CN113131804B - A three-switch converter topology and control strategy for switched reluctance motors - Google Patents

Abstract

The invention relates to the technical field of motors, and provides a topology and a control strategy of a three-switch converter for a switched reluctance motor. The proposed three-switch converter topology can realize bipolar operation of current, and has 8 operation modes such as a forward excitation mode, a forward upper tube zero-voltage follow current mode, a forward lower tube zero-voltage follow current mode, a forward negative voltage follow current mode, a reverse excitation mode, a reverse upper tube zero-voltage follow current mode, a reverse lower tube zero-voltage follow current mode and a reverse negative voltage follow current mode. Meanwhile, the magnetic circuit balance control method can eliminate the phenomenon of asymmetric magnetic circuits of the switched reluctance motor with even phases, realize the balance control of the magnetic circuits and improve the operation efficiency of the system. Compared with a conventional asymmetric half-bridge power converter for driving the switched reluctance motor, the power converter can reduce the using number of power semiconductor devices, does not need to increase passive devices such as inductors, capacitors and the like, and has good engineering application value.

Description

A three-switch converter topology and control strategy for switched reluctance motors

technical field

The invention relates to the technical field of motors, in particular to a topology and control strategy of a three-switch converter for a switched reluctance motor.

Background technique

Switched reluctance motor has the advantages of simple structure, low manufacturing cost and strong fault tolerance, and has become an important choice for driving motors in new energy vehicles, wind power generation, coal mining and intelligent manufacturing equipment. However, due to the absence of rare earth and the doubly salient structure, the SRM also has disadvantages such as low power density, large torque ripple and low efficiency, and the reliability problems brought about by the above shortcomings have hindered the large-scale SRM system. major barriers to adoption and development. To overcome the above shortcomings, it is necessary to explore new low-cost and high-reliability power converter topologies. Low-cost converter topologies in existing research mainly include Miller converters, m-switch converters, C-dump converters and R-dump converters, etc., but these topologies often bring about the decline of control performance and fault tolerance. For example, the m-switch converter can reduce the number of power devices used, but the fault tolerance is significantly reduced compared to the asymmetric half-bridge power converter. At the same time, the existing fault-tolerant power converters for switched reluctance motors often need to add power semiconductor devices, especially the distributed fault-tolerant power converter topology requires two controllable switches and two diodes for each pole, which greatly increases the system cost. At the same time, the existing power converter topologies cannot solve the problem of magnetic circuit imbalance of even-phase switched reluctance motors. Therefore, in order to improve the operating performance of the system, it is urgent to develop a low-cost and high-reliability high-performance power converter topology.

SUMMARY OF THE INVENTION

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

Therefore, an object of the present invention is to propose a three-switch converter topology and control strategy for a switched reluctance motor, so as to reduce the number of components used and system cost, and improve fault tolerance and long-distance travel efficiency. and power density to achieve balanced operation of the magnetic circuit.

To achieve the above objective, an embodiment of the present invention provides a topology and control strategy of a three-switch converter for a switched reluctance motor. In the proposed three-switch converter, each bridge arm is composed of three controllable switches with built-in diodes, and each phase winding is connected to the upper and lower nodes of the adjacent bridge arms, which can drive any phase switched reluctance motor.

Description of working principle: The proposed three-switch converter topology can realize the bipolar operation of the current, with positive excitation mode, positive upper tube zero-voltage freewheeling mode, positive lower tube zero-voltage freewheeling mode, and forward negative voltage. There are 8 operating modes including freewheeling mode, reverse excitation mode, reverse upper tube zero voltage freewheeling mode, reverse lower tube zero voltage freewheeling mode and reverse negative voltage freewheeling mode. The three switch tubes of a bridge arm are named as the upper tube, the middle tube and the lower tube according to their positions. The parasitic diode of the upper tube is named the upper diode, the parasitic diode of the middle tube is named the middle diode, and the parasitic diode of the lower tube is named as the lower diode. . The current bridge arm is the kth bridge arm, the next bridge arm is the k+1th bridge arm, and the previous bridge arm is the k-1th bridge arm. If both ends of a phase winding are connected to the upper node of the k-th bridge arm and the lower node of the k+1-th bridge arm respectively, in the forward excitation mode, the upper tube of the k-th bridge arm and the k+1-th bridge need to be turned on. Arm down tube. For example, when the A-phase is excited in the forward direction, it is necessary to turn on the upper tube S1 of the first bridge arm and the lower tube S6 of the second bridge arm, and excite the A-phase winding through the power supply. In the reverse excitation mode, it is necessary to turn on the middle tube and the lower tube of the kth bridge arm, and the upper tube and the middle tube of the k+1th bridge arm. For example, the middle tube S2, the lower tube S3 of the first bridge arm, the upper tube S4 and the middle tube S5 of the second bridge arm need to be turned on when the phase A is reversely excited. In the case of zero-voltage freewheeling of the forward upper tube, the upper tube of the kth bridge arm needs to be turned on, and the parasitic diode of the upper tube of the k+1th bridge arm and the parasitic diode of the middle tube are turned on at the same time. For example, when phase A is forwarding with zero-voltage freewheeling of the upper tube, it is necessary to turn on the upper tube S1 of the first bridge arm, and at the same time turn on the parasitic diode D4 of the upper tube S4 of the second bridge arm and the parasitic diode D5 of the middle tube S5. When the zero-voltage freewheeling of the reverse upper tube is performed, the parasitic diode of the upper tube of the kth bridge arm needs to be turned on, and the upper tube and the middle tube of the k+1th bridge arm need to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the upper tube, it is necessary to turn on the parasitic diode D1 of the upper tube S1 of the first bridge arm, and simultaneously turn on the upper tube S4 and the middle tube S5 of the second bridge arm. In the case of zero-voltage freewheeling of the forward lower tube, it is necessary to turn on the parasitic diode of the middle tube of the kth bridge arm and the parasitic diode of the lower tube, and at the same time turn on the lower tube of the k+1th bridge arm. For example, when the A-phase forward lower tube has zero-voltage freewheeling, it is necessary to turn on the parasitic diode D2 of the middle tube S2 of the first bridge arm and the parasitic diode D3 of the lower tube S3, and at the same time turn on the lower tube S6 of the second bridge arm. When the zero-voltage freewheeling of the reverse lower tube is performed, the middle tube and the lower tube of the k-th bridge arm need to be turned on, and the parasitic diode of the lower tube of the k+1-th bridge arm needs to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the lower tube, it is necessary to turn on the middle tube S2 and the lower tube S3 of the first bridge arm, and simultaneously turn on the parasitic diode D6 of the lower tube S6 of the second bridge arm. When the forward and negative voltage freewheels, it is necessary to turn on the parasitic diode of the middle tube of the kth bridge arm and the parasitic diode of the lower tube, and at the same time turn on the parasitic diode of the upper tube of the k+1th bridge arm and the parasitic diode of the middle tube . For example, when the positive and negative voltage of phase A is freewheeling, it is necessary to turn on the parasitic diode D2 of the middle tube S2 of the first bridge arm and the parasitic diode D3 of the lower tube S3, and at the same time turn on the parasitic diode of the upper tube S4 of the second bridge arm D4 and the parasitic diode D5 of the intermediate tube S5. When the reverse negative voltage freewheels, the parasitic diode of the upper tube of the k-th bridge arm needs to be turned on, and the parasitic diode of the lower tube of the k+1-th bridge arm needs to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the lower tube, the parasitic diode D1 of the upper tube S1 of the first bridge arm needs to be turned on, and the parasitic diode D6 of the lower tube S6 of the second bridge arm needs to be turned on at the same time.

Through the effective combination of 8 operating modes, the orderly bipolar operation of the current can be realized, which can eliminate the phenomenon of asymmetry of the magnetic circuit of the even-phase switched reluctance motor, realize the balanced control of the magnetic circuit, and reduce the torque ripple of the system. At the same time, the proposed magnetic circuit balance control method can reduce the phase current frequency, thereby reducing the iron loss and improving the operating efficiency of the system. Taking the four-phase switched reluctance motor as an example, if the A-phase, B-phase, C-phase and D-phase pass through the unipolar current in an orderly manner, then the stator pole magnetic field distribution has two situations: NNNNSSSS or NSNSSNSN. For the first case, there will be 3 long magnetic circuits and 1 short magnetic circuit in one week, and for the second case, there will be 1 long magnetic circuit and 3 short magnetic circuits in a week. Using the proposed three-switch converter, the A-phase, B-phase, C-phase and D-phase are passed into the bipolar current orderly, and the current order is A+, B+, C+D+A-B-C-D-, at this time the stator pole The magnetic field distribution is NSNSNSNS, all of which are short-circuit operation to realize the symmetrical distribution of the magnetic field, so this method is called the magnetic circuit balance control method.

The proposed converter can provide a variety of excitation modes and two-phase series conduction channels, so that after the system open-circuit fault occurs, part of the excitation of the faulty phase can be guaranteed, and the fault tolerance and reliability of the system can be improved. After that, the short-circuit fault can be converted into an open-circuit fault manually; for example, after the open-circuit fault occurs in the lower tube S3 of the A-phase, S2, S4, S5, S11 and S12 can be turned on to make the D-phase and A-phase conduct in series; and the A-phase upper tube After S1 has a short-circuit fault, S1 can be manually cut off to convert the short-circuit fault into an open-circuit fault.

The beneficial effects of the present invention are: compared with the conventional asymmetric half-bridge power converter for driving a switched reluctance motor, the power converter can reduce the number of power semiconductor devices used, and at the same time, it is not necessary to increase passive devices such as inductors and capacitors, As a result, system cost and size can be reduced, power density, efficiency and fault tolerance can be improved, and torque ripple can be reduced.

Description of drawings

FIG. 1 is a topological structure diagram of a three-switch converter according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of a forward excitation mode current path according to Embodiment 1 of the present invention.

3 is a schematic diagram of a reverse excitation mode current path according to Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of the current path in the zero-voltage freewheeling mode of the forward upper tube according to Embodiment 1 of the present invention.

FIG. 5 is a schematic diagram of the current path in the zero-voltage freewheeling mode of the reverse upper tube according to Embodiment 1 of the present invention.

FIG. 6 is a schematic diagram of a current path in a zero-voltage freewheeling mode of a forward lower tube according to Embodiment 1 of the present invention.

7 is a schematic diagram of a current path in a zero-voltage freewheeling mode of a reverse lower tube according to Embodiment 1 of the present invention.

FIG. 8 is a schematic diagram of a current path in a forward and negative voltage freewheeling mode according to Embodiment 1 of the present invention.

FIG. 9 is a schematic diagram of a current path in a reverse negative voltage freewheeling mode according to Embodiment 1 of the present invention.

FIG. 10 is a schematic diagram of a fault-tolerant running current path according to Embodiment 1 of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

The topology of a three-switch converter of a switched reluctance motor and a magnetic circuit balancing method according to embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a topological structure diagram of a three-switch converter for a four-phase switched reluctance motor according to an embodiment of the present invention. As shown in FIG. 1 , the topological structure of the three-switch converter for a four-phase switched reluctance motor according to the embodiment of the present invention is characterized in that each bridge arm is composed of three controllable switch tubes with built-in diodes, and each phase winding is connected to the phase on the upper and lower nodes of the adjacent bridge arm. The A-phase winding La is connected to the upper node of the first bridge arm and the lower node of the second bridge arm, the B-phase winding Lb is connected to the upper node of the second bridge arm and the lower node of the third bridge arm, the C-phase winding is connected to the upper node of the second bridge arm and the lower node of the third bridge arm. The winding Lc is connected to the upper node of the third bridge arm and the lower node of the fourth bridge arm, and the D-phase winding Ld is connected to the upper node of the fourth bridge arm and the lower node of the first bridge arm. The proposed three-switch converter topology can realize the current bipolar operation, with positive excitation mode, positive upper tube zero-voltage freewheeling mode, positive lower tube zero-voltage freewheeling mode, positive negative voltage freewheeling mode, There are 8 operating modes including reverse excitation mode, reverse upper tube zero voltage freewheeling mode, reverse lower tube zero voltage freewheeling mode and reverse negative voltage freewheeling mode. The three switch tubes of a bridge arm are named as the upper tube, the middle tube and the lower tube according to their positions, the parasitic diode of the upper tube is named the upper diode, the parasitic diode of the middle tube is the middle diode, and the parasitic diode of the lower tube is named as the lower diode. The current bridge arm is the kth bridge arm, the next bridge arm is the k+1th bridge arm, and the previous bridge arm is the k-1th bridge arm. If both ends of a phase winding are connected to the upper node of the k-th bridge arm and the lower node of the k+1-th bridge arm respectively, in the forward excitation mode, the upper tube of the k-th bridge arm and the k+1-th bridge need to be turned on. Arm down tube. For example, when the A-phase is excited in the forward direction, the upper tube S1 of the first bridge arm and the lower tube S6 of the second bridge arm need to be turned on, and the A-phase winding is positively excited through the power supply, as shown in Figure 2. In the reverse excitation mode, it is necessary to turn on the middle tube and the lower tube of the kth bridge arm, and the upper tube and the middle tube of the k+1th bridge arm. For example, the middle tube S2, the lower tube S3 of the first bridge arm, the upper tube S4 and the middle tube S5 of the second bridge arm need to be turned on when the phase A is reversely excited, as shown in Figure 3. In the case of zero-voltage freewheeling of the forward upper tube, the upper tube of the kth bridge arm needs to be turned on, and the parasitic diode of the upper tube of the k+1th bridge arm and the parasitic diode of the middle tube are turned on at the same time. For example, when the A-phase positive upper tube has zero-voltage freewheeling, it is necessary to turn on the upper tube S1 of the first bridge arm, and at the same time turn on the parasitic diode D4 of the upper tube S4 of the second bridge arm and the parasitic diode D5 of the middle tube S5, as shown in the figure 4 shown. When the zero-voltage freewheeling of the reverse upper tube is performed, the parasitic diode of the upper tube of the kth bridge arm needs to be turned on, and the upper tube and the middle tube of the k+1th bridge arm need to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the upper tube, it is necessary to turn on the parasitic diode D1 of the upper tube S1 of the first bridge arm, and simultaneously turn on the upper tube S4 and the middle tube S5 of the second bridge arm, as shown in Figure 5. In the case of zero-voltage freewheeling of the forward lower tube, it is necessary to turn on the parasitic diode of the middle tube of the kth bridge arm and the parasitic diode of the lower tube, and at the same time turn on the lower tube of the k+1th bridge arm. For example, when the A-phase forward lower tube has zero-voltage freewheeling, it is necessary to turn on the parasitic diode D2 of the middle tube S2 of the first bridge arm and the parasitic diode D3 of the lower tube S3, and at the same time turn on the lower tube S6 of the second bridge arm. As shown in Figure 6. When the zero-voltage freewheeling of the reverse lower tube is performed, the middle tube and the lower tube of the k-th bridge arm need to be turned on, and the parasitic diode of the lower tube of the k+1-th bridge arm needs to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the lower tube, it is necessary to turn on the middle tube S2 and the lower tube S3 of the first bridge arm, and simultaneously turn on the parasitic diode D6 of the lower tube S6 of the second bridge arm, as shown in Figure 7. When the forward and negative voltage freewheels, it is necessary to turn on the parasitic diode of the middle tube of the kth bridge arm and the parasitic diode of the lower tube, and at the same time turn on the parasitic diode of the upper tube of the k+1th bridge arm and the parasitic diode of the middle tube . For example, when the positive and negative voltage of phase A is freewheeling, it is necessary to turn on the parasitic diode D2 of the middle tube S2 of the first bridge arm and the parasitic diode D3 of the lower tube S3, and at the same time turn on the parasitic diode of the upper tube S4 of the second bridge arm D4 and the parasitic diode D5 of the intermediate tube S5, as shown in Figure 8. When the reverse negative voltage freewheels, the parasitic diode of the upper tube of the k-th bridge arm needs to be turned on, and the parasitic diode of the lower tube of the k+1-th bridge arm needs to be turned on at the same time. For example, when A reverses the zero-voltage freewheeling of the down tube, it is necessary to turn on the parasitic diode D1 of the upper tube S1 of the first bridge arm, and simultaneously turn on the parasitic diode D6 of the lower tube S6 of the second bridge arm, as shown in Figure 9.

Through the effective combination of 8 operating modes, the orderly bipolar operation of the current can be realized, which can eliminate the phenomenon of asymmetry of the magnetic circuit of the even-phase switched reluctance motor, realize the balanced control of the magnetic circuit, and reduce the torque ripple of the system. At the same time, the proposed magnetic circuit balance control method can reduce the phase current frequency, thereby reducing the iron loss and improving the operating efficiency of the system. Taking the four-phase switched reluctance motor as an example, if the A-phase, B-phase, C-phase and D-phase pass through the unipolar current in an orderly manner, then the stator pole magnetic field distribution has two situations: NNNNSSSS or NSNSSNSN. For the first case, there will be 3 long magnetic circuits and 1 short magnetic circuit in one week, and for the second case, there will be 1 long magnetic circuit and 3 short magnetic circuits in a week. Using the proposed three-switch converter, the A-phase, B-phase, C-phase and D-phase are passed into the bipolar current orderly, and the current order is A+, B+, C+D+A-B-C-D-, at this time the stator pole The magnetic field distribution is NSNSNSNS, all of which are short-circuit operation to realize the symmetrical distribution of the magnetic field, so this method is called the magnetic circuit balance control method.

The proposed converter can provide a variety of excitation modes and two-phase series conduction channels, so that after the system open-circuit fault occurs, part of the excitation of the faulty phase can be guaranteed, and the fault tolerance and reliability of the system can be improved. After that, the short-circuit fault can be manually converted into an open-circuit fault; for example, after the open-circuit fault of the A-phase upper tube S1, S10 and S6 can be turned on to make the D-phase and A-phase conduct in series; and after the A-phase upper-tube S1 has a short-circuit fault, S1 can be manually removed to convert a short circuit fault into an open circuit fault.

The proposed converter can provide a variety of excitation modes and two-phase series conduction channels, so that after the system open-circuit fault occurs, part of the excitation of the faulty phase can be guaranteed, and the fault tolerance and reliability of the system can be improved. After that, the short-circuit fault can be manually converted into an open-circuit fault; for example, after the open-circuit fault occurs in the lower tube S3 of the A-phase, S2, S4, S5, S11 and S12 can be turned on to make the D-phase and A-phase conduct in series, as shown in Figure 10 ; After the A-phase upper tube S1 has a short-circuit fault, S1 can be manually removed to convert the short-circuit fault into an open-circuit fault.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (2)

1. a control method of a three-switch converter topology circuit for a switched reluctance motor, it is characterized in that: each bridge arm of the topology circuit is made up of the controllable switch tubes S1, S2 and S3 of three built-in diodes in series successively, each The phase windings are respectively connected on the upper and lower nodes of the adjacent bridge arms, wherein the upper node is the intersection of S1 and S2, and the lower node is the intersection of S2 and S3; the control method includes: the topology circuit can provide a variety of excitation modes and two The channel that is connected in series can make the faulty phase and another phase winding be connected in series after an open-circuit fault occurs in the switch tube of a certain phase, so as to ensure part of the excitation of the faulty phase; The fault switch tube converts a short-circuit fault into an open-circuit fault. 2. A control method as claimed in claim 1, characterized in that it has a positive excitation mode, a positive upper tube zero-voltage freewheeling mode, a positive lower tube zero-voltage freewheeling mode, and a positive negative voltage freewheeling mode , reverse excitation mode, reverse upper tube zero voltage freewheeling mode, reverse lower tube zero voltage freewheeling mode and reverse negative voltage freewheeling mode 8 operating modes; through the effective combination of 8 operating modes, the current can be realized. Orderly bipolar operation can eliminate the asymmetry of the magnetic circuit of the even-phase switched reluctance motor and realize the balanced control of the magnetic circuit.

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