DE102011078050A1 - Determining the rotor position of a synchronous machine - Google Patents

Abstract

In determining the rotor position of a synchronous machine 12, the following steps are performed. Acting on the synchronous machine 12 with a first voltage pulse; Measuring a first measured stator current at a first time t ₂ ; Calculating a first calculated stator current i _m ^{ph #} with a machine model 20 comprising a model 38 of the synchronous machine 12; Calculating a first differential current space vector Δi _m ^{ph #} from the first measured stator current and the first calculated stator current; Measuring a second measured stator current i _m ^ph at a second time t ₅ ; Calculating a second calculated stator current (i _m ^{ph #} ) with the machine model 20; Calculating a second differential current space vector Δi _m ^{ph #} from the second measured stator current and the second calculated stator current; Determining the rotor position from the first differential flow space vector and the second differential flow space vector. The machine model includes a model of a synchronous machine 12 upstream device.

Description

FIELD OF THE INVENTION

The invention relates to a method for determining the rotor position of a synchronous machine, a computer program, a computer-readable medium and a controller for a synchronous machine.

BACKGROUND OF THE INVENTION

For field-oriented current and speed control of a rotating or linear synchronous machine, the knowledge of the rotor position and the speed is usually required. For example, the rotor may be a rotor of a rotating synchronous machine. In particular, it may be necessary for the rotor position to be determined as accurately as possible at standstill and at low speeds in the speed range up to 10% of the rated speed. This allows an optimal start in the right direction of rotation, with the maximum desired torque and high efficiency can be achieved.

To avoid heat loss in the rotating or linear synchronous machine, the machine can also be preceded by an LC filter.

To determine the rotor position so far direct encoders (mechanical, optical, magnetic) are used, which can be expensive and prone to failure and may require appropriate space. Alternatively, methods are known which dispense with a direct encoder. Such a method is for example in the DE 10 2009 029 896 A1 described. This method requires a measurement of the voltages at the input of the machine. Due to the required potential separation between the machine and the signal evaluation circuit as well as due to strongly jumping reference potentials, such a voltage measurement can be relatively complex (component and circuit complexity, EMC).

Other known methods (eg. WO 92/19038 ) can only be used for synchronous machines, which are fed directly by a pulse inverter without LC filter. These methods are usually only suitable for determining the rotor position at standstill and can normally only be extended with very large restrictions in the dynamics and accuracy for the low-speed range.

SUMMARY OF THE INVENTION

It is an object of the invention to determine the rotor position of a synchronous machine without the aid of a voltage measurement.

This object is solved by the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims and from the following description.

A first aspect of the invention relates to a method for determining the rotor position of a synchronous machine. The synchronous machine can be a rotating or linear synchronous machine.

According to one embodiment of the invention, the method comprises the steps of: applying a first voltage pulse to the synchronous machine; Measuring a first measured stator current at a first time; Calculating a first calculated stator current with a machine model comprising a model of the synchronous machine; Calculating a first differential current space vector from the first measured stator current and the first calculated stator current; Measuring a second measured stator current at a second time; Calculating a second calculated stator current with the machine model; Calculating a second differential current space vector from the second measured stator current and the second calculated stator current; and determining the rotor position from the first differential current space vector and the second differential current space vector. So can like in the DE 10 2009 029 896 A1 described a rotor position can be calculated with the aid of a model of the synchronous machine.

In other words, the synchronous machine two alternating voltage pulses are switched. After each of the two voltage pulses, one stator current is measured and calculated, the stator current being calculated on the basis of a machine model. From the measured and calculated currents then the current position of the rotor is determined. It should be understood that the stator current (both measured and calculated) may include at least two components associated with at least two phases of the system. In principle, each stator current can therefore comprise at least two stator current components.

According to one embodiment of the invention, the machine model comprises a model of a device upstream of the synchronous machine. This device may, for example, a Pulse inverter or an LC filter. Thus, the process as compared to the DE 10 2009 029 896 A1 extended method that is suitable at least for determining the rotor position of rotating or linear synchronous machines.

As a result of the fact that the machine model comprises a model of the device arranged upstream of the synchronous machine, currents whose measured values are already present in the control of the synchronous machine can be included in the calculation of the rotor position. Such a current, for example, be the output current of the pulse inverter. Furthermore, in the case of a synchronous machine having a pulse inverter, as a rule, a setpoint voltage for the pulse inverter is present in the controller, which can be used to calculate the rotor position. With these additional sizes already present in the controller, the stator voltage can then be calculated. A measurement of the stator voltage is no longer necessary.

According to one embodiment of the invention, the first and / or second calculated stator current is calculated from a nominal output voltage of a pulse inverter and the first and / or second measured stator current. Thus, the machine voltages (i.e., stator voltage) required for the process can be calculated directly from the setpoint voltages of the pulse inverter using the already measured stator currents of the synchronous machine. As a rule, the real behavior of the pulse inverter is taken into account.

According to one embodiment of the invention, an output current from a pulse inverter is measured in front of an LC filter. The first and / or second calculated stator current is then calculated from the output current of the pulse inverter and the first and / or second measured stator current. In other words, measured output currents of the pulse inverter can be used to calculate the machine voltages anyway.

According to one embodiment of the invention, an AC current supplied to the synchronous machine is generated with a pulse inverter. In this case, the machine model may comprise a model of the pulse-controlled inverter, which is designed to calculate an output voltage of the pulse-controlled inverter from a nominal output voltage of the pulse-controlled inverter. As already stated, the output target voltage is usually present in the controller if the system comprises a pulse-controlled inverter.

According to one embodiment of the invention, the alternating current supplied to a synchronous machine is filtered by an LC filter. The machine model may then include a model of the LC filter configured to calculate a stator voltage from an input voltage or current and a measured stator current. The method is applicable to a synchronous machine with or without an upstream LC filter. If an LC filter is present, the machine model can be extended with a model of the LC filter. However, the method is also applicable to synchronous machines without LC filter.

According to one embodiment of the invention, the model of the synchronous machine is designed to calculate a further stator current from an input voltage and a measured stator current. The further stator current indirectly provides information about the rotor position, since the position of the rotor influences the inductance of the coils in the synchronous machine. By comparing the measured stator current with the calculated stator current, it is then possible to deduce the relative position of the phase windings and the permanent magnets in the rotor and thus of the stator and rotor.

In summary, the method can be used to determine the rotor position without a direct rotary encoder. The previously required voltage measurement can be omitted with the same accuracy of the position detection. The accuracy can be improved by optional consideration of the output currents of the pulse inverter. The method can be used with and without LC filter. Parameter variations of the machine and the LC filter can be corrected by means of tables. Due to a very fast measuring sequence, the regulation of the machine is not necessarily influenced by the position determination.

Another aspect of the invention relates to a computer program that, when executed on a processor, directs the processor to perform the steps of the method as described above and below. For example, a controller of the synchronous machine or of the entire drive system may have a processor on which such a computer program is executed.

A further aspect of the invention relates to a computer-readable medium on which such a computer program is stored. A computer-readable medium may be a floppy disk, a hard disk, a USB storage device, a RAM, a ROM, a FLASH or an EPROM. A computer-readable medium may also be a data communication network, such as the Internet, which allows the download of program code.

A further aspect of the invention relates to a controller for a synchronous machine adapted to carry out the steps of the method as described above and below. It is to be understood that the method can also be implemented completely or at least partially in hardware.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

1 schematically shows a drive system with a synchronous machine and its control according to an embodiment of the invention.

2 shows an equivalent circuit diagram for a phase of the filter and the synchronous machine of the 1 ,

3 FIG. 12 is a diagram illustrating the calculation of rotor position according to an embodiment of the invention. FIG.

4 shows a diagram with the temporal sequence of the voltage pulses according to an embodiment of the invention.

5 shows a module for simulating the stator current according to an embodiment of the invention.

6 shows a module for simulating the synchronous machine according to an embodiment of the invention.

7 shows a module for simulating the LC filter according to an embodiment of the invention.

8th shows a module for simulating the stator current according to another embodiment of the invention.

9 shows a module for simulating the LC filter according to an embodiment of the invention.

10 shows a module for simulating the stator current according to another embodiment of the invention.

Basically, identical or similar parts are provided with the same reference numerals.

DETAILED DESCRIPTION OF EMBODIMENTS

1 schematically shows a drive system 10 for feeding a rotating or linear synchronous machine 12 , which continues a pulse inverter 14 , an optional LC output filter 16 and a controller 18 includes. The pulse inverter 14 receives a DC voltage U _DC from a high voltage network generated therefrom on the basis of control commands from the controller 18 a three-phase alternating current i _p1 , i _p2 , i _p3 passing through the LC output filter 16 is converted into a filtered alternating current i _m1 , i _m2 , i _m3 . The filtered alternating current or the alternating current from the pulse inverter 14 then serves to drive the synchronous machine 12 , For this purpose, a magnetic field is generated in the windings in the stator, which forms a rotor 13 rotate with permanent magnets.

In general, the synchronous machine has 12 a runner 13 , the different positions, in the present case, for example, different angular positions can take. The current position of the synchronous machine 12 or the runner 13 can be determined by the method as described above and below.

2 shows an equivalent circuit diagram for the synchronous machine 12 and the LC filter 16 , It's just one of three phases 1 shown. The LC filter comprises an inductance L _f and a capacitance C _f . The synchronous ^{machine is} modeled by an internal resistance R _s and an inductance L _s ^ph . A dash under the voltage and current symbols indicates that these quantities are space vectors, ie, comprise one component for each phase. In addition, it should be understood that the following calculation is performed not only for one phase but for at least two phases.

3 shows a diagram that represents the calculation of the rotor position. The entire calculation can be in the controller 18 be carried out and there either as a hardware module 19 or as a software module 19 be implemented. The module 19 includes a submodule 20 for modeling (ie modeling) the stator current i _m ^{ph #} . The module 20 can as a model 20 of the drive system 10 be understood in the controller 18 is modeled. Next includes the module 19 latches 22 which store and pass on a measured quantity or a calculated quantity at a specific time and a submodule 24 for calculating the rotor position. The method for calculating the rotor position executed with this module will be described in more detail below.

4 shows a diagram with the time sequence of the voltage pulses during the Method are generated, or a timing of the calculation of the rotor position.

In a first pulse interval 26 between the times t ₀ and t ₁ is a first voltage pulse by the controller 28 generated. For this purpose, the controller, for example, the pulse inverter 14 switch accordingly. The synchronous machine 12 can be acted upon by a first voltage pulse at the time t = t ₀ the duration t ₁ - t ₀ .

In a first measurement interval 28 between t ₀ and t ₂ , the stator current i _m ^{ph is} measured. In the first measurement interval 28 The calculation of simulated machine flows i _m ^{ph # is also carried out} with the submodule 20 from the measured machine currents and from simulated machine voltages using an idealized simulation of the synchronous machine.

Subsequently, the machine currents are measured in at least two of the phases at a time t = t ₂ > t ₀ . A first measured stator current i _m ^ph (t ₂ ) is determined at a first time t ₂ . This is done via the corresponding memory element 22 ,

At time t ₂ , a first calculated stator current i _m ^{ph #} (t ₂ ) with the corresponding memory element is also detected 22 determined.

From the first measured stator current i _m ^ph (t ₂ ) and the first calculated stator current i _m ^{ph #} (t ₂ ), a first differential current space vector Δi _m ^{ph #} (t ₂ ) is then formed by differentiating the two currents. As already mentioned, the currents are determined for at least two phases. Therefore, a space vector can also be formed from them.

Analogously, the determination of measured and calculated stator currents takes place during a second measurement interval 32 , At time t = t ₃ > t ₂ , the synchronous machine becomes 12 with a second voltage pulse of duration t ₄ -t ₃ during a second pulse interval 30 applied. This should be rotated by more than +/- 90 ° with respect to the first voltage pulse, so that the rotor position at the end can be clearly calculated.

Subsequently, the stator currents i _m ^{ph are} measured again in at least two of the phases at a time t = t ₅ > t ₃ . During the entire time period t ₅ -t ₃ , the calculation of simulated stator currents i _m ^{ph # is performed} with the module 20 from the measured stator currents i _m ^ph . The measured currents i _m ^ph (t ₅ ) and calculated currents i _m ^{ph #} (t ₅ ) at the second time t ₅ are again via the corresponding memory elements 22 determined.

The following is the calculation of a second differential current space vector Δi _m ^{ph #} (t ₅ ) by taking the difference between the measured stator currents i _m ^ph (t ₅ ) and the simulated stator currents i _m ^{ph #} (t ₅ ) at time t = t ₅ > t ₃ .

The sought-after rotor position is then calculated using a linear combination of the determined residual current space vectors Δi _m ^{ph #} (t ₂ ), Δi _m ^{ph #} (t ₅ ). This can be done for example by solving a system of equations that reflects the structure of the synchronous machine and in particular the coils and permanent magnets. However, it is also possible that a rotor position is determined using a table from the linear combinations.

Especially in the range of low speeds, the method is as in DE 10 2009 029 896 A1 described fully functional. If the time periods t ₂ - t ₀ and t ₅ - t ₃ are chosen as small as possible (the synchronous machine 12 due to the voltage pulses in the magnetic circuit should be saturated), the control of the stator current is essentially not affected and can be continued without interruption at a standstill and at low speeds.

5 shows an embodiment of a module 20a for simulating the stator current i _m ^{ph #} . The module comprises a submodule 34 for the simulation of the pulse inverter 14 , a submodule 36 to simulate the LC filter 16 and a submodule 38 to simulate the synchronous machine 12 ,

The module 34 receives a nominal output voltage u _p ^{ph *} , which is converted into an output voltage u _p ^{ph *} . The calculation of the simulated output voltages u _p ^{ph * of} the pulse inverter 14 takes place via an idealized simulation of the electrical properties of the pulse inverter 14 , The necessary locking times, the switching dead times and the signal propagation times are taken into account. The input variables are the nominal output voltages u _p ^{ph * of} the pulse-controlled inverter.

6 shows a module 38 to simulate the synchronous machine 12 as it is in the module 20a of the 5 could be used. In the module 38 is an internal resistance member 40 modeled that generates a voltage from the measured stator current i _m ^ph . From this voltage and the calculated voltage u _m ^{ph #} , a difference is formed by the integrator 42 is added up to the calculated stator current i _m ^{ph #} .

7 shows a module 36 to simulate the LC filter 16 as it is in the module 20a of the 5 could be used. From the calculated output voltage u _p ^{ph #} and a calculated Machine voltage u _m ^{ph #} is a difference formed by a first integrator 44 , which models the inductance L _f , is added up to a current i _p ^{ph #} . With this current i _p ^{ph #} and the measured current i _m ^ph , a difference is formed, which is a second integrator 46 , which models the capacitance C _f , is summed up to the machine voltage u _m ^{ph #} . The machine voltage u _m ^{ph #} goes through a feedback loop in front of the integrator 44 formed difference. The input variables of the module 36 are the measured machine currents i _m ^ph and the simulated output voltages u _p ^{ph # of} the pulse inverter.

8th shows a further embodiment of a module 20b for simulating the stator current i _m ^{ph #} . The module comprises a submodule 50 to simulate the LC filter 16 and a submodule 38 to simulate the synchronous machine 12 , The module 38 can according to the 6 be constructed. As in a drive system 10 with LC filter 16 To improve the Statorstromregelung often the output currents i _p ^{ph of} the pulse inverter 14 metrologically recorded, these variables can be incorporated into the process. Are these currents i _p ^ph the controller 18 available, the method can be simplified in this way.

9 shows a module 50 to simulate the LC filter 16 as it is in the module 20b of the 8th could be used. As in the embodiment of the 8th the measured output current i _p ^ph at the pulse inverter 14 in the system, it must be in contrast to the module 36 from the 7 not be calculated. The module 50 can thus be used as the second part of the module 36 be understood. The simulation of the machine voltages u _m ^{ph #} can therefore be made directly from the measured output currents i _p ^{ph of} the pulse-controlled inverter 14 and the measured machine currents i _m ^ph .

10 shows a further embodiment of a module 20c for simulating the stator current i _m ^{ph #} . The module comprises a submodule 34 for the simulation of the pulse inverter 14 and a submodule 38 to simulate the synchronous machine 12 , The module 38 can according to the 6 be constructed. In a drive systems 10 without LC filter 16 The method can be simplified by simulating the machine currents i _m ^{ph #} directly from the setpoint voltages u _p ^{ph * of} the pulse-controlled inverter 14 and the measured machine currents i _m ^ph .

In addition, it should be noted that "encompassing" does not exclude other elements or steps, and "a" or "an" does not exclude a multitude. It should also be appreciated that features or steps described with reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limiting.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009029896 A1 [0004, 0009, 0011, 0048]
• WO 92/19038 [0005]

Claims (9)

Method for determining the rotor position of a synchronous machine ( 12 ), comprising the steps of: charging the synchronous machine ( 12 ) with a first voltage pulse ( 26 ); Measuring a first measured stator current (i _m ^ph ) at a first time (t ₂ ); Calculation of a first calculated stator current (i _m ^{ph #} ) with a machine model ( 20 . 20a . 20b . 20c ), which is a model ( 38 ) of the synchronous machine ( 12 ); Calculating a first differential current space vector (Δi _m ^{ph #} ) from the first measured stator current and the first calculated stator current; Measuring a second measured stator current (i _m ^ph ) at a second time (t ₅ ); Calculation of a second calculated stator current (i _m ^{ph #} ) with the machine model ( 20 . 20a . 20b . 20c ); Calculating a second differential current space vector (Δi _m ^{ph #} ) from the second measured stator current and the second calculated stator current; Determining the rotor position from the first differential current space vector and the second differential current space vector; characterized in that the machine model is a model ( 34 . 36 . 50 ) one of the synchronous machine ( 12 ) upstream device ( 14 . 16 ). The method of claim 1, wherein the first and / or second calculated stator current (i _m ^{ph #} ) from a nominal output voltage (u _p ^{ph *} ) of a pulse inverter ( 14 ) and the first and / or second measured stator current (i _m ^ph ). Method according to claim 1 or 2, wherein an output current (i _p ^ph ) from a pulse inverter ( 14 ) in front of an LC filter ( 16 ) is measured; wherein the first and / or second calculated stator current (i _m ^{ph #} ) from the output current (i _p ^ph ) of the pulse inverter and the first and / or second measured stator current (i _m ^ph ) is calculated. Method according to one of the preceding claims, wherein one of the synchronous machine ( 12 ) supplied alternating current with a pulse inverter ( 14 ) is produced; where the machine model ( 20a . 20c ) a model ( 34 ) of the pulse inverter ( 14 ); where the model ( 34 ) of the pulse-controlled inverter is executed from a nominal output voltage (u _p ^{ph *} ) of the pulse-controlled inverter ( 14 ) an output voltage (u _p ^{ph #} ) of the pulse inverter ( 14 ) to calculate. Method according to one of the preceding claims, wherein one of the synchronous machine ( 12 ) supplied alternating current through an LC filter ( 16 ) is filtered; where the machine model ( 20a . 20b ) a model ( 36 . 50 ) of the LC filter ( 16 ); where the model ( 36 . 50 ) of the LC filter ( 16 ) is designed to calculate a stator voltage (u _m ^{ph #} ) from an input voltage (u _p ^{ph #} ) or an input current (i _p ^ph ) and a measured stator current (i _m ^{ph #} ). Method according to one of the preceding claims, wherein the model ( 38 ) of the synchronous machine ( 12 ) is designed to calculate a stator current (i _m ^{ph #} ) from an input voltage (u _m ^{ph #} ) and a measured stator current (i _m ^ph ). A computer program which, when executed on a processor, instructs the processor to perform the steps of the method of any one of claims 1 to 6. Computer-readable medium on which a computer program according to claim 7 is stored. Control ( 18 ) for a synchronous machine ( 12 ), which is adapted to perform the steps of the method according to one of claims 1 to 6.

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