Current partition planning method for three-phase SRM based on switch type Hall position sensor

Abstract

The invention discloses a three-phase SRM current partition planning method based on a switch type Hall position sensor, which relates to the technical field of motor control, comprising: if the rotor is in a Hall sector where only one phase torque is consistent with a given motor total output torque direction, only this phase is turned on, the given current of the turned-on phase does not change with the rotor position, and the given current of the turned-on phase is determined with the goal of the sector average torque of the turned-on phase being the same as the given total torque; if the rotor is in a Hall sector where only one phase torque is opposite to the given motor total output torque direction, a high-frequency pulse current is injected into the winding of this phase, the rotor position is estimated according to the pulse peak value, so as to determine the given torque of the other two phases, and then determine the given current of the other two phases; the invention suppresses torque pulsation by estimating the rotor position in a sector where the turned-on phase torque is sensitive to the rotor position and planning the turned-on phase current curve in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a three-phase SRM current partitioning planning method based on a switch type Hall position sensor. Background Art

[0002] Switched reluctance motor (SRM) has the advantages of high reliability, large starting torque and wide speed regulation range, so it has been widely used in engineering machinery, electric vehicles and household appliances. Switch type Hall position sensor has the advantages of low cost and resistance to dust and oil, so it is often used to detect the rotor position of SRM. However, the resolution of the switch type Hall position sensor is low, and it can only detect the position where the stator salient pole of the SRM is aligned with the center of the rotor salient pole (recorded as the aligned position) and the position where the stator salient pole is aligned with the center of the rotor groove (recorded as the misaligned position).

[0003] For three-phase SRMs using switch-type Hall position sensors, during motor start-up and low-speed operation, the given current of each phase is generally planned as a square wave, and the given conduction area of ​​each phase is set to the area between the aligned position and the misaligned position of the phase. The square wave amplitude is only related to the given total output torque of the motor. This current planning method is simple and easy to implement, but the relationship between the phase torque and the rotor position of the SRM is highly nonlinear, and the torque pulsation is large when this method is used. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a three-phase SRM current partition planning method based on a switch-type Hall position sensor. The present invention suppresses torque pulsation by estimating the rotor position in the sector where the conduction phase torque is sensitive to the rotor position and planning the conduction phase current curve in real time.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a three-phase SRM current partition planning method based on a switch-type Hall position sensor, comprising:

[0006] If the rotor is in a Hall sector where only one phase torque is consistent with the given total motor output torque direction, recorded as a Class I sector, then only this phase is turned on, and the given current of the turned-on phase does not change with the rotor position. The given current of the turned-on phase is determined with the goal of making the sector average torque of the turned-on phase the same as the given total torque.

[0007] If the rotor is in a Hall sector where only one phase torque is opposite to the given total output torque of the motor, which is recorded as a Class II sector, a high-frequency pulse current is injected into this phase winding, and the rotor position is estimated based on the pulse peak value. The given torque of the other two phases is determined based on the given total torque, the estimated rotor position and the torque distribution function, and the given current of the other two phases is further determined based on the given torque of the other two phases, the estimated rotor position and the current-torque-position characteristics of the motor.

[0008] As a further improvement of the present invention, with the goal of making the average sector torque of the conducting phase equal to the given total torque, the specific steps of determining the given current of the conducting phase are as follows:

[0009] 1) Extract the torque data in a sector with the midpoint of the stator-rotor pole alignment position of the conducting phase and the midpoint of the stator pole-rotor slot alignment position of the conducting phase as the midpoint from the phase torque characteristic data of the motor, and calculate the average value of the torque data extracted when the phase current takes different values ​​within the phase current range corresponding to the torque data;

[0010] 2) Take the average value obtained as the known independent variable value, and the phase current corresponding to the average value as the known function value, and use the interpolation method to obtain the independent variables: The function value when ;

[0011] 3) As the known independent variable value, the obtained function value is taken as the known function value, and the function value when the independent variable is a given total torque is obtained by interpolation method, that is, the given current value of the conducting phase in the said Class I sector;

[0012] in, It represents the number of known data points required to obtain the conducting phase current in the Class I sector by using the interpolation method.

[0013] As a further improvement of the present invention, the high-frequency pulse current is injected by applying a high-frequency rectangular wave voltage across the two ends of the phase winding.

[0014] As a further improvement of the present invention, the high and low levels of the high-frequency rectangular wave voltage are respectively the positive and negative bus voltages.

[0015] As a further improvement of the present invention, the values ​​of the duty cycle and frequency of the high-frequency rectangular wave voltage meet the following conditions:

[0016] 1) The peak value of the high-frequency pulse current is not greater than the critical saturation current;

[0017] 2) The peak value of the high-frequency pulse current is accurately detected;

[0018] 3) Before the high-frequency rectangular wave voltage changes from a low level to a high level, the high-frequency pulse current has dropped to zero.

[0019] As a further improvement of the present invention, the formula for estimating the rotor position according to the pulse peak value is:

[0020]

[0021] in, represents the estimated rotor position; represents the peak value of the high-frequency pulse current; Indicates the DC bus voltage; and Respectively represent the period and duty cycle of the high-frequency rectangular wave voltage; and Respectively represent the inductance values ​​of the phase windings injected with high-frequency pulse current at the left and right endpoints of the Class II sector; Indicates the rotor position of the left endpoint of the Class II sector; the left endpoint of the Class II sector is the endpoint with a smaller rotor position, and the right endpoint is the endpoint with a larger rotor position.

[0022] As a further improvement of the present invention, the torque distribution function should make the commutation overlap area located in the type II sector.

[0023] As a further improvement of the present invention, the steps of obtaining the current-torque-position characteristics are as follows:

[0024] 1) Extract the curve data of each phase torque monotonically changing with the phase current from the phase torque characteristic data of the motor;

[0025] 2) When the rotor position takes different values, the corresponding curve data is taken as the known independent variable value, and the phase current value corresponding to the torque data is taken as the known function value. The independent variables are obtained by interpolation method. The function value at the time, that is, the curve data of the phase current changing with the phase torque;

[0026] 3) The obtained curve data of each phase current changing with the phase torque are summarized to obtain the current-torque-position characteristic table.

[0027] The beneficial effects of the present invention are:

[0028] The present invention realizes continuous estimation of the rotor position in the sector where the conduction phase torque is relatively sensitive to the rotor position, thereby realizing real-time planning of the conduction phase current and instantaneous torque control, and suppressing torque pulsation; in addition, based on the estimated rotor position, the rotation speed can be estimated more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the principle of an embodiment of the present invention;

[0030] Figure 2 It is a waveform diagram of the Hall signal and the SRM phase inductance in an embodiment of the present invention;

[0031] Figure 3 A family of inductance curves of phase A in an embodiment of the present invention;

[0032] Figure 4 A phase torque curve family diagram in an embodiment of the present invention;

[0033] Figure 5 For the embodiment of the present invention Figure 2 middle N s =6, the curve of phase A current changing with phase A average torque;

[0034] Figure 6 A phase current curve family in the embodiment of the present invention;

[0035] Figure 7 It is a simulation waveform diagram when the rotation speed is 500 rpm and the given total torque is 5 Nm in an embodiment of the present invention;

[0036] Figure 8 This is a simulation waveform diagram of the method using square wave current in an embodiment of the present invention when the speed is 500 rpm and the given total torque is 5 Nm;

[0037] Fig. 9 It is a simulation waveform diagram when the rotation speed is 500 rpm and the given total torque is 15 Nm in an embodiment of the present invention;

[0038] Fig.10 This is a simulation waveform diagram of the method using square wave current in an embodiment of the present invention when the speed is 500 rpm and the given total torque is 15 Nm. DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] Example

[0041] A three-phase SRM current partition planning method based on switch-type Hall position sensor is proposed. The control object is a three-phase 12 / 8-pole SRM with a bus voltage of 72 V and an asymmetric half-bridge power converter.

[0042] Depend on Figure 3 The family of phase inductance curves shown yields:

[0043] 1) When the rotor position (angle) is 240 electrical degrees, the unsaturated inductance of phase A is 1.76 mH, and when the rotor position (angle) is 300 electrical degrees, the unsaturated inductance of phase A is 0.59 mH;

[0044] 2) When the rotor position (angle) is in the range of 240~300 electrical degrees, the phase inductance curve when the A phase current is 10 A is almost the same as the inductance curve when the A phase current is 20 A;

[0045] 3) When the rotor position (angle) is in the range of 240~300 electrical degrees and the A-phase current is not greater than 20 A, the inductance is approximately a straight line.

[0046] Therefore, the embodiment of the present invention assumes that: when the rotor position (angle) is in the range of 240-300 electrical degrees and the A-phase current is not greater than 20 A, the A-phase inductance is independent of the A-phase current and is linearly related to the rotor position.

[0047] In addition, since the present invention is only used in low-speed conditions, it is assumed that: a positive bus voltage is applied to both ends of the A-phase winding so that the A-phase current i A From 0 to i pk,A ( i pk,A ≤20 A), the effects of back EMF and the voltage drop across the resistive winding on the current are negligible.

[0048] Based on the above two assumptions, if a positive bus voltage is applied across the A phase winding t rise seconds, so that the A phase current increases from 0 to i pk,A ( i pk,A ≤20 A), then when the rotor position angle is within a sector with 240 electrical degrees as the left end point and 300 electrical degrees as the right end point, the rotor position (angle) and i pk,A The relationship is

[0049]

[0050] Combination Figure 2 The relationship between the inductances of phases A and B shown in the figure is as follows: if a positive bus voltage is applied across the B phase winding t rise seconds, so that the B phase current i B From 0 to i pk,B ( i pk,B ≤20 A), then when the rotor position angle is within a sector with 0 electrical degrees as the left end point and 60 electrical degrees as the right end point, the rotor position (angle) is i pk,B The relationship is

[0051]

[0052] Combination Figure 2 The relationship between the inductances of phases A and C is shown in Figure 1. If a positive bus voltage is applied across the C phase winding, t rise seconds, so that the C phase current i C From 0 to i pk,C ( i pk,C ≤20 A), then when the rotor position angle is within a sector with 120 electrical degrees as the left end point and 180 electrical degrees as the right end point, the rotor position (angle) is i pk,C The relationship is

[0053]

[0054] based on Figure 2 The relationship between the Hall signal and the phase inductance is shown in Figure 1 As shown, according to the sector number N s Different control strategies are adopted for different values:

[0055] 1) N s =5, a high-frequency rectangular wave voltage is applied to both ends of the B-phase winding, the peak value of the corresponding high-frequency pulse current of the B-phase winding is measured, and the rotor position is estimated according to the formula, and then according to the cosine torque distribution function, as well as Figure 6 The relationship between the phase current, phase torque and rotor position shown determines the given current of phases A and C;

[0056] 2) N s =1, only phase A is conducting and the given current of phase A is constant. Figure 5 The relationship between the phase current and the sector average torque shown determines the given current of phase A;

[0057] 3) N s =3, a high-frequency rectangular wave voltage is applied to both ends of the C-phase winding, the peak value of the corresponding C-phase winding high-frequency pulse current is measured, and the rotor position is estimated according to the formula, and then according to the cosine torque distribution function, as well as Figure 6 The relationship between the phase current, phase torque and rotor position shown determines the given current of phases A and B;

[0058] 4) N s =2, only phase B is conducting and the given current of phase B is constant. Figure 5 The relationship between the phase current and the sector average torque shown determines the given current of phase B;

[0059] 5) N s =6, a high-frequency rectangular wave voltage is applied to both ends of the A-phase winding, the peak value of the corresponding A-phase winding high-frequency pulse current is measured, and the rotor position is estimated according to the formula, and then according to the cosine torque distribution function, as well as Figure 6 The relationship between the phase current, phase torque and rotor position shown determines the given current of phases B and C;

[0060] 6) N s =4, only phase C is conducting and the given current of phase C is constant. Figure 5 The relationship between the phase current and the sector average torque shown determines the C phase given current.

[0061] In the above strategy, the frequency and duty cycle of the high-frequency rectangular wave voltage are 5 kHz and 37.5% respectively, so the current rise time during the application of the high-frequency rectangular wave voltage to the phase winding is t rise is 75 us; the opening angle and overlap angle of the cosine torque distribution function are set to 5 electrical degrees and 50 electrical degrees respectively; Figure 5 The relationship between the phase current and the average torque of the sector is shown, and Figure 6 The relationships between phase current, phase torque and rotor position shown are based on Figure 4 The phase torque characteristics shown are obtained.

[0062] The method of the present invention and the method using square wave current were compared in the MATLAB / SIMULINK environment. In the simulation, the conduction phase current was controlled by hard chopping, the control frequency was 40 kHz, and the speed was 500 rpm. The simulation waveforms when the total torque was 5 Nm and 15 Nm were shown as follows: Figure 7 , Figure 8 and Fig. 9 , Fig.10 It can be seen that when the method of the present invention is adopted, the actual total torque fluctuation is small, especially under the working condition of large torque.

[0063] The torque ripple coefficient is defined as follows:

[0064]

[0065] In the formula, the maximum, minimum and average torques specifically refer to the maximum, minimum and average torques within an electrical cycle. When the total torque is given to be 5 Nm, the torque pulsation coefficient obtained by the method of the present invention is 0.54, while the torque pulsation coefficient obtained by using the square wave current is 0.57; when the total torque is given to be 15 Nm, the torque pulsation coefficient obtained by the method of the present invention is 0.3, and the torque pulsation coefficient obtained by using the square wave is 0.56. The difference in the quantitative index of the torque pulsation coefficient further illustrates the usefulness of the method of the present invention in suppressing torque pulsation.

[0066] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A three-phase SRM current partition planning method based on a switch-type Hall position sensor, characterized in that: include: If the rotor is in a Hall sector where only one phase torque is consistent with the given total motor output torque direction, recorded as a Class I sector, then only this phase is turned on, and the given current of the turned-on phase does not change with the rotor position. The given current of the turned-on phase is determined with the goal of making the sector average torque of the turned-on phase the same as the given total torque. With the goal of making the average sector torque of the conducting phase the same as the given total torque, the specific steps for determining the given current of the conducting phase are as follows: 1) extracting torque data in a sector with the midpoint of the stator-rotor pole alignment position of the conducting phase and the midpoint of the stator pole-rotor slot alignment position of the conducting phase as the midpoint from the phase torque characteristic data of the motor, and calculating the average value of the torque data extracted when the phase current takes different values ​​within the phase current range corresponding to the torque data; 2) Take the average value obtained as the known independent variable value, take the phase current corresponding to the average value as the known function value, and use the interpolation method to obtain the independent variables as 0, T max / (N t -1) 2T max / (N t -1),…,T max The function value when ; 3) Set 0, T max / (N t -1) 2T max / (N t -1),…,T max As the known independent variable value, the obtained function value is taken as the known function value, and the function value when the independent variable is a given total torque is obtained by interpolation method, that is, the given current value of the conducting phase in the said Class I sector; Among them, T max N represents the torque value of the conducting phase when the current of the conducting phase in the class I sector reaches the maximum value; t represents the number of known data points required to obtain the conducting phase current in the class I sector by using the interpolation method; If the rotor is in a Hall sector where only one phase torque is opposite to the given total output torque of the motor, which is recorded as a Class II sector, a high-frequency pulse current is injected into the winding of this phase, and the rotor position is estimated according to the pulse peak value, so as to determine the given torque of the other two phases according to the given total torque, the estimated rotor position and the torque allocation function, and then determine the given current of the other two phases according to the given torque of the other two phases, the estimated rotor position and the current-torque-position characteristics of the motor; The formula for estimating the rotor position based on the pulse peak value is: in, represents the estimated rotor position; i pk Represents the peak value of the high-frequency pulse current; U dc Indicates the DC bus voltage; T pls and D pls They respectively represent the period and duty cycle of the high-frequency rectangular wave voltage; L1 and L2 respectively represent the inductance values ​​of the phase windings into which the high-frequency pulse current is injected at the left and right end points of the Class II sector; θ1 represents the rotor position of the left end point of the Class II sector; the left end point of the Class II sector is the end point with a smaller rotor position, and the right end point is the end point with a larger rotor position.

2. The three-phase SRM current partition planning method based on the switch type Hall position sensor according to claim 1 is characterized in that: The high-frequency pulse current is injected by applying a high-frequency rectangular wave voltage across the phase winding.

3. The three-phase SRM current partition planning method based on the switch type Hall position sensor according to claim 2 is characterized in that: The high and low levels of the high-frequency rectangular wave voltage are respectively the positive and negative bus voltages.

4. The three-phase SRM current partition planning method based on the switch type Hall position sensor according to claim 2 or 3 is characterized in that: The values ​​of the high-frequency rectangular wave voltage duty cycle and frequency meet the following conditions: 1) The peak value of the high-frequency pulse current is not greater than the critical saturation current; 2) The peak value of the high-frequency pulse current is accurately detected; 3) Before the high-frequency rectangular wave voltage changes from a low level to a high level, the high-frequency pulse current has dropped to zero.

5. The three-phase SRM current partition planning method based on switch type Hall position sensor according to claim 1 is characterized in that: The torque distribution function should make the commutation overlap area located in the type II sector.

6. The three-phase SRM current partition planning method based on switch type Hall position sensor according to claim 1 is characterized in that: The steps of obtaining the current-torque-position characteristics are as follows: 1) Extracting the curve data of each phase torque monotonically changing with the phase current from the phase torque characteristic data of the motor; 2) When the rotor position takes different values, the corresponding curve data is used as the known independent variable value, and the phase current value corresponding to the torque data is used as the known function value. The interpolation method is used to obtain the independent variables 0, T max / (N t -1) 2T max / (N t -1),…,T max The function value at the time, that is, the curve data of the phase current changing with the phase torque; 3) The obtained curve data of each phase current changing with the phase torque are summarized to obtain the current-torque-position characteristic table.

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