter. An envelope curve then results over the counter value differences, which is determined by a corresponding instantaneous rotor speed. The instantaneous rotor speed can therefore be determined from the envelope curve, which results from the previously determined counter value differences. The ongoing adjustment of the envelope due to new, determined count differences allows the instantaneous rotor speed to be updated.

Alternatively or cumulatively, the switch-on signal and/or the switch-off signal for outputting the phase current and/or ending the output of the phase current for a current phase used for driving can be determined by extreme values of a phase inductance of the respective current phase. The phase inductance fluctuates between a minimum phase inductance and a maximum phase inductance depending on the overlap of at least one rotor tooth and at least one associated stator tooth. These extreme values of the phase inductance therefore generally determine the switching points at the beginning or at the end of the output of the phase current in order to enable the most efficient machine operation possible.

Furthermore, the switch-on signal and/or the switch-off signal for outputting the phase current and/or ending the output of the phase current can depend on an instantaneous speed of the rotor and/or an operating point of the reluctance machine and/or predetermined machine parameters of the reluctance machine. Depending on the instantaneous speed of the rotor, it can be advantageous, for example, to select a switchover time for ending the output of the phase current such that it is just before reaching an extreme value (in particular maximum value) of the respective phase inductance. As a result, an extended time interval can then be provided until the subsequent extreme value (in particular minimum value) of the phase inductance is reached, so that the phase current can actually drop sufficiently before it is output again. Such a wiring, which deviates from the extreme values with regard to the phase inductance, can be advantageous, for example, for relatively high instantaneous speeds of the rotor. Similar deviations can be provided in order to adapt the output of the phase currents to the operating points and/or machine parameters of the reluctance machine.

In general, the turn-on signal for outputting the phase current can be determined by a minimum of the phase inductance (minimum phase inductance) and/or the turn-off signal for stopping the output of the phase current can be determined by a maximum of the phase inductance (maximum phase inductance). As already explained, the phase inductance depends on the overlapping of at least one rotor tooth and at least one associated stator tooth. With complete overlap, the maximum phase inductance (also longitudinal axis inductance) occurs. When the rotor tooth and stator tooth gap are symmetrically compared, the minimum phase inductance (also quadrature axis inductance) occurs. If the output of the phase current is not ended when the maximum phase inductance is reached, then the decreasing overlap of the rotor tooth and associated stator tooth leads to a decreasing phase inductance. If the phase current continues to be output at this point in time, then this produces at least a proportion of an influence that hinders the movement of the rotor, since at least a proportion of the reluctance force is caused counter to the direction of rotation of the rotor. The extreme values of the respective phase inductance are therefore suitable for determining the point in time of the signals for outputting the phase current.

In particular, the switch-on signal for outputting the phase current for a specific current phase can coincide with a switch-off signal for ending the output of the phase current of a previous current phase. With regard to the underlying phase inductance, a sequential, mutually dependent wiring of the current phases is also possible, which reduces the control effort.

The switch-on signal for outputting the phase current for a current phase and/or the switch-off signal for ending the output of the phase current can optionally have a time offset with respect to the respective extreme values of the phase inductance of the respective current phase. The time offset can be variable, especially within predetermined limits based on the respective extreme value of the phase inductance. In other words, it is possible to deviate at least slightly from a circuit corresponding to the extreme values of the phase inductance in order to achieve secondary effects, for example in order to influence the resulting torque ripple. A continuously varying slight deviation of the switching time in relation to the time at which the respective extreme value of the phase inductance is reached leads to the system being driven less symmetrically. As a result, the course of the output torque of the reluctance machine does not have a fixed course, as a result of which a symmetrical superimposition with regard to the amplitude is avoided. Overall, therefore, the torque output becomes more uniform in amplitude, resulting in less torque ripple. This can reduce the load on driven external components.

Furthermore, an absolute instantaneous rotor position can be determined after a reference position has first been determined. In this respect, the relative rotor position can be “calibrated” with respect to the reference position. By continuously determining the relative rotor position, the current, absolute instantaneous rotor position can then be determined for all relative rotor positions as a function of the reference position.

Alternatively or cumulatively, an absolute instantaneous rotor position can be determined based on the times at which the upper switching threshold and/or the lower switching threshold of the phase current output by the converter is reached. The extreme values of the phase inductances can differ from one another, for example, as a result of intentionally introduced asymmetrical magnetic circuits and/or as a result of manufacturing tolerances. If the times at which the upper switching threshold and/or the lower switching threshold of the output phase current is reached are determined, the respective absolute instantaneous rotor position can then be determined, for example because a specific switching threshold sequence corresponds to a specific asymmetric magnetic circuit profile.

Furthermore, an initial rotor position (when the rotor is stationary) can be determined based on a current pulse that is applied to all current phases simultaneously and/or sequentially (“pulse injection method”). The determination of the initial rotor position is then based on the evaluation of the magnetic flux linkage and/or the evaluation of the phase inductance. In particular, the respective phase inductance can take place, for example, by evaluating counted values from time counters assigned to the respective current phases or based on a comparison of the respective phase currents. The current pulse used is selected in such a way that it does not cause the rotor to rotate. In this respect, the current pulse can have a correspondingly small amplitude.

Alternatively, the determination of the initial rotor position can also be avoided. Because the rotor can also be brought into a defined position by simply controlling it. A single current phase can be controlled. Alternatively, several current phases can also be controlled sequentially. The resulting movement of the rotor makes it possible to determine the relative rotor position of the rotor with respect to the underlying electromagnetic rotating field.

Since the instantaneous rotational speed of the rotor changes only slowly relative to the period length of the phase current control, this can optionally also be used to eliminate "measurement errors" when determining the current rate of change, the time difference between the upper switching threshold and the lower switching threshold being reached by the phase current output To identify counts of the time counter and count differences of consecutive counts of the time counter. In this respect, the current control can include a safety mechanism that detects major deviations from an expected value that can be determined based on the instantaneous rotational speed of the rotor. In this case, the current controller can provide that the respective "measured value" is not taken into account in the current control.

According to a further aspect, a system comprising at least one switched reluctance machine and at least one converter is also provided. The reluctance machine is driven based on the method previously described. This means that the converter is arranged and set up to output corresponding phase currents to stator coils (stator windings).

The reluctance machine includes a stator with stator teeth and a rotor with rotor teeth.

Of course, with a corresponding design, the rotor and stator can also each have sets of several rotor teeth and stator teeth that show a simultaneous overlapping behavior.

Optionally, the stator and/or the rotor can be segmented. This means that, for example, several stator teeth together form a stator segment of the stator. In other words, a stator segment includes a number of stators teeth. Correspondingly, rotor segments can be provided, each correspondingly comprising a plurality of rotor teeth. This makes it possible to build a redundant reluctance machine. Maintenance work can thus be simplified. Also, transportation can be simplified. In addition, the cost of materials for the construction can be reduced.

For example, for segmented reluctance machines, but generally also in general, the converter can be designed as a single device for all segments (generally: stator windings of the same current phases) or in the form of multiple devices for each individual segment. Thanks to the sensorless drive concept explained here, each converter finds the correct switch-on and switch-off time. This advantageously reduces the complexity of the regulation and the complexity of the wiring, since each converter determines its own switch-on and switch-off times to match the respective segment position. Furthermore, assembly can also be simplified in this way, since inaccurate positioning is automatically compensated for by each converter. The assembly effort is therefore reduced.

For example, all current phases present are assigned to a stator segment. This makes it possible for the different stator segments to be constructed in the same way, as a result of which the complexity and thus the costs can be reduced. Each stator segment can be supplied independently via its own assigned converter with its own current control and rotor position detection. This provides redundancy in the event of a segment failure so that the reluctance machine can continue to operate. Furthermore, based on the self-sufficient supply, different segments can also be electrically dimensioned differently, as a result of which a reluctance machine with a performance adjustment to the respective application is provided. Alternatively, the different electrical dimensioning can be used in order to be able to adapt the reluctance machine to different performance requirements. The reluctance machine can then be operated with the best possible efficiency in each case in accordance with a current power requirement.

The converter includes at least one speed controller, one current controller and one driver circuit for outputting the phase currents.

The speed controller forwards the current setpoint to the current controller and can be designed as a simple PID controller, for example.

The current controller has at least indirectly the task of feeding the respective phase current into the corresponding stator coil (stator winding). Depending on the rotor position, it selects the current phase to be switched. The rotor position does not have to be absolutely known. It is sufficient to consider a relative rotor position with regard to the underlying electromagnetic rotating field. Different current forms (e.g. sine wave, sawtooth wave, square wave or others) can be used. A selection can be appropriately made to influence the generated torque and the torque ripple. The current controller is typically faster than the speed controller and subordinate to it.

Optionally, the current controller can include a hysteresis controller or two-point controller or be designed as such. This makes it possible to obtain a quasi-constant phase current by choosing suitable switching thresholds of the underlying controller. The control speed of the current controller can be taken into account. In this case, the respective rise and fall time of the phase current results as a variable quantity, since this is influenced by the varying phase inductance as a function of the relative rotor position. In this way, the current rate of change and the time difference between reaching the upper switching threshold and the lower switching threshold of the underlying controller can be influenced. The current controller therefore not only determines the current phase to be applied, but also provides the corresponding switch-on times and switch-off times in order to obtain a quasi-constant phase current.

The driver circuit can include, for example, corresponding semiconductor devices, in particular diodes and/or active semiconductors, which block and/or switch and/or regulate. Illustratively, these may be transistors, metal-oxide-semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), or other equivalent devices that allow easy adjustment of the output phase currents. The power electronics (driver circuit) of the converter can be set up in particular as an asymmetrical half-bridge, depending on the number of current phases.

Optionally, the converter can be set up to assume at least three operating states with regard to each current phase, namely "off", "on" and "freewheeling". In the no-current operating state, the "off" state prevents the phase current in the loaded stator coil (stator winding) increases. In the energized operating state, the current flows via the voltage source. The voltage of the source is then compared to the voltage of the station gate coil switched, causing a rapid current drop. In the "freewheeling" operating state, on the other hand, the coil is short-circuited, which results in a relatively slow current drop in the respective phase current. In the "On" operating state, the voltage from the source is applied to the stator coil and the phase current in the stator coil increases.

It is only necessary to detect the phase currents output by the converter in order to drive the reluctance machine according to the method explained above. The system, whose reluctance machine is operated according to the method explained above, is therefore simplified, at least with regard to the underlying control technology. External position encoders or speed sensors are not required. The number of underlying current phases of the stator is not subject to any special requirements. Feedback of signals other than those conventionally used for the drive to the converter for the purpose of regulation can advantageously be avoided. The system is therefore characterized by its control efficiency and reduced complexity.

The system may further include at least one data processing device coupled to the converter. The method used for the drive can then be at least partially hardware-based and/or software-based. In particular, the speed controller, the current controller, the determination of the relative rotor position and/or the determination of the instantaneous speed can essentially be software-based (computer-implemented).

All of the features explained with regard to the various aspects can be combined individually or in (sub)combination with other aspects.

character list

• - 1 eine vereinfachte schematische Darstellung eines Teils eines Systems umfassend eine Reluktanzmaschine und einen Umrichter sowie eine Vergrößerung eines Ausschnitts des Systems,
• - 2 eine vereinfachte schematische Darstellung eines beispielhaften Induktivitätsverlaufs für die Reluktanzmaschine aus 1,
• - 3 eine vereinfachte schematische Darstellung des zugrundeliegenden Regelungskonzepts bei der Reluktanzmaschine aus 1,
• - 4 eine vereinfachte schematische Darstellung des Induktivitätsverlaufs mit eingeprägtem Phasenstrom und einem korrespondierenden Zeitzähler bei der Reluktanzmaschine aus 1, und
• - 5 eine vereinfachte schematische Darstellung eines Verfahrens zum sensorlosen Betrieb einer geschalteten Reluktanzmaschine aus 1.

The invention and other advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. The features to be found in the description and the drawings can be used according to the invention individually or collectively in any combination. Show it:

• - 1 a simplified schematic representation of part of a system comprising a reluctance machine and a converter as well as an enlargement of a section of the system,
• - 2 shows a simplified schematic representation of an exemplary inductance profile for the reluctance machine 1 ,
• - 3 shows a simplified schematic representation of the underlying control concept for the reluctance machine 1 ,
• - 4 a simplified schematic representation of the inductance curve with an impressed phase current and a corresponding time counter in the reluctance machine 1 , and
• - 5 a simplified schematic representation of a method for sensorless operation of a switched reluctance machine 1 .

DETAILED DESCRIPTION

All features disclosed below in relation to the exemplary embodiments and/or the accompanying figures can be combined alone or in any sub-combination with features of the aspects of the present disclosure, including features of preferred embodiments, provided that the resulting combination of features is for a person skilled in the art field of technology makes sense.

For purposes of this disclosure, the phrase “at least one of A, B, and C” means, for example, (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C), including all other possible combinations if more than three items are listed. In other words, the term "at least one of A and B" generally means "A and/or B", namely "A" alone, "B" alone or "A and B".

1 shows a simplified schematic representation of part of a system 10 comprising an exemplary reluctance machine 12 and a converter 14 as well as a corresponding enlargement 27 of a section of the system 10.

The reluctance machine 12 comprises a stator 16 (consisting of several parts, for example) and a rotor 18. The rotor 18 is designed here as an internal rotor, and accordingly the stator 16 as an external stator. Other configurations can also be used, for example rotors 18 as external rotors or the stator 16 as a double stator, which is arranged on both sides of the rotor 18 with respect to the rotor 18 (ie inside and outside).

The present method is not limited to specific designs of stators 16 and/or rotors 18 . In this respect, the embodiment shown merely represents an exemplary configuration.

The stator 16 is segmented here, with each stator segment 17 in the embodiment shown comprising two stator teeth 20, 22 and a stator tooth gap 24 lying between them. There are also gaps between the stator segments 17 , for example gaps which are the same size as the stator tooth gaps 24 .

A stator segment 17 can be the grouping of individual stator components, in particular individual stator teeth 20, 22.

In this respect, each stator segment 17 comprises at least one stator tooth 20.

Depending on the application, the stator 16 can have different configurations. The stator teeth 20, 22 can of course also be provided as individual components (not as U-shaped components). In particular, stator teeth 20, 22 of a stator segment 17 can be subjected to a phase current jointly or sequentially, depending on the overall design of the stator 16. The rotor 18 comprises a plurality of rotor teeth 26, which in the present case are distributed uniformly around the circumference.

The passage of the rotor 18 over all the stator teeth 20, 22, which have different positions relative to the rotor teeth 26, corresponds to a full passage of the electrical angle and corresponds to the number of current phases used. By way of example, the stator segments 17A-17E with the respective stator teeth 20, 22 have different positions relative to the rotor teeth 26 of the rotor 18. The current phase number of the present reluctance machine 12 is therefore five. For simplification, however, a reluctance machine 12 with three current phases is assumed below.

A section of the system 10 is shown in more detail in an enlargement 27 for the following explanations. A first position 28A and a second position 28B (dashed lines) of the rotor 18 relative to the stator 16 are shown by way of example. Corresponding to the first position 28A, the rotor tooth 26 is oriented correspondingly to the stator tooth gap 24 . Corresponding to the second position 28B, the rotor tooth 26 is oriented correspondingly to the second stator tooth 22 .

The stator teeth 20, 22 include stator windings 30. By applying a corresponding configuration of stator teeth 20, 22, an electric field can be formed, which is closed by the rotor 18. The converter 14 , which is coupled to the stator windings 30 via signal lines 32 , can be used for charging. This generates a reluctance force which causes the rotor 18 to move, for example in the direction of rotation 34. The stator windings 30 of the different stator teeth 20, 22 are acted upon in accordance with a number of current phases, shown below as an example for a three-phase reluctance machine 12 with the current phases 36A, 36B, 36C. The current phases 36A, 36B, 36C are generally energized sequentially (one after the other). The number of current phases 36A, 36B, 36C can be chosen freely, but must match the number of rotor teeth 26 and corresponding stator teeth 20, 22.

The overlap between the rotor tooth 26, the stator tooth 22 and the gap 24 in the stator tooth determines the phase inductance 38A of the respective current phase 36A, since the stator winding 30 is arranged in a stationary manner on a respective stator tooth. If the rotor tooth 26 is correspondingly aligned with the stator tooth gap 24 (first position), then there is a minimum phase inductance. If the rotor tooth 26 is correspondingly aligned with a stator tooth 22 (second position), then there is a maximum phase inductance. The respective phase inductance 38A, 38B, 38C therefore depends on the relative rotor position in relation to the electrical angle of rotation of the underlying electromagnetic rotating field.

2 shows a simplified schematic representation of an exemplary inductance profile 40 for a reluctance machine 12 as a function of the rotor angle 42. The reluctance machine 12 is, for example, energized according to three current phases 36A, 36B, 36C. The inductance profile 40 is therefore shown for the different phase inductances 38A, 38B, 38C of the underlying current phases 36A, 36B, 36C. Since the stator teeth 20, 22 of the different current phases 36A, 36B, 36C have a geometric offset along the stator circumference in such a way that they do not overlap with rotor teeth 26 at the same time, the phase inductances 38A, 38B, 38C have a time offset with respect to their extreme values, taking into account the rotor rotation on, which is represented here by a rotor angle offset 44 . In other words, the maximum phase inductance 46A of the first current phase 36A is reached at a different rotor angle 42 (time) than the maximum phase inductance 46B of the second current phase 36B. This is also reflected accordingly in the respective minimum phase inductances 48A, 48B. Since the direction of rotation 34 of the rotor 18 is constant, each phase inductance 38A, 38B, 38C has a monotonically increasing or monotonically decreasing behavior between the extreme values of the respective phase inductance 38A, 38B, 38C, corresponding to an increasing or decreasing overlap between the stator tooth 22 and the rotor tooth 26 .

The rotor angle 42 does not have to be understood here as an absolute rotor angle. It is sufficient to interpret the rotor angle 42 as the angle of rotation of the underlying electromagnetic rotating field. Accordingly, no absolute rotor position is required, but a relative rotor position with respect to the underlying electromagnetic rotating field is sufficient, since it reflects the same dependency.

3 shows a simplified schematic representation of the underlying control concept 50 of the system 10.

The converter 14 is separated from the reluctance machine 12 except for the signal lines 32 for loading the stator windings 30 . Feedback of signals from the reluctance machine 12 to the converter 14 is not necessary for the control concept 50 . Only the phase currents 86 output via the signal lines 32 have to be evaluated and are used in the control concept 50 . This means that the input variables on which the regulation is based can be derived from the converter 14 itself.

The converter 14 includes a speed controller 52, a current controller 54, a driver circuit 56, a position determining technique 58 and a speed determining technique 60. Individual components of the converter 14 can be implemented on a hardware basis or, preferably, on a software basis.

The speed controller 52 receives a desired speed value 62 as an input variable, for example from a man-machine interface. Speed controller 52 receives an instantaneous speed 64 of rotor 18 as a further input variable. Based on the input variables, for example based on the difference, speed controller 52 determines a current setpoint 66 for applying at least one stator winding 30. Based on current setpoint 66, a phase current 86 is impressed and thus tries to adapt the instantaneous speed 64 of the rotor 18 to the desired speed value 62 .

The current controller 54 receives the current setpoint value 66 and the current actual value 72 of the phase current output by the converter 14 for the respective current phase 36A, 36B, 36C as input variables. Furthermore, the current controller 54 receives the relative rotor position 70 of the rotor 18 in relation to the underlying electromagnetic rotary field as an input variable. Based on the input variables, the current controller 54 determines switch-on times and switch-off times, which are forwarded to the downstream driver circuit 56 by a corresponding switching signal 74 (also called coil voltage). As a result, a quasi-constant phase current for the respective current phase 36A, 36B, 36C used to control the reluctance machine 12 is output by the driver circuit 56, which receives a supply voltage 76 from a voltage source.

The current controller 54 includes in particular a hysteresis controller and/or a two-point controller in order to provide a quasi-constant phase current. At least one upper switching threshold and one lower switching threshold, between which the output phase current is regulated, are defined as a function of current setpoint value 66 .

The switching times at which the output of the phase current is started and/or ended are used at least indirectly as input variables 66 of the speed determination technique 60 in order to determine the instantaneous speed 64 of the rotor 18 .

The output phase current is also used at least indirectly as an input variable 68 with regard to the respective rate of change of current in order to determine a relative rotor position 70 of the rotor 18 using the position determination technique 58 .

The converter can include a time counter 78 in particular for determining the relative rotor position 70 . The time counter 78 can start counting repeatedly when the output phase current reaches the upper switching threshold and stop counting when the lower switching threshold is reached. This results in consecutive count values and corresponding count value differences between consecutive count processes, which generally vary due to the changing phase inductance 38A, 38B, 38C due to the rotational movement of the rotor 18. The count values and count value differences can therefore determine the input variable 68 .

The method used to operate the reluctance machine 12 is described below with reference to FIG 3 and the 4 and 5 explained.

4 shows a simplified schematic representation 80 of the phase inductance 38A of an energized current phase 36A, the course of the corresponding impressed phase current 86 and a corresponding time counter 78. In this respect, the ordinate 82 is multifunctional and shows the amplitude of the phase inductance 38A, the amplitude of the phase current 86 and the height of consecutive counts 104A of the time counter 78. The abscissa 84 is also multifunctional and shows the continuous relative rotor angle 70 which is proportional to the running time.

5 shows a simplified schematic representation of a method 110 for sensorless operation of a switched reluctance machine 12. Optional method steps or partial steps are shown in dashed lines. The method 110 can therefore be expanded to include individual optional steps or sub-steps or a specific (sub)combination.

The method 110 includes at least the step 112 of determining a current setpoint 66 using the speed controller 52. The speed setpoint 62 and the instantaneous speed 64 are taken into account as input variables.

Method 110 also includes at least step 114 of determining at least one switching signal 74 using current controller 54 for at least one current phase 36A based on at least current setpoint 66 and an actual current value 72 output by converter 14 and taking into account a relative rotor position 70 with respect to an angle of rotation of an electromagnetic rotating field of the switched reluctance machine 12.

The method also includes the step 116 of outputting a phase current 86 by a driver circuit 56 of the converter 14 for at least one current phase 36A to at least one stator winding 30 as a result of the at least one switching signal 74. The output phase current 86 is divided by the current regulator 54 between an upper Switching threshold 96 and a lower switching threshold 98 regulated. 4 shows, among other things, the course of the output phase current 86 for the current phase 36A by way of example.

If the switch-on time, which is provided by the switching signal 74, has not yet been reached, the converter 14 with the current regulator 54 and the driver circuit 56 is in the operating state “Off” 88. Since the stator winding 30 is initially without current, this operating state prevents an increase of the phase current 86 in the stator winding 30.

When the switch-on time is reached, the converter 14 with the current regulator 54 and the driver circuit 56 changes to the operating state “On” 90 based on the switching signal 74. The coil voltage is then applied to the stator winding 30 and the output phase current 86 increases in accordance with the switch-on edge 87A until it reaches the upper switching threshold 96.

Now the stator winding 30 is short-circuited. The converter 14 and the stator winding 30 are therefore in the “freewheeling” operating state 92, which results in a relatively slow drop in the phase current 86 depending on the phase inductance 38A. If the phase current 86 reaches the lower switching threshold 98, the converter 14 changes back to the operating state “On” 90. The phase current 86 is amplified again until it reaches the upper switching threshold 96 again. The sequence between the operating state “freewheeling” 92 and the operating state “on” 90 is repeated until the switch-off time is reached. In this respect, the current controller 54 provides a quasi-constant phase current 86 as a function of the upper switching threshold 96 and the lower switching threshold 98 .

When the switch-off time is reached, the converter 14 changes to the operating state "Off" 94. The supply voltage 76 of the voltage source is then switched against the coil voltage of the stator winding 30, which causes a rapid current drop in the phase current 86 corresponding to the switch-off edge 87B. The turn-off time is generally reached at the time of the maximum phase inductance 46A of the phase inductance 38A. Then there is a change to the operating state "Off" 94.

Optionally, a time deviation (corresponds to an angular deviation) from reaching the maximum phase inductance 46A of the phase inductance 38A can be provided in order to influence the torque ripple, for example.

As the relative rotor position 70 changes over time, resulting in a varying phase inductance 38A, the rate of change of current 100A also varies. In other words, the gradient of the phase current 86 in the “freewheeling” operating state changes as a function of the phase inductance 38A. While the current rate of change 100A has a first gradient value corresponding to its gradient at the beginning of the “freewheeling” operating state 92, the current rate of change 100B assumes a second gradient value at a later point in time. This is also reflected in the fact that the time differences 102A, 102B between when the upper switching threshold 96 and the lower switching threshold 98 are reached by the phase current 86 vary as a function of the phase inductance 38A. Due to the dependence of the points in time when the upper switching threshold 96 and the lower switching threshold 98 are reached on the phase inductance 38A, the points in time can be used at least indirectly in a simple manner to determine the relative rotor position 70 .

An exemplary use can be made using the time counter 78 . This starts repetitively to count when the phase current 86 reaches the upper switching threshold 96 . A count ends when the phase current 86 has fallen to the lower switching threshold 98 . Count values 104A, 104B then result, which also vary, corresponding to the changing time differences 102A, 102B. As a result, there is also a generally varying count value difference 106A, 106B from successive counting processes of the time counter 78.

If the maximum phase inductance 46A is reached, the subsequent drop in the phase inductance 38A means that the phase current 86 no longer falls, but would generally increase if the converter 14 and the stator winding 30 were to remain in the “freewheeling” 92 operating state. For this reason, for example, a switchover threshold value 108 can be defined for the count value of the timer 78 , when it is reached, the timer 78 switches to the operating state “off” 94 . This switching threshold 108 can be chosen such that the switching occurs before the maximum phase inductance 46A, (exactly) at it, or after the maximum phase inductance 46A. A threshold value for counter value differences can be defined in a corresponding manner, with interpolation optionally also being able to be taken into account. These are exemplary implementation options for optional method step 126 (see explanations for 5 ).

Since the application of the phase current 86 to a first current phase 36A has now ended after the change to the “Off” operating state 94, this can optionally also be used as a trigger for the phase current 86 to be applied to a subsequent current phase 36B. This simplifies the control concept 50 (see also optional step 134).

A variety of variables are thus provided in a simple manner, which can be determined at least indirectly, namely the number of switch-on edges 78A and/or switch-off edges 78B per unit time interval, extreme values 46A, 48A of the phase inductance 38A, rates of current change 100A, time differences 102A between reaching the upper switching threshold 96 and the lower switching threshold 98 by the phase current 86, count values 104A of the time counter 78 and count value differences 106A between successive count processes of the time counter 78. The variables can be used at least indirectly as input variables 66, 68 for the position determination technique 58 and the speed determination technique 60.

For example, in the method 110, the optional step 118 can be considered. Based on the fundamentally known rotor geometry and the stator geometry, the instantaneous speed 64 can be determined using the speed determination technique 60 in that the number of switch-on edges 78A and/or switch-off edges 78B of the output phase current 86 per unit time interval is determined for at least one current phase 36A, 36B, 36C, preferably for several or all power phases 36A, 36B, 36C.

In addition, the phase inductance 38A is dependent on the relative rotor position 70 of the rotor 18. Furthermore, the phase inductance 38A can be viewed as being proportional to the measurement time. This means that the measuring time is also proportional to the relative rotor position 70. The phase inductance 38A thus increases with an increasing angle of rotation (advancing relative rotor position 70). This can also be seen from the increasing time differences 102A. The position determination technique 58 can therefore determine the relative rotor position 70 of the rotor 18 with respect to the rotating electromagnetic field based on the times when the upper switching threshold 96 and the lower switching threshold 98 were reached, the time differences 102A and/or the count values of the time counter 78 . The relative rotor position 70 can then in turn be used in the current regulator 54 for regulation.

Alternatively or cumulatively, the instantaneous speed 64 of the rotor 18 according to the optional step 120 can also be determined based on count value differences 106A from successive counting processes of the time counter 78, since the count values 104A vary due to the dependence on the phase inductance 38A, taking into account the relative rotor position 70.

In order to make this possible, each determined counter value 104A can be used, for example, to determine a phase inductance 38A corresponding to the respective determined counter value 104A. Since the relative rotor position 70 and the phase inductance 38A have a corresponding dependency, the instantaneous speed 64 of the rotor 18 can be determined by determining the individual relative rotor positions 70 as a function of the respective phase inductance 38A. With each new acquisition of a count 104A, the instantaneous speed 64 may be updated.

As a further alternative, the counter value differences 106A from repetitive and/or consecutive counting processes of the time counter 78 can also be used to determine the instantaneous speed 64 . Here, first of all, an envelope curve is determined via the counter value differences 106A, on the basis of which the corresponding instantaneous speed 64 can be determined. The continuous adaptation of the envelope due to new, determined ter counter value differences 106A enables the instantaneous speed to be updated 64.

Furthermore, step 114 can be further developed by the optional step 122 . Then the switching signal 74 can be determined by means of the current controller 54 for at least one current phase 36A based on the varying rate of current change 100A through the respective time difference 102A of the rising and/or falling phase current 86 output by the converter between the upper switching threshold 96 and the lower switching threshold 98.

Alternatively or cumulatively, method step 124 can be taken into account. Then the switching signal 74 for outputting the phase current 86 can be determined by a minimum of the phase inductance 38A (see FIG 2 ).

Furthermore, the method 110 can be further developed to include the optional step 126 in order to determine a switch-off time for changing to the “off” operating state 94 . Optionally, step 128 can be used for this purpose, according to which a switchover threshold value 108 for the timer 78 is defined, when this is reached the converter 14 and the stator winding 30 switch to the operating state “off” 94 .

Alternatively or cumulatively, the optional step 130 can also be used, which is based on the determination of a maximum of the phase inductance 38A, in order to thereby trigger the switch-off signal.

Furthermore, the method 110 can be further developed by the optional step 132. A time offset is then taken into account corresponding to an angular offset of the rotor 18 in relation to the relative rotor positions 70 at which an extreme value of the phase inductance 38A is reached in each case. In other words, the switch-on times and/or switch-off times are selected such that they deviate (slightly) from the relative rotor positions 70 corresponding to the extreme values of the phase inductance 38A. The respective deviation can be variable over time, in particular within predetermined deviation intervals based on the extreme value positions. The resulting torque ripple can thus be influenced.

The method 110 can also include the optional step 134, in which the sequential energization of the different current phases 36A, 36B, 36C is utilized. When the switch-off signal for the first current phase 36A is reached, the switch-on signal for a subsequent current phase can thereby be determined. This may be determined according to optional step 136 based on the current rate of change 100A reaching, exceeding or falling below a predetermined switching threshold, for example when the average slope of a time difference 102A exceeds the switching threshold.

Alternatively or cumulatively, according to the optional step 138, a count value difference (106A) between count values 104A of repeated counting processes of the time counter 78 can also be used to determine the point in time for switching between the current phases 36A, 36B, 36C. As such, count difference 106A may be considered to decide when to switch from a first current phase 36A used to drive switched reluctance machine 12 to a second current phase 36B used to drive.

In principle, the reluctance machine 12 can be operated by the converter 14 using the method 110 for varying speed setpoints 62 . With increasing instantaneous speeds 64, the number of intervals for determining the rate of change of current 100A naturally decreases. However, method 110 can be used at least for instantaneous speeds 64 for which at least one interval for determining current rate of change 100A still exists. In other words, a time difference 102A must still be determinable. The method must be modified for higher instantaneous speeds 64 . Here, for example, the control speed of the current controller 54 can have an influence, since the upper switching threshold 96 and the lower switching threshold 98 ultimately depend on the control speed of the current controller 54 , taking into account the instantaneous speed 64 of the rotor 18 . Adaptation of the intermediate circuit voltage also has an effect on the control speed of the current controller 54, which in turn can be used to enable even higher speeds.

Amounts and numbers may be referred to in the present application. Unless expressly stated, such amounts and numbers are not to be considered as limiting, but as examples of the possible amounts or numbers within the context of the present application. In this context, the term "plurality" can also be used in the present application to refer to a quantity or number. In this context, the term "plurality" means any number greater than one, e.g. B. two, three, four, five, etc. The terms "about", "approximately", "near" etc. mean plus or minus 5% of the stated value.

Claims (17)

Method (110) for sensorless operation of a switched reluctance machine (12) with a plurality of current phases (36A, 36B, 36C), the switched reluctance machine (12) being controlled by means of a converter (14), the method (110) having at least the following steps includes: - Determining a current setpoint (66) for applying at least one stator coil (30) by means of a speed controller (52) based on at least one speed setpoint (62) and an instantaneous speed (64), - Determining at least one switching signal (74) by means of a current controller (54) for at least one current phase (36A, 36B, 36C) based on at least the current setpoint (66) and an actual current value (72) output by the converter (14) and taking into account a Relative rotor position (70) with respect to a rotation angle of an electromagnetic rotating field of the switched reluctance machine (12), - Outputting a phase current (86) by a driver circuit (56) of the converter (14) for at least one current phase (36A, 36B, 36C) to at least one stator coil (30) as a result of the at least one switching signal (74), and wherein the output Phase current (86) is regulated by the current controller (54) between an upper switching threshold (96) and a lower switching threshold (98), the relative rotor position (70) being at least based on an initial rotor position and/or a current rate of change (100A) of the converter ( 14) output phase current (86) is determined. Method (110) according to claim 1 , the current rate of change (100A) being determined by a time difference (102A) of the rising and/or falling phase current (86) output by the converter (14) between the upper switching threshold (96) and the lower switching threshold (98), in particular the time difference (102A) is determined by points in time at which the upper switching threshold (96) and the lower switching shaft (98) are reached. Method (110) according to claim 2 , the time difference (102A) being determined by a count (104A) of a time counter (78), the time counter (78) beginning to count repeatedly when the phase current (86) regulated by the current controller (54) exceeds the upper switching threshold (96 ), in particular the time counter (78) stops counting when the phase current (86) regulated by the current controller (54) reaches the lower switching threshold (98). Method (110) according to one of the preceding claims, wherein the current controller (54) has a continuous or discontinuous control behavior, in particular wherein the current controller (54) comprises a two-point controller and/or a hysteresis controller. Method (110) according to one of the preceding claims, in which the at least one stator coil (30) to which the phase current (86) is applied by the converter (14) is in freewheeling (92) as soon as the phase current ( 86) reaches the upper switching threshold (96), in particular the freewheeling (92) of the loaded stator coil (30) is terminated and the phase current (86) is output again as soon as the phase current (86) regulated by the current regulator (54) exceeds the lower Switching threshold (98) reached. Method (110) according to one of the preceding claims, wherein the instantaneous speed (64) is determined based on a number of switch-on edges and/or switch-off edges of at least one current phase (36A, 36B, 36C) per unit time interval, preferably wherein the instantaneous speed (64) is based on the number of switch-on edges and/or switch-off edges of several or all current phases (36A, 36B, 36C) per unit time interval is determined. Method (110) according to one of the preceding claims, in which a switch is made from a first current phase (36A) used to drive the switched reluctance machine (12) to a second current phase (36B) used for driving as soon as a current phase (36A) specified for the first current phase threshold value for the rate of current change (100A) is reached or exceeded. Method (110) according to claim 3 or one of the Claims 4 until 7 so far related to claim 3 , wherein an output of the phase current (86) by a driver circuit (56) of the converter (14) for the respective current phase (36A, 36B, 36C) is terminated after a switch-off signal, and wherein the switch-off signal is determined in that the count value (104A ) of the time counter (78) for the respective current phase (36A, 36B, 36C) exceeds a predetermined switching threshold value (108). Method (110) according to claim 8 , switching from a first current phase (36A) used to drive the switched reluctance machine (12) to a second current phase (36B) used to drive as soon as a switching threshold value (108) specified for the first current phase (36A) is reached or exceeded. Method (110) according to claim 3 or one of the Claims 4 until 9 so far related to claim 3 switching from a first current phase (36A) used to drive the switched reluctance machine to a second current phase (36B) used to drive based on a count difference (106A) between counts (104A) of repeated counts of the time counter (78). Method (110) according to claim 10 wherein the instantaneous speed (64) is determined based on the count difference (106A) between counts (104A) of repeated counts of the time counter (78). Method (110) according to claim 8 or one of the claims 9 until 11 so far related to claim 8 , wherein a switch-on signal and/or the switch-off signal for outputting the phase current (86) and/or ending the output of the phase current (86) are determined by extreme values (46A, 48A) of a phase inductance (38A) of the respective current phase (36A), in particular wherein the switch-on signal and/or the switch-off signal for outputting the phase current (86) and/or ending the output of the phase current (86) from an instantaneous speed (64) of the rotor (18) and/or an operating point of the reluctance machine (12) and/or predetermined ones Machine parameters of the reluctance machine (12) depends. Method (110) according to claim 12 wherein the turn-on signal for outputting the phase current (86) is determined by a minimum of the phase inductance (48A) and the turn-off signal for stopping the output of the phase current (86) is determined by a maximum of the phase inductance (46A). Method (110) according to claim 12 or 13 wherein the turn-on signal to output phase current (86) for a particular power phase (36A, 36B, 36C) coincides with a turn-off signal to stop outputting phase current (86) of a previous power phase (36A, 36B, 36C). Method (110) according to any one of Claims 12 until 14 , wherein the switch-on signal for outputting the phase current (86) for a current phase (36A, 36B, 36C) and/or the switch-off signal for ending the output of the phase current (86) with respect to the respective extreme values (46A, 48A) of the phase inductance (38A, 38B , 38C) of the respective current phase (36A, 36B, 36C) has a time offset. Method (110) according to one of the preceding claims, wherein an absolute instantaneous rotor position is determined based on the times at which the upper switching threshold (96) and/or the lower switching threshold (98) of the phase current (86) output by the converter (14) is reached. System (10) comprising at least one switched reluctance machine (12) and at least one converter (14), wherein the reluctance machine (12) based on the method (110) according to one of Claims 1 until 16 is driven, in particular wherein the system (10) further comprises at least one with the converter (14) coupled data processing device, and wherein the method (110) according to one of Claims 1 until 16 is at least partially hardware-based and/or software-based.

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