Driving circuit of four-level switched reluctance motor and control method thereof

Abstract

The invention discloses a driving circuit of a four-level switched reluctance motor, which comprises a T-type single-phase three-level voltage source rectifier and a four-level SRM controller, the SRM controller is connected with the voltage source rectifier with double outputs, compared with the prior art, each phase of the SRM controller is provided with two switches and two diodes, the two phases are connected in parallel on a direct current link, and the two switches are connected in parallel with the diodes. The SRM controller does not adopt a common switch, so that the SRM controller has four working modes, namely an excitation mode, a follow current mode, a double demagnetization mode and a double-voltage demagnetization mode, when the SRM is turned off, the double-voltage demagnetization mode can be switched, the trailing time of demagnetization current is shortened, rapid demagnetization is realized, and the driving performance of the motor is improved; the invention further provides a control method of the four-level switched reluctance motor.

Description

Technical Field

[0001] The present invention relates to the technical field of motor driving, and more specifically to a driving circuit of a four-level switched reluctance motor and a control method thereof. Background Art

[0002] In the prior art, when the four-level switched reluctance motor runs at high speed, the back electromotive force of the motor increases, and the excitation and demagnetization time of each cycle is shortened, so it is difficult for the phase current to reach the expected value during normal voltage excitation. In the four-level switched reluctance motor drive system based on the traditional asymmetric half-bridge converter (AHBC), the traditional operation modes are the excitation mode (expressed as 1) and the demagnetization mode (expressed as -1). The traditional operation mode combination is as follows: Figure 1a , 1b As shown in Figure 1c, for the four-level switched reluctance motor, due to the high speed after shutdown, the current drops very slowly after shutdown, so the drag current can easily continue to the inductance drop region, that is, normal voltage demagnetization is difficult to meet the requirement of rapid drop of phase current, thereby reducing the output performance of the motor.

[0003] In view of this, the inventor conducted in-depth research on this basis, and thus the present case was produced. Summary of the invention

[0004] The object of the present invention is to provide a driving circuit for a four-level switched reluctance motor, which can reduce the tail time of the demagnetization current and improve the driving performance of the motor.

[0005] The purpose of the present invention is to provide a control method for a four-level switched reluctance motor, which can To achieve the above object, the solution of the present invention is: A four-level switched reluctance motor drive circuit includes a T-type single-phase three-level voltage source rectifier and a four-level SRM controller, wherein the voltage source rectifier includes a capacitor and capacitor The SRM controller includes an A-phase winding and a B-phase winding, wherein the A-phase winding includes a switch , and diode , , the B-phase winding includes a switch , and diode , ; The switch The collectors of the diodes are connected and the diode The cathode of the switch The emitter of the diode is connected to the positive electrode of the winding A phase and the The negative electrode of the winding A phase is connected to the diode The positive terminal and the switch The collector of the switch The emitter of the switch is connected The collector of the switch The emitter of the diode is connected to the positive electrode of the winding B phase and The cathode of the diode The anodes of the diodes are connected The positive terminal and the switch The emitter of the switch The collector of the diode is connected to the negative electrode of the winding B phase and anode; wherein the switch The emitter of the capacitor is connected to The negative electrode and the capacitor The positive terminal of the switch The collectors of the capacitors are connected The negative electrode and the capacitor The positive terminal of the capacitor The positive terminal of the diode is connected The cathode of the capacitor The cathode of the diode is connected The anode of the capacitor The negative terminal of the capacitor is connected to The positive electrode.

[0006] The switch , the switch , the switch and the switch All use N-channel IGBT tubes.

[0007] The four-level switched reluctance motor has four working modes, which are respectively an excitation mode, a freewheeling mode, a one-time demagnetization mode and a two-times-voltage demagnetization mode.

[0008] The switching of each working mode is respectively performed by controlling the switch , the switch , the switch and the switch The on-off is carried out.

[0009] The drive system comprises a position / speed calculation module, a speed controller, a current feedforward control module, a phase detection module, a capacitor balance controller and an SVPWM module and a drive circuit as claimed in any one of claims 1 to 4; the control method comprises the following steps: S1. Establish a virtual phase, the variables of which are orthogonal to the variables of the single-phase system. In the αβ reference system, the original grid-side variables Treated as a variable of Axis component, The axis component lags behind its corresponding original network-side variable phases, the voltage equation of the virtual two-phase system is as follows: (1), In the formula, represents the resistance in the above drive circuit, represents the inductance in the above drive circuit, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: yes The voltage source rectifier voltage in the coordinate system, where , and The voltage and current are sampled and acquired respectively; S2, Park conversion, the above voltage equation is transformed into: (2), in, , and In It is a mathematical symbol and has no practical meaning; For a virtual two-phase orthogonal system Axis and The angle of the axis, is the fundamental frequency, For time; Substituting expression (2) into expression (1), expression (1) can be transformed into: (3), In the formula, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: The voltage source rectifier voltage in the coordinate system; S3, yes and Decoupling: Using the current feedforward control module, define two intermediate variables and , the expressions of the two intermediate variables are as follows: (4), (5), In formula (4), is the d-axis component of the grid-side current, formula (5) is the q-axis component of the grid-side current, are two intermediate variables of current feedforward control, and are respectively obtained through the speed controller; Substituting expressions (4) and (5) into expression (3), we can get It can be given by the following formula: (6), (7), In formula (6), is the d-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side voltage, is the q-axis component of the grid-side current; in formula (7), is the q-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side current, is the q-axis component of the grid-side voltage; S4. Obtain the original single phase: Transforming back to the αβ reference frame, we get , the virtual β phase is discarded, and then sent to the SVPWM module to output a signal to the voltage source rectifier so that it outputs a constant DC bus voltage to the SRM controller.

[0010] After step S4, control and Constant to reduce the harmonic distortion of the grid-side current. The specific control is as follows: Based on the Park inverse transformation matrix, the original grid-side current ( ) is transformed into: (8), In formula (8), The d-axis component of the current in the dq coordinate system is: is the q-axis component of the current in the dq coordinate system, and the grid-side current Obtained through current sensor sampling; If the virtual orthogonal two-phase system and are all constants, then The expression is: (9), In the formula, = , =arctan( ), is the current phase, is the current amplitude.

[0011] With the capacitor and the capacitor The voltage difference between , The capacitor balance controller outputs the influencing factor f To the SVPWM module, wherein the capacitor balance is maintained by adjusting as follows: Step S5: calculated in step S4 The conversion is as follows: (10), where is the voltage reference for the voltage source rectifier; Step S6: According to the volt-second balance theory, In a control cycle The action expression is as follows: (11); In the formula, and They represent the residence time of the base voltage vector respectively, and the subscripts i and j are the symbols of the base vectors, and their directions differ by 90° in space; The voltage source rectifier has nine switching states, each of which is defined as a switching state vector. There are different impacts, and Can be identified by to determine; adjust and The expression for the residence time is: (12), where , They respectively represent and Execution time; Step S7: Evaluation The polarity, then and According to the impact factor f Make adjustments.

[0012] After adopting the above circuit, the present invention has the following beneficial effects: the present invention adds one more switch and one more diode in each phase winding loop in the driving circuit, and the two phases are connected in parallel in the DC link, so that the four-level switched reluctance motor can realize four working modes, namely, the excitation mode, the freewheeling mode, the one-time demagnetization mode and the two-times voltage demagnetization mode. In this way, when the motor is turned off, the operation mode of the SRM controller is switched to the two-times voltage demagnetization mode to reduce the tail time of the demagnetization current of the four-level switched reluctance motor, increase the utilization rate of the inductance rise zone, and thus improve the driving performance of the four-level switched reluctance motor.

[0013] After adopting the above method, the present invention has the following beneficial effects: the motor speed is directly controlled by To control, so that the output of the speed controller is the reference of the d-axis component of the grid-side current ( ),because It can be positive or negative, so energy can not only flow from the grid to the four-level switched reluctance motor, but also flow back to the grid, realizing bidirectional energy flow and reducing energy waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1a Schematic diagram of the operation mode 1 of the traditional SRM controller (the direction of the arrow is the current flow direction); Figure 1b Schematic diagram of the second operation mode of the traditional SRM controller (the direction of the arrow is the current flow direction); Figure 1c Schematic diagram of the third operation mode of the traditional SRM controller (the direction of the arrow is the current flow direction); Figure 2 A schematic diagram of a driving circuit used in the present invention; Figure 3a-3j They are schematic diagrams of the operation modes of the two phases in the SRM controller adopted by the present invention (the direction of the arrows indicates the current flow direction); Figure 4 This is a principle block diagram of the control method of the drive system adopted by the present invention; Figure 5 Schematic diagram of basis vectors and sector division of nine basic switch states in the control method proposed in the present invention. DETAILED DESCRIPTION

[0015] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0016] The present invention provides a driving circuit of a four-level switched reluctance motor, comprising a voltage source rectifier (VSR) and an SRM controller; the voltage source rectifier adopts a conventional T-type single-phase three-level voltage source rectifier, and the voltage source rectifier comprises a power supply ,resistance ,inductance ,capacitance and capacitor And three-level switch , The circuit of the voltage source rectifier adopts the circuit of the conventional T-type single-phase three-level voltage source rectifier. Figure 2 As shown, the capacitor in the voltage source rectifier The negative terminal of the capacitor is connected The positive pole of the three-level switch , They are composed of four IGBT switches respectively. The specific connection circuit is as follows Figure 2 As shown, the Where w can be a or b.

[0017] The SRM controller of the present invention is used to control the SRM motor. A four-level SRM controller is constructed on the basis of a conventional split-term DC converter to connect a voltage source rectifier with dual output voltages. The four-level SRM controller includes a winding A phase and a winding B phase. The winding A phase includes a switch , and diode , , winding B phase including switch , ,diode , ,switch , and , Conventional N-channel IGBT tubes are used; the circuit connection of the SRM controller is: switch The collectors of the diodes are connected and diode The cathode of the switch The emitter of the diode is connected to the positive pole of winding A phase and The negative pole of winding A phase is connected to the diode The positive pole and switch The collector of the switch The emitter connection switch The collector of the switch The emitter of the diode is connected to the positive electrode of winding B phase and The cathode of the diode The anodes of the diodes are connected The positive pole and switch The emitter of the switch The collector of the winding is connected to the negative electrode of the B phase and the diode anode.

[0018] The connection circuit between the voltage source rectifier and the SRM controller is: switch The emitter of The negative electrode and capacitor The positive pole of the switch The collectors of The negative electrode and capacitor The positive electrode of the capacitor The positive terminal of the diode is connected The cathode of the capacitor The cathode of the diode is connected anode.

[0019] In the present invention, compared with the existing four-level SRM controller, the four-level SRM controller adds one more switch and one more diode in each phase winding loop, that is, each phase winding is connected with two switches and two diodes respectively, and the two phases are connected in parallel in the DC link, and the SMR controller does not use a common switch, so the four-level switched reluctance motor can realize four working modes, namely, excitation mode, freewheeling mode, one-time demagnetization mode and two-time voltage demagnetization mode. The operation modes of the four working modes in the SRM controller are as follows Figure 3a-3j Combination of (taking two phases as an example); where, for the convenience of description, in this embodiment, the excitation mode is recorded as 1, the freewheeling mode is recorded as 0, the one-fold demagnetization mode is recorded as -1, and the two-fold voltage demagnetization mode is recorded as -2, then Figure 3a The two-phase windings of the four-level SRM controller work in the (1,1) operation mode, the first part is the working mode of winding phase A, and the second part is the working mode of winding phase B, that is, winding phase A works in the excitation mode, and winding phase B works in the excitation mode; Figure 3b The four-level SRM controller works in the (1,0) operation mode, that is, the winding A phase works in the excitation mode and the winding B phase works in the freewheeling mode; Figure 3c The four-level SRM controller works in the (1, -1) operation mode. Figure 3d The four-level SRM controller works in the (1, -2) operation mode. Figure 3e The four-level SRM controller works in the (0,0) operation mode. Figure 3f The four-level SRM controller works in the (0, -1) operation mode. Figure 3g The four-level SRM controller works in the (0, -2) operation mode. Figure 3hThe four-level SRM controller works in the (-1,-1) operation mode. Figure 3i The four-level SRM controller works in the (-1, -2) operation mode. Figure 3j The four-level SRM controller works in the (-2,-2) operation mode; Figure 3a-3j From the energy loop in (i.e., the direction of the arrow), it can be seen that the energy flow of any phase in the four-level SRM controller will not be affected by the operation mode of other phases, thus achieving phase-to-phase control independence.

[0020] It should be noted that the switching of each operation mode of the above four-level SRM controller is respectively controlled by switching on the switch in the four-level SRM controller. , and switch , The on-off and combined diode , and , Implementation, wherein, in combination with the operating state of the SRM motor in the drive circuit, the switches are controlled separately , ,switch and switch The on and off of each switch tube is controlled by the operating status of the SRM motor to achieve Figure 3a-3j The energy circuit in this example is a routine operation, so I will not elaborate on it.

[0021] Furthermore, the conventional single pulse control (SPC) is used in the present drive circuit to control the on and off of each switch in the above-mentioned SRM controller. Taking the double voltage demagnetization mode as an example, the encoder on the four-level switched reluctance motor sends the encoder signal to the position / speed estimator to calculate the position and speed. When the motor is located in the conduction area of ​​a certain phase winding (taking phase A as an example), the two switches in the loop of the phase A winding are controlled. , At the same time, phase A is energized; if the motor is not in the conduction area of ​​phase A winding, the two switches in the loop of phase A winding , At the same time, the A phase is demagnetized twice. In this way, the winding is demagnetized quickly by applying the double voltage demagnetization mode. Similarly, the B phase winding also enters the double voltage demagnetization mode according to this principle. In addition, the single voltage demagnetization mode ( ) In the four-level SRM controller, strict over-current protection can be achieved.

[0022] like Figure 3j As shown, the control switch , and switch , All are in the off state. At this time, the operation mode of the four-level SRM controller is the double voltage demagnetization mode, in which the energy flow is based on Figure 3j The double voltage demagnetization mode of the SRM controller can operate independently and can be controlled by -2 The rapid demagnetization is used to accelerate the current decline process, so as to reduce the tail time of the demagnetization current of the four-level switched reluctance motor, increase the utilization rate of the inductance rising area, and thus improve the driving performance of the four-level switched reluctance motor.

[0023] In the present invention, the driving system of the four-level switched reluctance motor includes the aforementioned driving circuit and an overcurrent protection module, a single pulse control module, a position / speed calculation module, a speed controller, a current feedforward control module, a phase detection module, a capacitor balance controller, a vector pulse width modulation (SVPWM) module and dq In this embodiment, the speed controller adopts the conventional speed proportional integral (PI) control method, and the above modules are conventional modules in the existing drive system, so they will not be described in detail.

[0024] Furthermore, in this embodiment, each part is respectively Figure 4 In other words, the control method of the four-level switched reluctance motor provided in this embodiment is based on the above-mentioned drive system. Specifically, Figure 2 As shown and Figure 4 As shown, the control method includes the following steps: S1. Establish a virtual phase. The variables of the virtual phase are orthogonal to the variables of the single-phase system. In the αβ reference system, the original grid-side variables Treated as a variable of Axis component, The axis component lags behind its corresponding original network-side variable phases, the voltage equation of the virtual two-phase system is as follows: (1), In the formula, represents the resistance in the above drive circuit, represents the inductance in the above drive circuit, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: yes The voltage source rectifier voltage in the coordinate system, where the above , and It can be obtained by sampling through voltage and current sensors respectively.

[0025] S2, Park conversion, the above voltage equation is transformed into: (2), , and In It is a mathematical symbol and has no practical meaning; For a virtual two-phase orthogonal system Axis and The angle of the axis, is the fundamental frequency, For time; Furthermore, by substituting expression (2) into expression (1), expression (1) can be transformed into: (3), In the formula, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: The voltage source rectifier voltage in the coordinate system; It is worth mentioning that in expression (3) and There is coupling between them, which increases the design complexity of the controller. Therefore, current feedforward control is used to decouple, that is, the following step S3 is adopted; where the coefficient express and DC link voltage The ratio between them is: ,coefficient Equivalent to the duty cycle of the current switching signal.

[0026] S3, decoupling, using current feedforward control, defining two intermediate variables and , two intermediate variables and The expressions are as follows: (4), (5), In formula (4), is the d-axis component of the grid-side current, formula (5) is the q-axis component of the grid-side current, and are two intermediate variables of current feedforward control, and are respectively obtained through the speed controller; It should be noted that in this embodiment, the power correction factor (PFC) is taken into consideration, so the control =0 to achieve power factor refer to .

[0027] Furthermore, by substituting expressions (4) and (5) into expression (3), we can obtain It can be given by the following formula: (6), (7), In formula (6), is the d-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side voltage, is the q-axis component of the grid-side current; In formula (7), is the q-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side current, is the q-axis component of the grid-side voltage; so, is the d-axis reference of the grid-side current, is the q-axis reference of the grid-side current, where, combined with Figure 4 It can be seen that after obtaining the speed of the SRM motor in the above way, it can be obtained through a conventional speed controller (such as a PI regulator) In other words, The acquisition of is an existing conventional technology, so it will not be described in detail; in this embodiment, Always 0.

[0028] It is worth mentioning that in this step, by controlling and By keeping the current constant, the harmonic distortion (THD) of the grid-side current in the drive system can be reduced.

[0029] S4. Obtain the original single phase: Transforming back to the αβ reference frame, we get , the virtual β phase is discarded, and then Sent to the space vector pulse width modulation (SVPWM) module to make the SVPWM output signal , to control the voltage source rectifier so that it outputs a constant DC bus voltage.

[0030] As a preferred method, after step S4, control and is a constant to reduce harmonic distortion. The specific instructions are as follows: Based on the Park inverse transformation matrix, the original grid-side current ( ) is transformed into: (8), In formula (8), The d-axis component of the current in the dq coordinate system is: is the q-axis component of the current in the dq coordinate system, and the grid-side current Obtained through current sensor sampling.

[0031] Among them, the Park inverse transformation matrix is: .

[0032] If the virtual orthogonal two-phase system and are all constants, then The expression is: (9), where = , =arctan( ), is the current phase, is the current amplitude.

[0033] From formula (9), we can see that is a standard sinusoidal curve, that is, by controlling and is a constant, It can be a sine curve with low harmonic distortion (THD); in addition, in this embodiment, the power correction factor (PFC) is taken into consideration, so the control =0.

[0034] It should be noted that if Figure 4 As shown, position / speed calculation, single pulse control, speed controller control, phase detection, overcurrent protection and SVPWM control are all implemented by existing technical means applied to motors, so they are not described in detail.

[0035] In the present invention, the motor speed of the above-mentioned four-level switched reluctance motor is directly controlled by To control, the Represents the d-axis component of the grid-side current, so the speed controller outputs the reference of the d-axis component of the grid-side current ( ),because It can be positive or negative, so energy can not only flow from the grid to the four-level switched reluctance motor, but also flow back to the grid, realizing bidirectional energy flow. In addition, the present invention adopts a decoupling strategy based on current feedforward control to track the current in the drive system. and Therefore, through the decoupling control of the grid-side current, the motor speed, grid-side PFC and grid-side THD in the drive system can be adjusted simultaneously. In other words, the present invention realizes the joint control of the front-end VSR and SRM through the above control method.

[0036] Further, if Figure 2 As shown and Figure 5 As shown, there are nine switch states in the single-phase three-level VSR. Different rectifier voltages are obtained by switching different switch states. For the convenience of description, nine switch state vectors are defined. Each switch state vector represents the rectifier voltage in the two-dimensional αβ stationary coordinate system, that is, Figure 5 As shown, each switch state vector, that is, the redundant vector, corresponds to: (1,-1), (1,0), (0,-1), (1,1), (0,0), (-1,-1), (0,1), (-1,0) and (-1,1), 1, -1 and 0 represent positive voltage, negative voltage and zero voltage respectively; (S a ,S b ), S a Connect to positive voltage, S b Connect to negative voltage, n is a positive integer, n≥9.

[0037] In this embodiment, the capacitor and capacitor The voltage difference between , Input to the capacitor balance controller for capacitor balance control, the capacitor balance controller outputs the influencing factor f To the SVPWM module, the voltage difference is The relationship between the switch states and the voltage difference is The relationship with the impact factor f is as follows: First, the value calculated in step S4 is The conversion is as follows: (10), where is the voltage reference for the voltage source rectifier; Secondly, according to the volt-second balance theory, In a control cycle The action expression is as follows: (11); In the formula, and They represent the residence time of the redundant base voltage vectors, respectively. The subscripts i and j are the symbols of the defined base vectors, and their directions differ by 90° in space. and They are all base voltage vectors; and Can be identified by The sector where the is located is determined, as shown in Table Ⅰ. and are redundant base voltage vectors, redundant base voltage vectors and Both are used for modulation of capacitor balance control.

[0038] Further, , and Substitute into equation (11) to calculate and obtain the execution time of each redundant base voltage vector; TABLE Each interval and

[0039]

[0040] Further, for the convenience of description, each switch state is The impact of is shown in Table II.

[0041] TABLE Base voltage vector pair Impact

[0042] From the above table, we can see that for the same grid-side current , redundant vector (1,0) and (0,-1) pairs The effect is opposite; redundant vector (1,0), (0, -1), its The effect of is opposite to that of current i, that is and ; Redundant vector (-1,0) and (0,1) pair The influence of redundancy vector (1,0) and (0, -1) are the same; therefore, Depends not only on the switch state, but also on the grid current The polarity of sign( ), so by adjusting the above two pairs of redundant vectors and The capacitance balance can be maintained by a dwell time of

[0043] Among them, regulation and The expression for the residence time is: (12), where , They represent and Execution time.

[0044] From formula (12) and Table II, we can see that if ,but Reduce, if but The dynamic adjustment of f can effectively maintain the balance of capacitors without affecting Therefore, in the capacitor balance control of this embodiment, first evaluate The polarity, then and Adjust according to f respectively, and then output f to the SVPWM module, combined with , to get the control signal of VSR .

[0045] The control method of the four-level switched reluctance motor proposed in the present invention integrates the control of the single-phase four-level VSR and SRM into a control strategy, wherein the d-axis of the grid-side current controls the SRM speed, and the q-axis of the grid-side current controls the grid-side PF, so that the grid-side PF, THD and motor speed can be adjusted at the same time, so that the drive system adopted by the present invention is more integrated and simplified than the drive system of the switched reluctance motor with PFC in the past, and the centralized control of the drive system is realized; and for high-power systems, in application scenarios that require frequent speed regulation (such as electric locomotives), by adopting the control method of the present invention, energy can not only flow from the grid to the motor, but also Under the regulation of the grid, the energy flows back to the grid, realizing the two-way flow of energy and reducing energy waste.

[0046] The above description is only a preferred embodiment of the present embodiment, and all equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A driving circuit for a four-level switched reluctance motor, characterized in that: The invention comprises a T-type single-phase three-level voltage source rectifier and a four-level SRM controller, wherein the voltage source rectifier comprises a capacitor and capacitor The SRM controller includes an A-phase winding and a B-phase winding, wherein the A-phase winding includes a switch , and diode , , the B-phase winding includes a switch , and diode , ; The switch The collectors of the diodes are connected and the diode The cathode of the switch The emitter of the diode is connected to the positive electrode of the winding A phase and the The negative electrode of the winding A phase is connected to the diode The positive terminal and the switch The collector of the switch The emitter of the switch is connected The collector of the switch The emitter of the diode is connected to the positive electrode of the winding B phase and The cathode of the diode The anodes of the diodes are connected The positive terminal and the switch The emitter of the switch The collector of the diode is connected to the negative electrode of the winding B phase and anode; wherein the switch The emitter of the capacitor is connected to The negative electrode and the capacitor The positive terminal of the switch The collectors of the capacitors are connected The negative electrode and the capacitor The positive terminal of the capacitor The positive terminal of the diode is connected The cathode of the capacitor The cathode of the diode is connected The anode of the capacitor The negative terminal of the capacitor is connected to The positive electrode.

2. The driving circuit of a four-level switched reluctance motor according to claim 1, characterized in that: The switch , the switch , the switch and the switch All use N-channel IGBT tubes.

3. The driving circuit of a four-level switched reluctance motor according to claim 1, characterized in that: The four-level switched reluctance motor has four working modes, which are respectively an excitation mode, a freewheeling mode, a one-time demagnetization mode and a two-times-voltage demagnetization mode.

4. The driving circuit of a four-level switched reluctance motor according to claim 3, characterized in that: The switching of each working mode is respectively performed by controlling the switch , the switch , the switch and the switch The on-off is carried out.

5. A control method for a four-level switched reluctance motor, based on a drive system of a four-level switched reluctance motor, characterized in that: The drive system comprises a position / speed calculation module, a speed controller, a current feedforward control module, a phase detection module, a capacitor balance controller and an SVPWM module and a drive circuit as claimed in any one of claims 1 to 4; the control method comprises the following steps: S1. Establish a virtual phase, the variables of which are orthogonal to the variables of the single-phase system. In the αβ reference system, the original grid-side variables Treated as a variable of Axis component, The axis component lags behind its corresponding original network-side variable phases, the voltage equation of the virtual two-phase system is as follows: （1）， In the formula, represents the resistance in the above drive circuit, represents the inductance in the above drive circuit, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: yes The voltage source rectifier voltage in the coordinate system, where , and The voltage and current are sampled and acquired respectively; S2, Park conversion, the above voltage equation is transformed into: （2）， in, , and In It is a mathematical symbol and has no practical meaning; For a virtual two-phase orthogonal system Axis and The angle of the axis, is the fundamental frequency, For time; Substituting expression (2) into expression (1), expression (1) can be transformed into: （3）， In the formula, yes The grid voltage in the coordinate system is: yes The grid-side current in the coordinate system is: The voltage source rectifier voltage in the coordinate system; S3, yes and Decoupling: Using the current feedforward control module, define two intermediate variables and , the expressions of the two intermediate variables are as follows: （4）， （5）， In formula (4), is the d-axis component of the grid-side current, formula (5) is the q-axis component of the grid-side current, are two intermediate variables of current feedforward control, and are respectively obtained through the speed controller; Substituting expressions (4) and (5) into expression (3), we can get It can be given by the following formula: （6）， （7）， In formula (6), is the d-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side voltage, is the q-axis component of the grid-side current; in formula (7), is the q-axis component of the voltage source rectifier voltage, is the d-axis component of the grid-side current, is the q-axis component of the grid-side voltage; S4. Obtain the original single phase: Transforming back to the αβ reference frame, we get , the virtual β phase is discarded, and then sent to the SVPWM module to output a signal to the voltage source rectifier so that it outputs a constant DC bus voltage to the SRM controller.

6. A driving circuit for a four-level switched reluctance motor according to claim 5, characterized in that: After step S4, control and Constant to reduce the harmonic distortion of the grid-side current. The specific control is as follows: Based on the Park inverse transformation matrix, the original grid-side current ( ) is transformed into: （8）， In formula (8), The d-axis component of the current in the dq coordinate system is, is the q-axis component of the current in the dq coordinate system, the grid-side current Obtained through current sensor sampling; If the virtual orthogonal two-phase system and are all constants, then The expression is: (9), In the formula, = , =arctan( ), is the current phase, is the current amplitude.

7. The driving circuit of a four-level switched reluctance motor according to claim 5, characterized in that: With the capacitor and the capacitor The voltage difference between , The capacitor balance controller outputs the influencing factor f To the SVPWM module, wherein the capacitor balance is maintained by adjusting as follows: Step S5: calculated in step S4 The conversion is as follows: (10), where is the voltage reference for the voltage source rectifier; Step S6: According to the volt-second balance theory, In a control cycle The action expression is as follows: （11）； In the formula, and They represent the residence time of the base voltage vector respectively, and the subscripts i and j are the symbols of the base vectors, and their directions differ by 90° in space; The voltage source rectifier has nine switching states, each of which is defined as a switching state vector. There are different impacts, and Can be identified by to determine; adjust and The expression for the residence time is: (12), where , They respectively represent and Execution time; Step S7: Evaluation The polarity, then and According to the impact factor f Make adjustments.

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