Control method of motor driving system

Abstract

The invention provides a control method of a motor driving system. The control method is characterized by comprising the following steps: 1) respectively acquiring a peak external characteristic curve of a driving motor and a continuous external characteristic curve of the driving motor; 2) combining the peak external characteristic curve of the driving motor with the continuous external characteristic curve of the driving motor; 3) determining a first working area and a second working area in the combination curve; 4) performing improvement treatment on the combined curve to form an improved curve; and 5) determining a control strategy corresponding to the improved curve, by fusing the peak external characteristic curve of the driving motor and the continuous external characteristic curve of the driving motor, the maximum torque output and the small matching power of the system are considered, and the vehicle cost is reduced and the reliability and efficiency of the system are improved while the dynamic property requirement of the vehicle is met.

Description

Technical Field

[0001] The invention relates to the technical field of motor control strategies for mining trucks, and in particular to a control method for a motor drive system. Background Art

[0002] With the development trend of large-scale and unmanned mining equipment in modern times, large-tonnage electric-driven mining trucks have gradually replaced small and medium-tonnage internal combustion engine-driven mining trucks and become the mainstream product of mining trucks at this stage. As the loading mass of mining trucks increases, the output torque requirements of the drive system are increasing; at the same time, with the development of unmanned driving technology, the reliability requirements of the drive system are getting higher and higher, further requiring the drive system to shift less or even not shift gears. As a result, multi-motor deceleration drive, multi-motor two-gear drive, and multi-motor three-gear drive products came into being.

[0003] Existing multi-motor drive products generally have motors with the same external characteristics. The external characteristic curve of a single motor is as follows: Figure 1 As shown in the figure, the control strategy is: the motor speed is determined by the vehicle speed and gear position, the motor output torque and power are determined by the driver's throttle depth, and when the throttle is fully depressed, all motors output peak torque. When the motor or inverter temperature is too high, the output torque and power of the drive motor will be actively reduced. The defects of this control strategy include: (1) The multi-motor system configuration results in excessive power matching of the power generation module or energy storage unit, which in turn leads to higher cost of the entire vehicle.

[0004] (2) The motor and inverter frequently operate under overload conditions, resulting in reduced reliability and shorter fatigue life of the motor and inverter.

[0005] (3) The motor and inverter frequently operate under overload conditions, resulting in poor working efficiency of the motor and inverter, high system energy consumption, and poor vehicle economy.

[0006] Therefore, there is an urgent need to provide a control method for a motor drive system to solve the defects and shortcomings in the above-mentioned prior art. Summary of the invention

[0007] In order to solve the above defects and shortcomings in the prior art, the present invention provides a control method for a motor drive system.

[0008] The technical solution provided by the present invention is: A control method for a motor drive system, characterized in that it comprises the following steps: 1) Obtain the peak external characteristic curve and the continuous external characteristic curve of the drive motor respectively; 2) Combine the peak external characteristic curve of the drive motor and the continuous external characteristic curve of the drive motor; 3) determining a first working region and a second working region in the binding curve; 4) Improving the combined curve to form an improved curve; 5) Determine the control strategy corresponding to the improvement curve.

[0009] As a further preferred embodiment of the present invention, in the step 1), the peak external characteristic curve of the driving motor and the continuous external characteristic curve of the driving motor are detected from bench tests, their left vertical coordinates are the per-unit value of the motor torque, the right vertical coordinates are the per-unit value of the motor power, the horizontal coordinates are the per-unit value of the motor speed, and the inflection point speed is set accordingly as needed.

[0010] As a further preferred embodiment of the present invention, in the step 1), in the peak external characteristic curve of the driving motor, as the motor speed continues to increase, the motor peak torque first remains unchanged from the initial peak torque and then gradually decreases; as the motor speed continues to increase, the motor peak power increases from zero to the peak power, then maintains the peak power unchanged, and then gradually decreases from the peak power.

[0011] As a further preferred embodiment of the present invention, in the step 1), in the continuous external characteristic curve of the driving motor, as the motor speed continues to increase, the continuous torque of the motor first remains unchanged from the initial continuous torque, and then gradually decreases; as the motor speed continues to increase, the continuous power of the motor increases from zero to the continuous power, then maintains the continuous power unchanged, and then gradually decreases from the continuous power.

[0012] As a further preferred embodiment of the present invention, the continuous power is lower than the peak power, and the initial continuous torque is lower than the initial peak torque.

[0013] As a further preferred embodiment of the present invention, in step 3), the speed dividing line between the first working area and the second working area satisfies: at this speed, the motor peak power corresponding to the motor peak torque is equal to the maximum value of the motor continuous power.

[0014] As a further preferred embodiment of the present invention, in step 4), when the combined curve is improved to form an improved curve, the use of the first working area is retained and the use of the second working area is avoided.

[0015] As a further preferred embodiment of the present invention, in step 5), the control strategy includes: the rotation speed of the motor is determined by the vehicle speed and the gear position, and the output torque and power of the motor are determined by the throttle depth of the driver.

[0016] As a further preferred embodiment of the present invention, in step 5), the control strategy further includes: when the accelerator is stepped on to the bottom, the torque output by the motor at this time satisfies: When the motor speed is within the range of (0, first inflection point speed), the motor outputs peak torque; When the motor speed is within the range of [first inflection point speed, second inflection point speed), the motor outputs transition torque; When the motor speed is within the range of [second inflection point speed, maximum speed), the motor outputs continuous torque; When the throttle depth is between (0%, 100%), the motor output torque is proportional to the three conditions from 0 to the throttle bottom.

[0017] As a further preferred embodiment of the present invention, the method is used in a single-motor or multi-motor drive system.

[0018] Compared with the prior art, the technical effects achieved by the present invention include: 1) The present invention provides a control method for a motor drive system, which reduces the power configuration of the power generation module and the power configuration of the energy storage device of the whole vehicle while meeting the power requirements of the drive system, thereby reducing the production cost of the whole vehicle.

[0019] 2) The present invention provides a control method for a motor drive system. The drive system may operate in an overload condition only when the vehicle starts and climbs a steep slope for a short distance. After reaching a certain vehicle speed, the drive system is not in an overload condition. At this time, the operating temperature of the drive motor and inverter is low and controllable, which increases the reliability and fatigue life of the system to a certain extent.

[0020] 3) The present invention provides a control method for a motor drive system. In actual work, the vehicle runs at medium to high speeds in most cases, and the corresponding motor speed is medium to high speed. At this time, the working point of the drive system is more easily concentrated in the high-efficiency area, thereby reducing the vehicle's operating energy consumption and improving the economy of vehicle operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the peak external characteristic curve of the driving motor in the prior art.

[0022] Figure 2 It is a schematic diagram of the continuous external characteristic curve of the driving motor in the prior art.

[0023] Figure 3 It is a schematic diagram of the binding curve provided in the present invention; Figure 4 It is a schematic diagram of the improved curve provided in the present invention; Figure 5 It is a schematic diagram of the motor braking characteristic curve of the drive system provided in the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] [First embodiment] like Figure 1-4 The first embodiment of the present invention is shown, which provides a control method for a motor drive system, comprising the following steps: 1) Obtain the peak external characteristic curve and the continuous external characteristic curve of the drive motor respectively; Figure 1-2 As shown, there are schematic diagrams of the peak external characteristic curve of the drive motor and the continuous external characteristic curve of the drive motor, respectively. The peak external characteristic curve of the drive motor and the continuous external characteristic curve of the drive motor can be detected from the bench test. The left vertical axis is the per-unit value of the motor torque, the right vertical axis is the per-unit value of the motor power, and the horizontal axis is the per-unit value of the motor speed. The inflection point speed is set accordingly according to needs, and is generally between 0.25 and 0.6 per-unit values.

[0028] like Figure 1The figure shows the peak external characteristic curve of the drive motor. The peak external characteristic of the drive motor refers to the maximum torque and maximum power that can be output at different operating speeds by the power device that outputs the rotating mechanical power. Under normal circumstances, the power device cannot continuously output the maximum torque and maximum power due to unstable heating. It can be seen from the figure that as the motor speed continues to increase, the peak torque of the motor remains unchanged from the initial peak torque of 1.00, and then gradually decreases; as the motor speed continues to increase, the peak power of the motor increases from zero to a peak power of 1.00, and then maintains the peak power unchanged, and then gradually decreases from the peak power.

[0029] like Figure 2 The figure shows the continuous external characteristic curve of the drive motor. The continuous external characteristic of the drive motor refers to the maximum torque and maximum power that can be continuously output (continuously working for more than 2 hours until the device reaches thermal equilibrium) at different operating speeds for the power device that outputs rotating mechanical power. As can be seen from the figure, in the continuous external characteristic curve of the drive motor, as the motor speed continues to increase, the motor continuous torque first remains unchanged from the initial continuous torque of 0.50, and then gradually decreases; as the motor speed continues to increase, the motor continuous power increases from zero to a continuous power of 0.80, then maintains the continuous power unchanged, and then gradually decreases from the continuous power.

[0030] Combination Figure 1-2 It can be seen that the continuous power is lower than the peak power, and the initial continuous torque is lower than the initial peak torque. When the drive motor works within the continuous external characteristic curve, the continuous power of the drive motor is lower than the peak power (generally only 60%~80% of the peak power). At the same time, not only will the temperature of the drive motor and inverter not overheat, but the system efficiency is higher than the peak area. However, its disadvantages are also obvious. The maximum torque of the drive motor when working within the continuous external characteristic curve is low, generally only 40%~60% of the peak torque, resulting in insufficient ability of mining trucks to escape and climb steep slopes, thus breaking down.

[0031] Therefore, it is necessary to combine the low-speed and high-torque characteristics of the peak external characteristics of the drive motor with the low-power, low-loss and high-efficiency characteristics of the continuous external characteristics.

[0032] 2) Combine the peak external characteristic curve of the drive motor and the continuous external characteristic curve of the drive motor; the combined curve after combination is as follows: Figure 3 As shown; 3) Determine the first working area I and the second working area II in the combined curve; in this embodiment, the speed dividing line between the first working area and the second working area satisfies: at this speed, the motor peak power corresponding to the motor peak torque is equal to the maximum value of the motor continuous power, Figure 3 In the figure, the dividing line is exactly at the position where the rotation speed is 0.2 per unit; 4) Improve the combined curve to form an improved curve; the improved curve of the external characteristic of the drive motor after the improvement is as follows: Figure 4 As shown, in order to fully integrate the advantages of the peak external characteristic curve and the continuous external characteristic curve, it is necessary to retain the use of the first working area and avoid the use of the second working area. It is worth noting that after the second working area is discarded, there needs to be a transition torque between the peak torque and the continuous torque inflection point. The transition torque is based on the unchanged maximum continuous power value, and the transition torque value at different speeds can be calculated.

[0033] 5) Determine the control strategy corresponding to the improvement curve.

[0034] The control strategy includes: the motor speed is determined by the vehicle speed and gear, and the motor output torque and power are determined by the driver's throttle depth. It is the same as the control strategy in the prior art.

[0035] At the same time, the difference from the control strategy in the prior art is that the control strategy also includes: when the accelerator is stepped on to the bottom, the torque output by the motor at this time satisfies: When the motor speed is within the range of (0, first inflection point speed), the motor outputs peak torque; When the motor speed is within the range of [first inflection point speed, second inflection point speed), the motor outputs transition torque; When the motor speed is within the range of [second inflection point speed, maximum speed), the motor outputs continuous torque; and meets the conditions of 0<first inflection point speed<second inflection point speed<maximum speed; Figure 4 It can be seen that in this embodiment, the first inflection point speed is 0.2, the second inflection point speed is 0.4, and the maximum speed is 1.0; When the throttle depth is between (0%, 100%), the motor output torque is proportional to the three conditions from 0 to the throttle bottom.

[0036] A control method for a motor drive system provided in this embodiment takes into account the maximum torque output and smaller matching power of the system by integrating the peak external characteristic curve of the drive motor with the continuous external characteristic curve of the drive motor. While meeting the vehicle's power requirements, it reduces vehicle costs and improves system reliability and efficiency.

[0037] As a further preferred and promoted implementation method, the method can also be applied to the drive systems of electric vehicles in other fields, such as electric-driven passenger cars, electric-driven commercial vehicles, electric-driven construction machinery, electric-driven agricultural machinery, etc.

[0038] This method is applicable to multi-motor drive systems and can also be used in single-motor drive systems with limited discharge power of power generation systems or energy storage units.

[0039] The motor torque per unit value and motor power per unit value of this control method are set to negative values, and the speed range and relationship remain unchanged, which is the energy recovery braking control strategy of the drive system. At this time, the brake pedal (or other electric brake operating devices, such as brake lever, etc.) replaces the accelerator pedal. Different pedal depths correspond to the motor braking torque in three cases, such as Figure 5 shown.

[0040] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A control method for a motor drive system, characterized in that: The following steps are involved: 1) Obtain the peak external characteristic curve and the continuous external characteristic curve of the drive motor respectively; 2) Combine the peak external characteristic curve of the drive motor and the continuous external characteristic curve of the drive motor; 3) determining a first working region and a second working region in the binding curve; 4) Improving the combined curve to form an improved curve; 5) Determine the control strategy corresponding to the improvement curve.

2. The control method of a motor drive system according to claim 1, characterized in that: In the step 1), the peak external characteristic curve of the driving motor and the continuous external characteristic curve of the driving motor are detected from the bench test, the left vertical coordinates of which are the per-unit value of the motor torque, the right vertical coordinates are the per-unit value of the motor power, the horizontal coordinates are the per-unit value of the motor speed, and the inflection point speed is set accordingly as needed.

3. The control method of a motor drive system according to claim 2, characterized in that: In the step 1), in the peak external characteristic curve of the driving motor, as the motor speed continues to increase, the motor peak torque first remains unchanged from the initial peak torque and then gradually decreases; as the motor speed continues to increase, the motor peak power increases from zero to the peak power, then maintains the peak power unchanged, and then gradually decreases from the peak power.

4. The control method of a motor drive system according to claim 3, characterized in that: In the step 1), in the continuous external characteristic curve of the driving motor, as the motor speed continues to increase, the motor continuous torque first remains unchanged from the initial continuous torque and then gradually decreases; as the motor speed continues to increase, the motor continuous power increases from zero to the continuous power, then maintains the continuous power unchanged, and then gradually decreases from the continuous power.

5. The control method of a motor drive system according to claim 4, characterized in that: The continuous power is lower than the peak power, and the initial continuous torque is lower than the initial peak torque.

6. The control method of a motor drive system according to claim 1, characterized in that: In the step 3), the speed dividing line between the first working area and the second working area satisfies: at this speed, the peak power of the motor corresponding to the peak torque of the motor is equal to the maximum value of the continuous power of the motor.

7. The control method of a motor drive system according to claim 1, characterized in that: In the step 4), when the combined curve is improved to form an improved curve, the use of the first working area is retained and the use of the second working area is avoided.

8. The control method of a motor drive system according to claim 1, characterized in that: In step 5), the control strategy includes: the rotation speed of the motor is determined by the vehicle speed and the gear position, and the output torque and power of the motor are determined by the throttle depth of the driver.

9. The control method of a motor drive system according to claim 8, characterized in that: In step 5), the control strategy further includes: when the accelerator is stepped on to the bottom, the torque output by the motor at this time satisfies: When the motor speed is within the range of (0, first inflection point speed), the motor outputs peak torque; When the motor speed is within the range of [first inflection point speed, second inflection point speed), the motor outputs transition torque; When the motor speed is within the range of [second inflection point speed, maximum speed), the motor outputs continuous torque; and satisfies 0<first inflection point speed<second inflection point speed<maximum speed; When the throttle depth is between (0%, 100%), the motor output torque is proportional to the three conditions from 0 to the throttle bottom.

10. A control method for a motor drive system according to any one of claims 1 to 9, characterized in that: The method is used in a single-motor or multi-motor drive system.

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