Switched reluctance motor electrolytic capacitor-free driving and charging integrated system and control method

Abstract

The application discloses a switched reluctance motor electrolytic capacitor-free driving and charging integrated system, which comprises a storage battery, a bus filter capacitor, a power balance circuit, an asymmetric half-bridge circuit, a switched reluctance motor, a driving / charging switch and a rectifier bridge; the power balance circuit is connected in parallel across the storage battery and is composed of two switching tubes, one capacitor and one high-frequency inductor; in the driving mode, the power balance circuit can eliminate the pulsating power on the bus, realizes the electrolytic capacitor-free driving of the switched reluctance motor and improves the reliability of the system; in the charging mode, the power balance circuit is reused as a boost charging circuit of the storage battery, realizes the driving / charging integration of the switched reluctance motor and reduces the volume of the system; and the application is compatible with DC power supply and AC power supply and is applicable to switched reluctance motors with any number of phases.

Description

Technical Field

[0001] This invention relates to switched reluctance motors, and more particularly to a capacitor-free integrated drive / charging system and control method for switched reluctance motors. Background Technology

[0002] Most existing fast-charging networks have a maximum output voltage of 500V for their charging stations, while the battery packs in vehicles operate at 800V. Therefore, the voltage of the charging stations must be increased before the battery packs can be charged. Boost charging technology solves the "chicken and egg" problem of 800V electric vehicles and 800V charging networks. It allows charging with existing 500V charging stations, and also enables charging with future 800V charging stations, serving as a transitional technology for the 800V platform.

[0003] Due to the nonlinearity and commutation characteristics of switched reluctance motors (SRMs), the energy transferred between the DC power supply and the SRM exhibits significant pulsation. A simple method to suppress this pulsating power is to connect a large electrolytic capacitor in parallel on the DC bus side. However, electrolytic capacitors greatly increase the cost and size of the entire system. Furthermore, electrolytic capacitors have short lifespans and high failure rates, making them the weakest link in the SRM drive circuit and reducing system reliability. Electrolytic capacitor-free motor technology can improve system reliability, reduce costs, and decrease size, becoming an important direction in modern motor drive systems and has already been successfully applied in aerospace, industrial drives, and household appliances. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an integrated system and control method for electrolytic capacitor-free drive and charging of a switched reluctance motor that enables multiple boost charging modes, including slow charging with single-phase AC power, fast charging with three-phase AC power, and fast charging with DC power, without requiring switching between drive and charging modes.

[0005] Technical solution: The present invention provides an integrated electrolytic capacitor-free drive and charging system for a switched reluctance motor. The on-board component includes a battery, a second capacitor, an asymmetrical half-bridge circuit, a switched reluctance motor, a rectifier bridge, and a filter. It also includes a power balancing circuit connected in parallel across the battery, comprising a seventh switch, an eighth switch, a first capacitor, and a high-frequency inductor. Wherein:

[0006] One end of the high-frequency inductor is connected to the output terminal of the seventh switch and the input terminal of the eighth switch, and the other end is connected to the first capacitor. The other end of the first capacitor is connected to the output terminal of the eighth switch. The input terminal of the seventh switch is connected to the positive terminal of the battery, and the output terminal of the eighth switch is connected to the negative terminal of the battery.

[0007] The output terminal of the rectifier bridge is connected in parallel across the first capacitor.

[0008] When the system is in drive mode, the DC / AC power supply is not connected to the circuit and the rectifier bridge does not work. By controlling the seventh and eighth switching transistors in the power balance circuit, the pulsating power on the bus is eliminated, realizing the electrolytic capacitor-free drive of the switched reluctance motor. At this time, the second capacitor is the bus filter capacitor.

[0009] When the system is in charging mode, the DC / AC power supply is connected to the circuit, the rectifier bridge works, and the power balancing circuit is reused as the boost PFC circuit for battery boost charging. At this time, the second capacitor is the output capacitor of the boost circuit.

[0010] Furthermore, in charging mode, when the external power source is a three-phase AC power source, connect the first terminal, the second terminal, and the third terminal respectively; when the external power source is a single-phase AC power source, connect any two of the first terminal, the second terminal, and the third terminal respectively; when the external power source is a DC power source, connect any two of the first terminal, the second terminal, and the third terminal respectively, or connect directly to the positive terminal and the negative terminal.

[0011] Furthermore, the rectifier bridge is a single-phase bridge or three-phase bridge rectifier circuit.

[0012] Furthermore, each of the switching transistors is a Si or SiC controllable switching transistor.

[0013] Furthermore, the switched reluctance motor has any number of phases.

[0014] Furthermore, the circuit control of the above-mentioned electrolytic capacitor-free drive and charging integrated system for the switched reluctance motor is implemented; in drive mode, when the external DC / AC power supply is not connected, the control methods for phases A, B, and C are the same; the control steps for phase A are as follows:

[0015] S11, the first and second switching transistors are turned on, and the battery excites the A-phase motor windings;

[0016] S12, the first and second switching transistors are turned off, and the current on the A-phase motor winding is fed back to the battery through the first and second diodes.

[0017] Furthermore, in drive mode, when the external DC / AC power supply is not connected, the control steps of the power balancing circuit are as follows:

[0018] S21, when the bus current is higher than the average current, the seventh switch is turned on, and part of the bus current flows into the first capacitor through the high-frequency inductor L, charging the first capacitor.

[0019] S22, when the bus current equals the average current, the seventh switch is turned off, and the electrical energy stored in the high-frequency inductor is transferred to the first capacitor, which is then charged.

[0020] S23, when the bus current is lower than the average current, the eighth switch is turned on first, the first capacitor discharges, and the high-frequency inductor is charged; then the eighth switch is turned off, and the first capacitor discharges through the high-frequency inductor and the body diode of the seventh switch to compensate for the bus current.

[0021] S24: When the bus current equals the average current, the eighth switch is turned on and no longer compensates for the bus current.

[0022] Furthermore, the control steps in charging mode are as follows:

[0023] S31, the eighth switch is turned on, and the external power supply charges the high-frequency inductor; at this time, the second capacitor charges the battery.

[0024] When the eighth switch S32 is turned off, the high-frequency inductor discharges, and the stored energy charges the battery and the second capacitor through the body diode of the seventh switch. The charging voltage is changed by adjusting the duty cycle of the eighth switch to match the nominal potential of the battery.

[0025] Compared with the prior art, the significant advantages of this invention are as follows:

[0026] 1. Based on the original asymmetrical half-bridge circuit of the switched reluctance motor, this invention adds a power balancing circuit to eliminate the pulsating power on the bus in the driving mode, and replaces the large-capacity filter electrolytic capacitor connected in parallel at both ends of the bus, so as to realize the electrolytic capacitor-free driving of the switched reluctance motor and improve the reliability of the system.

[0027] 2. In charging mode, the power balancing circuit is reused as the battery boost charging circuit, realizing the integration of switched reluctance motor drive / charging, thus reducing the system size;

[0028] 3. This system is compatible with both DC and AC power supplies and is suitable for switched reluctance motors with any number of phases. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall circuit of the present invention;

[0030] Figure 2(a) is a circuit diagram of the excitation state when the present invention is in the first electric mode.

[0031] Figure 2(b) is a circuit diagram of the freewheeling state of the present invention in the second electric mode.

[0032] Figure 3(a) is a schematic diagram of the power balance circuit in this invention when the bus current is higher than the average current;

[0033] Figure 3(b) is a schematic diagram of the power balance circuit in this invention when the bus current is equal to the average current.

[0034] Figure 3(c) is a schematic diagram of the switching transistor being turned on in the power balance circuit when the bus current is lower than the average current in this invention.

[0035] Figure 3(d) is a schematic diagram of the switching transistor being turned off in the power balance circuit when the bus current is lower than the average current in this invention.

[0036] Figure 4(a) shows the working state of the first boost charging mode of the present invention: the external power supply charges the high-frequency inductor L and the second capacitor C2 charges the battery.

[0037] Figure 4(b) shows the working state of the second boost charging mode of the present invention: the external power supply charges the battery and the second capacitor C2 through the inductor L.

[0038] Figure 5 This is a schematic diagram illustrating the structure of the present invention for achieving electrolytic capacitor-free motor driving and time-sharing multiplexing of battery charging. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] This invention proposes an electrolytic capacitor-free drive / charging integrated system for switched reluctance motors (SRMs) in electric vehicles, applicable to various applications such as plug-in high-power hybrid electric vehicles driven by SRMs. Based on the original asymmetrical half-bridge circuit of the SRM, this invention adds a power balancing circuit. In drive mode, it eliminates pulsating power on the bus, replacing the large-capacity electrolytic capacitors connected in parallel across the bus, thus achieving electrolytic capacitor-free drive of the SRM and improving system reliability. In charging mode, the power balancing circuit is reused as a boost PFC circuit for battery voltage boosting, reducing system size. This invention is compatible with DC power supplies and single-phase or three-phase AC power supplies, and is applicable to SRMs with any number of phases.

[0041] like Figure 1 The diagram shows a schematic of a switched reluctance motor-driven charging integrated system without electrolytic capacitors, which can be used in the electric vehicle field. Its on-board components mainly include a battery, bus filter capacitor, power balance circuit, asymmetrical half-bridge circuit, switched reluctance motor, rectifier bridge, and filter.

[0042] The power balancing circuit is connected in parallel across the battery and consists of two switching transistors, one capacitor, and one high-frequency inductor. Specifically: one end of the high-frequency inductor L is connected to the output of the seventh switching transistor Q7 and the input of the eighth switching transistor Q8, and the other end is connected to the first capacitor C1. The other end of the first capacitor C1 is connected to the output of the eighth switching transistor Q8. The input of the seventh switching transistor Q7 is connected to the positive terminal of the battery, and the output of the eighth switching transistor Q8 is connected to the negative terminal of the battery. The output of the rectifier bridge is connected in parallel across the first capacitor C1.

[0043] When the system is in drive mode, the DC / AC power supply is not connected to the circuit, the rectifier bridge does not work, and the pulsating power on the bus is eliminated by controlling the seventh switch Q7 and the eighth switch Q8 in the power balance circuit. The large-capacitance filter electrolytic capacitor connected in parallel at both ends of the bus is replaced. The second capacitor C2 is the bus filter capacitor, realizing the electrolytic capacitor-free drive of the switched reluctance motor and improving the reliability of the system.

[0044] When the system is in charging mode, the DC / AC power supply is connected to the circuit, the rectifier bridge operates, and the power balancing circuit is reused as a boost PFC (Power Factor Correction) circuit for battery voltage boosting. The second capacitor C2 is the output capacitor of the boost circuit, reducing the system size. Figure 5 As shown. This invention is compatible with DC power supplies and single-phase or three-phase AC power supplies, and is applicable to switched reluctance motors with any number of phases.

[0045] In charging mode, when the external power source is a three-phase AC power supply, connect terminals P1, P2, and P3 respectively; when the external power source is a single-phase AC power supply, connect any two terminals P1, P2, and P3 respectively; when the external power source is a DC power supply, connect any two terminals P1, P2, and P3 respectively, or directly connect to terminals P and N. When an external AC power supply is connected, the rectifier bridge rectifies the AC power into DC power; when an external DC power supply is connected, the rectifier bridge acts as a reverse connection protection circuit, ensuring the correct polarity of the subsequent circuit regardless of the polarity of the external DC power supply.

[0046] A three-phase bridge rectifier circuit can be an uncontrolled or controlled rectifier circuit; when the external power supply is a single-phase AC power supply or a DC power supply, the rectifier bridge can also be a single-phase bridge uncontrolled or controlled rectifier circuit.

[0047] In this embodiment, the switched reluctance motor has 3 phases. The specific control steps of the electrolytic capacitor-free drive / charging integrated system for the switched reluctance motor are as follows:

[0048] In drive mode, the control steps for motor winding excitation and freewheeling are as follows. The control methods for phases A, B, and C are the same. Taking phase A as an example:

[0049] 11) When the first switch Q1 and the second switch Q2 are turned on, the battery excites the A-phase motor winding, as shown in Figure 2(a);

[0050] 12) When the first switch Q1 and the second switch Q2 are turned off, the current on the excitation of the A-phase motor winding is fed back to the battery through the first diode D1 and the second diode D2, as shown in Figure 2(b).

[0051] In drive mode, the control steps of the power balancing circuit are as follows:

[0052] 21) When the bus current is higher than the average current, the seventh switch Q7 is turned on, and part of the bus current flows into the first capacitor C1 through the high-frequency inductor L, and the first capacitor C1 is charged, as shown in Figure 3(a).

[0053] 22) When the bus current is equal to the average current, the seventh switch Q7 is turned off, and the electrical energy stored in the inductor L is transferred to the first capacitor C1, and the first capacitor C1 is charged, as shown in Figure 3(b).

[0054] 23) When the bus current is lower than the average current, the eighth switch Q8 is turned on first, the first capacitor C1 is discharged, and the high-frequency inductor L is charged, as shown in Figure 3(c); then the eighth switch Q8 is turned off, and the first capacitor C1 is discharged through the high-frequency inductor L and the body diode of the seventh switch Q7 to compensate for the bus current, as shown in Figure 3(d).

[0055] 24) When the bus current is equal to the average current, the eighth switch Q8 is turned on and no longer compensates for the bus current, as shown in Figure 3(c).

[0056] The control steps in charging mode are as follows:

[0057] 31) When the eighth switch Q8 is turned on, the external power supply charges the high-frequency inductor L; at this time, the second capacitor C2 charges the battery, as shown in Figure 4(a).

[0058] 32) When the eighth switch Q8 is turned off, the high-frequency inductor L discharges, and the stored energy charges the battery and the second capacitor C2 through the body diode of the seventh switch Q7, as shown in Figure 4(b). The charging voltage is changed by adjusting the duty cycle of the eighth switch Q8 to match the nominal potential of the battery.

[0059] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A switched reluctance motor electrolytic capacitor-free drive charging integrated system, the on-board part comprising a battery, a second capacitor (C2), an asymmetric half-bridge circuit, a switched reluctance motor, a rectifier bridge and a filter; characterized in that: Further comprising a power balance circuit connected in parallel with the storage battery, the power balance circuit comprising a seventh switch tube (Q7), an eighth switch tube (Q8), a first capacitor (C1), and a high-frequency inductor (L); wherein: One end of the high-frequency inductor (L) is connected with the output end of the seventh switch tube and the input end of the eighth switch tube respectively, one end is connected with the first capacitor (C1), the other end of the first capacitor (C1) is connected with the output end of the eighth switch tube (Q8); the input end of the seventh switch tube (Q7) is connected with the positive pole of the storage battery, and the output end of the eighth switch tube (Q8) is connected with the negative pole of the storage battery; The output end of the rectifier bridge is connected in parallel with the two ends of the first capacitor (C1); When the system is in the driving mode, the direct current / alternating current power supply is not connected to the circuit, the rectifier bridge does not work, the seventh switch tube (Q7) and the eighth switch tube (Q8) in the power balance circuit are controlled to eliminate the pulsating power on the bus, and the electrolytic capacitor-free driving of the switched reluctance motor is realized, at this time, the second capacitor (C2) is the bus filter capacitor; When the system is in the charging mode, the direct current / alternating current power supply is connected to the circuit, the rectifier bridge works, and the power balance circuit is reused as a boost PFC circuit for boosting and charging the storage battery, at this time, the second capacitor (C2) is the output capacitor of the boost circuit.

2. The switched reluctance motor drive and charging integrated system of claim 1, wherein In the charging mode, when the external power supply is a three-phase alternating current power supply, the first terminal (P1), the second terminal (P2), and the third terminal (P3) are connected respectively; when the external power supply is a single-phase alternating current power supply, any two of the first terminal (P1), the second terminal (P2), and the third terminal (P3) are connected respectively; when the external power supply is a direct current power supply, any two of the first terminal (P1), the second terminal (P2), and the third terminal (P3) are connected or directly connected with the positive terminal (P) and the negative terminal (N).

3. The switched reluctance motor drive and charging integrated system of claim 1, wherein, The rectifier bridge is a three-phase bridge rectifier circuit or a single-phase bridge rectifier circuit.

4. The switched reluctance motor drive and charging integrated system of claim 1, wherein, The switch tubes are Si or SiC controllable switch tubes.

5. The switched reluctance motor drive and charging integrated system of claim 1, wherein: The switched reluctance motor is of any phase number.

6. A control method of a switched reluctance motor electrolytic capacitor-free drive charging integrated system, characterized by, The circuit control of the switched reluctance motor electrolytic capacitor-free driving and charging integrated system according to any one of claims 1-5 is realized; In the driving mode, when the external direct current / alternating current power supply is not connected, the control strategies of the A phase, the B phase, and the C phase are the same; the control steps of the A phase are as follows: S11, the first switch tube (Q1) and the second switch tube (Q2) are turned on, and the storage battery excites the motor winding A; S12, the first switch tube (Q1) and the second switch tube (Q2) are turned off, and the current on the motor winding A flows back to the storage battery through the first diode (D1) and the second diode (D2).

7. The control method of the switched reluctance motor drive and battery charging integrated system of claim 6, wherein, In the driving mode, when the external direct current / alternating current power supply is not connected, the control steps of the power balance circuit are as follows: S21, when the bus current is higher than the average current, the seventh switch tube (Q7) is turned on, part of the bus current flows into the first capacitor (C1) through the high-frequency inductor L, and the first capacitor (C1) is charged; S22, when the bus current is equal to the average current, the seventh switch tube (Q7) is turned off, the electric energy stored in the high-frequency inductor (L) is transferred to the first capacitor (C1), and the first capacitor (C1) is charged; S23, when the bus current is lower than the average current, the eighth switch (Q8) is turned on first, the first capacitor (C1) is discharged, and the high-frequency inductor (L) is charged; then the eighth switch (Q8) is turned off, and the first capacitor (C1) is discharged through the high-frequency inductor (L) and the body diode of the seventh switch (Q7) to compensate for the bus current. S24 When the bus current equals the average current, the eighth switch (Q8) is turned on and no longer compensates for the bus current.

8. The control method of the switched reluctance motor drive and battery charging integrated system of claim 6, wherein, The control steps in charging mode are as follows: S31, the eighth switch (Q8) is turned on, and the external power supply charges the high-frequency inductor (L); at this time, the second capacitor (C2) charges the battery; S32, the eighth switch (Q8) is turned off, the high-frequency inductor (L) discharges, and the stored energy charges the battery and the second capacitor (C2) through the body diode of the seventh switch (Q7). The charging voltage is changed by adjusting the duty cycle of the eighth switch (Q8) to match the nominal potential of the battery.

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