Electric forklift six-phase motor driving system and control method

Abstract

The invention discloses an electric forklift six-phase motor driving system and a control method, and belongs to the technical field of electric forklift driving motor control systems, and the electric forklift six-phase motor driving system comprises a six-phase alternating current motor, a six-phase driving controller and a power battery. A first bridge arm, a second bridge arm and a third bridge arm of the six-phase driving controller are connected with a first winding of the six-phase alternating current motor, and a fourth bridge arm, a fifth bridge arm and a sixth bridge arm of the six-phase driving controller are connected with a second winding of the six-phase alternating current motor. The electric forklift has the advantages that the installation space problem and the control complexity of a low-voltage, large-tonnage and high-performance electric forklift are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric forklift drive motor control systems, and in particular to an electric forklift six-phase motor drive system and a control method. Background Art

[0002] As people's awareness of green environmental protection increases, the demand for electric forklifts is increasing. However, due to the special working conditions in some areas without high-voltage power batteries, large-tonnage electric counterbalanced forklifts can only use low-voltage power batteries below 96V. Due to the space layout and structure of the vehicle, only dual-drive solutions can be used. The dual-drive solution requires two drive motors and two drive controllers, which is relatively compact in space and more complex in control than single-drive, and has a higher failure rate. Summary of the invention

[0003] The present invention aims to solve the technical problems mentioned in the above background technology. In a first aspect, a six-phase motor drive system for an electric forklift is provided, which provides a simple and direct drive mode and drive system in a limited space and reduces the failure rate.

[0004] The second aspect provides a control method, which is applied to the six-phase motor drive system of the electric forklift provided in the first aspect, so that the electric forklift can be used in two walking conditions with large and small torques.

[0005] Based on the above purposes, the technical solution provided in the first aspect of the present invention is: a six-phase motor drive system for an electric forklift, comprising a six-phase AC motor, a six-phase drive controller and a power battery assembly, the power battery assembly being electrically connected to the six-phase drive controller, the six-phase drive controller being communicatively connected to the six-phase AC motor, the six-phase AC motor having a dual-winding structure, and the number of motor pole pairs of the second winding of the six-phase AC motor being greater than the number of motor pole pairs of the first winding.

[0006] In some embodiments, the first bridge arm, the second bridge arm and the third bridge arm of the six-phase drive controller are connected to the first winding of the six-phase AC motor, and the fourth bridge arm, the fifth bridge arm and the sixth bridge arm of the six-phase drive controller are connected to the second winding of the six-phase AC motor.

[0007] In some embodiments, the number of motor pole pairs of the second winding of the six-phase AC motor is twice the number of motor pole pairs of the first winding.

[0008] In some embodiments, the three phases of the first winding of the six-phase AC motor include a first U phase, a first V phase, and a first W phase, and the three phases of the second winding of the six-phase AC motor include a second U phase, a second V phase, and a second W phase. The first U phase and the second U phase are short-circuited, the first V phase and the second V phase are short-circuited, and the first W phase and the second W phase are short-circuited.

[0009] In some embodiments, the first bridge arm, the second bridge arm, and the third bridge arm of the six-phase drive controller are respectively connected to the first U phase, the first V phase, and the first W phase of the first winding of the six-phase AC motor, and the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm of the six-phase drive controller are respectively connected to the second U phase, the second V phase, and the second W phase of the second winding of the six-phase AC motor.

[0010] In some embodiments, the power battery assembly includes a low-voltage battery pack, a DC / DC converter and a high-voltage battery pack. The low-voltage battery pack is electrically connected to the high-voltage battery pack through the DC / DC converter, and the high-voltage battery pack is electrically connected to the six-phase drive controller.

[0011] In some embodiments, the six-phase AC motor is a dual-drive motor, and the input end of the six-phase AC motor is connected to the engine through an electromagnetic clutch transmission.

[0012] The second aspect of the present invention provides a control method. When the vehicle starts or is climbing a slope, the vehicle speed is low but the torque required by the whole vehicle is large. The six-phase drive controller judges the current working condition and turns off the output of the first bridge arm, the second bridge arm and the third bridge arm, and controls the second winding of the six-phase AC motor by controlling the fourth bridge arm, the fifth bridge arm and the sixth bridge arm. At this time, the pole pair number of the six-phase AC motor is in a high state, and the six-phase AC motor can output a large torque. At this time, the vehicle speed adjustment range is small.

[0013] Furthermore, when the vehicle is running smoothly and the required torque is small, when the vehicle speed needs to be increased, the six-phase drive controller judges the current operating conditions and turns off the output of the fourth bridge arm, the fifth bridge arm and the sixth bridge arm, and controls the first winding of the six-phase AC motor by controlling the first bridge arm, the second bridge arm and the third bridge arm. At this time, the pole pair number of the six-phase AC motor is in a lower state, and the six-phase AC motor can output a smaller torque. At this time, the vehicle speed adjustment range is higher.

[0014] The advantages of the present invention compared with the prior art are: 1. A six-phase AC motor with a dual winding structure is used, and the number of motor pole pairs of the second winding of the six-phase AC motor is greater than the number of motor pole pairs of the first winding. The second winding of the six-phase AC motor can provide a larger torque when driven, and the first winding of the six-phase AC motor can provide a larger speed regulation range when driven; 2. A control method for the system is provided, and the current working condition is judged by a six-phase drive controller to cope with different working conditions.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a connection diagram of a six-phase motor drive system according to an embodiment of the present invention; Figure 2 is a schematic diagram of the electrical architecture of a drive system according to an embodiment of the present invention; Figure 3 is a connection diagram of a six-phase AC motor and a six-phase drive controller according to an embodiment of the present invention; Figure 4 Schematic diagram of the structure of the first winding and the second winding of the six-phase AC motor according to an embodiment of the present invention; Figure 5 Schematic diagram of the relationship between the speed and torque of a six-phase AC motor according to an embodiment of the present invention; In the attached figure: 1. six-phase AC motor; 2. six-phase drive controller; 3. power battery assembly; 4. engine; 5. electromagnetic clutch; 6. travel pump; 7. proportional solenoid valve; 8. electric proportional controller; 9. drive motor; 31. Low-voltage battery pack; 32. DC / DC converter; 33. High-voltage battery pack; U11, first bridge arm; V11, second bridge arm; W11, third bridge arm; U22, fourth bridge arm; V22, fifth bridge arm; W22, sixth bridge arm; U1, first U phase; V1, first V phase; W1, first W phase; U2, second U phase; V2, second V phase; W2, second W phase. DETAILED DESCRIPTION

[0017] The present invention is described in further detail below.

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0019] Combination Figure 1 , Figure 2 As shown, a six-phase motor drive system for an electric forklift of the present embodiment includes a six-phase AC motor 1, a six-phase drive controller 2 and a power battery assembly 3. The power battery assembly 3 is electrically connected to the six-phase drive controller 2. The six-phase drive controller 2 is communicatively connected to the six-phase AC motor 1. The six-phase AC motor 1 is a dual-drive motor. The input end of the six-phase AC motor 1 is connected to the engine 4 through an electromagnetic clutch 5. The power battery assembly 3 includes a low-voltage battery pack 31, a DC / DC converter 32 and a high-voltage battery pack 33. The low-voltage battery pack 31 is electrically connected to the high-voltage battery pack 33 through the DC / DC converter 32, and the high-voltage battery pack 33 is electrically connected to the six-phase drive controller 2.

[0020] Combination Figure 3 , Figure 4As shown, the six-phase AC motor 1 has a double winding structure. If the number of motor pole pairs of the first winding of the six-phase AC motor 1 is n, the number of motor pole pairs of the second winding of the six-phase AC motor 1 is 2n.

[0021] The first winding three phases of the six-phase AC motor 1 include a first U phase U1, a first V phase V1, and a first W phase W1. The first U phase U1 and the second U phase U2 are short-circuited, the first V phase V1 and the second V phase V2 are short-circuited, and the first W phase W1 and the second W phase W2 are short-circuited to form a second winding.

[0022] The first bridge arm U11, the second bridge arm V11, and the third bridge arm W11 of the six-phase drive controller 2 are respectively connected to the first U phase U1, the first V phase V1, and the first W phase W1 of the first winding of the six-phase AC motor 1, and the fourth bridge arm U22, the fifth bridge arm V22, and the sixth bridge arm W22 of the six-phase drive controller 2 are respectively connected to the second U phase U2, the second V phase V2, and the second W phase W2 of the second winding of the six-phase AC motor 1.

[0023] Combination Figure 5 As shown, when the speed of the six-phase AC motor 1 is below 2,000 rpm, the second winding works with a large torque, which is suitable for climbing or starting conditions; especially when the speed range is within 700 rpm, it can provide peak torque, which is suitable for climbing conditions.

[0024] When the speed of the six-phase AC motor 1 is above 2,000 revolutions per minute, the first winding works, the torque is relatively low, and the speed regulation range is relatively large, which is suitable for flat road acceleration conditions.

[0025] The control method when using the six-phase motor drive system of an electric forklift is as follows: when the vehicle starts or is in a climbing condition, the vehicle speed is low, but the torque required by the entire electric forklift is large. The six-phase drive controller 2 determines the size of the torque required by the entire electric forklift, closes the output of the first bridge arm U11, the second bridge arm V11 and the third bridge arm W11, and controls the second winding of the six-phase AC motor 1 by controlling the fourth bridge arm U22, the fifth bridge arm V22 and the sixth bridge arm W22. At this time, the pole pair number of the six-phase AC motor 1 is in a high state, and the six-phase AC motor 1 can output a large torque, which is convenient for climbing or starting. At this time, the vehicle speed adjustment range is small.

[0026] When the vehicle is running smoothly and the required torque is small, when the vehicle speed needs to be increased, the six-phase drive controller 2 determines the working condition of the electric forklift at this time, turns off the output of the fourth bridge arm U22, the fifth bridge arm V22 and the sixth bridge arm W22, and controls the first winding of the six-phase AC motor 1 by controlling the first bridge arm U11, the second bridge arm V11 and the third bridge arm W11. At this time, the pole pair number of the six-phase AC motor 1 is in a low state, and the six-phase AC motor 1 can output a small torque. At this time, the vehicle speed adjustment range is relatively high, which is convenient for increasing the vehicle speed.

[0027] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A six-phase motor drive system for an electric forklift, characterized in that: The invention comprises a six-phase AC motor (1), a six-phase drive controller (2) and a power battery assembly (3), wherein the power battery assembly (3) is electrically connected to the six-phase drive controller (2), and the six-phase drive controller (2) is communicatively connected to the six-phase AC motor (1), wherein the six-phase AC motor (1) has a double-winding structure, and the number of motor pole pairs of the second winding of the six-phase AC motor (1) is greater than the number of motor pole pairs of the first winding.

2. The six-phase motor drive system for electric forklift according to claim 1, characterized in that: The first bridge arm (U11), the second bridge arm (V11) and the third bridge arm (W11) of the six-phase drive controller (2) are connected to the first winding of the six-phase AC motor (1), and the fourth bridge arm (U22), the fifth bridge arm (V22) and the sixth bridge arm (W22) of the six-phase drive controller (2) are connected to the second winding of the six-phase AC motor (1).

3. The six-phase motor drive system for electric forklift according to claim 1, characterized in that: The number of motor pole pairs of the second winding of the six-phase AC motor (1) is twice the number of motor pole pairs of the first winding.

4. The six-phase motor drive system for electric forklift according to claim 2, characterized in that: The three phases of the first winding of the six-phase AC motor (1) include a first U phase (U1), a first V phase (V1), and a first W phase (W1); the three phases of the second winding of the six-phase AC motor (1) include a second U phase (U2), a second V phase (V2), and a second W phase (W2); the first U phase (U1) and the second U phase (U2) are short-circuited, the first V phase (V1) and the second V phase (V2) are short-circuited, and the first W phase (W1) and the second W phase (W2) are short-circuited.

5. The six-phase motor drive system for electric forklift according to claim 4, characterized in that: The first bridge arm (U11), the second bridge arm (V11), and the third bridge arm (W11) of the six-phase drive controller (2) are respectively connected to the first U phase (U1), the first V phase (V1), and the first W phase (W1) of the first winding of the six-phase AC motor (1); the fourth bridge arm (U22), the fifth bridge arm (V22), and the sixth bridge arm (W22) of the six-phase drive controller (2) are respectively connected to the second U phase (U2), the second V phase (V2), and the second W phase (W2) of the second winding of the six-phase AC motor (1).

6. The six-phase motor drive system for electric forklift according to claim 1, characterized in that: The power battery assembly (3) comprises a low-voltage battery pack (31), a DC / DC converter (32) and a high-voltage battery pack (33); the low-voltage battery pack (31) is electrically connected to the high-voltage battery pack (33) via the DC / DC converter (32); and the high-voltage battery pack (33) is electrically connected to the six-phase drive controller (2).

7. The six-phase motor drive system for electric forklift according to claim 1, characterized in that: The six-phase AC motor (1) is a dual-drive motor, and the input end of the six-phase AC motor (1) is transmission-connected to the engine (4) via an electromagnetic clutch (5).

8. A control method, characterized in that: Applicable to the six-phase motor drive system for an electric forklift as described in any one of claims 1-7.

9. The control method according to claim 8, characterized in that: When the vehicle is starting or climbing a slope, the vehicle speed is low but the torque required by the vehicle is large. After judging the current working condition, the six-phase drive controller (2) turns off the output of the first bridge arm (U11), the second bridge arm (V11) and the third bridge arm (W11), and controls the second winding of the six-phase AC motor (1) by controlling the fourth bridge arm (U22), the fifth bridge arm (V22) and the sixth bridge arm (W22). At this time, the number of pole pairs of the six-phase AC motor (1) is high, and the six-phase AC motor (1) can output a large torque. At this time, the vehicle speed adjustment range is small.

10. The control method according to claim 8, characterized in that: When the vehicle is running smoothly and the required torque is small, when the vehicle speed needs to be increased, the six-phase drive controller (2) judges the current working condition and shuts down the output of the fourth bridge arm (U22), the fifth bridge arm (V22) and the sixth bridge arm (W22), and controls the first winding of the six-phase AC motor (1) by controlling the first bridge arm (U11), the second bridge arm (V11) and the third bridge arm (W11). At this time, the number of pole pairs of the six-phase AC motor (1) is in a relatively low state, and the six-phase AC motor (1) can output a relatively small torque. At this time, the adjustment range of the vehicle speed is relatively high.

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