DE102011088244A1 - Method for operating e.g. permanent magnet synchronous motor at inverter of e.g. electrical powertrain of motor car, involves setting pulse-width modulation default values to provide corrected values of phases for adjusting voltage vector - Google Patents

Abstract

The method involves determining pulse-width modulation (PWM) default values for phases (U-W) to set a voltage vector at an induction machine (4) via power switches (S1-S6) of an inverter (1) to operate the induction machine. A phase current value per phase is simulated corresponding to a respective switching period to compensate a potential shift of the switches and return diodes (D1-D6). A PWM default error value of the phase is determined depending on the current values. The PWM default values are set to provide corrected PWM default values of the phases for adjusting the voltage vector. The power switches are designed as high- and low-side power switches such as MOSFETs or insulated-gate bipolar transistors (IGBT). Independent claims are also included for the following: (1) a device for operating an induction machine (2) a propulsion system.

Description

The present invention relates to a method for operating a rotating field machine according to the preamble of claim 1.

In an inverter, in particular a voltage source inverter, by a PWM modulation method, the desired voltages for a to be operated by means of the inverter induction machine, for. As a permanent-magnet synchronous machine (PMSM) can be set by means of generated PWM default values. The generated PWM default values from the controller or controller to produce a particular voltage vector will vary depending on the desired voltage frequency and amplitude.

As a semiconductor or current valves in the inverter MOSFETs, IGBTs, thyristors, GTOs, etc. are usually used.

In these switch semiconductors in the inverter and the associated freewheeling or flyback diodes arise voltage drops, resulting from the current flowing through and from the forward voltage in these flow control valves. These voltage drops cause potential shifts in the inverter, which leads to the falsification of the intended voltage vector in the induction machine and thus to voltage distortions.

In order to compensate for these potential shifts in the inverter, it is known for controlled drive systems to measure the phase currents in order to be able to build up a feedback, whereby an accurate determination of the zero crossing is considerable.

In the context of drive systems which are like that according to 3 From a control structure for field-oriented control of the induction machine, in particular with adjustable dynamics, make use of or generally provide no measurement of the machine currents, a compensation of the potential shift can not be done in this way.

Proceeding from this, the present invention has the object to provide an alternative method for operating a rotating field machine, which advantageously allows easy compensation of the potential shifts in the inverter, in particular without measuring the machine currents.

This object is achieved by the features of claim 1. Advantageous embodiments and further developments are the subject of the dependent claims.

The invention proposes a method for operating a rotary field machine, in particular a permanent-magnet synchronous machine (PMSM) or an asynchronous machine, to an inverter, in particular a voltage source inverter. Such has a voltage intermediate circuit on the network side, which is preferably formed by means of a DC link capacitor. Furthermore, the inverter has power switch, z. As MOSFETs or IGBTs, which are arranged in half-bridges of an inverter bridge circuit as a high-side power switch or low-side power switch. The circuit breakers here freewheeling or flyback diodes are assigned, in particular depending on a freewheeling or flyback diode. Preferably, the inverter is formed by means of a B6 bridge circuit, which can be controlled by a driver stage, in particular of the inverter.

For operation of the induction machine - which in the context of the present invention, in particular a stator and a rotor - on the inverter, is provided on the induction machine voltage vector by means of the inverter by suitable switching positions of the circuit breaker of the same, in particular one voltage vector - preferably a space vector modulation Voltage vector - during each one switching period or PWM period. For this purpose, in the context of the method according to the invention PWM default values are determined for each phase, z. B. calculated. The PWM default values express duty cycles for selected switches of the half-bridges, i.e.. per phase, and are provided for the inverter or its driver stage.

The inverter is generally operable by means of PWM default values for the respective PWM periods which already implement the potential shift compensation, e.g. B. in the context of PWM default values, which are generated by a regulation with current measurement.

Furthermore, the inverter and in this respect an induction machine within the scope of the present invention by means of PWM default values for the respective PWM periods can be operated, which - as largely idealized PWM default values, z. B. provided in the context of a field-oriented control - still require a correction to compensate for the potential shift and such can be provided below as corrected PWM default values for the inverter. This will be explained in more detail below.

According to the invention - in order to compensate for a potential shift on the circuit breakers of the inverter and the flyback diodes - corresponding to a respective switching period, a phase current value per phase simulated, depending on the reproduced phase current value of the phase, a PWM default value error of the phase determined and the PWM Phase of the phase for providing a corrected PWM default value of the phase for adjusting the voltage vector is related.

In the method according to the invention, the PWM standard value error per phase is preferably determined based on a phase current value of the phase simulated by means of desired current specifications or current setpoints, in particular by means of filtering of nominal current specifications. By utilization by means of nominal current presets or current setpoints of simulated phase currents, i. phase current values mimicking those actual phase current values on / in the induction machine, i. in terms of magnitude and sign, in particular with regard to their time course, and which can be obtained in the context of the present invention, in particular as a result of filtering the target current specifications, can advantageously account for a current measurement of the phase currents of the induction machine to compensate for the potential shift. This is extremely advantageous, in particular for field-oriented control.

In the context of the present invention, it is provided that a simulated phase current value is always provided by means of filtering the nominal current specifications with a low-pass filter, in particular a digital filter. In this case, the setpoint current specifications are provided, in particular, as discrete-time variables, for the filtering of which the low-pass filter is preferably suitable in the context of the present invention. The low-pass filter is designed, in particular, to act on the setpoint current specifications with a time delay, insofar preferably acts as a time-discrete PT1 element. The low-pass filter can be formed in a simple manner computerized.

By means of the low-pass filter, the dynamics of a field-oriented control or regulation, in particular a field-oriented control with adjustable dynamics by any suitable choice or adjustment of the time constant of the low-pass filter can be emulated.

The setpoint current specifications for filtering are preferably provided in a d, q two-size system, in particular as time-discrete variables. As a result, an unobtrusive further processing is possible. After filtering, the now-filtered target current specifications can be transformed into a three-digit system for providing the simulated phase current values per phase. It is envisaged here that the PWM default values per phase are determined on the basis of the setpoint current specifications or current setpoint values.

Provided within the scope of the present invention, it is preferred that the induction machine be operated in a controlled manner during the process according to a field-oriented control (FOS), in particular with adjustable dynamics. The time constant of a filter can be selected corresponding to the dynamics, in particular depending on the set dynamics. In addition, the use of the method is also conceivable in controller structures which do not make use of a current measurement.

In the context of the method according to the invention, it is provided that a simulated phase current value for determining the PWM standard value error of the phase is in each case compared with a threshold value, in particular in order to determine whether the respective simulated phase current value is positive or greater than zero or negative or not positive, ie less than zero. The PWM default value error per phase can hereafter be determined as a function of the comparison result, in particular depending on the sign and magnitude.

Furthermore, it is provided in the context of the method according to the invention, for the determination of the PWM default value error per phase, voltage drops of the phase, i. determining a circuit breaker voltage drop and a diode voltage drop based on the replicated phase current value of the phase. The determined voltage drops of the phase are in this case in particular voltage drops at the current-carrying components, ie. each of a circuit breaker and each of the return diode of the complementary circuit breaker of the phase.

In particular, as a function of the PWM comparison result and the determined voltage drops, the default value error per phase can now be determined, for which purpose in the context of the present invention, in particular following equations 1) and 2) can be used.

ermittelt werden, falls durch den Schwellwertvergleich bestimmt ist, dass der nachgebildete Phasenstromwert der Phase positiv ist, oder gemäß der Gleichung 2)

ermittelt werden, falls durch den Schwellwertvergleich bestimmt ist, dass der nachgebildete Phasenstromwert der Phase nicht positiv, alternativ z.B. negativ, ist. In den Gleichungen 1) und 2) bezeichnet ΔPWM_potF1,2,3 den ermittelten PWM-Vorgabewertfehler je Phase, PWM_potF1,2,3 den PWM-Vorgabewert je Phase, U_T1,2,3 den Leistungsschalter-Spannungsabfall je Phase, U_D1,2,3 den Dioden-Spannungsabfall je Phase und U_dc die Zwischenkreisspannung, i.e. des Wechselrichters. The PWM default value error per phase can be calculated according to equation 1)

if it is determined by the threshold comparison that the replicated phase current value of the phase is positive, or according to equation 2)

are determined, if it is determined by the threshold comparison, that the replicated phase current value of the phase is not positive, alternatively, for example negative. In Equations 1) and 2), ΔPWM potF1,2,3 _designates the determined PWM default value _error per phase, PWM _potF1,2,3 the PWM default value per phase, U _T1,2,3 the circuit breaker voltage drop per phase, U _D1,2,3 the diode voltage drop per phase and U _dc the _{DC link} voltage, ie the inverter.

Once the respective PWM default value error has been determined, the latter can be related, in particular added, to the corresponding PWM default value for this phase in order to determine the corresponding corrected PWM default value, by means of which the compensation of the potential shift is implemented. Subsequently, the correspondingly corrected PWM default value can be output for setting the distortion-free voltage vector for the further operation of the induction machine, in particular for iterative application of the method one corrected PWM default value per phase for all voltage vectors to be set.

In order to avoid that a corrected PWM default value, which was less than zero percent or greater than one hundred percent, was determined, i.e. assumes a value that can not be displayed within a PWM period to which the inverter is output, this can be limited to zero percent or one hundred percent before output to the inverter.

The method can be carried out by means of a device which is designed to carry out the method, in particular includes an inverter, and provides the corrected default values for operating the inverter. Such a device can be formed largely computerized, z. B. by means of at least one μControllers or processor, in particular as a control unit. Depending on the corrected PWM default values, the inverter can drive a rotating field machine connected to this power side, which is preferably part of a drive system that can be formed by means of the device.

The device preferably has a control structure for field-oriented control, in particular for field-oriented control with adjustable dynamics, wherein the device provides corrected PWM default values in the course of the field-oriented control. It is also conceivable to implement the control structure in a controller structure for field-oriented control, which is optionally switchable to the control structure.

It is envisaged in each case that the device has a filter as described above or its functionality for filtering the setpoint current specifications or for simulating the phase currents. The time constant of the filter is preferably set to model the dynamics of the controller.

It is also proposed a drive system with a rotating field machine and an inverter, wherein the drive system is designed for operation of the induction machine according to the method described above.

The method, which allows the operation of the induction machine without phase current sensor, is advantageously applicable especially at high speeds. The method can be carried out computerized, in particular continuously, z. B. by means of a microcontroller, for. B. a controller or a Control of a device according to the invention, in particular, for example, the same control or regulation, which also calculates the PWM default values.

The proposed method, the device or the drive system are preferably used in a motor vehicle, in particular in a drive train of the motor vehicle. The hereby operated rotary field machine is preferably used for actuating an actuator of the drive train, d. H. for carrying out an actuating function of the drive train, for example for performing gearshifts in a multi-gear vehicle transmission, for coupling / uncoupling drive shafts, for carrying out a starting operation of an internal combustion engine etc. Also preferably, the induction machine serves as a traction drive (drive motor) in the vehicle drive train, d. H. for generating a drive torque for propulsion of the motor vehicle. In the latter case, the motor vehicle is in particular an electric vehicle or an electric motor hybrid vehicle hybrid. However, the induction machine can also be used preferably for another actuator of the motor vehicle. In particular, the induction machine can be used in a vehicle steering system for electromotive steering power assistance (electric power steering) or for adjusting a suspension component, such as an electrically adjustable Fahrzeugfahrwerksstabilisators or vehicle suspension arm. However, the proposed method, the device or the drive system are not limited thereto. Thus, for example, the control of an induction machine of an elevator drive, a cable car drive, a machine tool drive or adjustment system or a wind turbine control system can be done.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 an example of a voltage source inverter with an operable by this rotary field machine;

2 an example of an equivalent circuit diagram for the arrangement according to 1 ;

3 exemplarily a drive system with a control structure according to the prior art;

4 exemplary and schematically a drive system with an apparatus for carrying out the method according to a possible embodiment of the present invention; and

5 exemplary and schematically a flowchart for providing the corrected and limited PWM default values according to the method for operating a rotating field machine according to a possible embodiment of the invention.

In the following description of the figures, the same elements or functions are provided with the same reference numerals. Corresponding elements or functions in the prior art are provided with primed reference numerals.

1 shows an example and schematically a pulse inverter 1 with a voltage intermediate circuit 2 , which by means of an intermediate circuit capacitor 3 is formed. The inverter 1 is formed in B6 bridge circuit with three half-bridges, each having two power switches S1, S2 and S3, S4, and S5, S6 in the form of MOSFETs. Three circuit breakers S1, S3, S5 of the inverter 1 are arranged as a high-side circuit breaker, three switches S2, S4, S6 as a low-side circuit breaker. Each switch S1 ... S6 is associated with a flyback or freewheeling diode D1 ... D6. The center taps of the half bridges are each with a phase U or V or W of a rotary field machine 4 in the form of a permanent magnet synchronous machine (PMSM) electrically connected. The induction machine 4 , which is intended for use in a motor vehicle, for. B. in a hybridized or electric drive train, alternatively z. As for a power steering, has a stator with a stator winding, in particular with the three winding strands U, V, W, which are preferably symmetrically wound and arranged offset by 120 degrees, and further in particular a rotor equipped with permanent magnets.

By means of the switches S1 ... S6 can via a driver stage, not shown, of the inverter 1 the usual in a space vector modulation voltage vectors on the induction machine 4 be set over the eight possible switching states of the circuit breaker S1 to S6 of the inverter 1 ,

A turn-on state of a half-bridge for a phase U, V, W can generally be controlled via a PWM default value corresponding to a duty cycle per PWM period. 2 In this case, an equivalent circuit diagram is illustrated in which two switches S1, S2 or S3, S4 or S5, S6 each have a half-bridge as a changeover switch S _U , S _V , S _W corresponding to the functionality of the inverter 1 are shown. Depending on a respective PWM default value for one of the phases U, V, W, each switch S _U , S _V , S _W between high-side and low-side potential for a certain duration per PWM period from -1 to +1 are switched (or vice versa), wherein the high-side potential is illustrated by the switch position +1, low-side potential by the position -1.

With a default PWM value of 100%, a switch S _U or S _V or S _{W should be} in position +1 for the entire duration of a PWM period, ie the induction machine 4 about the associated phase U or V bwz. W be connected to the high-side potential. For a PWM default value of 0%, the switch S _U , S _V , S _{W should be} in the -1 position for the entire PWM period, ie the induction machine 4 be connected via the associated phase with the low-side potential. A PWM default value between zero and 100% indicates insofar a corresponding duty cycle corresponding to the ratio of the duration of the state +1 to the period.

The inventive method can with a device 5 as well as a drive system 6 especially depending on 4 be performed. Visible here are compared to the prior art, sz B. 3 , advantageously only minor modifications required.

Preferred embodiments of the invention are described below with reference to 4 and 5 explained in more detail.

4 shows a control structure 7 , which by means of a device 5 of the drive system 6 is implemented. The device 5 or the drive system 6 point to the formation of the tax structure 7 suitable functional units, which are formed in particular by means of at least one μControllers, in particular integrated or alternatively z. B. separated from each other, which will be explained in more detail below. In addition, have device 5 or drive system 6 an inverter as described above 1 on, the drive system 6 furthermore a rotary field machine as described above 4 ,

The tax structure 7 the device 5 or the drive system 6 includes a functional unit 8th at the entrance nine Current setpoint values or setpoint current specifications I _sdRef , I _sqRef , which are provided in the d, q two-variable system as time-discrete variables. The functional unit 8th has another entrance 10 on, as an additional input variable, the actual electrical angular velocity ω _{el of} the rotor of the induction machine 4 is made available. The electrical angular velocity ω _el is based on the determined mechanical angle θ _mech z. B. by considering the temporal change of

i.e. basierend auf der Winkelinformation eines Positionsgebers 11, z. B. eines Inkrementalgebers oder eines Resolvers, als auch in Abhängigkeit der Polpaarzahl Zp auf bekannte Weise ermittelt, wozu eine entsprechend ausgebildete Funktionseinheit 12 vorgesehen ist. Der Eingang 10 ist z. B. mit einem Ausgang der zweiten Funktionseinheit 12 verbunden, z. B. mittels einer elektrischen Verbindungsleitung 13. mechanical angle θ _mech accordingly

ie based on the angle information of a position sensor 11 , z. B. an incremental encoder or a resolver, as well as in dependence on the number of pole pairs Zp determined in a known manner, including a suitably trained functional unit 12 is provided. The entrance 10 is z. B. with an output of the second functional unit 12 connected, z. B. by means of an electrical connection line 13 ,

The functional unit 8th is intended, in particular taking into account the actual, determined electrical angular velocity ω _{el of} the rotor and the desired current specifications I _sdRef , I _{sqRef setpoint} voltage _components , ie a (stator) longitudinal voltage component or d-voltage component and a (stator) transverse voltage component or q- Determine the voltage component in the d, q-two-size system by means of respective FOS algorithms and provide them. The d, q two-size system denotes a coordinate system which rotates in a known manner with the rotor.

und Gleichung B) für die (Stator-)Sollquerspannungskomponente

As FOS algorithms, which z. B. in a permanent memory of the functional unit 8th are deposited or z. B. are loaded as needed in a volatile memory on which the functional unit 8th equations A) and B) can be used, which are solved in the respective current or to be performed sampling step, ie equation A) for the (stator) Solllängsspannungskomponente:

and equation B) for the (stator) desired lateral stress component

In the equations A) and B), the indexing _{_k} denotes the magnitudes of the current and _{_k-1} the magnitudes of the preceding scanning step of the duration T and _s the stator reference, ie a quantity relating to the stator of the induction machine 4 , U _{sd_k} or U _{sd_k-1} denote the desired longitudinal stress component, U _{sq_k} and U _{sq_k-1} , respectively, the desired transverse stress component, ie, respective specifications for z. B. further functional units of the drive system 6 or for controlling the induction machine 4 ,

T _Ed denotes a time constant resulting from L _sd / R and L _sd the longitudinal component of the inductance of the stator winding, T _Eq a time constant resulting from L _sq / R and L _sq the _{transverse component of} the inductance of the stator winding, I _{sdRef_k} or I _{sdRef_k-1 is} the nominal longitudinal current specification, I _{sq.ref_k} or I _{sq.ref_k-1 is} the set cross current specification, R is the ohmic winding resistance of the stator winding, ω _{el is} the electrical angular velocity, and Ψω _{el is} the pole rotor or rotor voltage assumed to be constant for a particularly very short or short sampling step duration T, where Ψ represents the pole wheel flux. The pole wheel is z. B. determined by means of stored characteristics.

The winding resistance R is z. B. deposited or in individual cases according to the respective induction machine 4 predetermined, z. B. also in a memory for the functional unit 8th deposited. The Polradspannung Ψω _el is assumed to be constant, since normally the mechanical time constant of the induction machine 4 is greater than the electrical time constant. The speed can be considered constant during the rapid change of the current.

The d, q current setpoints I _{sdRef_k-1} and I _{sqRef_k-1 of} the respective preceding sampling step required to solve the equations A) and B) in a current sampling step _{_k} are e.g. B. also in a memory for the functional unit 8th deposited. The deposit and access to the stored values are in particular by the functional unit 8th causes. The memory is z. B. a volatile or a RAM memory.

Using the FOS algorithms according to Equations A) and B), the field-oriented control (FOS) dynamics determined by the control structure 7 can be realized or made possible to be set optionally on the time constants T ₁ and T ₂ , ie by transmission elements. The time constants T _Ed and T _{Eq of} the (control) path are compensated here.

The determined _desired voltage _components U _{sd_k} , U _{sq_k} are at the output 14 the functional unit 8th provided, cf. 4 ,

The functional unit 8th in signal flow direction to the inverter 1 subordinate has the tax structure 7 furthermore a functional unit 15 which is intended to that of the functional unit 8th provided d, q-set voltage _components U _{sd_k} , U _{sq_k} in particular by means of an inverse Park and Clarke transformation, in target voltage values U _s1 , U _s2 , U _s3 a multi-phase three-phase system, in particular a three-phase three-phase system to convert, z. B. also within the current sampling step.

The functional unit 15 has an entrance 16 on, which with the exit 14 the functional unit 8th is in communication, for. B. via electrical connection lines. The functional unit 8th downstream functional unit 15 is designed in particular as a signal converter or as a transformation unit.

In order to determine the setpoint voltage values U _s1 , U _s2 , U _s3 in the multi-variable three-phase system, the functional unit is used 15 Also provided an angle information available, ie the actual electrical angle θ _{el of} the rotor resulting from the mechanical angle as a function of the number of pole pairs Z _p communicated. This size comes from another functional unit 17 , alternatively z. B. from the functional unit 12 , z. B. based on the angle information of the position sensor 11 ascertained in a known manner and z. B. via another input 18 the functional unit 15 provided with an output of the functional unit 17 communicates.

Based on that of the functional unit 15 at an exit 19 output nominal voltages U _s1 , U _s2 , U _s3 are then PWM default values PWM1, PWM2, PWM3 generated, which correspond to values with which the induction machine 4 would be operable in an idealized operating case, ie idealized values that the potential shift at the circuit breakers S1 ... S6 in contrast to the z. B. generated in the course of a control PWM default values PWM1, PWM2, PWM3, however, do not take into account.

The conversion of the nominal voltage values U _s1 , U _s2 , U _s3 to PWM default values PWM1, PWM2, PWM3 is performed by a functional unit in the form of the PWM generator 20 the tax structure 7 , which is formed as a vector modulator or space vector pulse width modulator and which also has the DC voltage U _{dc of} the intermediate _circuit of the inverter 1 is supplied as a further input variable, ie to an input 21 , The nominal voltage values U _s1 , U _s2 , U _s3 are present at an input 22 the functional unit 20 On, the PWM default values PWM1, PWM2, PWM3 are at an output 23 to disposal.

With the exit 23 the functional unit 20 connected is the entrance 24 a functional unit 25 the tax structure 7 , which is provided for compensation of the inverter-side potential shift and based on the PWM default values PWM1, PWM2, PWM3 generates corrected PWM default values PWM1n, PWM2n, PWM3n for each phase U, V, W, by means of which the potential shift is compensated. The corrected and possibly limited default values PWM1n, PWM2n, PWM3n, which respectively express duty cycles, are output 26 for controlling the inverter 1 provided, based on which the induction machine 4 operates suitably, ie adjusts the intended voltage vector via its power switches S1 to S6.

In order to be able to provide the corrected PWM default values PWM1n, PWM2n, PWM3n appropriately, the control structure has 7 a filter 27 on, in particular a digital filter, which is designed to apply the time-discrete target current specifications I _sdRef , I _sqRef in the course of filtering with a delay or to filter them. For this purpose, the filter acts as a low-pass filter, in particular as a PT1 element. The filter 27 are the set current specifications I _sdRef , I _sqRef , which at the input nine the functional unit 8th be tapped, at an entrance 28 provided.

The filter 27 has a time constant which is suitable, a respective dynamics of the controller or the device 5 or the drive system 6 reproduce, the time constant is set in particular according to the nachzubildenden dynamics. This makes it possible to _generate phase _{current values} I _s1Ref , I _s2Ref , I _s3Ref per phase U, V, W based on the setpoint current specifications I _sdRef , I _sqRef , which with regard to their magnitude and their sign reflect the actual machine currents or values per phase U, V, W correspond.

The filtered nominal current specifications I _sdRefF , I _sqRefF are at one output 29 provided as sizes in the d, q two-size system. To provide the phase _{currents of} simulated phase _{current values} I _s1Ref , I _s2Ref , I _s3Ref , ie a phase _{current value} I _s1Ref , I _s2Ref , I _s3Ref per phase U, V, W, these are subsequently transformed back into the three-series system. For this purpose, the tax structure 7 a functional unit 30 as it were the functional unit 15 for transformation on, at the entrance 31 the filtered nominal current specifications I _sdRefF , I _{sqRefF are} applied and which angle information required for the transformation, ie the electrical angle θ _el , via another, with an output 32 the transformation unit 15 connected input 33 receives.

At an exit 34 the functional unit 30 After transformation, the simulated phase _{current value} I _s1Ref , I _s2Ref , I _s3Ref per phase U, V, W is now provided, which at a further input 35 the functional unit 25 for determining the corrected PWM default values PWM1n, PWM2n, PWM3n.

Corresponding to a respective switching period of the inverter 1 determines the functional unit 25 for compensation of the potential shift based on the phase _{current values} I _s1Ref , I _s2Ref , I _{s3Ref mimicked} by means of the setpoint _{current specifications} I _sRef , I _sqRef , a default value error _{ΔPWM potF1,2,3} per phase U, V, W by sign and magnitude to relate this to the respective default value PWM1, PWM2, PWM3 of the phase U, V, W for providing or respectively determining a respective corrected default value PWM1n, PWM2n, PWM3n W, which is hereafter in particular by means of 5 is explained in more detail.

To determine the respective default value error ΔPWM _potF1 or ΔPWM _potF2 or ΔPWM _potF3 is determined by the functional unit 25 for each phase U, V, W, first a threshold value comparison performed, reference numerals 36 in which it is determined whether a simulated phase _{current value} I _s1Ref , I _s2Ref , I _{s3Ref is} always positive, reference _numeral 37 , or negative or less than zero, reference numerals 38 , is.

Furthermore, by the functional unit 25 _Based on the simulated phase _{current value} I _s1Ref , I _s2Ref , I _s3Ref the phase per phase U, V, W a circuit breaker voltage drop and a diode voltage drop determined, reference numerals 39 , For this purpose, by the functional unit 25 the equation 3): U _T1,2,3 = U _T0 + I _s1,2,3ref R _T1,2,3 for the voltage drop in the semiconductor S1 ... S6 per phase U, V, W and the equation 4): U _D1,2,3 = U _D0 + I _s1,2,3ref R _D1,2,3 for the voltage drop in the diode D1 ... D6 be solved. In equations 3) and 4), U _T0 here furthermore designates the forward _{voltage in} the _{power switch} S1... S6 in the respective phase U, V, W, I _{s1, 2, 3ref} the respective simulated phase _{current value} I _s1Ref or I _s2Ref or I _s3Ref the phase U, V, W, R _T1,2,3 the on- _resistance in the circuit breaker S1 ... S6 and R _D1,2,3 the on- _{resistance of} the diode D1 ... D6 the phase U, V, W (the Diode of the complementary circuit breaker).

Depending on the comparison result, reference number 37 . 38 , as well as the determined voltage drops, reference numerals 39 , determines the functional unit 25 now the PWM default value error ΔPWM _potF1,2,3 per phase U, V, W. In the event that the comparison result shows that a simulated phase _{current value} I _s1,2,3ref the phase U, V, W is positive, reference numeral 37 , for the PWM default value error ΔPWM _{potF1,2,3 of} the phase U, V, W, equation 5) is solved per phase U, V, W:

Returns the threshold comparison, reference number 36 in that a simulated phase _{current value} I _{s1,2,3ref of} the phase U, V, W is negative or not positive, reference numerals 38 , for the PWM default value error ΔPWM _{potF1,2,3 of} the phase U, V, W, equation 6) is solved per phase U, V, W:

In equations 5) and 6), ΔPWM potF1,2,3 _denotes the determined PWM standard value _error per phase (U, V, W), PWM _1,2,3 the PWM default value PWM1, PWM2, PWM3 per phase U, V, W, U _T1,2,3 the circuit breaker voltage drop per phase U, V, W, U _D1,2,3 the diode voltage drop per phase U, V, W and U _dc the _{DC link} voltage at the inverter 1 , This becomes the functional unit 25 at another entrance 40 made available.

By subsequently adding, reference number 41 , a respectively determined with respect to its magnitude and sign PWM default value error ΔPWM _potF1,2,3 per phase with the corresponding PWM default value PWM1 or PWM2 or PWM3 is now for each phase U, V, W a new or corrected PWM default value PWM1n or PWM2n or PWM3n determines which to output to the inverter 1 can be output or provided for setting a voltage vector taking into account the potential shift, ie at the output 26 , The corrected PWM default values PWM1n or PWM2n or PWM3n are given below PWM1n = PWM1 + ΔPWM _potF1 , PWM2n = PWM2 + ΔPWM _potF2 , and PWM3n = PWM3 + ΔPWM _potF3 .

A corrected PWM default value PWM1n, PWM2n, PWM3n, which is less than zero percent or greater than one hundred percent, is thereby output to the inverter 1 to zero percent or one hundred percent through the functional unit 25 limited, reference numerals 42 ,

It should be noted that the induction machine 4 is operated controlled during the described method according to a field-oriented control, in particular with adjustable dynamics.

In the context of the present invention, a compensation of the potential shift without the use of current sensors is made possible, together with a reduced cost for sensors, A / D converters, board surface, e.g. for use in power steering systems. By compensating for the potential shift, on the one hand, better acoustics are guaranteed - insofar as harmonics are damped in the current - and, on the other hand, the voltage can be better utilized. The method can be used in traction drives with inaccurate current measurement in the large current range and in particular large speed range. Of course, further applications are conceivable.

LIST OF REFERENCE NUMBERS

1, 1 '

inverter

2

DC

3

Link capacitor

4, 4 '

Induction machine

5, 5 '

contraption

6, 6 '

drive system

7, 7 '

tax structure

8, 8 '

functional unit

9, 9 '

entrance 8th

10, 10 '

another entrance 8th

11, 11 '

position sensor

12, 12 '

functional unit

13, 13 '

connecting line

14, 14 '

output 8th

15, 15 '

functional unit

16, 16 '

entrance 15

17, 17 '

functional unit

18, 18 '

entrance 15

19, 19 '

output 15

20, 20 '

functional unit

21, 21 '

entrance 20

22, 22 '

another entrance 20

23, 23 '

output 20

24

entrance 25

25

functional unit

26

output 25

27

filter

28

entrance 27

29

output 27

30

functional unit

31

entrance 30

32

another exit 15

33

another entrance 30

34

output 30

35

another entrance 25

36

thresholding

37

comparison result

38

comparison result

39

Determination of voltage drops

40

another entrance 25

41

Determination of corrected PWM default values

42

limit

S1 ... S6

 breakers

D1 ... D6

 Freewheeling diode

AND MANY MORE

phases

Claims (16)

Method for operating a rotating field machine ( 4 ), in particular a permanent-magnet synchronous machine (PMSM) or an asynchronous machine, to an inverter ( 1 ), wherein the operation of the induction machine ( 4 ) PWM default values per phase (U, V, W) of the same are determined for the setting of a voltage vector at the induction machine ( 4 ) via the circuit breaker (S1, ... S6) of the inverter ( 1 ), characterized in that corresponding to a respective switching period for compensating the potential shift at the power switches (S1, ... S6) of the inverter ( 1 ) and their flyback _diodes (D1 ... D6) a phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) is _{simulated for} each phase (U, V, W), wherein depending on the simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) determines a PWM default value error (ΔPWM _potF1,2,3 ) of the phase (U, V, W) and with the PWM default value (PWM1, PWM2, PWM3) of the phase (U, V, W) to provide a corrected PWM Bias value (PWM1n, PWM2n, PWM3n) is related to the phase (U, V, W) for adjusting the voltage vector. Method according to Claim 1, characterized in that a simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) for determining the PWM standard value error (ΔPWM _potF1,2,3 ) of the phase (U, V, W) is each compared with a threshold value is determined, wherein the PWM default value error (ΔPWM _potF1,2,3 ) is determined as a function of the comparison result, in particular depending on the sign and magnitude. Method according to one of the preceding claims, characterized in that for determining the PWM standard value error (ΔPWM _potF1,2,3 ) per phase (U, V, W) voltage _{drops of} the phase (U, V, W) on the replicated phase current _value (I _s1Ref , I _s2Ref , I _s3Ref ) of the phase (U, V, W). A method according to claim 2 and 3, characterized in that the PWM default value error (ΔPWM _potF1,2,3 ) per phase (U, V, W) is determined as a function of the comparison result and / or the determined voltage _drops . Method according to one of the preceding claims, characterized in that the PWM default value error per phase (U, V, W) according to equation 1)

if it is determined by the threshold value _comparison that the simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) of the phase (U, V, W) is positive, or according to equation 2)

is determined, if it is determined by the Schwellwertvergleich that the simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) of the phase (U, V, W) is negative, where .DELTA.PWM _potF1,2,3 the determined PWM default value _error per phase (U, V, W), PWM _1,2,3 denotes the PWM default value (PWM1, PWM2, PWM3) per phase (U, V, W), U _{T1,2,3 denotes} a circuit breaker voltage drop per phase (U , V, W), U _D1,2,3 a diode voltage drop per phase (U, V, W) and U _dc the _{DC link} voltage. Method according to one of the preceding claims, characterized in that the determined PWM default value error (ΔPWM _potF1,2,3 ) per phase (U, V, W) for providing corrected PWM default values (PWM1n, PWM2n, PWM3n) for the inverter each with the PWM default value (PWM1, PWM2, PWM3) of the phase (U, V, W) are added. Method according to one of the preceding claims, characterized in that a corrected PWM default value (PWM1n, PWM2n, PWM3n), which is less than zero percent or greater than one hundred percent, before being output to the inverter ( 1 ) is limited to zero percent or one hundred percent. Method according to one of the preceding claims, characterized in that the PWM default value error (ΔPWM _potF1,2,3 ) per phase (U, V, W) based on a means of target current specifications (I _sdRef , I _sqRef ), in particular by means of filtering of target current specifications (I _sdRef , I _sqRef ), simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) of the phase (U, V, W) is determined. Method according to one of the preceding claims, characterized in that a simulated phase _{current value} (I _s1Ref , I _s2Ref , I _s3Ref ) by means of filtering the target current specifications (I _sdRef , I _sqRef ) with a low-pass filter ( 27 ), in particular a digital filter, wherein the setpoint current specifications (I _sdRef , I _sqRef ) are provided in particular as time-discrete variables. Method according to one of the preceding claims, characterized in that the phase _{current values} simulated by the filtering (I _s1Ref , I _s2Ref , I _s3Ref ) _{correspond to} the actual phase _{current values of} the phases (U, V, W) of the _{induction machine} ( 4 ) correspond. Method according to one of the preceding claims, characterized in that the induction machine ( 4 ) is operated in a controlled manner during the method according to a field-oriented control, in particular with adjustable dynamics. Method according to one of the preceding claims, characterized in that the corrected and / or corrected and limited default value (PWM1n, PWM2n, PWM3n) per phase (U, V, W) for or to the inverter ( 1 ) is output for setting a voltage vector. Contraption ( 5 ) for the operation of a rotary field machine ( 4 ), in particular with an inverter ( 1 ), characterized in that the device ( 5 ) for carrying out the method according to one of the preceding claims, wherein for the operation of the inverter ( 1 ) corrected default values (PWM1n, PWM2n, PWM3n) by the device ( 5 ) to be provided. Contraption ( 5 ) according to claim 13, characterized in that the device has a control structure ( 7 ) for field-oriented control, in particular for field-oriented control with adjustable dynamics, wherein the device ( 5 ) provides corrected default values (PWM1n, PWM2n, PWM3n) in the course of the field-oriented control. Contraption ( 5 ) according to one of claims 13 or 14, characterized in that the device is a filter ( 27 ), in particular a digital filter, further comprising in particular a low-pass filter for filtering the setpoint current specifications (I _sdRef , I _SqRef ). Drive system ( 6 ) with a rotating field machine ( 4 ) and an inverter ( 1 ), characterized in that the drive system ( 6 ) for the operation of the induction machine ( 4 ) is designed according to one of claims 1 to 12.

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