阅读说明：本技术 基于脉冲注入的开关磁阻电机无位置传感器控制方法 (Pulse injection-based switched reluctance motor position sensorless control method ) 是由 陈昊 刘亮 崔思航 董锋 张珂 巩士磊 阎明 张战 袁利 李祥阳 刘明燕 于 2020-06-04 设计创作，主要内容包括：本发明提出了一种基于脉冲注入的开关磁阻电机无位置传感器控制方法,适用于不同相数的开关磁阻电机控制。该方法采用在开关磁阻电机非励磁相的退磁和闲置区间注入检测脉冲,通过比较脉冲响应电流的上升时间来估计转子的对齐位置。该方法能够适用于电流斩波控制策略和电压斩波控制策略,此外还能保证开关磁阻电机在变速变载条件下转子位置估计的准确性,具有良好的工程应用价值。(The invention provides a pulse injection-based switched reluctance motor position sensorless control method, which is suitable for controlling switched reluctance motors with different phases. The method adopts the technical scheme that detection pulses are injected into a demagnetization and idle interval of a non-excitation phase of the switched reluctance motor, and the alignment position of a rotor is estimated by comparing the rise time of pulse response current. The method can be suitable for a current chopping control strategy and a voltage chopping control strategy, can also ensure the accuracy of rotor position estimation of the switched reluctance motor under the conditions of variable speed and variable load, and has good engineering application value.)

1. The pulse injection-based switched reluctance motor position sensorless control method is characterized by comprising the following steps of:

under inductive unsaturated conditions, the voltage equation for the phase winding can be represented by:

in the formula u_m,i_m,L_m,R_mω and m represent phase voltage, phase current, phase inductance, winding impedance, angular velocity of the motor rotor, and phase number of the motor, respectively;

assuming that there are n on periods in total in the detection current injection interval, then at t_n-1And t_nThe phase voltage equation at a time may be expressed as:

since the sense pulse is generated by hysteresis current control and the current loop width is very small, at t_n-1And t_nThe transient current at the moment is approximately equal to the reference current value I of the detection current_refI.e. i_m(t_n-1)≈i_m(t_n)≈I_refThus can obtain

i_m(t_n-1)R_m≈i_m(t_n)R_m(4)

Since the motor operates at low speed, the magnitude of the detected current is small and the inductance gradients at two adjacent moments are approximately equal, the third parts of equations (2) and (3) can be considered equal, i.e.

Considering that the voltage drop of the power switch tube is negligible compared with the direct current bus voltage, the phase voltage at two ends of the winding can be considered to be equal to the bus voltage, so that the voltage has

u_m(t_n-1)＝u_m(t_n)＝U_DC(6)

In the formula of U_DCRepresents the dc bus voltage;

by combining formulae (4), (5) and (6), the subtraction of formula (3) from formula (2) can be used

According to equation (7), the following relationship exists between the rate of change of phase current and the phase inductance:

suppose that the corresponding current rise times in the last two consecutive on periods are each Δ T_n-1And Δ T_nAnd the loop width of the detected current is Δ i, the amount of change of the current in one on period is 2 Δ i, and thus equation (7) can be expressed as

By dividing both sides of the above formula by 2 Δ i, the formula (10) can be simplified to

According to the above equation, the phase inductance and the rise time of the detection current have the following relationship:

if L is_m(t_n-1)＜L_m(t_n) Then Δ T_n-1＜ΔT_n(12)

If L is_m(t_n-1)＞L_m(t_n) Then Δ T_n-1＞ΔT_n(13)

It can be seen that the rise time of the detection current is proportional to the value of the phase inductance, and the value of the phase inductance is gradually increased before the rotor is aligned, and therefore the rise time of the detection current is also gradually increased, and Δ T is present₁<ΔT₂<…<ΔT_n-1(ii) a After the aligned position of the rotor, the value of the phase inductance starts to decrease, and therefore the rise time of the detection current also gradually decreases, so there is Δ T_n-1>ΔT_n(ii) a In summary, the alignment position of the rotor can be determined by comparing two adjacent rise times of the detection current;

and finally, the position of the rotor of the switched reluctance motor at any moment can be calculated according to the aligned position of the rotor, so that the control operation of the switched reluctance motor without a position sensor is realized.

Technical Field

The invention relates to a pulse injection-based switched reluctance motor position sensorless control method, which is particularly suitable for switched reluctance motors with various phases.

Background

A switched reluctance motor is a self-synchronous motor that requires rotor position information to ensure continuous operation of the motor. The position sensor is an important device for providing rotor position information, but the installation of the position sensor can increase the cost and the volume of the system, and is not beneficial to the integrated development of the switched reluctance motor system. In addition, the non-position sensor is easy to be interfered by severe environments such as moisture, dust and the like to fail, so that the reliability of the switched reluctance motor system is reduced. Therefore, research on sensorless control of the switched reluctance motor is currently focused. The existing control method of the switched reluctance motor without the position sensor mainly comprises the following steps: 1. the method is only suitable for a current chopping control strategy and can generate negative torque; 2. an inductance gradient method that may produce erroneous rotor position estimates near the misalignment location affecting the accuracy of the rotor position estimate; 3. the flux linkage method needs electromagnetic priori knowledge of the motor, is complex in calculation and occupies a large memory; 4. the pulse injection method, which generally adopts the injection of detection pulses in the inductance drop zone and idle zone of the motor to estimate the special position of the rotor, can generate a large amount of negative torque and affect the output performance of the motor. Therefore, there is a need for a switched reluctance motor position sensorless control method that is suitable for different control strategies, does not require complex calculations and electromagnetic prior knowledge of the motor, and does not produce negative torque.

Disclosure of Invention

The invention aims to provide a switched reluctance motor position sensorless control method based on pulse injection, aiming at the problems of the existing switched reluctance motor position sensorless control method.

The position sensorless control method provided by the invention comprises the following steps:

under inductive unsaturated conditions, the voltage equation for the phase winding can be represented by:

in the formula u_m,i_m,L_m,R_mω and m represent phase voltage, phase current, phase inductance, winding impedance, angular velocity of the motor rotor, and phase number of the motor, respectively;

assuming that there are n on periods in total in the detection current injection interval, then at t_n-1And t_nThe phase voltage equation at a time may be expressed as:

since the sense pulse is generated by hysteresis current control and the current loop width is very small, at t_n-1And t_nThe transient current at the moment is approximately equal to the reference current value I of the detection current_refI.e. i_m(t_n-1)≈i_m(t_n)≈I_refThus can obtain

i_m(t_n-1)R_m≈i_m(t_n)R_m(4)

Since the motor operates at low speed, the magnitude of the detected current is small and the inductance gradients at two adjacent moments are approximately equal, the third parts of equations (2) and (3) can be considered equal, i.e.

Considering that the voltage drop of the power switch tube is negligible compared with the direct current bus voltage, the phase voltage at two ends of the winding can be considered to be equal to the bus voltage, so that the voltage has

u_m(t_n-1)＝u_m(t_n)＝U_DC(6)

In the formula of U_DCRepresents the dc bus voltage;

by combining formulae (4), (5) and (6), the subtraction of formula (3) from formula (2) can be used

According to equation (7), the following relationship exists between the rate of change of phase current and the phase inductance:

if L is_m(t_n-1)＜L_m(t_n) Then, then

If L is_m(t_n-1)＞L_m(t_n) Then, then

Suppose that the corresponding current rise times in the last two consecutive on periods are each Δ T_n-1And Δ T_nAnd the loop width of the detected current is Δ i, the amount of change of the current in one on period is 2 Δ i, and thus equation (7) can be expressed as

By dividing both sides of the above formula by 2 Δ i, the formula (10) can be simplified to

According to the above equation, the phase inductance and the rise time of the detection current have the following relationship:

if L is_m(t_n-1)＜L_m(t_n) Then Δ T_n-1＜ΔT_n(12)

If L is_m(t_n-1)＞L_m(t_n) Then Δ T_n-1＞ΔT_n(13)

It can be seen that the rise time of the detection current is proportional to the value of the phase inductance, and the value of the phase inductance is gradually increased before the rotor is aligned, and therefore the rise time of the detection current is also gradually increased, and Δ T is present₁<ΔT₂<…<ΔT_n-1(ii) a After the aligned position of the rotor, the value of the phase inductance starts to decrease, and therefore the rise time of the detection current also gradually decreases, so there is Δ T_n-1>ΔT_n(ii) a In summary, the alignment position of the rotor can be determined by comparing two adjacent rise times of the detection current.

When the aligned position of the rotor of any phase is detected, the timer 2 starts counting until the count value is stored in the register after the aligned position of the rotor of the next phase is detected, and at the same time, the timer is immediately reset and starts to count again. Thus, the time interval Δ T between two successive alignment positions_{2_all}Then is

ΔT_{2_all}＝N_{2_all}×T2 (14)

In the formula N_{2_all}Represents the total count value of timer 1 and T2 represents the count period of timer 2. Thus, the average angular velocity ω between two successive alignment positions can be calculated by:

where Δ θ represents the angular difference between the two aligned positions. The rotor position at other times can then be calculated:

θ＝θ_o+ωN₂×T2 (16)

in the formula [ theta ]_oAnd N₂Indicating the initial rotor position and the real time count of the timer 2, respectively.

Therefore, the position of the rotor of the switched reluctance motor at any moment can be calculated according to the alignment position of the rotor, and the control operation of the switched reluctance motor without a position sensor is realized.

Has the advantages that: the pulse injection-based position sensorless control method does not need additional hardware, complex calculation and priori knowledge of the electromagnetic characteristics of the switched reluctance motor. In addition, the method is also suitable for different control strategies, including a current chopping control strategy and a voltage chopping control strategy, and can not generate negative torque.

Drawings

FIG. 1 is a functional schematic of the position sensorless control method of the present invention.

Fig. 2 is an experimental diagram of the position sensorless control method of the present invention operating in a normal state.

Fig. 3 is an experimental diagram of the position sensorless control method of the present invention operating in an acceleration state.

Fig. 4 is an experimental diagram of the position sensorless control method of the present invention operating in a deceleration state.

FIG. 5 is an experimental plot of the position sensorless control method of the present invention operating in a loaded state.

Fig. 6 is an experimental diagram of the position sensorless control method of the present invention operating in a load shedding state.

Detailed Description

The position sensorless control method proposed by the present invention is further described below with reference to the accompanying drawings:

when the position sensorless control method provided by the invention is applied to a current chopping control strategy, the working principle of the position sensorless control method provided by the invention is shown in fig. 1.

Under inductive unsaturated conditions, the voltage equation for the phase winding can be represented by:

in the formula u_m,i_m,L_m,R_mAnd ω and m represent phase voltage, phase current, phase inductance, winding impedance, angular velocity of the motor rotor, and number of phases of the motor, respectively.

Assuming that there are n on periods in total in the detection current injection interval, then at t_n-1And t_nThe phase voltage equation at a time may be expressed as:

since the sense pulse is generated by hysteresis current control and the current loop width is very small, at t_n-1And t_nThe transient current at the moment is approximately equal to the reference current value I of the detection current_refI.e. i_m(t_n-1)≈i_m(t_n)≈I_refThus can obtain

i_m(t_n-1)R_m≈i_m(t_n)R_m(4)

Since the motor operates at low speed, the magnitude of the detected current is small and the inductance gradients at two adjacent moments are approximately equal, the third parts of equations (2) and (3) can be considered equal, i.e.

Considering that the voltage drop of the power switch tube is negligible compared with the direct current bus voltage, the phase voltage at two ends of the winding can be considered to be equal to the bus voltage, so that the voltage has

u_m(t_n-1)＝u_m(t_n)＝U_DC(6)

In the formula of U_DCRepresenting the dc bus voltage.

By combining formulae (4), (5) and (6), the subtraction of formula (3) from formula (2) can be used

According to equation (7), the following relationship exists between the rate of change of phase current and the phase inductance:

if L is_m(t_n-1)＜L_m(t_n) Then, then

If L is_m(t_n-1)＞L_m(t_n) Then, then

Suppose that the corresponding current rise times in the last two consecutive on periods are each Δ T_n-1And Δ T_nAnd the loop width of the detected current is Δ i, the amount of change of the current in one on period is 2 Δ i, and thus equation (7) can be expressed as

By dividing both sides of the above formula by 2 Δ i, the formula (10) can be simplified to

According to the above equation, the phase inductance and the rise time of the detection current have the following relationship:

if L is_m(t_n-1)＜L_m(t_n) Then Δ T_n-1＜ΔT_n(12)

If L is_m(t_n-1)＞L_m(t_n) Then Δ T_n-1＞ΔT_n(13)

It can be seen that the rise time of the detection current is proportional to the value of the phase inductance, and the value of the phase inductance is gradually increased before the rotor is aligned, and therefore the rise time of the detection current is also gradually increased, and Δ T is present₁<ΔT₂<…<ΔT_n-1. After the aligned position of the rotor, the value of the phase inductance starts to decrease, and therefore the rise time of the detection current also gradually decreases, so there is Δ T_n-1>ΔT_n. In summary, the alignment position of the rotor can be determined by comparing two adjacent rise times of the detection current.

The rotor alignment position can be obtained by comparing the rise times of two adjacent currents of the detection pulses, and the rise time of the response current generated by each detection pulse can be measured and counted by the timer 1, and the counting period of the timer 1 is 5 microseconds, which is denoted as t1. Whereas the calculation of the average rotation speed requires a time interval between two successive alignment positions, the timer 2 can be used to measure this time interval, and the counting period of the timer 2 is 10 microseconds, denoted T2. In the pulse injection interval, when the follow current is reduced to the lower limit value of the detection current, the main switch tube of the power converter starts to be switched on, the detection current starts to rise, and the timer 1 starts to count, when the detection current rises to the upper limit value, the main switch tube of the power converter is immediately switched off, the detection current starts to fall, and the timer 1 stops counting, stores the counting value at the moment into a register, and waits for being compared with the counting value of the next switching-on period. When the detected current is reduced to the lower limit value again, the main switching tube of the power converter is turned on again, the detected current starts to rise, meanwhile, the timer 1 is immediately reset to restart counting, and therefore the second on period is started. The current rise time Δ T per on period can be calculated by:

ΔT＝N_{1_all}×T1 (14)

in the formula N_{1_all}Indicates an openingThe total count value of timer 1 in the on period.

Comparing the count value of the current period with the count value of the previous period, if the count value is larger than the count value of the previous period, continuing to inject the detection pulse, if the count value is smaller than the count value of the previous period, stopping injecting the detection pulse, and simultaneously indicating that the current time is the alignment position of the rotor, wherein the timer 2 needs to start counting immediately, and when the alignment position of one rotor is detected, the timer 2 stores the count value into a register, and simultaneously resets immediately and starts to count again. Thus, the time interval Δ T between two successive alignment positions_{2_all}Then is

ΔT_{2_all}＝N_{2_all}×T2 (15)

In the formula N_{2_all}Representing the total count value of the timer 2. Thus, the average angular velocity ω between two successive alignment positions can be calculated by:

where Δ θ represents the angular difference between the two aligned positions. The rotor position at other times can then be calculated:

θ＝θ_o+ωN₂×T2 (17)

in the formula [ theta ]_oAnd N₂Indicating the initial rotor position and the real time count of the timer 2, respectively.

Therefore, the position of the rotor of the switched reluctance motor at any moment can be calculated according to the alignment position of the rotor, and the control operation of the switched reluctance motor without a position sensor is realized.

FIG. 2 is a waveform diagram of an experiment when the position sensorless control method proposed by the present invention works in a normal state, wherein i_a、i_b、i_c、i_d、θ_e、θ_rAnd theta_erThe estimated rotor position, the actual rotor position and the rotor position estimation error are respectively the winding current of four phases of the switched reluctance motor. As can be seen from the figure, θ_eAnd theta_rThe superposition is kept to be kept,θ_erfluctuating around zero, thus accounting for the accuracy of the rotor position estimate for the position sensorless control method.

FIGS. 3 and 4 are experimental waveforms of the sensorless control method according to the present invention in an acceleration state and a deceleration state, respectively, where N is_SRepresenting the actual rotational speed of the motor. As can be seen from the figure, θ_eAnd theta_rThe method is consistent all the time, and the accuracy of rotor position estimation can still be ensured under the speed change condition by the position sensor-free control method.

FIGS. 5 and 6 are experimental waveforms of the position sensorless control method according to the present invention in a loaded state and a unloaded state, respectively, where θ_eAlways follow theta_rVariation, theta_erThe fluctuation is small, which shows that the control method without the position sensor can ensure the accuracy of the rotor position estimation under the variable load condition.

In conclusion, the pulse injection-based position sensorless control method provided by the invention ensures the accuracy of rotor position estimation, realizes the stable operation of the switched reluctance motor, and has good speed regulation performance and load disturbance resistance.