Power supply system for electric tractor and electric tractor

Abstract

The present invention discloses a power supply system for an electric tractor and an electric tractor, and relates to the technical field of electric power equipment. The high-voltage system of the power supply system includes: a rectifier, a high-voltage distribution box, a step-down transformer and a controller. The rectifier is used to convert the alternating current transmitted to the high-voltage system into direct current, and the output positive pole of the output end of the rectifier is configured with a first positive relay, and the output negative pole of the output end of the rectifier is configured with a first negative relay; the high-voltage distribution box is connected to the output end of the rectifier, and the high-voltage distribution box is used to distribute the direct current transmitted by the rectifier to the operating parts; the output end of the step-down transformer is connected to the input end of the rectifier, and is used to step down the alternating current; the controller is used to control the first positive relay and the first negative relay to be disconnected at the same time when the high-voltage system is under high voltage, so that the voltage difference between the output end of the rectifier and the electric tractor is lower than the first preset threshold value. The above scheme can improve the safety of power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy agricultural machinery, and in particular to a power supply system for an electric tractor and an electric tractor. Background Art

[0002] In recent years, the green and sustainable development of agriculture has been vigorously promoted. The replacement of traditional diesel agricultural machinery with new energy agricultural machinery has become an industry development trend, and efficient, intelligent and environmentally friendly agricultural power machinery has become the main direction of global agricultural machinery technology innovation. High-horsepower electric tractors are mainly used for agricultural production activities. They are powerful vehicles designed for farmland operations. Compared with traditional fuel tractors, electric tractors have the characteristics of zero emissions, low noise and low maintenance costs. Existing high-horsepower electric tractors include two power supply modes, pure electric mode and hybrid mode. In the pure electric mode, the electric energy stored in the on-board power battery is used as the vehicle power source, and the motor converts the electric energy into mechanical energy for use. The hybrid mode includes two power sources, the power battery and the engine. When the power battery is sufficient to maintain the operation of the whole machine, the engine stops working and the battery directly powers the whole machine. When the battery power is insufficient to maintain the operation of the whole machine, the engine starts, burns fuel to generate mechanical energy, the generator converts the mechanical energy of the engine into electrical energy, and the rectifier converts the alternating current of the generator into direct current to power the whole machine and charge the battery pack at the same time. There is also a grid power supply mode. In this mode, there is a transformer in the system. The three-phase AC power at the rear end of the transformer is converted into DC power through a rectifier to power the entire machine. In this mode, after the high voltage of the entire vehicle is powered on, like a conventional rectifier that only disconnects the output positive pole, the front and rear circuits cannot be completely cut off, and there will still be a voltage difference between the rectifier output end and the frame (ground). Once any high-voltage circuit is touched, it is easy to cause an electric shock accident. Summary of the invention

[0003] The purpose of the embodiment of the present invention is to provide a power supply system for an electric tractor, so as to solve the technical problem in the prior art that electric shock accidents are easily caused.

[0004] In order to achieve the above object, the first aspect of the present invention provides a power supply system for an electric tractor, the power supply system comprising a high voltage system, the high voltage system being installed on the electric tractor, and the high voltage system comprising:

[0005] A rectifier, the rectifier comprises an output end and an input end, the output end comprises an output positive electrode and an output negative electrode, the rectifier is used to convert the alternating current transmitted to the high voltage system into direct current, wherein the output positive electrode of the rectifier is configured with a first positive electrode relay, and the output negative electrode of the rectifier is configured with a first negative electrode relay;

[0006] A high-voltage distribution box is connected to the output end of the rectifier, and is used to distribute the direct current transmitted by the rectifier to the operating parts of the electric tractor;

[0007] A step-down transformer, the output end of which is connected to the input end of the rectifier, for stepping down the AC power transmitted to the high-voltage system;

[0008] The vehicle controller is connected to the first positive relay and the first negative relay respectively. The vehicle controller is used to control the first positive relay and the first negative relay to be disconnected at the same time when the high-voltage system is under high voltage, so that the voltage difference between the output end of the rectifier and the electric tractor is lower than a first preset threshold value.

[0009] In an embodiment of the present invention, the input end of the rectifier further includes a filter capacitor and a discharge resistor connected in parallel, the filter capacitor is used to filter the AC component in the rectifier circuit of the rectifier, and the discharge resistor is used to dissipate the energy stored in the filter capacitor.

[0010] In an embodiment of the present invention, the connection mode of the windings of the step-down transformer is DY11.

[0011] In an embodiment of the present invention, the step-down transformer includes an incoming line terminal and an outgoing line terminal. The connection mode of the incoming line terminal is a triangle connection, and the connection mode of the outgoing line terminal is a star connection without a neutral line. The outgoing line terminal is configured with a first circuit breaker, and the first circuit breaker is used to cut off the line of the high-voltage system when an overcurrent or short circuit occurs in the high-voltage system.

[0012] In an embodiment of the present invention, the power supply system also includes a power grid distribution cabinet, a step-up transformer, and a high-voltage switch cabinet connected in sequence according to the power supply direction. The output end of the high-voltage switch cabinet is connected to the input end of the step-down transformer. The step-up transformer is fixedly installed on the ground. The connection method of the winding of the step-up transformer is YNd11. The connection method between the primary side of the step-up transformer and the power grid distribution cabinet is a star connection. The connection method between the secondary side of the step-up transformer and the high-voltage switch cabinet is a triangle connection. The power grid distribution cabinet is equipped with a second circuit breaker, which is used to disconnect the circuit when a leakage is detected.

[0013] In an embodiment of the present invention, the high-voltage system also includes a reel device, the high-voltage switch cabinet is connected to the step-down transformer through a transmission cable, and the reel device is used to reel in and out the transmission cable; a reel controller is connected to the reel device, the reel controller is connected to the third switch of the high-voltage distribution box, and the third switch is connected in series with the third positive relay of the high-voltage distribution box.

[0014] In an embodiment of the present invention, the output positive electrode of the rectifier is further configured with a first pre-charging relay connected in parallel with the first positive electrode relay, and a first pre-charging resistor connected in series with the first pre-charging relay.

[0015] In an embodiment of the present invention, the high-voltage distribution box also includes a first positive branch, a second positive branch and a negative main circuit. The first positive branch is configured with a third positive relay, the second positive branch is configured with a fourth positive relay and a second pre-charging relay, and the negative main circuit is configured with a second negative relay.

[0016] In an embodiment of the present invention, the high-voltage distribution box also includes a positive main circuit, which is equipped with a first switch for disconnecting the circuit when the switch is open, connecting the circuit when the switch is closed, and fusing the circuit when the circuit is short-circuited.

[0017] In an embodiment of the present invention, the high-voltage system also includes a braking unit and a braking resistor connected to the high-voltage distribution box, and the vehicle controller is also configured to: monitor the voltage at the DC end of the high-voltage system, so that the braking unit connects the circuit between the braking resistor and the braking unit when the voltage at the DC end is greater than a second preset threshold value, so as to convert electrical energy into heat energy through the braking resistor.

[0018] A second aspect of the present application provides an electric tractor, provided with the above-mentioned power supply system for an electric tractor.

[0019] Through the above technical solution, the power supply system includes a high-voltage system, which is installed on the electric tractor. The high-voltage system includes: a rectifier, a high-voltage distribution box, a step-down transformer and a controller. The rectifier is used to convert the alternating current transmitted to the high-voltage system into direct current, and the output positive pole of the rectifier output end is configured with a first positive relay, and the output negative pole of the rectifier output end is configured with a first negative relay; the high-voltage distribution box is connected to the output end of the rectifier, and the high-voltage distribution box is used to distribute the direct current transmitted by the rectifier to the operating parts; the output end of the step-down transformer is connected to the input end of the rectifier, and is used to step down the alternating current; the controller is used to control the first positive relay and the first negative relay to be disconnected at the same time when the high-voltage system is in a high-voltage power-down state, so that the voltage difference between the output end of the rectifier and the electric tractor is lower than the first preset threshold value. The above solution can improve the safety of high-voltage power supply of electric tractors.

[0020] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0022] Figure 1 An electrical schematic diagram of a power supply system for an electric tractor according to an embodiment of the present invention is schematically shown;

[0023] Figure 2 Schematically shows an electrical connection diagram of a power supply system for an electric tractor according to an embodiment of the present invention;

[0024] Figure 3 The electrical connection diagram of a power supply system for an electric tractor according to another embodiment of the present invention is schematically shown.

[0025] Description of Reference Numerals

[0026] 110-rectifier, 2-second step-down transformer, 120-high-voltage distribution box, C0-filter capacitor, 130-vehicle VCU, R0-discharge resistor, 140-step-down transformer, R1-first pre-charge resistor, 150-grid distribution cabinet, R2-second pre-charge resistor, 160-boost transformer, K1-first positive relay, 170-high-voltage switch cabinet, K2-first pre-charge relay, 180-reel device, K3-first negative relay, 190-transmission cable, K4-third positive relay, 210-brake unit, K5-fourth positive relay, 220-brake resistor, K6-second pre-charge relay, 230-three-in-one Controller, K7-second negative pole relay, 10-brake motor, QF1-second circuit breaker, 20-steering motor, QF2-third circuit breaker, 30-low-voltage battery, QF3-first circuit breaker, 40-oil pump motor controller, QS1-upper isolating knife switch, 41-oil pump motor, F1-first switch, 50 travel motor controller, F2-second switch, 51-travel motor, F3-third switch, 60-operating motor controller, F4-fourth switch, 61-operating motor, F5-fifth switch, 70-winding motor, F6-sixth switch, 1-first step-down transformer, 2-second step-down transformer, 181-reel controller. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0029] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] Figure 1 The electrical schematic diagram of a power supply system for an electric tractor according to an embodiment of the present invention is schematically shown. Figure 1 As shown, an embodiment of the present invention provides a power supply system for an electric tractor, the power supply system includes a high-voltage system, the high-voltage system is installed on the electric tractor, and the high-voltage system includes:

[0031] The rectifier 110 includes an output end and an input end, the output end includes an output positive electrode and an output negative electrode, and the rectifier 110 is used to convert the alternating current transmitted to the high-voltage system into direct current, wherein the output positive electrode of the rectifier is configured with a first positive electrode relay K1, and the output negative electrode of the rectifier is configured with a first negative electrode relay K3;

[0032] A high-voltage distribution box 120 is connected to the output end of the rectifier 110, and the high-voltage distribution box 120 is used to distribute the direct current transmitted by the rectifier 110 to the working parts of the electric tractor;

[0033] A step-down transformer 140, the output end of which is connected to the input end of the rectifier 110, for stepping down the AC power transmitted to the high voltage system;

[0034] The vehicle controller (not shown in the figure) is connected to the first positive relay K1 and the first negative relay K3 respectively. The vehicle controller is used to control the first positive relay K1 and the first negative relay K3 to be disconnected at the same time when the high-voltage system is powered off, so that the voltage difference between the output end of the rectifier and the electric tractor is lower than the first preset threshold.

[0035] Specifically, the operating parts of the electric tractor include but are not limited to a travel motor, a travel motor controller, an operating motor, an operating motor controller, a brake unit, a brake resistor, an oil pump motor, an oil pump motor controller, a brake motor, a steering motor, a low-voltage battery, etc. The rectifier 110 can use diode rectification to convert the AC power delivered to the high-voltage system into DC power. The output positive pole of the rectifier 110 is configured with a first positive relay K1, and the output negative pole is configured with a first negative relay K3. The output positive pole and the output negative pole of the rectifier 110 are both configured with relays. When the high voltage of the whole vehicle is turned off, the positive and negative relays are controlled to be disconnected at the same time to ensure that the high-voltage circuit is completely cut off and improve safety performance. The step-down transformer 140, the output end of the step-down transformer 140 is connected to the input end of the rectifier 110, and the AC power delivered to the high-voltage system is stepped down. After the stepped-down AC power is converted into DC power by the rectifier 110, it is distributed to various operating parts of the electric tractor through the high-voltage distribution box 120 for use. It is understandable that only configuring the relay at the output positive pole cannot completely disconnect the circuit. If only the relay at the output positive pole is disconnected after power is turned off, there is still a voltage difference between the output negative pole of the rectifier 110 and the frame of the electric tractor. The output positive pole of the rear-end line of the high-voltage system is connected to the output negative pole through the discharge resistor, and there is also a voltage difference. If the rear-end high voltage is touched at this time, an electric shock accident will occur. Therefore, the vehicle controller can control the first positive pole relay K1 and the first negative pole relay K3 to be disconnected at the same time when the high-voltage system is under high voltage power-off, so that the voltage difference between the output end of the rectifier 110 and the electric tractor is lower than the first preset threshold value, and the first preset threshold value refers to the voltage difference caused by random errors. The first preset threshold value is set to be compatible with the errors generated randomly. If it exceeds the first preset threshold value, there will be a risk of electric shock, and being lower than the first preset threshold value already meets the actual requirements of safe operation. Specifically, the first preset threshold value can be set to be lower than the safe voltage 24V for continuous contact with the human body, and exceeding this value will cause the risk of electric shock. In this way, the safety of high-voltage power supply of the electric tractor can be improved. Among them, the vehicle controller can specifically be a vehicle VCU unit.

[0036] refer to Figure 1 In an embodiment of the present invention, the input end of the rectifier 110 also includes a filter capacitor C0 and a discharge resistor R0 arranged in parallel. The filter capacitor C0 is used to filter the AC component in the rectifier circuit of the rectifier, and the discharge resistor R0 is used to dissipate the energy stored in the filter capacitor.

[0037] It can be understood that the filter capacitor C0 refers to an energy storage device installed at both ends of the rectifier circuit to reduce the AC ripple coefficient and improve the efficient and smooth DC output. Setting the filter capacitor C0 will make the working performance of the electronic circuit more stable, and also reduce the interference of the alternating pulsating ripple on the electronic circuit. The filter capacitor is used in the rectifier circuit to filter out the AC component and make the output DC smoother. The discharge resistor R0 is connected in parallel with the filter capacitor C0. The filter capacitor C0 filters the AC component in the rectifier circuit of the rectifier 110 by charging and discharging. The discharge resistor R0 can quickly reduce the residual charge of the capacitor and dissipate the energy stored in the filter capacitor.

[0038] refer to Figure 1 In an embodiment of the present invention, the high voltage system further includes a step-down transformer 140, the output end of the step-down transformer 140 is connected to the input end of the rectifier 110, and is used to step down the alternating current transmitted to the high voltage system. The connection mode of the winding of the step-down transformer 140 is DY11.

[0039] The step-down transformer 140 is fixedly installed in the vehicle, and the winding adopts the DY11 connection method. The step-down transformer 140 can step down the AC power transmitted to the high-voltage system to about 400V AC power, transmit it to the rectifier 110, convert the AC power into DC power, and distribute it to various operating components through the high-voltage distribution box 120.

[0040] Specifically, the AC component in the rectifier circuit of the rectifier 110 can be filtered through the filter capacitor C0 at the input end of the rectifier 110, and the energy stored in the filter capacitor is dissipated through the discharge resistor R0 connected in parallel with the filter capacitor C0, thereby converting the AC power into DC power suitable for the electric tractor, and distributing it to various working parts through the high-voltage distribution box 120. The combination of the filter capacitor C0 and the discharge resistor R0 can be set in multiple groups for parallel connection, so as to achieve the effect of maximally eliminating the AC component in the AC power.

[0041] refer to Figure 1 In an embodiment of the present invention, the step-down transformer 140 includes an incoming line terminal and an outgoing line terminal. The connection mode of the incoming line terminal is a triangle connection, and the connection mode of the outgoing line terminal is a star connection without a neutral line. The outgoing line terminal is configured with a first circuit breaker QF3. The first circuit breaker QF3 is used to cut off the line of the high-voltage system when an overcurrent or short circuit occurs in the high-voltage system.

[0042] The step-down transformer 140 is fixedly installed in the vehicle, and can reduce the voltage of the transmitted high voltage electricity to meet the voltage provided by the electric tractor for driving operation. The winding adopts the DY11 connection method, the incoming line adopts a triangle connection, and the outgoing line adopts a star connection without a neutral line. The outgoing line is equipped with a first circuit breaker QF3, which is used to cut off the line of the high voltage system in the event of overcurrent or short circuit in the high voltage system, thereby protecting the line and electrical appliances at the back end of the step-down.

[0043] refer to Figure 1 In an embodiment of the present invention, the power supply system further includes a power grid distribution cabinet 150, a step-up transformer 160, and a high-voltage switch cabinet 170 which are connected in sequence according to the power supply direction. The output end of the high-voltage switch cabinet 170 is connected to the input end of the step-down transformer 140. The step-up transformer 160 is fixedly installed on the ground. The connection mode of the winding of the step-up transformer 160 is YNd11. The connection mode between the primary side of the step-up transformer 160 and the power grid distribution cabinet is a star connection. The connection mode between the secondary side of the step-up transformer 160 and the high-voltage switch cabinet 170 is a triangle connection. The power grid distribution cabinet is equipped with a second circuit breaker QF1, which is used to disconnect the circuit when leakage is detected.

[0044] Specifically, an electric tractor can be a high-horsepower tractor for field operation, and the whole machine can be powered by a pure power battery or a hybrid power mode of a power battery and an engine. Tractors need to work in the field for a long time, and the pure power battery power supply solution is only suitable for low-horsepower tractors, but not for high-horsepower tractors. For example, a 150KW (200hp) tractor needs to be equipped with a battery pack of more than 600KW / h to work at rated power for 4 hours, which is difficult to achieve in terms of cost or assembly space. The energy supply time of the pure power battery in the high-horsepower range of hybrid mode tractors is limited, and the whole machine still relies mainly on the engine for power. When the engine burns fuel to drive, it will still emit more exhaust gas, which does not conform to the green and clean development concept of electric tractors.

[0045] In order to provide stable working power for the long-range electric tractor, and not to use fuel or power batteries as the power source, the AC power of the low-voltage power grid can be obtained from the mains power grid provided by the power distribution cabinet 150, and the AC power of the low-voltage power grid is boosted by the step-up transformer 160 by means of power boost transmission and in-vehicle voltage reduction, and transmitted to the high-voltage switch cabinet 170. Among them, the voltage of the power distribution cabinet 150 can be 380V. The power distribution cabinet 150 can provide three-phase low-voltage power grid current. The high-voltage switch cabinet 170 is fixedly installed close to the step-up transformer 160, and can cut off the circuit in time when short circuit, open circuit, overcurrent and other faults occur in the rear-end circuit, protect the rear-end electrical appliances and lines, and avoid personal injury caused by cable breakage or short circuit. Furthermore, the AC power is transmitted to the step-down transformer 140, which steps down the high voltage power to about 400V AC power, and transmits it to the rectifier 110, which converts the AC power into DC power suitable for the tractor, and distributes it to each operating component through the high-voltage distribution box 120. The above scheme uses grid power as the energy source of the whole vehicle, which can not only ensure the long-term stable operation of the high-horsepower electric tractor, but also achieve lower pollution emissions. The scheme of boosting transmission and stepping down is adopted to reduce the power loss in the process of high-power and long-distance power transmission.

[0046] refer to Figure 1 The high-voltage switch cabinet 170 is fixedly installed near the step-up transformer 160, and includes the third circuit breaker QF2, the upper isolating knife switch QS1, the microcomputer protection device, the voltage transformer, the current transformer, the zero-sequence current transformer and other devices, which can cut off the circuit in time when the back-end circuit has a short circuit, a circuit break, an overcurrent and other faults, protect the back-end electrical appliances and lines, and avoid personal injury caused by cable breakage or short circuit. The third circuit breaker can be, but is not limited to, a vacuum circuit breaker.

[0047] refer to Figure 1 In an embodiment of the present invention, the high-voltage system includes a reel device 180, the high-voltage switch cabinet 170 is connected to the step-down transformer through a transmission cable 190, and the reel device 180 is used to retract and release the transmission cable; a reel controller 181 is connected to the reel device 180, and the reel controller 181 is connected to the third switch F3 of the high-voltage distribution box, and the third switch F3 is connected in series with the third positive relay K4 of the high-voltage distribution box.

[0048] Specifically, after the electric energy is output from the high-voltage switch cabinet 170, it is transmitted to the step-down transformer 140 through the transmission cable 190 and the reel device 180. The transmission cable 190 can be a three-phase four-core wire, including a grounding cable, which is used to connect the grounding at the step-up transformer 160 to the frame of the electric tractor to ensure that the voltage level inside and outside the vehicle is consistent. The transmission cable 190 is divided into an outside part and an inside part through the slip ring of the reel device 180. One end of the transmission cable 190 outside the vehicle is fixed to the high-voltage switch cabinet 170, and the other end is connected to the rotor of the slip ring of the reel device 180. The transmission cable 190 is wound on the reel device 180 inside the vehicle. The reel controller 181 is connected to the reel device 180, and can control the cable collection or release according to the running distance of the electric tractor, so that the transmission cable 190 maintains a suitable tension. Then the transmission cable 190 will not be loosely dragged on the ground due to excessive relaxation, nor will there be a risk of breakage due to excessive tension. The drum controller 181 is connected to the third switch F3 of the high-voltage distribution box, and the third switch F3 is connected in series with the third positive relay K4 of the high-voltage distribution box. The high-voltage distribution box can distribute direct current to the drum controller and the drum device to cooperate with the long-distance work of the electric tractor. One end of the in-vehicle part of the transmission cable 190 is fixed to the stator of the slip ring of the drum device 180, and the other end is connected to the step-down transformer 140. The above scheme adopts the scheme of boost transmission and step-down use, which reduces the power loss in the process of high-power and long-distance power transmission, configures a longer transmission cable, and increases the operating range of the tractor.

[0049] refer to Figure 1 In an embodiment of the present invention, the output positive pole of the rectifier 110 is also configured with a first pre-charging relay K2 connected to the first positive pole relay K1, which is used to control the opening and closing of the pre-charging circuit. Specifically, the first positive pole relay K1 is connected in parallel with the first pre-charging relay K2, and the first pre-charging relay K2 is connected in series with the first pre-charging resistor R1, which can limit the magnitude of the current and avoid large current shocks, thereby protecting the power switch from damage. The filter capacitor C0 at the input end of the rectifier 110 filters the AC component in the rectifier circuit of the rectifier 110, and dissipates the energy stored in the filter capacitor through the discharge resistor R0 connected in parallel with the filter capacitor C0, and the combination of the filter capacitor C0 and the discharge resistor R0 can be set in multiple groups for parallel connection, so as to achieve the effect of maximally eliminating the AC component in the AC power. One end of the combination of the filter capacitor C0 and the discharge resistor R0 is connected to the output positive pole, and the other end is connected to the output negative pole.

[0050] refer to Figure 1In an embodiment of the present invention, the high-voltage distribution box 120 also includes a first positive branch, a second positive branch and a negative main circuit. The first positive branch is configured with a third positive relay K4, the second positive branch is configured with a fourth positive relay K5, the second positive branch is configured with a second pre-charging relay K6, and the negative main circuit is configured with a second negative relay K7.

[0051] refer to Figure 1 In an embodiment of the present invention, the high-voltage distribution box 120 also includes a positive main circuit, which is equipped with a first switch F1 for disconnecting the circuit when the switch is open, connecting the circuit when the switch is closed, and fusing the circuit when the circuit is short-circuited.

[0052] The rectified DC power of the rectifier 110 is transmitted to the high-voltage distribution box 120, and distributed to each motor controller and motor through the high-voltage distribution box 120 to provide power for the whole machine. The high-voltage distribution box 120 includes a third positive relay K4 and a fourth positive relay K5, a second pre-charge relay K6 and a second negative relay K7, which are used to control the DC high-voltage circuit. The first switch F1 is also configured in the positive main circuit to disconnect the circuit to ensure safety during debugging and maintenance, and can effectively fuse when the back-end circuit is short-circuited to protect the line and electrical appliances.

[0053] refer to Figure 1 In an embodiment of the present invention, the high-voltage system further includes a brake unit 210 and a brake resistor 220 connected to the high-voltage distribution box 120, and the vehicle controller (not shown in the figure) is further configured to: monitor the voltage at the DC end of the high-voltage system, and when the voltage at the DC end of the brake unit 210 is greater than the second preset threshold, connect the loop between the brake resistor 220 and the brake unit 210 to convert electrical energy into heat energy through the brake resistor. The second preset threshold is the voltage threshold of the DC end of the high-voltage distribution box set by the technician. Setting the second preset threshold as the basis for the brake unit to connect the loop between the brake resistor 220 and the brake unit 210 can improve the stability of the DC power. Specifically, because the overvoltage protection point of the motor controller is 750V, in order to prevent the motor controller from shutting down for protection or causing damage due to overvoltage, and to ensure that the DC voltage does not exceed the protection point within the reaction time of the brake unit, after simulation, the second preset threshold can be set to 680V.

[0054] Since there is no power battery in the power supply system, the motor deceleration or braking will generate regenerative electric energy, which is fed back to the DC bus and cannot be consumed quickly, causing the DC high voltage of the whole machine to increase abnormally, causing the motor controller to shut down or even be damaged. Therefore, a brake unit 210 and a brake resistor 220 are configured between the main circuits of the high-voltage distribution box 120. The vehicle controller monitors the voltage at the DC end of the high-voltage system. When the voltage is greater than the second preset threshold, the brake unit 210 connects the circuit between the brake resistor 220, and the brake resistor 220 converts the regenerative electric energy into heat energy for consumption, keeping the DC voltage stable.

[0055] In an embodiment of the present invention, the first branch of the first positive branch is connected to the auxiliary source three-in-one controller, and a second switch F2 is provided on the branch. The three-in-one controller 230 is respectively connected to the brake motor 10, the steering motor 20, and the low-voltage battery 30. Among them, the three-in-one controller 230 includes a DCAC1 set for the brake motor 10, a DCAC2 set for the steering motor 20, and a DCDC1 set for the low-voltage battery 30. The wire connected to the brake motor 10 is a 3×2.5mm2 multi-core shielded cable, and the wire connected to the steering motor 20 is a 3×2.5mm 2 Multi-core shielded cable, the wire connecting the low-voltage battery 30 is 24V+35mm 2 Unshielded cable and 24V- 35mm 2 Unshielded cable. The second branch of the first positive branch is connected to the reel controller 181, and a third switch F3 is provided on the branch. DCAC3 is provided between the second branch and the reel controller 181. The second positive branch corresponds to three branches, the first branch is provided with a fourth switch F4, the first branch is connected to the oil pump motor controller 40, and the oil pump motor controller 40 controls the operation of the oil pump motor 41; the second branch is provided with a fifth switch F5, and the second branch is connected to the walking motor controller 50, and the walking motor controller 50 controls the operation of the walking motor 51; the third branch is provided with a sixth switch F6, and the third branch is connected to the working motor controller 60, and the working motor controller 60 controls the operation of the working motor 61. After the second pre-charge relay K6 is connected in series with the second pre-charge resistor R2, the two are connected in parallel with the fourth positive relay K5 of the second positive branch. The above switches are respectively used to control the on and off of the corresponding controllers or components. The high-voltage distribution box 120 also includes a third positive branch, and the third positive branch is connected to a brake unit 210 and a brake resistor 220. The braking unit 210 may not be based on the judgment of the vehicle controller. When the motor decelerates or brakes to generate reverse electromotive force, the braking unit can be started in time to connect the braking resistor, convert the regenerated electrical energy into heat energy consumption, and maintain the DC voltage stable.

[0056] Figure 2The electrical connection diagram of a power supply system for an electric tractor according to an embodiment of the present invention is schematically shown. Figure 1 and Figure 2 The power supply system is connected in sequence according to the power supply direction with the power distribution cabinet 150, the step-up transformer 160, the high-voltage switch cabinet 170, the transmission cable 190, the step-down transformer 140, the rectifier 110, the high-voltage distribution box 120, the vehicle VCU 130 and the operating parts. Among them, the transmission cable 190 is divided into an external part and an internal part through the slip ring of the reel device 180. One end of the transmission cable 190 outside the vehicle is fixed to the high-voltage switch cabinet 170, and the other end is connected to the rotor of the slip ring. The transmission cable 190 is wound on the reel device 180 inside the vehicle, and the reel is driven to rotate by the winding motor 70 of the reel device, and the cable is collected or released according to the running distance of the electric tractor. One end of the internal part of the transmission cable 190 is fixed to the stator of the slip ring, and the other end is connected to the step-down transformer 140. The working parts of the electric tractor include a travel motor 51, a travel motor controller 50, a working motor 61, a working motor controller 60, a brake unit 210, a brake resistor 220, an oil pump motor 41, and an oil pump motor controller 40, and the above working parts are all connected to the high-voltage distribution box 120. The working parts also include a brake motor 10, a steering motor 20, a low-voltage battery 30, etc. connected to the three-in-one controller 230. The vehicle VCU 130 is respectively connected to the rectifier 110, the high-voltage distribution box 120, the oil pump motor controller 40, the travel motor controller 50, the working motor controller 60, and the three-in-one controller 230. The three-in-one controller 230 is connected to the high-voltage distribution box 120. The power of the brake motor 10 can be 1.5kw, and the power of the steering motor 20 can be 3KW.

[0057] The step-up transformer 160 and the high-voltage switch cabinet 170 are fixedly installed outside the vehicle near the power distribution cabinet 150, and the reel device 180, the step-down transformer 140, the rectifier 110, the high-voltage distribution box 120, and the vehicle VCU 130 are all installed inside the vehicle. The step-up transformer 160 is connected to the power grid, and the low-voltage power of the power grid is stepped up, and transmitted to the step-down transformer 140 through the reel device 180 and the transmission cable 190. The step-down transformer 140 steps down the high-voltage AC power transmitted to an AC power supply of about 400V, and transmits it to the rectifier 110. The rectifier 110 converts the AC power into DC power suitable for the tractor, and distributes it to each motor controller and motor through the high-voltage distribution box 120.

[0058] The above technical solution adopts the power supply mode of grid electricity, and uses grid electricity as the energy source of the whole vehicle, which can not only ensure the long-term stable operation of the high-horsepower tractor, but also achieve zero emission of the whole vehicle. The scheme of boost transmission and step-down is adopted to reduce the power loss in the process of high-power and long-distance power transmission, and can be configured with longer transmission cables, which increases the operating range of the tractor. The high-voltage switch cabinet, step-down transformer and high-voltage distribution box are equipped with circuit breaker protection devices for the rear-end circuit, which can cut off the circuit in time when short circuit, open circuit, overcurrent and other faults occur in the rear-end sections of the line, protect the rear-end electrical appliances and cables, and avoid electric shock injuries caused by ground short circuit. The positive and negative poles of the rectifier output are equipped with relays. When the high voltage of the whole vehicle is powered on, the positive and negative relays are controlled to be disconnected at the same time to ensure that the high-voltage circuit is completely cut off. A brake unit and a brake resistor are configured behind the high-voltage distribution box, which can be started in time when the motor decelerates or brakes to generate reverse electromotive force, converting the regenerated electric energy into heat energy consumption and maintaining the stability of the DC voltage.

[0059] Figure 3 The electrical principle diagram of a power supply system for an electric tractor according to another embodiment of the present invention is schematically shown. Figure 1 and Figure 3 The power supply system is connected in sequence according to the power supply direction to the power distribution cabinet 150, the first step-down transformer 1, the high-voltage switch cabinet 170, the transmission cable 190, the second step-down transformer 2, the rectifier 110, the high-voltage distribution box 120 and the operating parts. Among them, the transmission cable 190 is divided into an external part and an internal part through the slip ring of the reel device 180. One end of the external transmission cable 190 is fixed to the high-voltage switch cabinet 170, and the other end is connected to the rotor of the slip ring. The transmission cable 190 is wound on the internal reel device 180, and the cable can be collected or released according to the running distance of the electric tractor. One end of the internal part of the transmission cable 190 is fixed to the stator of the slip ring, and the other end is connected to the second step-down transformer 2. The working parts of the electric tractor include a travel motor 51, a travel motor controller 50, a working motor 61, a working motor controller 60, a brake unit 210, a brake resistor 220, an oil pump motor 41, and an oil pump motor controller 40. The above working parts are all connected to the high-voltage distribution box 120. The working parts also include a brake motor 10, a steering motor 20, a low-voltage battery 30, etc. connected to the three-in-one controller 230. The vehicle VCU 130 is respectively connected to the rectifier 110, the high-voltage distribution box 120, the oil pump motor controller 40, the travel motor controller 50, the working motor controller 60, and the three-in-one controller 230. The three-in-one controller 230 is connected to the high-voltage distribution box 120.

[0060] The first step-down transformer 1 and the high-voltage switch cabinet 170 are fixedly installed outside the vehicle near the power distribution cabinet 150, and the reel device 180, the second step-down transformer 2, the rectifier 110, the high-voltage distribution box 120, the vehicle VCU 130, etc. are all installed inside the vehicle. The first step-down transformer 1 is connected to the power grid, and the medium-voltage electricity in the power grid is stepped down, and transmitted to the second step-down transformer 2 through the reel device 180 and the transmission cable 190. The second step-down transformer 2 steps down the high-voltage AC power transmitted to an AC power supply of about 400V, and transmits it to the rectifier 110. The rectifier 110 converts the AC power into DC power suitable for the tractor, and distributes it to each motor controller and motor through the high-voltage distribution box 120.

[0061] The power is taken from the medium voltage 6 / 10kV grid, and the voltage is adjusted to the required transmission voltage by the first step-down transformer 1, and then connected to the high-voltage switch cabinet 170 and transmitted to the vehicle by the transmission cable 190, and then stepped down for use by the second step-down transformer 2. Furthermore, if the power of the whole machine is large enough, the primary step-down process can be omitted, and the electric energy of the medium voltage grid is directly transmitted to the vehicle by the transmission cable 190 after passing through the high-voltage switch cabinet 170, and stepped down by the second step-down transformer 2 in the vehicle, and then rectified into DC power suitable for the whole vehicle to supply energy to the whole machine. Of course, as the transmission voltage increases, the corresponding risk factor will also increase, so we should choose a transmission voltage that is suitable for the whole vehicle, and cannot blindly choose 6 / 10kV grid direct power supply to reduce the step-down link.

[0062] An embodiment of the present invention provides a controller, which may include:

[0063] a memory configured to store instructions;

[0064] The processor is configured to call instructions from the memory and implement the above method for controlling the power supply system when executing the instructions.

[0065] Specifically, in the embodiment of the present invention, the processor may be configured to:

[0066] When the high voltage system is in high voltage power-down state, the first positive relay and the first negative relay are controlled to be disconnected simultaneously so that the voltage difference between the output negative pole of the rectifier and the electric tractor is lower than a first preset threshold value.

[0067] In an embodiment of the present invention, the processor may also be configured to:

[0068] The voltage at the DC end of the high-voltage system is monitored so that the brake unit connects the loop between the brake resistor and the brake unit when the voltage at the DC end is greater than a second preset threshold value, so as to convert electrical energy into heat energy through the brake resistor.

[0069] An embodiment of the present invention further provides an electric tractor, which may include the above-mentioned power supply system for an electric tractor, which can not only ensure the long-term stable operation of the electric tractor, but also achieve zero emissions of the entire vehicle.

[0070] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0071] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A power supply system for an electric tractor, characterized in that: The power supply system includes a high-voltage system, which is installed on the electric tractor. The electric tractor includes a high-horsepower tractor operating in the field. The high-voltage system includes: A rectifier, the rectifier comprising an output end and an input end, the output end comprising an output positive electrode and an output negative electrode, the rectifier being used to convert the alternating current transmitted to the high voltage system into direct current, wherein the output positive electrode of the rectifier is configured with a first positive electrode relay, the output negative electrode of the rectifier is configured with a first negative electrode relay, the input end of the rectifier further comprising a filter capacitor and a discharge resistor arranged in parallel, the filter capacitor being used to filter the alternating current component in the rectifier circuit of the rectifier, and the discharge resistor being used to dissipate the energy stored in the filter capacitor; A high-voltage distribution box connected to the output end of the rectifier, the high-voltage distribution box is used to distribute the direct current delivered by the rectifier to the operating parts of the electric tractor; A step-down transformer, the output end of which is connected to the input end of the rectifier, for stepping down the alternating current delivered to the high voltage system; a vehicle controller, connected to the first positive relay and the first negative relay, respectively, and configured to control the first positive relay and the first negative relay to be disconnected simultaneously when the high-voltage system is in a high-voltage power-off state, so that the voltage difference between the output end of the rectifier and the electric tractor is lower than a first preset threshold value; The power supply system also includes a power grid distribution cabinet, a step-up transformer, and a high-voltage switch cabinet which are connected in sequence according to the power supply direction. The output end of the high-voltage switch cabinet is connected to the input end of the step-down transformer. The step-up transformer is fixedly installed on the ground. The connection mode of the winding of the step-up transformer is YNd11. The connection mode between the primary side of the step-up transformer and the power grid distribution cabinet is a star connection. The connection mode between the secondary side of the step-up transformer and the high-voltage switch cabinet is a triangle connection. The power grid distribution cabinet is equipped with a second circuit breaker, which is used to disconnect the circuit when leakage is detected.

2. The power supply system for an electric tractor according to claim 1, characterized in that: The connection mode of the windings of the step-down transformer is DY11.

3. The power supply system for an electric tractor according to claim 1, characterized in that: The step-down transformer includes an incoming line terminal and an outgoing line terminal. The incoming line terminal is connected in a triangle manner, and the outgoing line terminal is connected in a star manner without a neutral line. The outgoing line terminal is configured with a first circuit breaker. The first circuit breaker is used to cut off the line of the high-voltage system when an overcurrent or short circuit occurs in the high-voltage system.

4. The power supply system for an electric tractor according to claim 1, characterized in that: The high-voltage system further comprises: A reel device, wherein the high-voltage switch cabinet is connected to the step-down transformer via a transmission cable, and the reel device is used to retract and release the transmission cable; A reel controller is connected to the reel device, the reel controller is connected to the third switch of the high-voltage distribution box, and the third switch is connected in series with the third positive relay of the high-voltage distribution box.

5. The power supply system for an electric tractor according to claim 1, characterized in that: The output positive electrode of the rectifier is also configured with a first pre-charging relay connected in parallel with the first positive relay, and a first pre-charging resistor connected in series with the first pre-charging relay.

6. The power supply system for an electric tractor according to claim 1, characterized in that: The high-voltage distribution box also includes a first positive branch, a second positive branch, a negative main circuit and a positive main circuit. The first positive branch is configured with a third positive relay, the second positive branch is configured with a fourth positive relay and a second pre-charge relay, and the negative main circuit is configured with a second negative relay; the positive main circuit is configured with a first switch, which is used to disconnect the circuit when the switch is open, connect the circuit when the switch is closed, and fuse the circuit when the circuit is short-circuited.

7. The power supply system for an electric tractor according to claim 1, characterized in that: The high-voltage system further includes a brake unit and a brake resistor connected to the high-voltage distribution box, and the vehicle controller is further configured as follows: The voltage at the DC end of the high-voltage system is monitored so that the brake unit connects the loop between the brake resistor and the brake unit when the voltage at the DC end is greater than a second preset threshold value, so as to convert electrical energy into heat energy through the brake resistor.

8. An electric tractor, characterized in that: A power supply system for an electric tractor as claimed in any one of claims 1 to 7 is provided.

Images