CN114094902A - Method for monitoring commutation position of brushless direct current motor - Google Patents

Method for monitoring commutation position of brushless direct current motor Download PDF

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CN114094902A
CN114094902A CN202111375074.XA CN202111375074A CN114094902A CN 114094902 A CN114094902 A CN 114094902A CN 202111375074 A CN202111375074 A CN 202111375074A CN 114094902 A CN114094902 A CN 114094902A
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commutation
motor
commutation position
phase
loop control
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李娜
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Nanjing Linghua Microelectronics Technology Co ltd
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Nanjing Linghua Microelectronics Technology Co ltd
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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
    • 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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/08—Arrangements for controlling the speed or torque of a single motor
    • 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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/12—Monitoring commutation; Providing indication of commutation failure

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  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

The invention discloses a method for monitoring the commutation position of a brushless DC motor, which comprises the following steps: judging the optimal commutation position of the motor, calculating to obtain the ideal commutation position under the two conditions of ideal square waves and offset angles, and performing simulation analysis; after the ideal commutation phase is obtained, calculating and analyzing a commutation phase position open-loop control method, and performing open-loop correction on commutation position errors of the high-speed motor; and analyzing the relation between the virtual neutral point voltage integral and the commutation position, and performing closed-loop control on the commutation position. The invention solves the problem that the motor operation is unstable due to the fact that the commutation position of the existing motor cannot be accurately judged.

Description

Method for monitoring commutation position of brushless direct current motor
Technical Field
The invention relates to the technical field of motor control, in particular to a method for monitoring a commutation position of a brushless direct current motor.
Background
When the PMSM is driven by the square waves, the running characteristics of the motor have a close relation with a phase commutation position, and an undesirable commutation position can cause reduction of electromagnetic torque and increase of current harmonic waves. In the control without a position sensor, the actual commutation position deviates from the given commutation position due to terminal voltage detection filtering, software and hardware delay and the like. High speed motors are more sensitive to such commutation position errors due to the extremely short commutation periods. Therefore, controlling the motor to accurately switch the phase at the optimal position is very important for stable operation of the motor.
Disclosure of Invention
Therefore, the invention provides a method for monitoring the commutation position of a brushless direct current motor, which aims to solve the problem that the operation of the motor is unstable due to the fact that the commutation position of the existing motor cannot be accurately judged.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention discloses a method for monitoring the commutation position of a brushless DC motor, which comprises the following steps:
judging the optimal commutation position of the motor, calculating to obtain the ideal commutation position under the two conditions of ideal square waves and offset angles, and performing simulation analysis;
after the ideal commutation phase is obtained, calculating and analyzing a commutation phase position open-loop control method, and performing open-loop correction on commutation position errors of the high-speed motor;
and analyzing the relation between the virtual neutral point voltage integral and the commutation position, and performing closed-loop control on the commutation position.
Further, the optimal commutation position of the motor comprises calculating the commutation position both in the case of an ideal square wave, where commutation of the motor 30 degrees after the back emf zero crossing will result in the maximum battery torque output with constant current, and in the presence of a commutation offset angle δ.
Further, when the phase change offset angle delta is smaller than 0, the motor advances the phase change, when the delta is larger than 0, the motor lags the phase change, and when the motor lags the phase change, the influence caused by the line back electromotive force relatively advances; when the motor is in advance phase-changing, the relative delay of the influence caused by the back electromotive force of the wire is calculated according to the following formula,
Figure BDA0003359591400000021
the ideal commutation position of the motor can be obtained off-line from the numerical solution of delta.
Further, after the optimal commutation position of the motor is determined, simulation analysis is carried out, the influence generated by leading commutation and lagging commutation is analyzed and verified, and whether the optimal commutation position meets the requirement of the optimal commutation position is judged.
Further, the open loop control method for the commutation positionIn the method, the source of phase change position error is firstly determined by time delay
Figure BDA0003359591400000022
Compensating in an open-loop compensation mode, ensuring the stability of a commutation switching process, and establishing a commutation position open-loop control simulation model for simulation analysis.
Furthermore, in the process of determining the source of the commutation position error, the high-speed motor position-free sensor controls commutation by detecting the zero crossing point of the voltage of a non-conducting phase end, because the waveform of the voltage of the non-conducting phase end can be interfered by commutation and current ripple waves, filtering is required, and the lag angle is increased along with the increase of the rotating speed of the motor, so that errors can be caused, and the motor operation is influenced.
Further, the time delay
Figure BDA0003359591400000023
The open loop compensation mode of the degree is as follows: delaying the counter electromotive force zero crossing point at 0 degree by 90 degrees to generate the phase change signal of the n +1 th beat correspondingly, and the original nth beat is triggered by delaying the last zero crossing event by 90 degrees, and at the moment, advancing the lagging commutation position to 90 degrees, and at the filtered zero crossing point thetanTime delay
Figure BDA0003359591400000031
To achieve when
Figure BDA0003359591400000032
Error compensation at greater than 30 degrees.
Further, closed-loop control is carried out based on the virtual neutral point voltage integral and the phase change position relation, the open-loop control of the phase change position calculates the filtering phase shift and the software and hardware delay corresponding to different rotating speeds through the parameters of a filtering circuit and experiments, in the off-line calculation mode, the phase shift calculation only considers the fundamental wave of the back electromotive force, and the phase shift has an error with the actual zero crossing point; when the filter circuit changes, an error phase shift angle is calculated; the measurement of software and hardware delays and numerical calculations also cause deviations. However, in the sensorless method of externally connecting a virtual neutral point, the waveform of the neutral point voltage has a fixed relationship with the actual commutation position of the motor, and the influence of these deviations cannot be suppressed by the open-loop control method, and the deviations can be suppressed by the on-line closed-loop control method based on this relationship.
Furthermore, in the relationship between the virtual neutral point voltage integral and the commutation position, U in different circuit states is analyzed according to the commutation offset angle delta of 0, namely, the commutation time delayed by 30 degrees and the commutation offset angle not 0, namely, the motor leads or lags the commutation timesm。
Furthermore, after the commutation position is determined by a closed-loop control method, analysis and simulation are carried out, and the optimal commutation position and commutation method are determined.
The invention has the following advantages:
the invention discloses a method for monitoring a commutation position of a brushless direct current motor, which analyzes the optimal commutation position of the motor to obtain an optimal commutation position off-line searching method for controlling the average value of d-axis current to be 0; secondly, in order to make the motor accurately commutate at the optimal position, the compensation of the commutation position error of the high-speed motor is studied
Figure BDA0003359591400000033
An open loop correction method; and finally, analyzing the relation between the neutral point voltage and the commutation position, and analyzing and simulating the commutation position closed-loop control method. In a reversing position closed-loop control system, the condition that the motor can accurately change the phase at a desired position is determined, and the running stability of the motor is ensured.
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 should be apparent that the drawings in the following description are merely exemplary and that other implementation drawings may be derived from the drawings provided to one of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
FIG. 1 is a schematic diagram of phase currents during leading commutation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of phase currents during a hysteretic phase change provided by an embodiment of the present invention;
FIG. 3 is a waveform diagram of BUCK inductor current and d-axis current at different offset angles δ according to an embodiment of the present invention;
FIG. 4 is a graph of phase current, electromagnetic torque waveforms for lead, lag and phase inversion at optimal positions, as provided by an embodiment of the present invention;
fig. 5 is a circuit diagram of a terminal voltage filter according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an embodiment of the present invention
Figure BDA0003359591400000041
The compensation method is an electromotive force schematic diagram;
FIG. 7 is a schematic diagram of an embodiment of the present invention
Figure BDA0003359591400000042
The compensation method is an electromotive force schematic diagram;
FIG. 8 is a schematic diagram of an embodiment of the present invention
Figure BDA0003359591400000043
A compensation mode control block diagram;
FIG. 9 is a diagram of a commutation position open-loop control simulation model provided in an embodiment of the present invention;
FIG. 10 is a waveform diagram of phase current, delay angle, and commutation signals provided by an embodiment of the present invention;
FIG. 11 is a schematic diagram of an embodiment of the present invention
Figure BDA0003359591400000051
Schematic diagram of mode switching process;
fig. 12 is a schematic diagram of a commutation position closed-loop control topology based on virtual neutral point voltage according to an embodiment of the present invention;
FIG. 13 is a schematic diagram illustrating a circuit state of a non-commutation region according to an embodiment of the present invention;
FIG. 14 is a schematic diagram illustrating a circuit state of a commutation region according to an embodiment of the present invention;
fig. 15 shows U where δ is 0 according to an embodiment of the present inventionsmA waveform diagram;
FIG. 16 is a circuit diagram illustrating reverse freewheeling in accordance with an embodiment of the present invention;
FIG. 17 shows U in the advanced phase-change operation according to an embodiment of the present inventionsmA schematic diagram;
FIG. 18 shows U during the lagging phase transition according to the embodiment of the present inventionsmA schematic diagram;
FIG. 19 is a block diagram of a commutation position closed loop control system provided by an embodiment of the invention;
FIG. 20 is a schematic diagram of a neutral point voltage integral difference closed-loop control model according to an embodiment of the present invention;
FIG. 21 is a graph of a virtual neutral voltage waveform for different commutation positions provided by an embodiment of the present invention;
FIG. 22 is a graph illustrating the response of open-loop and closed-loop control of commutation position to a position error disturbance, according to an embodiment of the present invention.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. 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.
Example 1
The embodiment discloses a method for monitoring the commutation position of a brushless direct current motor, which comprises the steps of determining the optimal commutation position of the motor; the optimal commutation position when the current is at the ideal square wave,
the control system drives the direct current brushless motor by using square wave current, delta is set as the angle difference between the actual phase change position and the delayed 30-degree commutation position, the phase change is called as lag phase change when delta is larger than 0, and the phase change is called as lead phase change when delta is smaller than zero. Taking the conduction of the switching tube a + b-as an example, the conduction region is ω t epsilon (7 pi/6 + δ,3 pi/2), and according to the electromagnetic torque formula of the motor, the average electromagnetic torque of the motor in a commutation period when the rotating speed is stable can be obtained
Figure BDA0003359591400000061
Order to
θ＝ωt (2)
According to the basic principle formula of the motor, the method can obtain
Figure BDA0003359591400000062
When the driving current is an ideal square wave, there are
ia(θ)＝-ib(θ)＝I,ic(θ)＝0 (4)
Can be substituted to obtain
Figure BDA0003359591400000071
From this equation, when the value of δ is 0, equation 5 will obtain the maximum value
Figure BDA0003359591400000072
So for the ideal square wave current case, commutation of the motor at 30 degrees after the back emf zero crossing will cause the maximum electromagnetic torque to be output with the current unchanged.
Due to the phase-change follow current caused by the phase inductance of the motor and the disturbance of the line back electromotive force, the actual phase current cannot be an ideal square wave, and the actual waveform of the current is shown in fig. 2-7. At this time, the commutation position for enabling the motor to output the maximum torque is no longer 30 degrees, and the optimal commutation position for enabling the motor to output the maximum torque current ratio needs to be searched again.
On the basis of a control mode steady-state current model, when a commutation offset angle delta is considered, in a region where ω t belongs to (7 pi/6 + delta, 3 pi/2 + delta), if a conduction region steady-state current expression when transient components are ignored is considered:
Figure BDA0003359591400000073
at this time, the current waveforms when delta is less than 0 and delta is greater than 0, namely the motor leads and lags the phase conversion, can be respectively drawn. As shown in fig. 1 and 2.
It can be seen from the figure that the influence of the line back emf is relatively advanced when the motor lags and commutates; when the motor is in phase-changing in advance, the influence caused by the back electromotive force of the wire is relatively delayed. The commutation position of the motor determines the distortion degree of the current waveform, influences the content of current harmonics, and if the deviation delta is too large, a current peak is caused, which is more obvious in the process of lagging commutation and aggravates the pulsation of the electromagnetic torque.
Observing equation 7, it can be seen that different rotation speeds correspond to different bus voltages and motor impedance angles, so the actual phase current waveform will be related to the rotation speed, meaning that there will be different ideal commutation positions when the motor operates at different rotation speeds.
Known PARK coordinate transformation
Figure BDA0003359591400000081
As can be seen by comparing equation 8, the integrand in equation 3 is in the same form as the q-axis component of the stator current, i.e., the instantaneous output torque is proportional to the q-axis current. Due to the fact that
Figure BDA0003359591400000082
As can be seen from equation 9, the smaller the d-axis current is, the larger the q-axis current is when the current vector magnitude is constant. Therefore, in order to maximize the average output torque under the same current amplitude, the d-axis current time should be 0 as the control target. For sine wave vector control, three-phase current vectors are respectively modulated in a calculation period, so that the average value of d-axis current in a carrier period is 0; in the square wave control of the method, under the condition that the average current is not changed, the d-axis current is only related to the phase change position, and the phase change position can only be adjusted when the next phase change comes after the current phase change is finished, so that the average value of the d-axis current in a phase change period is 0 at this time as the control target.
At this time have
Figure BDA0003359591400000083
And solving the numerical solution of the delta to obtain the ideal commutation position of the motor off line. It should be noted that the off-line searching method for the optimal commutation position provided by the present invention is based on the premise that the motor parameters are accurate, and a certain deviation may be caused by the actual parameter change of the motor during the actual operation of the motor.
And (4) carrying out simulation analysis, adding an input of an offset angle delta into the position-sensorless module, and simultaneously taking the integral of a d-axis component of the stator current in a commutation period. The BUCK inductor current waveform was observed with a given rotation speed of 100000r/min and a load of 0.01Nm, with a given delta angle ranging from-20 degrees to 20 degrees over a period of 0.035s to 0.055s, as shown in FIG. 3.
In this process, the load torque is kept constant at 0.01Nm, the rotational speed is kept constant, and the output average electromagnetic torque is constant. The inductor current is an average value of the output phase current, and a smaller inductor current means a smaller current required to generate the same electromagnetic torque, and the commutation position is more desirable.
As can be seen from FIG. 3, with offsetThe phase shift angle is gradually changed from-20 degrees to 20 degrees, the inductive current is firstly decreased and then increased, the minimum value is 5.48A and appears at the position of 0.047s, at the moment, delta is-4 degrees, the output average current is not minimum when delta is 0 degrees in the control mode, and the time delay of 30-degree phase change is not the optimal phase change position any more; and idTime to zero average 0.04665s, corresponding delta-3.3 degrees, and inductor current iLTaking the time of the minimum value close to indicate that i can be in the phase change perioddThe average value of 0 is the determined optimal commutation position approximated by the control target. Torque coefficient K at this timeT(Nm/A) is calculated from the load torque and the output average current
Figure BDA0003359591400000091
Fig. 4 shows waveforms of phase current and electromagnetic torque when the motor is advanced by 10 degrees and delayed by 10 degrees and phase-shifted at the optimum position.
As can be seen from fig. 4, the average values of the d-axis currents at the leading and lagging commutation will be less than 0 and greater than 0, respectively; FIG. 4(b), in which the phase current distortion level and harmonic content are higher than those in the optimal commutation positions, illustrates that larger lead and lag angles result in more severe current waveform distortion, cause larger harmonics, and have a greater effect on lagging commutation than leading commutation; the torque ripple peak values in fig. 4(a) and (c) are 0.006Nm and 0.008Nm, respectively, which are higher than 0.004Nm at the time of the optimum commutation, and it is explained that the undesirable commutation position affects not only the magnitude of the output torque but also the torque ripple. Therefore, it is important to control the motor to accurately change the phase at the optimal commutation position.
Example 2
The embodiment discloses a commutation position open-loop control method, firstly determining a commutation position error source, controlling commutation by detecting a zero crossing point of a non-conducting phase end voltage (back electromotive force) by a high-speed motor position-free sensor, wherein filtering is required because the waveform of the end voltage is interfered by commutation, current ripple and the like, and a typical end voltage filtering circuit is shown in fig. 5.
The phase shift due to the low-pass filter circuit causes the actually detected terminal voltage to lag behind the actual value by the lag angle
Figure BDA0003359591400000101
As can be seen from equation 12, the hysteresis angle will increase as the motor speed increases. In addition, in actual operation, software computing period and delay T exist in the processorsThe signal transmission of the hardware circuit also has a time delay ThThese factors all contribute to inaccuracies in the detected zero-crossing of back emf with a total lag angle of
Figure BDA0003359591400000111
If the lag angle is not compensated, the phase change will be inaccurate, and the motor operation will be affected. And the commutation error is more obvious for a high-speed motor with short commutation period.
Due to terminal voltage filter circuit parameter Rx、RyAnd software hardware delay Ts、ThCan be measured by an off-line method, so that the delay angle corresponding to each rotating speed when the motor operates
Figure BDA0003359591400000112
Can be obtained by calculation.
When the commutation offset angle delta is 0, to compensate for the lag angle at the zero crossing
Figure BDA0003359591400000113
The actual reversing position needs to be advanced
Figure BDA0003359591400000114
Equivalent to changing the delay time of 30 degrees into the delay time
Figure BDA0003359591400000115
As shown in fig. 6.
The pre-filtered a counter emf crosses zero at 0 degrees in fig. 6, which should produce its corresponding n-th commutation phase signal at the ideal commutation position (30 degrees). And the filtered back EMF signal is at θnZero crossing, and if no compensation is applied, the commutation signal is at thetanOccurs at +30 degrees, resulting in a lag in commutation. Changing the delay angle to
Figure BDA0003359591400000116
The motor will then commutate at the desired position.
Because the change range of the rotating speed of the high-speed motor is very large, the rotating speed is increased, and the rotating speed is calculated
Figure BDA0003359591400000117
Often greater than 30 degrees or even greater than 90 degrees, as shown in fig. 6
Figure BDA0003359591400000118
The compensation method of (3) will no longer be applicable. To solve this problem, compensation is made in a range greater than 30 degrees
Figure BDA0003359591400000119
The 30-degree delay method can be changed into a 90-degree delay method, and compensation is carried out on the basis of 90-degree delay
Figure BDA00033595914000001110
As shown in fig. 7.
In fig. 7, the back emf zero-crossing at 0 degrees is delayed by 90 degrees, corresponding to the commutation signal producing beat n +1, with the original beat n being triggered by the last zero-crossing event being delayed by 90 degrees. At this time, to advance the retarded commutation position to 90 degrees, at the filtered zero crossing point θnTime delay
Figure BDA00033595914000001111
And (4) degree. Thus it is realized that
Figure BDA0003359591400000121
Error compensation at greater than 30 degreesThe same principle can be obtained
Figure BDA0003359591400000122
At greater than 90 degrees
Figure BDA0003359591400000123
A compensation method.
The block diagram of the open loop control system for the reversing position is shown in fig. 8. Used when the motor is running at low speed
Figure BDA0003359591400000124
By raising to a certain speed and switching to
Figure BDA0003359591400000125
The method. In the rotation speed range with the lag angle close to 30 degrees, the two modes are frequently switched, and an angle hysteresis loop theta is added during mode judgmentt. When the given offset angle delta is not 0, the given offset angle delta and the given offset angle delta can be added into a delay angle calculation part together to realize open-loop control of the reversing position.
It should be noted that the two ways of handover procedure need to be in the correct order. To get from
Figure BDA0003359591400000126
Switch to
Figure BDA0003359591400000127
As an example, when calculated
Figure BDA0003359591400000128
Gradually increase to more than 30+ thetatThen, the next back electromotive force zero-crossing event should be waited for first, and then when the next zero-crossing occurs, the delay angle is switched to
Figure BDA0003359591400000129
And finally, when the time delay is finished, the phase change signal generating the nth beat is changed into the phase change signal generating the (n + 1) th beat. If the time delay angle and the beat number are switched without waiting for the generation of a new zero-crossing event, one beat is missed in the switching process, so that the switching process is causedIs unstable.
Simulation analysis was performed, and a commutation position open-loop control simulation model was created as shown in fig. 9(a), (b), and (c). Under the condition of 10 ten thousand rotation speed and 0.01Nm load, when delta is given to be 0 degree,
Figure BDA00033595914000001210
the open-loop control waveform of the delay method is shown in fig. 10 and 11, in which the hysteresis width of the switching angle is set to 9 degrees.
As can be seen from fig. 10 and 11, the delay angle is 30 degrees at a rotation speed of 0, and as the rotation speed increases, the delay angle increases
Figure BDA00033595914000001211
Decrease until less than 0, and then the temperature of the liquid can not exceed 30 DEG
Figure BDA00033595914000001212
And compensating, wherein the phase change position of the motor is gradually lagged, and the current waveform is distorted.
When in use
Figure BDA00033595914000001213
Increasing the temperature to 39 degrees to meet the hysteresis switching condition, and switching the delay angle to
Figure BDA00033595914000001214
At the moment, the motor has accurate phase change, and the current waveform distortion is reduced.
Example 3
The embodiment discloses a commutation position closed-loop control method based on virtual neutral point voltage integration
And the phase-change position open-loop control calculates the filtering phase shift and software and hardware delay corresponding to different rotating speeds through filter circuit parameters and experiments. In the off-line calculation mode, the phase shift calculation only considers the fundamental wave of the back electromotive force, and the phase shift has an error with the actual zero crossing point; when the filter circuit changes, an error phase shift angle is calculated; the measurement of software and hardware delays and numerical calculations also cause deviations. And the open loop control cannot suppress the influence of these deviations.
In the sensorless approach of externally connecting a virtual neutral point, the waveform of the neutral point voltage has a fixed relationship with the actual commutation position of the motor, and based on this relationship, the above deviation can be suppressed by an online closed-loop control method.
The relationship between the voltage of the virtual neutral point and the commutation position leads out the middle point of the output voltage of the BUCK circuit, and the voltage between the middle point and the virtual neutral point is measured, wherein the topology is shown in figure 12.
The analysis in the foregoing examples shows
Figure BDA0003359591400000131
Then
Figure BDA0003359591400000132
To illustrate the neutral point voltage usmRelationship with commutation position of the motor, u in the following for different circuit statessmAnd (6) carrying out analysis.
(1) The circuit state in the non-commutation region ω t ∈ (7 π/6+ ω Δ t,3 π/2) is shown in FIG. 13, with the commutation shift angle δ being 0, i.e., 30 degrees of commutation delay, taking the switching state of a + b-as an example.
The c phase is cut off at the moment, and the voltage of the three-phase terminal at the moment can be obtained
uag＝Ud,ubg＝0,ucg＝ec+ung (16)
The voltage equation at this time is
Figure BDA0003359591400000141
From equation 17, the
Figure BDA0003359591400000142
It is known that
ea+eb+ec＝0 (19)
By substituting 16, 18, 19 for 15
Figure BDA0003359591400000143
The circuit state is shown in FIG. 14 when ω t ∈ (3 π/2,3 π/2+ ω Δ t) commutates from a + b-to a + c-.
At this time have
uag＝ubg,ucg＝0 (21)
Substituted by formula 15
Figure BDA0003359591400000151
Similarly, U in other switch states can be deducedsmExpression, plotting U at an offset angle δ of 0smThe waveform is shown in fig. 15.
As can be seen from the figure, UsmThe signal is a periodic signal with the frequency three times that of the motor, and the periodic signal sequentially crosses the x axis from the positive direction and the negative direction; when delta is 0, in the non-commutation area UsmThe waveform coincides with the counter electromotive force; in the commutation zone, when the bridge arm is switched to be the lower bridge arm, U sm1/6 for bus voltage, when switching arm to upper arm, UsmIs-1/6 for bus voltage.
(2) The commutation offset angle is not 0, i.e. when the motor is in advance or in retard commutation, in the commutation region and the non-commutation region UsmIs the same as when delta is 0, but a new non-conducting continuous flow region exists.
Taking the phase change process from a + b-to a + c-during the advanced phase change as an example, the phase change of the lower bridge arm is performed at the time, and when the phase change is finished, the ω t belongs to (3 π/2+ ω Δ t,3 π/2+ δ + + ω Δ t)1) Wherein Δ t1For the duration of the interval, now
Figure BDA0003359591400000152
Figure BDA0003359591400000153
Since the motor is advanced by phase change, at this time ebSmaller than that when delta is equal to 0, when
Figure BDA0003359591400000161
When it is established, UbgAnd is less than zero, resulting in a current freewheeling in the reverse direction from the negative terminal of the bus to phase b through the diode, and the equivalent circuit is shown in fig. 16.
At this time, the three-phase terminal voltage is
ubg＝ucg＝Ud,uag＝0 (26)
Substituted by formula 15 to obtain
Figure BDA0003359591400000162
When the upper bridge arm changes phase, UsmThe sign will change.
In the same way, the lagging commutation time U can be obtainedsmIs described in (1). U during leading and lagging phase changesmThe waveforms are shown in fig. 17 and 18.
In the commutation position closed-loop control method, as can be seen from the observation of fig. 15, 17 and 18, the shadow areas of the positive crossing periods and the negative crossing periods in the figures are related to the commutation positions.
The variable of the horizontal axis is changed into t, the area relation of the formula is unchanged, and the area can be calculated by integrating the time t. Taking two commutation periods of a + b-conduction and a + c-conduction as an example, in the positive crossing period of omega t epsilon (7 pi/6 + delta, 3 pi/2 + delta), a new free-wheeling area delta t after the commutation period is not considered1Has a small influence of the area of the blue shadow of
Figure BDA0003359591400000171
In the positive crossing period of omega t epsilon (3 pi/2 + delta, 11 pi/6 + delta), the area of the yellow shadow is
Figure BDA0003359591400000172
As can be seen from equations 28, 29 and FIGS. 17, 18, S+Decreases with increasing offset angle delta, and S-Increasing with increasing offset angle delta. Leading phase change time S-Will be gradually greater than S+Lagging commutation time S-Will be less than S+The difference between the two can be expressed as
Figure BDA0003359591400000173
Is simple and easy to obtain
Figure BDA0003359591400000174
The calculation formula of delta t is given by the formula 2-35
Figure BDA0003359591400000175
Wherein the initial value of current can be an average value of the inductor current.
The first term on the right side of equation 31 equals to two periods U before and aftersmThe second term is equivalent to U in the integral difference of the non-commutation areasmIntegral difference in commutation region, Δ s is UsmIntegration over the entire commutation region.
As can be seen from equation 31, there is a definite relationship between the difference of the neutral point voltage integrals of the positive and negative ride-through periods and the commutation offset angle. If the voltage of the neutral point is detected to obtain deltas when the motor runs, the commutation position at the moment can be known; similarly, if it is desired to commutate the motor at δ, this can be achieved by controlling the difference of the positive and negative cross-over periodic neutral voltage integrals corresponding to that δ.
In order to calculate Δ s for a given δ, equation 31 is divided into two parts,
Figure BDA0003359591400000181
S1can be obtained by means of off-line calculation, and S2The motor current, bus voltage and rotational speed calculation need to be detected in real time. And when S is ignored2And given that delta is 0, delta s is also 0, which shows that the voltage integrals of the neutral points in the front and the back two periods are approximately equal when the phase change is carried out by delaying 30 degrees.
Thus, a block diagram of a commutation position closed loop control system can be constructed, as shown in fig. 19.
The system calculates the corresponding S according to the formula 31 for any given commutation offset angle delta1Calculating integral S of neutral point voltage in a phase conversion area through bus voltage, inductive current and current rotating speed2The sum of which is given as the integral difference
Figure BDA0003359591400000191
And detecting the difference value deltas of the neutral point voltage integrals of the motor in the front phase-changing period and the rear phase-changing period, taking the difference value deltas as a controlled variable, and performing closed-loop control by using a PI controller to ensure that the motor accurately changes the phase at a given offset angle delta.
And (3) carrying out simulation analysis, and establishing a neutral point voltage integral difference value closed-loop control module on the basis of the original model under the condition of giving 10 kilo-revolutions and 0.01Nm load, as shown in figure 20.
In fig. 20, S is calculated from a predetermined commutation offset angle δ, and the inductance current, the bus voltage, and the like of the motor1、S2After adding, comparing with the detected actual neutral point voltage difference value of the positive and negative crossing periods, and outputting a delay angle by the PI controller
Figure BDA0003359591400000192
Are added together to
Figure BDA0003359591400000193
In the delay module, closed-loop control is realized; the neutral point voltage detection part stores the integral difference value of the current period and the previous commutation period according to the crossing direction of the current period at the initial time of each commutation; PI controller parameter KpIs 40, KiAnd the output amplitude is 700 degrees, the output amplitude is 15 degrees, and the output is started after the rotating speed is stabilized.
The virtual neutral point voltage waveforms of the motor at different commutation positions are shown in figure 21. As can be seen from FIG. 21, UsmIs related to commutation position, as shown in (b), when commutation is performed at 0 degrees, U is in a period crossing the x-axis positively and in a period crossing the x-axis negativelysmThe waveforms of (1) are symmetrical, and the integrated values thereof in one period are approximately equal; whereas the leading and lagging commutation cases in graphs (a) (c) will result in U, respectivelysmThe conclusion given by equation 31 is verified when the integral over the positive crossing period is less than or greater than the negative crossing period.
To illustrate the on-line error correction effect of the commutation position closed-loop control, given δ of-3.3 degrees, an artificially given commutation error leading 10 degrees is added at 0.03s, at which the commutation positions of the open-loop control and closed-loop control are compared, as shown in fig. 22.
As can be seen from fig. 22(b), the output delay angle of the open-loop control does not change when the position error disturbance is received, and the actual commutation position will lead the given commutation position, which means that it can only compensate the pre-calculated phase shift, but cannot correct other position errors online; in fig. 22(a), after receiving the disturbance, the closed-loop control system determines the delay angle of the output compensation at this time according to the neutral point voltage integral difference, and compensates for 10 degrees of the previous phase, so that the motor recovers accurate phase commutation within 0.001s, and the goal of online correction is achieved.
The invention discloses a method for monitoring the commutation position of a brushless DC motor, which analyzes the optimal commutation position of the motor to obtain the optimal commutation position with the average value of the current of a control d shaft as 0An off-line searching method; secondly, in order to make the motor accurately commutate at the optimal position, the compensation of the commutation position error of the high-speed motor is studied
Figure BDA0003359591400000201
An open loop correction method; and finally, analyzing the relation between the neutral point voltage and the commutation position, and analyzing and simulating the commutation position closed-loop control method. In a reversing position closed-loop control system, the condition that the motor can accurately change the phase at a desired position is determined, and the running stability of the motor is ensured.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (10)

1. A method for monitoring the commutation position of a brushless DC motor is characterized by comprising the following steps:
judging the optimal commutation position of the motor, calculating to obtain the ideal commutation position under the two conditions of ideal square waves and offset angles, and performing simulation analysis;
after the ideal commutation phase is obtained, calculating and analyzing a commutation phase position open-loop control method, and performing open-loop correction on commutation position errors of the high-speed motor;
and analyzing the relation between the virtual neutral point voltage integral and the commutation position, and performing closed-loop control on the commutation position.
2. A method of monitoring commutation positions of a brushless dc motor according to claim 1, wherein the optimal commutation position of the motor comprises calculating the commutation position both in the case of an ideal square wave, where commutation 30 degrees after the zero crossing of the back emf will cause the maximum battery torque to be output with the current unchanged, and in the presence of a commutation offset angle δ.
3. The method according to claim 1, wherein when the commutation offset angle δ is smaller than 0, the motor is leading to commutation, when δ is larger than 0, the motor is lagging to commutation, and when the motor is lagging to commutation, the influence caused by the back electromotive force of the wire is relatively leading; when the motor is in phase advance and phase inversion, the relative lag of the influence caused by the line back electromotive force is calculated according to the following formula,
Figure FDA0003359591390000011
the ideal commutation position of the motor can be obtained off-line from the numerical solution of delta.
4. The method according to claim 1, wherein the optimal commutation position of the brushless dc motor is determined and then subjected to simulation analysis, and the influence of leading commutation and lagging commutation is analyzed and verified, so as to determine whether the optimal commutation position meets the requirement of the optimal commutation position.
5. The method according to claim 1, wherein the commutation position error source is first determined by delaying the commutation position error source by a delay time
Figure FDA0003359591390000012
Compensating in an open-loop compensation mode, ensuring the stability of the commutation switching process, and establishing a commutation position open-loop control simulation model for simulation analysis.
6. The method of claim 5, wherein in the step of determining the error source of commutation position, the sensorless control of the high speed motor controls commutation by detecting zero crossing of voltage at non-conducting phase, because the waveform of the voltage is interfered by commutation and ripple wave, filtering is necessary, and the lag angle increases with the increase of the motor speed, which causes error and affects the motor operation.
7. The method according to claim 5, wherein the delay time is set to a value corresponding to a commutation position of the brushless DC motor
Figure FDA0003359591390000021
The open loop compensation mode of the degree is as follows: delaying the counter electromotive force zero crossing point at 0 degree by 90 degrees to generate the phase change signal of the n +1 th beat correspondingly, and the original nth beat is triggered by delaying the last zero crossing event by 90 degrees, and at the moment, advancing the lagging commutation position to 90 degrees, and at the filtered zero crossing point thetanTime delay
Figure FDA0003359591390000022
To achieve when
Figure FDA0003359591390000023
Error compensation at greater than 30 degrees.
8. The method according to claim 1, wherein closed-loop control is performed based on the relationship between virtual neutral point voltage integral and commutation position, and open-loop control of commutation position calculates the filtering phase shift and software and hardware delay corresponding to different rotation speeds through filtering circuit parameters and experiments, and in the off-line calculation mode, the phase shift calculation only takes into account the fundamental wave of the back electromotive force, and there is an error in the phase shift from the actual zero crossing point; when the filter circuit changes, an error phase shift angle is calculated; the measurement of software and hardware delay and numerical calculation also cause deviation, and the influence of the deviation cannot be inhibited by open-loop control.
9. The method according to claim 8, wherein the virtual neutral point voltage integral and commutation position relationship is analyzed for U under different circuit conditions according to a commutation offset angle δ of 0, i.e. a commutation time delayed by 30 degrees, and a commutation offset angle other than 0, i.e. a leading or lagging commutation of the motorsm。
10. The method according to claim 1, wherein the commutation position is determined by a closed-loop control method, and then analyzed and simulated to determine the best commutation position and commutation method.
CN202111375074.XA 2021-11-17 2021-11-17 Method for monitoring commutation position of brushless direct current motor Pending CN114094902A (en)

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Publication number Priority date Publication date Assignee Title
CN106160593A (en) * 2016-07-12 2016-11-23 张前 Permanent magnetic brushless commutation method for optimizing position
CN107395072A (en) * 2017-08-31 2017-11-24 哈尔滨工程大学 A kind of method of position-sensor-free DC brushless motor phase compensation
CN112022143A (en) * 2020-08-17 2020-12-04 南京凌华微电子科技有限公司 Mobile robot monitoring system and method based on vital sign parameter analysis

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CN106160593A (en) * 2016-07-12 2016-11-23 张前 Permanent magnetic brushless commutation method for optimizing position
CN107395072A (en) * 2017-08-31 2017-11-24 哈尔滨工程大学 A kind of method of position-sensor-free DC brushless motor phase compensation
CN112022143A (en) * 2020-08-17 2020-12-04 南京凌华微电子科技有限公司 Mobile robot monitoring system and method based on vital sign parameter analysis

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