A method for controlling a switched reluctance motor without a position sensor

Abstract

The present invention belongs to the field of motor control, and specifically relates to a method for controlling a switched reluctance motor without a position sensor. Based on the simplified Fourier series expression of the inductance of the switched reluctance motor and the relationship between the incremental inductance and the inductance, a simplified incremental inductance model is established; the incremental inductance of the switched reluctance motor under different phase currents at three special rotor positions is measured, so as to obtain the relationship between the incremental inductance model coefficient and the phase current, and establish a nonlinear incremental inductance model of the switched reluctance motor; according to the incremental inductance model, an analytical expression for estimating the rotor position of the switched reluctance motor from the phase incremental inductance and its coefficient is derived; when the motor is running, the phase current and bus voltage are detected, the incremental inductance of the excitation phase is estimated by the current slope difference method, the current rotor position is calculated by using the derived rotor position analytical expression, and the position sensorless operation control of the switched reluctance motor is realized according to the estimated rotor position. The control method is simple, has a small amount of calculation, is easy to implement digitally, and has a high position estimation accuracy.

Description

Technical Field

[0001] The invention relates to a switch reluctance motor control method, in particular to a switch reluctance motor position sensorless control method based on an incremental inductance model. Background Art

[0002] The switched reluctance motor is a new type of mechatronic motor with the advantages of simple and solid structure, reliable operation, good speed regulation performance, low manufacturing cost, and suitability for operation in high speed and harsh environments. These excellent characteristics make it one of the research topics in the field of electrical transmission. It has been applied to motor drive systems, fans, water pumps, aerospace and other fields to a certain extent, showing its strong market competitiveness.

[0003] Real-time and accurate acquisition of rotor position information is an important condition for achieving reliable operation of switched reluctance motors, especially high-performance operation. However, in current practical engineering applications, Hall position sensors and rotary transformers are generally still used to detect rotor position, which increases system cost and reduces system reliability, especially in extreme environments such as high temperature and strong electromagnetic fields. In addition, the debugging and initial positioning of the position sensor before normal use will also bring a certain amount of workload. Summary of the invention

[0004] In order to solve the various drawbacks brought by the position sensor to the switched reluctance motor control system, the present invention provides a position sensorless control method for the switched reluctance motor based on an incremental inductance model.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: the control method establishes a simplified incremental inductance model based on the simplified Fourier series expression of the inductance of the switched reluctance motor and the relationship between the incremental inductance and the inductance; the incremental inductance under different phase currents at three special rotor positions of the switched reluctance motor is measured to obtain the relationship between the incremental inductance model coefficient and the phase current, and establish a nonlinear incremental inductance model of the switched reluctance motor; according to the incremental inductance model, an analytical expression for estimating the rotor position of the switched reluctance motor from the phase incremental inductance and its coefficient is derived; when the motor is running, the phase current and bus voltage are detected, the incremental inductance of the excitation phase is estimated by the current slope difference method, the current rotor position is calculated by using the derived rotor position analytical expression, and the position sensorless operation control of the switched reluctance motor is realized according to the estimated rotor position.

[0006] Step (1) measures the incremental inductance of each phase of the motor at different phase currents when the rotor is fully aligned with the stator pole, the edge of the rotor pole is aligned with the center of the stator pole, and the rotor pole is fully aligned with the center of the stator groove. The above three positions are three special positions of the incremental inductance of each phase.

[0007] Step (2), obtaining the relationship between the coefficients of the simplified Fourier series incremental inductance model of the switched reluctance motor and the current according to the data obtained in step (1); and obtaining the nonlinear incremental inductance model of the switched reluctance motor according to the relationship;

[0008] Step (3), measuring the voltage and current signals of each phase of the motor, and estimating the phase incremental inductance using the current slope difference method;

[0009] Step (4), measuring the current signal of each phase of the motor, and calculating the incremental inductance model coefficient using the relationship between the incremental inductance model coefficient obtained in step (2) and the current change to obtain the incremental inductance model coefficient.

[0010] Step (5), calculating the current rotor position angle using a nonlinear incremental inductance model based on the phase incremental inductance calculated in step (3) and the incremental inductance coefficient calculated in step (4);

[0011] Step (1), measure the incremental inductance at three rotor positions of the motor, that is, the incremental inductance l at which the rotor and stator poles are completely aligned inc_a (i), that is, the rotor position angle θ elec = 0°; the incremental inductance l at the point where the rotor pole edge is aligned with the stator pole center inc_m (i), that is, the rotor position angle θ elec =90°; incremental inductance l at which the rotor pole is completely aligned with the center of the stator groove inc_u (i), that is, the rotor position angle θ elec =180°;

[0012] In step (2), the simplified Fourier series incremental inductance model of the switched reluctance motor is:

[0013]

[0014] Among them, θ elec is the U-phase rotor position electrical angle, and its relationship with the rotor mechanical angle is θ elec = N r θ mec , N r is the number of rotor poles; L inc_u , L inc_v and L inc_w are the incremental inductances of the switched reluctance motor phases u, v and w respectively; L inc_0 , L inc_1 and L inc_2 are the amplitudes of its fundamental wave, first harmonic and second harmonic respectively;

[0015] The model is based on the simplified inductance Fourier series expression of the switched reluctance motor and the relationship between inductance and incremental inductance. The simplified inductance Fourier series expression is:

[0016]

[0017] Among them, L u , L v and L w are the inductances of the switched reluctance motor u, v and w phases respectively; L0, L1 and L2 are the amplitudes of its fundamental wave, first harmonic and second harmonic respectively;

[0018] The relationship between inductance and incremental inductance is:

[0019]

[0020] Using the l measured in step (1) inc_a (i) l inc_m (i) and l inc_u (i) According to the incremental inductance model coefficient L inc_0 (i) L inc_1 (i) and L in c _2 (i) and l inc_a (i) l inc_m (i) and l inc_u (i), we get L inc_0 (i) L inc_1 (i) and L in c _2 (i) Relationship with phase current;

[0021] L inc_0 (i) L inc_1 (i) and L inc_2 (i) and l inc_a (i) l inc_m (i) and l inc_u The relationship (i) is:

[0022]

[0023] In step (3), the analytical formula for estimating the phase incremental inductance using the current slope difference method is:

[0024]

[0025] Among them, U dc is the DC power supply voltage; and They are the current change slopes when the voltages at both ends of the phase winding are the positive power supply voltage and the negative power supply voltage respectively.

[0026] The analytical formula of the U-phase electrical angle obtained by solving the U-phase nonlinear incremental inductance model of the switched reluctance motor is:

[0027]

[0028] The analytical formula of the U-phase electrical angle obtained by solving the V-phase nonlinear incremental inductance model of the switched reluctance motor is:

[0029]

[0030] The analytical formula of the U-phase electrical angle obtained by solving the W-phase nonlinear incremental inductance model of the switched reluctance motor is:

[0031]

[0032] According to the above method, the position detection of the switched reluctance motor without a position sensor can be realized.

[0033] Beneficial effects: The present invention uses the voltage and current information of the switched reluctance motor to indirectly detect the rotor position and realize the position sensorless operation of the motor, thereby reducing the system cost and improving the reliability of the system. Taking the three-phase 6 / 4-pole switched reluctance motor as the control object, the values ​​of the phase incremental inductance at three special positions under different phase currents are first measured, and then the relationship between the incremental inductance model coefficient and the phase current is obtained, thereby obtaining the nonlinear incremental inductance model of the switched reluctance motor. On the basis of this model, the phase incremental inductance and its coefficient are estimated using the real-time detected phase voltage and phase current signals, and then the rotor position is calculated, thereby realizing the position sensorless operation of the motor.

[0034] Advantages: The position sensorless control method of the present invention is simple, has a small amount of calculation, is easy to implement digitally, and has a high position estimation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of three special rotor positions of the switched reluctance motor.

[0036] Figure 2 It is a scatter plot of the phase incremental inductance versus phase current at three special rotor positions of the prototype.

[0037] Figure 3 It is a scatter plot of the prototype nonlinear incremental inductance model coefficient changing with phase current.

[0038] Figure 4 This is the prototype phase incremental inductance curve.

[0039] Figure 5 It is a schematic diagram of a position sensorless speed control system for a switched reluctance motor according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0040] An embodiment of the present invention is described below with reference to the accompanying drawings.

[0041] Embodiment 1: Taking a three-phase 6 / 4-pole switched reluctance motor as a prototype, the steps of the switched reluctance motor position sensorless control method provided by the present invention are as follows:

[0042] 1) The current slope difference method is used to measure the phase incremental inductance of the prototype at different phase currents when the rotor and stator poles are completely aligned, when the rotor pole edge is aligned with the stator pole center, and when the rotor pole is completely aligned with the stator groove center. The formula for estimating the phase incremental inductance using the current slope difference method is:

[0043]

[0044] The three positions are three special positions of the incremental inductance of each phase, as shown in the attached Figure 1 The curves of the prototype phase incremental inductance changing with phase current at three special positions are shown in the attached figure. Figure 2 shown.

[0045] 2) The relationship data table between the three coefficients of the simplified Fourier incremental inductance model of the prototype and the three-phase current is calculated by formula (2). The formula (2) is:

[0046]

[0047] The three coefficients are L inc_0 (i) L inc_1 (i) and L inc_2 (i) The curves of the three coefficients changing with phase current are shown in the attached figure. Figure 3 As shown in the figure, it can be seen that as the phase current increases, the three coefficients become smaller.

[0048] 3) When the motor is running, the current and voltage of the motor excitation phase are detected in real time, and the phase incremental inductance is estimated using the above formula (1). According to the detected phase current, the relationship data table described in step 2) is queried to obtain the three coefficients of the incremental inductance model.

[0049] 4) The rotor position is estimated based on the incremental inductance and coefficient of the excitation phase obtained in step 3) according to the simplified incremental inductance Fourier series model. Taking the U phase as an example, the current position can be estimated by substituting the estimated U phase incremental inductance into the following formula.

[0050]

[0051] The curve of the prototype phase incremental inductance changing with phase current and rotor position is shown in the attached figure. Figure 4 shown.

[0052] 4) The estimated angle is differentiated to estimate the speed; the speed PI regulator is used to calculate the given current according to the given speed and the estimated speed; the given current of each phase is distributed according to the given current, the estimated angle and the opening and closing angle; according to the given current and the actual current of each phase, the current chopping control is used to obtain the driving signal of the main switching device of each phase, so as to realize the control of the main switching device in the power converter, thereby realizing the control of the switched reluctance motor.

Claims

1. A method for controlling a switched reluctance motor without a position sensor, characterized in that: This control method establishes a simplified incremental inductance model based on the simplified Fourier series expression of the inductance of the switched reluctance motor and the relationship between the incremental inductance and the inductance; the incremental inductance of the switched reluctance motor under different phase currents at three special rotor positions is measured to obtain the relationship between the incremental inductance model coefficient and the phase current, and the nonlinear incremental inductance model of the switched reluctance motor is established; based on the incremental inductance model, an analytical expression for estimating the rotor position of the switched reluctance motor from the phase incremental inductance and its coefficient is derived; when the motor is running, the phase current and bus voltage are detected, the incremental inductance of the excitation phase is estimated by the current slope difference method, the current rotor position is calculated using the derived rotor position analytical expression, and the position sensorless operation control of the switched reluctance motor is realized based on the estimated rotor position; The specific steps of the position sensorless operation control of the switched reluctance motor are as follows: Step (1), measuring the value of the incremental inductance of each phase of the motor at different phase currents at the position where the rotor and stator poles are completely aligned, the position where the rotor pole edge is aligned with the stator pole center, and the position where the rotor pole is completely aligned with the stator groove center, the above three positions are three special positions of the incremental inductance of each phase; Step (2), obtaining the relationship between the coefficients of the simplified Fourier series incremental inductance model of the switched reluctance motor and the current according to the data obtained in step (1); and obtaining the nonlinear incremental inductance model of the switched reluctance motor according to the relationship; Step (3), measuring the voltage and current signals of each phase of the motor, and estimating the phase incremental inductance using the current slope difference method; Step (4), measuring the current signal of each phase of the motor, and calculating the incremental inductance model coefficient using the relationship between the incremental inductance model coefficient obtained in step (2) and the current change to obtain the incremental inductance model coefficient; Step (5), calculating the current rotor position angle using a nonlinear incremental inductance model based on the phase incremental inductance calculated in step (3) and the incremental inductance coefficient calculated in step (4); Step (1), measure the incremental inductance at three special rotor positions of the motor, namely: the incremental inductance l at which the rotor and stator poles are completely aligned inc_a (i), that is, the rotor position angle θ elec =0°; when the rotor pole edge is aligned with the stator pole center, the incremental inductance l inc_m (i), that is, the rotor position angle θ elec =90°; incremental inductance l at which the rotor pole is completely aligned with the center of the stator groove inc_u (i), that is, the rotor position angle θ elec =180°; In step (2), the simplified Fourier series incremental inductance model of the switched reluctance motor is: Among them, θ elec is the U-phase rotor position electrical angle, and its relationship with the rotor mechanical angle is θ elec =N r θ mec , N r is the number of rotor poles; L inc_u , L inc_v and L inc_w are the incremental inductances of the switched reluctance motor phases u, v and w respectively; L inc_0 , L inc_1 and L inc_2 are the amplitudes of its fundamental wave, first harmonic and second harmonic respectively; The model is based on the simplified inductance Fourier series expression of the switched reluctance motor and the relationship between inductance and incremental inductance; the simplified inductance Fourier series expression is: Among them, L u , L v and L w are the inductances of the switched reluctance motor u, v and w phases respectively; L0, L1 and L2 are the amplitudes of its fundamental wave, first harmonic and second harmonic respectively; The relationship between inductance and incremental inductance is: Using the l measured in step (1) inc_a (i) l inc_m (i) and l inc_u (i), according to the incremental inductance model coefficient L inc_0 (i) L inc_1 (i) and L inc_2 (i) and l inc_a (i) l inc_m (i) and l inc_u (i), we get L inc_0 (i) L inc_1 (i) and L inc_2 (i) Relationship with phase current; L inc_0 (i) L inc_1 (i) and L inc_2 (i) and l inc_a (i) l inc_m (i) and l inc_u The relationship (i) is: In step (3), the analytical formula for estimating the phase incremental inductance using the current slope difference method is: Among them, U dc is the DC power supply voltage; and are the current change slopes when the voltages at both ends of the phase winding are the positive power supply voltage and the negative power supply voltage respectively; The analytical formula of the U-phase electrical angle obtained by solving the U-phase nonlinear incremental inductance model of the switched reluctance motor is: The analytical formula of the U-phase electrical angle obtained by solving the V-phase nonlinear incremental inductance model of the switched reluctance motor is: The analytical formula of the U-phase electrical angle obtained by solving the W-phase nonlinear incremental inductance model of the switched reluctance motor is: According to the above method, the position detection of the switched reluctance motor without a position sensor can be realized.

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