Method for determining a capacitively smoothed rotor current of an inductive transformer of a separately excited electrical machine

Abstract

A method (100) for determining a capacitively smoothed rotor current of an inductive transformer (1) of a separately excited electrical machine is disclosed, preferably for controlling the capacitively smoothed rotor current for driving a rotor (40) of the separately excited electrical machine. The method comprises: determining a capacitor voltage (110) of a secondary intermediate circuit capacitor (22) of the inductive transformer (1) using a primary current of the inductive transformer (1), an equivalent circuit of a transformer (30) of the inductive transformer (1), and a diode voltage of a first diode (21).1) of a rectifier circuit (21) of the inductive transformer (1); Determining a transmission power (120) of the inductive transformer (1) using the primary current and a primary voltage of the inductive transformer (1); Determining a rotor resistance (130) using the capacitor voltage, the transmission power and detected disturbance signals of the rotor (40); and Determining the rotor current (140) using the capacitor voltage, the rotor resistance and the disturbance signals.

Description

[0001] The present invention relates to a method for determining a capacitively smoothed rotor current of an inductive transformer of a separately excited electric machine, preferably to control the capacitively smoothed rotor current for driving a rotor of the separately excited electric machine. The invention further relates to a control unit and a vehicle comprising a separately excited electric machine and the control unit.

[0002] It is known to estimate the rotor current of a separately excited electric machine using the current and voltage across an inductive transformer. It is also known to estimate the rotor current of a separately excited electric machine using the primary current and voltage of the inductive transformer. Furthermore, it is known to estimate the rotor current of a separately excited electric machine using a voltage induced in the stator of the machine. Finally, it is known to determine the rotor current of a separately excited electric machine using sensors arranged on the machine.

[0003] In separately excited electrical machines, the rotor is actively controlled or regulated based on the rotor current, with the accuracy of this control depending on the accuracy of the rotor current. Therefore, the accuracy of determining or measuring the rotor current directly affects the accuracy of the rotor current control.

[0004] From each of EP 2 186 188 B1, DE 10 2022 208 061 A1, DE 10 2022 210 963 A1 and the unpublished DE 10 2023 121 924 B3, a method for determining a rotor current of a separately excited electrical machine by detecting a primary current is known.

[0005] The object of the present invention is therefore to provide a technology that is more advanced than the prior art. In particular, the accuracy of determining the rotor current is to be improved compared to other methods using capacitive smoothing, in order to control the rotor current with greater accuracy.

[0006] This problem is solved by articles with the features according to the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0007] A method for determining a capacitively smoothed rotor current of an inductive transformer of a separately excited electrical machine is disclosed, preferably for controlling or regulating the capacitively smoothed rotor current for driving a rotor of the separately excited electrical machine. The method comprises determining a capacitor voltage of a secondary DC link capacitor of the inductive transformer using a primary current of the inductive transformer, an equivalent circuit of a transformer of the inductive transformer, and a diode voltage of a first diode of a rectifier circuit of the inductive transformer. Furthermore, the method comprises determining a power transmission capacity of the inductive transformer using the primary current and a primary voltage of the inductive transformer.Furthermore, the method includes determining a rotor resistance using the capacitor voltage, the transmission power and detected disturbance signals of the rotor, and determining the rotor current using the capacitor voltage, the rotor resistance and the disturbance signals.

[0008] The inductive transformer can, for example, have a primary side carrying the primary current and a secondary side carrying a secondary current. Furthermore, the transformer can transfer the primary current from the primary side to the secondary side as the secondary current.

[0009] The capacitively smoothed rotor current can also be referred to as the rotor current designed to supply the rotor with electrical current. This rotor current can be provided from the secondary side and may be at least partially dependent on the secondary current.

[0010] The equivalent circuit can, for example, represent the actual behavior of the transformer, where the actual behavior is represented or modeled using at least one equivalent resistance and / or at least one equivalent inductance. The equivalent circuit can include at least data for a primary equivalent inductance, a secondary equivalent inductance, a primary equivalent resistance, and a secondary equivalent resistance.

[0011] The interference signals can, for example, include the value of a voltage induced in the rotor. This induced voltage can, for instance, be induced in the rotor from the stator of a separately excited electric machine. The value of the interference signals can then be provided to the process.

[0012] The method can, for example, calculate a freewheeling capacitor voltage using the primary current and diode voltage, as well as the voltage and inductance data from the equivalent circuit. Furthermore, an active capacitor voltage can be calculated using the voltage supplied by the transformer, the primary current and diode voltage, as well as the voltage and inductance data from the equivalent circuit. In this respect, a capacitor voltage can be calculated using the freewheeling capacitor voltage and the active capacitor voltage.

[0013] Using the primary current to determine the capacitor voltage can increase the accuracy of the rotor current determination. This increase in accuracy can be achieved, in particular, by including the magnetization of the inductive transformer in the rotor current determination.

[0014] In particular, using the primary current to determine the rotor current allows influencing effects of a real transformer to be included in the determination. These influencing effects can include, for example, the magnetization of the transformer.

[0015] Therefore, the rotor current and / or the rotor resistance can be used to generate control signals, in particular for setting an exact target value of the rotor current.

[0016] Furthermore, the primary current and primary voltage can be determined by means of oversampling. Oversampling allows the behavior, and in particular changes, of the primary current to be recorded.

[0017] Furthermore, the primary current can have a current gradient d i / d t represented. The current gradient d can be used in this process. i / d t represent an instantaneous value of the primary current.

[0018] Furthermore, the transmission power can be measured over a period T. A of the capacitively smoothed rotor current.

[0019] Preferably, the instantaneous value of the primary current can be captured using oversampling, allowing the primary current flow to be represented with greater accuracy. This improved accuracy can be achieved, for example, compared to sampling at a required sampling rate. The sampling rate can, for instance, be dependent on the period T. A be.

[0020] Furthermore, the transmission power can, for example, represent an average transmission power or amount of energy that is transmitted per period, e.g., modulation period.

[0021] The average transmission power p can be determined using the primary current i. p and the primary voltage u pfor example, determined based on the following formula: p¯=1TA∫oTAup⋅ip

[0022] Furthermore, the transmission power can also be determined by measuring the power loss of the inductive transformer.

[0023] The power loss can, for example, include primary power loss of the inductive transformer and / or secondary power loss of the inductive transformer and / or diode power loss of the first diode. Preferably, the power loss can be determined using all power losses.

[0024] The power loss can vary depending on the external temperature of the inductive transformer, the component temperature of the inductive transformer's components, and the first diode voltage. Therefore, approximate formulas for the respective power losses to be determined can be provided to the method.

[0025] Furthermore, the method can include determining a rotor temperature using the rotor resistance.

[0026] For example, the rotor temperature can be determined using material constants of the rotor materials. In particular, information on a specific resistance, for example at 20 °C, and / or a temperature coefficient of a material used in the rotor can be provided to the method. Furthermore, information on the specific resistances and / or temperature coefficients of all materials used in the rotor can be provided to the method. Additionally, temperature models of the rotor can be provided to the method.

[0027] Furthermore, the method may also include providing a control signal for controlling the capacitively smoothed rotor current, which is determined by means of the rotor resistance and / or the rotor current and / or the rotor temperature.

[0028] Preferably, the control signal can be determined using the rotor current and the rotor resistance.

[0029] Also disclosed is a control unit that is trained and programmed to execute the disclosed method.

[0030] Furthermore, a control unit can control the capacitively smoothed rotor current using the control signal.

[0031] For example, the rotor current and rotor resistance can be provided to the control unit, which can then generate the control signal to control the rotor current. "Control" can also refer to regulating or adjusting, for example.

[0032] Furthermore, a vehicle with an externally excited electric machine and the disclosed control unit is disclosed.

[0033] For example, the control unit can use the control signal to control the inductive transformer in such a way that the inductive transformer provides a rotor current to drive the separately excited electric machine, depending on the control signal. The controlled rotor current can then drive the rotor of the separately excited electric machine.

[0034] The present invention is described in detail below with reference to the figures. These show: Fig. 1 an inductive transformer for providing a capacitively smoothed rotor current; and Fig. 2 a process of a method for determining a capacitively smoothed rotor current of an inductive transformer according to Fig. 1 of a separately excited electrical machine, preferably to control the capacitively smoothed rotor current for driving a rotor of the separately excited electrical machine.

[0035] The present invention is described below with reference to preferred embodiments and the figures. However, this description of embodiments should not be considered exhaustive.

[0036] The Fig. Figure 1 shows an inductive transformer 1 for providing a capacitively smoothed rotor current i R .

[0037] The inductive transformer 1 comprises a primary side 10 and a secondary side 20. The primary side 10 includes a primary capacitor 11 and a bridge circuit 12. The secondary side 20 includes a rectifier circuit 21 with a first diode 21.1 and a first secondary intermediate circuit capacitor 22.

[0038] Furthermore, the inductive transformer 1 includes a transformer 30, which is represented by an equivalent electrical circuit diagram. The transformer 30 is for transmitting a primary current i Pthe primary side 10 is formed by means of a first winding n1 to a second winding n2 into a secondary current on the secondary side 20.

[0039] The equivalent circuit of the transmitter 30 includes at least one primary equivalent resistance with a primary equivalent voltage u. RP and a secondary equivalent resistance with a secondary equivalent voltage u RS Furthermore, the equivalent circuit diagram includes a primary equivalent inductance L. P , a secondary equivalent inductance Ls and a load equivalent inductance L L .

[0040] In this respect, transformer 30 is also designed to transmit a primary voltage u P the primary side 10 to form a secondary voltage us on the secondary side 10, wherein the secondary voltage us is generated by a transmission of the primary voltage u P to a primary equivalent voltage u 'P depends on the primary side 10 and the electrical equivalent components of the equivalent circuit diagram.

[0041] The first diode 21.1 includes a diode voltage U D , the secondary intermediate circuit capacitor 22 a capacitor voltage uc and the secondary side 10 a rotor current i R .

[0042] Furthermore, the secondary side 20 represents the capacitively smoothed rotor current i R a rotor 40 of a separately excited electrical machine, wherein the rotor 40 is represented by an electrical equivalent circuit diagram.

[0043] The electrical equivalent circuit of the rotor 40 includes a voltage u induced by a stator of the separately excited electrical machine. ind , an equivalent inductance with an equivalent inductance voltage u L and an equivalent resistance with an equivalent voltage u w The induced voltage u lnd can be assumed to be known.

[0044] Fig. Figure 2 shows a sequence of steps of procedure 100 for determining a capacitively smoothed rotor current i R of the more inductive transformer 30 after Fig. 1 of a separately excited electrical machine, in order to preferably use the capacitively smoothed rotor current i R to control the drive of the rotor 40 of a separately excited electric machine.

[0045] Method 100 comprises determining a capacitor voltage uc 110 of the secondary intermediate circuit capacitor 22 of the inductive transformer 1 using the primary current is of the inductive transformer 1, the equivalent circuit of the transformer 30 of the inductive transformer 1 and the diode voltage u. D the diode 21.1 of the rectifier circuit 21 of the inductive transformer 1.

[0046] The procedure also includes a determination of the transmission power p. DC 120 of the inductive transformer 1 by means of the primary current i P and the primary voltage u Pof the inductive transformer 1.

[0047] Furthermore, the procedure includes determining the rotor resistance R. R 130 by means of the capacitor voltage uc, the transmission power p DC and detected disturbance signals of the rotor 40. The disturbance signals include at least a voltage U induced in the rotor 40 by a stator of the separately excited electrical machine. ind .

[0048] Furthermore, the method allows for the determination of the rotor current i R 140 using the capacitor voltage uc, the rotor resistance R R and the interference signals.

[0049] The capacitor voltage uc can also be determined, for example, by means of a freewheeling capacitor voltage u. c-f and an active capacitor voltage u c-a determined 110 or calculated.

[0050] The freewheeling capacitor voltage can be... c-fin particular, they are calculated based on the following formula: −dipdt⋅(Lσp+Lσs)−uRp−uRs−2uD−=uC−f

[0051] Furthermore, the active capacitor voltage can be adjusted. c-a in particular, they are calculated based on the following formula: up'−dipdt⋅(Lσp+Lσs)−uRp−uRs−2uD−=uC−a

[0052] In particular, a current gradient can be a factor. i / d t of the primary current i P be used.

[0053] The transmission power p DC can, for example, be equal to the capacitor power pc of the secondary intermediate circuit capacitor 22. Preferably, an average transmission power p can be used. DC over a period T A of the rotor current i R by means of the primary voltage u P and the primary current i P The target is 120. The transmission power p can be... DC calculated based on the following formula: p¯DC=p¯c=1TA∫oTAup⋅ip

[0054] The average transmission power p can be particularly preferred. DC over the period T A and by means of the primary voltage u P , of the primary current i P and a power loss is determined. The transmission power p DC can be calculated, for example, based on the following formula: p¯DC=p¯c=1TA∫oTAup⋅ip−1TA∫oTARp⋅ip+Rs⋅is+2⋅uD⋅is

[0055] The rotor resistance R R can preferably be achieved using a formula for capacitor power p C and taking into account the induced voltage u ind The rotor resistance R will be determined to be 130. R can be calculated, for example, based on a rearrangement of the following formula: p¯DC=uind⋅uC−uindRR+RR⋅(uC−uindRR)2

[0056] The rotor current i Rcan preferably be expressed as a quotient of the difference between the capacitor voltage uc and the induced voltage u. ind , and the rotor resistance R R The target value is determined to be 140. For example, the rotor current can be i R calculated based on the following formula: IR=uC−uindRR

[0057] Furthermore, method 100 in 130 can include determining a rotor temperature using the rotor resistance. The rotor temperature T can preferably also be determined using a formula for calculating the rotor resistance R. R The rotor temperature T can be determined. For example, it can be calculated based on a rearrangement of the following formula: RR=ρ(T20°)⋅(1+α⋅(T−T20°)

[0058] In particular, a specific resistance ρ at a temperature of 20 °C of at least one material of the rotor 40 and a temperature coefficient α of at least one material of the rotor 40 can be used.

[0059] After the process has been completed, a control signal can be output to control the capacitively smoothed rotor current. The control signal can be determined using the rotor resistance and / or the rotor current and / or the rotor temperature.

[0060] The process can be implemented in a control unit that is designed and programmed to execute the process. In particular, the control unit can control or regulate the capacitively smoothed rotor current using the provided control signal.

[0061] The control unit can be installed and used in a vehicle with a separately excited electric machine. Reference symbol list 1 Circuit arrangement 10 Primary page 11 Primary capacitor 12 Bridge circuit 20 Secondary page 21 Rectifier circuit 21.1 first diode 22 Secondary intermediate circuit capacitor 30 Transformer 40 Rotor 100 methods for determining a capacitively smoothed rotor current 110 Determining capacitor voltage data 120 Determining transmission performance data 130 Determining rotor resistance data and rotor temperature data 140 Determining rotor voltage data 150 Determining rotor current data

Claims

[1] Method (100) for determining a capacitively smoothed rotor current of an inductive transformer (1) of a separately excited electrical machine, preferably to control the capacitively smoothed rotor current for driving a rotor (40) of the separately excited electrical machine, comprising: Determining a capacitor voltage (110) of a secondary intermediate circuit capacitor (22) of the inductive transformer (1) using a primary current of the inductive transformer (1), an equivalent circuit of a transformer (30) of the inductive transformer (1) and a diode voltage of a first diode (21.1) of a rectifier circuit (21) of the inductive transformer (1); Determining a transmission power (120) of the inductive transformer (1) using the primary current and a primary voltage of the inductive transformer (1); Determining a rotor resistance (130) using the capacitor voltage, the transmission power and detected disturbance signals of the rotor (40); and Determining the rotor current (140) using the capacitor voltage, the rotor resistance and the disturbance signals. [2] Method according to claim 1, characterized by that the primary current and primary voltage are determined by means of oversampling. [3] Method according to claim 1 or 2, characterized by that the primary current has a current gradient d i / d t represents. [4] Method according to any one of claims 1 to 3, characterized by , that the transmission power is determined over one period of the capacitively smoothed rotor current. [5] Method according to any one of claims 1 to 4, characterized by , that the transmission power is further determined by means of a power loss of the inductive transformer (30). [6] Method according to any one of claims 1 to 5, characterized by, that the method includes determining a rotor temperature using the rotor resistance. [7] Method according to any one of claims 1 to 6, characterized by , that the method further comprises providing a control signal for controlling the capacitively smoothed rotor current, which is determined by means of the rotor resistance and / or the rotor current and / or the rotor temperature. [8] Control unit which is trained and programmed to execute the method according to any one of claims 1 to 7. [9] Control unit according to claim 8, characterized by , that the control unit controls the capacitively smoothed rotor current by means of the control signal. [10] Vehicle with a separately excited electric machine and the control unit according to claim 8 or 9.

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