METHOD AND DEVICE FOR SPEED CONTROLLING AN ELECTRIC MACHINE FOR DRIVING A COMPRESSOR OF A HEAT PUMP

Description

[0001] The invention relates to a method and a device for controlling the speed of an electric machine for driving a compressor, for example, a heat pump. Furthermore, the invention relates to an electric drive system with a corresponding device and a heat pump with an electric drive system, as well as a computer program and a computer-readable storage medium. State of the art

[0002] The document DE 10 2008 013 557 A1 discloses a laundry treatment appliance with a drum driven by an electric motor and an acoustic sensor, wherein the speed of the drum is regulated depending on a measured acoustic signal.

[0003] When electric motors are used to drive heat pumps, they are connected to compressors. Due to their discontinuous operation, i.e. the working cycle consisting of suction, compression and discharge under pressure, the compressors generate very strong vibrations because their piston masses are constantly accelerating and decelerating. This creates vibrations, pressure waves and structure-borne sound waves that spread throughout the entire system of pipes and components, for example in a heat pump. If these waves are radiated across a surface, for example a pipe, a housing cover or a heat exchanger, clearly audible noises result. This noise is particularly loud when a resonance frequency, for example of the pipe system or a housing, is excited.This mode of operation results in significant torque fluctuations on the compressor drive shaft, via which the rotor of the electric motor drives the compressor and is preferably connected, preferably in a rotationally fixed manner, to the compressor drive shaft. Depending on the compressor design, preferably the number of cylinders used, a fluctuating torque occurs with each revolution of the compressor drive shaft, with one or more very high peak torque loads with steep flanks, either opposite to the direction of rotation and / or in the direction of rotation of the compressor drive shaft or rotor.

[0004] The power of the compressors or the air flow through a compressor is controlled by varying the speed. Speed ​​control for inverter-driven compressors is well known. BLDC motors or synchronous machines are preferably controlled with a sensorless speed control and a subordinate field-oriented current control, also without a sensor. With constant speed control, the peak torque loads described above are applied to the compressor drive shaft or rotor, causing acceleration, vibrations, pressure fluctuations, and resulting noise. These torque fluctuations also cause compensating currents in the electrical drive circuit between the power source and the electrical machine, which are reflected in a fluctuation in the electrical power drawn from or fed back into the electrical intermediate circuit.This power must either be temporarily stored in the DC link capacitors or taken from the power source or the grid. The latter leads to undesirable grid disturbances. Therefore, the DC link capacitor must be dimensioned depending on the load driven by the electric machine and the resulting torque fluctuations in the drive system. For larger torque fluctuations, the DC link capacitor must be designed with a larger capacitance.If, to compensate for peak torque loads in the direction of rotation, power is extracted from the mechanical system via the electric machine and the inverter by the machine providing a braking torque, and then later, when the compressor is braking very strongly, this power is supplied again by applying an increased drive torque, additional losses are generated due to the repeated conversion of electrical energy from the inverter intermediate circuit into mechanical energy of the rotating system and back again. A simple speed control would do precisely this: if the compressor is braking strongly and thus the speed drops, this is compensated, preferably with a subsequent delay, by an increased electrical drive torque. If the compressor is "driving" and thus increases the speed, the speed control would compensate for this by setting a braking torque with the electric machine.

[0005] Therefore, there is a need for solutions that dampen compressor vibrations and the associated noise, while simultaneously maintaining the average compressor speed at the desired value using conventional speed control. This also reduces the power fluctuations of the intermediate circuit and thus potential grid perturbations and additional losses. Furthermore, the mechanical load on the individual components of the drive system is also reduced. The publications DE 103 41 106 A1, EP 1 519 046 A2, and US 2012 / 306411 A1 disclose methods and devices for controlling the speed of an electric machine for driving a compressor.

[0006] It is known to control electric induction machines using field-oriented control (FOR). This control is essentially designed to control the fundamental current. For this purpose, the fundamental current is transformed into DC variables id, iq in the co-rotating dq coordinate system using the d / q transformation. The DC variables are controlled in the coordinate system, and the determined manipulated variables du, uq are then transformed back into the time domain and used as the fundamental voltage to control the electric machine. Field-oriented control is preferably used to easily and, above all, very dynamically set the desired torque of an electric machine using power electronics and a controller.To achieve highly dynamic torque adjustment and technically simple adjustment of the desired torque, the three-phase currents are transformed into a vertical rotating system that usually rotates with the rotor field. In this system, the torque is adjusted by varying the torque-generating current component (q) and preferably by varying the flux-generating component (d). For simplification, a fundamental wave machine is preferably assumed. This subordinate control is preferably used alongside direct control. Disclosure of the invention

[0007] A method for controlling the speed of an electric machine for driving a compressor, for example, a heat pump, with a speed controller and a damping unit is provided. The method comprises the following steps: Determining a target torque as a function of a difference between a target speed and an actual speed of the electric machine by means of the speed controller, determining a damping torque as a function of an angle and a first torque value, superimposing a variable characterizing the target torque with a variable characterizing the damping torque to form a variable characterizing the control torque, controlling the electric machine with the variable characterizing the control torque.

[0008] In the method, a target torque for the electric machine is first determined based on a comparison of a predeterminable target speed and the actual speed. The target speed is preferably specified as a function of the power to be delivered, preferably a compressor power to be delivered by the compressor to be driven by the electric machine. The actual speed is preferably a speed detected by means of a sensor device, preferably of the rotor of the electric machine or the compressor drive shaft. Alternatively, the actual speed is a variable characterizing the actual speed that correlates with the actual speed. Or the actual speed is determined sensorlessly from physical parameters of the drive system, preferably from measured phase voltages or the phase currents of the electric machine or by means of a physical mathematical model of at least the electric machine.Depending on the difference, a target torque is determined using a predetermined characteristic map or a predetermined functional relationship. This target torque or the variables used to determine it - for example, the speed target value or actual value - are preferably heavily filtered or its average value is calculated over at least one pass through the machine or compressor rotational irregularity in order to determine a damping torque. To avoid the torque fluctuations mentioned above, a damping torque is determined. Since the torque fluctuations occur due to the mechanical design of a load coupled to the electric machine, the level of the damping torque to be specified is determined as a function of an angle. This angle is preferably a variable correlated with the rotor angle of the electric machine. The angle is preferably the rotor angle of the electric machine or the compressor drive shaft.If the rotor of the electric machine and the compressor drive shaft are rigidly connected, the angle values ​​are identical. If a gearbox is arranged between the electric machine and the compressor, or if the compressor drive shaft is connected to the compressor pistons via a gearbox within the compressor, the angle must be a value correlated with the rotor angle of the electric machine, which takes into account the entire load cycle of the compressor. This fully accounts for the periodic torque fluctuations that occur during a compressor's working cycle, consisting of intake, compression, and discharge under pressure. In addition, an initial torque value is also taken into account to determine the damping torque, since the level of the specified damping torque increases with increasing power.The damping torque to be specified is determined using a predetermined characteristic map or a mathematical function.

[0009] Preferably, a damping voltage value corresponding to the damping torque is applied for damping after a field-oriented control based on the angle and the first torque value, usually the average torque setpoint of the speed control. Preferably, a damping torque value is added to an input setpoint torque of a field-oriented control.

[0010] A variable characterizing the control torque results from the superposition of a variable characterizing the target torque with a variable characterizing the damping torque. The superposition is preferably an addition or multiplication of the two variables. The resulting variable characterizing the control torque is used to control the electric machine. Control is preferably carried out using an inverter, which converts the variable characterizing the control torque into a phase voltage, which is applied to the windings or phases of an electric machine.

[0011] Advantageously, a speed control is provided that influences or reduces design-related torque fluctuations of driven loads or a drive system. The speed controller preferably maintains the average speed constant and specifies the average torque over at least one pass of the load rotational irregularity as the setpoint of the underlying field-oriented or, if applicable, direct current or torque control. This correctly adjusts the compressor's power. Noise reduction is achieved by additionally determining a damping torque.

[0012] In another embodiment of the invention, the damping torque is determined as a function of a harmonic function with a predetermined frequency of a predeterminable order of the rotational speed of the electric machine.

[0013] The damping torque is specified as a function of a harmonic function with a predetermined frequency of a predeterminable order of the speed, the electrical frequency of the electric machine, or the speed of the compressor drive shaft of the compressor to be driven by the electric machine. The damping torque is preferably specified as a function of the load angle, preferably in the case of a fixed coupling based on the rotor angle of the electric machine. This preferably correctly takes into account the order and the speed as well as the orientation over the angle. Piston compressors, preferably reciprocating compressors, are preferably used as compressors. The significant non-uniform resistances over one revolution of the compressor drive shaft arise depending on the number of reciprocating pistons in a compressor.The predetermined frequency is therefore preferably an nth order of a fundamental frequency of the rotor angle or the mechanical frequency of the electric machine or the compressor drive shaft or the compressor's working cycle, which makes a significant contribution to the mechanical vibrations of the electric machine, the compressor to be connected and / or the drive system. These are preferably the 1st, 2nd, 3rd, 4th, and / or 6th order. Preferably, several, in particular more than one or more than two, harmonic orders of the compressor are taken into account simultaneously. The number of orders to be taken into account is preferably specified depending on the design of the compressor. The computational effort increases only at most linearly with the number of orders.

[0014] When determining the nth order as a function of the angle, it is advantageous to map any order in a table. If the effects of torsional irregularities of different orders increase uniformly with torque, a two-dimensional table for the average torque or the torque specified by the speed control and the angle is sufficient, regardless of the order. If the noise or structure-borne sound waves of different orders change to different degrees with the torque, a table must be stored for each type of torque dependence.

[0015] The position of the signals to be added in relation to the angle is determined by the design of the compressor. It should be noted that the compressor rotor is always mounted in the same position relative to the electric motor rotor during production, which can be easily achieved using Poka-Yoke. If a gearbox is installed between the electric motor and the compressor, the gear ratio or the position of the gearbox input and output shafts must be taken into account in the tables. Here, too, the position of the input to output shafts must be known. This means that the position angle of the damping table can be determined using the position detection of the electric motor or a sensor-free rotor position determination. The same applies if a function is used to determine the damping signals or a combination of table and function.

[0016] If the position of the rotor shaft to the compressor shaft is not exactly known, e.g. because Poka-Yoka is not used in production, the angle can be compensated for during initial commissioning of the finished product based on the noise generated by adding an offset until the noise or structure-borne sound waves are minimal.

[0017] Advantageously, an additive periodic damping torque is provided to superimpose on the target torque of the speed controller in order to influence the vibrations and noise development of the drive system with an electric machine and a mechanically coupled compressor.

[0018] In another embodiment of the invention, the harmonic function is specified as a sine or cosine function, a rectangular function, or as any desired function or by means of a characteristic map, wherein the desired function or the parameters of the characteristic map are specified as a function of uneven drive system resistances.

[0019] The harmonic function is preferably specified as a sine or cosine function or as a rectangular function. Alternatively, any function can be specified, for example one determined analytically or based on the compressor design. Or a harmonic function is specified using a predetermined characteristic map. The analytically determined function or the predetermined characteristic map are preferably determined or specified as a function of the non-uniform drive system resistances. The non-uniform drive system resistances include the non-uniform resistances of the compressor to be connected over one revolution of the compressor drive shaft, of the electric machine over one revolution of the rotor and / or further non-uniform resistances of the coupling of the rotor of the electric machine to the compressor drive shaft of the compressor to be connected over one revolution of the compressor drive shaft.Preferably, the rotor of the electric motor is connected to the compressor drive shaft. The connection can be non-rotatable, separable, or damped, for example, by means of a dual-mass flywheel. Preferably, a non-rotatable connection or a step-up or step-down gear is arranged between the rotor and the compressor drive shaft. The rotational speed of the rotor differs from the rotational speed of the compressor drive shaft. The uneven resistances are taken into account depending on the slower-rotating shaft.

[0020] Advantageously, a method is provided for providing an additive periodic damping torque for superimposing on the target torque of the speed controller.

[0021] According to the invention, the amplitude of the damping torque is specified as a function of a variable characterizing the target torque.

[0022] The amplitude and thus the strength of the torque to be superimposed is specified as a function of a variable characterizing the target torque. A variable characterizing the target torque correlates with the target torque, which is determined by the speed controller. As the target torque increases, a larger damping torque to be superimposed is specified to influence the vibration and noise of the drive system.

[0023] Advantageously, a method is provided for specifying an amplitude of an additive periodic damping torque for superimposing on the target torque of the speed controller.

[0024] In one embodiment of the invention, the variable characterizing the target torque is the determined target torque and the variable characterizing the damping torque is the determined damping torque, the superposition of the target torque and the damping torque to the control torque is the variable characterizing the control torque.

[0025] The determined target torque and the determined damping torque are superimposed to form the control torque for controlling the machine.

[0026] Advantageously, the determined values ​​are used directly to control the electrical machine.

[0027] In another embodiment of the invention, the variable characterizing the target torque is determined as a target voltage by means of a field-oriented control and the variable characterizing the damping torque is determined as a damping voltage by means of a field-oriented control and / or a machine model and the target voltage and the damping voltage are superimposed to form a control voltage, which is determined as the variable characterizing the control torque.

[0028] Using field-oriented control, a target voltage is determined, preferably from the target torque determined by the speed controller. This target voltage is determined as a function of the target torque and thus characterizes the target torque. Accordingly, using field-oriented control and / or a machine model, a damping voltage is determined as a function of the determined damping torque, which characterizes the damping torque. The control voltage is specified as a superposition of the target voltage and the damping voltage, which characterizes the control torque due to their interdependencies.

[0029] Field-oriented control systems are widely used to control electrical machines, preferably synchronous machines with permanent magnet excitation. The alternating variables of the phase currents to be controlled in the time domain, preferably sinusoidal, also known as the fundamental waves, are transferred by means of a mathematical transformation into a coordinate system rotating at the frequency of the alternating variables. The frequency of the alternating variables also determines the frequency of the magnetic field in the machine, so that this coordinate system rotating at the frequency of the alternating variables is also called a field-oriented system. During steady-state operation of the electrical machine, the alternating variables in the time domain result in direct variables in the field-oriented system, which can be controlled using standard control engineering methods. The field-oriented system is also called a d / q coordinate system. Its d-axis points in the direction of the rotor flux.The q-axis is perpendicular to the d-axis. A sinusoidal phase current is represented as a stator current vector, which is characterized by its length and direction.

[0030] This current phasor rotates synchronously with the rotating stator or rotor flux of the electric machine. In the d / q coordinate system, the current phasor can be represented according to its length and direction using two perpendicular components Id and Iq, which are equal in the steady-state case. Alternatively or in addition to field-oriented control, so-called direct torque control methods can also be used. In these methods, the inverter control signals are not calculated using field-oriented control and modulation, but rather directly based on a model and output to the inverter. When using this type of control, the damping torque must be added to the torque setpoint before direct machine control.

[0031] The determined variables are advantageously used to control the electrical machine by means of a field-oriented control or a direct torque control method.

[0032] According to the invention, the first torque value corresponds to the determined target torque or the torque value of a field-oriented control.

[0033] Depending on the embodiment, the determined torque value or a torque value of a field-oriented control is used as the first torque.

[0034] Preferably, the damping compensation causes the actual speed value to deviate from the setpoint speed and thus acts as a disturbance for the speed controller. If the speed control is heavily filtered, it no longer reacts to the speed fluctuation within a load cycle. In this case, the speed controller only reacts very slowly to a speed change that occurs, for example, due to an increasing average load. The dynamics of the speed control are low. The influence of the ripple compensation and the ripple load within a compressor cycle on the actual speed of the machine is therefore preferably simulated using a model to avoid filtering. For this purpose, this model value is subtracted from the determined actual speed value before it is fed to the speed control. If the model is correct, no speed filter is required because the speed ripple is masked out for damping purposes for the speed controller.

[0035] Advantageously, variants for determining the first torque value are provided to determine the amplitude of the damping torque.

[0036] In another embodiment of the invention, the influence of the damping torque on the actual speed is determined using a model of the mechanical system and subtracted from the actual speed.

[0037] By determining the influence of the damping torque on the actual speed using a model of the mechanical system and taking this into account when determining the target torque, the two stages of speed control, namely the determination of a target torque and the determination of the damping torque, are decoupled.

[0038] Advantageously, a method for decoupling the two stages of the speed control is provided.

[0039] Furthermore, the invention relates to a computer program which comprises instructions which, when executed by a computer, cause the computer to carry out the steps of the method described so far.

[0040] Furthermore, the invention relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method described so far.

[0041] The invention further relates to a device for controlling the speed of an electric machine for driving a compressor, wherein the device comprises a speed controller and a damping unit. The device is configured to carry out the steps of the described method.

[0042] Advantageously, a device for effective speed control is provided which influences or reduces design-related torque fluctuations of driven loads or a drive system.

[0043] The invention further relates to an electric drive system comprising an electric machine and a described device. Such an electric drive system serves, for example, to drive a compressor of a heat pump. The method and device enable optimized operation of the drive system with regard to mechanical stress and / or noise generation.

[0044] Furthermore, the invention relates to a heat pump with a described electric drive system, wherein the heat pump comprises a compressor and in particular a condenser, a throttle, and / or an evaporator. Thus, a heat pump is advantageously provided which comprises a device for effectively controlling an electric machine.

[0045] It is understood that the features, properties and advantages of the method according to the invention apply or are applicable accordingly to the device or the electric drive system and the heat pump and vice versa.

[0046] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawing

[0047] In the following, the invention will be explained in more detail with reference to some figures, which show: Figure 1 a schematic structure for determining a damping torque Figure 2 a schematic speed control structure of an electrical machine Figure 3 a first alternative schematic speed control structure of an electric machine Figure 4 a second alternative schematic speed control structure of an electrical machine Figure 5a third alternative schematic speed control structure of an electric machine Figure 6 a schematically illustrated flow diagram for a method for controlling the speed of an electrical machine. Figure 7 a schematically illustrated device for speed control of an electrical machine Figure 8 a schematically illustrated heat pump with an electric drive system Embodiments of the invention

[0048] The Figure 1shows a schematic structure or damping unit 220 for determining a damping torque T_D. Depending 245 on the angle Phi and an offset position ΔPhi or phase shift to be taken into account, a value 255 of a harmonic function with a predetermined frequency of a predeterminable order 250 of the rotational speed of the electric machine or the rotational speed of the compressor drive shaft of the compressor to be driven by the electric machine is provided, for example as a sine function 260. Depending on a first torque value T_1, a factor for influencing the amplitude 270 is determined, by which the sine function 260 is multiplied 265. The result of the multiplication is the control torque T_D, depending on which the electric machine 204 is controlled.Preferably, for damping various several predeterminable orders, several harmonic functions with a predetermined frequency of a predeterminable order 250 of the rotational speed of the electric machine or the rotational speed of the compressor drive shaft of the compressor to be driven by the electric machine are taken into account.

[0049] The Figure 2shows a schematic speed control structure 200 of an electric machine 204 for driving a compressor 640. As a function of the angle Phi and a first torque value T_1, a damping torque T_D is determined in a damping unit 220. A target torque T_soll is determined as a function of a difference between a target speed n_soll and an actual speed n_ist of the electric machine 204 by means of a speed controller 210. At a first superposition point 212, a variable characterizing the target torque T_soll is superimposed with a variable characterizing the damping torque T_D to form a variable characterizing the control torque T_A. By means of a field-oriented control 230, a control voltage U_A is determined from the variable characterizing the control torque T_A, with which the electric machine 204 is controlled.The electric machine 204 drives, for example, a compressor 640 via the compressor drive shaft, wherein the torque T_M is transmitted from the rotor of the electric machine 204 to the compressor drive shaft.

[0050] The Figure 3 shows starting from Figure 2 a first alternative schematic speed control structure 200 of an electric machine, wherein in addition to Figure 2the speed controller 210 is decoupled from the damping unit 220 via a decoupling structure 240. The decoupling structure 240 determines a filtered speed n_fil as a feedback variable depending on the angle Phi and the damping torque T_D. The target torque T_soll is determined by means of the speed controller 210 as a function of the difference between the target speed n_soll and the filtered speed n_fil of the electric machine 204. The actual value of the speed, which is preferably determined as a function of the angle Phi, is preferably filtered via a low-pass filter. This preferably filters over at least one mechanical load cycle. It is preferably designed for the lowest speed or is tracked with the speed.Alternatively, the filtering by means of the decoupling structure 240 is carried out by means of a model of the load 640 driven by the electric machine 204, preferably by means of a model of the mechanical system consisting of a compressor, an optional gearbox between the electric machine and the compressor and / or the machine rotor, with which the effect of the vibration damping on the actual speed is modelled and from which the speed determined from the angle Phi is subtracted.

[0051] Figure 4shows a second alternative schematic speed control structure 200 of an electric machine 204 for driving a compressor 640. Depending on the angle Phi and a first torque value T_1, preferably the field-oriented control T_FOR, preferably an estimated or modeled torque value of the field-oriented control T_FOR, a damping torque T_D, preferably a damping voltage U_D of a field-oriented control 230, is determined in a damping unit 220. A target torque T_soll is determined as a function of a difference between a target speed n_soll and an actual speed n_ist of the electric machine 204 by means of a speed controller 210. By means of the field-oriented control 230, a target voltage U_soll is determined from a target current I_soll, which correlates with the target torque T_soll, and a damping voltage U_D is preferably determined from the damping torque T_D.The superposition of a variable characterizing the target torque T_soll with a variable characterizing the damping torque T_D to form a variable characterizing the control torque T_A is achieved by superimposing the target voltage U_soll with the damping voltage U_D at the second superposition point 216 to form the control voltage U_A. The control voltage U_A is used to control the electric machine 204. The electric machine 204, for example, drives a compressor 640 via the compressor drive shaft, with the torque T_M being transmitted from the rotor of the electric machine 204 to the compressor drive shaft. As an alternative to a measured or estimated speed n_actual of the electric machine 204, the speed setpoint n_soll could also be used for noise damping if the speed control 210 regulates the speed setpoint n_soll with sufficient precision.Advantageously, the measured rotor position Phi or a rotor position Phi determined with a sensor-free angle simulation can also be used to determine the damping voltage U_D.

[0052] For optimized control, a current through the electric machine I_actual is preferably fed back and subtracted as a feedback variable from the target current I_soll, which is preferably correlated with and determined from the target torque T_soll.

[0053] Figure 5 shows starting from Figure 4 a third alternative schematic speed control structure 200 of an electric machine, wherein in addition to Figure 4The field-oriented control 230 is decoupled from the damping unit 220 via a decoupling structure 240. The current measurement signal I_ist for the field-oriented control 230 is filtered accordingly to form the filtered current measurement signal I_ist_fil. For this purpose, the effect of the damping voltage U_D on the machine currents is determined using a model, and this is subtracted from the current measurement values ​​I_ist of the field-oriented control 230.

[0054] Figure 6shows a schematically illustrated flow diagram for a method 100 for controlling the speed of an electric machine 204. In step 110, a target torque T_soll is determined as a function of a difference between a target speed n_soll and an actual speed n_ist of the electric machine 204 by means of the speed controller 210. In step 120, a damping torque T_D is determined as a function of the angle Phi and a first torque value T_1. In step 130, a variable characterizing the target torque T_soll and a variable characterizing the damping torque T_D are superimposed to form a variable characterizing the control torque T_A. In step 140, the electric machine 204 is controlled with the variable characterizing the control torque T_A.

[0055] The Figure 7shows a schematically illustrated device 300 for controlling the speed of an electrical machine 204. The electrical machine 204 is controlled by means of an inverter 203. The device 300 comprises a speed control structure 200 and a computing unit 310 for controlling and implementing the speed control structure 200. The device 300 is configured to carry out the method steps described above and thus to operate and control the electrical machine 204.

[0056] The Figure 8 shows a schematically illustrated heat pump 600 with an electric drive system 500. The drive system 500 comprises the electric machine 204, which is controlled by means of an inverter 203, and a device 300 for controlling the electric machine 204, as Figure 7described. The electric machine 204 drives a compressor 640 of the heat pump 600. The heat pump 600 preferably comprises a condenser 610, a throttle 620, and / or an evaporator 630.

Claims

1. Method (100) for controlling the speed of an electric machine (204) for driving a compressor (640) of a heat pump (600), having a speed controller (210) and a damping unit (220), said method having the steps of: ascertaining (110) a target torque (T_soll) as a function of a difference between a target speed (n_soll) and an actual speed (n_ist) of the electric machine (204) using the speed controller (210), ascertaining (120) a damping torque (T_D) as a function of an angle (Phi) and a first torque value (T_1), superposing (130) a variable characterizing the target torque (T_soll) with a variable characterizing the damping torque (T_D) to form a variable characterizing the actuation torque (T_A), actuating (140) the electric machine (204) using the variable characterizing the actuation torque (T_A), characterized in that the amplitude of the damping torque (T_D) is specified as a function of a variable characterizing the target torque (T_soll) and the first torque value (T_1) corresponds to the ascertained target torque (T_soll) or the torque value (T_FOR) of a field-oriented control system (230).

2. Method (100) according to Claim 1, wherein the damping torque (T_D) is ascertained as a function of a harmonic function with a predetermined frequency of a predeterminable order of the speed of the electric machine (204) or the speed of the compressor drive shaft of the compressor to be driven using the electric machine.

3. Method (100) according to either of the preceding claims, wherein the harmonic function is specified as a sine or cosine function, a square-wave function or is specified as an arbitrary function or by means of a characteristic map, wherein the arbitrary function or the parameters of the characteristic map are specified as a function of irregular drive system resistances.

4. Method (100) according to one of the preceding claims, wherein the variable characterizing the target torque is the ascertained target torque (T_soll) and the variable characterizing the damping torque is the ascertained damping torque (T_D), and the superposition of the target torque and the damping torque to form the actuation torque (T_A) is the variable characterizing the actuation torque.

5. Method (100) according to one of the preceding claims, wherein the variable characterizing the target torque is ascertained as a target voltage (U_soll) by means of a field-oriented control system (230) and / or a machine model and the variable characterizing the damping torque is ascertained as a damping voltage (U_D) by means of a field-oriented control system and / or a machine model and the target voltage (U_soll) and the damping voltage (U_D) are superposed to form an actuation voltage (U_A), which is ascertained as the variable characterizing the actuation torque.

6. Computer program comprising instructions that cause the device in Claim 8 to carry out the method / the steps of the method (100) according to Claims 1 to 5.

7. Computer-readable storage medium comprising instructions that cause the device according to Claim 8 to carry out the method / the steps of the method (100) according to Claims 1 to 5.

8. Device (300) for controlling the speed of an electric machine (204) for driving a compressor (640), having a speed controller (210) and a damping unit (220), wherein the device is configured to carry out the steps of the method (100) according to one of Claims 1-5.

9. Electric drive system (500) having an electric machine (204) and a device (300) according to Claim 8.

10. Heat pump (600) having an electric drive system (500) according to Claim 9, wherein the heat pump (600) comprises a compressor (640) and in particular a condenser (610), a throttle (620) and / or an evaporator (630).