Current prediction control method of switched reluctance motor based on vector synthesis

Abstract

The invention discloses a voltage vector synthesis-based current prediction control method for a switched reluctance motor, and belongs to the field of switched reluctance motor control. The current prediction control method comprises the following steps: obtaining a given current of a rotor according to a PI controller of a rotating speed ring; determining the region of the rotor by measuring the actual mechanical position of the rotor; selecting a corresponding voltage vector through an area where the rotor is located; determining the duty ratio of the voltage vector according to the given current; and sending the selected voltage vector action time and a switching signal corresponding to the duty ratio to an asymmetric half-bridge power converter, and controlling the switched reluctance motor. The method has the advantages that the maximum error given by current tracking is reduced by about 75%, the current pulsation rate is reduced by about 7%, the current tracking given effect is obviously improved, and the problems that the current peak value is high and the current pulsation is large in the commutation period of a traditional finite set model prediction control algorithm are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of model predictive control of switched reluctance motors, and in particular to a current predictive control method based on vector synthesis for solving the problems of high current peak and large current pulsation when the switched reluctance motor operates in a commutation overlap region. Background Art

[0002] Switched reluctance motor (SRM) has attracted extensive attention due to its strong structure, simple manufacturing process, low cost and high reliability. It can be applied to military and civilian fields such as electric vehicles, wind power generation, precision machining and specific industrial applications. However, during the operation of SRM, its parameters such as inductance and flux change according to the changes of current and mechanical angle at the same time. After the magnetization curve is saturated, the inductance has nonlinear characteristics, making it difficult to accurately obtain the motor parameters and increasing its control difficulty. In the process of controlling SRM, traditional control methods inevitably have certain errors in current tracking, especially during current commutation, which may cause large current peaks and current pulsations. The most commonly used current chopping control (CCC control) has fast dynamic response and can limit current errors by setting the loop width, but its switching frequency is uneven and not fixed. In addition, since the inductance of the SRM is relatively small in the non-aligned position, the current has large pulsations and peaks when the switching frequency is limited.

[0003] In order to solve the above problems, the voltage chopping PWM control method can make the switching frequency fixed and the waveform relatively improved. However, since the inductance parameters of SRM depend on the accurate acquisition of phase current and rotor position, it is difficult to design PI parameters that are well applicable to all working conditions. SRM under direct instantaneous torque control (DITC) can make the torque more stable and can effectively suppress the torque pulsation caused by phase change. However, similar to the CCC control method, there is also the problem of current waveform distortion. Summary of the invention

[0004] Technical problem: The purpose of the invention is to overcome the shortcomings of the prior art and to provide a current prediction control method for a switched reluctance motor based on vector synthesis, which has a lower peak current and smaller current pulsation during commutation overlap, while reducing the amount of calculation and optimizing the current waveform.

[0005] Technical solution: To achieve the above-mentioned purpose, a current prediction control method of a switched reluctance motor based on voltage vector synthesis of the present invention comprises the following steps:

[0006] Step 1: Obtain the given current of the rotor according to the PI controller of the speed loop;

[0007] Step 2: Determine the rotor area by measuring the actual mechanical position of the rotor;

[0008] Step 3: Select the corresponding voltage vector according to the area where the rotor is located;

[0009] Step 4: Determine the duty cycle of the voltage vector according to the current given;

[0010] Step 5: Send the selected voltage vector action time and the switching signal corresponding to the duty cycle to the asymmetric half-bridge power converter to control the switched reluctance motor.

[0011] In step 1, the specific method of obtaining the rotor given current according to the PI controller of the speed loop includes:

[0012] The mechanical angle θ(k) of the switched reluctance motor (SRM) is measured using an encoder and differentiated Get the actual speed ω, and the given speed ω * The comparison result is output through the PI regulator to the given current i of the rotor. * .

[0013] In step 2, the specific method of determining the region where the rotor is located by measuring the actual mechanical position of the rotor includes:

[0014] First, according to the electrical angle θ of the rotor e Determine areas Ⅰ to VI as follows:

[0015] (0°, 60°) corresponds to area I, (60°, 120°) corresponds to area II, (120°, 180°) corresponds to area III, (180°, 240°) corresponds to area IV, (240°, 300°) corresponds to area V, and (300°, 360°) corresponds to area VI;

[0016] Then the mechanical angle θ of the rotor is measured by the encoder. e =pθ, p is the number of pole pairs of the switched reluctance motor, which determines the area where the rotor is located.

[0017] In step 3, the specific method of selecting the corresponding voltage vector according to the region where the rotor is located includes:

[0018] Voltage vector V1~V 12 The switch state variable correspondence table is:

[0019] Voltage Vector Switch state variable Voltage Vector Switch state variable Voltage Vector Switch state variable <![CDATA[V1]]> (1,-1,-1) <![CDATA[V3]]> (-1,1,-1) <![CDATA[V5]]> (-1,-1,1) <![CDATA[V2]]> (1,1,-1) <![CDATA[V7]]> (1,0,-1) <![CDATA[V8]]> (0,1,-1) <![CDATA[V4]]> (-1,1,1) <![CDATA[V9]]> (-1,1,0) <![CDATA[V 10 ]]> (-1,0,1) <![CDATA[V6]]> (1,-1,1) <![CDATA[V 11 ]]> (0,-1,1) <![CDATA[V 12 ]]> (1,-1,0)

[0020] The single-phase conduction area is Ⅰ, Ⅲ, Ⅴ, and the two-phase conduction area is Ⅱ, Ⅳ, Ⅵ; when the rotor is in the single-phase conduction area, a single voltage vector V is selected. si and the corresponding zero vector V s0 , in the two-phase conduction region, two voltage vectors V are selected from three candidate voltage vectors through a cost function designed based on the current error.si 、V sj and the corresponding zero vector V s0 ;

[0021] The correspondence table between the rotor area and the voltage vector to be selected is:

[0022] area <![CDATA[θ e ]]> <![CDATA[V si (In sj )]]> <![CDATA[V s0 ]]> Corresponding conduction phase Ⅰ (0°,60°) <![CDATA[V1]]> (0,-1,-1) A Ⅱ (60°,120°) <![CDATA[V2、V7、V8]]> (0,0,-1) A,B Ⅲ (120°,180°) <![CDATA[V3]]> (-1,0,-1) B Ⅳ (180°,240°) <![CDATA[V4、V9、V 10 ]]> (-1,0,0) B,C Ⅴ (240°,300°) <![CDATA[V5]]> (-1,-1,0) C Ⅵ (300°，360°) <![CDATA[V6、V 11 、In 12 ]]> (0,-1,0) C,A

[0023] For the rotor in the two-phase conduction region, from the three selected voltage vectors and the corresponding zero vector V s0 The two voltage vectors V are selected by a cost function designed based on the current error si 、V sj The specific steps are:

[0024] Step 3.1: Using the first-order forward Euler discretization method, use the formula

[0025]

[0026] Predict the current at time (k+1), where i(k+1) and i(k) are the currents at time k+1 and time k respectively, T s is the sampling period, V p (k),L p (k) are the rotor phase voltage and phase inductance at time k; R, ω r ,θ are the total rotor resistance, speed and mechanical angle respectively;

[0027] Step 3.2: Cost function expression designed based on given current and predicted current:

[0028] J = norm(i * -i p (k+1)) 2 +norm(i * -i q (k+1)) 2

[0029] Where J is the cost function, norm is the second-order norm, i * For a given current, (p,q)∈{(A,B),(B,C),(C,A)},i p (k+1),i q (k+1) are the currents of phases p and q at the moment (k+1);

[0030] Step 3.3: Select two voltage vectors V from the three candidate voltage vectors through the cost function si 、V sj ;

[0031]

[0032]

[0033]

[0034] Where: V x ,V y ,V z There are three candidate vectors.

[0035] First, pq is determined according to the region where the rotor is located. Second, three voltage vectors V are applied according to the correspondence table between the region where the rotor is located and the voltage vector to be selected. x ,V y ,V z , we get three cost functions J1, J2, and J3, and select the voltage vectors corresponding to the two smaller cost functions.

[0036] In step 4, the specific method of determining the duty cycle of the voltage vector according to the given current includes:

[0037] The voltage vector selected according to the region where the rotor is located in step 3 and the corresponding zero vector act together, and the duty cycle of the voltage vector action is determined by following the given current;

[0038] The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), and a single candidate voltage vector V is selected according to the area where the rotor is located. si and the corresponding zero vector V s0 Working together, the predicted current at time (k+1) is:

[0039] i p (k+1)=i p (k)+S i dT s +S0(1-d)T s

[0040] Where: p∈(A,B,C)

[0041]

[0042] d is the voltage vector V si The duty cycle, S i , S0 is to apply V to the conducting phase winding si ,V s0 The rate of change of current after

[0043] In order to make: i(k+1)=i*, reverse the solution i p (k+1)=i p (k)+S i dT s +S0(1-d)T s Get the d expression:

[0044]

[0045] Among them, dot is the dot product operation, norm is the second-order norm;

[0046] V s =dV si +(1-d)V s0 =dV si

[0047] Among them, V s is the resultant voltage vector;

[0048] The rotor is in the two-phase conduction area (II, IV, VI), and the voltage vector V is selected according to the area where the rotor is located. si 、V sj Working together, first of all, Δi pq and S i d1T s +S j (1-d1)T s Phase Coherence:

[0049] i pq (k+1)=i pq (k)+S i d1T s +S j (1-d1)T s

[0050] Δi pq =i pq (k+1)-i pq (k)

[0051] Where: pq∈{AB,BC,CA}, i pq (k+1), i pq (k) are the current vectors at time k+1 and k, i pq (k+1)=(i p (k+1), i q (k+1)), i pq (k)=(i p (k), i q (k)).

[0052]

[0053] In order to make: Δi pq and S i d1T s +S j (1-d1)T sThe phases of the two vectors are consistent, that is, the ratio of the components of the two vectors on the xy axis is the same:

[0054]

[0055] d1 is the voltage vector V si The weight, S i ,S j To apply voltage vector V to the two phases that are turned on si 、V sj The rate of change of current after

[0056] Inverse Solution Get the expression of d1:

[0057]

[0058] Voltage vector synthesis results:

[0059] V syn =d1V si +(1-d1)V sj

[0060] Among them, V syn is the voltage vector V si 、V sj The resultant voltage vector acting together;

[0061] The resultant voltage vector V syn and zero vector V s0 Working together, the predicted current at time (k+1) is:

[0062] i pq (k+1)=i pq (k)+S syn dT s +S0(1-d2)T s

[0063] in:

[0064]

[0065] d2 is the voltage vector V syn The duty cycle, S syn , S0 is the voltage vector V applied to the two phases that are turned on syn ,V s0 The rate of change of current after

[0066] In order to make: i(k+1)=i*, reverse the solution i pq (k+1)=i pq (k)+S syn dT s +S0(1-d2)Ts Get the d2 expression:

[0067]

[0068] V s =d2V syn +(1-d2)V s0

[0069] =d1d2V si +d2(1-d1)V sj +(1-d2)V s0

[0070] Among them, V s is the resultant voltage vector.

[0071] In step 5, the specific method of sending the selected voltage vector action time and the switch signal corresponding to the duty cycle to the asymmetric half-bridge power converter to control the switched reluctance motor includes:

[0072] The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), the voltage vector V si and zero vector V s0 The action time T1, T0 is:

[0073]

[0074] T s is a switching cycle of an asymmetric half-bridge power converter;

[0075] The rotor is in the two-phase conduction area (Ⅱ, Ⅳ, Ⅵ), the voltage vector V si ,V sj and zero vector V s0 The action time T2, T1, T0 is:

[0076]

[0077] Beneficial effects: In order to solve the traditional control method of the current technology, the present invention determines the current setting through the speed error, and the cost function is designed as the error between the current setting and the actual current. Before predicting the current, delay compensation is performed first, and then the current of the next cycle is estimated. After that, by traversing all possible switching states, the cost function is calculated, and a switching state with the smallest cost function is selected as the optimal choice to act on the switched reluctance motor within a control cycle. Compared with the traditional control method, a single effective vector and a zero vector are selected in the single-phase conduction area of ​​the switched reluctance motor, and three candidate voltage vectors and a zero vector are selected in the two-phase conduction area. During the commutation period, the optimal vector is judged and selected according to the cost function. It effectively solves the problem that the traditional algorithm has to traverse all vectors in each sampling cycle, and only three cost function calculations are performed during the commutation period. It can not only reduce the amount of calculation of the processor, but also optimize the current waveform, especially reduce pulsation and overshoot during current commutation. The maximum error and pulsation rate are significantly reduced, the maximum error given by current tracking is reduced by about 75%, and the current pulsation rate is reduced by about 7%, which significantly improves the current tracking effect and effectively solves the problems of high current peak and large current pulsation during commutation in traditional finite set model predictive control algorithms. It has wide practicality in this technical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is a three-phase inductance diagram when the SRM of the present invention is in operation.

[0079] Figure 2 (a) is an asymmetric half-bridge power converter S p =1 schematic diagram.

[0080] Figure 2 (b) is an asymmetric half-bridge power converter S p =0 schematic diagram.

[0081] Figure 2 (c) is an asymmetric half-bridge power converter S p =-1 schematic diagram.

[0082] Figure 3 These are 12 kinds of voltage vector distribution diagrams to be selected according to the present invention.

[0083] Figure 4 The voltage vector V when the single phase is turned on in the present invention si and V s0 Synthesis schematic.

[0084] Figure 5 is the voltage vector V when the two phases of the present invention are turned on si and V sj Synthesis schematic.

[0085] Figure 6is the voltage vector V when the two phases of the present invention are turned on syn and V s0 Synthesis schematic.

[0086] Figure 7 It is a block diagram of the overall current prediction control system of the present invention.

[0087] Figure 8 It is the waveform diagram of the current and voltage of phases A and B under the traditional control mode; the dotted box area is the waveform diagram of the current and voltage of phases A and B during the commutation period.

[0088] Fig. 9 1 is a waveform diagram of the current and voltage of the two phases A and B under the control mode of the embodiment of the present invention; the dotted box area is the waveform diagram of the current and voltage of the two phases A and B during the commutation period. DETAILED DESCRIPTION

[0089] The present invention will be further described below in conjunction with the embodiments in the accompanying drawings. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0090] The motor used in the example is a 5kW three-phase 12 / 8 switched reluctance motor.

[0091] like Figure 1-9 As shown, a current prediction control method of a switched reluctance motor based on voltage vector synthesis of the present invention comprises the following steps:

[0092] Step 1: Obtain the given current of the rotor according to the PI controller of the speed loop;

[0093] like Figure 8 As shown in the figure, the encoder measures the mechanical angle θ(k) of the switched reluctance motor (SRM) by differentiating Get the actual speed ω, and the given speed ω * The comparison result is output through the PI regulator to output the given current i of the rotor. * .

[0094] Step 2: Determine the rotor area by measuring the actual mechanical position of the rotor;

[0095] First, according to the operating characteristics of SRM, the conduction phase corresponds to the rising interval of inductance, and only one or two phases of the three phases are turned on, and the following is obtained: Figure 1 The three-phase inductance diagram of the SRM during operation is shown in Figure 1. In a rotor electrical angle cycle of 360°, according to the rotor electrical angle θ e Determine areas Ⅰ to VI as follows:

[0096] (0°, 60°) corresponds to area I, (60°, 120°) corresponds to area II, (120°, 180°) corresponds to area III, (180°, 240°) corresponds to area IV, (240°, 300°) corresponds to area V, and (300°, 360°) corresponds to area VI.

[0097] Then the mechanical angle θ of the rotor is measured by the encoder. e =pθ, p is the number of pole pairs of the switched reluctance motor, which determines the area where the rotor is located.

[0098] Step 3: Select the corresponding voltage vector according to the area where the rotor is located;

[0099] like Figure 2 As shown in (a, b, c), the asymmetric half-bridge power converter is divided into three states: excitation mode, natural freewheeling mode and demagnetization mode. In the figure: VT1, VT2 are IGBTs, VD1, VD2 are freewheeling diodes, V P ,V k Input voltage and output voltage respectively; the direction of the arrow is the current flow in different modes.

[0100] The three state functions corresponding to the three working modes are:

[0101]

[0102] S p is the working state of the p-phase winding, where p∈(A,B,C);

[0103] S p ∈{1,0,-1}, because there are three-phase windings A, B, and C, so there are 3 3 = 27 voltage states correspond to 27 voltage vectors, which are simplified to 12 voltage vectors.

[0104] Voltage vector V1~V 12 The switch state variable correspondence table is:

[0105] Voltage Vector Switch state variable Voltage Vector Switch state variable Voltage Vector Switch state variable <![CDATA[V1]]> (1,-1,-1) <![CDATA[V3]]> (-1,1,-1) <![CDATA[V5]]> (-1,-1,1) <![CDATA[V2]]> (1,1,-1) <![CDATA[V7]]> (1,0,-1) <![CDATA[V8]]> (0,1,-1) <![CDATA[V4]]> (-1,1,1) <![CDATA[V9]]> (-1,1,0) <![CDATA[V 10 ]]> (-1,0,1) <![CDATA[V6]]> (1,-1,1) <![CDATA[V 11 ]]> (0,-1,1) <![CDATA[V 12 ]]> (1,-1,0)

[0106] Figure 3 This is a distribution diagram of 12 candidate voltage vectors. The directions indicated by V1, V3, and V5 are the corresponding vectors when the three phases A, B, and C are turned on separately. The same direction represents the same vector, and the other directions are the results of vector synthesis.

[0107] The single-phase conduction area is Ⅰ, Ⅲ, Ⅴ, and the two-phase conduction area is Ⅱ, Ⅳ, Ⅵ. When the rotor is in the single-phase conduction area, a single voltage vector V is selected. si and the corresponding zero vector V s0, in the two-phase conduction region, two voltage vectors V are selected from three candidate voltage vectors through a cost function designed based on the current error. si 、V sj and the corresponding zero vector V s0 .

[0108] The correspondence table between the rotor area and the voltage vector to be selected is:

[0109]

[0110]

[0111] Step 3.1: By the first-order forward Euler discretization method, use the formula:

[0112]

[0113] Predict the current at time (k+1), where i(k+1) and i(k) are the currents at time k+1 and time k respectively, T s is the sampling period, V p (k),L p (k) are the rotor phase voltage and phase inductance at time k; R, ω r ,θ are the total rotor resistance, speed and mechanical angle respectively.

[0114] Step 3.2: Cost function expression designed based on given current and predicted current:

[0115] J = norm(i * -i p (k+1)) 2 +norm(i * -i q (k+1)) 2

[0116] Among them, J is the cost function, norm is the second-order norm, i * For a given current, (p,q)∈{(A,B),(B,C),(C,A)},i p (k+1),i q (k+1) are the currents of phases p and q at time (k+1).

[0117] Step 3.3: Select two voltage vectors V from the three candidate voltage vectors through the cost function si 、V sj .

[0118]

[0119]

[0120]

[0121] Where: V x ,V y ,V z There are three candidate vectors.

[0122] First, pq is determined according to the region where the rotor is located. Then, three voltage vectors V are applied according to the correspondence table between the region where the rotor is located and the voltage vector to be selected. x ,V y ,V z , we get three cost functions J1, J2, and J3, and select the voltage vectors corresponding to the two smaller cost functions.

[0123] Step 4: Determine the duty cycle of the voltage vector according to the current given;

[0124] The voltage vector selected according to the region where the rotor is located in step 3 and the corresponding zero vector act together, and the duty cycle of the voltage vector action is determined by following the given current.

[0125] The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), and a single candidate voltage vector V is selected according to the area where the rotor is located. si and the corresponding zero vector V s0 Working together, the predicted current at time (k+1) is:

[0126] i p (k+1)=i p (k)+S i dT s +S0(1-d)T s

[0127] Where: p∈(A,B,C)

[0128]

[0129] d is the voltage vector V si The duty cycle, S i , S0 is to apply V to the conducting phase winding si ,V s0 The rate of change of current after.

[0130] In order to make i(k+1)=i*, inversely solve i p (k+1)=i p (k)+S i dT s +S0(1-d)T s Get the d expression:

[0131]

[0132] Where dot is the dot product operation and norm is the second-order norm.

[0133] V s wxya si +(1-d)V s0 =dV si

[0134] Among them, V s is the resultant voltage vector.

[0135] Figure 4 When single phase is on, the voltage vector V si and the corresponding zero vector V s0 Synthesis schematic.

[0136] The rotor is in the two-phase conduction area (II, IV, VI), and the voltage vector V is selected according to the area where the rotor is located. si 、V sj Working together, first of all, Δi pq and S i d1T s +S j (1-d1)T s Phase Coherence:

[0137] i pq (k+1)=i pq (k)+S i d1T s +S j (1-d1)T s

[0138] Δi pq =i pq (k+1)-i pq (k)

[0139] Where: pq∈{AB,BC,CA}, i pq (k+1), i pq (k) are the current vectors at time k+1 and k, i pq (k+1)=(i p (k+1), i q (k+1)), i pq (k)=(i p (k), i q (k)).

[0140]

[0141] In order to make Δi pq and S i d1T s +S j(1-d1)T s The phase is consistent, that is, the ratio of the components of the two vectors on the xy axis is the same:

[0142]

[0143] d1 is the voltage vector V si The weight, S i ,S j To apply voltage vector V to the two phases that are turned on si 、V sj The rate of change of current after.

[0144] Inverse Solution Get the expression of d1

[0145]

[0146] Voltage vector synthesis results:

[0147] V syn =d1V si +(1-d1)V sj

[0148] Among them, V syn is the voltage vector V si 、V sj The resultant voltage vector acting together.

[0149] Figure 5 is the voltage vector V when two phases are turned on si and V sj Synthesis schematic.

[0150] The resultant voltage vector V syn and zero vector V s0 Working together, the predicted current at time (k+1) is:

[0151] i pq (k+1)=i pq (k)+S syn dT s +S0(1-d2)T s

[0152] in:

[0153]

[0154] d2 is the voltage vector V syn The duty cycle, S syn , S0 is the voltage vector V applied to the two phases that are turned on syn ,V s0 The rate of change of current after.

[0155] In order to make i(k+1)=i*, inversely solve i pq (k+1)=i pq (k)+S syn dT s +S0(1-d2)T s Get d2 expression

[0156]

[0157] V s =d2V syn +(1-d2)V s0

[0158] =d1d2V si +d2(1-d1)V sj +(1-d2)V s0

[0159] Among them, V s is the resultant voltage vector.

[0160] Figure 6 is the voltage vector V when two phases are turned on syn and V s0 Synthesis schematic.

[0161] Step 5: Send the selected voltage vector action time and the switching signal corresponding to the duty cycle to the asymmetric half-bridge power converter to control the switched reluctance motor.

[0162] The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), the voltage vector V si and zero vector V s0 The action time T1, T0 is:

[0163]

[0164] T s is a switching cycle of an asymmetric half-bridge power converter.

[0165] The rotor is in the two-phase conduction area (Ⅱ, Ⅳ, Ⅵ), the voltage vector V si ,V sj and zero vector V s0 The action time T2, T1, T0 is:

[0166]

[0167] The corresponding switching signal is sent to an asymmetric half-bridge power converter to control the switched reluctance motor.

[0168] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A current prediction control method for a switched reluctance motor based on voltage vector synthesis, characterized in that: The following steps are involved: Step 1: Obtain the given current of the rotor according to the PI controller of the speed loop; Step 2: Determine the rotor area by measuring the actual mechanical position of the rotor; Step 3: Select the corresponding voltage vector according to the area where the rotor is located; Step 4: Determine the duty cycle of the voltage vector according to the current given; Step 5: Send the selected voltage vector action time and the switching signal corresponding to the duty cycle to the asymmetric half-bridge power converter to control the switched reluctance motor.

2. The current prediction control method of a switched reluctance motor based on voltage vector synthesis according to claim 1 is characterized in that: In step 1, the specific method of obtaining the rotor given current according to the PI controller of the speed loop includes: The mechanical angle θ(k) of the switched reluctance motor (SRM) is measured using an encoder and differentiated Get the actual speed ω, and the given speed ω * The comparison result is output through the PI regulator to the given current i of the rotor. * .

3. The current prediction control method of a switched reluctance motor based on voltage vector synthesis according to claim 1 is characterized by: In step 2, the specific method of determining the region where the rotor is located by measuring the actual mechanical position of the rotor includes: First, according to the electrical angle θ of the rotor e Determine areas Ⅰ to VI as follows: (0°, 60°) corresponds to area I, (60°, 120°) corresponds to area II, (120°, 180°) corresponds to area III, (180°, 240°) corresponds to area IV, (240°, 300°) corresponds to area V, and (300°, 360°) corresponds to area VI; Then the mechanical angle θ of the rotor is measured by the encoder. e =pθ, p is the number of pole pairs of the switched reluctance motor, which determines the area where the rotor is located.

4. The current prediction control method of a switched reluctance motor based on voltage vector synthesis according to claim 1 is characterized by: In step 3, the specific method of selecting the corresponding voltage vector according to the region where the rotor is located includes: Voltage vector V1~V 12 The switch state variable correspondence table is: The single-phase conduction area is Ⅰ, Ⅲ, Ⅴ, and the two-phase conduction area is Ⅱ, Ⅳ, Ⅵ; when the rotor is in the single-phase conduction area, a single voltage vector V is selected. si and the corresponding zero vector V s0 , in the two-phase conduction region, two voltage vectors V are selected from three candidate voltage vectors through a cost function designed based on the current error. si 、V sj and the corresponding zero vector V s0 ; The correspondence table between the rotor area and the voltage vector to be selected is: For the rotor in the two-phase conduction region, from the three selected voltage vectors and the corresponding zero vector V s0 The two voltage vectors V are selected by a cost function designed based on the current error si 、V sj The specific steps are: Step 3.1: Using the first-order forward Euler discretization method, use the formula Predict the current at time (k+1), where i(k+1) and i(k) are the currents at time k+1 and time k respectively, T s is the sampling period, V p (k),L p (k) are the rotor phase voltage and phase inductance at time k; R, ω r ,θ are the total rotor resistance, speed and mechanical angle respectively; Step 3.2: Cost function expression designed based on given current and predicted current: J=norm(i * -i p (k+1)) 2 +norm(i * -i q (k+1)) 2 Among them: J is the cost function, norm is the second-order norm, i * For a given current, (p,q)∈{(A,B),(B,C),(C,A)},i p (k+1),i q (k+1) are the currents of phases p and q at the moment (k+1); Step 3.3: Select two voltage vectors V from the three candidate voltage vectors through the cost function si 、V sj ; Where: V x ,V y ,V z There are three candidate vectors. First, pq is determined according to the region where the rotor is located. Second, three voltage vectors V are applied according to the correspondence table between the region where the rotor is located and the voltage vector to be selected. x ,V y ,V z , we get three cost functions J1, J2, and J3, and select the voltage vectors corresponding to the two smaller cost functions.

5. The current prediction control method of a switched reluctance motor based on voltage vector synthesis according to claim 1 is characterized by: In step 4, the specific method of determining the duty cycle of the voltage vector according to the given current includes: The voltage vector selected according to the region where the rotor is located in step 3 and the corresponding zero vector act together, and the duty cycle of the voltage vector action is determined by following the given current; The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), and a single candidate voltage vector V is selected according to the area where the rotor is located. si and the corresponding zero vector V s0 Working together, the predicted current at time (k+1) is: i p (k+1)=i p (k)+S i dT s +S0(1-d)T s Where: p∈(A,B,C) d is the voltage vector V si The duty cycle, S i , S0 is to apply V to the conducting phase winding si ,V s0 The rate of change of current after In order to make: i(k+1)=i*, reverse the solution i p (k+1)=i p (k)+S i dT s +S0(1-d)T s Get the d expression: Among them, dot is the dot product operation, norm is the second-order norm; V s =dV si +(1-d)V s0 =dV si Among them, V s is the resultant voltage vector; The rotor is in the two-phase conduction area (II, IV, VI), and the voltage vector V is selected according to the area where the rotor is located. si 、V sj Working together, first of all, Δi pq and S i d1T s +S j (1-d1)T s Phase Coherence: i pq (k+1)=i pq (k)+S i d1T s +S j (1-d1)T s Δi pq =i pq (k+1)-i pq (k) Where: pq∈{AB,BC,CA} In order to make: Δi pq and S i d1T s +S j (1-d1)T s The phases of the two vectors are consistent, that is, the ratio of the components of the two vectors on the xy axis is the same: d1 is the voltage vector V si The weight, S i ,S j To apply voltage vector V to the two phases that are turned on si 、V sj The rate of change of current after Inverse Solution Get the expression of d1: Voltage vector synthesis results: In syn =d1V si +(1-d1)V sj Among them, V syn is the voltage vector V si 、V sj The resultant voltage vector acting together; The resultant voltage vector V syn and zero vector V s0 Working together, the predicted current at time (k+1) is: i pq (k+1)=i pq (k)+S syn d2T s +S0(1-d2)T s in: d2 is the voltage vector V syn The duty cycle, S syn , S0 is the voltage vector V applied to the two phases that are turned on syn ,V s0 The rate of change of current after In order to make: i(k+1)=i*, reverse the solution i pq (k+1)=i pq (k)+S syn dT s +S0(1-d2)T s Get the d2 expression: V s =d2V syn +(1-d2)V s0 =d1d2V si +d2(1-d1)V sj +(1-d2)V s0 Among them, V s is the resultant voltage vector.

6. The current prediction control method of a switched reluctance motor based on voltage vector synthesis according to claim 1 is characterized by: In step 5, the specific method of sending the selected voltage vector action time and the switch signal corresponding to the duty cycle to the asymmetric half-bridge power converter to control the switched reluctance motor includes: The rotor is in the single-phase conduction area (Ⅰ, Ⅲ, Ⅴ), the voltage vector V si and zero vector V s0 The action time T1, T0 is: T s is a switching cycle of an asymmetric half-bridge power converter; The rotor is in the two-phase conduction area (Ⅱ, Ⅳ, Ⅵ), the voltage vector V si ,V sj and zero vector V s0 The action time T2, T1, T0 is:

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