CN113014174B - Method and system for detecting initial position of motor rotor and related components - Google Patents
Method and system for detecting initial position of motor rotor and related components Download PDFInfo
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- CN113014174B CN113014174B CN202110352360.8A CN202110352360A CN113014174B CN 113014174 B CN113014174 B CN 113014174B CN 202110352360 A CN202110352360 A CN 202110352360A CN 113014174 B CN113014174 B CN 113014174B
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- 238000000034 method Methods 0.000 title claims abstract description 59
- 238000005070 sampling Methods 0.000 claims abstract description 90
- 238000002347 injection Methods 0.000 claims description 32
- 239000007924 injection Substances 0.000 claims description 32
- 238000001514 detection method Methods 0.000 claims description 19
- 230000001939 inductive effect Effects 0.000 claims description 12
- 238000012423 maintenance Methods 0.000 claims description 10
- 238000004146 energy storage Methods 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 4
- 238000007599 discharging Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/24—Vector control not involving the use of rotor position or rotor speed sensors
- H02P21/32—Determining the initial rotor position
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
- H02P21/18—Estimation of position or speed
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2203/00—Indexing scheme relating to controlling arrangements characterised by the means for detecting the position of the rotor
- H02P2203/03—Determination of the rotor position, e.g. initial rotor position, during standstill or low speed operation
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2203/00—Indexing scheme relating to controlling arrangements characterised by the means for detecting the position of the rotor
- H02P2203/09—Motor speed determination based on the current and/or voltage without using a tachogenerator or a physical encoder
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- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
The application discloses a method, a system and related components for detecting the initial position of a motor rotor, wherein the method comprises the following steps: measuring positive current and reverse current between every two phase voltage output ends of the motor to obtain six sampling currents; calculating the initial position of a rotor of the motor; and when each sampling current is measured, closing the upper half bridge arm of the first phase bridge arm and the lower half bridge arm of the second phase bridge arm, injecting a voltage pulse maintaining the minimum on-time, then disconnecting the lower half bridge arm of the second phase bridge arm, closing the upper half bridge arm of the second phase bridge arm, and sampling the current circulation passing through the upper half bridge arm of the second phase bridge arm. When each sampling current is obtained, the voltage pulse is injected firstly to be disconnected, a current loop between the two upper half bridge arms and the motor inductor is established, and the current in the current loop is taken as the current to be sampled and can be kept for a longer time, so that the requirement on the sampling rate of hardware is lower, the noise influence of hardware with high sampling rate is avoided, and the hardware cost is reduced.
Description
Technical Field
The invention relates to the field of motor control, in particular to a method and a system for detecting an initial position of a motor rotor and a related component.
Background
At present, the traditional method for detecting the initial position of the rotor of the permanent magnet synchronous motor based on the current interpolation of the inductance saturation effect can be suitable for most motors, and the initial angle of the rotor of the motor can be estimated more accurately. However, in practical engineering application, it is found that when the inductance of the motor is small, the current rise rate is large due to injection of motor voltage in unit time, and the maximum current value is difficult to accurately detect when the sampling rate is low, so that the requirement on the sampling rate of the analog-to-digital conversion device is high at some moments, but the analog-to-digital converter with a high sampling rate has relatively high cost, and meanwhile, the magnetic pole position identification result is influenced by high precision of analog-to-digital conversion detection and noise.
Therefore, how to provide a solution to the above technical problems is a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the present invention provides a method, a system and related components for detecting an initial position of a rotor of an electric machine without requiring a high sampling rate. The specific scheme is as follows:
a method for detecting the initial position of a motor rotor comprises the following steps:
measuring positive current and reverse current when every two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents;
calculating the initial position of the rotor of the motor by using the six sampling currents;
the process of measuring the positive current or the reverse current when every two phase voltage output ends of the motor are conducted according to the minimum turn-on time comprises the following steps:
closing an upper half bridge arm of a first phase bridge arm and a lower half bridge arm of a second phase bridge arm, injecting a voltage pulse for maintaining the minimum switching time, then disconnecting the lower half bridge arm of the second phase bridge arm, closing the upper half bridge arm of the second phase bridge arm, and sampling a current circulation passing through the upper half bridge arm of the second phase bridge arm;
two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
Preferably, before the measuring positive current and negative current when each two phase voltage output ends of the motor are conducted according to the minimum on-time to obtain six sampling currents, the method further includes:
determining the minimum on-time of the motor.
Preferably, the process of determining the minimum on-time of the motor includes:
sequentially measuring positive current and reverse current when the two phase voltage output ends of the motor are conducted by using voltage pulses with the maintenance time taking a preset minimum time as a starting point, a preset time period as a step length and a preset maximum time as an end point until the positive current or the reverse current reaches a preset current, and recording the maintenance time corresponding to the current voltage pulse as the shortest injection time to obtain three shortest injection times;
and comparing the three shortest injection times, and determining the shortest injection time as the minimum on-time of the motor.
Preferably, the preset maximum time is determined according to the preset current, the inductance of the motor and the bus voltage value.
Preferably, the process of calculating the initial position of the rotor of the motor by using the six sampling currents includes:
calculating an initial position of a rotor of the motor according to the following formula:
I current1 ＝I UV -I VU ；
I current2 ＝I VW -I WV ；
I current3 ＝I WU -I UW ；
wherein, three phase voltage output ends of the motor are respectively a U end, a V end and a W end, I UV And I VU Positive and reverse currents, I, of the U and V terminals, respectively VW And I WV Positive and reverse currents, I, of the V and W terminals, respectively WU And I UW Positive and reverse currents of the W terminal and the U terminal, respectively, and θ is the rotor initial position.
Preferably, the process of measuring the positive current and the reverse current when conducting between every two phase voltage output ends of the motor comprises:
the method comprises the steps of firstly measuring positive currents when current two phase voltage output ends of the motor are conducted, and then measuring reverse currents when the current two phase voltage output ends are conducted.
Preferably, the process of measuring the positive current or the reverse current when conducting between each two phase voltage output terminals of the motor according to the minimum on-time further comprises:
and disconnecting the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm to release the inductive energy storage of the motor.
Correspondingly, this application still discloses a detecting system of electric motor rotor initial position, includes:
the current measuring module is used for measuring positive current and reverse current when every two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents;
the calculation module is used for calculating the initial position of the rotor of the motor by using the six sampling currents;
wherein, the current measurement module includes first action unit, second action unit and sampling unit, wherein:
the first action unit closes the upper half bridge arm of the first phase bridge arm and the lower half bridge arm of the second phase bridge arm and injects a voltage pulse for maintaining the minimum turn-on time; then the second action unit disconnects the lower half bridge arm of the second phase bridge arm and then closes the upper half bridge arm of the second phase bridge arm, and the sampling unit samples the current circulation passing through the upper half bridge arm of the second phase bridge arm;
two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
Correspondingly, this application still discloses a detection device of electric motor rotor initial position, includes:
the system comprises a controller, a power supply, a three-phase bridge arm and a sampling circuit, wherein the three-phase bridge arm is connected with the power supply and a motor; wherein,
the controller measures positive current and reverse current when every two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents; calculating the initial position of the rotor of the motor by using the six sampling currents;
the process that the controller measures the positive current or the reverse current when every two phase voltage output ends of the motor are conducted according to the minimum opening time comprises the following steps:
sending a control instruction to the three-phase bridge arms and the power supply to close an upper half bridge arm of a first-phase bridge arm and a lower half bridge arm of a second-phase bridge arm and inject a voltage pulse for maintaining the minimum on-time, then disconnecting the lower half bridge arm of the second-phase bridge arm and then closing the upper half bridge arm of the second-phase bridge arm; acquiring the sampling current sent by the sampling circuit after sampling the current circulation passing through the upper half bridge arm of the second-phase bridge arm;
the first phase bridge arm and the second phase bridge arm are any two phase bridge arms in the three phase bridge arms, two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel to output ends of the power supply, a midpoint of the first phase bridge arm and a midpoint of the second phase bridge arm are respectively connected with current two phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
Correspondingly, this application still discloses a motor assembly, includes:
a device for detecting the initial position of a rotor of an electric machine as described above;
and the motor is connected with the detection device.
When each sampling current is obtained, firstly injecting voltage pulses into two conducted phase voltage output ends for the minimum opening time, then disconnecting the voltage pulses, establishing a current loop between the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm and a motor inductor, and keeping the current in the current loop as the current to be sampled for a long time, so that the requirement on the sampling rate of hardware is low, the influence of the hardware with high sampling rate on the noise of detection is avoided, and the hardware cost is reduced when the method is implemented.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flowchart illustrating steps of a method for detecting an initial position of a rotor of an electric machine according to an embodiment of the present invention;
FIG. 2 is a flow chart illustrating the sub-steps of a method for detecting an initial position of a rotor of an electric machine according to an embodiment of the present invention;
FIG. 3 is a hardware diagram illustrating a method for detecting an initial position of a rotor of a motor according to an embodiment of the present invention;
FIG. 4 is a timing diagram of a current flow during the detection of the initial position of the rotor of the motor according to an embodiment of the present invention;
FIG. 5 is a structural distribution diagram of a system for detecting an initial position of a rotor of a motor according to an embodiment of the present invention;
fig. 6 is a structural distribution diagram of a device for detecting an initial position of a rotor of an electric machine according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
When the inductance of the motor is small, the current rise rate is large due to injection of motor voltage in unit time, and the maximum current value is difficult to accurately detect when the sampling rate is low, so that the sampling rate requirement on an analog-digital conversion device is high at certain moments, but the cost of an analog-digital converter with a high sampling rate is relatively high, and meanwhile, the magnetic pole position identification result is influenced by the high precision of analog-digital conversion detection and noise. According to the method, a current loop between the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm and the motor inductor is established, and the current in the current loop is used as the current to be sampled and can be kept in the current loop for a long time, so that the requirement on the sampling rate of hardware is low, the influence of the hardware with high sampling rate on the detection noise is avoided, and the hardware cost in the implementation of the method is reduced.
The embodiment of the invention discloses a method for detecting the initial position of a motor rotor, which is shown in figure 1 and comprises the following steps:
s1: measuring positive current and reverse current when each two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents;
s2: calculating the initial position of the rotor of the motor by using the six sampling currents;
it can be understood that, the process of calculating the initial position of the rotor of the motor by using six sampling currents in step S2 specifically includes:
calculating the initial position of the rotor of the motor according to the following formula:
I current1 ＝I UV -I VU ；
I current2 ＝I VW -I WV ；
I current3 ＝I WU -I UW ；
wherein, three phase voltage output ends of the motor are respectively a U end, a V end and a W end, I UV And I VU Positive and reverse currents, I, at the U and V terminals, respectively VW And I WV Positive and reverse currents, I, at terminals V and W, respectively WU And I UW Positive and reverse currents at W and U terminals, theta is initial position of rotor, I current1 、I current2 And I current3 Respectively, the intermediate current between every two of the three phase voltage output ends.
Further, referring to fig. 2, the step S1 of measuring the positive current or the reverse current when conducting between each two phase voltage output terminals of the motor according to the minimum on-time includes:
s11: closing an upper half bridge arm of the first phase bridge arm and a lower half bridge arm of the second phase bridge arm and injecting a voltage pulse for maintaining the minimum turn-on time;
s12: disconnecting the lower half bridge arm of the second phase bridge arm;
s13: closing the upper half bridge arm of the second phase bridge arm;
it is understood that step S13 is implemented with consideration of the insertion of dead time, i.e. the action time interval between step S12 and step S13.
S14: sampling current circulation passing through the upper half bridge arm of the second phase bridge arm;
the two ends of the first phase bridge arm and the two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with the current two phase voltage output ends, and the current circulation is used as a positive current or a reverse current corresponding to the current voltage pulse.
The step S14 may specifically include sampling the current loop passing through the upper half bridge arm of the second-phase bridge arm for multiple times, and determining the sampled current measured this time after data pre-screening.
It can be understood that, the current circulating current gradually attenuates at a slower speed, and after obtaining an effective sampling current in step S14, the inductive energy storage can be released at an accelerated speed, so as to increase the sampling speed of the whole method, that is, the step S1 measures the positive current or the reverse current when the two phase voltage output ends of the motor are conducted according to the minimum on-time, and further includes:
s15: and disconnecting the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm to release the inductive energy storage of the motor.
Specifically, referring to fig. 3, three phase voltage output terminals of the motor M are a U terminal, a V terminal, and a W terminal, three bridge arms in the circuit are connected to the three phase voltage output terminals through respective midpoints, and upper half bridge arms and lower half bridge arms of the three bridge arms are simplified into switches 1 to 6 in fig. 3. Step S1 measures a positive current or a reverse current when each two phase voltage output terminals of the motor are connected according to the minimum on-time, and finally obtains respective positive currents and reverse currents of the U terminal, the V terminal, the W terminal, and the U terminal under three conditions, where the positive currents and the reverse currents under each determined condition are not in a specific direction of an actual current but are defined as currents in two opposite directions passing through an inductor, and a current flowing from a first phase voltage output terminal to a second phase voltage output terminal through the inductor may be referred to as a positive current, or a current flowing from the second phase voltage output terminal to the first phase voltage output terminal through the inductor may be referred to as a positive current, but it should be noted that in the same test, directions of the three positive currents under three conditions should be the same, and the reverse currents are the same. Normally, the sampling process of positive current and reverse current under the same condition is continuous, so that the previous sampling can be demagnetized, and the interference of the last sampling on the motor inductance is eliminated.
Specifically, the process of measuring the positive current and the reverse current when each two phase voltage output ends of the motor are conducted includes: the method comprises the steps of firstly measuring positive currents when current two phase voltage output ends of the motor are conducted, and then measuring reverse currents when the current two phase voltage output ends are conducted.
Further, the generation of the two currents in different directions can use the same set of bridge arms to act but apply two times of voltage pulses in opposite directions, or apply voltage pulses in the same direction but select opposite half-bridge arms on the on-off of the bridge arms, similar to positive and negative currents, and the upper half bridge arm and the lower half bridge arm in the embodiment are only used for distinguishing the connection relationship and are not the physical positions of the actual bridge arms.
Taking a U end and a V end as an example, at this time, a first-phase bridge arm is a bridge arm of a switch 1 and a switch 2 connected to the U end, a second-phase bridge arm is a bridge arm of a switch 3 and a switch 4 connected to the V end, and assuming that the switch 1 and the switch 3 are upper half bridge arms of respective bridge arms and the switch 2 and the switch 4 are lower half bridge arms of respective bridge arms, the method for obtaining positive and negative currents by applying voltage pulses in the same direction specifically includes: firstly, a switch 1 and a switch 4 are turned on, voltage pulse for maintaining the minimum on-time is injected, then the switch 4 is turned off, and then a switch 3 is turned on, at the moment, the switch 1, the switch 3 and the inductance of the motor form a current loop, at the moment, the current loop is stable, and the analog-to-digital converter is allowed to sample for a long time to obtain a positive current; and after sampling is finished, the switch 1 and the switch 3 are turned off to release the inductive energy storage of the motor.
TABLE 1 Current sampling sequence of actions
| Section | Conduction switch tube | Sampling judgment current | |
| 0 | 1. 4 conducting | |
|
| 1 | 1 conducting through | |
|
| 2 | 1. 3 conducting through | Circular current T circ | The collected current value is I UV |
| 3 | Full shut-off | Full turn-off T close Discharge of electricityInductive current | |
| 4 | 2. 3 conducting through | |
|
| 5 | 3 conducting through | |
|
| 6 | 1. 3 conducting through | Circulation T circ | The collected current value is I VU |
| 7 | Full shut-off | Full turn-off T close Discharging inductive current | |
| 8 | 3. 6 conducting through | Conduction time T open | |
| 9 | 3 conducting through | Dead zone T death | |
| 10 | 3. 5 conducting through | Circular current T circ | The collected current value is I VW |
| 11 | Full closing | Full turn-off T close Discharging the inductive current | |
| 12 | 4. 5 conducting through | |
|
| 13 | 5 conducting through | |
|
| 14 | 3. 5 conducting through | Circular current T circ | The collected current value is I WV |
| 15 | Full shut-off | Full turn-off T close Discharging the inductive current | |
| 16 | 1. 6 conducting through | Conduction time T open | |
| 17 | 1 conducting through | Dead zone T death | |
| 18 | 1. 5 conducting through | Circulation T circ | The collected current value is I UW |
| 19 | Full shut-off | Full turn-off T close Discharging the inductive current | |
| 20 | 2. 5 conducting through | Conduction time T open | |
| 21 | 5 conducting through | Dead zone T death | |
| 22 | 1. 5 conducting through | Circular current T circ | The collected current value is I WU |
| 23 | Full shut-off | Full turn-off T close Discharging the inductive current |
See FIG. 4, in which the injection duration of the voltage pulse is the minimum on-time T open The current rises in a slope during the injection process and then enters a current steady state, and the state maintaining time is the dead time T death And switch 3 closing time T circ After sampling, entering an inductive energy storage and release process, and consuming time T close The current gradually decreases to 0. Then switch 2 and switch 3 are switched on, voltage pulse is injected, switch 2 is switched off, switch 1 is switched on, sampling is carried out to obtain reverse current, and after sampling is finished, switch 1 and switch 3 are switched off to release inductive energy storage of the motor. The six sampling currents are sampled according to the idea, and the specific action sequence can be carried out according to the table 1.
It can be understood that table 1 only provides an action execution idea, and this embodiment does not limit the sampling sequence of the positive and negative currents at the two phase output ends, as long as the sampling of the positive and negative currents is continuous under the same condition, in this embodiment, the conducting bridge arms corresponding to the current loops of the positive and negative currents under the same condition may be the same or different, and the applying conditions of the positive and negative currents under the same condition may be the positive and negative of the voltage pulse, or the opposite conducting bridge arms.
When each sampling current is obtained, firstly injecting voltage pulses into two conducted phase voltage output ends for the minimum opening time, then disconnecting the voltage pulses, establishing a current loop between the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm and a motor inductor, and keeping the current in the current loop as the current to be sampled for a long time, so that the requirement on the sampling rate of hardware is low, the influence of the hardware with high sampling rate on the noise of detection is avoided, and the hardware cost is reduced when the method is implemented.
The embodiment of the invention discloses a specific method for detecting the initial position of a motor rotor, and compared with the previous embodiment, the embodiment further explains and optimizes the technical scheme.
Specifically, step S1 includes, before obtaining six sampling currents, measuring a positive current and a negative current when each two phase voltage output terminals of the motor are connected according to the minimum on-time, and determining the minimum on-time of the motor.
Specifically, the process of determining the minimum on-time of the motor includes:
sequentially measuring positive current and reverse current when the two phase voltage output ends of the motor are conducted by using voltage pulses with the maintenance time taking a preset minimum time as a starting point, a preset time period as a step length and a preset maximum time as an end point until the positive current or the reverse current reaches a preset current, and recording the maintenance time corresponding to the current voltage pulse as the shortest injection time to obtain three shortest injection times;
and comparing the three shortest injection times, and determining the shortest injection time as the minimum turn-on time.
Further, the process of measuring the positive current and the reverse current when the connection between each two phase voltage output ends of the motor is successively performed by using the voltage pulse with the holding time taking the preset minimum time as a starting point, the preset time period as a step length, and the preset maximum time as an end point may further include:
and if the positive current and the reverse current do not reach the preset current all the time, judging that the equipment has a fault, and stopping detection.
It will be appreciated that the steps of measuring the positive and negative currents when determining the minimum on-time areThe specific steps of step S1 in the above embodiment are the same, and the details may be directly referred to, where the difference between the two steps is that the injection time of the voltage pulse changes many times, the start point of the injection time is set to a preset minimum time for measuring the positive and negative currents at each two phase voltage output terminals, if neither the collected positive current nor the collected negative current reaches the preset current, the injection time is increased by one step length and the positive and negative currents are collected again until the positive current or the negative current reaches the preset current, and the holding time corresponding to the current voltage pulse is the shortest injection time, so as to obtain three shortest injection times T UV 、T VW 、T WU Then, the minimum shortest injection time is selected to be determined as the minimum opening time T required in the next step open . It should be noted that if the injection time is increased until the preset maximum time, and the positive and negative currents under the same condition still do not reach the preset current, the determination time fails, the device fails, and the subsequent detection is terminated.
It is understood that the preset current in this embodiment may be specifically set to a peak rated current of the motor, the current cannot exceed an overcurrent point of a frequency converter implementing the method, and the preset maximum time may be determined according to the preset current, an inductance of the motor, and a bus voltage value, where the specific determination method is that the preset maximum time = the preset current/the inductance/the bus voltage value. Specifically, taking the U terminal and the V terminal of the motor in fig. 3 as an example, the sequence of the positive and negative current operations can be shown in table 2:
TABLE 2 sequence of actions determined by shortest injection time
It should be understood that table 2 is only an example, and the specific action switch and the action sequence may be selected according to the actual implementation, which is not limited in this embodiment.
Further, if the minimum on-time is successfully determined, in the process of determining the minimum on-time in this embodiment, in fact, under polling voltage pulses of different holding times including the minimum on-time, positive currents and negative currents at any two phase voltage output ends may be recorded in a table, and in step S1, six sampling currents corresponding to the minimum on-time are determined by directly looking up the table, and redundant sampling does not need to be repeated again, so that the detection time is saved, and the efficiency is improved.
Correspondingly, the embodiment of the present application further discloses a system for detecting an initial position of a rotor of an electric machine, which is shown in fig. 5 and includes:
the current measuring module 1 is used for measuring positive current and reverse current when each two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents;
the calculation module 2 is used for calculating the initial position of the rotor of the motor by using the six sampling currents;
wherein, the current measurement module 1 includes a first action unit 11, a second action unit 12 and a sampling unit 13, wherein:
the first action unit 11 closes the upper half bridge arm of the first phase bridge arm and the lower half bridge arm of the second phase bridge arm and injects a voltage pulse for maintaining the minimum turn-on time; then the second action unit 12 opens the lower half bridge arm of the second phase bridge arm, closes the upper half bridge arm of the second phase bridge arm, and the sampling unit 13 samples the current circulation passing through the upper half bridge arm of the second phase bridge arm;
two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulation is used as a positive current or a reverse current corresponding to a current voltage pulse.
In the embodiment, when each sampling current is obtained, the voltage pulse is injected into the two conducted phase voltage output ends at the minimum opening time, then the voltage pulse is cut off, and a current loop between the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm and the motor inductor is established.
In some specific embodiments, the detection system further comprises a time determination module 3 for determining a minimum on-time of the motor.
In some specific embodiments, the time determination module 3 includes:
the time measuring unit 31 is configured to successively measure a positive current and a reverse current when each two phase voltage output ends of the motor are switched on by using a voltage pulse with a preset minimum time as a starting point, a preset time period as a step length, and a preset maximum time as an end point in the maintenance time until the positive current or the reverse current reaches a preset current, and record the maintenance time corresponding to the current voltage pulse as a shortest injection time to obtain three shortest injection times;
a time determining unit 32, configured to compare the three shortest injection times, and determine the shortest injection time that is the smallest as the minimum on-time.
Further, the time determination module 3 further includes:
and a fault determination unit 33, configured to determine that the device is faulty and terminate the detection if both the positive current and the reverse current have not reached the preset current.
In some specific embodiments, the preset maximum time is determined according to the preset current, the inductance of the motor and a bus voltage value.
In some specific embodiments, the calculation module 2 is specifically configured to:
calculating the initial position of the rotor of the motor according to the following formula:
I current1 ＝I UV -I VU ；
I current2 ＝I VW -I WV ；
I current3 ＝I WU -I UW ；
wherein three phase voltage output ends of the motor are respectively provided with three phase voltage output endsIs U terminal, V terminal and W terminal, I UV And I VU Positive and reverse currents, I, of the U and V terminals, respectively VW And I WV Positive and reverse currents, I, of the V and W terminals, respectively WU And I UW Positive and reverse currents of the W terminal and the U terminal, respectively, and θ is the rotor initial position.
In some specific embodiments, the current measurement module 1 further includes a third action unit 14, configured to disconnect the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm to release the stored energy of the inductance of the motor.
In some specific embodiments, the sampling unit 13 is specifically configured to:
and sampling the current circulation passing through the upper half bridge arm of the second phase bridge arm for multiple times, and determining the sampling current measured this time after data pre-screening.
Correspondingly, the embodiment of the present application further discloses a device for detecting an initial position of a rotor of an electric machine, as shown in fig. 6, including:
the system comprises a controller 01, a power supply 02, a three-phase bridge arm 03 and a sampling circuit 04, wherein the three-phase bridge arm 03 is connected with the power supply 02 and a motor M; wherein,
the controller 01 measures a positive current and a reverse current when each two phase voltage output ends of the motor are conducted according to the minimum turn-on time, and six sampling currents are obtained; calculating the initial position of the rotor of the motor by using the six sampling currents;
the process of the controller 01 measuring the positive current or the reverse current when the two phase voltage output ends of the motor are conducted according to the minimum turn-on time comprises the following steps:
sending a control instruction to the three-phase bridge arm 03 and the power supply 02 to close the upper half bridge arm of the first-phase bridge arm and the lower half bridge arm of the second-phase bridge arm and inject a voltage pulse maintaining the minimum on-time, then disconnecting the lower half bridge arm of the second-phase bridge arm and then closing the upper half bridge arm of the second-phase bridge arm; acquiring a sampling current sent by a sampling circuit 04 after sampling the current circulation passing through the upper half bridge arm of the second-phase bridge arm;
the first-phase bridge arm and the second-phase bridge arm are any two-phase bridge arm in the three-phase bridge arm 03, two ends of the first-phase bridge arm and two ends of the second-phase bridge arm are connected in parallel to the output end of the power supply 02, the middle point of the first-phase bridge arm and the middle point of the second-phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current serves as positive current or reverse current corresponding to current voltage pulse.
It will be appreciated that the three phase legs are controlled by switches 1-6 to turn on the upper or lower half bridge of each phase leg as shown in figure 6.
In some specific embodiments, the controller 01 is further configured to: the minimum on-time of the motor M is determined.
In some specific embodiments, the controller 01 is specifically configured to:
sending a control instruction to the three-phase bridge arm 03 and the power supply 02, so as to utilize the voltage pulse with the maintenance time taking the preset minimum time as a starting point, the preset time period as a step length and the preset maximum time as an end point, sequentially utilizing the sampling circuit 04 to measure the positive current and the reverse current when the two phase voltage output ends of the motor M are conducted until the positive current or the reverse current reaches the preset current, and recording the maintenance time corresponding to the current voltage pulse as the shortest injection time to obtain three shortest injection times; and comparing the three shortest injection times, and determining the shortest injection time as the minimum turn-on time.
In some specific embodiments, the preset maximum time is determined according to the preset current, the inductance of the motor M, and the bus voltage value.
In some specific embodiments, the controller 01 is specifically configured to:
the initial position of the rotor of the motor M is calculated according to the following formula:
I current1 ＝I UV -I VU ；
I current2 ＝I VW -I WV ；
I current3 ＝I WU -I UW ；
wherein, three phase voltage output ends of the motor M are respectively a U end, a V end and a W end, I UV And I VU Positive and reverse currents, I, at the U and V terminals, respectively VW And I WV Positive and reverse currents, I, at terminals V and W, respectively WU And I UW Positive and negative currents at the W and U terminals, respectively, and θ is the rotor initial position.
In some specific embodiments, the controller 01 is specifically configured to: the positive current of the motor M when the current two phase voltage output ends are conducted is measured, and then the reverse current of the motor M when the current two phase voltage output ends are conducted is measured.
In some specific embodiments, the controller 01 is further specifically configured to: and disconnecting the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm to release the stored energy of the inductance of the motor MM.
According to the detection device in the embodiment of the application, when each sampling current is obtained, voltage pulses are injected into the two conducted phase voltage output ends at the minimum opening time, then the voltage pulses are cut off, a current loop between the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm and the motor inductor is established, the current in the current loop is used as the current to be sampled, and the current can be kept in the current loop for a long time, so that the requirement on the sampling rate of hardware is low, the influence of the hardware with a high sampling rate on the noise of detection is avoided, and the hardware cost in the implementation of the method is reduced.
Correspondingly, this application embodiment still discloses a motor assembly, includes: a device for detecting the initial position of the rotor of an electric machine according to the above embodiments;
the content of the detection device for the initial position of the motor rotor in this embodiment may refer to the specific description in the above embodiments, and is not described herein again.
The motor assembly in this embodiment has the same technical effect as the detection device for the initial position of the motor rotor in the above embodiments, and details are not repeated here.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The method, the system and the related components for detecting the initial position of the motor rotor provided by the invention are described in detail above, a specific example is applied in the text to explain the principle and the implementation mode of the invention, and the description of the above embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (10)
1. A method for detecting an initial position of a motor rotor is characterized by comprising the following steps:
measuring positive current and reverse current when each two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents; calculating the initial position of the rotor of the motor by using the six sampling currents;
the process of measuring the positive current or the reverse current when every two phase voltage output ends of the motor are conducted according to the minimum turn-on time comprises the following steps:
closing an upper half bridge arm of a first phase bridge arm and a lower half bridge arm of a second phase bridge arm, injecting a voltage pulse for maintaining the minimum switching time, then disconnecting the lower half bridge arm of the second phase bridge arm, closing the upper half bridge arm of the second phase bridge arm, and sampling a current circulation passing through the upper half bridge arm of the second phase bridge arm;
two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
2. The method according to claim 1, wherein before the measuring positive current and reverse current at the time of conduction between every two phase voltage output terminals of the motor according to the minimum on-time to obtain six sampling currents, the method further comprises:
determining the minimum on-time of the motor.
3. The detection method according to claim 2, wherein the process of determining the minimum on-time of the motor comprises:
sequentially measuring positive current and reverse current when the two phase voltage output ends of the motor are conducted by using voltage pulses with the maintenance time taking a preset minimum time as a starting point, a preset time period as a step length and a preset maximum time as an end point until the positive current or the reverse current reaches a preset current, and recording the maintenance time corresponding to the current voltage pulse as the shortest injection time to obtain three shortest injection times;
and comparing the three shortest injection times, and determining the shortest injection time as the minimum on-time of the motor.
4. The method according to claim 3, wherein the predetermined maximum time is determined according to the predetermined current, the inductance of the motor and a bus voltage value.
5. The method according to any one of claims 1 to 4, wherein the step of calculating an initial position of a rotor of the motor by using six of the sampled currents comprises:
calculating the initial position of the rotor of the motor according to the following formula:
I current1 ＝I UV -I VU ；
I current2 ＝I VW -I WV ；
I current3 ＝I WU -I UW ；
wherein, three phase voltage output ends of the motor are respectively a U end, a V end and a W end, I UV And I VU Positive and reverse currents, I, of the U and V terminals, respectively VW And I WV Positive and reverse currents, I, of the V and W terminals, respectively WU And I UW Positive and reverse currents of the W terminal and the U terminal, respectively, and θ is the rotor initial position.
6. The method according to claim 5, wherein the step of measuring the positive current and the reverse current when conducting between each two phase voltage output terminals of the motor comprises:
the method comprises the steps of firstly measuring positive currents when current two phase voltage output ends of the motor are conducted, and then measuring reverse currents when the current two phase voltage output ends are conducted.
7. The method of claim 6, wherein the step of measuring the positive current or the reverse current when conducting between each two phase voltage output terminals of the motor according to the minimum on-time further comprises:
and disconnecting the upper half bridge arm of the first phase bridge arm and the upper half bridge arm of the second phase bridge arm to release the inductive energy storage of the motor.
8. A system for detecting an initial position of a rotor of an electric machine, comprising:
the current measuring module is used for measuring positive current and reverse current when each two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents;
the calculation module is used for calculating the initial position of the rotor of the motor by using the six sampling currents;
wherein, the current measurement module includes first action unit, second action unit and sampling unit, wherein:
the first action unit closes an upper half bridge arm of the first phase bridge arm and a lower half bridge arm of the second phase bridge arm and injects a voltage pulse for maintaining the minimum turn-on time; then the second action unit disconnects the lower half bridge arm of the second phase bridge arm and then closes the upper half bridge arm of the second phase bridge arm, and the sampling unit samples the current circulation passing through the upper half bridge arm of the second phase bridge arm;
two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel, the midpoint of the first phase bridge arm and the midpoint of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
9. A device for detecting the initial position of a motor rotor is characterized by comprising:
the system comprises a controller, a power supply, a three-phase bridge arm and a sampling circuit, wherein the three-phase bridge arm is connected with the power supply and a motor; wherein,
the controller measures positive current and reverse current when each two phase voltage output ends of the motor are conducted according to the minimum opening time to obtain six sampling currents; calculating the initial position of the rotor of the motor by using the six sampling currents;
the process that the controller measures the positive current or the reverse current when every two phase voltage output ends of the motor are conducted according to the minimum opening time comprises the following steps:
sending a control instruction to the three-phase bridge arms and the power supply to close an upper half bridge arm of a first-phase bridge arm and a lower half bridge arm of a second-phase bridge arm and inject a voltage pulse for maintaining the minimum on-time, then disconnecting the lower half bridge arm of the second-phase bridge arm and then closing the upper half bridge arm of the second-phase bridge arm; acquiring the sampling current sent by the sampling circuit after sampling the current circulation passing through the upper half bridge arm of the second phase bridge arm;
the first phase bridge arm and the second phase bridge arm are any two-phase bridge arms in the three-phase bridge arms, two ends of the first phase bridge arm and two ends of the second phase bridge arm are connected in parallel to the output end of the power supply, the middle point of the first phase bridge arm and the middle point of the second phase bridge arm are respectively connected with two current phase voltage output ends, and the current circulating current is used as the positive current or the reverse current corresponding to the current voltage pulse.
10. An electric machine combination, comprising:
a detecting device of an initial position of a rotor of an electric machine according to claim 9;
and the motor is connected with the detection device.
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