A control method of a bipolar switched reluctance motor with distributed windings

Abstract

The application discloses a kind of bipolarity switched reluctance motor control methods of distributed winding, comprising: 1) selecting suitable bipolarity switched reluctance motor, using distributed installation motor stator winding;2) based on the bipolarity switched reluctance motor selecting suitable power converter, motor each phase winding is connected using star connection mode;3) according to motor structure and the scheme of selected power converter division motor rotor position interval and making switch tube turn-on and turn-off;4) after starting, the commutation of motor is completed by two kinds of control methods.The application selects three-phase full-bridge power converter, reduces the cost of switched reluctance motor controller;Motor winding selects star connection, three-phase full-bridge circuit is connected with winding lead end, combined with the structure of the power converter, two commutation control methods of motor are proposed;Make motor total lead line quantity reduce, can be used in long distance power supply situation under motor drive field, such as downhole oil motor.

Description

Technical Field

[0001] This invention relates to the field of electric drive technology, and in particular to a control method for a bipolar switched reluctance motor with distributed windings. Background Technology

[0002] Currently, research and application of submersible pump motors both domestically and internationally mainly focus on asynchronous motors and permanent magnet synchronous motors, with asynchronous motors being the mainstream. The confined space in oil wells limits the size of the motor stator, restricting the number of poles and resulting in poor torque performance and low efficiency at low speeds. Factors such as downhole oil quality, viscosity, and sand content can cause asynchronous motors to overload. While permanent magnet synchronous motors offer improved operating efficiency compared to asynchronous motors, demagnetization of the permanent magnets can occur when operating in high-temperature environments.

[0003] In existing technologies, traditional power converters use an asymmetrical half-bridge structure, resulting in excessive and heavy power supply wires from the power converter to both ends of the motor windings. This causes inconvenience to downhole submersible motors and also increases costs. Traditional unipolar current conduction schemes result in low utilization of the motor stator windings and also cause problems such as reduced electromagnetic torque due to delays and deformation of commutation current. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a control method for a bipolar switched reluctance motor with distributed windings, which reduces the number of power supply lines of traditional switched reluctance motors and enables the operation of a bipolar switched reluctance motor with distributed windings for downhole oil wells.

[0005] The objective of this invention is achieved as follows: a control method for a bipolar switched reluctance motor with distributed windings, characterized by comprising the following steps:

[0006] 1) Select a suitable bipolar switched reluctance motor and adopt a distributed installation of the motor stator windings;

[0007] 2) Select a suitable power converter based on the bipolar switched reluctance motor, and connect the windings of each phase of the motor in a star connection manner;

[0008] 3) Divide the motor rotor position range according to the motor structure and the selected power converter, and formulate a scheme for the switching transistor to be turned on and off;

[0009] 4) After startup, the motor commutation is completed through two commutation control methods.

[0010] As a further limitation of the present invention, step 1) specifically includes selecting a three-phase 12 / 8 structure motor, adopting distributed installation of motor stator windings, placing only one phase coil in one stator slot, installing the coil across stator teeth, the number of stator teeth spanned is the same as the number of phases of the motor, and the number of stator teeth spanned by the coils of each phase A, B, and C is three; the winding conduction excitation voltage changes with the positive and negative positions of the motor rotor.

[0011] As a further limitation of the present invention, the power converter mentioned in step 2) is a three-phase full-bridge circuit. The three-phase full-bridge circuit includes three bridge arms, each of which is provided with two switching transistors and their anti-parallel diodes, namely switching transistors T1 and T2, diodes D1 and D2; switching transistors T3 and T4, diodes D3 and D4; switching transistors T5 and T6, diodes D5 and D6; the collector of switching transistor T1 is connected to the positive terminal of the main circuit, and the emitter of switching transistor T2 is connected to the negative terminal of the main circuit. The collector of transistor T2 is connected to one end of the A-phase winding of the motor; the collector of transistor T3 is connected to the positive terminal of the main circuit, the emitter of transistor T4 is connected to the negative terminal of the main circuit, and the emitter of transistor T3 and the collector of transistor T4 are connected to one end of the B-phase winding of the motor; the collector of transistor T5 is connected to the positive terminal of the main circuit, the emitter of transistor T6 is connected to the negative terminal of the main circuit, and the emitter of transistor T5 and the collector of transistor T6 are connected to one end of the C-phase winding of the motor; the other ends of the A, B, and C phase windings are connected to form a star connection.

[0012] As a further limitation of the present invention, step 3) specifically includes: according to the motor structure, the rotor position interval is divided into six intervals within one electrical cycle, the motor performs a commutation every 15°, and the position where the stator pole S1 and the rotor pole R1 are aligned is the 0 position. The power converter has six switching states. The power converter conduction signal, the relative position of the motor rotor and the winding current direction are shown in Table 1 below:

[0013] .

[0014] As a further limitation of the present invention, the two commutation control methods described in step 4) specifically include:

[0015] Commutation control method 1: When the motor is commutating, the switching state of the switch tubes of the bridge arm corresponding to the winding whose current flow direction changes is changed in the three-phase winding. The switching state of the switch tubes of the bridge arm corresponding to one phase winding remains unchanged in the winding whose current flow direction remains unchanged. The switch tubes of the bridge arm corresponding to the other phase winding are turned off at a certain angle and then turned on again to complete the commutation.

[0016] Commutation control method two: Keep the conduction range of each phase winding of the motor unchanged, and move the commutation position of the motor forward by a fixed angle; when the motor reaches the forward commutation position, the switching state of the switch tube of the bridge arm corresponding to the winding whose current flow direction has changed changes, while the switching state of the switch tube of the bridge arm corresponding to the other two phase windings remains unchanged, thus completing the commutation.

[0017] The present invention adopts the above technical solution, and compared with the prior art, the beneficial effects are as follows: 1) The selected 12 / 8 structure distributed winding bipolar switched reluctance motor, compared with asynchronous motor and synchronous motor, can still work normally at low speed and will not have high temperature demagnetization phenomenon; compared with traditional switched reluctance motor, it can generate greater electromagnetic torque; the use of four pole magnetic circuit, compared with 6 / 4 structure motor, the length of the end winding will be reduced, and the winding loss will be reduced accordingly.

[0018] 2) The power converter adopts a standard bridge structure and the winding adopts a star connection. Compared with the traditional asymmetrical half-bridge structure, the power converter can use a general-purpose IPM module, which reduces the cost. The number of wires connecting the power converter to the two ends of the motor winding is reduced from 6 to 3, avoiding the problem of too many and too heavy power supply wires. This brings greater convenience to the downhole submersible motor.

[0019] 3) The bipolar current conduction scheme is adopted. Compared with the unipolar current conduction scheme, it can output torque in more than half an inductor cycle, and the winding utilization rate is improved. The three phases are excited at the same time each time, making full use of the mutual inductance rising and falling regions, resulting in high motor output and high power density.

[0020] 4) Motor commutation control provides two methods that can effectively increase the average electromagnetic torque of the motor and solve the problem of reduced electromagnetic torque caused by the delay and deformation of commutation current. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the distributed winding bipolar switched reluctance motor winding distribution structure of the present invention.

[0022] Figure 2 This is a magnetic flux distribution diagram of the distributed winding bipolar switched reluctance motor of the present invention.

[0023] Figure 3 This is the power converter circuit topology used in this invention.

[0024] Figure 4 The curve showing the change in mutual inductance of the distributed winding bipolar switched reluctance motor windings according to the present invention.

[0025] Figure 5The present invention provides detailed schematic diagrams of six different conduction states of the power converter's switching transistors within one cycle and the current flow directions of the A, B, and C phase windings: (a) 0°~15° (b) 15°~30° (c) 30°~45° (d) 45°~60° (e) 60°~75° (f) 75°~90°.

[0026] Figure 6 The diagram below shows the curve of the three-phase winding excitation voltage changing with the rotor position and the current flow direction during phase C commutation in one cycle. (a) Curve of the three-phase winding excitation voltage changing with the rotor position (b) Current flow direction when the rotor rotates to 15°~19° (c) Current flow direction when the rotor rotates to 60°~64°.

[0027] Figure 7 This is the curve showing the change of the three-phase winding excitation voltage with rotor position under control method two of the present invention.

[0028] Figure 8 The torque variation curve is shown in the static finite element simulation of the distributed winding bipolar switched reluctance motor of this invention.

[0029] Figure 9 The torque variation curve of the distributed winding bipolar switched reluctance motor of the present invention under the commutation control method is shown in the transient finite element simulation.

[0030] Figure 10 The transient finite element simulation torque variation curve of the distributed winding bipolar switched reluctance motor of the present invention under commutation control method two. Detailed Implementation

[0031] like Figure 1-2 As shown, the distributed winding bipolar switched reluctance motor studied in this invention has a 12 / 8 structure, with only one phase winding in each stator slot, and each phase winding is not a concentrated winding method, but rather spans three stator tooth poles to form one phase winding of the motor. The distributed winding bipolar switched reluctance motor studied in this invention has a total of three phases.

[0032] like Figure 3 As shown, the circuit topology of the power converter used in a distributed winding bipolar switched reluctance motor is given in detail. The motor drive circuit is a three-phase full-bridge circuit. Taking the connection between the A-phase winding and the bridge arm of a three-phase 12 / 8 structure motor as an example: two switching transistors and their anti-parallel diodes are set on the bridge arm, namely switching transistors T1 and T2, and diodes D1 and D2; the collector of switching transistor T1 is connected to the positive terminal of the main circuit, and the emitter of switching transistor T2 is connected to the negative terminal of the main circuit. The emitter of switching transistor T1 and the collector of switching transistor T2 are connected to one end of the A-phase winding of the motor; the other end of the A-phase winding is connected to the other end of the B and C phase windings to form a star connection.

[0033] Based on the motor structure, the rotor position range is divided into six intervals within one electrical cycle. The motor commutates every 15°. The zero position is defined as the alignment of the stator pole S1 with the rotor pole R1. The power converter has six switching states. The power converter's on signal, the relative position of the motor rotor, and the winding current direction are shown in Table 1 below:

[0034]

[0035] like Figure 4 As shown, the mutual inductance variation curves of the distributed winding bipolar switched reluctance motor are presented in detail. The self-inductance of this motor is constant throughout the entire rotor cycle, so the torque of the motor is mainly generated through the variation of mutual inductance, which changes with the rotor position. The two commutation control schemes are proposed with reference to the mutual inductance variation curves.

[0036] like Figure 5 As shown in Figure (a), the diagram illustrates in detail the six different conduction states of the power converter's switching transistors within one cycle and the current flow directions of the A, B, and C phase windings. Figure (b) shows the following: In the 0°~15° range, switching transistors T1, T4, and T6 are on, phase A is forward energized, and phases B and C are reverse energized. (Note: The text repeats the same information multiple times.) As shown in Figure (c), within the 30°~45° range, switches T2, T4, and T5 are turned on, with phase C energized in the forward direction and phases A and B energized in the reverse direction. As shown in Figure (d), within the 45°~60° range, switches T2, T3, and T6 are turned on, with phases B and C energized in the forward direction and phase A energized in the reverse direction. As shown in Figure (e), within the 60°~75° range, switches T2, T3, and T6 are turned on, with phase B energized in the forward direction and phases A and C energized in the reverse direction. As shown in Figure (f), within the 75°~90° range, switches T1, T3, and T6 are turned on, with phases A and B energized in the forward direction and phase C energized in the reverse direction.

[0037] There are two control methods for a motor to complete commutation. Taking the motor rotor from position 0 to the completion of the first commutation as an example, that is, the switching transistor's conduction state changes from T1, T4, T6 to T1, T4, T5, the commutation control method is as follows:

[0038] Commutation control method 1: The phase difference between the motor rotor position and the commutation position is angular. θAt time 1, switch T1 is turned off and switch T5 is turned on. At this time, the current in coil A flows through freewheeling diode D2, coil B, and switch T4. Switch T1 is turned off at a certain angle. θ After step 2, conduction is resumed, completing the commutation.

[0039] Commutation control method two: Keep the conduction range of each phase winding of the motor unchanged, and move the commutation position of the motor forward by a fixed angle. θ 3; When the motor reaches the forward commutation position, switch T6 is turned off and switch T5 is turned on, realizing motor commutation.

[0040] like Figure 6 The diagram shows the curves of the three-phase winding excitation voltage changing with the rotor position and the current flow during phase C commutation within one cycle, according to the control method of this invention. (a) shows the curves of the three-phase winding excitation voltage changing with the rotor position. Taking phase C as an example within one cycle: the motor starts at position 0. When the motor rotor rotates to 15°, switches T1 and T6 are turned off, and switch T5 is turned on. At this time, the current in coil A flows through freewheeling diode D2, coil B, and switch T4, as shown in (b). After switch T1 is turned off for 4°, it is turned on again, completing the commutation. When the motor rotor rotates to 60°, switches T2 and T5 are turned off, and switch T6 is turned on. At this time, the current in coil A flows through freewheeling diode D1, coil B, and switch T3, as shown in (c). After switch T2 is turned off for 4°, it is turned on again, completing the commutation. The commutation schemes for phases A and B are similar to those for phase C.

[0041] like Figure 7 The figure shows the curves of the three-phase winding excitation voltage versus rotor position under control method two of this invention. Taking the rotor moving from position 0 to the completion of the first commutation as an example, that is, the switching transistors change from states T1, T4, T6 to T1, T4, T5, specifically: the conduction range of each phase winding remains unchanged, and the commutation position of the motor is moved forward by 30°. When the motor reaches the forward-moved commutation position, switch T6 is turned off, and switch T5 is turned on, realizing the motor commutation. Subsequent commutations are also performed in the same way, requiring only a change in the conduction state of one switch each time.

[0042] like Figure 8 As shown, two phases of a distributed winding bipolar switched reluctance motor are energized by applying opposite currents. The static finite element simulation curves of torque variation over two cycles are presented. Each phase coil has 160 turns. Phase A is energized with a forward current of 8.5A, and phase B with a reverse current of 8.5A. The current in phase C remains constant at 0. The finite element simulation results in a relatively large average electromagnetic torque, as can be seen from the figure.

[0043] like Figure 9The figure shows the torque variation curve in the next cycle for the first scheme. According to... Figure 6 The given conduction logic allows the motor to operate normally and generate torque.

[0044] like Figure 10 The figure shows the torque variation curve in the next cycle for the second scheme. According to... Figure 7 The given conduction logic allows the motor to operate normally, generating an average torque that is much greater than that of a traditional switched reluctance motor.

[0045] This invention employs a distributed winding bipolar switched reluctance motor and a three-phase full-bridge power converter, reducing the cost of the switched reluctance motor controller. The motor windings are connected in a star configuration, and the three-phase full-bridge circuit is connected to the winding leads. Combined with this power converter structure, two commutation control methods for the motor are proposed. This reduces the total number of motor leads compared to traditional switched reluctance motors, making it suitable for motor drives in long-distance power supply applications, such as downhole submersible motors.

[0046] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method of controlling a distributed winding bipolar switched reluctance machine, characterized by, The method comprises the following steps: 1) selecting a suitable bipolar switched reluctance motor, and adopting distributed installation of motor stator windings; 2) selecting a suitable power converter based on the bipolar switched reluctance motor, and connecting motor phase windings in a star connection mode; 3) dividing motor rotor position intervals and formulating a scheme of switch tube turn-on and turn-off according to motor structure and the selected power converter; 4) after starting, completing motor commutation through two commutation control methods; The two commutation control methods in step 4) specifically comprise: Commutation control method one: when the motor commutates, the switch state of the switch tube of the bridge arm corresponding to the winding in which the current flow direction changes is changed, the switch state of the switch tube of the bridge arm corresponding to the winding in which the current flow direction does not change remains unchanged, and the switch tube of the bridge arm corresponding to the other winding is turned off for a certain angle and then turned on again to complete commutation; Commutation control method two: the motor commutation position of each phase winding remains unchanged, and the motor commutation position is moved forward by a fixed angle; when the motor reaches the commutation position after moving forward, the switch state of the switch tube of the bridge arm corresponding to the winding in which the current flow direction changes is changed, and the switch state of the switch tube of the bridge arm corresponding to the other two windings remains unchanged to complete commutation.

2. A control method of a bipolar switched reluctance motor with distributed windings according to claim 1, characterized in that, Step 1) specifically comprises selecting a three-phase 12 / 8 structure motor, adopting distributed installation of motor stator windings, and installing only one phase coil in one stator slot, wherein the coil is installed across the stator teeth, the number of crossed stator teeth is the same as the number of motor phases, and the number of crossed stator teeth of A, B and C phase windings is three; the winding turn-on excitation voltage changes with the positive and negative change of the motor rotor position.

3. A control method of a bipolar switched reluctance motor with distributed windings according to claim 1, characterized in that, The power converter in step 2) is a three-phase full-bridge circuit, which comprises three bridge arms, each bridge arm is provided with two switch tubes and their anti-parallel diodes, namely switch tubes T1 and T2, diodes D1 and D2; switch tubes T3 and T4, diodes D3 and D4; switch tubes T5 and T6, diodes D5 and D6; the collector electrode of the switch tube T1 is connected to the positive electrode of the main circuit, the emitter electrode of the switch tube T2 is connected to the negative electrode of the main circuit, and the emitter electrode of the switch tube T1 and the collector electrode of the switch tube T2 are connected to one end of the A phase winding of the motor; the collector electrode of the switch tube T3 is connected to the positive electrode of the main circuit, the emitter electrode of the switch tube T4 is connected to the negative electrode of the main circuit, and the emitter electrode of the switch tube T3 and the collector electrode of the switch tube T4 are connected to one end of the B phase winding of the motor; the collector electrode of the switch tube T5 is connected to the positive electrode of the main circuit, the emitter electrode of the switch tube T6 is connected to the negative electrode of the main circuit, and the emitter electrode of the switch tube T5 and the collector electrode of the switch tube T6 are connected to one end of the C phase winding of the motor; the other ends of the A, B and C three-phase windings are connected to form a star connection mode.

4. A control method of a bipolar switched reluctance motor with distributed windings according to claim 1, characterized in that, Step 3) specifically comprises: according to the motor structure, dividing the rotor position interval into six intervals within one electrical cycle, and performing motor commutation once every 15°, taking the position of the alignment of the motor stator pole S1 and the rotor pole R1 as the 0 position, the power converter has six switch states in total, and the power converter conduction signal, motor rotor relative position and winding current direction are shown in Table 1: 。

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