Bidirectional series-parallel hybrid power tractor transmission system controller and control method

Abstract

The invention provides a bidirectional series-parallel hybrid power tractor transmission system controller and method, the controller comprises a high-voltage power battery, a battery management unit, a bidirectional converter, a generator, a motor, a diesel engine and a power distribution mechanism, the high-voltage power battery is connected with the battery management unit and the bidirectional converter; the bidirectional converter is connected with the generator and the motor, the engine controller is connected with the diesel engine, and the generator, the motor and the diesel engine are coaxially connected with wheels through a power distribution mechanism and related mechanical structures. The hybrid power system integrates the advantages of a serial hybrid power system and a parallel hybrid power system, and compared with a serial hybrid power system, the transmission route of mechanical power is increased; compared with a parallel connection mode, the transmission line of electric energy is increased, and meanwhile, bidirectional flow of power can be realized, so that multiple working modes exist, energy can be utilized and recycled to the maximum extent, and the efficiency of a transmission system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tractors, and in particular to a controller and a control method for a transmission system of a bidirectional parallel-parallel hybrid power tractor. Background Art

[0002] High-horsepower tractors are essential tools in agricultural production, and their performance directly impacts the efficiency and quality of agricultural production. With the continuous development of modern agriculture, demands for tractor efficiency, energy efficiency, environmental friendliness, and user comfort are increasing. Furthermore, the tractor's ability to prevent slippage in complex operating environments is crucial, especially in slippery conditions or when the vehicle is stuck, requiring enhanced safety and stability. Therefore, the development of a novel hybrid tractor transmission system and its control method is crucial for improving the tractor's overall performance.

[0003] Currently, tractor power systems are primarily categorized into traditional diesel, pure electric, hydrogen-electric hybrid, and series and parallel hybrid systems. While traditional diesel tractors are technologically mature, they suffer from low transmission efficiency, high fuel consumption, high noise levels, and environmental pollution. Among new energy tractors, pure electric tractors are limited by battery performance and charge retention in low-temperature environments; hydrogen-electric hybrid tractors face issues such as low energy density, insufficient hydrogen refueling facilities, and safety risks. While series hybrid tractors offer electric drive, they suffer from insufficient power and low transmission efficiency under high loads. While parallel hybrid tractors can utilize both the engine and electric motor, the engine's operating point struggles to maintain optimal operation, resulting in low fuel efficiency and potential jerking and shaking during driving. Regarding anti-skid control, existing tractors primarily address slippery surfaces or vehicle jams by adjusting tire pressure, shifting the center of gravity, or employing differential locks. However, these methods largely rely on driver experience and manipulation, lacking scientific and reliable reliability.

[0004] Existing tractor technology has numerous shortcomings in terms of transmission efficiency, environmental performance, driving comfort, and anti-skid control. Traditional diesel tractors have low transmission efficiency, resulting in high fuel consumption and severe environmental pollution. They are also noisy and uncomfortable to drive. While new energy tractors offer certain environmental advantages, pure electric tractors are limited by battery performance. Hydrogen-electric hybrid tractors suffer from low energy density and insufficient hydrogen refueling facilities. Series hybrid tractors suffer from insufficient power and low transmission efficiency under high-load conditions, while parallel hybrid tractors suffer from low fuel efficiency and jerky ride. Furthermore, existing anti-skid control strategies, which mostly rely on the driver's experience and operation, lack scientific and reliable principles and are unable to meet the requirements of modern agriculture for efficient, energy-saving, environmentally friendly, safe, and stable tractor operation. Summary of the Invention

[0005] To address the aforementioned technical issues, a controller and method for a bidirectional parallel-parallel hybrid tractor transmission system are provided. This invention effectively addresses the shortcomings of existing tractors in transmission efficiency, power performance, driving comfort, and anti-slip control, significantly improving their overall performance and meeting modern agriculture's requirements for high efficiency, energy conservation, environmental protection, and safe and stable operation.

[0006] The technical means adopted in the present invention are as follows:

[0007] A bidirectional parallel-parallel hybrid power tractor transmission system controller includes: a high-voltage power battery, a battery management unit, a bidirectional converter, a generator, an electric motor, a diesel engine and a power distribution mechanism, wherein:

[0008] The high-voltage power battery is connected to the battery management unit and the bidirectional converter, the bidirectional converter is connected to the generator and the electric motor, the engine controller is connected to the diesel engine, and the generator, electric motor and diesel engine are coaxially connected to the wheels through a power distribution mechanism and related mechanical structures.

[0009] Furthermore, the bidirectional converter and the engine controller realize network communication through the 100M Ethernet 100BASE-TX protocol. The protocol adopts full-duplex mode. The communicating parties can send and receive data at the same time. The maximum transmission distance is 100 meters. Information interaction is realized with the tractor vehicle controller and power distribution mechanism through Ethernet communication, relevant control instructions from the vehicle controller and power distribution mechanism are received, and relevant signal parameters of the permanent magnet synchronous motor are uploaded.

[0010] Furthermore, the relevant control instructions include cab control instructions and transmission working mode instructions; the relevant signal parameters include the speed, voltage, current and temperature of the permanent magnet synchronous motor.

[0011] Furthermore, the bidirectional converter adopts SIC power devices to form a three-phase three-level topology structure, including a signal acquisition unit, a central processing unit and a SIC power module, wherein:

[0012] The signal acquisition unit is used to collect the speed, voltage, current and temperature signals of the permanent magnet synchronous motor, including a digital quantity acquisition circuit, a temperature acquisition signal circuit, an analog quantity signal acquisition circuit, a rotary transformer signal acquisition circuit and an isolated power supply circuit;

[0013] The central processing unit is used to process the signals collected by the signal acquisition unit and generate control instructions, including a DSP processor, an FPGA processor, a pulse width modulation circuit and a drive feedback acquisition circuit;

[0014] The SIC power module is used to drive the permanent magnet synchronous motor according to the control instructions generated by the central processing unit, and includes a SIC device and a drive module.

[0015] Furthermore, the signal acquisition unit performs signal conditioning and filtering on analog signals related to the permanent magnet synchronous motor and control signals of the vehicle controller and the power distribution mechanism, and sends the processed signals to the central processing unit.

[0016] Furthermore, in the central processing unit:

[0017] The FPGA processor implements the operation logic control of the transmission system, samples and filters the signals transmitted by the signal acquisition unit, and sends them to the DSP processor after processing. At the same time, it modulates the PWM pulses, provides overcurrent and overvoltage protection, and performs external Ethernet communication.

[0018] The DSP processor controls the permanent magnet synchronous motor, protects the SIC module and the permanent magnet synchronous motor, and implements external Ethernet communication based on the signals transmitted by the FPGA processor.

[0019] The pulse width modulation circuit is used to generate the PWM control signal;

[0020] The drive feedback acquisition circuit is used to acquire the drive feedback signal.

[0021] Furthermore, the bidirectional parallel-parallel hybrid tractor transmission system includes six operating modes, namely, pure electric mode, pure oil mode, hybrid parallel mode, hybrid series mode, charging mode and maximum power mode, wherein:

[0022] The pure electric mode is when the battery-powered electric motor pulls the tractor to run, and is used for starting and low-speed and low-horsepower operation;

[0023] The pure oil mode is when the diesel engine directly drives the tractor to run, and is used when there is no electricity and high horsepower is required or when there is a fault;

[0024] In the hybrid series mode, the diesel engine drives the generator to generate electricity and the battery simultaneously supplies energy to the electric motor to drive the tractor;

[0025] In the hybrid parallel mode, the diesel engine and electric motor drive the tractor simultaneously;

[0026] The charging mode is to recover energy when going downhill or braking to drive the diesel generator to generate electricity and store it in the battery;

[0027] The maximum power mode is used in special situations where the tractor needs maximum power. Through the control strategy, the generator is converted into an electric motor, and the dual motors and the engine are used to drive the tractor to maximize power.

[0028] The present invention also provides a control method based on the above-mentioned bidirectional parallel-parallel hybrid tractor transmission system controller, comprising:

[0029] In the low-speed and low-horsepower range, it works in pure electric mode, with the power battery driving the electric motor through a bidirectional converter to drive the wheels. When the tractor brakes or goes downhill, the engine drives the generator to generate electricity and recover energy to charge the power battery.

[0030] In the medium-speed and high-horsepower range, the hybrid energy supply working mode is selected according to the actual situation. The battery and diesel engine can be used to drive the generator to generate electricity, and at the same time, the electric motor can be used to drive the wheels. The excess electricity generated by the generator can be stored in the power battery. The diesel engine can also establish a mechanical connection with the wheels and drive the wheels with the electric motor at the same time, or the diesel engine can drive the wheels alone and the electric motor can drive the wheels alone.

[0031] Under high-speed, high-horsepower or slipping conditions, the generator is converted into an electric motor through control strategy, and dual motors plus the engine are used to drive the wheels simultaneously to achieve maximum driving capacity output.

[0032] Furthermore, the control strategy adopts the maximum torque to current ratio (MTPA) control algorithm to calculate the optimal current value according to the given torque, as follows:

[0033] Under the dq axis, calculate the torque and current, the calculation formula is as follows:

[0034]

[0035] Among them, T e Represents electromagnetic torque, n p represents the pole pair number, ψ f Represents magnetic flux, L d , L q Indicates the d and q axis inductance, i d 、i q Represents d-axis and q-axis currents respectively; I s Indicates the motor current;

[0036] According to the Lagrange multiplier method, the auxiliary function is constructed as follows:

[0037]

[0038] Where G represents the auxiliary function and λ is the Lagrange multiplier, which is a parameter that balances the objective function (maximizing torque) and the constraint condition (current limit) during the optimization process. The optimal current distribution can be obtained by solving its derivative.

[0039] Taking partial derivatives of the constructed auxiliary function, we get:

[0040]

[0041] From the first two equations above, we get:

[0042]

[0043] Substituting the above formula into the torque equation, we get:

[0044]

[0045] Organize and get i q About T e Refer to the given equation, as follows:

[0046]

[0047] Taking the derivative of the above formula, we get:

[0048]

[0049] According to the Newton-Raphson iterative method for solving nonlinear equations, we can get i q 、i d The given values ​​are as follows:

[0050]

[0051] in, Represent the given values ​​of d-axis and q-axis current respectively.

[0052] Vector control requires calculation and setting of d and q axis currents, as follows:

[0053] WhenU s Lower than U smax When i is obtained from the maximum torque current ratio curve d At this time, since the output voltage is less than the maximum output voltage of the inverter, U smax with U s The difference Δe is greater than 0. After passing through the PI regulator and limiting, the weak magnetic compensation current i dweak is equal to 0, Equal to i d , Calculated from the constant torque formula, Used for vector control;

[0054] WhenU s Higher than U smax When the weak magnetic control mode is entered, U smax with U s The difference Δe is less than 0, so the weak magnetic compensation current i dweak Less than 0, i d The superposition of the current is given Still using the constant torque formula, Used for vector control.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] 1. This invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller that combines the advantages of series and parallel hybrid systems, adding transmission paths for both mechanical and electrical power, and achieving bidirectional power flow. This architecture enables flexible switching of operating modes based on varying operating conditions, thereby improving transmission efficiency, reducing fuel consumption, and minimizing environmental pollution.

[0057] 2. This invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller. In the low-speed, low-horsepower range, the system operates in pure electric mode, with the power battery driving the electric motor to drive the wheels. In the medium-speed, high-horsepower range, the system selects a hybrid power supply mode, using either battery and engine combined or engine alone. In high-speed, high-horsepower, or slipping conditions, the system uses both the dual motors and the engine to drive the wheels simultaneously. This flexible control strategy improves power performance and adapts to diverse operational requirements.

[0058] 3. The present invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller, which improves the power conversion efficiency and system stability by adopting a bidirectional converter with a three-phase three-level topology composed of SIC power devices.

[0059] 4. The present invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller, which optimizes the control strategy of the permanent magnet synchronous motor by adopting the maximum torque current ratio (MTPA) algorithm and the field weakening control algorithm, ensuring that the motor can operate efficiently under different working conditions, thereby improving motor efficiency and reducing energy loss.

[0060] 5. This invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller, which proposes a new control strategy for tractors on slippery roads. This strategy provides improved anti-slip performance and vehicle stability, enabling better traversal in muddy conditions. It represents a significant breakthrough in improving transmission efficiency, reducing air pollution, enhancing driving performance and comfort, and preventing slippage.

[0061] 6. The present invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller that implements network communication using the 100M Ethernet 100BASE-TX protocol, ensuring efficient information exchange between the controller and the vehicle controller and power distribution device, thereby improving the system's response speed and control accuracy.

[0062] 7. The present invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller, which simplifies the system structure, improves the efficiency of system operation, and reduces the weight and complexity of the system by integrating multiple control functions such as signal acquisition, central processing, and power modules.

[0063] Based on the above reasons, the present invention can be widely promoted in the fields of tractors and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0065] Figure 1 This is a diagram of the transmission system architecture of the bidirectional parallel-parallel hybrid tractor of the present invention.

[0066] Figure 2 This is a diagram of the hybrid electric transmission system architecture of the present invention.

[0067] Figure 3 This is a diagram of the bidirectional converter architecture of the present invention.

[0068] Figure 4 It is the working mode diagram of the tractor of the present invention.

[0069] Figure 5 This is the vector control flow chart of the present invention. DETAILED DESCRIPTION

[0070] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0071] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0072] like Figure 1 、 2 As shown, the present invention provides a bidirectional parallel-parallel hybrid tractor transmission system controller, comprising: a high-voltage power battery, a battery management unit, a bidirectional converter, a generator, an electric motor, a diesel engine and a power distribution mechanism, wherein:

[0073] The high-voltage power battery is connected to the battery management unit and bidirectional converter, which is connected to the generator and electric motor. The engine controller is connected to the diesel engine. The generator, electric motor, and diesel engine are coaxially connected to the wheels via a power distribution mechanism and related mechanical structures. In this embodiment, both the generator and electric motor are permanent magnet synchronous motors.

[0074] When specifically implemented, as a preferred embodiment of the present invention, Figure 2 As shown, the bidirectional converter and the engine controller realize network communication through the 100M Ethernet 100BASE-TX protocol. The protocol adopts full-duplex mode. The communicating parties can send and receive data at the same time. The maximum transmission distance is 100 meters. Information interaction is realized with the tractor vehicle controller and power distribution mechanism through Ethernet communication. The relevant control instructions (including cab control instructions and transmission working mode instructions) from the vehicle controller and the power distribution mechanism are received, and the relevant signal parameters of the permanent magnet synchronous motor (including the speed, voltage, current, and temperature of the permanent magnet synchronous motor) are uploaded.

[0075] When specifically implemented, as a preferred embodiment of the present invention, Figure 3 As shown, the bidirectional converter adopts SIC power devices to form a three-phase three-level topology structure, including a signal acquisition unit, a central processing unit and a SIC power module, wherein:

[0076] The signal acquisition unit is used to collect the speed, voltage, current and temperature signals of the permanent magnet synchronous motor, including a digital quantity acquisition circuit, a temperature acquisition signal circuit, an analog quantity signal acquisition circuit, a rotary transformer signal acquisition circuit and an isolated power supply circuit;

[0077] The central processing unit is used to process the signals collected by the signal acquisition unit and generate control instructions, including a DSP processor, an FPGA processor, a pulse width modulation circuit and a drive feedback acquisition circuit;

[0078] The SIC power module is used to drive the permanent magnet synchronous motor according to the control instructions generated by the central processing unit, and includes a SIC device and a drive module.

[0079] In specific implementation, as a preferred embodiment of the present invention, the signal acquisition unit conditions and filters the analog signals related to the permanent magnet synchronous motor and the control signals of the vehicle controller and the power distribution mechanism, and sends them to the central processing unit after processing.

[0080] In specific implementation, as a preferred embodiment of the present invention, in the central processing unit:

[0081] The FPGA processor implements the transmission system operation logic control, samples and filters the signals transmitted by the signal acquisition unit, and sends them to the DSP processor after processing. At the same time, it modulates the PWM pulses, provides overcurrent and overvoltage protection, and performs external Ethernet communication. In this embodiment, the FPGA processor uses the Kintex7 series chip to implement the transmission system logic control, network communication with the entire vehicle, realize data interaction with the DSP processor, receive the PWM comparison value of the DSP, perform pulse width modulation, output pulse signals to control the SIC device, collect drive feedback signals, collect the speed and angle of the permanent magnet motor, and implement overvoltage, overcurrent, and overtemperature protection of the permanent magnet motor.

[0082] The DSP processor controls the permanent magnet synchronous motor, protects the SIC module and the permanent magnet synchronous motor, and performs external Ethernet communication based on the signals transmitted by the FPGA processor. In this embodiment, the DSP processor uses the TMS320C6XXX series chip to implement the maximum torque-to-current ratio control algorithm and the field-weakening control algorithm of the permanent magnet synchronous motor. At the same time, it can interact with the FPGA processor for data, implement external Ethernet communication, and perform data recording and downloading, debugging and maintenance, etc.

[0083] The pulse width modulation circuit is used to generate the PWM control signal;

[0084] The drive feedback acquisition circuit is used to acquire the drive feedback signal.

[0085] When specifically implemented, as a preferred embodiment of the present invention, Figure 4 As shown, the bidirectional parallel-parallel hybrid tractor transmission system includes six operating modes, namely pure electric mode, pure oil mode, hybrid parallel mode, hybrid series mode, charging mode and maximum power mode, among which:

[0086] The pure electric mode is when the battery-powered electric motor pulls the tractor to run, and is used for starting and low-speed and low-horsepower operation;

[0087] The pure oil mode is when the diesel engine directly drives the tractor to run, and is used when there is no electricity and high horsepower is required or when there is a fault;

[0088] In the hybrid series mode, the diesel engine drives the generator to generate electricity and the battery simultaneously supplies energy to the electric motor to drive the tractor;

[0089] In the hybrid parallel mode, the diesel engine and electric motor drive the tractor simultaneously;

[0090] The charging mode is to recover energy when going downhill or braking to drive the diesel generator to generate electricity and store it in the battery;

[0091] The maximum power mode is used in special situations where the tractor needs maximum power. Through the control strategy, the generator is converted into an electric motor, and the dual motors and the engine are used to drive the tractor to maximize power.

[0092] The present invention also provides a control method based on the above-mentioned bidirectional parallel-parallel hybrid tractor transmission system controller, comprising:

[0093] In the low-speed and low-horsepower range, it works in pure electric mode, with the power battery driving the electric motor through a bidirectional converter to drive the wheels. When the tractor brakes or goes downhill, the engine drives the generator to generate electricity and recover energy to charge the power battery.

[0094] In the medium-speed and high-horsepower range, the hybrid energy supply working mode is selected according to the actual situation. The battery and diesel engine can be used to drive the generator to generate electricity, and at the same time, the electric motor can be used to drive the wheels. The excess electricity generated by the generator can be stored in the power battery. The diesel engine can also establish a mechanical connection with the wheels and drive the wheels with the electric motor at the same time, or the diesel engine can drive the wheels alone and the electric motor can drive the wheels alone.

[0095] Under high-speed, high-horsepower or slipping conditions, the generator is converted into an electric motor through control strategy, and dual motors plus the engine are used to drive the wheels simultaneously to achieve maximum driving capacity output.

[0096] In specific implementation, as a preferred embodiment of the present invention, the control strategy is to use the maximum torque current ratio (MTPA) control algorithm to calculate the optimal current value according to the given torque, as follows:

[0097] Under the dq axis, calculate the torque and current, the calculation formula is as follows:

[0098]

[0099] Among them, T e Represents electromagnetic torque, n p represents the pole pair number, ψ f Represents magnetic flux, L d , L q Indicates the d and q axis inductance, i d 、i q Represents d-axis and q-axis currents respectively; I s Indicates the motor current;

[0100] According to the Lagrange multiplier method, the auxiliary function is constructed as follows:

[0101]

[0102] Where G represents the auxiliary function and λ is the Lagrange multiplier, which is a parameter that balances the objective function (maximizing torque) and the constraint condition (current limit) during the optimization process. The optimal current distribution can be obtained by solving its derivative.

[0103] Taking partial derivatives of the constructed auxiliary function, we get:

[0104]

[0105] From the first two equations above, we get:

[0106]

[0107] Substituting the above formula into the torque equation, we get:

[0108]

[0109] Organize and get i q About T e Refer to the given equation, as follows:

[0110]

[0111] Taking the derivative of the above formula, we get:

[0112]

[0113] According to the Newton-Raphson iterative method for solving nonlinear equations, we can get i q 、i d The given values ​​are as follows:

[0114]

[0115] in, Respectively represent the given values ​​of d-axis and q-axis current;

[0116] Vector control requires calculation and setting of d and q axis currents, such as Figure 5 As shown, the details are as follows:

[0117] WhenU s Lower than U smax When i is obtained from the maximum torque current ratio curve d At this time, since the output voltage is less than the maximum output voltage of the inverter, U smax with U s The difference Δe is greater than 0. After passing through the PI regulator and limiting, the weak magnetic compensation current i dweak is equal to 0, Equal to i d , Calculated from the constant torque formula, Used for vector control;

[0118] WhenU s Higher than U smax When the weak magnetic control mode is entered, U smax with U s The difference Δe is less than 0, so the weak magnetic compensation current i dweak Less than 0, i d The superposition of the current is given Still using the constant torque formula, Used for vector control.

[0119] In this embodiment, the MTPA algorithm ensures that the stator current is minimized within the constant torque operating range, provided the motorized spindle outputs a given torque. When the motor operates at a specific torque, the stator current vector corresponding to any point on its constant torque trajectory produces the same torque. The closer the point on the curve is to the origin, the smaller the magnitude of the stator current vector corresponding to the torque. By connecting the minimum current points required for all different torque values, the motor's MTPA trajectory is obtained. Controlling the motor along this trajectory can achieve maximum torque per unit current.

[0120] In summary, in response to the special working conditions of wet and slippery roads and getting stuck during operation, a new anti-skid control strategy is adopted. Based on the advantages of the new transmission system and permanent magnet motor, the traditional traction control system is integrated into the controller of the permanent magnet synchronous motor, which can more directly adjust the control of the motor according to the needs, and at the same time, it can realize the optimal control strategy of the motor. It can also realize independent control of the motor according to the needs, and distribute the power centrally to achieve escape. The vehicle body electronic stability module is integrated with the brake unit of the electric motor. In order to solve the problem that the tires are prone to side slipping on wet and slippery roads during braking, better control of the vehicle body stability and anti-skid during braking can be achieved. The present invention can also realize automatic adjustment of tire pressure. According to the control strategy requirements for escape and anti-skid, the tire pressure can be automatically adjusted to change the contact area between the tire and the ground, thereby increasing or reducing friction and helping to better control the tractor.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional parallel-parallel hybrid tractor transmission system controller, characterized in that: include: High-voltage power batteries, battery management units, bidirectional converters, generators, electric motors, diesel engines, and power distribution mechanisms, including: The high-voltage power battery is connected to the battery management unit and the bidirectional converter, the bidirectional converter is connected to the generator and the electric motor, the engine controller is connected to the diesel engine, and the generator, electric motor and diesel engine are coaxially connected to the wheels through a power distribution mechanism and related mechanical structures.

2. A two-way parallel-parallel hybrid tractor transmission system controller according to claim 1, characterized in that: The bidirectional converter and the engine controller achieve network communication through the 100M Ethernet 100BASE-TX protocol. This protocol adopts full-duplex mode. The communicating parties can send and receive data simultaneously. The maximum transmission distance is 100 meters. Information exchange is achieved with the tractor vehicle controller and power distribution mechanism through Ethernet communication, and relevant control instructions from the vehicle controller and power distribution mechanism are received, and relevant signal parameters of the permanent magnet synchronous motor are uploaded.

3. A two-way parallel-parallel hybrid tractor transmission system controller according to claim 2, characterized in that: The relevant control instructions include cab control instructions and transmission working mode instructions; the relevant signal parameters include the speed, voltage, current and temperature of the permanent magnet synchronous motor.

4. The bidirectional parallel-parallel hybrid tractor transmission system controller according to claim 1, characterized in that: The bidirectional converter adopts SIC power devices to form a three-phase three-level topology structure, including a signal acquisition unit, a central processing unit and a SIC power module, wherein: The signal acquisition unit is used to collect the speed, voltage, current and temperature signals of the permanent magnet synchronous motor, including a digital quantity acquisition circuit, a temperature acquisition signal circuit, an analog quantity signal acquisition circuit, a rotary transformer signal acquisition circuit and an isolated power supply circuit; The central processing unit is used to process the signals collected by the signal acquisition unit and generate control instructions, including a DSP processor, an FPGA processor, a pulse width modulation circuit and a drive feedback acquisition circuit; The SIC power module is used to drive the permanent magnet synchronous motor according to the control instructions generated by the central processing unit, and includes a SIC device and a drive module.

5. A bidirectional parallel-parallel hybrid tractor transmission system controller according to claim 4, characterized in that: The signal acquisition unit performs signal conditioning and filtering on analog signals related to the permanent magnet synchronous motor and control signals of the vehicle controller and the power distribution mechanism, and sends the processed signals to the central processing unit.

6. A bidirectional parallel-parallel hybrid tractor transmission system controller according to claim 4, characterized in that: In the central processing unit: The FPGA processor implements the operation logic control of the transmission system, samples and filters the signals transmitted by the signal acquisition unit, and sends them to the DSP processor after processing. At the same time, it modulates the PWM pulses, provides overcurrent and overvoltage protection, and performs external Ethernet communication. The DSP processor controls the permanent magnet synchronous motor, protects the SIC module and the permanent magnet synchronous motor, and implements external Ethernet communication based on the signals transmitted by the FPGA processor. The pulse width modulation circuit is used to generate the PWM control signal; The drive feedback acquisition circuit is used to acquire the drive feedback signal.

7. The bidirectional parallel-parallel hybrid tractor transmission system controller according to claim 1, characterized in that: The bidirectional parallel-parallel hybrid tractor transmission system includes six operating modes, namely pure electric mode, pure oil mode, hybrid parallel mode, hybrid series mode, charging mode and maximum power mode, among which: The pure electric mode is when the battery-powered electric motor pulls the tractor to run, and is used for starting and low-speed and low-horsepower operation; The pure oil mode is when the diesel engine directly drives the tractor to run, and is used when there is no electricity and high horsepower is required or when there is a fault; In the hybrid series mode, the diesel engine drives the generator to generate electricity and the battery simultaneously supplies energy to the electric motor to drive the tractor; In the hybrid parallel mode, the diesel engine and electric motor drive the tractor simultaneously; The charging mode is to recover energy when going downhill or braking to drive the diesel generator to generate electricity and store it in the battery; The maximum power mode is used in special situations where the tractor needs maximum power. Through the control strategy, the generator is converted into an electric motor, and the dual motors and the engine are used to drive the tractor to maximize power.

8. A control method based on the bidirectional parallel-parallel hybrid tractor transmission system controller according to any one of claims 1 to 7, characterized in that: include: In the low-speed and low-horsepower range, it works in pure electric mode, with the power battery driving the electric motor through a bidirectional converter to drive the wheels. When the tractor brakes or goes downhill, the engine drives the generator to generate electricity and recover energy to charge the power battery. In the medium-speed and high-horsepower range, the hybrid energy supply working mode is selected according to the actual situation. The battery and diesel engine can be used to drive the generator to generate electricity, and at the same time, the electric motor can be used to drive the wheels. The excess electricity generated by the generator can be stored in the power battery. The diesel engine can also establish a mechanical connection with the wheels and drive the wheels with the electric motor at the same time, or the diesel engine can drive the wheels alone and the electric motor can drive the wheels alone. Under high-speed, high-horsepower or slipping conditions, the generator is converted into an electric motor through control strategy, and dual motors plus the engine are used to drive the wheels simultaneously to achieve maximum driving capacity output.

9. The control method according to claim 8, characterized in that: The control strategy adopts the maximum torque-to-current ratio control algorithm to calculate the optimal current value according to the given torque, as follows: Under the dq axis, calculate the torque and current, the calculation formula is as follows: Among them, T e Represents electromagnetic torque, n p represents the pole pair number, ψ f Represents magnetic flux, L d 、L q Indicates the d and q axis inductance, i d 、i q Represents d-axis and q-axis currents respectively; I s Indicates the motor current; According to the Lagrange multiplier method, the auxiliary function is constructed as follows: Where G represents the auxiliary function, and λ is the Lagrange multiplier, which is a parameter that balances the objective function and constraints during the optimization process. The optimal current distribution can be obtained by solving its derivative. Taking partial derivatives of the constructed auxiliary function, we get: From the first two equations above, we get: Substituting the above formula into the torque equation, we get: Organize and get i q About T e Refer to the given equation, as follows: Taking the derivative of the above formula, we get: According to the Newton-Raphson iterative method for solving nonlinear equations, we can get i q 、i d The given values ​​are as follows: in, Respectively represent the given values ​​of d-axis and q-axis current; Vector control requires calculation and setting of d and q axis currents, as follows: When U s Lower than U smax When i is obtained from the maximum torque current ratio curve d At this time, since the output voltage is less than the maximum output voltage of the inverter, U smax with U s The difference Δe is greater than 0. After passing through the PI regulator and limiting, the weak magnetic compensation current i dweak is equal to 0, Equal to i d , Calculated from the constant torque formula, Used for vector control; When U s Higher than U smax When the weak magnetic control mode is entered, U smax with U s The difference Δe is less than 0, so the weak magnetic compensation current i dweak Less than 0, i d The superposition of the current is given Still using the constant torque formula, Used for vector control.

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