Field winding dual-mode switching system and current control method of hybrid excitation motor

Abstract

The invention discloses a dual-mode switching system for an excitation winding of a hybrid excitation motor and a current control method. The system comprises an armature winding, an excitation winding, a power converter and a relay switch. The armature winding and the excitation winding are respectively connected to different power converters for power supply. The armature winding and the excitation winding are connected or separated by controlling the relay switch. When the hybrid excitation motor does not need to adjust the magnetic field of the excitation winding, the excitation winding is connected in series with the armature winding by controlling the relay switch. At this time, the excitation winding, as a part of the armature winding, can increase the output torque of the motor. When the hybrid excitation motor needs to increase the magnetization or weaken the magnetic field of the excitation winding, the excitation winding is separated from the armature winding by controlling the relay switch, and the two work independently and in parallel, thereby improving the output torque of the motor. Moreover, each phase of the excitation winding in the hybrid excitation motor adopts a current intermittent working mode, thereby reducing the loss of the excitation winding and improving the working efficiency of the motor.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to a dual-mode switching system for an excitation winding of a hybrid excitation motor and a current control method. Background Art

[0002] Hybrid excitation motors have the advantages of low excitation loss and high efficiency, and have increasingly gained widespread attention and application. In order to improve the efficiency of the motor, the excitation magnetic potential of the hybrid excitation motor is usually based on the permanent magnet magnetic potential, supplemented by the electric excitation magnetic potential, and the permanent magnet magnetic potential is significantly greater than the electric excitation magnetic potential. Therefore, in normal operation, the motor is usually excited by the permanent magnet, and no current flows through the electric excitation winding; when the motor needs to run in a low-speed overload state, the electric excitation winding passes a positive DC current, so that the electric excitation magnetic potential generated by it is in the same direction as the permanent magnet magnetic potential, so that the motor magnetic field is enhanced, thereby increasing the motor output torque; when the motor needs to run at high speed and light load, the electric excitation winding passes a reverse DC current, so that the electric excitation magnetic potential generated by it is in the opposite direction to the permanent magnet magnetic potential, so that the motor magnetic field is weakened, thereby increasing the motor speed. Due to the low utilization rate of the excitation winding, the hybrid excitation motor usually sacrifices a small part of the armature winding space in exchange for the magnetic field adjustment capability, so its torque density is slightly lower than that of the permanent magnet motor.

[0003] The armature windings A, B, C and the excitation windings FA, FB, FC in the hybrid excitation motor are wound in the following manner: the excitation coil is wound on the middle stator pole of a stator pole group composed of three continuous stator poles, and the armature coil is wound across the three stator poles corresponding to the stator pole group. Multiple armature coils of the same phase are connected in series or in parallel or in mixed connection to form the armature winding of the phase; the excitation coils surrounded by the armature coil of the same phase are connected in series or in parallel to form the corresponding excitation winding; the armature winding is used for motor output, and the excitation winding is used for regulating the motor magnetic field. Taking the new type of 18 / 10 structure flux reversal three-phase double salient pole motor as an example, its motor structure is as shown in the attached figure. Figure 6 As shown; according to the motor structure and working principle, the middle stator pole alignment position of the A-phase winding is assumed to be the 0-degree electrical angle position; when the angle is in the range of [-90°, 90°], the A-phase excitation current provides excitation flux for the three phases A, B, and C, and the three phases output simultaneously; when the electrical angle is in a range near 180°, the A-phase armature current mainly interacts with the magnetic field established by the B- and C-phase excitation currents to generate output torque, and the A-phase excitation current contributes very little to the motor output and will generate a large leakage flux, thereby increasing the core loss of the motor. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a dual-mode switching system and current control method for the excitation winding of a hybrid excitation motor that can reduce the excitation loss of the motor and enable the excitation winding to be reused with the armature winding, thereby improving the output torque of the motor.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A dual-mode switching system for an excitation winding of a hybrid excitation motor and a current control method, comprising an armature winding, an excitation winding, a power converter and a relay switch, wherein the armature winding and the excitation winding are respectively connected to different power converters for power supply, and the armature winding and the excitation winding are connected or separated by the relay switch. When the hybrid excitation motor does not need to adjust the magnetic field of the excitation winding, the excitation winding is connected in series with the armature winding by controlling the relay switch. At this time, the excitation winding, as a part of the armature winding, can increase the motor output torque; when the hybrid excitation motor needs to increase the magnetic field of the excitation winding or weaken the magnetic field, the excitation winding is separated from the armature winding by controlling the relay switch, and the two work independently and in parallel.

[0007] The power converter includes a three-arm power converter, a two-arm power converter and a four-arm power converter, and the relay switch includes a three-phase relay switch S1, a three-phase relay switch S2 and a three-phase relay switch S3.

[0008] When the armature winding is powered by the three-arm power converter and the excitation winding is powered by the two-arm power converter, the three arm midpoints of the three-arm power converter are respectively connected to the three-phase head ends of the armature winding; the two arm midpoints of the two-arm power converter are respectively connected to the normally-off contact k20_a of the three-phase relay switch S2 and the normally-off contact k30_c of the three-phase relay switch S3; the three-phase normally-off contacts k20_a, k20_b, k20_c of the three-phase relay switch S2 are respectively connected to the three-phase normally-off contacts k20_a, k20_b, k20_c of the three-phase relay switch S2. They are respectively connected to the midpoint of the first bridge arm of the two-arm power converter, the normally-off contact k30_a of the three-phase relay switch S3 and the normally-off contact k30_b of the three-phase relay switch S3; the incoming line end of the three-phase relay switch S3 is connected to the three-phase head end of the excitation winding, the three-phase normally-on contacts k31_a, k31_b, and k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contact k30_c of the three-phase relay switch S3 is connected to the midpoint of the second bridge arm of the two-arm power converter.

[0009] At this time, when the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally on state, the armature winding and the excitation winding are connected in series, the hybrid excitation motor operates in the non-magnetic adjustment state of permanent magnet excitation, and the excitation winding and the armature winding output power together; when the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally off state, the armature winding and the excitation winding are separated from each other, the excitation winding flows a DC current through the two-bridge arm power converter to adjust the magnetic field of the hybrid excitation motor, and the armature winding outputs power.

[0010] When the armature winding is powered by the three-arm power converter and the excitation winding is powered by the four-arm power converter, the three arm midpoints of the three-arm power converter are respectively connected to the three-phase head ends of the armature winding; the first three arm midpoints of the four-arm power converter are respectively connected to the normally-off contacts k30_a, k30_b and k30_c of the three-phase relay switch S3, and the fourth arm midpoint of the four-arm power converter is connected to the normally-off contacts k20_a, k20_b and k20_c of the three-phase relay switch S2; the incoming line ends of the three-phase relay switch S1 are respectively connected to the three-phase ends of the armature winding, and the three-phase normally-off contacts k10_a, k10_b and k10_c of the three-phase relay switch S1 are short-circuited. The three-phase normally-on contacts k11_a, k11_b, and k11_c of the three-phase relay switch S1 are respectively connected to the three-phase normally-on contacts k21_a, k21_b, and k21_c of the three-phase relay switch S2; the incoming line end of the three-phase relay switch S2 is connected to the three-phase ends of the excitation winding, and the three-phase normally-off contacts k20_a, k20_b, and k20_c of the three-phase relay switch S2 are commonly connected to the fourth bridge arm midpoint of the four-bridge arm power converter, and the three-phase normally-on contacts k31_a, k31_b, and k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contacts k30_a, k30_b, and k30_c of the three-phase relay switch S3 are respectively connected to the first three bridge arm midpoints of the four-bridge arm power converter.

[0011] At this time, when the hybrid excitation motor operates in the non-magnetic adjustment state of permanent magnet excitation, the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally-on state, the armature winding and the excitation winding are connected in series and star-connected, and the excitation winding and the armature winding output power together; when the hybrid excitation motor operates in the magnetic adjustment state, the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally-off state, the armature winding and the excitation winding are separated from each other, and the excitation current adjusts the motor magnetic field through the four-arm power converter.

[0012] The excitation winding of each phase in the hybrid excitation motor adopts a current discontinuous working mode, and the alignment position of the middle stator salient pole and the rotor salient pole of the A-phase armature winding is taken as the electrical angle position of 0 degrees. Then, in a section [180°-Δθ, 180°+Δθ] near the electrical angle of 180°, the excitation current of the excitation winding FA corresponding to phase A is turned off, and in a section [300°-Δθ, 300°+Δθ] near the electrical angle of 300°, the excitation current of the excitation winding FB corresponding to phase B is turned off; in a section [60°-Δθ, 60°+Δθ] near the electrical angle of 60°, the excitation current of the excitation winding FC corresponding to phase C is turned off, thereby reducing the excitation winding loss and improving the working efficiency of the motor, wherein Δθ<90°.

[0013] The positive beneficial effects of the present invention are:

[0014] 1. The present invention reuses the excitation winding, that is, when the motor does not need the excitation winding for magnetic adjustment, the excitation winding is connected in series with the armature winding by controlling the relay switch, and the excitation winding, as a part of the armature winding, outputs power together with the armature winding, thereby improving the output torque of the motor; when the motor needs to work at low speed and high torque or needs excitation current magnetization or magnetic weakening, the excitation winding is separated from the armature winding by controlling the relay switch, and the two work independently and in parallel; by adjusting the size of the DC current input to the excitation converter, the motor magnetic field is regulated to improve the speed range of the hybrid excitation motor or increase the torque output.

[0015] 2. The present invention adopts an intermittent control mode of the excitation winding current, that is: in a section near the electrical angle of 180°, the excitation current of the excitation winding FA corresponding to A is turned off; in a section near the electrical angle of 300°, the excitation current of the excitation winding FB corresponding to B is turned off; in a section near the electrical angle of 60°, the excitation current of the excitation winding FC corresponding to C is turned off, thereby reducing the excitation winding loss and improving the working efficiency of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1This is a topological structure diagram of a power circuit of a control system for multiplexing the excitation winding in Embodiment 1 of the present invention;

[0017] Figure 2 This is a topological structure diagram of a power circuit of a control system for multiplexing excitation windings in Embodiment 2 of the present invention;

[0018] Figure 3 is an enlarged view of the contacts of the three-phase relay switches S1, S2 and S3 in Embodiment 2 of the present invention;

[0019] Figure 4 It is a schematic diagram of the waveform of the excitation current of the excitation windings FA, FB, and FC in the present invention;

[0020] Figure 5 It is the power circuit topology of the three-phase four-bridge-arm excitation control system in Embodiment 2 of the present invention;

[0021] Figure 6 It is a schematic diagram of the motor structure in the background technology of the present invention. DETAILED DESCRIPTION

[0022] The following will refer to the attached Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 Embodiments of the present invention are described in more detail. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0023] The term "include" and variations thereof as used herein are open-ended inclusions, ie, "including but not limited to."

[0024] The names of the messages or information exchanged between multiple devices in the embodiments of the present invention are only used for illustrative purposes, and are not used to limit the scope of these messages or information.

[0025] Embodiment 1: A dual-mode switching system and current control method of an excitation winding of a hybrid excitation motor, including an armature winding, an excitation winding, a three-arm power converter and a two-arm power converter. The armature winding is powered by the three-arm power converter, and the excitation winding is powered by the two-arm power converter.

[0026] The three bridge arm midpoints of the three-arm power converter are respectively connected to the three-phase head end of the armature winding; the two bridge arm midpoints of the two-arm power converter are respectively connected to the normally-off contact k20_a of the three-phase relay switch S2 and the normally-off contact k30_c of the three-phase relay switch S3; the three-phase normally-off contacts k20_a, k20_b, and k20_c of the three-phase relay switch S2 are respectively connected to the first bridge arm midpoint of the two-arm power converter, the normally-off contact k30_a of the three-phase relay switch S3, and the normally-off contact k30_b of the three-phase relay switch S3; the incoming line end of the three-phase relay switch S3 is connected to the three-phase head end of the excitation winding, the three-phase normally-on contacts k31_a, k31_b, and k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contact k30_c of the three-phase relay switch S3 is connected to the second bridge arm midpoint of the two-arm power converter.

[0027] When the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally on state, the armature winding and the excitation winding are connected in series. At this time, the hybrid excitation motor operates in the non-magnetic adjustment state of permanent magnet excitation, and the excitation winding and the armature winding output power together; when the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally off state, the armature winding and the excitation winding are separated from each other, and the excitation winding flows a DC current through the two-arm power converter to adjust the magnetic field of the hybrid excitation motor, and the armature winding outputs power.

[0028] During operation, the armature winding and the excitation winding are connected or separated by operating the control relay switch to be in the normally-on state or the normally-off state. When the hybrid excitation motor does not need the excitation winding to adjust the magnetism, the excitation winding is connected in series with the armature winding by operating the three-phase relay switch S1 and the three-phase relay switch S2 to be in the normally-on state. At this time, the excitation winding, as a part of the armature winding, can increase the output torque of the motor; when the hybrid excitation motor needs the excitation winding to be magnetized or weakened, the excitation winding is separated from the armature winding by operating the three-phase relay switch S1 and the three-phase relay switch S2 to be in the normally-off state, and the two work independently and in parallel.

[0029] In addition, each phase excitation winding in the hybrid excitation motor adopts a current discontinuous working mode, that is, in the electrical angle range of [90°, 270°], the excitation current of the excitation winding FA corresponding to A is turned off, and in the electrical angle range of [210°, 360°] and [0°, 30°], the excitation current of the excitation winding FB corresponding to B is turned off; in the electrical angle range of [0°, 150°] and [330°, 360°], the excitation current of the excitation winding FC corresponding to C is turned off, thereby reducing the excitation winding loss and improving the motor working efficiency.

[0030] Embodiment 2: The difference from Embodiment 1 is that a four-arm power converter is used to replace a two-arm power converter, that is, the armature winding is powered by a three-arm power converter, and the excitation winding is powered by a four-arm power converter.

[0031] The midpoints of the three bridge arms of the three-arm power converter are respectively connected to the three-phase head ends of the armature winding; the midpoints of the first three bridge arms of the four-arm power converter are respectively connected to the normally-off contacts k30_a, k30_b and k30_c of the three-phase relay switch S3, and the midpoint of the fourth bridge arm of the four-arm power converter is connected to the normally-off contacts k20_a, k20_b and k20_c of the three-phase relay switch S2; the incoming line ends of the three-phase relay switch S1 are respectively connected to the three-phase ends of the armature winding, the three-phase normally-off contacts k10_a, k10_b, k10_c of the three-phase relay switch S1 are short-circuited, and the three-phase normally-on contacts k11_a, k11_c of the three-phase relay switch S1 are short-circuited. 1_b, k11_c are respectively connected to the three-phase normally-made contacts k21_a, k21_b, k21_c of the three-phase relay switch S2; the incoming line end of the three-phase relay switch S2 is connected to the three-phase end of the excitation winding, the three-phase normally-off contacts k20_a, k20_b, k20_c of the three-phase relay switch S2 are commonly connected to the fourth bridge arm midpoint of the four-arm power converter, the three-phase normally-made contacts k31_a, k31_b, k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contacts k30_a, k30_b, k30_c of the three-phase relay switch S3 are respectively connected to the first three bridge arm midpoints of the four-arm power converter.

[0032] When the hybrid excitation motor works in the non-magnetic adjustment state of permanent magnet excitation, the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally-on state, the armature winding and the excitation winding are connected in series and in star connection, and the excitation winding and the armature winding output power together; when the hybrid excitation motor works in the magnetic adjustment state, the three-phase relay switch S1, the three-phase relay switch S2 and the three-phase relay switch S3 are all in the normally-off state, the armature winding and the excitation winding are separated from each other, and the excitation current adjusts the motor magnetic field through the four-arm power converter.

[0033] In order to realize the phase-splitting and intermittent control of the excitation current, a three-phase four-bridge-arm excitation control system power circuit topology is also designed in this embodiment, such as Figure 5 As shown, the three-phase excitation winding is star-connected, and the output terminals and neutral points of the three-phase excitation winding are respectively connected to the midpoints of the three-phase four-bridge arms.

[0034] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A dual-mode switching system and current control method for an excitation winding of a hybrid excitation motor, comprising an armature winding, an excitation winding, a power converter and a relay switch, characterized in that: The armature winding and the excitation winding are respectively connected to different power converters for power supply, and the armature winding and the excitation winding are connected or separated by the relay switch. When the hybrid excitation motor does not need to adjust the magnetic field of the excitation winding, the excitation winding is connected in series with the armature winding by controlling the relay switch. At this time, the excitation winding, as a part of the armature winding, can increase the output torque of the motor; when the hybrid excitation motor needs to increase the magnetization or weaken the magnetic field of the excitation winding, the excitation winding is separated from the armature winding by controlling the relay switch, and the two work independently and in parallel.

2. The field winding dual-mode switching system and current control method of the hybrid excitation motor according to claim 1 is characterized by: The power converter includes a three-arm power converter and a two-arm power converter, and the relay switch includes a three-phase relay switch S1, a three-phase relay switch S2 and a three-phase relay switch S3; the three arm midpoints of the three-arm power converter are respectively connected to the three-phase head ends of the armature winding; the two arm midpoints of the two-arm power converter are respectively connected to the normally-off contact k20_a of the three-phase relay switch S2 and the normally-off contact k30_c of the three-phase relay switch S3; the three-phase normally-off contacts k20_a, k20_c of the three-phase relay switch S2 and the three-phase normally-off contacts k30_c of the three-phase relay switch S3. 0_b, k20_c are respectively connected to the midpoint of the first bridge arm of the two-arm power converter, the normally-off contact k30_a of the three-phase relay switch S3 and the normally-off contact k30_b of the three-phase relay switch S3; the incoming line end of the three-phase relay switch S3 is connected to the three-phase head end of the excitation winding, the three-phase normally-on contacts k31_a, k31_b, k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contact k30_c of the three-phase relay switch S3 is connected to the midpoint of the second bridge arm of the two-arm power converter.

3. The field winding dual-mode switching system and current control method of the hybrid excitation motor according to claim 1 is characterized by: The power converter includes a three-arm power converter and a four-arm power converter, and the relay switch includes a three-phase relay switch S1, a three-phase relay switch S2 and a three-phase relay switch S3; the three arm midpoints of the three-arm power converter are respectively connected to the three-phase head ends of the armature winding; the first three arm midpoints of the four-arm power converter are respectively connected to the normally-off contacts k30_a, k30_b and k30_c of the three-phase relay switch S3, and the fourth arm midpoint of the four-arm power converter is connected to the normally-off contacts k20_a, k20_b and k20_c of the three-phase relay switch S2; the incoming line end of the three-phase relay switch S1 is respectively connected to the three-phase ends of the armature winding, and the three-phase normally-off contacts k10_a, k10_b, k10_c of the three-phase relay switch S1 are respectively connected to the three-phase ends of the armature winding. 10_c phase is short-circuited, the three-phase normally-made contacts k11_a, k11_b, k11_c of the three-phase relay switch S1 are respectively connected to the three-phase normally-made contacts k21_a, k21_b, k21_c of the three-phase relay switch S2; the incoming line end of the three-phase relay switch S2 is connected to the three-phase end of the excitation winding, and the three-phase normally-off contacts k20_a, k20_b, k20_c of the three-phase relay switch S2 are commonly connected to the fourth bridge arm midpoint of the four-bridge arm power converter, and the three-phase normally-made contacts k31_a, k31_b, k31_c of the three-phase relay switch S3 are short-circuited, and the three-phase normally-off contacts k30_a, k30_b, k30_c of the three-phase relay switch S3 are respectively connected to the first three bridge arm midpoints of the four-bridge arm power converter.

4. The field winding dual-mode switching system and current control method of the hybrid excitation motor according to claim 2 or 3, characterized in that: The excitation winding of each phase in the hybrid excitation motor adopts a current discontinuous working mode. The position where the middle stator salient pole of the A-phase armature winding is aligned with the rotor salient pole is an electrical angle position of 0 degrees. Then, in an interval [180°-Δθ, 180°+Δθ] near an electrical angle of 180°, the excitation current of the excitation winding FA corresponding to phase A is turned off; in an interval [300°-Δθ, 300°+Δθ] near an electrical angle of 300°, the excitation current of the excitation winding FB corresponding to phase B is turned off; in an interval [60°-Δθ, 60°+Δθ] near an electrical angle of 60°, the excitation current of the excitation winding FC corresponding to phase C is turned off, wherein Δθ<90°.

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