A driving circuit and a control method of a four-level switched reluctance motor

Abstract

The application discloses a kind of four-level switched reluctance motor drive circuit, including T-type single-phase three-level voltage source rectifier and four-level SRM controller, SRM controller is connected with double-output voltage source rectifier, compared with prior art, every phase of SRM controller has two switches and two diodes, two phases are parallel on DC link, and SRM controller does not adopt common switch, so that SRM controller has four working modes, respectively excitation mode, freewheeling mode, one times demagnetization mode and two times voltage demagnetization mode, when SRM is off, it can be switched to two times voltage demagnetization mode, reduce the tailing time of demagnetization current, realize fast demagnetization and improve the driving performance of motor;The application also provides a kind of four-level switched reluctance motor control method.

Description

Technical Field

[0001] This invention relates to the field of motor drive technology, and more specifically to a drive circuit and control method for a four-level switched reluctance motor. Background Technology

[0002] In existing technologies, when a four-level switched reluctance motor operates at high speed, the back electromotive force of the motor increases, while the excitation and demagnetization times per cycle are shortened, making it difficult for the phase current during constant-pressure excitation to reach the desired value. In a four-level switched reluctance motor drive system based on a traditional asymmetric half-bridge converter (AHBC), the traditional operating modes are excitation mode (represented as 1) and demagnetization mode (represented as -1), and the traditional combination of operating modes is as follows: Figure 1a , 1b As shown in Figure 1c, it can be seen that for a four-level switched reluctance motor, due to the high speed after shutdown, the current drops very slowly after shutdown. Therefore, the drag current can easily continue to the inductance drop region. That is, normal voltage demagnetization cannot meet the requirement of rapid phase current drop, thereby reducing the output performance of the motor.

[0003] In view of this, the present invention has been further studied and thus this case came into being. Summary of the Invention

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

[0005] The purpose of this invention is to provide a control method for a four-level switched reluctance motor, which can...

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A drive circuit for a four-level switched reluctance motor includes a T-type single-phase three-level voltage source rectifier and a four-level SRM controller. 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 diodes , The B-phase winding includes a switch. , and diodes , ;

[0008] The switch The collectors of the diodes are respectively connected to the diodes. and the diode The cathode, the switch The emitters are respectively connected to the positive terminal of phase A of the winding and the diode. The negative terminal of the winding A phase is connected to the diode. The positive electrode and the switch The collector of the switch The emitter is connected to the switch The collector of the switch The emitters are respectively connected to the positive terminal of phase B of the winding and the diode. The cathode of the diode The anodes of the diodes are respectively connected to the diodes. The positive electrode and the switch The emitter, the switch The collectors are respectively connected to the negative terminal of phase B of the winding and the diode. The anode; wherein the switch The emitters are respectively connected to the capacitor The negative terminal and the capacitor The positive electrode, the switch The collectors of the capacitors are respectively connected to the capacitors. The negative terminal and the capacitor The positive terminal of the capacitor, and the capacitor The positive terminal is connected to the diode. The cathode, the capacitor The negative terminal is connected to the diode. The anode of the capacitor The negative terminal is connected to the capacitor. The positive pole.

[0009] The switch The switch The switch and the switch All use N-channel IGBTs.

[0010] The four-level switched reluctance motor has four operating modes, namely excitation mode, freewheeling mode, single-voltage demagnetization mode, and double-voltage demagnetization mode.

[0011] The switching of each of the aforementioned operating modes is achieved by controlling the switch. The switch The switch and the switch The on / off state is controlled.

[0012] The drive system includes a position / velocity calculation module, a speed controller, a current feedforward control module, a phase detection module, a capacitor balance controller, and an SVPWM module, as well as the drive circuit as described in any one of claims 1-4; the control method includes the following steps:

[0013] S1. Establish a virtual phase, wherein the variables of the virtual phase are orthogonal to the variables of the single-phase system, and the original network-side variables are in the αβ reference frame. Treated as variables of Axial components, The axis component lags behind its corresponding original network-side variable. If there are two phases, the voltage equation for this virtual two-phase system is as follows:

[0014] (1),

[0015] In the formula, This represents the resistor in the aforementioned drive circuit. This refers to the inductor in the aforementioned drive circuit. yes Grid-side voltage in coordinate system yes Current on the grid side in the coordinate system yes The voltage of the voltage source rectifier in the coordinate system, where... , and Data were acquired through sampling using voltage and current sensors, respectively.

[0016] S2, Park Transformation: The above voltage equation is transformed using the Park transformation as follows:

[0017] (2),

[0018] in, , and In These are mathematical symbols and have no practical meaning. For virtual two-phase orthogonal systems shaft and The included angle of the axis, For the fundamental frequency, For time;

[0019] Substituting expression (2) into expression (1), expression (1) can be transformed into:

[0020] (3),

[0021] In the formula, yes Voltage on the grid side in the coordinate system yes Current on the grid side in the coordinate system Voltage of the voltage source rectifier in the coordinate system;

[0022] S3, to and Decoupling is achieved by using the aforementioned current feedforward control module and defining two intermediate variables. and The expressions for the two intermediate variables are as follows:

[0023] (4),

[0024] (5),

[0025] In equation (4), It is the d-axis component of the grid-side current, as shown in equation (5). It is the q-axis component of the grid-side current. These are the two intermediate variables for current feedforward control. and The speed is obtained respectively through the speed controller;

[0026] Substituting expressions (4) and (5) into expression (3) respectively, the dq reference frame... It can be given by the following formula:

[0027] (6),

[0028] (7),

[0029] In equation (6), It is the d-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side voltage. It is the q-axis component of the grid-side current; in equation (7), It is the q-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side current. It is the q-axis component of the grid-side voltage;

[0030] S4. Obtain the original single phase: [The above...] Transforming back to the αβ reference frame yields The virtual beta phase is discarded, and then The signal is sent to the SVPWM module to output the signal. The voltage source rectifier is supplied with a constant DC bus voltage to the SRM controller.

[0031] After step S4, control and To maintain a constant current and reduce harmonic distortion of the grid-side current, the specific control measures are as follows:

[0032] Based on the Park inverse transform matrix, the original grid-side current ( Transformed into:

[0033] (8),

[0034] In equation (8), The d-axis component of the current in the dq coordinate system The q-axis component of the current in the dq coordinate system, the grid-side current. Obtained by sampling through a current sensor;

[0035] If a virtual orthogonal two-phase system and If all are constants, then The expression is: (9),

[0036] In the formula, = , =arctan( ), It is the current phase. It is the current amplitude.

[0037] With the capacitor and the capacitor The voltage difference between them is The The input is fed into the capacitor balance controller for capacitor balance control, and the capacitor balance controller outputs an influencing factor. f The SVPWM module is adjusted to maintain capacitor balance using the following method:

[0038] Step S5, obtained through step S4 The conversion is as follows:

[0039] (10), where This serves as the voltage reference for the voltage source rectifier.

[0040] Step S6: According to the volt-second balance theory, In a control cycle The function expression is as follows:

[0041] (11);

[0042] In the formula, and These represent the dwell time of the base voltage vector, respectively. The subscripts i and j are both symbols for defining the base vector, and their directions differ by 90° in space.

[0043] The voltage source rectifier has nine switching states, each of which is defined as a switching state vector, and each switching state vector is further defined as follows: There are different effects. and It can be identified To confirm;

[0044] adjust and The expression for the dwell time is:

[0045] (12), among which, , They represent respectively and Execution time;

[0046] Step S7, Evaluation The polarity, then and Based on impact factor f Adjustments will be made.

[0047] With the above circuit, the present invention has the following beneficial effects: By adding an extra switch and a diode to each phase winding circuit in the drive circuit, and connecting the two phases in parallel in the DC link, the four-level switched reluctance motor can achieve four operating modes: excitation mode, freewheeling mode, single-voltage demagnetization mode, and double-voltage demagnetization mode. In this way, when the motor is turned off, the operating mode of the SRM controller is switched to double-voltage demagnetization mode to reduce the tailing time of the demagnetization current of the four-level switched reluctance motor, increase the utilization rate of the inductor rising region, and thus improve the driving performance of the four-level switched reluctance motor.

[0048] By employing the above method, the present invention has the following beneficial effects: In the present invention, the motor speed is directly controlled by... To control this, the output of the speed controller is used as a reference for the d-axis component of the grid-side current. ),because It can be positive or negative, so energy can flow not only from the power grid to the four-level switched reluctance motor, but also back to the power grid, realizing bidirectional energy flow and reducing energy waste. Attached Figure Description

[0049] Figure 1aThis is a schematic diagram of the operation mode of a traditional SRM controller (the arrows indicate the direction of current flow).

[0050] Figure 1b This is a schematic diagram of the second operating mode of a traditional SRM controller (the arrow indicates the direction of current flow).

[0051] Figure 1c This is a schematic diagram of the third operating mode of a traditional SRM controller (the arrows indicate the direction of current flow).

[0052] Figure 2 This is a schematic diagram of the driving circuit used in this invention;

[0053] Figures 3a-3j These are schematic diagrams of the two-phase operation modes in the SRM controller used in this invention (arrows indicate the direction of current flow).

[0054] Figure 4 This is a block diagram illustrating the principle of the control method for the drive system used in this invention.

[0055] Figure 5 This is a schematic diagram of the basis vectors and sector division of the nine basic switching states in the control method proposed in this invention. Detailed Implementation

[0056] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0057] This invention provides a drive circuit for a four-level switched reluctance motor, including a voltage source rectifier (VSR) and an SRM controller; the voltage source rectifier is a conventional T-type single-phase three-level voltage source rectifier, and includes a power supply. ,resistance ,inductance ,capacitance and capacitor and three-level switches , The circuit of this voltage source rectifier adopts the circuit of a conventional T-type single-phase three-level voltage source rectifier, as shown in the figure below. Figure 2 As shown, the capacitor in the voltage source rectifier The negative terminal of the capacitor is connected. The positive terminal, of which, a three-level switch , Each circuit consists of four IGBT switches, and the specific connection circuit is as follows: Figure 2 As shown, the In this case, w can be either a or b.

[0058] The SRM controller of this invention is used to control an SRM motor. It is a four-level SRM controller built on the basis of a conventional split-phase DC-DC converter, connected to a voltage source rectifier with dual output voltages. The four-level SRM controller includes winding phase A and winding phase B. Winding phase A includes a switch. , and diodes , Phase B winding includes a switch. , ,diode , ,switch , and , All use conventional N-channel IGBT transistors; the SRM controller circuit connection is as follows: switch The collectors of the diodes are respectively connected to the diodes. and diodes cathode, switch The emitters are connected to the positive terminal of phase A of the winding and the diode, respectively. The negative terminal of winding A is connected to the diode. Positive electrode and switch collector, switch emitter connection switch collector, switch The emitters are connected to the positive terminal of phase B of the winding and the diode, respectively. cathode, diode The anodes are respectively connected to diodes Positive electrode and switch emitter, switch The collectors are connected to the negative terminal of phase B of the winding and the diode, respectively. The anode.

[0059] The connection circuit between the voltage source rectifier and the SRM controller described above is as follows: switch The emitters are connected to capacitors respectively. negative electrode and capacitor The positive terminal, switch The collectors are respectively connected to capacitors negative electrode and capacitor The positive terminal, and the capacitor The positive terminal of the diode is connected. cathode, capacitor Negative terminal connected to diode The anode.

[0060] In this invention, compared to existing four-level SRM controllers, the four-level SRM controller adds one switch and one diode to each phase winding circuit. Specifically, each phase winding is connected to two switches and two diodes, and the two phases are connected in parallel in the DC link. Furthermore, this SRM controller does not use a common switch. Therefore, the four-level switched reluctance motor can achieve four operating modes: excitation mode, freewheeling mode, single-voltage demagnetization mode, and double-voltage demagnetization mode. The operation modes of these four operating modes in the SRM controller are as follows: Figures 3a-3j The combination method (taking two phases as an example); where, for ease of description, in this embodiment, the excitation mode is denoted as 1, the freewheeling mode as 0, the one-time demagnetization mode as -1, and the two-times voltage demagnetization mode as -2. Figure 3a The two-phase windings of the four-level SRM controller operate 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 operates in the excitation mode, and winding phase B operates in the excitation mode. Figure 3b The four-level SRM controller operates in the (1,0) mode, that is, winding A phase operates in excitation mode and winding B phase operates in freewheeling mode. Figure 3c The four-level SRM controller operates in a (1, -1) mode. Figure 3d The four-level SRM controller operates in the (1, -2) mode. Figure 3e The four-level SRM controller operates in (0,0) mode. Figure 3f The four-level SRM controller operates in the (0, -1) mode. Figure 3g The four-level SRM controller operates in the (0, -2) mode. Figure 3h The four-level SRM controller operates in a (-1, -1) mode. Figure 3i The four-level SRM controller operates in the (-1, -2) mode. Figure 3j The four-level SRM controller operates in a (-2, -2) mode; from Figures 3a-3j As can be seen from the energy loop (i.e. the direction of the arrow), the energy flow of any phase in the four-level SRM controller will not be affected by the operating mode of other phases, thus realizing the independence of phase control.

[0061] It should be noted that the switching of each operating mode of the above-mentioned four-level SRM controller is achieved by switching the switches in the four-level SRM controller. , and switches , On / off state, and the connection of diodes , and , This is achieved by controlling the switches according to the operating status of the SRM motor in the drive circuit. , ,switch and switch The switching on and off of the transistors is controlled by the operating status of the SRM motor to achieve... Figures 3a-3j The energy circuits within are standard operating procedures, so they will not be described in detail here.

[0062] Furthermore, this drive circuit uses conventional single-pulse control (SPC) to control the on / off state of each switch in the aforementioned SRM controller. Taking the double-voltage demagnetization mode as an example, the encoder on the four-level switched reluctance motor sends encoder signals to the position / speed estimator for position and speed calculation. When the motor is in the conduction zone of a certain phase winding (taking phase A as an example), the two switches in the circuit controlling phase A winding are activated. , Simultaneously, phase A is energized; if the motor is not located in the conducting region of phase A winding, then the two switches in the phase A winding circuit... , Simultaneously shutting off phase A results in double demagnetization; this achieves rapid demagnetization of the winding using a double-voltage demagnetization mode; similarly, phase B winding also enters the double-voltage demagnetization mode according to this principle. In addition, a single-voltage demagnetization mode is also used ( In a four-level SRM controller, strict overcurrent protection can be achieved.

[0063] like Figure 3j As shown, control switch , and switches , All are in the off state. At this time, the four-level SRM controller operates in double voltage demagnetization mode, where the energy flow is according to... Figure 3j As indicated by the arrow, the SRM controller's double-voltage demagnetization mode can operate independently, and via -2 The rapid demagnetization accelerates the current drop process, thereby reducing the tail time of the demagnetizing current in the four-level switched reluctance motor, increasing the utilization rate of the inductance rising region, and thus improving the driving performance of the four-level switched reluctance motor.

[0064] In this invention, the drive system of the four-level switched reluctance motor includes the aforementioned drive circuit, as well as 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 / αβ conversion module. In this embodiment, the speed controller described above uses conventional proportional-integral (PI) speed control. All the modules mentioned above are conventional modules in existing drive systems, so they will not be described in detail.

[0065] Furthermore, in this embodiment, each part is respectively arranged according to... Figure 4 The control is performed as shown; in other words, the control method for the four-level switched reluctance motor provided in this embodiment is based on the above-mentioned drive system. Specifically, as shown... Figure 2 As shown and as Figure 4 As shown, the control method includes the following steps:

[0066] 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 frame, the original network-side variables... Treated as variables of Axial components, The axis component lags behind its corresponding original network-side variable. If there are two phases, the voltage equation for this virtual two-phase system is as follows:

[0067] (1),

[0068] In the formula, This represents the resistor in the aforementioned drive circuit. This refers to the inductor in the aforementioned drive circuit. yes Grid-side voltage in coordinate system yes Current on the grid side in the coordinate system yes The voltage of the voltage source rectifier in the coordinate system, wherein, as mentioned above... , and It can be obtained by sampling through voltage and current sensors respectively.

[0069] S2, Park Transformation: The above voltage equation is transformed using the Park transformation as follows:

[0070] (2), , and In These are mathematical symbols and have no practical meaning. For virtual two-phase orthogonal systems shaft and The included angle of the axis, For the fundamental frequency, For time;

[0071] Furthermore, substituting expression (2) into expression (1), expression (1) can be transformed into:

[0072] (3),

[0073] In the formula, yes Voltage on the grid side in the coordinate system yes Current on the grid side in the coordinate system Voltage of the voltage source rectifier in the coordinate system;

[0074] It is worth mentioning that in expression (3) and The existence of coupling increases the design complexity of the controller. Therefore, current feedforward control is used to decouple them, i.e., the following step S3 is adopted; where the coefficients are... express With DC link voltage The ratio between them is given by the formula: ,coefficient This is equivalent to the duty cycle of the current switching signal.

[0075] S3. Decoupling: Using current feedforward control, two intermediate variables are defined. and Two intermediate variables and The expressions are as follows:

[0076] (4),

[0077] (5),

[0078] In equation (4), It is the d-axis component of the grid-side current, as shown in equation (5). It is the q-axis component of the grid-side current. and These are the two intermediate variables for current feedforward control. and The speed is obtained respectively through the speed controller;

[0079] It should be noted that this embodiment takes into account the power correction factor (PFC), therefore the control... =0, to achieve power factor refer to .

[0080] Furthermore, substituting expressions (4) and (5) into expression (3) respectively, the dq reference frame... It can be given by the following formula:

[0081] (6),

[0082] (7),

[0083] In equation (6), It is the d-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side voltage. It is the q-axis component of the grid-side current;

[0084] In equation (7), It is the q-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side current. It is the q-axis component of the grid-side voltage;

[0085] so, It is the d-axis reference for the grid-side current. It is the q-axis reference for the grid-side current, where, combined with Figure 4 As can be seen, after obtaining the speed of the SRM motor in the aforementioned manner, it can be obtained through a conventional speed controller (such as a PI regulator). In other words, The acquisition of [the data] is a conventional technique and will not be described further; in this embodiment, It has always been 0.

[0086] 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.

[0087] S4. Obtain the original single phase: [The above...] Transforming back to the αβ reference frame yields The virtual beta phase is discarded, and then The signal is sent to the Space Vector Pulse Width Modulation (SVPWM) module to make the SVPWM output signal... This is used to control the voltage source rectifier so that it outputs a constant DC bus voltage.

[0088] As a preferred method, after step S4, control and This is a constant to reduce harmonic distortion, as explained below:

[0089] Based on the Park inverse transform matrix, the original grid-side current ( Transformed into:

[0090] (8),

[0091] In equation (8), The d-axis component of the current in the dq coordinate system The q-axis component of the current in the dq coordinate system, the grid-side current. Obtained by sampling through a current sensor.

[0092] The Park inverse transformation matrix is: .

[0093] If a virtual orthogonal two-phase system and If all are constants, then The expression is: (9), where, = , =arctan( ), It is the current phase. It is the current amplitude.

[0094] From equation (9), we can see that For a standard sine curve, that is, by controlling and It is a constant. It can be a sine curve with low harmonic distortion (THD); in addition, this embodiment takes into account the power correction factor (PFC), so the control... =0.

[0095] It should be noted that, as Figure 4 As shown, position / speed calculation, single-pulse control, speed controller control, phase detection, overcurrent protection, and SVPWM control are all implemented using existing technologies applied to motors, so they will not be described in detail here.

[0096] In this invention, the motor speed of the aforementioned four-level switched reluctance motor is directly controlled by... To control, the This represents the d-axis component of the grid-side current; therefore, the speed controller outputs the grid-side current d-axis component as a reference ( ),because The energy can be positive or negative, thus allowing energy to flow not only from the power grid to the four-level switched reluctance motor but also back to the power grid, achieving bidirectional energy flow. Furthermore, this invention employs a decoupling strategy based on current feedforward control to track the energy in the drive system. and Therefore, by decoupling 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 achieves joint control of the front-end VSR and SRM through the above control method.

[0097] To elaborate further, such as Figure 2 As shown and as Figure 5 As shown, the above single-phase three-level VSR has nine switching states. Different rectified voltages are obtained by switching different switching states. For ease of description, nine switching state vectors are defined, each representing the rectifier voltage in the two-dimensional αβ stationary coordinate system, i.e., as shown in the figure. Figure 5 As shown, the state vectors of each switch, i.e., the redundancy vectors, correspond to the following: (1,-1) (1,0) (0,-1) (1,1) (0,0) (-1,-1) (0,1) (-1,0) and (-1,1), where 1, -1 and 0 represent positive voltage, negative voltage and zero voltage, respectively; (S a ,S b In ), S a Connect to positive voltage, S b Connect to a negative voltage, where n is a positive integer and n≥9.

[0098] In this embodiment, a capacitor is used. and capacitor The voltage difference between them is , The input is fed into the capacitor balance controller for capacitor balance control, and the capacitor balance controller outputs the influencing factor. f For the SVPWM module, where the voltage difference is The relationship between the states of each switch and the voltage difference are as follows: The relationship between the impact factor f and the influence factor f is as follows:

[0099] First, the result obtained through step S4 The conversion is as follows: (10), where This serves as the voltage reference for the voltage source rectifier.

[0100] Secondly, according to the volt-second balance theory, In a control cycle The function expression is as follows:

[0101] (11);

[0102] In the formula, and These represent the dwell time of the redundant base voltage vectors, respectively. The subscripts i and j are both symbols for defining the base vectors, and their directions differ by 90° in space. and Both are base voltage vectors; and It can be identified The sector in question determines the location, as shown in Table I. and Both are redundant base voltage vectors. and Both are used for modulation in capacitor balance control.

[0103] Furthermore, , and Substitute into equation (11) for calculation to obtain the execution time of each redundant base voltage vector;

[0104] TABLE Each interval and

[0105]

[0106] Furthermore, for ease of description, each switch state is... The effects are shown in Table II.

[0107] TABLE Base voltage vector pair Impact

[0108]

[0109] As can be seen from the table above, for the same grid-side current Redundant vectors (1,0) and (0, -1) pairs The effects are opposite; redundant vectors (1,0), (0, -1), their pairs The effect is opposite to that of the current i, that is and Redundant vectors (-1,0) and (0,1) Impact and Redundancy Vector (1,0) and (0, -1) are the same; therefore, It depends not only on the switching state, but also on the grid-side current. The polarity of sign ( Therefore, by adjusting the above two pairs of redundant vectors... and The residence time is sufficient to maintain capacitance balance.

[0110] Among them, regulation and The expression for the dwell time is:

[0111] (12), among which, , They represent respectively and Execution time.

[0112] From equation (12) and Table II, it can be seen that if ,but Decrease, if but Increasing f allows for dynamic adjustment, which can effectively maintain the balance of the capacitor without affecting its operation. The modulation does not cause any effect; therefore, in the capacitor balance control of this embodiment, the first evaluation is performed. The polarity, then and Adjust according to f, then output f to the SVPWM module, and combine To obtain the control signal of the VSR. .

[0113] The control method for a four-level switched reluctance motor proposed in this invention integrates the aforementioned single-phase four-level VSR and SRM control into a single control strategy. 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 power supply (PF). This allows the grid-side PF, THD, and motor speed to be adjusted simultaneously. Therefore, the drive system used in this invention is more integrated and simplified than previous drive systems for switched reluctance motors with PFC, achieving centralized control of the drive system. Furthermore, for high-power systems and applications requiring frequent speed adjustments (such as electric locomotives), the control method described in this invention allows energy to flow not only from the grid to the motor but also... Under the regulation of the system, energy flows back to the grid, achieving bidirectional energy flow and reducing energy waste.

[0114] The above description is only a preferred embodiment of this invention. Any equivalent changes and modifications made within the scope of the claims of this invention shall fall within the scope of the claims of this invention.

Claims

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

2. The drive circuit for 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 IGBTs.

3. The drive circuit for a four-level switched reluctance motor according to claim 1, characterized in that: The four-level switched reluctance motor has four operating modes, namely excitation mode, freewheeling mode, single-voltage demagnetization mode, and double-voltage demagnetization mode.

4. The drive circuit for a four-level switched reluctance motor according to claim 3, characterized in that: The switching of each of the aforementioned operating modes is achieved by controlling the switch. The switch The switch and the switch The on / off state is controlled.

5. A control method for a four-level switched reluctance motor, based on a drive system for the four-level switched reluctance motor, characterized in that, The drive system includes a position / velocity calculation module, a speed controller, a current feedforward control module, a phase detection module, a capacitor balance controller, and an SVPWM module, as well as the drive circuit as described in any one of claims 1-4; the control method includes the following steps: S1. Establish a virtual phase, wherein the variables of the virtual phase are orthogonal to the variables of the single-phase system, and the original network-side variables are in the αβ reference frame. Treated as variables of Axial components, The axis component lags behind its corresponding original network-side variable. If there are two phases, the voltage equation for the virtual two-phase system is as follows: （1）， In the formula, This represents the resistor in the aforementioned drive circuit. This refers to the inductor in the aforementioned drive circuit. yes Grid-side voltage in coordinate system yes Current on the grid side in the coordinate system yes The voltage of the voltage source rectifier in the coordinate system, where... , and Data were acquired through sampling using voltage and current sensors, respectively. S2, Park Transform: The above voltage equation is transformed using the Park transformation as follows: （2）， in, , and In These are mathematical symbols and have no practical meaning. For virtual two-phase orthogonal systems shaft and The included angle of the axis, For the fundamental frequency, For time; Substituting expression (2) into expression (1), expression (1) becomes: （3）， In the formula, yes Grid-side voltage in coordinate system yes Current on the grid side in the coordinate system Voltage of the voltage source rectifier in the coordinate system; S3, to and Decoupling is achieved by using the aforementioned current feedforward control module and defining two intermediate variables. and The expressions for the two intermediate variables are as follows: （4）， （5）， In equation (4), It is the d-axis component of the grid-side current, as shown in equation (5). It is the q-axis component of the grid-side current. These are the two intermediate variables for current feedforward control. and The speed is obtained respectively through the speed controller; Substituting expressions (4) and (5) into expression (3) respectively, the dq reference frame... It can be given by the following formula: （6）， （7）， In equation (6), It is the d-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side voltage. It is the q-axis component of the grid-side current; in equation (7), It is the q-axis component of the voltage source rectifier voltage. It is the d-axis component of the grid-side current. It is the q-axis component of the grid-side voltage; S4. Obtain the original single phase: [The above...] Transforming back to the αβ reference frame yields The virtual beta phase is discarded, and then The signal is sent to the SVPWM module to output the signal. The voltage source rectifier is supplied with a constant DC bus voltage to the SRM controller.

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

7. The control method for a four-level switched reluctance motor according to claim 5, characterized in that: With the capacitor and the capacitor The voltage difference between them is The The input is fed into the capacitor balance controller for capacitor balance control, and the capacitor balance controller outputs an influencing factor. f The SVPWM module is adjusted to maintain capacitor balance using the following method: Step S5, obtained through step S4 The conversion is as follows: (10), where This serves as the voltage reference for the voltage source rectifier. Step S6: According to the volt-second balance theory, In a control cycle The function expression is as follows: （11）； In the formula, and These represent the dwell time of the base voltage vector, respectively. The subscripts i and j are both symbols for defining the base vector, 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, and each switching state vector corresponds to the voltage source rectifier. There are different effects. and It can be identified To confirm; adjust and The expression for the dwell time is: (12), among which, , They represent respectively and Execution time; Step S7, Evaluation The polarity, then and Based on impact factor f Adjustments will be made.

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