Method for operating a synchronous motor excited by permanent magnets, electronic control device, motor arrangement, and storage medium

Abstract

A method for operating a permanent magnet synchronous motor comprises setting a maximum power, determining a current vector and an output voltage vector in the dq coordinate system. A setpoint amount for a setpoint voltage vector is calculated on the basis of the maximum power, the current vector and the output voltage vector. The setpoint voltage vector is generated with the setpoint amount, and then operating the permanent magnet synchronous motor at least with the setpoint voltage vector.

Claims

1. A method for operating a permanent magnet synchronous motor, the method comprising the following steps: setting a maximum power; determining a current vector in the dq coordinate system on the basis of one of a torque requirement and a power limitation and a torque requirement; determining an output voltage vector in the dq coordinate system; calculating a setpoint amount for a setpoint voltage vector on the basis of the maximum power, the current vector and the output voltage vector; generating the setpoint voltage vector with the setpoint amount; operating the permanent magnet synchronous motor at least with the setpoint voltage vector; calculating the setpoint amount as the product of the factor ⅔ with a quotient comprising a dividend and a divisor; calculating the dividend as the product of the maximum power and the amount of the output voltage vector; and calculating the divisor as the sum of the product of the d components of the output voltage vector and the current vector on the one hand and the product of the q components of the output voltage vector and the current vector on the other hand.

2. The method as claimed in claim 1, further comprising determining the current vector on the basis of measured currents flowing through the permanent magnet synchronous motor.

3. The method as claimed in claim 1, wherein determining the output voltage vector comprises determining the output voltage vector in the dq coordinate system on the basis of one of: a torque requirement, a power limitation and a torque requirement, and the current vector.

4. The method as claimed in claim 1, wherein determining the current vector comprises setting an angle of the setpoint voltage vector equal to the angle of the output voltage vector.

5. An electronic control device with instructions comprising: setting a maximum power; determining a current vector in the dq coordinate system on the basis of one of a torque requirement and a power limitation and a torque requirement; determining an output voltage vector in the dq coordinate system; calculating a setpoint amount for a setpoint voltage vector on the basis of the maximum power, the current vector and the output voltage vector; generating the setpoint voltage vector with the setpoint amount; operating the permanent magnet synchronous motor at least with the setpoint voltage vector; calculating the setpoint amount as the product of the factor ⅔ with a quotient comprising a dividend and a divisor; calculating the dividend as the product of the maximum power and the amount of the output voltage vector; and calculating the divisor as the sum of the product of the d components of the output voltage vector and the current vector and the product of the q components of the output voltage vector and the current vector.

6. The device as claimed in claim 5, wherein determining the current vector comprises determining the current vector on the basis of measured currents flowing through the permanent magnet synchronous motor.

7. The device as claimed in claim 5, wherein determining the output voltage vector further comprises determining the output voltage vector in the dq coordinate system on the basis of one of: a torque requirement, a power limitation and a torque requirement, and the current vector.

8. A motor arrangement comprising: a permanent magnet synchronous motor, an inverter for controlling the permanent magnet synchronous motor; and an electronic control device for controlling the inverter by setting a maximum power; determining a current vector in the dq coordinate system on the basis of one of a torque requirement and a power limitation and a torque requirement; determining an output voltage vector in the dq coordinate system; calculating a setpoint amount for a setpoint voltage vector on the basis of the maximum power, the current vector and the output voltage vector; generating the setpoint voltage vector with the setpoint amount; operating the permanent magnet synchronous motor at least with the setpoint voltage vector; calculating the setpoint amount as the product of the factor ⅔ with a quotient comprising a dividend and a divisor; calculating the dividend as the product of the maximum power and the amount of the output voltage vector; and calculating the divisor as the sum of the product of the d components of the output voltage vector and the current vector and the product of the q components of the output voltage vector and the current vector.

9. The motor arrangement as claimed in claim 8, wherein determining the current vector comprises determining the current vector on the basis of measured currents flowing through the permanent magnet synchronous motor.

10. The motor arrangement as claimed in claim 8, wherein determining the output voltage vector comprises determining the output voltage vector in the dq coordinate system on the basis of one of: a torque requirement, a power limitation and a torque requirement, and the current vector.

11. The motor arrangement as claimed in claim 8, further comprising setting an angle of the setpoint voltage vector equal to the angle of the output voltage vector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages will be taken by a person skilled in the art from the exemplary embodiment described below with reference to the appended drawing, in which:

(2) FIG. 1: shows a motor arrangement, and

(3) FIG. 2: shows a flow diagram.

DETAILED DESCRIPTION

(4) FIG. 1 shows a motor arrangement 10 according to an exemplary embodiment. The motor arrangement 10 has a control device 20, an inverter 30 and a permanent magnet synchronous motor 40. The control device 20 is designed to control the inverter 30, which in turn controls the motor 40, and thus both supplies it with power and specifies its operation, including a torque.

(5) The control device 20 is configured to carry out a method based on the following considerations.

(6) The power consumption of a permanent magnet synchronous motor may be calculated as follows:
U.sub.DCI.sub.DC=3/2(U.sub.dI.sub.d+U.sub.qI.sub.q)

(7) where

(8) U.sub.DC: is an applied voltage, which may be a specified vehicle electrical system voltage,

(9) I.sub.DC: is a specified maximum current,

(10) U.sub.d: is a d component of a voltage vector actually used in the dq coordinate system,

(11) I.sub.d: is a d component of a current vector actually used in the dq coordinate system,

(12) U.sub.q: is a q component of the voltage vector actually used in the dq coordinate system, and

(13) I.sub.q: is a q component of the current vector actually used in the dq coordinate system.

(14) This formula can be transformed if the amounts of the vectors and the intermediate angle are considered instead of the d and q components:
U.sub.DCI.sub.DC=3/2|U.sub.dq∥I.sub.dq| cos(phi)

(15) where

(16) U.sub.dq: is the voltage vector actually used,

(17) I.sub.dq: is the current vector actually used, and

(18) phi: is the intermediate angle between U.sub.dq and I.sub.dq.

(19) This equation can be solved for the voltage:

(20) $.Math.U_{dq}.Math.=\frac{2}{3}\frac{U_{\mathrm{DC}}{I}_{\mathrm{DC}}}{.Math.I_{dq}.Math.\cos \left(\mathrm{phi}\right)}$

(21) This gives a relationship between a specified maximum power, which is indicated by the product of U.sub.DC and I.sub.DC, the amount of the current vector, the angle phi and the amount of a voltage vector. How this relationship can be used in a motor control is discussed below.

(22) In a control of a permanent magnet synchronous motor, it is possible for example to use a current control or to use a model-based calculation in advance in order to set motor currents by setting dq voltages. Consequently, a current vector may for example be based on measurements or else on a default value. An output voltage vector U*.sub.dq, which represents the voltage vector that would be desirable without taking a power limitation into account, may first be calculated. For example, such an output voltage vector U*.sub.dq is based on a torque requirement.

(23) The intermediate angle phi may in this case be calculated as follows:

(24) $\cos \left(phi\right)=\frac{U_d^{*}{I}_d+U_q^{*}{I}_q}{.Math.I_{dq}.Math..Math.U_{dq}^{*}.Math.}$

(25) where

(26) U*.sub.d: is a d component of the output voltage vector and

(27) U*.sub.q: is a q component of the output voltage vector.

(28) If this formula for the cosine of the intermediate angle phi is used in the aforementioned equation for calculating the setpoint amount of the voltage vector, the following formula is obtained:

(29) $.Math.U_{dq}.Math.=\frac{2}{3}\frac{U_{DC}{I}_{DC}.Math.U_{\mathrm{dq}}^{*}.Math.}{U_d^{*}{I}_d+U_q^{*}{I}_q}$

(30) This allows the calculation of an amount of a voltage vector that is based on a calculated or measured current vector I.sub.dq and a calculated output voltage vector U*.sub.dq and at the same time takes into account the power limitation already specified above. This setpoint amount |U.sub.dq| can be used if the angle phi calculated according to the above formula is left the same. This results in minimal intervention in the motor parameters, which are only changed to the extent that this is necessary in order to meet the specified maximum power.

(31) Returning to the exemplary embodiment shown in FIG. 1, the control device 20 thus calculates not only the intermediate angle phi but also the output voltage vector U*.sub.dq and the setpoint amount of a voltage vector as just indicated, while it is possible here to revert to either a calculated or a measured current vector I.sub.dq. The output voltage vector U*.sub.dq is then left constant in terms of its angle, but the amount may be changed to such an extent that its amount corresponds to the setpoint amount |U.sub.dq|. In this way, the inverter 30, and ultimately also the motor 40, are then controlled. Compliance with a line limitation is thus ensured, although a externally specified torque requirement is met as far as possible with regard to the power limitation.

(32) FIG. 2 shows the procedure for calculating the setpoint voltage vector or its amount in a schematic overview. In particular, an output voltage vector U.sub.dq_rec is included at the top left. In addition, the current vector I.sub.dq with its d and q coordinates is included at the bottom left. In between it can be seen that the maximum power is included in the form of a voltage U.sub.DC and a maximum current I.sub.bmax. It can be seen on the right in the illustration of FIG. 2 that the limited values of the voltage vector are output.

(33) The mentioned steps of the method may be carried out in the order indicated. However, they may also be carried out in a different order, if this is technically appropriate. In one of its embodiments, for example with a specific combination of steps, the method may be carried out in such a way that no further steps are carried out. However, in principle, further steps can also be carried out, even steps that have not been mentioned.

(34) It should also be pointed out that refinements, features and variants of the invention which are described in the various embodiments or exemplary embodiments and/or shown in the figures can be combined with one another in any desired manner. Single or multiple features are interchangeable with one another in any desired manner. Combinations of features arising therefrom are intended to be understood as also covered by the disclosure of this application.

(35) Back-references in dependent claims are not intended to be understood as a relinquishment of the attainment of independent substantive protection for the features of the back-referenced dependent claims. These features may also be combined with other features in any desired manner.

(36) Features which are only disclosed in the description or features which are only disclosed in the description or in a claim in conjunction with other features may in principle be of independent significance essential to the invention. They may therefore also be individually included in claims for the purpose of delimitation from the prior art.

(37) The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.