DE102011075392A1 - Method and device for controlling an electric machine - Google Patents

Abstract

The present invention relates to a method for controlling an electrical machine, in particular a synchronous machine, the electrical machine being supplied with one or more phases by means of an inverter (32), the inverter (32) correspondingly being switched on by means of a control signal (39, 44). or multiphase, indirectly or directly, and wherein the electrical machine is energized by the inverter (32) in accordance with the control signal (39, 44), at least one physical variable (74, 76) of the control signal (39, 44) being detected and a phase voltage (U12, U23, U31) of the electrical machine is estimated on the basis of the physical variable (74, 76).

Description

The invention relates to a method for controlling an electrical machine, in particular a synchronous machine, wherein the electric machine is energized by an inverter single or multi-phase, wherein the inverter is driven by a control signal corresponding to single or multi-phase indirectly or directly, and wherein the electric Machine is energized by the inverter according to the control signal.

Furthermore, the present invention relates to a device for controlling an electrical machine, in particular a synchronous machine, with an inverter, which is designed to power the electric machine single-phase or multi-phase, a control circuit, the inverter by means of a corresponding single- or multi-phase control signal indirectly or directly controls, wherein the inverter is adapted to energize the electric machine according to the control signal.

State of the art

In the field of electric motor technology, it is well known that the torque provided by an electrical machine is determined indirectly via measured electrical parameters and measured mechanical parameters, such as the speed of the motor shaft. In order to measure these electrical and mechanical parameters of the electrical machine, it is necessary to integrate detectors in the electrical machine to detect the corresponding parameters. For controlling and / or regulating the electric machine, the torque thus determined is compared with a desired value and controlled in accordance with a phase current or a phase voltage. Such a method is known, for example from the DE 10 2008 001 714 A1 ,

In the field of electric motor technology, it is also generally known to provide the phase currents of the electric machine via inverters and to control the output torque via a pulse width modulated signal or via pulse width modulated phase currents.

A disadvantage of the control method of the prior art is that the determination of the necessary parameters for the control is technically complex and it requires a large number of sensors for this determination.

The object of the present invention is therefore to provide an improved method and a corresponding device for controlling an electrical machine, in particular a synchronous machine, which is technically less complicated and offers a high degree of safety.

Disclosure of the invention

This object is achieved according to the invention in the method mentioned above in that at least one physical quantity of the control signal is detected and a phase voltage of the electrical machine is estimated on the basis of the physical quantity.

Furthermore, the above object is achieved in the aforementioned device in that detection means are provided, which are adapted to detect at least one physical quantity of the control signal and determining means are provided, which are adapted to a phase voltage based on the detected physical quantity to appreciate the electric machine.

Advantages of the invention

By the present invention, the phase voltage of an electric motor can be estimated on the basis of the control signal and thus determined without phase voltage meter, whereby the number of required sensors of the electric machine can be reduced.

In other words, the phase voltage is estimated on the basis of other detected physical quantities and can be used to control the electric machine and in particular the output torque. As a result, the electric machine is technically less expensive and can be produced more cheaply.

Further, the phase voltage can thereby be independently determined and estimated and a redundant value can be provided, whereby the safety of the drive can be increased.

The present invention may further provide an apparatus for driving an electric machine, which makes it possible to estimate the phase voltage of the electric machine, so that the electric machine need not be formed with separate voltage measuring sensors. In other words, the electric machine becomes less technically complicated by such a drive device and can be manufactured correspondingly less expensively.

It is particularly advantageous in the method according to the invention if at least one further state variable of the electric machine, in particular a phase current, a rotor position or a rotor speed is detected and, on the basis of the detected state variable and the estimated phase voltage, an output variable, in particular a delivered torque electrical machine is determined.

As a result, an output variable of the electrical machine can be determined by simple means, as a result of which the control or regulation of the electrical machine becomes more precise. It is also advantageous that the determination of the output variable, in particular of the actual torque, can be carried out independently of the specific embodiment of the electric drive. In other words, the machine-specific parameters, such as e.g. the inductance of the stator, are not taken into account to determine the actual torque. This makes the control versatile and does not have to be adapted to the respective drive. Furthermore, the drive is insensitive to parameter changes due to aging of the components, e.g. the magnet.

It is also particularly preferred if the control signal forms an input to a driver circuit which drives the inverter.

As a result, the input signal of the driver circuit, whose time characteristic is usually identical to an output signal of the driver circuit, can be detected by simple means and on the basis of which the phase voltage can be estimated.

It is alternatively preferred if the control signal forms an output signal of a driver circuit which drives the inverter.

As a result, time delays of the driver circuit or smoothings of the original signal, which are caused by the driver circuit, can be taken into account in the estimation of the phase voltage.

It is furthermore preferred if the control signal forms an input signal of the inverter.

As a result, the direct input signal can be used to control the inverter, thereby increasing the accuracy of estimating the phase voltage.

It is generally preferred for a control unit to drive a control circuit which drives the drive circuit and wherein the physical quantity is fed back to the control unit and the phase voltage is estimated by the control unit.

As a result, the overall structure can be simplified technically, since conventional circuits can be used for the individual elements of the timing chain and, in particular, a conventional microcontroller can be used as the control unit.

It is further preferred if the input signal of the driver circuit is a low voltage signal and the output signal of the driver circuit is a high voltage signal.

As a result, a high-voltage network and a low-voltage network can be physically separated from one another, and expensive isolation of the drive of the driver circuit can be dispensed with.

It is particularly advantageous if the control unit controls the control circuit by means of a clock signal and the control circuit outputs a pulse width modulated signal.

Thereby, the control unit can drive the control circuit with a usual clock signal and the control circuit generate the corresponding control signal in order to request an increased or reduced power from the electric machine.

It is furthermore preferred if the output variable of the electrical machine is determined by the control unit.

As a result, such arithmetic operations can be performed by simple arithmetic units such as e.g. a microcontroller are performed and at the same time a corresponding control signal is output from the same arithmetic unit to the control circuit.

It is further preferred if the control signal is a clocked signal and the physical quantity is a time of a rising or falling edge of the clocked signal within a period.

As a result, the physical quantity can be detected with simple means and the time profile of the phase voltage can be determined.

It is particularly preferred if the physical quantity is a time difference between the time of the rising and the falling edge of the clock signal.

As a result, the exact time profile of the phase voltage can be determined with simple means, since an energization duration of the corresponding phase is defined by the rising and the falling edge of the clock signal.

It is furthermore preferred if the detection of the physical variable is triggered by the control unit.

As a result, the measurement of the physical quantity is performed only when necessary, that is, not within each of the periods of the clock signal, whereby the technical complexity for detecting the physical quantity is reduced.

It is particularly preferred if exactly one rising and exactly one falling edge of the clock signal is detected after triggering the detection by the control unit.

In other words, the measurement of the physical quantity is triggered by the control unit and during exactly one period of the clock signal, the edges of the signal are measured.

As a result, the phase voltage can be estimated by the control unit as required and the physical quantity can only be detected as required. As a result, the technical complexity for detecting the physical size is reduced. It is understood that the features, properties and advantages of the method according to the invention also apply correspondingly to the device according to the invention or are applicable.

Brief description of the drawings

1 shows in schematic form the structure of an electrical machine;

2 shows in schematic form a device for driving the electric machine;

3 shows in schematic form a control unit for signal detection, for estimating the phase voltage and for driving a drive circuit;

4 shows a course of three drive signals for three phase currents of the electric machine; and

5 shows a schematic flow diagram of the method for detecting a positive and a negative edge of a control signal.

Embodiments of the invention

In 1 the construction of an electric machine is shown in schematic form. The electric machine is in 1 generally with 10 designated.

The electric machine 10 has three phase current conductors 12 . 14 . 16 in which three phase currents IS1, IS2 and IS3 flow. The phase current conductors 12 . 14 . 16 are with respective excitation windings 18 the electric machine 10 connected. The excitation windings 18 are connected in a star shape with each other, preferably no neutral conductor is provided.

The excitation windings 18 are in 1 labeled phase V, phase U and phase W. The phase current conductors 12 . 14 . 16 are sensors 20 . 22 . 24 assigned to measure the phase currents IS1, IS2 and IS3 and each a corresponding current signal 26 deliver. The sensors 20 . 22 . 24 are designed as ammeters. Alternatively, by means of voltmeters, strand voltages in the phase current conductors 12 . 14 . 16 be measured for control or regulation.

The sensors 20 . 22 . 24 are connected to a control unit, not shown, wherein the measured phase currents IS1, IS2 and IS3 are returned to the controller. The controller provides based on the current signals 26 a control signal to a power electronics, not shown, to the electric machine 10 to control or regulate.

In 1 Furthermore, strand voltages U12, U23 and U31 are shown, between the phase conductors 12 . 14 . 16 fall off. On the basis of the phase currents IS1, IS2 and IS3, the phase voltages U12, U23 and U31, a rotor position and a rotor speed of the in 1 not shown rotor of the electric machine 10 Can this be done by the electric machine 10 delivered torque can be calculated. For precise control of the torque output, it is necessary to know the phase currents IS1, IS2 and IS3, the phase voltages U12, U23, U31, the rotor position and the rotor speed. These quantities can be measured by means of the sensors 20 . 22 . 24 be detected and estimated via appropriate control signals.

In 2 is a driving device for driving the electric machine 10 shown schematically and generally with 30 designated.

The driving device 30 has an inverter or inverter 32 on that with the live wires 12 . 14 . 16 is connected and the Phases U, V, W provides. The inverter 32 is via supply lines 34 connected to an electric power source, not shown, such as a battery, an accumulator or a fuel cell. The inverter 32 is over the supply lines 34 supplied with a DC voltage and serves to convert the DC voltage in the three phases U, V, W and on the phase lines 12 . 14 . 16 to provide the currents IS1, IS2 and IS3 accordingly. The inverter 32 preferably has a plurality of controllable semiconductor switches in particular controllable IGBTs to convert the DC voltage into AC voltage.

The drive device 30 also has a driver circuit 36 on, over a driver line 38 with the inverter 32 connected is. The driver circuit 36 drives the inverter 32 and in particular the semiconductor switches of the inverter 32 via a driver signal 39 , The drive device 30 also has a drive circuit 40 on, via a control line 42 the driver circuit 36 controls. The drive circuit 40 controls by means of a drive signal 44 the driver circuit 36 at. The driver circuit 36 is via a signal line 46 with the drive circuit 40 via which an error signal is transmitted to the drive circuit, if the driver circuit detects an error or a malfunction. The drive device 30 also has a control unit 48 on, which is preferably designed as a microcontroller. The control unit 48 is via a control line 50 with the drive circuit 40 connected and controls these via a control signal 52 at. The control line 42 is also with the control unit 48 connected to the control signal 44 to the control unit 48 to feed back or due. The driver line 38 can via a coupler 54 with the control unit 48 be connected to the driver signal 38 to the control unit 48 due.

Basically, the control unit 48 , the drive circuit 40 associated with a low voltage range and the corresponding signals 44 . 46 . 52 are low voltage signals. The inverter 32 and the driver line 38 are associated with a high voltage region, wherein the driver signal 39 is a corresponding high voltage signal. The driver circuit 36 converts accordingly based on the low voltage drive signal 44 into the high voltage based driver signal 39 , In 2 is a demarcation between the low voltage range and the high voltage range by a line 56 indicated. To the driver signal 39 to the control unit 48 is due to the driver line 38 over the coupler 54 with the control unit 48 connected. The coupler converts the high voltage driver signal 39 in a corresponding low-voltage signal and leads it to the control unit 48 back. About the line 56 is a high voltage insulation between the high voltage range and the low voltage range indicated.

The control unit 48 controls via the control signal 52 the drive circuit 40 , The drive circuit 40 has power output stages that the drive signal 44 provide. The drive circuit 40 changes the control signal 52 For example, to achieve a dead time correction, so a compensation of switching delays of the semiconductor switches or IGBTs and thereby a short circuit in the inverter 32 to avoid or to account for hardware errors, so that the drive signal 44 in case of malfunction is suspended. Such a malfunction can, for example, via the signal line 46 from the driver circuit 36 to the drive circuit 40 be forwarded or returned.

The drive signal 44 has three different phases corresponding to the phase lines 12 . 14 . 16 on to the inverter 32 via the driver circuit 36 head for. The thus formed three-phase drive signal 44 controls the driver circuit 36 which are preferably designed as Gatedriver ICs. The driver circuit 36 generates the high voltage driver signal 39 , which is also formed three-phase, wherein the three phases of the drive signal 39 the three phases of the drive signal 44 correspond. By means of the three-phase high-voltage driver signal 39 become the semiconductor switches or the IGBTs of the inverter 32 controlled to correspondingly clocked phase currents IS1, IS2 and IS3 of the electric machine 10 provide.

The time course of the three phases of the driver signal 39 is usually identical to the time course of the three phases of the drive signal 44 ,

The drive signal 44 is sent to the control unit 48 attributed to estimate the phase voltages U12, U23 and U31 from the time courses of the three phases U, V, W of the signal, as explained in more detail below. Alternatively or additionally, the driver signal 39 to the control unit 48 be returned from the timing of the phases U, V, W of the drive signal 39 estimate the phase voltages U12, U23, U31. The driver signal 39 is usually identical to the drive signal 44 , In case of malfunction of the driver circuit 36 is via the signal line 46 an error message to the drive circuit 40 is returned, so that possibly the outputs of the drive circuit 40 be locked.

In this way, the phase voltages U12, U23, U31 of the electric machine 10 be determined without separate voltage sensors and on this basis, for example, a torque of the electric machine 10 be determined.

In 3 is the control unit 48 shown schematically. The control unit 48 has a parent clock 58 on. The control unit also has three control signal generators 60 . 62 . 64 on which the three phases U, V, W of the control signal 52 provide. The control unit 48 also has three measurement interfaces 66 . 68 . 70 on, with the control line 42 or the driver line 38 are connected to the three phases U, V, W of the output signal 44 or the driver signal 39 capture.

The control unit 48 also has an interface 72 on, via the measuring signals of the sensors 20 . 22 . 24 , Measurements of rotor position and rotor speed is supplied to the control unit. The clock generator 58 is over a clock line 74 with the signal generators 60 . 62 . 64 , the measurement interfaces 66 . 68 . 70 and the interface 72 connected to signal generation via the signal generators 60 . 62 . 64 , the signal acquisition via the measurement interfaces 66 . 68 . 70 and to synchronize the detection of phase currents, rotor position and rotor speed. The signals synchronized in this way are read into another module (eg a general-purpose timer array) in order to evaluate the measuring signals and to estimate the phase voltage from the measured values.

In 4 is the time course of the phases U, V, W of the driver signal 39 , the drive signal 44 and / or the control signal 52 shown schematically. The phases U, V, W each have a square wave signal with a positive edge 74 and a negative edge 76 , The phases U, V, W each have a positive edge in a period T. 74 and a negative edge 76 on. The phases U, V, W each form a pulse width modulated signal, wherein the distance between the edges 74 . 76 in each of the periods and each of the phase signals U, V, W varies a different distance between the edges 74 . 76 within each of the periods T has.

For evaluating the phases U, V, W of the signals 39 . 44 . 52 After a pulse width modulated cycle has been started with the period T, after a predetermined time which is smaller than the period T, a sequence for evaluating the phases U, V, W is started. The time at which the process is started is in 4 indicated schematically and with 78 designated. In the evaluation, the measurement interfaces are first 66 . 68 . 70 read out the measuring interfaces 66 . 68 . 70 then re-programmed and the measurement results of the phase currents, the rotor position, the rotor speed from the interface 72 read. The measurement interfaces 66 . 68 . 70 are configured to time the next rising edge 74 and the subsequent falling edge 76 , ie the next period T. The measurement interfaces are configured in such a way that the respective measurements are carried out at the same time and are started when the timer 58 provides a corresponding signal.

The measurement interfaces 66 . 68 . 70 are configured to have only one of the rising edges 74 and one of the falling flanks 76 to capture. Thereafter, these are deactivated until they are replaced by a new drive signal of the clock generator 58 be activated or initialized. This activation can take place in the following period T, as is the case with 80 is shown. For example, the measurement interfaces 66 . 67 . 70 Therefore, the edges are operated only once and not continuously in each of the periods T 74 . 76 to capture.

From the time difference between a time t2 of one of the falling edges 76 and a time t1 of one of the rising edges 74 then becomes the duration of the H level 82 or the high phase of the corresponding signal U, V, W determined. The fact that the period T is known and invariant can be obtained by dividing the ratio of the H level 82 and the period T are calculated, the duty cycle.

From the measured duty cycle, the phase voltage U12, U23, U31 can be estimated. Because the semiconductor switches of the inverter 32 the outputs, so the phase lines 12 . 14 . 16 alternating with a high voltage potential (eg 400 V) and connect the ground potential, resulting in an approximately sinusoidal phase voltage from the formula U = (DC-0.5) × UDC, where U is the phase voltage, DC the duty cycle and UDC the high voltage applied to the phase lines 12 . 14 . 16 is created. The value 0.5 is subtracted from the duty cycle since the high voltage is always positive (typically 200V to 400V). A virtual zero position of the voltage is defined by DC = 0.5, which corresponds to 0.5 × UDC.

The measurement of the clock ratio usually takes place every two periods T of the phase signals U, V, W, as shown in FIG 4 is shown. Such monitoring is sufficient because of the electrical machine 10 delivered torque rather slowly changes. If the clock ratio is to be recorded for each of the periods, then per Phase twice as much hardware will be provided and operated with a time delay.

The invention is preferably used in electrically driven vehicles, in particular electric vehicles or hybrid vehicles.

In 5 is a schematic flow diagram of the method steps for estimating the phase voltages U12, U23, U31 shown. The procedure is triggered by the clock 58 as shown at S1. This initiates the process at S2. After initiating the procedure, three steps are executed in parallel, namely the readout of the measured values of the measuring interfaces 66 . 68 . 70 as shown at S3, perform the measurement of the phase currents IS1, IS2, IS3 as shown at S4 and perform the measurement of the rotor speed and the rotor position as shown at S5. After the measurement results from the measurement interfaces 66 . 68 . 70 are read, the measurement interfaces 66 . 68 . 70 at S6, reinitialized or configured for a subsequent measurement to go to the edges in the following period 74 . 76 capture.

The steps S1 to S6 are executed within a first period T. In the following period T, the measurement interfaces capture 66 . 68 . 70 at S7 the rising edge 74 and at S8 the subsequent falling edge 76 , After the end of the second period, in the subsequent period at S2 the method is reinitialized and at S3 the measured values are from the measurement interfaces 60 . 62 . 64 read. This allows the rising and the falling edge 74 . 76 the signals 39 . 44 . 52 Accordingly, within two periods T are detected and estimated from the measured values, the phase voltages U12, U23, U31.

The phase voltages can thus be determined independently of the drive-specific parameters, so that the calculations based on the phase voltages do not have to be adapted drive-specific. For example, the inductance of the stator need not be known. This determination is also insensitive to parameter changes due to aging of components, e.g. the magnet. Furthermore, this method can be used as a redundant path for determining the phase voltages, whereby the security can be increased.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102008001714 A1 [0003]

Claims (14)

Method for controlling an electric machine ( 10 ), in particular a synchronous machine, wherein the electric machine ( 10 ) by means of an inverter ( 32 ) is energized one or more phases, wherein the inverter ( 32 ) by means of a control signal ( 39 . 44 ) is driven directly or indirectly according to one or more phases, and wherein the electric machine ( 10 ) by the inverter ( 32 ) according to the control signal ( 39 . 44 ) is energized, characterized in that at least one physical quantity ( 74 . 76 ) of the control signal ( 39 . 44 ) is detected and a phase voltage (U12, U23, U31) of the electric machine ( 10 ) on the basis of physical size ( 74 . 76 ) is estimated. Method according to claim 1, wherein at least one further state quantity (IS1, IS2, IS3) of the electrical machine ( 10 ), in particular a phase current (IS1, IS2, IS3), a rotor position or a rotor speed is detected and on the basis of the detected state variable (IS1, IS2, IS3) and the estimated phase voltage (U12, U23, U31) an output variable, in particular a output torque, the electric machine ( 10 ) is determined. Method according to claim 1 or 2, wherein the control signal ( 39 . 44 ) an input signal ( 44 ) a driver circuit ( 39 ) forming the inverter ( 32 ) drives. Method according to claim 1 or 2, wherein the control signal ( 38 . 44 ) an output signal ( 39 ) a driver circuit ( 36 ) forming the inverter ( 32 ) drives. Method according to one of claims 1 to 4, wherein the control signal ( 38 . 44 ) an input signal ( 39 ) of the inverter ( 32 ). Method according to one of claims 1 to 5, wherein a control unit ( 48 ) a control circuit ( 40 ) which drives the driver circuit ( 36 ) and the physical size ( 74 . 76 ) is returned to the control unit and the phase voltage (U12, U23, U31) is estimated by the control unit. Method according to one of claims 3 to 6, wherein the input signal ( 44 ) the driver circuit ( 36 ) is a low voltage signal and the output signal ( 39 ) the driver circuit ( 36 ) is a high voltage signal. Method according to claim 6 or 7, wherein the control unit ( 48 ) the control circuit ( 40 ) by means of a clock signal ( 52 ) and the control circuit ( 40 ) a pulse width modulated signal ( 44 ). Method according to one of claims 6 to 8, wherein the output of the electric machine ( 10 ) by the control unit ( 48 ) is determined. Method according to one of claims 1 to 9, wherein the control signal ( 39 . 44 ) is a clocked signal and the physical quantity ( 74 . 76 ) a time (t1, t2) of a rising or falling edge ( 74 . 76 ) of the clocked signal ( 52 ) within one period (T). Method according to claim 10, wherein the physical quantity ( 74 . 76 ) a time difference between the time (t1) of the rising edge ( 74 ) and the time (t2) of the falling edge ( 76 ) of the control signal ( 39 . 44 ). Method according to one of claims 6 to 11, wherein the detection of the physical quantity ( 74 . 76 ) by the control unit ( 48 ) is triggered. Method according to claim 12, wherein after triggering the detection by the control unit ( 48 ) exactly one rising edge ( 74 ) and exactly one falling edge ( 76 ) of the clock signal ( 38 . 44 ) is detected (S7, S8). Device for controlling an electric machine ( 10 ), in particular a synchronous machine, with an inverter ( 32 ), which is adapted to the electrical machine ( 10 ) to energize one or more phases, a control circuit ( 36 . 40 ), which is the inverter ( 32 ) by means of a corresponding single- or multi-phase control signal ( 39 . 44 ) directly or indirectly, the inverter ( 32 ) is adapted to the electric machine ( 10 ) according to the control signal ( 39 . 44 ), characterized by detection means ( 66 . 68 . 70 ), which are designed to be at least one physical variable ( 74 . 76 ) of the control signal ( 39 . 44 ) and determination means which are designed on the basis of the detected physical quantity ( 74 . 76 ) a phase voltage (U12, U23, U31) of the electric machine ( 10 ) appreciate.

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