Electric drive

Abstract

The invention relates to an electric drive (1), comprising an electric machine (2), an inverter (3) and an intermediate circuit capacitor (C), the intermediate circuit capacitor (C) being formed by at least two capacitors (Cx1, Cx2) connected in series, a center tap between the capacitors (Cx1, Cx2) forming a neutral point (NP), the electric drive (1) having a drive control device (6) which is designed such that the drive control device (6) is electrically connected to the inverter (3). The electric drive (1) has a single-phase network connection (5) with a phase line (L) and a zero conductor (N), the phase line (L) being connected to a star point (S) of the electric machine (2) and the zero conductor (N) being connected to a neutral point (NP) of the intermediate circuit capacitor (C), wherein the regulation for the supply of electrical energy from the single-phase network connection (5) is integrated into the drive regulation device (6).

Description

Technical Field

[0001] The invention relates to an electric drive. Background Art

[0002] Electric drives are known in a variety of designs for a wide variety of applications.

[0003] A common design of an electric drive comprises an electric machine, an inverter and an intermediate circuit capacitor, wherein the intermediate circuit capacitor is formed by at least two capacitors connected in series, wherein a center tap between the capacitors forms a neutral point. The electric drive has a drive control device which is designed such that the inverter is controlled as a function of input parameters in order to generate a desired drive torque, for example. In this case, the intermediate circuit capacitor can be connected to a battery as an energy source.

[0004] There is a desire to also use energy from the electrical AC voltage network to supply the drive, wherein the AC voltage is then converted into a DC voltage via a separate rectifier and used to charge the intermediate circuit capacitor, for example. Summary of the invention

[0005] The invention is based on the technical object of creating an electric drive in which single-phase mains charging is possible with low circuit technology expenditure.

[0006] The solution to this technical problem is achieved by the electric drive described below.

[0007] For this purpose, the electric drive comprises an electric machine, an inverter and an intermediate circuit capacitor, wherein the intermediate circuit capacitor is formed by at least two capacitors connected in series, wherein the center tap between the capacitors forms the neutral point. The electric drive has a drive control device, which is designed in such a way that the inverter is controlled according to the input parameters. In this case, the electric drive has a network connection with a phase line and a neutral conductor (Nullleiter, sometimes called a neutral line), wherein the phase line is connected to the star point of the electric machine and the neutral conductor is connected to the neutral point of the intermediate circuit capacitor, wherein the regulation for the supply of electrical energy from the single-phase network connection is integrated into the drive control device. This allows a very simple integration without the need for additional components, wherein only the star point of the electric machine or the neutral point of the intermediate circuit capacitor must be pulled out. Obviously, in the case of a positive current in the winding of the electric machine, the high-side transistor is turned on (durchschalten, sometimes called switched on), and in the case of a negative current, the low-side transistor is turned on, thereby charging the intermediate circuit capacitor and charging the battery connected thereto if necessary.

[0008] The single-phase mains connection preferably has a ground connection which is connected to a ground connection of the electric drive.

[0009] In another embodiment, the drive control device is designed as a DQ control device with an additional zero current control, wherein the zero current is the current through all windings of the electric machine, which is not equal to zero at least in the case of AC charging. The term "zero current" is derived from the fact that in pure motor operation, it is usually assumed that the current through the windings is zero. a +i b +i c = 0. Obviously, DQ regulation becomes DQZ regulation (Z=zero), that is, the zero current usually ignored in drive regulation is regulated as active charging current here.

[0010] In another embodiment, the line of the single-phase mains connection is connected to the EMC filter, from which the line of the single-phase mains connection is led to the star point and the mains connection. The advantage is that the connection is easily accessible from the EMC filter, since all necessary connections (star point (Sternpunkt, sometimes called star connection), neutral point, ground) are present there. For example, Y capacitors are arranged in the EMC filter, which are connected from the line leading the voltage (spannungsführendenLeitungen, sometimes called live wire) to the ground.

[0011] In one embodiment, the drive control device is designed such that in AC charging operation the charging power to be set and the network voltage value are calculated as input variables and from this the zero current to be set as the charging current for the intermediate circuit capacitor.

[0012] In another embodiment, the drive control device is designed such that an AC charging process is carried out simultaneously and a drive torque is generated. Thus, for example, a fan or a heat pump can be operated and charged at the same time. Obviously, the drive control device calculates the d, q and z currents.

[0013] In an alternative embodiment, the drive control device is designed in such a way that no drive torque is generated in AC charging operation. In certain applications, for example in electric drives of electric or hybrid vehicles, no drive torque should be generated in AC charging operation. In this case, the design of the drive control device is simplified because the zero current is zero in the driving situation and the d and q currents are zero in AC charging operation.

[0014] As a result, the electric drive is suitable for a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is then explained in more detail based on preferred embodiments.

[0016] Figure 1 shows a schematic diagram of an electric drive, and

[0017] Figure 2 A schematic block circuit diagram of a drive regulating device is shown. DETAILED DESCRIPTION

[0018] Figure 1 Schematically, an electric drive 1 is shown in FIG. The electric drive 1 has a three-phase electric motor 2 with a star point S. In addition, the electric drive 1 has an inverter 3, which is symbolically represented by six switching elements (Schaltelement, sometimes referred to as switching elements) S1-S6, which are connected in three half bridges, wherein the center taps of the three half bridges are connected to the three phases of the electric motor 2. Depending on the application, the switching elements S1-S6 can be designed as power transistors (for example MOSFETs or IGBTs), wherein the technology (Si, SiC, GaN) can also be selected application-specifically. In addition, the electric drive 1 has an intermediate circuit capacitor C, which consists of two capacitors C x1 ,C x2 A series connection is formed, wherein the center tap forms the neutral point NP. Here, an EMC filter 4 is provided, which has various filters in order to reduce the reaction to the AC voltage network on the one hand and to reduce the interference radiation of the electric drive 1 on the other hand. In addition, the electric drive 1 has a single-phase network connection 5, which has a phase line L, a zero conductor N as a return conductor and a ground line PE for grounding. The three lines L, N and PE mentioned are led to the EMC filter 4 and are distributed from there. The phase line L is connected to the star point S, and the neutral conductor (Neutralleiter, sometimes called neutral line) N is connected to the neutral point NP. The ground line PE is connected to the ground connection of the electric drive 1. Here, the three-phase current i is measured at the center tap of the half bridge. a ,i b ,i c and voltage U a ,U b ,U c Here, U n is the network voltage present at the network connection 5. Furthermore, the voltage U at the intermediate circuit capacitor C is determined. ZK+ and U ZK- .

[0019] The switching elements S1-S6 are then actuated via the drive control device 6, wherein the drive control device 6 is Figure 2 Here, the drive control device 6 has a reference calculation unit 7, which is composed of an input variable U ZK+ , U ZK- , U n , n, m* and p* to calculate the three current components i d* 、iq* and i z* , where n is the speed of the motor 2, m* is the rated torque (Soll-Dreh moment, sometimes called theoretical torque) of the motor 2, and p* is the rated charging power. d* and i q* The current components can be determined as in the known DQ control, where i z* For example, OK. Here, is the network voltage U n In parallel, a DQZ transformation 8 takes place, which transforms the three measured phase currents i a ,i b ,i c Transform into i d 、i q and i z Then the difference i d* -i d 、i q* -i q and i z* -i z They are supplied to regulators 9, 10 and 11 respectively. In addition, a pre-control part (Vorsteuerung, sometimes called feedforward control part) 12 and a disturbance variable compensation part 13 are provided, wherein the disturbance variable for zero voltage is the network voltage, that is, U zs =U n (Here, the subscript s stands for the disturbance variable). The precontrol unit 12 takes into account the mutual inductance influence. Since three currents must be considered instead of two currents compared to the conventional DQ control, three three-dimensional characteristic curve families are obtained for the mutual influence of the inductance (instead of the two two-dimensional characteristic curve families in the DQ control). In this case, the following generally applies:

[0020] U zv =L zd (i d＊ ,i q＊ ,i z＊ )·l d＊ 2+L zq (i d＊ ,i q＊ ,i z＊ )·l q＊ 2 +L zz (i d＊ ,i q＊ ,i z＊ ) z＊ 2

[0021] Obviously, L zd Considering L zAffected by the d component, and L zq Considering the influence of q component, L zz It's self-feeling.

[0022] The voltage U obtained in this way d , U q and U z undergoes an inverse DQZ transformation 14 so that as a result the three voltages U a ,U b ,U c Exists at three half bridges.

[0023] With the aid of the drive control device 6 , the setpoint torque m* can also be adjusted during AC charging operation.

[0024] If, on the other hand, no setpoint torque m* is generated during AC charging operation, the control is simplified since no zero current (i z =0) and in AC charging operation it is i d =i q = 0. In this case, it is obvious that in AC charging operation, all high-side switching elements S1 , S3 , S5 and all low-side switching elements S2 , S4 , S6 are switched synchronously in the same manner.

[0025] As a result, single-phase AC charging operation can be integrated into the electric drive by simple adaptation, wherein a hybrid operation (AC charging+motor drive) is also possible.

[0026] Reference Numbers List

[0027] 1 Driver

[0028] 2 Motor

[0029] 3 Inverter

[0030] 4EMW filter

[0031] 5Network connection department

[0032] 6. Drive adjustment

[0033] 7 Reference Calculation Department

[0034] 8DQZ conversion unit

[0035] 9,10,11 Regulator

[0036] 12Pre-control unit

[0037] 13Interference parameter compensation unit

[0038] 14DQZ conversion unit

[0039] S star point

[0040] S1-S6 switch elements

[0041] C Intermediate circuit capacitor

[0042] C x1 ,C x2 Capacitors

[0043] L phase line

[0044] N zero conductor

[0045] PE ground wire

[0046] NP Neutral Point

Claims

1. An electric drive (1) comprising an electric machine (2), an inverter (3) and an intermediate circuit capacitor (C), wherein the intermediate circuit capacitor (C) is connected via at least two capacitors (C x1 ,C x2 ) is formed, wherein the capacitor (C x1 ,C x2 ), wherein the center tap between the inverter (3) and the drive (1) forms a neutral point (NP), wherein the electric drive (1) has a drive control device (6) which is designed in such a way that the inverter (3) is actuated as a function of input parameters, Features The electric drive (1) has a single-phase mains connection (5) with a phase conductor (L) and a neutral conductor (N), wherein the phase conductor (L) is connected to the star point (S) of the electric machine (2) and the neutral conductor (N) is connected to the neutral point (NP) of the intermediate circuit capacitor (C), wherein the control for the supply of electrical energy from the single-phase mains connection (5) is integrated into the drive control device (6).

2. The electric drive according to claim 1, characterized in that The single-phase mains connection (5) has a ground conductor (PE) which is connected to a ground connection of the electric drive (1).

3. The electric drive according to claim 1 or 2, characterized in that: The drive control device (6) is designed as a DQ control device with an additional zero current control, wherein the zero current (i z ) is the current through all windings of the electric machine (2), which is not equal to zero at least in AC charging operation.

4. The electric drive according to claim 1, characterized in that The lines (L, N, PE) of the single-phase network connection part (5) are connected to the EMC filter (4), and the lines (L, N, PE) of the single-phase network connection part (5) are led from the EMC filter to the star point (S) and the neutral point (NP).

5. The electric drive according to any one of the preceding claims, characterized in that The drive control device (6) is designed in such a way that, in AC charging operation, the charging line (p*) to be regulated and the network voltage (U n ) and from this calculates the zero current (i ) to be adjusted as the charging current for the intermediate circuit capacitor (C) z ).

6. The electric drive according to any one of the preceding claims, characterized in that The drive control device (6) is designed in such a way that an AC charging process and a generation of a drive torque (m*) are carried out simultaneously.

7. The electric drive according to any one of claims 1 to 5, characterized in that The drive control device (6) is designed in such a way that no drive torque (m*) is generated during the AC charging process.

8. The electric drive according to claim 7, characterized in that The electric drive (1) is designed as a drive for an electric or hybrid vehicle.

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