DE102005043576A1 - Method for operating an electrical machine - Google Patents

Abstract

Method for operating an electrical machine (M) which has at least two electrically separate stator windings (W1, W2), the first stator winding (W1) being fed via a first partial converter (U1) and the second stator winding (W2) via a second partial converter (U2) is fed. The partial converters (U1, U2) are controlled by means of offset clocked signals (PWM1, PWM2, PWM3).

Description

The The invention relates to a method for operating an electrical Machine having at least two electrically separate stator windings wherein the first stator winding via a first partial converter is fed, and the second stator winding via a second partial converter is fed, and wherein the first and the second partial converter be controlled by means of clocked signals.

such Methods for operating an electric machine, for example as a component of electronic control in vehicles, such as For example, hybrid vehicles or electric vehicles used.

hybrid vehicles are vehicles that are over two have separate drive systems. As a rule, these are an electric machine and an internal combustion engine, which are coordinated by an electronic control. The electronic Control exists u. a. from a drive in the drive train the hybrid vehicle is arranged and optionally as a rectifier or inverter can be operated and the electric machine Provides energy in a suitable form.

Usually, electrical machines are designed as multiphase machines with a number of phases _ph , for example three phases (n _ph = 3). Accordingly, a voltage source must be connected to the electric machine via n _ph electrical connections, for example three electrical connections. However, electrical machines may also have a different number of phases, such as four, and correspondingly many electrical connections.

at many applications comes for the electrical operation of such an electric machine Inverter used. An inverter is typically constructed that the DC voltage of a DC link capacitor by switches, such as semiconductor devices or switches, on the Stator windings of the electric machine is switched. This usually happens clocked, d. H. pulse width modulated signals actuate the Switches supplemented by antiparallel diodes. The DC link capacitor is over a supply line with a DC voltage source, such as a battery connected.

Around that needed To generate torque of the electric machine, high motor phase currents are required. To switch these are elaborate To dimension switch, for example by parallel connection several switches with lower current carrying capacity, such as IGBTs or MOSFETs. Such parallel circuits are often not easy to master.

Especially, if the capacity of the DC link capacitor is small, arise in the switching operations over- and Undervoltage peaks which, on the one hand, make it difficult to regulate the motor phase currents, on the other on the supply line to the DC voltage source so-called Generate ripple currents. The DC link voltage breaks down, the break in the DC link voltage the inverter is larger, the bigger the Motor phase current is switched. Furthermore, such ripple currents are disadvantageous for example, because they are warming the DC voltage source via can cause their internal resistance.

task The present invention is a method for operating a provide electrical machine, which also at high motor phase currents a optimal operation of the electric machine allows.

These The object is solved by the features of claims 1 and 13. advantageous Further developments can be found in the dependent claims.

The Stator winding of the electric machine, in particular a three-phase Three-phase motor, is divided into several individual stator windings. The electric machine has at least two electrically isolated Stator windings on. The separated stator windings become too so-called "partial motors" summarized. Each sub-engine can now be assigned a separate sub-converter. Each sub-converter switches the motor phase currents of the corresponding sub-motor, which was assigned to him. Thus, by the partial converter or its switch is not the motor phase currents of the entire electric motor to switch, but only the motor phase currents of the sub-motor. These motor phase currents of the partial motors are smaller than the motor phase currents of the whole according to the number of partial motors The electric motor. It does not matter if the part converter in separate housings or in a housing are installed. Are the partial converters installed in a housing, so can different components are shared, such as the DC link capacitor or the control or signal processing unit. Of course can be an electric machine in any number of sub-motors and Thus partial converters are separated or divided. Furthermore is it also possible that in the electric motor more stator windings of a motor part in parallel be interconnected.

According to the invention, the first and the second partial converter controlled in each case by means of clocked signals, wherein the control takes place by means of offset clocked signals. The partial converters are therefore clocked offset, which means that the control signals for the switches of the partial converter are generated so that they are not switched simultaneously, but in succession.

Corresponding the number of phases of a stator winding of the electric machine becomes the associated one Partial converter controlled by clocked signals. Indicates the first Stator winding, for example, two phases, then becomes the first Partial converter with at least a first and a second clocked Signal controlled. Likewise, the second partial converter with at least controlled a first and a second clocked signal when the second stator winding also has two phases. Increases the number of phases of a stator winding, it increases according to the number of clocked signals of the associated subcircuit. The clocked signals of both the first subcommand as well of the second subcircuit also have centers of symmetry.

A preferred embodiment The invention consists in that the centers of symmetry of the clocked Signals of the first partial converter in relation to the symmetry centers of the clocked signals of the second subcommander are offset.

In particular, the offset V of the centers of symmetry V = T _PWM / m is _part , where T _{PWM is} the period of the basic signal clock and m _{part is} the number of sub-motors.

But the displacement V of the symmetry centers can also V <T _PWM / m or _{in part} V> T _PWM / m _{in part} be where T _PWM is the period of the signal and the basic _clock-m is the number of sub-engines.

Preferably the offset V of the centers of symmetry can additionally be varied over time.

The Control signals for the partial converter, or the switches of the partial converter, are advantageously generated symmetrically pulse width modulated, d. H. the clocked signals are symmetric pulse width modulated signals. It can, however, too other clocked signals are used.

The first phase of the first and second stator winding is the first clocked signal of the first and second partial converter assigned and the second phase of the first and second stator winding is the second clocked signal of the first and second partial converter assigned.

In particular, each clocked signal, and thus each phase, a duty cycle T of T = PWM _on / T _PWM assigned, where PWM _on the duration of the on state of the respective clocked signal and T _{PWM is} the period of the basic signal clock.

With The first clocked signal of the first one has a particular advantage Partial converter and the first clocked signal of the second partial converter the same duty cycle as well as the second clocked signal of the first subcircuit and the second clocked signal of the second subcircuit have the same duty cycle. This means that the first phase of the first part of the engine with the same clocked signal, d. H. Signal with the same duty cycle, controlled becomes like the first phase of the second part engine. Be the duty cycle the same, Thus, the entire structure of the electrical machine or the partial converter be realized with less effort. The duty cycles for example a partial motor with a three-phase current controller calculated and can then for all other sub-motors are used.

It but it is also possible the first phase of the partial motors with clocked signals with different duty cycles head for. The advantage of differently selected duty cycles is that asymmetries of the partial motor stator windings, for example, by controlling the motor phase currents of the partial motors balanced can be. Furthermore you can the switches of all partial converters operated closer to their power limit become.

Preferably the electric machine is designed as a three-phase motor and for the Installation provided in a motor vehicle.

In The following description describes the features and details the invention in conjunction with the accompanying drawings with reference to embodiments explained in more detail. there are features and relationships described in individual variants in principle all embodiments transferable. In the drawings show:

1 a circuit arrangement with DC voltage source, DC link capacitor, inverter and electrical machine;

2 a schematic representation of a three-phase motor with two separate stator windings;

3 a schematic representation of a three-phase motor with two separate stator windings and two separate partial converters;

4 the temporal course of clocked signals of a partial converter;

5 the timing of clocked signals of several partial converter with staggered centers of symmetry.

to better understandability the description will be for like elements in the figures use like reference numerals.

1 shows a circuit arrangement with a DC voltage source G, a DC link capacitor K, a converter U and an electrical machine M.

The electric machine M is designed as a multi-phase machine with a number of three phases. Accordingly, a voltage source G must be connected to the electric machine M via three electrical connections. The inverter U is arranged between the voltage source G, which is designed, for example, as a battery, and the electrical machine M. The inverter U is constructed so that the DC voltage of the DC link capacitor K through the switch S to the electric machine M, in particular the in 1 not shown stator windings, is switched. This is usually clocked, ie pulse width modulated signals actuate the switch S, which are supplemented by the anti-parallel diodes D. The capacitor K is connected via the leads L to the voltage source G.

2 shows a schematic representation of a three-phase motor M with two separate stator windings W1 and W2. The separate stator windings W1 and W2 are combined to form so-called "partial motors." The stator winding W1 corresponds to a partial motor 1, not shown, and the stator winding W2 to a partial motor 2 (not shown).

3 shows a schematic representation of a three-phase motor M with two separate stator windings W1 and W2 and two separate partial converters U1 and U2. As already stated, the separate stator windings W1 and W2 are combined into partial motors. Each partial motor or stator winding can now be assigned a separate partial converter. The stator winding W1 is connected to the partial converter U1 and the stator winding W2 to the partial converter U2. The partial converters U1 and U2 are each connected to the voltage source G.

Everyone Partial converter switches the motor phase currents of the corresponding part motor, which was assigned to him. The partial converter U1 switches the stator winding W1 and the partial converter U2 switches the stator winding W2. Consequently are not the motor phase currents of the entire by the partial converter U1 or U2 Electric motor M to switch, but only the motor phase currents of the sub-motor W1 or W2.

4 shows the time course t of the clocked signals PWM1, PWM2 and PWM3 a partial converter, not shown. The clocked signals PWM1, PWM2 and PWM3 have the centers of symmetry Z1, Z2 and Z3. Within the centers of symmetry the signals PWM1, PWM2 and PWM3 have the same state. Both in the center of symmetry Z1 and in the centers of symmetry Z2 and Z3, the signals PWM1, PWM2 and PWM3 are in the on state. As in 4 to see, the drive signals PWM1, PWM2 and PWM3 are generated symmetrically pulse width modulated. T _PWM designates the period of the basic signal clock.

5 shows the time course of the clocked signals PWM1, PWM2 and PWM3 of four, not shown, partial converters and thus four partial motors Mot1, Mot2, Mot3 and Mot4 with offset centers of symmetry Z1 and Z2. Each sub-motor Mot1 to Mot4 is controlled by offset clocked signals. The drive signals PWM1 to PWM3 are generated so that the partial motors Mot1 to Mot4 are not switched simultaneously, but in succession. This occurs in particular in that the centers of symmetry Z1 and Z2 of the clocked signals PWM1 to PWM3 of the first partial motor Mot1 are offset from the centers of symmetry Z1 and Z2 of the clocked signals PWM1 to PWM3 of the partial motors Mot2, Mot3 and Mot4. The offset V of the centers of symmetry of the four sub-motors Mot1 to Mot4 is equal to V = T _PWM / m _part where T _{PWM is} the period of the basic signal clock and m _{part is} the number of sub-motors. Furthermore, in 5 It can be seen clearly that the respective first clocked signals PWM1 of the four partial motors Mot1 to Mot4 are identical, ie they have the same duty cycle. Likewise, the respective second and third signals PWM2 and PWM3 are identical, ie they also have the same duty cycle. The duty cycle T results from T = PWM _on / T _PWM , where PWM _on the duration of the on state of the respective clocked signal and T _{PWM is} the period of the basic signal clock.

LIST OF REFERENCE NUMBERS

• D

  diode

  G

  DC voltage source

  I

  Motor phase current

  K

  Link capacitor

  L

  supply

  M

  Electric machine (Three phase motor)

  mot1

  Partial motor 1

  Mot2

  Partial motor 2

  MOT3

  Partial motor 3

  Mot4

  Partial motor 4

  m _part

  Number of sub-motors

  PWM1

  Signal 1 (pulse width modulated generated signal)

  PWM 2

  Signal 2 (pulse width modulated generated signal)

  PWM3

  Signal 3 (pulse width modulated generated signal)

  PWM _on

  Signal in switched on Status

  S

  switch

  T

  duty cycle

  T _PWM

  Period of the Signal basic clock

  t

  Time

  U

  inverter

  U1

  Partial converter 1

  U2

  Partial converter 2

  V

  transfer

  W1

  Stator winding 1 (partial motor 1)

  W2

  Stator winding 2 (partial motor 2)

  Z1

  Symmetry Center 1

  Z2

  Symmetry Center 2

  Z3

  Symmetry Center 3

Claims (15)

Method for operating an electrical machine (M), which has at least two electrically separate stator windings (W1, W2), wherein the first stator winding (W1) is fed via a first partial converter (U1), and the second stator winding (W2) via a second Partial converter (U2) is fed, and wherein the first and the second partial converter (U1, U2) by means of clocked signals (PWM1, PWM2, PWM3) are controlled, characterized in that the first partial converter (U1) and the second partial converter (U2) controlled by offset clocked signals (PWM1, PWM2, PWM3). Method according to claim 1, characterized in that that the first partial converter (U1) with at least a first and a second clocked signal (PWM1, PWM2) is controlled and the second partial converter with at least a first and a second clocked signal (PWM1, PWM2) is controlled. Method according to claim 1 or 2, characterized that the clocked signals (PWM1, PWM2) of the first and second Partial converter (U1, U2) have symmetry centers (Z1, Z2, Z3). Method according to claim 3, characterized in that the centers of symmetry (Z1, Z2, Z3) of the clocked signals (PWM1, PWM2, PWM3) of the first partial converter (U1) with respect to the centers of symmetry (Z1, Z2, Z3) of the clocked signals (PWM1, PWM2, PWM3) of the second partial converter (U2) are offset. A method according to claim 3 or 4, characterized in that for the displacement (V) of the centers of symmetry (Z1, Z2, Z3) V = T _PWM / m _part applies. A method according to claim 3 or 4, characterized in that for the displacement (V) of the centers of symmetry (Z1, Z2, Z3) V <T _PWM / m _part applies. A method according to claim 3 or 4, characterized in that for the displacement (V) of the centers of symmetry (Z1, Z2, Z3) V> T _PWM / m _part applies. Method according to one of claims 3 to 7, characterized that the displacement (V) of the centers of symmetry is varied over time. Method according to one of the preceding claims, characterized characterized in that the clocked signals (PWM1, PWM2, PWM3) symmetric pulse width modulated Signals are. A method according to claim 1, characterized in that each clocked signal (PWM1, PWM2, PWM3) a duty cycle (T) T = PWM _on / T _{PWM is} assigned. Method according to claim 10, characterized in that that the first clocked signal (PWM1) of the first partial converter (U1) and the first clocked signal (PWM1) of the second partial converter (U2) the same duty cycle (T) and / or the second clocked signal (PWM2) of the first Partial converter (U1) and the second clocked signal (PWM2) of the second Subconductor (U2) have the same duty cycle (T). Method according to claim 10 or 11, characterized that the first clocked signal (PWM1) of the first partial converter (U1) and the first clocked signal (PWM1) of the second subcircuit (U2) different duty cycles (T) and / or the second clocked signal (PWM2) of the first Partial converter (U1) and the second clocked signal (PWM2) of the second Subconductor (U2) have different duty cycles (T). Arrangement for implementing the method of operation an electric machine (M) according to one of claims 1 to 12th Arrangement according to claim 13, characterized the electric machine (M) is a three-phase motor. Arrangement according to claim 13 or 14, characterized that the electric machine (M) for installation in a motor vehicle is provided.