阅读说明：本技术 用于三相交流电机的驱动控制器 (Drive controller for three-phase AC motor ) 是由 P·席尔默 D·格罗泽 于 2019-02-21 设计创作，主要内容包括：提出一种用于三相交流电机的驱动控制器,所述驱动控制器包括：逆变器,其包括多个开关,以用于在三相交流电机的线圈上产生三相交流电压；以及控制装置,用于基于脉宽调制控制所述逆变器的各开关,其中,所述控制装置设置为用于在一个开关周期内在使用开关模式的情况下控制所述各开关,其中,所述开关模式由两个主动的电压空间矢量和多个零矢量组成,其中,所述多个零矢量在所述开关模式内变化。(A drive controller for a three-phase alternating current machine is proposed, the drive controller comprising: an inverter including a plurality of switches for generating a three-phase alternating current voltage on coils of a three-phase alternating current motor; and a control device for controlling the switches of the inverter on the basis of pulse width modulation, wherein the control device is arranged for controlling the switches in a switching cycle using a switching pattern, wherein the switching pattern consists of two active voltage space vectors and a plurality of zero vectors, wherein the plurality of zero vectors vary within the switching pattern.)

1. A drive controller for a three-phase ac motor, comprising:

an inverter including a plurality of switches for generating a three-phase alternating current voltage on coils of a three-phase alternating current motor; and

control means for controlling the switches of the inverter on the basis of pulse width modulation,

characterized in that the control means are arranged for controlling the switches in a switching cycle using a switching pattern, wherein the switching pattern consists of two active voltage space vectors and a plurality of zero vectors, wherein the plurality of zero vectors vary within the switching pattern.

2. The drive controller of claim 1, wherein the switching pattern is reversed during one switching cycle.

3. A drive controller according to any preceding claim, wherein the switching pattern defines an allocation of zero vectors and/or a number of zero vectors.

4. The drive controller according to one of the preceding claims, comprising a calculation unit for calculating a zero vector for each operating state of the three-phase alternating current motor and for storing the zero vector.

5. The drive controller of claim 4, wherein the operating state has a determined rotational speed and a determined torque.

6. A drive controller according to claim 4 or 5, wherein the calculation unit is arranged for calculating the zero vector offline.

7. A drive controller according to any of claims 4 to 6, wherein the calculation unit is arranged to store the zero vector in a look-up table.

8. The drive controller according to one of claims 4 to 7, wherein the calculation unit is arranged for calculating the zero vector based on an optimization algorithm, wherein the optimization algorithm is adapted to reduce the losses of the three-phase alternating current machine over the entire operating range.

9. The drive controller of claim 8, wherein the optimization algorithm is adapted to reduce losses of a three-phase alternating current motor on the motor side or on the intermediate circuit side.

10. Three-phase alternating current machine, in particular for a motor vehicle, comprising a drive controller according to one of the preceding claims.

Technical Field

The present invention relates to a drive controller for a three-phase ac motor. The invention further relates to a three-phase alternating current machine, in particular for a motor vehicle, comprising such a drive controller.

Background

In the field of three-phase alternating current machines, drives are used which are responsible for the existence of a defined direction of the magnetic flux density distribution in the three-phase alternating current machine. Pulse width modulation of the input signal is usually used here. In order to be able to commutate a three-phase ac machine (also referred to as an ac motor) continuously (sinusoidally), voltage space vector modulation is carried out, in particular, in an inverter. Such an inverter may have a half bridge for each of the three phases of a three-phase alternating current motor. The output voltages of the three phases are thereby brought not only to the positive intermediate circuit potential but also to the negative intermediate circuit potential. The intermediate circuit is the transition from the input voltage source to the inverter.

Each half-bridge may assume two different switch positions. Since three half-bridges are necessary for a three-phase ac system, 2 results therefrom³One possible switch position and thus 8 switch states. Each active switch position corresponds to a further voltage condition between the phase and thus a further voltage space vector. The voltage space vector defines the magnetic flux density distribution in the electric machine by means of two variables, namely the angle of the voltage space vector and its value. The two switch positions, in which either all three upper switches are closed or all three lower switches are closed, are referred to as a zero voltage space vector, a zero vector, or a passive voltage space vector.

From these switch positions, six active and two passive voltage space vectors can thus be realized. In order to be able to commutate the three-phase ac motor continuously, these six active basic voltage space vectors are not sufficient, since voltage space vectors with arbitrary angles and values must be connected to the motor. To achieve this, pulse width modulation may be applied. In order to output an arbitrary voltage space vector, two voltage space vectors may be alternately output. The duration of time each voltage space vector is applied is related to the switching frequency of the modulation and the angular position of the voltage space vector. The resulting voltage space vector is defined by the ratio of the two times. This output of the voltage space vector in the three-phase alternating current machine produces an average current and thus a desired orientation of the desired voltage space vector, i.e. the magnetic flux density.

In order to be able to arbitrarily select the amplitude of the output voltage, i.e. the value of the voltage space vector, not only are the two voltage space vectors alternately output, but they are also supplemented by a zero vector. The value of the resulting voltage space vector can be reduced by this zero vector. The magnitude of the induced voltage space vector is related to the ratio of the on-time of the active voltage space vector and the on-time of the zero vector. Thus pulse width modulating three or four participating voltage space vectors (and thus switch positions).

In past systems, the output of an arbitrary voltage space vector was divided into three or four time intervals for each switching cycle. The two active voltage space vectors are output in two of these time intervals, while the zero vector is output in the third or fourth time interval. In the known modulation method, the selection is made as a function of an operating point, wherein one operating point corresponds to a combination comprising two voltage space vectors. This means that for a phase angle pi/3 there is always a certain combination comprising two voltage space vectors and one or two zero vectors. In the case of generating phases for a three-phase alternating current motor, current harmonics also occur in addition to the desired oscillation of the current. This may lead to losses in the entire operating characteristic diagram cluster, which cannot be avoided by the described modulation and control of the three-phase ac motor.

Disclosure of Invention

Against this background, the object of the invention is to improve the drive control of a three-phase ac machine, in which, in particular, the current harmonics should be reduced.

This object is solved by a drive controller for a three-phase alternating current machine, as it is presented hereinafter. The drive controller has an inverter including a plurality of switches for generating a three-phase alternating-current voltage on coils of a three-phase alternating-current motor; and a control device for controlling the switches of the inverter based on pulse width modulation. The inverter may be, in particular, a six-pulse bridge circuit, the three of which are formed by half-bridges with an upper switch and a lower switch, respectively.

In order to improve the actuation of a three-phase ac motor in comparison with known actuators, the control device according to the present drive actuator is provided for controlling the switching in a switching cycle using a switching pattern, wherein the switching pattern is composed of two active voltage space vectors and a plurality of zero vectors, wherein the plurality of zero vectors varies within the switching pattern.

A switching cycle corresponds here to an operating state which is defined by a defined combination of two active voltage space vectors. For each operating state, the rotational speeds and torques of the three-phase ac machine are thus determined, since these are determined by the two active voltage space vectors and the zero vectors. A switching cycle corresponds here to an angle of pi/3 of the three-phase ac signal.

According to the proposed drive controller, a combination is applied comprising two active voltage space vectors and a number of zero vectors, wherein the type and number of said zero vectors is variable within one fundamental period. In contrast, in known systems, only combinations comprising two active voltage space vectors and one or more zero vectors are applied in one fundamental cycle, wherein they do not change in one fundamental cycle. According to the drive controller proposed herein, the plurality of zero vectors may vary within one voltage cycle. A combination comprising two active voltage space vectors and a zero vector can be used, wherein the zero vector varies within the voltage cycle. Alternatively, a combination comprising two active voltage space vectors and a plurality of zero vectors can be applied, wherein these zero vectors likewise vary within the voltage cycle. These two possibilities can also be combined.

By applying multiple and/or different zero vectors in one voltage cycle, the resulting three-phase ac signal can be optimized in terms of its harmonics. During a switching cycle, the values of the voltage space vectors can be adapted by selecting the zero vector accordingly in such a way that these correspond to the actual voltage space vectors, i.e. the voltage space vectors that are realized by simply switching the switches. Since the losses due to harmonics are very small in these cases, the three-phase alternating signal generated in terms of losses and harmonics can be reduced by suitably applying the zero vector.

Since the current harmonics do not provide usable torque, the utilization of the three-phase ac machine is reduced due to the percentage contribution of the harmonics. Furthermore, the harmonics result in an increased thermal load and thus reduce the maximum possible continuous power. This can be improved by the proposed drive controller, since harmonics can be reduced.

According to one embodiment, the switching pattern is reversed during a switching cycle. Reversal in this case means: contains active voltage space vectors and reverses the one or more zero vectors. The switching pattern can be reversed at least once during the switching cycle. Preferably, the reversal occurs in each half of the switching cycle. The signals present at the three-phase ac motor are therefore periodically inverted. Here, it was confirmed that: losses can be reduced in the case of zero vector reversal. The reversal of the zero vector at pi/6 can preferably be achieved, since this leads to an optimized reduction of losses.

According to another embodiment, the switching pattern defines the distribution and/or number of said zero vectors.

By means of the switching pattern, therefore, it is defined: how many zero vectors are applied in a switching cycle and how the zero vectors are distributed. For example, a combination comprising two active voltage space vectors and a first zero vector may be applied first during a switching cycle, while a combination comprising two active voltage space vectors and a second, different zero vector may be applied subsequently during the same switching cycle.

According to another embodiment, the drive controller has a calculation unit for calculating a zero vector for each operating state of the three-phase alternating current machine and for storing the zero vectors.

The calculation unit can already calculate the possible switching states for each operating state in advance, independently of the three-phase ac motor. The operating state has a defined rotational speed and a defined torque, which are defined by the sum of the active voltage space vector and the zero vector. Since the switching state or the zero vector is stored for each operating state, a fast access to this information during the operation of the three-phase alternating current motor is possible without being limited by the calculation.

In particular, the calculation unit may be arranged for calculating the plurality of zero vectors off-line. By off-line calculation, the calculation of the zero vector can also take longer, without this leading to an effect in the operation of the three-phase alternating current machine. Furthermore, the off-line calculation may be implemented already at the factory or before the delivery of the drive controller at once.

In one embodiment, the calculation unit is arranged for storing the one or more zero vectors in a look-up table. The look-up table provides a particularly simple way of storing the zero vector, since no further processing for selecting the zero vector is required here during operation, but rather only the zero vector has to be selected for the respective operating state or switching cycle.

According to a further embodiment, the calculation unit is provided for calculating the one or more zero vectors on the basis of an optimization algorithm, wherein the optimization algorithm is suitable for reducing the losses of the three-phase alternating current machine over the entire operating range.

The choice of the optimization algorithm may furthermore be related to what kind of computing power is available or how fast the algorithm should run. In any case, the optimization is carried out over the entire operating range, i.e. in all operating states, in order to reduce the losses of the three-phase ac machine as a whole. The corresponding algorithm may be selected according to the available computation and time resources. In particular, the optimization algorithm may be adapted to reduce the losses of the three-phase alternating current motor on the motor side or on the intermediate circuit side. The intermediate circuit is the transition from the input voltage source to the inverter.

Different numerical algorithms can be used as optimization algorithms. These include, for example, the following algorithms: "exhaustive search" (extreme search), "complete Parameter Variation" (complete Parameter Variation), "minimum search" (minimum search), or "gradient method".

The optimization algorithm may be the same for the intermediate circuit side as well as the motor side. Voltage fluctuations should naturally be reduced for the intermediate circuit. There may be a target conflict between the optimization on the motor side and the intermediate circuit side. In this case, the motor side or the intermediate circuit side can therefore be optimized.

According to a further aspect, a three-phase alternating current machine, in particular for a motor vehicle, is proposed, which comprises a drive control as described above.

According to another aspect, a method for operating a three-phase alternating current machine is proposed. The method comprises the following steps: generating a three-phase alternating voltage at the coils of a three-phase alternating current motor by means of an inverter having a plurality of switches; and controlling the switching of the inverter on the basis of pulse width modulation, wherein the switching is controlled in one switching cycle using a switching pattern, wherein the switching pattern consists of two active voltage space vectors and a plurality of zero vectors, wherein the plurality of zero vectors vary within the switching pattern.

The embodiments and features described for the proposed device apply correspondingly to the proposed method.

Furthermore, a computer program product is proposed, which has a program code configured to cause a computer to carry out the method described above.

The computer program product, for example the computer program module, may be provided or supplied, for example, as a storage medium, for example a memory card, a USB stick, a CD-ROM, a DVD or in the form of a file downloadable by a server in a network. This may be achieved, for example, by transmitting corresponding files with computer program products or computer program modules in a wireless communication network.

Further possible implementations of the invention also include combinations of features or embodiments not explicitly described above or in the following with regard to the individual embodiments.

Those skilled in the art can also add various aspects as improvements or additions to the corresponding basic form of the invention.

Further advantages and advantageous embodiments are set forth in the description, the drawing and the claims. The combinations of features mentioned here, in particular in the description and in the drawings, are purely exemplary, so that the individual features can also be present individually or in further combinations.

Drawings

The invention shall be further described in the following on the basis of embodiments shown in the drawings. The embodiments and combinations shown in the embodiments are purely exemplary and should not limit the scope of protection of the invention. The scope of the invention is defined only by the appended claims.

The figures show:

FIG. 1 shows a drive controller for a three-phase AC motor;

FIG. 2 shows a graph of a modulation curve according to the modulation phase angle; and

fig. 3 shows a graph of a modulation curve according to a modulation index.

Detailed Description

In the following, elements that are identical or functionally equivalent are denoted by the same reference numerals.

Fig. 1 shows a drive controller 1 for a three-phase ac machine 2, the three-phase ac machine 2 here ideally being formed by three windings L1 to L3 and a voltage e induced in the opposite direction_aTo e_cIt represents the three coils of the three-phase alternating current motor 2.

In order to obtain a defined direction of the magnetic flux density distribution in the three-phase alternating current motor 2, a pulse width modulation of the input signal is applied in the inverter 3, the input signal originating from the input voltage source 5. In particular voltage space vector modulation.

The inverter 3 has a half bridge for each of three phases 6 of the three-phase ac motor 2. The first half-bridge is formed by switches S1, S2, the second half-bridge is formed by switches S3, S4, and the third half-bridge is formed by switches S5, S6. The output voltages of the three phases 6 can thus be brought both to the positive intermediate circuit potential and to the negative intermediate circuit potential. The intermediate circuit is the transition from the input voltage source 5 to the inverter 3.

Each half-bridge of the inverter 3 may assume two different switching positions. Since three half-bridges are necessary for a three-phase ac system, 2 results therefrom³One possible switch position and thus 8 switch states. Each active switch position corresponds to a further voltage situation between the respective phase 6 and therefore a further voltage space vector. The voltage space vector defines the magnetic flux density distribution in the three-phase alternating current machine 2 by two variables, namely the angle of the voltage space vector and its value.

For driving the inverter 3 and its switches S1 to S6, a control device 4 is provided. In order to improve the actuation of the three-phase alternating current motor 2 in comparison with known actuation, the control device 4 is provided for controlling the switches S1 to S6 within one switching cycle using a certain predefined switching pattern. The switching pattern is composed of two active voltage space vectors and a plurality of zero vectors, wherein the plurality of zero vectors vary within the switching pattern. In order to optimize the generated alternating point signal, in particular to reduce current harmonics, since these harmonics cause distortions in the signal, the applied switching pattern can be optimized using a zero vector. Different suitable optimization algorithms can be applied for this purpose.

Fig. 2 and 3 show modulation curves for different modulation methods. Fig. 2 shows the change of the angle θ of the signal in relation to the Harmonic Distortion Factor (HDF), while fig. 3 shows the modulation index M in relation to the Harmonic Distortion Factor (HDF)_i. Modulation index M_iThis is understood to mean a standardized inverter output voltage (inverter regulation).

Fig. 2 and 3 show, on the one hand, modulation profiles for discrete modulation methods. These include methods DPWMMIN (discontinuous minimum pulse width modulation), DPWMMAX (discontinuous maximum pulse width modulation), DPWM1 (discontinuous pulse width modulation) and DPWM3 (discontinuous 30 ° pulse width modulation), each applying a zero vector. Furthermore, a modulation profile for a continuous modulation method is shown. These include the modulation methods SVPWM (space vector pulse width modulation) and THIPWM1/4 (third harmonic PWM), which apply two zero vectors. The modulation method, as applied by the control device described in fig. 1, is indicated in fig. 2 and 3 as OZP. The number of zero vectors varies within a switching cycle depending on the regulation, the angle and the frequency.

Curves C1 and K5 relate to SWPWM modulation. Curves C2 and K4 relate to THIPWM1/4 modulation. Curves C3/C4 and K2 relate to DPWMMIN/DPWMMAX modulation. Curve K3 relates to DPWM3 modulation. Curve K1 relates to DPWM1 modulation.

As can be seen from fig. 2 and 3, the reduction of the distortion factor is achieved by modulation (OZP), as it is done by the drive controller 1 of fig. 1. This is illustrated by curve C5 in fig. 2 and curve K6 in fig. 3. As shown in the figure, the curve C5 or K6 is optimized by a corresponding optimization algorithm which can be used to calculate the zero vector in such a way that the distortion factor HDF is minimal compared to the existing modulation methods.

By applying multiple and/or different zero vectors in one voltage cycle, as set forth herein, the resulting three-phase ac signal can be optimized with respect to harmonics of the three-phase ac signal. In this way, distortion of the output signal can be reduced.

List of reference numerals

1 drive controller

2 three-phase AC motor

3 inverter

4 control device

5 input voltage source

6 output phase

Modulation curve of C1-C4 according to phase angle

e_a-e_cVoltage of reverse induction

Modulation curves of K1-K6 according to modulation index

L1-L3 coil

S1-S6 switch