Optimized specification of setpoint voltage values for an externally excited synchronous motor

Abstract

An externally excited synchronous motor (1) comprises a stator (2), a rotor (5), an excitation winding (6), and a motor winding (3). A setpoint value determiner (9) receives an instantaneous rotational speed (ω) of the rotor (5) relative to the stator (2), a setpoint torque (M*) to be applied by the synchronous motor (1), a change in the setpoint torque (M*) over time, and actual current values (Iemax, Immax) for an excitation current (Ie) flowing in the excitation winding (6) and a motor current (Im) flowing in the motor winding (3). The setpoint value determiner (9) determines setpoint voltage values (Ue*, Um*) for an excitation voltage (Ue) driving the excitation current (Ie) and a motor voltage (Um) driving the motor current (Im) as a function of the rotational speed (ω), the setpoint torque (M*), the change in the setpoint torque (M*) over time and the actual current values (Iemax, Immax), such that the synchronous motor (1) applies, as far as possible, an actual torque (M) corresponding to the setpoint torque (M*) and the actual torque (M) changes, as far as possible, in accordance with the change in the setpoint torque (M*) over time. The setpoint value determiner (9) controls a converter device (8), which is connected to the excitation winding (6) and the motor winding (3), in accordance with the determined setpoint voltage values (Ue*, Um*), such that the converter device (8) applies voltages (Ue, Um) corresponding to the determined setpoint voltage values (Ue*, Um*) to the excitation winding (6) and the motor winding (3). The setpoint value determiner (9) determines setpoint current values (I*) for the excitation current (Ie) and the motor current (Im) as a function of the rotational speed (ω) and the setpoint torque (M*), such that the synchronous motor (1) applies, as far as possible, the actual torque (M) corresponding to the setpoint torque (M*), changes in the setpoint current values (I*) over time, such that the actual torque (M) changes, as far as possible, in accordance with the change in the setpoint torque (M*) over time, and, based on the setpoint current values (I*), the changes in the setpoint current values (I*) over time, the rotational speed (ω) and the actual current values (Ie, Im), the setpoint voltage values (Ue*, Um*).

Description

[0001] Description

[0002] Title of the invention

[0003] Optimized specification of voltage setpoints for a separately excited synchronous motor

[0004] field of technology

[0005] The present invention relates to an operating method for a separately excited synchronous motor comprising a stator, a rotor, an excitation winding and a motor winding,

[0006] - wherein a setpoint determiner receives an instantaneous rotational speed of the rotor relative to the stator and a target torque to be applied by the synchronous motor,

[0007] - wherein the setpoint determiner determines voltage setpoints for an excitation voltage driving the excitation current and a motor voltage driving the motor current, depending on the speed and the target torque, so that the synchronous motor provides an actual torque corresponding to the target torque as far as possible,

[0008] - wherein the setpoint determiner controls a converter unit connected to the excitation winding and the motor winding according to the determined voltage setpoints, so that the converter unit applies voltages corresponding to the determined voltage setpoints to the excitation winding and the motor winding,

[0009] - wherein the setpoint determiner determines current setpoints for the excitation current and the motor current depending on the speed and the target torque, so that the synchronous motor provides the actual torque corresponding to the target torque as far as possible.

[0010] The present invention further relates to a computer program for a setpoint determiner, wherein the computer program comprises machine code that can be executed by the setpoint determiner, wherein the execution of the machine code by the setpoint determiner causes the setpoint determiner to perform such an operating procedure.

[0011] The present invention further relates to a setpoint determiner for determining voltage setpoints for an excitation voltage and a motor voltage of a separately excited synchronous motor, wherein the setpoint determiner has inputs for receiving an instantaneous speed of the synchronous motor and a set torque to be applied by the synchronous motor and is programmed with such a computer program so that it performs such an operating procedure in operation.

[0012] The present invention further assumes a drive,

[0013] - wherein the drive comprises a separately excited synchronous motor with a stator, a rotor, an excitation winding and a motor winding, - wherein the drive comprises a converter device which is connected to the excitation winding for applying an excitation voltage and supplying an excitation current and which is connected to the motor winding for applying a motor voltage and supplying a motor current,

[0014] - wherein the drive has such a setpoint determiner,

[0015] - wherein the setpoint determiner is connected to the inverter device for specifying voltage setpoints for the excitation voltage and the motor voltage.

[0016] State of the art

[0017] The aforementioned items are known, for example, from EP 4 213 368 A1. The technical paper “Optimal current setpoint computation for externally excited synchronous machines” by Johannes Reinhard et al., published in the 2022 IEEE Conference on Control Technology and Applications, August 22-25, Trieste, Italy, contains essentially the same disclosure content.

[0018] From DE 10 2014 223 014 A1, an operating method for a separately excited synchronous motor is known, which has an excitation winding and a motor winding. In this operating method, a setpoint determiner receives the instantaneous speed of the synchronous motor and the target torque to be supplied by the synchronous motor. The setpoint determiner is aware of maximum values ​​for the excitation current supplied to the excitation winding, the motor voltage driving the motor current, the power of the synchronous motor, and also the resistance values ​​of the excitation winding and the motor winding. The setpoint determiner sets up an optimization problem for a current vector and solves it in real time. The current vector has a component each for a field-generating component of the motor current, a torque-generating component of the motor current, and the excitation current.The setpoint generator determines the current vector as part of the optimization problem solution in such a way as to minimize losses occurring in the excitation winding and the motor winding. The setpoint generator determines the current vector such that the actual torque of the synchronous motor, resulting from the excitation current and the motor current, corresponds to the target torque. As a supplementary condition, the setpoint generator considers that the magnitude of the excitation current does not exceed the maximum value for the excitation current, and the magnitude of the motor voltage does not exceed the maximum value for the motor voltage. The setpoint generator specifies the components of the determined current vector as setpoints to a current control device for a converter device, so that the current control device controls the converter device in such a way that the converter device supplies the excitation current to the excitation winding and the motor current to the motor winding.

[0019] From US patent 2023 / 0 283 211 A1, an electric machine with efficient torque transfer is known. The electric machine can be a motor, including a wound rotor synchronous machine. Optimal paths for the d- and q-currents are determined to achieve any desired torque trajectory. Deviations from a desired torque and applicable boundary conditions, particularly voltage and current limits, can be taken into account. The change in torque itself is neither determined, specified, nor utilized. The determined setpoints can be voltage setpoints for controlling the electric machine.

[0020] A rotary electric machine is known from US patent 2022 / 0 089 034 A1. The electric machine can be a permanent magnet machine or a variable flux machine. A control unit receives, among other things, a "motor torque slew command." Based on the determined current setpoints, voltage setpoints are calculated, which are used to control the inverter. These are "open-loop control schemes." However, some feedback loops may be present.

[0021] Summary of the invention

[0022] In recent years, the use of externally excited synchronous motors (FESM) has increased significantly. This is due to their high efficiency across the entire operating range and their high starting torque. A further advantage, particularly compared to permanent magnet synchronous motors (PESM), is that they do not require materials with limited availability, especially rare earth elements.

[0023] Furthermore, the magnetic flux of the rotor, which can be adjusted via the excitation current, represents an additional degree of freedom, allowing the desired torque to be achieved in an energy-efficient and flexible manner.

[0024] The torque control of a FESM (Fiber-Electrically Adjustable Motor) is typically performed in field-oriented coordinates. This requires calculating target currents based on the specified torque, the motor parameters, the inverter data, and the current speed. Key requirements for these target currents are that the required torque is achieved as effectively as possible while minimizing losses. The calculation must be completed within a single control cycle and therefore be capable of real-time operation. Physical limitations, such as the maximum available voltage of the inverter and the maximum current in the motor, must be observed and considered during the calculation.

[0025] In the prior art, the current components of the motor current, i.e., the field-generating and torque-generating components, as well as the excitation current, are determined partially independently of one another. The required torque is fed to a current filter, which uses filtering to determine a setpoint for the torque-generating current component of the motor current (usually referred to as the q-current) and provides this setpoint to the current control device. Furthermore, the maximum value of the motor voltage and the current motor voltage are fed to a field weakening controller. The field weakening controller determines the setpoint for the excitation current and provides this setpoint to the current control device. Additionally, the field weakening controller determines a preliminary setpoint for the field-generating component of the motor current (usually referred to as the d-current).Based on the current speed of the synchronous motor, a correction value for the setpoint of the field-forming component of the motor current is determined using a characteristic curve. The final setpoint for the field-forming component of the motor current is determined by adding this correction value to the preliminary setpoint. The final setpoint for the field-forming component of the motor current is then fed back to the current control unit.

[0026] Other approaches to FESM address this problem, but they only ever solve partial problems. Furthermore, these solutions are not real-time capable. Other state-of-the-art methods only consider the base speed range (where operation without field weakening is possible) and use characteristic curves for the field weakening controller in the field weakening range, i.e., for high speeds. These methods therefore require characteristic curves that must be recorded beforehand. Moreover, the motor current and the excitation current are considered independently, which produces suboptimal solutions.

[0027] It is also known in the art to use offline-optimized look-up tables for the currents to find an optimal operating point depending on the current speed and the requested torque. However, this solution requires a very large amount of measurement data and considerable preparation effort. The look-up tables for the motor current and the excitation current created in this way are inflexible during runtime and must be completely adjusted if the machine parameters change. Furthermore, the look-up tables are very memory-intensive if they are to be used with high accuracy and depending on the motor parameters.

[0028] In a common approach, separate PI controllers are used for the excitation current and the motor current. The use of a state controller, such as a linear quadratic controller, is also known. When designing the controller, nonlinear couplings between the currents—especially between the field-generating current and the excitation current and the motor speed—are often neglected. Therefore, such control concepts rely on linearized dynamics coupled with voltage feedforward control based on steady-state voltages. This is disadvantageous because the optimal currents are only achieved in steady-state operation. Furthermore, parameterizing the control is difficult and often only optimal for specific operating points. State-of-the-art approaches all consider only the static case, i.e., that a specific target torque is specified, and the control of the inverter is determined accordingly.As a rule, the required current setpoints are determined without considering dynamic changes and then specified to a subordinate current controller, which in turn determines the required voltage setpoints based on actual current values. In static operating conditions, satisfactory results are generally achieved using state-of-the-art methods, and even very good results are achieved using the method according to EP 4213 368 A1. However, when torque specifications change dynamically, state-of-the-art methods reach their limits.

[0029] The object of the present invention is to create possibilities by means of which good control of the inverter device and thus of the synchronous motor can still be achieved even with dynamically changing torque specifications.

[0030] The problem is solved by an operating method with the features of claim 1. Advantageous embodiments of the operating method are the subject of dependent claims 2 to 12.

[0031] According to the invention, an operating method of the type mentioned above is designed by:

[0032] - that the setpoint determiner also accepts a time change of the setpoint torque and actual current values ​​for an excitation current flowing in the excitation winding and a motor current flowing in the motor winding,

[0033] - that the setpoint determiner, when determining the voltage setpoints, also takes into account the change in the target torque over time and the actual current values, and further determines the voltage setpoints in such a way that the actual torque changes as much as possible in accordance with the change in the target torque over time.

[0034] - that the setpoint determiner continues to determine temporal changes in the current setpoints, so that the actual torque changes as much as possible in accordance with the temporal change of the setpoint torque, and

[0035] - that the setpoint determiner then determines the voltage setpoints based on the current setpoints, the time changes of the current setpoints, the rotational speed and the current actual values.

[0036] By considering the temporal change of the target torque and directly determining the voltage setpoints, superior control conditions for the synchronous motor can be determined even with rapidly changing torque requirements. Determining the voltage setpoints based on the current setpoints enables a systematic and highly robust determination of the voltage setpoints during operation. In particular, the voltage setpoints can be determined in such a way that the excitation current and the motor current follow their current setpoints and their temporal changes, similar to an asymptotic tracking control system.

[0037] Preferably, the setpoint determiner calculates the current setpoints without considering the change in the target torque over time, and calculates the change in the current setpoints over time considering both the target torque and its change over time. This simplifies the determination of the current setpoints.

[0038] Preferably, the setpoint determiner uses a current-related optimization problem to determine the current setpoints and solves it in real time. It is particularly preferred that the setpoint determiner determines the current setpoints in such a way that copper losses in the excitation winding and the motor winding caused by the excitation current and the motor current are minimized. A particularly suitable approach for this is described in detail in EP 4 213 368 A1. Within the scope of the present invention, optimization problem 1 of EP 4 213 368 A1, which is described there in conjunction with FIG 4, is particularly relevant.

[0039] Several methods are available for determining the change in current setpoints over time. In the simplest case, the change in current setpoints over time is inversely proportional to the square root of the setpoint torque and proportional to the time derivative of the setpoint torque.

[0040] Preferably, the setpoint generator is aware of the maximum values ​​for the excitation current and the motor current. In this case, the setpoint generator is able to take these maximum values ​​into account when determining the current setpoints. This results in particularly good control of the synchronous motor. The term "takes into account" means not only that the setpoint generator considers the corresponding maximum values, but also that it determines the current setpoints in such a way that these maximum values ​​are adhered to.

[0041] Preferably, the setpoint determiner uses a voltage-related optimization problem to determine the voltage setpoints. This problem takes the current setpoints and their changes over time as inputs and provides the voltage setpoints as outputs. The voltage-related optimization problem is then solved in real time. This approach yields particularly good results.

[0042] Preferably, the setpoint determiner is aware of the maximum values ​​for the excitation voltage and the motor voltage. This enables the setpoint determiner to consider these maximum values ​​when solving the optimization problem. The term "consider" means, as before, not only that the setpoint determiner takes the corresponding maximum values ​​into account, but also that it determines the voltage setpoints in such a way that these maximum values ​​are adhered to.

[0043] To solve the voltage-related optimization problem, the setpoint optimizer preferably proceeds in several coordinated steps. Preferably, as part of solving the voltage-related optimization problem, the setpoint determiner first solves the voltage-related optimization problem itself, i.e., without considering the maximum values ​​for the magnitudes of the excitation voltage and the motor voltage. This allows the setpoint optimizer to determine preliminary voltage setpoints. The setpoint optimizer then checks whether these preliminary voltage setpoints comply with the maximum values ​​for the magnitudes of the excitation voltage and the motor voltage. If so, the setpoint optimizer can directly and without further ado adopt the preliminary voltage setpoints as the final voltage setpoints for the excitation voltage and the motor voltage. No further steps are required.

[0044] If the preliminary voltage setpoints do not comply with the maximum values ​​for the excitation voltage and / or the motor voltage, i.e., the excitation voltage is greater than its corresponding maximum value and / or the motor voltage is greater than its corresponding maximum value, further steps are required. In this case, the setpoint optimizer proceeds as follows:

[0045] First, the setpoint optimizer determines the upper and lower corners of a regular prism in a field-oriented coordinate system. The area enclosed by the prism is defined by the maximum values ​​of the excitation voltage and the motor voltage, as well as the current rotational position of the rotor relative to the stator. The term "regular prism" refers, as is generally accepted, to a right prism whose base is a regular polygon, in this case typically a regular hexagon. A right prism is also generally accepted to be a prism whose top face is 1:1 greater than its base, and whose lateral surface therefore consists of rectangles.

[0046] With respect to this prism, the setpoint determiner selects a first and a second upper corner. The first upper corner is the corner of the prism where the excitation voltage reaches its maximum value and which, according to a standard specification, has the smallest distance to the preliminary voltage setpoints in the field-oriented coordinate system. The second upper corner is a different corner than the first selected corner. It is the corner that, according to the standard specification, has the smallest distance to the preliminary voltage vector after the first selected corner. The standard specification may depend, in particular, on the inductances of the excitation winding and the motor winding.

[0047] Starting from the two selected upper corners, the target value determiner then calculates a first to fifth stress vector. These stress vectors are characterized by the fact that, in the field-oriented coordinate system according to the standard, they each exhibit the smallest distance to the preliminary stress target values. They differ by the constraints that are taken into account when determining the respective stress vector. Specifically, the procedure is as follows:

[0048] - When determining the first voltage vector, the magnitude of the excitation voltage is fixed at its maximum value. However, the limitation of the motor voltage magnitude is not taken into account.

[0049] - When determining the second voltage vector, the motor voltage lies in a plane in the field-oriented coordinate system, defined by the first and second selected upper corners of the prism and the corresponding lower corners of the prism. Neither the limit on the magnitude of the excitation voltage nor the limit on the magnitude of the motor voltage is taken into account.

[0050] - When determining the third voltage vector, it is taken into account that the motor voltage has the value of the first selected upper corner of the prism. However, the limitation of the excitation voltage magnitude is not considered.

[0051] - When determining the fourth voltage vector, it is taken into account that the motor voltage has the value of the second selected upper corner of the prism. However, the limitation of the excitation voltage magnitude is not considered.

[0052] - When determining the fifth voltage vector, it is taken into account that the magnitude of the excitation voltage is at its maximum value and that the motor voltage lies on a straight line defined by the first and second selected upper corners of the prism. However, the limitation of the magnitude of the motor voltage is not considered.

[0053] A set of stress vectors is then generated. This set contains at least seven stress vectors: the first five and the first and second selected upper corners. Optionally, the set of stress vectors can also include the two lower corners corresponding to the two selected upper corners. From this set, the setpoint determiner selects the stress vector for which the magnitudes of the excitation voltage and the motor voltage comply with the maximum values ​​for the excitation voltage and the motor voltage, and which, in the field-oriented coordinate system according to the standard, exhibits the smallest deviation from the preliminary stress setpoints.

[0054] Selecting the "correct" voltage vector can be done in two steps. In the first step, the setpoint determiner removes from the previously generated set of voltage vectors those vectors where the magnitudes of the excitation voltage and / or the motor voltage do not comply with the maximum values ​​for these values. The remaining set is never empty, as it contains at least the first and second selected upper corners and—if included—the two corresponding lower corners. In a second step, the setpoint determiner then selects from this remaining set the voltage vector that, according to the standard, exhibits the smallest deviation from the preliminary voltage setpoints in the field-oriented coordinate system.

[0055] The selected voltage vector is adopted by the setpoint determiner – regardless of whether this is done in a single step or, as explained above, in two successive steps – as the voltage setpoints for the excitation voltage and the motor voltage.

[0056] This approach makes it possible to determine the optimal voltage setpoints with manageable effort. The effort required is therefore comparatively low. Nevertheless, an optimal solution can be found.

[0057] Even apart from the specific procedures described above, in which the maximum values ​​for the currents are considered first when determining the current setpoints and then the maximum values ​​for the voltages are considered when determining the voltage setpoints, it is possible for the setpoint determiner to know maximum values ​​for the magnitudes of the excitation current, excitation voltage, motor current, and motor voltage, and to consider these maximum values ​​when determining the overall voltage setpoints. For example, the maximum values ​​for the magnitudes of the voltages can also be considered when determining the current setpoints, possibly in addition to being considered again when solving the voltage-related optimization problem, and possibly also when solving the current-related optimization problem.

[0058] Preferably, the setpoint determiner checks whether the magnitude of the applied target torque complies with a predetermined maximum value. If so, the setpoint determiner uses the applied target torque and its rate of change without modification. If not, it limits the magnitude of the applied target torque to the maximum value and sets the rate of change to zero. This ensures that the setpoint determiner always operates within its permissible range, so that the determined stress setpoints are also correct.

[0059] The problem is further solved by a computer program with the features of claim 13. According to the invention, the execution of the computer program by the setpoint determiner causes the setpoint determiner to execute an operating method according to the invention.

[0060] The problem is further solved by a setpoint determiner with the features of claim 14. According to the invention, the setpoint determiner is programmed with a computer program according to the invention, so that the setpoint determiner executes an operating method according to the invention during operation. The problem is further solved by a drive with the features of claim 15. According to the invention, in a drive of the type mentioned above, the setpoint determiner is designed as a setpoint determiner according to the invention.

[0061] Brief description of the drawings

[0062] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of an exemplary embodiment, which is explained in more detail in conjunction with the drawings. These drawings show:

[0063] FIG 1 a drive,

[0064] FIG 2 a flowchart,

[0065] FIG 3 a flowchart,

[0066] FIG 4 a flowchart,

[0067] FIG 5 shows a current-related optimization problem,

[0068] FIG 6 a flowchart,

[0069] FIG 7 a flowchart and

[0070] FIG 8 shows a coordinate system with a prism.

[0071] Description of the embodiments

[0072] According to FIG. 1, a drive comprises a separately excited synchronous motor 1. The synchronous motor 1 has a stator 2 with a motor winding 3 arranged therein. A motor current Im is supplied to the motor winding 3 via a converter 4. The motor winding 3 is generally designed as a three-phase winding. The motor current Im therefore comprises the phase currents of phases a, b, c of a three-phase system. The synchronous motor 1 also has a rotor 5 with a co-rotating excitation winding 6. An excitation current le is supplied to the excitation winding 6 via another converter 7. The converter 4 and the converter 7 together form a converter unit 8.

[0073] The converter unit 8 – more precisely, the converter 4 – is connected to the individual strands of the motor winding 3 for applying a motor voltage Um or phase voltages and for supplying the motor current Im or phase currents. The phase voltages drive the phase currents. The phase voltages have a value at any given time whose magnitude is at most a maximum value Ummax. Similarly, the magnitude of the phase currents also has a value at any given time whose magnitude is at most a maximum value Immax. Furthermore, the converter unit 8 – more precisely, the converter 7 – is connected to the excitation winding 6 for applying an excitation voltage Ue and for supplying the excitation current le. The excitation voltage Ue drives the excitation current le. The magnitude of the excitation voltage Ue has a maximum value Uemax. Likewise, the magnitude of the excitation current le has a maximum value lemax.

[0074] Unlike the motor voltage Um and the motor current Im, whose components are alternating quantities, the excitation voltage Ue and the excitation current le are usually equal in magnitude. While they can have values ​​less than 0, they are generally positive.

[0075] The control of the separately excited synchronous motor 1 is carried out in the prior art and also within the scope of the present invention in a field-oriented coordinate system, i.e., in the so-called dq coordinates. The d-component of the motor current Im is the field-generating component Id, and the q-component is the torque-generating component Iq. Similarly, the motor voltage Um also has a d- and a q-component in the field-oriented coordinate system, hereinafter referred to as the field-generating voltage component Ud and the torque-generating voltage component Uq. The conversion from the phase voltages or phase currents into the corresponding components Ud, Uq or Id, Iq in the field-oriented coordinate system and back is generally known to those skilled in the art.

[0076] The field-oriented coordinate system is initially only a two-dimensional coordinate system comprising the d- and q-components of the motor voltage Um and the motor current Im. Within the scope of the present invention, this coordinate system is extended by a third component for the excitation winding 6 and its electrical quantities (excitation current le, excitation voltage Ue, and others). This extension is also common practice and generally known to those skilled in the art.

[0077] The setpoint determiner 9 is the core subject of the present invention. The setpoint determiner 9 is programmed with a computer program 10. The computer program 10 comprises machine code 11, which can be executed by the setpoint determiner 9. By executing the machine code 11, the setpoint determiner 9 performs an operating procedure, which will be explained in more detail later. Before the actual explanation of the invention, however, the fundamental electrical engineering principles and facts of a separately excited synchronous motor 1 will be explained for a better understanding of the present invention. These principles and facts are explained below in connection with various actual variables. They also apply analogously when using the corresponding setpoint variables.

[0078] For a separately excited synchronous motor, the following relationship applies between the voltages Ud, Uq, Ue and the currents Id, Iq, le:

[0079] The various quantities used in equations 1 and 2 have the following meanings:

[0080] - Ud, Uq and Ue are the stress components of the stress vector U that have already been introduced.

[0081] RS and Re are the resistances of the motor winding 3 and the excitation winding 6; together they form the resistance matrix R. They can generally be assumed to be constant. However, it is also possible to take a temperature dependency into account.

[0082] - Id, Iq and le are the already introduced current components of the current vector I.

[0083] - id, iq and ie are the magnetic fluxes in the d-, q- and e-axes. Together they form the flux vector i .

[0084] Ld, Lq, and Le are the self-inductances along the d-, q-, and e-axes, respectively. Lm is the mutual inductance of the excitation winding 6. The inductances Ld, Lq, Le, and Lm together form the inductance matrix L. It should be noted that, strictly speaking, the mutual inductances between the d- and q-axes should be located at the positions in the inductance matrix L where "0" is currently entered. However, these mutual inductances are generally significantly smaller than the self-inductances Ld and Lq along the d- and q-axes and can therefore be neglected.

[0085] - w is the electrical speed. It is related to the mechanical speed n of rotor 5 according to the relationship w / n = Zp, where Zp is the number of pole pairs of the synchronous motor 1. The electrical speed w is always used below, except when the mechanical speed n is crucial.

[0086] Under the (generally permissible) assumption that the inductances Ld, Lq, Le and Lm are constant, the following also applies:

[0087] Thus, the dynamic model of the separately excited synchronous motor 1 can be expressed in the form be represented, whereby applies.

[0088] The copper losses VK of the separately excited synchronous motor 1 are due to or in vector notation by given.

[0089] The generated torque M is determined by the current components Id, Iq, and le and the inductances Ld, Lq, Le, and Lm. It results in where AL = Ld-Lq. The matrix used in equation 8 is referred to below as L2. Furthermore, the following relationship applies to the mechanical motion of rotor 5: where J is the moment of inertia of the synchronous motor 1 or the rotor 5, and D is the coefficient of friction. ML denotes the load torque. It includes all loads coupled to the synchronous motor 1 or the rotor 5.

[0090] Finally, the relationship w = dö / dt applies, where 0 is the electric rotor angle.

[0091] Based on these relationships, the state model of the separately excited synchronous motor 1 is given by the following relationships:

[0092] System limitations still apply to the operation of the separately excited synchronous motor 1 and the converter unit 8. For example, the following limitation applies to the voltage vector U:

[0093] -K -U max < F(&)-U < K - U max (13) with

[0094] (14) and (15)

[0095] To protect the converter unit 8 and the separately excited synchronous motor 1 from overheating, it should also be ensured that the phase currents remain within their permissible maximum value Immax and that the excitation current le also remains within its maximum value lemax. The limitation of the phase currents can be expressed in the field-oriented coordinate system by the relationship

[0096] ID + Iq' < Immax 2 (17) must be observed. The limitation of the excitation current le can be directly determined by the relationship

[0097] | / e| < le max (18) must be taken into account. The maximum values ​​Immax and lemax can be constant or temperature-dependent.

[0098] Based on the above-explained electrotechnical principles and facts, the operating method according to the invention is explained in more detail below - first in connection with FIG 2, then with additional reference to the other FIGs.

[0099] According to FIG. 2, the setpoint generator 9 receives various parameters in a step S1. As shown in FIG. 1, the setpoint generator 9 has corresponding inputs 12 for this purpose. The received parameters are the instantaneous rotational speed w of the rotor 5 relative to the stator 2, a target torque M* to be applied by the synchronous motor 1, a time-dependent change dM* / dt of the target torque M*, and actual current values ​​le and Im for the excitation current le flowing in the excitation winding 6 and the motor current Im flowing in the motor winding 3. The motor current Im is generally given by the phase currents and, in this case, is converted into the field-oriented coordinate system before being supplied to the setpoint generator 9 or by the setpoint generator 9 itself. In any case, the current vector I is thus known to the setpoint generator 9 as an actual value.

[0100] In step S2, the setpoint determiner 9 calculates a setpoint Ue* for the excitation voltage Ue and a setpoint Um* for the motor voltage Um. This calculation is performed as a function of the rotational speed w, the setpoint torque M*, the rate of change dM* / dt of the setpoint torque M*, and the current vector I. The calculation is performed such that the synchronous motor 1 applies an actual torque M corresponding to the setpoint torque M* as closely as possible, and the actual torque M changes as closely as possible according to the rate of change dM* / dt of the setpoint torque M*. The determination of the setpoint Um* for the motor voltage Um is generally performed in a field-oriented coordinate system. The setpoints Ud*, Uq*, and Ue* are subsequently referred to as the setpoint U* for the voltage vector U.As a rule, the setpoint U* is converted by the setpoint determiner 9 or in a conversion unit 13 downstream of the setpoint determiner 9 into corresponding setpoints for the phase voltages, insofar as it concerns the motor voltage Um. No conversion is required for the excitation voltage Ue. It can be adopted directly.

[0101] In step S3, the setpoint determiner 9 controls the converter unit 8 according to the determined voltage setpoints Ue*, Um*. The converter unit 8 thereby applies voltages Ue, Ua, Ub, Uc corresponding to the determined voltage setpoints Ue*, Um* to the excitation winding 6 and the motor winding 3.

[0102] Steps S1 to S3 are executed iteratively and repeatedly in real time at the control frequency of synchronous motor 1. The control frequency is usually in the range of 250 ps or below, for example 125 ps or 62.5 ps.

[0103] In many cases, as shown in FIG. 3, additional steps S11 and S12 are present, which are executed after step S1 and before step S2. If steps S11 and S12 are present, the setpoint determiner 9 checks in step S11 whether the magnitude of the applied target torque M* complies with a predetermined maximum value Mmax. If so, the setpoint determiner 9 skips step S12. Otherwise, the setpoint determiner 9 executes step S12. In step S12, the setpoint determiner 9 limits the magnitude of the applied target torque M* to the maximum value Mmax. The sign of the applied target torque M* is retained. Furthermore, in step S12, the setpoint determiner 9 sets the change dM* / dt of the target torque M* to 0.

[0104] In the present invention, step S2 is the crucial step. It is important to note that step S2 is not implemented by splitting the process into determining target current values ​​for a current controller and subsequent current control, where the current controller determines the voltage setpoints Ue*, Um*, but rather that the voltage setpoints Ue*, Um* are determined directly.

[0105] In particular, the setpoint determiner 9 can, to implement step S2 as shown in FIG. 4, first determine a setpoint I* for the current vector I in a step S21. This determination is carried out such that the synchronous motor 1 applies the actual torque M corresponding to the setpoint torque M* as closely as possible. Preferably, the current setpoint I* is determined in such a way as to minimize copper losses VK caused by the excitation current le and the motor current Im in the excitation winding 6 and the motor winding 3. The determination of step S21 depends on the rotational speed w and the setpoint torque M*. The time-dependent change dM* / dt of the setpoint torque M* is generally not taken into account. A possible embodiment of step S21 will be explained in more detail later.

[0106] In step S22, the setpoint determiner 9 further determines a time change dl* / dt of the setpoint I* for the current vector I. This determination is performed such that the actual torque M changes as much as possible in accordance with the time change dM* / dt of the setpoint M*. When determining the time change dl* / dt of the setpoint I* for the current vector I, the setpoint determiner 9 generally considers, among other things, the time change dM* / dt of the setpoint M*. A possible implementation of step S22 will be explained in more detail later.

[0107] In step S23, the setpoint determiner 9 then determines the voltage setpoints II*, i.e., the setpoint II* of the voltage vector II. This determination is based on the current setpoints I*, the time-dependent changes dl* / dt of the current setpoints I*, the rotational speed w, and the actual current values ​​I. Here, too, the determination is carried out in such a way that the actual torque M corresponds as closely as possible to the setpoint M*, and the actual torque M changes as closely as possible to the time-dependent change dM* / dt of the setpoint M*, so that, as a result, the determined setpoint I* for the current vector I and its time-dependent change dl* / dt are achieved as closely as possible.

[0108] For example, the setpoint determiner 9 can implement step S21 by applying a current-related optimization problem and solving it in real time. A suitable optimization problem based on minimizing copper losses VK is explained, for example, in the aforementioned EP 4 213 368 A1; see optimization problem 1 therein. This current-related optimization problem is illustrated in FIG. 5. The method for solving this optimization problem is explained in detail in EP 4 213 368 A1.

[0109] In the simplest case, the setpoint determiner 9 solves the current-related optimization problem without considering maximum values ​​lemax and Immax for the excitation current le and the motor current Im. In this case, the setpoint I* for the current vector I is obtained as follows:

[0110] I* = M* -C . (19)

[0111] In equation 19 it A system-dependent parameter vector. It is determined by the resistances RS and Re and the inductances Ld, Lq, Le and Lm of motor winding 3 and excitation winding 6, and the number of pole pairs Zp of motor winding 3. This fact is generally known to experts.

[0112] The time change dl* / dt of the setpoint I* for the current vector I, which the setpoint determiner 9 determines in step S22, results in this case as follows:

[0113] The above-explained facts regarding the setpoint I* for the current vector I and its time change dl* / dt also apply if the setpoint determiner 9 determines the setpoint I* for the current vector I in step S21 without regard to the maximum values ​​lemax, Immax, but the setpoint I* complies with the maximum values ​​lemax, Immax.

[0114] The setpoint determiner 9 often knows the corresponding maximum values ​​lemax and Immax. For example, they can be specified to the setpoint determiner 9 as shown in FIG. 1 during prior parameterization. If the setpoint determiner 9 knows the maximum values ​​lemax and Immax, it can take these values ​​into account when determining the setpoint I* for the current vector I. The corresponding procedure is also explained in the aforementioned EP 4 213 368 A1.

[0115] In the case that the motor current Im, when determined without considering the maximum values ​​lemax and Immax, exceeds its maximum value Immax, and therefore the current-related optimization problem is solved again, this time limiting the motor current Im to its maximum value Immax, the setpoint I* for the current vector I is obtained by the relationships

[0116] I* = f M*,x) (22) and x3 + a2 -M * 2 -x 2 -td - A- / * 2 -x + aQ -M * 2 = 0 (23) and the time change dl* / dt of the setpoint I* for the current vector I by the relationship Here, f is a vector that can be obtained, for example, using the corresponding Lagrange approach; see the relevant explanations in EP 4213 368 A1. The coefficients a2, a1, and a0 are also determined using the Lagrange approach. Equation 23 has several solutions, but only one of them is real. This solution is the physically meaningful one.

[0117] In the case that the excitation current le exceeds its maximum value lemax when determined without considering the maximum values ​​lemax and Immax, and therefore the current-related optimization problem is solved again, this time limiting the excitation current le to its maximum value lemax, the setpoint I* is obtained by the relationships and the time change dl* / dt of the setpoint I* for the current vector I by the relationship f is a vector known from the literature; compare again the corresponding explanations in EP 4213 368 A1. The coefficients b2, b1 and bO are also determined by this solution.

[0118] Finally, it may occur that the current-related optimization problem needs to be solved again, this time limiting both the motor current Im to its maximum value Immax and the excitation current le to its maximum value lemax. In this case, the maximum torque Mmax is reached.

[0119] In EP 4213 368 A1, the case where the voltage limit is limited is also considered in the context of solving the current-related optimization problem.

[0120] Ud 2 + q < Um max 2(28) is effective. This is also possible within the scope of the present invention. However, it is usually not necessary, since the voltage limitation is preferably taken into account later, namely when determining the target value II* for the voltage vector U in step S23.

[0121] In EP 4213 368 A1, the solution to the current-related optimization problem also considers the case where field weakening occurs, meaning the target torque M* cannot be achieved. In this case, the current-related optimization problem designated as optimization problem 2 in EP 4213 368 A1 is also solved within the scope of the present invention. This approach itself is not the subject of the present invention.

[0122] To determine the setpoint II* for the voltage vector U (step S23 of FIG. 4), the setpoint determiner 9 preferably sets up a voltage-related optimization problem and solves it in real time. The current setpoints I* and the time-dependent changes dl* / dt of the current setpoints I* are taken as inputs to the voltage-related optimization problem. The voltage setpoint II* is provided as output. To explain the voltage-related optimization problem, the applicant believes that some preliminary remarks will be helpful.

[0123] Based on equations 10 to 12, the following relationship holds: a diagonal matrix with, in principle, freely selectable time constants Td, Tq, Te.

[0124] Equation 29 can be transformed into the form k, provided the vector function k is appropriately defined. be brought about. This results in the relationship. =(32) dt dt v 7

[0125] With the introduction of the consequential error e:= ll*, the following relationship results:

[0126] It is therefore easy to see that the control law according to equation 29 leads to a linearization of the setpoint II*. Furthermore, it is easy to see from equation 33 that the control is asymptotically stable as long as the freely selectable time constants Td, Tq, Te have positive values.

[0127] If the motor voltage Um and the excitation voltage Ue were not limited, the setpoint U* for the voltage vector U could be determined directly by substituting them into equation 29. In practice, however, the motor voltage Um and the excitation voltage Ue are limited by the maximum values ​​Ummax and Uemax for the magnitudes of the motor voltage Um and the excitation voltage Ue, respectively. The setpoint determiner 9 must take these limitations into account when determining the setpoint U* for the voltage vector U. The maximum values ​​Ummax and Uemax themselves can be specified to the setpoint determiner 9 as shown in FIG. 1 within the framework of a prior parameterization.

[0128] Below, in conjunction with FIG 6, a currently preferred procedure is explained which, on the one hand, takes into account the maximum values ​​Ummax, Uemax and, on the other hand, ensures the determination of an optimal setpoint U* for the stress vector U.

[0129] Following the procedure shown in FIG. 6, the setpoint determiner 9 first determines a voltage vector UA in step S31 according to the relationship in Equation 29. The determination of step S31 is performed without considering the maximum values ​​Uemax and Ummax for the magnitudes of the excitation voltage Ue and the motor voltage Um. As far as step S31 is concerned, the solution of the voltage-related optimization problem is therefore trivial.

[0130] In step S32, the setpoint determiner 9 checks whether the current vector UA complies with the maximum values ​​Uemax and Ummax for the magnitudes of the excitation voltage Ue and the motor voltage Um, respectively. If this is the case, the determination of the setpoint U* for the voltage vector U is already complete. It is only necessary for the setpoint determiner 9 to set the setpoint U* for the voltage vector U to the value UA in step S33. Otherwise, the setpoint determiner 9 proceeds to step S34. In step S34, the setpoint determiner 9 determines a voltage vector UB. The voltage vector UB is composed as the sum of the voltage vector UA determined in step S31 and a difference vector AU. Then, in step S35, the setpoint determiner 9 solves the "actual" voltage-related optimization problem.The word "real" was added in this case because a trivial solution is no longer possible; instead, the stress-related optimization problem must actually be solved.

[0131] In step S35, the setpoint determiner 9 determines the optimal difference vector AU. The setpoint determiner 9 determines the optimal difference vector AU by determining the minimum of a norm dependent on the respective difference vector AU according to a standard rule for all difference vectors AU and using the value of the difference vector AU at which the norm reaches its minimum as the current vector UB: min||Aw|| . (34)

[0132] The standard incorporates a weighted sum of the squares of the components of the respective difference vector AU. The weighting is preferably determined by a matrix Q, which in turn is determined by the inductance matrix L, resulting in the inductances Ld, Lq, Le, and Lm of the excitation winding 6 and the motor winding 3. Consequently, the respective standard is calculated according to the relationship

[0133] || Aw|| e = Au T - Q-Aw (35) determined, where the matrix Q is

[0134] 2 = (z 1 ) r -Z 1 (36) is determined.

[0135] In the context of varying the difference vector AU, the setpoint determiner 9 observes the constraint that the stress vector UB, i.e. the sum of the stress vector UA and the difference vector AU, complies with the restrictions according to the maximum values ​​Ummax, Uemax, resulting in equation 13.

[0136] In step S36, the setpoint determiner 9 finally sets the setpoint U* for the stress vector U to the value UA + AU. In step S36, the optimal value for the difference vector AU determined in step S35 is, of course, used. In step S35, i.e., when solving the stress-related optimization problem, the setpoint determiner 9 considers, firstly, the fundamental requirement for determining the difference vector AU, namely the relationship U = UA + AU. Furthermore, the setpoint determiner 9 considers the stress constraint according to equation 13. The standard whose value is determined is preferably again defined by the matrix Q explained above. Step S35 is explained in more detail below in conjunction with FIGS. 7 and 8.

[0137] According to FIG. 7, the setpoint determiner 9, to solve the stress-related optimization problem, first determines the upper and lower vertices EO and EU of a regular prism in a step S41 in the field-oriented coordinate system (dqe system, see FIG. 8). Only some of the upper and lower vertices EO and EU are labeled with their reference symbols in FIG. 8.

[0138] The upper corners EO are those corners of the prism where the excitation voltage Ue reaches its maximum value Uemax. Similarly, the lower corners EU are those corners of the prism where the excitation voltage Ue reaches its minimum value -Uemax. The precise position of the upper and lower corners EO and EU is determined by the maximum value Ummax for the magnitude of the motor voltage Um and the current electrical rotor angle 0. The upper and lower corners EO and EU, and thus the area enclosed by the prism, are therefore determined by the maximum values ​​Uemax and Ummax for the magnitudes of the excitation voltage Ue and the motor voltage Um, respectively, and the current (electrical) rotational position of the rotor 5 relative to the stator 2.

[0139] Along the connecting line from each upper corner EO to the corresponding lower corner EU, the excitation voltage UE varies between its minimum value -Uemax and its maximum value Uemax. The field-oriented components Ud, Uq of the motor voltage Um do not vary along this line. Conversely, along a connecting line between adjacent upper corners EO, the excitation voltage Ue constantly exhibits its maximum value Uemax, while the field-oriented components Ud, Uq of the motor voltage Um vary along the voltage limit defined by the maximum value Ummax of the motor voltage Um. Furthermore, along a connecting line between adjacent lower corners EU, the excitation voltage Ue constantly exhibits its minimum value -Uemax, while the field-oriented components Ud, Uq of the motor voltage Um vary along the voltage limit defined by the maximum value Ummax of the motor voltage Um.

[0140] In step S42, the setpoint determiner 9 selects from the upper corners EO the one that, according to the applicable standard, has the smallest distance to the stress vector UA. Similarly, in step S43, the setpoint determiner 9 selects from the upper corners EO the one that, according to the applicable standard, has the second smallest distance to the stress vector UA. These two upper corners EO are referred to below as EO1 and EO2, and the two corresponding lower corners EU as EU1 and EU2.

[0141] In step S44, the setpoint determiner 9 calculates a first stress vector U1. This calculation is performed by solving the stress-related optimization problem according to equations 34 to 36. However, when solving this problem, the setpoint determiner 9 fixes the excitation voltage Ue at its maximum value Uemax. It does not, however, consider the limitation on the magnitude of the motor voltage Um. The calculated first stress vector U1 therefore lies within the plane defined by the top surface of the regular prism in the field-oriented coordinate system. The calculated first stress vector U1 may lie within the top surface of the regular prism itself, but this is not always the case. If necessary, the setpoint determiner 9 can calculate a further first stress vector UT.The further first voltage vector UT agrees with the first voltage vector U1 with respect to the determined motor voltage Um, but the excitation voltage Ue has the opposite sign.

[0142] In step S45, the setpoint determiner 9 calculates a second voltage vector U2. This calculation is again performed by solving the voltage-related optimization problem of equations 34 to 36. However, when solving this optimization problem, the setpoint determiner 9 considers the boundary condition that the motor voltage Um lies in a plane defined in the field-oriented coordinate system by the first and second selected upper vertices EO1, EO2 of the prism and the corresponding lower vertices EU1, EU2 of the prism. In contrast, the setpoint determiner 9 does not consider the limitation on the magnitude of the excitation voltage Ue. Nor does the setpoint determiner 9 consider the limitation on the motor voltage Um.The determined second stress vector U2 can lie within the lateral surface of the regular prism itself, bounded by the first and second selected upper vertices EO1, EO2 of the prism and the corresponding lower vertices EU1, EU2 of the prism. However, this is not always and necessarily the case.

[0143] In step S46, the setpoint determiner 9 calculates a third stress vector U3. This calculation is again performed by solving the stress-related optimization problem of equations 34 to 36. However, when solving this problem, the setpoint determiner 9 considers the boundary condition that the motor voltage Um has the value of the first selected upper corner EO1 of the prism. In contrast, the setpoint determiner 9 does not consider the limitation on the magnitude of the excitation voltage Ue. The calculated third stress vector U3 therefore lies in the field-oriented coordinate system on a straight line defined by the first selected upper corner EO1 of the prism and the corresponding lower corner EU1 of the prism. The calculated third stress vector U3 can lie on the line segment between the first selected upper corner EO1 and the corresponding lower corner EU1 of the prism itself. However, this is not always the case.

[0144] In step S47, the setpoint determiner 9 calculates a fourth stress vector U4. This calculation is again performed by solving the stress-related optimization problem of equations 34 to 36. However, when solving this problem, the setpoint determiner 9 considers the boundary condition that the motor voltage Um has the value of the second selected upper corner EO2 of the prism. In contrast, the setpoint determiner 9 does not consider the limitation on the magnitude of the excitation voltage Ue. The calculated fourth stress vector U4 therefore lies in the field-oriented coordinate system on a straight line defined by the second selected upper corner EO2 of the prism and the corresponding lower corner EU2 of the prism. The calculated fourth stress vector U4 can lie on the line segment between the second selected upper corner EO2 and the corresponding lower corner EU2 of the prism itself. However, this is not always the case.

[0145] In step S48, the setpoint determiner 9 calculates a fifth stress vector U5. This calculation is again performed by solving the stress-related optimization problem of equations 34 to 36. However, when solving this problem, the setpoint determiner 9 considers the boundary condition that the excitation voltage Ue has its maximum value Uemax and the motor voltage Um lies on a straight line defined by the first and second selected upper vertices EO1 and EO2 of the prism. The setpoint determiner 9 does not, however, consider the limitation on the magnitude of the motor voltage Um. Therefore, in the field-oriented coordinate system, the calculated fifth stress vector U5 lies on a straight line defined by the first and second selected upper vertices EO1 and EO2 of the prism.The determined fifth stress vector U4 can lie on the line between the first and second selected upper corners EO1 and EO2 of the prism itself. However, this is not always the case. If necessary, the setpoint determiner 9 can determine a further fifth stress vector U5'. This further fifth stress vector U5' corresponds to the determined motor voltage Um with respect to the fifth stress vector U5, but the excitation voltage Ue has the opposite sign.

[0146] In all five (or seven) cases, the setpoint determiner 9 thus determines a respective stress vector U1 to U5, U1', U5' that has the smallest distance to the stress vector UA in the field-oriented coordinate system. However, when determining the respective stress vectors U1 to U5 and, if applicable, also UT, U5', the setpoint determiner 9 considers various constraints. In step S49, the setpoint determiner 9 forms a set of permissible stress vectors. This set of permissible stress vectors initially contains the first and second selected upper corners EO1, EO2 of the prism. Optionally, it can also include the two corresponding lower corners EU1, EU2 of the prism. These two or four stress vectors, due to their defined magnitudes of excitation voltage Ile and motor voltage Um, adhere to the maximum values ​​Uemax, Ummax.Furthermore, this set includes those voltage vectors U1 to U5 determined in steps S44 to S48 where the magnitudes of the excitation voltage Ue and the motor voltage Um comply with the permissible maximum values ​​Uemax and Ummax. If necessary, the set of permissible voltage vectors may also include the voltage vectors UT and U5', provided that the magnitudes of the excitation voltage Ue and the motor voltage Um comply with the permissible maximum values ​​Uemax and Ummax.

[0147] In step S50, the setpoint determiner 9 selects from the set of permissible stress vectors generated in step S49 the one that, according to the standard, has the smallest distance to stress vector UA. This stress vector is the stress vector UB that was visited. Step S50 completes the procedure shown in FIG. 7.

[0148] The present invention offers many advantages. For example, no complex or pre-calculated lookup tables are required. Furthermore, no critical simplifications are necessary. This allows the operating method according to the invention to be adapted very quickly for new synchronous machines. Typically, only parameterization is required. Moreover, nonlinearities and couplings are fully considered and taken into account. This allows a trajectory for the target torque to be defined, which is maintained precisely and energy-efficiently. As a result, the control behavior of the synchronous motor, its energy efficiency, and compliance with excitation current and motor current limits are improved.

[0149] Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived by a person skilled in the art without departing from the scope of protection of the invention as defined by the claims. List of reference numerals

[0150] 1 synchronous motor

[0151] 2 Stator

[0152] 3 Motor winding

[0153] 4, 7 inverters

[0154] 5 Rotor

[0155] 6 Excitation development

[0156] 8 Inverter unit

[0157] 9 Target value determiners

[0158] 10 Computer programs

[0159] 11 Machine code

[0160] 12 entrances

[0161] 13 Conversion device

[0162] EO, EO1, EO2 upper corners

[0163] EU, EU1, EU2 bottom corners

[0164] Imax, Immax, lemax: Maximum values ​​for currents

[0165] I, le, In the streams

[0166] I* Current so set values

[0167] M* Target torque

[0168] Mmax maximum value for moment

[0169] S1 to S50 steps

[0170] Umax, Ummax, Uemax Maximum values ​​for voltages

[0171] Ue*, Um* Target values ​​for voltages

[0172] UA, UB, U1 to U5, UT, U5' stress vectors

[0173] VK copper losses

[0174] AU Differential vector w Rotational speed

Claims

Claims 1. Operating procedure for a separately excited synchronous motor (1) comprising a stator (2), a rotor (5), an excitation winding (6) and a motor winding (3), - wherein a setpoint determiner (9) receives an instantaneous rotational speed (w) of the rotor (5) relative to the stator (2), a setpoint torque (M*) to be applied by the synchronous motor (1), a time-dependent change of the setpoint torque (M*) and actual current values ​​(lemax, Immax) for an excitation current (le) flowing in the excitation winding (6) and a motor current (Im) flowing in the motor winding (3), - wherein the setpoint determiner (9) determines voltage setpoints (Ile*, Um*) for an excitation voltage (Ue) driving the excitation current (le) and a motor voltage (Um) driving the motor current (Im) as a function of the rotational speed (w), the setpoint torque (M*), the rate of change of the setpoint torque (M*) and the actual current values ​​(lemax, Immax), so that the synchronous motor (1) applies an actual torque (M) corresponding to the setpoint torque (M*) as far as possible and the actual torque (M) changes as far as possible in accordance with the rate of change of the setpoint torque (M*), - wherein the setpoint determiner (9) controls a converter unit (8) connected to the excitation winding (6) and the motor winding (3) according to the determined voltage setpoints (Ue*, Um*), so that the converter unit (8) applies voltages (Ue, Um) corresponding to the determined voltage setpoints (Ue*, Um*) to the excitation winding (6) and the motor winding (3), - wherein the setpoint determiner (9) determines current setpoints (I*) for the excitation current (le) and the motor current (Im) as a function of the speed (w) and the setpoint torque (M*), so that the synchronous motor (1) applies the actual torque (M) corresponding to the setpoint torque (M*) as far as possible, - wherein the setpoint determiner (9) continues to determine temporal changes in the current setpoints (I*), so that the actual torque (M) changes as far as possible in accordance with the temporal change in the setpoint torque (M*), and - wherein the setpoint determiner (9) then determines the voltage setpoints (Ue*, Um*) based on the current setpoints (I*), the time changes of the current so II values ​​(I*), the rotational speed (w) and the current actual values ​​(le, Im).

2. Operating method according to claim 1, characterized in that the voltage setpoints (Ue*, Um*) are determined in such a way that the excitation current (le) and the motor current (Im) follow their current setpoints (I*) and their temporal changes in the manner of an asymptotic tracking control.

3. Operating method according to claim 2, characterized by that the setpoint determiner (9) determines the current setpoints (I*) without taking into account the time change of the setpoint torque (M*) and determines the time change of the current setpoints (I*) taking into account the setpoint torque (M*) and the time change of the setpoint torque (M*).

4. Operating method according to claim 2 or 3, characterized in that the setpoint determiner (9) sets up a current-related optimization problem and solves it in real time to determine the current setpoints (I*).

5. Operating method according to claim 2, 3 or 4, characterized in that the setpoint determiner (9) determines the current setpoints (I*) in such a way that copper losses (VK) in the excitation winding (6) and the motor winding (3) caused by the excitation current (le) and the motor current (Im) are minimized.

6. Operating method according to one of claims 2 to 5, characterized in that the setpoint determiner (9) is aware of maximum values ​​(lemax, Immax) for the magnitudes of the excitation current (le) and the motor current (Im) and that the setpoint determiner (9) takes into account the maximum values ​​(lemax, Immax) for the magnitudes of the excitation current (le) and the motor current (Im) when determining the current setpoints (I*).

7. Operating method according to one of claims 2 to 6, characterized in that the setpoint determiner (9) uses a voltage-related optimization problem to determine the voltage setpoints (Ile*, Um*), in which the current setpoints (I*) and the time changes of the current setpoints (I*) are taken as input variables and which provides the voltage setpoints (Ue*, Um*) as output variables, and solves the voltage-related optimization problem in real time.

8. Operating method according to claim 7, characterized in that the setpoint determiner (9) is aware of maximum values ​​(Uemax, Ummax) for the magnitudes of the excitation voltage (Ue) and the motor voltage (Um) and that the setpoint determiner (9) takes into account the maximum values ​​(Uemax, Ummax) for the excitation voltage (Ue) and the motor voltage (Um) when solving the optimization problem.

9. Operating method according to claim 8, characterized by that the setpoint determiner (9) framework of solving the stress-related optimization problem - solves the voltage-related optimization problem initially without considering the maximum values ​​(Uernax, Urnmax) for the magnitudes of the excitation voltage and the motor voltage, thus determining preliminary voltage setpoints (UA), - then checks whether the preliminary voltage setpoints (UA) comply with the maximum values ​​(Uernax, Um-max) for the magnitudes of the excitation voltage (Ue) and the motor voltage (Um), - if affirmative, adopts the preliminary voltage setpoints (UA) as voltage setpoints (Ue*, Um*) for the excitation voltage (Ue) and the motor voltage (Um) and - if negative, performs the following steps: Determination of the upper and lower corners (EO, EU) of a regular prism in a field-oriented coordinate system, wherein the area enclosed by the prism is determined by the maximum values ​​(Uernax, Urnmax) for the magnitudes of the excitation voltage (Ue) and the motor voltage (Um) and a current rotational position of the rotor (5) relative to the stator (2), -- Selection of a first upper corner (EO1) of the prism at which the excitation voltage (Ue) has its maximum value (Uernax) and which, in the field-oriented coordinate system according to a standard specification, has the smallest distance to the preliminary voltage setpoints (UA), -- Selection of a second upper corner (EO2) of the prism, wherein the second selected corner (EO2) is a corner different from the first selected corner (EO1), at which the excitation voltage (Ue) has its maximum value (Uernax) and which, in the field-oriented coordinate system, has the smallest distance to the preliminary voltage setpoints (UA) after the first selected corner (EO1) according to the standard specification; determination of a first to fifth voltage vector (U1 to U5), each of which has the smallest distance to the preliminary voltage setpoints (UA) in the field-oriented coordinate system, wherein, in determining the first voltage vector (U1), the magnitude of the excitation voltage (Ue) is fixed at its maximum value (Uernax), but the limitation of the magnitude of the motor voltage (Um) is not taken into account.where, in determining the second voltage vector (U2), the motor voltage (Um) lies in the field-oriented coordinate system in a plane defined by the first and second selected upper corners (EO1, EO2) of the prism and the associated lower corners (EU1, EU2) of the prism, but the limitation of the magnitude of the excitation voltage (Ue) and the limitation of the magnitude of the motor voltage (Um) are not taken into account, where, in determining the third voltage vector (U3), it is taken into account that the motor voltage (Um) has the value of the first selected upper corner, (E01) of the prism, but the limitation of the magnitude of the excitation voltage (Ile) is not taken into account, wherein when determining the fourth voltage vector (U4) it is taken into account that the motor voltage (Um) has the value of the second selected upper corner (EO1) of the prism, but the limitation of the magnitude of the excitation voltage (Ue) is not taken into account, and wherein when determining the fifth voltage vector (U5) it is taken into account that the magnitude of the excitation voltage (Ue) has its maximum value (Uemax) and the motor voltage (Um) lies on a straight line defined by the first and second selected upper corners (EO1, EO2) of the prism, but the limitation of the magnitude of the motor voltage (Um) is not taken into account, selecting the voltage vector from a set of voltage vectors which has the first to fifth voltage vectors (1 to U5), the first and second selected upper corners (EO1,EO2) and optionally the two associated lower corners (EU1, EU2) of the prism, in which the magnitudes of the excitation voltage (Ue) and the motor voltage (Um) comply with the maximum values ​​(Uemax, Ummax) for the magnitudes of the excitation voltage (Ue) and the motor voltage (Um) and which, in the field-oriented coordinate system according to the standard specification, has the smallest distance to the preliminary voltage setpoints (UA), and adopting the selected voltage vector as voltage setpoints (Ue*, Um*) for the excitation voltage (Ue) and the motor voltage (Um).

10. Operating method according to claim 9, characterized in that the standard specification depends on the inductances of the excitation winding (6) and the motor winding (3).

11. Operating method according to claims 1 to 5, characterized in that the setpoint determiner (9) is aware of maximum values ​​(lemax, Uemax, Immax, Ummax) for the magnitudes of the excitation current (le), the excitation voltage (Ue), the motor current (Im) and the motor voltage (Um) and that the setpoint determiner (9) takes the maximum values ​​(lemax, Uemax, Immax, Ummax) into account when determining the voltage setpoints (Ue*, Um*).

12. Operating method according to one of the above claims, characterized in that the setpoint determiner (9) checks whether the amount of the target torque (M*) to be applied complies with a predetermined maximum value (Mmax), if so, utilizes the target torque (M*) to be applied and the change in the target torque (M*) over time without modification and denies If necessary, the amount of the target torque (M*) to be applied is limited to the maximum value (Mmax) and the time change of the target torque (M*) is set to 0.

13. Computer program for a setpoint determiner (9), wherein the computer program comprises machine code (11) that can be executed by the setpoint determiner (9), wherein the execution of the machine code (11) by the setpoint determiner (9) causes the setpoint determiner (9) to perform an operating procedure according to one of the above claims.

14. Setpoint determiner for determining voltage setpoints (Ile*, Um*) for an excitation voltage (Ue) and a motor voltage (Um) of a separately excited synchronous motor (1), wherein the setpoint determiner (9) has inputs (12) for receiving an instantaneous rotational speed (w) of the rotor (5) relative to the stator (2), a target torque (M*) to be applied by the synchronous motor (1), a time-dependent change of the target torque (M*) and actual current values ​​(le, Im) for an excitation current (le) flowing in the excitation winding (6) and a motor current (Im) flowing in the motor winding (3) and is programmed with a computer program (10) according to claim 13, so that it performs an operating procedure according to one of claims 1 to 12 during operation.

15. Drive, - wherein the drive comprises a separately excited synchronous motor (1) with a stator (2), a rotor (5), an excitation winding (6) and a motor winding (3), - wherein the drive has a converter device (8) which is connected to the excitation winding (6) for applying an excitation voltage (Ue) and supplying an excitation current (le) and is connected to the motor winding (3) for applying a motor voltage (Um) and supplying a motor current (Im), - wherein the drive comprises a setpoint determiner (9) according to claim 14, - wherein the setpoint determiner (9) is connected to the converter device (8) for specifying voltage setpoints (Ue*, Um*) for the excitation voltage (e) and the motor voltage (Um).

Images