Electric wheel self-unloading truck braking resistor and control method

Abstract

This invention relates to the field of mining truck equipment and discloses a braking resistor and control method for an electric wheel dump truck. The braking resistor includes a chopper module; a first end of the chopper module is connected to a resistor strip, and a second end of the chopper module is connected to the positive terminal of the first DC bus of the electric wheel dump truck. The resistor strip is connected to the negative terminal of the first DC bus. The chopper module is turned on when braking energy is fed back to the first DC bus, causing the DC bus voltage to rise to a first target value, thus loading the DC bus voltage onto the resistor strip to absorb braking energy. The chopper module is turned off when the DC bus voltage drops to a second target value during the process of the resistor strip absorbing braking energy. The braking resistor disclosed in this application solves the problem of improving the braking capacity of the braking resistor, making its application not limited by whether the converter of the electric wheel dump truck has control functions.

Description

Technical Field

[0001] This invention relates to the field of mining truck equipment technology, and in particular to a braking resistor and control method for an electric wheel dump truck. Background Technology

[0002] Off-highway electric wheel dump trucks are one of the main transportation equipment in open-pit mines. Their braking methods include mechanical braking and electric braking. Currently, the electric braking function is achieved by installing a braking resistor connected to a converter. When the feedback braking energy causes the DC bus voltage of the converter to rise to a certain threshold, the energy is released as heat through the braking resistor. Simultaneously, during the continuous heating of the resistor, a cooling system is needed to dissipate the heat into the air as quickly as possible, maintaining the resistor's continuous braking performance. However, the operation of existing braking resistors is controlled by the converter and lacks its own control function. For situations with large braking energy, the energy recovery of off-highway electric wheel dump trucks is limited (especially for pure electric off-highway electric wheel dump trucks). Relying solely on hydraulic brake friction pads results in significant wear and insufficient reliability. Summary of the Invention

[0003] The purpose of this invention is to provide at least one braking resistor and control method for electric wheel dump trucks, which can at least solve the problem of improving the braking capacity of the braking resistor, and at least achieve the effect that the application is not limited by whether the converter of the electric wheel dump truck has a control function, effectively improving the braking capacity and reliability of the braking resistor, and the application is not limited by whether the converter of the electric wheel dump truck has a control function.

[0004] To address the aforementioned technical problems, at least one embodiment of this application provides a braking resistor for an electric wheel dump truck, comprising a resistor strip and a cooling fan for dissipating heat from the resistor strip, and further comprising a chopper module; a first end of the chopper module is connected to the resistor strip, a second end of the chopper module is connected to the positive terminal of a first DC bus of the electric wheel dump truck, the resistor strip is connected to the negative terminal of the first DC bus, the chopper module is turned on when braking energy is fed back to the first DC bus, causing the DC bus voltage to rise to a first target value, thereby loading the DC bus voltage onto the resistor strip to absorb braking energy, and the chopper module is turned off when the DC bus voltage drops to a second target value during the process of the resistor strip absorbing braking energy.

[0005] At least one embodiment of this application also provides a voltage control method for the braking resistor of an electric wheel dump truck, comprising:

[0006] Obtain the DC bus voltage on the first DC bus connected to the resistor band;

[0007] Calculate the difference Ue between the first target value and the DC bus voltage;

[0008] Based on the difference Ue and the first preset threshold Uh1 and the second preset threshold Uh2, the following voltage control is performed:

[0009] When Ue=0, the chopper module is turned on, the resistor band starts working, and the cooling fan starts dissipating heat.

[0010] During the operation of the resistance band, if Ue > 0 and |Ue| < Uh2, the chopper module is in the on state; if Ue > 0 and |Ue| ≥ Uh2, the chopper module is in the off state, and when |Ue| = Uh2, the DC bus voltage drops to the second target value; if Ue < 0 and 0 < |Ue| < Uh1, the chopper module is in the on state and generates overcurrent or overvoltage alarm information; if Ue < 0 and Uh1 < |Ue|, the chopper module is off and generates shutdown alarm information.

[0011] At least one embodiment of this application also provides a current control method for the braking resistor of an electric wheel dump truck, comprising:

[0012] With the chopper module in the ON state, the DC bus voltage and the operating current of the resistor strip on the first DC bus connected to the resistor strip are obtained.

[0013] Based on the DC bus voltage and the resistance design value of the resistance band, calculate the current value;

[0014] Based on the error between the calculated current value and the operating current, it is determined whether the resistor band has a fault: if the error is the set value, the resistor band has no fault; if the error is greater than the set value, the resistor band has a short circuit fault; if the error is less than the set value, the resistor band has an open circuit fault.

[0015] At least one embodiment of this application also provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform any one of the voltage control method, current control method, or cooling fan control method described above.

[0016] At least one embodiment of this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements any one of the voltage control method, current control method, or cooling fan control method described above.

[0017] The electric wheel dump truck braking resistor provided in the embodiments of this application performs electric braking by turning on and off the chopper module, and the braking resistor is directly connected to the DC bus, so that the braking resistor has a control function. Its application is not limited by whether the converter of the electric wheel dump truck has a control function, effectively improving the braking capacity and reliability of the braking resistor.

[0018] The voltage control method for the braking resistor of the electric wheel dump truck provided in the embodiments of this application controls the voltage by using the difference between the first target value and the DC bus voltage, and the difference range determined by the first preset threshold and the second preset threshold. Different alarm information is generated under different conditions that exceed the difference range, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system fails.

[0019] The current control method for the braking resistor of the electric wheel dump truck provided in the embodiments of this application, during the process of dynamically adjusting the working current of the resistor band to reach the target current value, diagnoses whether the resistor band has a short circuit or open circuit fault based on the error between the calculated current value of the resistor band and the working current of the resistor band, and generates corresponding alarm information, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system malfunctions.

[0020] In some optional embodiments, the chopper module includes:

[0021] IGBT switching transistor;

[0022] A pulse board is connected to the IGBT switching transistor;

[0023] A control board, connected to the pulse board, is used to generate a first control signal when the braking energy is fed back to the first DC bus and the DC bus voltage rises to a first target value, and to generate a second control signal when the DC bus voltage drops to a second target value during the process of the resistor absorbing braking energy. The first control signal and the second control signal are transmitted to the IGBT switch through the pulse board to control the IGBT switch to turn on and off respectively.

[0024] The chopper module provided in the embodiments of this application controls the chopper to be turned on and off through a first target value and a second target value. When the braking energy is fed back to the DC bus, causing the DC bus voltage to rise to the first target value, the chopper circuit is turned on. At this time, the DC bus voltage is directly applied to the resistor band to absorb the braking energy. As the braking energy is absorbed, the DC bus voltage will drop to the second target value, thereby cutting off the chopper circuit. The control signal of the control board is transmitted to the IGBT switching transistor through the pulse board to realize the above voltage control method, which can improve the braking capacity and reliability of the braking resistor and avoid the problem of insufficient reliability due to large wear of hydraulic brake friction pads.

[0025] In some optional embodiments, the chopper module includes:

[0026] IGBT switching transistor;

[0027] A pulse board is connected to the IGBT switching transistor;

[0028] A control board, connected to the pulse board, is used to generate a third control signal to control the duty cycle of the IGBT switch during the process of the resistor band absorbing braking energy. The third control signal is transmitted to the IGBT switch through the pulse board to dynamically adjust the operating current of the resistor band so that the operating current reaches the target current value.

[0029] The chopper module provided in the embodiments of this application dynamically adjusts the working current of the resistor band to achieve the target current value. The control signal of the control board is transmitted to the IGBT switching transistor via the pulse board to realize the above-mentioned current control method. This can improve the braking capability and reliability of the braking resistor, avoid the problem of insufficient reliability due to large wear of hydraulic brake friction pads, and achieve precise current control during the process of the resistor band absorbing braking energy.

[0030] In some alternative embodiments, the cooling fan includes a DC fan or an AC fan;

[0031] In the case where the cooling fan includes a DC fan, the power supply line of the DC fan is connected in parallel to the resistor strip;

[0032] When the cooling fan includes an AC fan, the power line of the AC fan is connected to an inverter, and the inverter is connected to the first DC bus or the second DC bus of the electric wheel dump truck; when the braking energy is fed back to the first DC bus and the DC bus voltage rises to the first target value, the operating frequency of the AC fan is increased to the rated point; when the DC bus voltage drops to the second target value, the operating frequency of the AC fan drops to idle speed.

[0033] Since the power supply line of the AC fan is connected to the DC bus via the inverter, the inverter is powered by converting DC power to AC power by taking the DC bus voltage. This independent power supply method does not depend on the conduction of the resistor band. When the DC bus voltage drops to the second target value and the chopper circuit is cut off, the operating frequency of the AC fan can be reduced to idle speed and continue to operate, thus improving the heat dissipation effect.

[0034] In some optional embodiments, a step-down circuit is also provided on the first DC bus or the second DC bus connected to the inverter.

[0035] By setting up a step-down circuit, the DC bus voltage, which does not meet the rated operating voltage of the AC fan, can be processed into a voltage that can supply power to the AC fan.

[0036] In some optional embodiments, the electric wheel dump truck braking resistor further includes at least one of a voltage sensor and a current sensor;

[0037] A voltage sensor is disposed between the positive and negative terminals of the first DC bus to detect the DC bus voltage.

[0038] A current sensor is positioned between the second terminal of the chopper module and the positive terminal of the first DC bus to detect the operating current of the resistor band.

[0039] By setting up voltage and current sensors, it is possible to monitor the DC bus voltage and the operating current of the resistor, so as to effectively control the voltage and current. Attached Figure Description

[0040] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.

[0041] Figure 1 This is a schematic diagram of the energy transfer path in existing mining electric wheel dump truck technology;

[0042] Figure 2 This is a schematic diagram illustrating the working principle of the cooling fan in a mining electric wheel dump truck in the prior art;

[0043] Figure 3 This is a schematic diagram of the braking resistor for an electric wheel dump truck provided in one embodiment of this application;

[0044] Figure 4 This is a schematic diagram of the braking resistor of an electric wheel dump truck using an AC fan, provided in an embodiment of this application;

[0045] Figure 5 This is a flowchart of a voltage control method for the braking resistor of an electric wheel dump truck provided in an embodiment of this application;

[0046] Figure 6 This is a schematic diagram of the voltage control principle provided in an embodiment of this application;

[0047] Figure 7 This is a flowchart of a current control method for the braking resistor of an electric wheel dump truck provided in an embodiment of this application;

[0048] Figure 8 This is a schematic diagram illustrating the principle of the PWM wave control method provided in the embodiments of this application;

[0049] Figure 9 This is a schematic diagram of the current control principle using PWM waves provided in an embodiment of this application;

[0050] Figure 10 This is a schematic diagram of a voltage control device for the braking resistor of an electric wheel dump truck provided in an embodiment of this application;

[0051] Figure 11 This is a schematic diagram of the current control device for the braking resistor of an electric wheel dump truck provided in an embodiment of this application. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of the present invention to enable the reader to better understand the present invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0053] To facilitate understanding of the embodiments of this application, the relevant content regarding the braking resistor of the mining electric wheel dump truck will be introduced first.

[0054] As one of the main transportation tools in open-pit mines, off-highway electric wheel dump trucks have both mechanical and electric braking functions. These trucks are generally large in tonnage, with the smallest having a load capacity of 50 tons and the largest reaching 400 tons. If the vehicle is stopped by mechanical braking, the reliability of the brake pads is required to be very high. Therefore, most vehicles are equipped with electric braking functions for deceleration. Furthermore, mechanical braking is generally not used easily during driving, making electric braking a very important function in the overall vehicle design. In traction mode, the energy primarily comes from the engine or battery at the front end, providing power for driving, climbing, and other operations. In this state, the traction motor functions as an electric motor. However, when the vehicle is descending a slope, speed control and braking are necessary. In this case, the traction motor acts as a generator. Aside from some energy loss due to ground and air resistance, most of the potential and kinetic energy generated during descent is fed back to the DC bus of the converter, boosting its voltage. Failure to dissipate or recover this energy would damage the equipment. Figure 1 The diagram shows the energy transfer path of a mining electric wheel dump truck.

[0055] The electric braking function of mining electric wheel dump trucks is achieved by setting up a braking resistor connected to the converter. When the feedback braking energy raises the DC bus voltage of the converter to a certain threshold, the energy is released as heat through the braking resistor. Simultaneously, during the continuous heating of the resistor, a cooling system is needed to dissipate the heat into the air as quickly as possible, maintaining the resistor's continuous braking performance. As can be seen, the braking resistor mainly consists of a resistor strip, a cooling fan, and a housing. Cooling fans can be divided into DC fans or AC fans, such as... Figure 2 As shown, the DC fan operates by drawing power from a resistor strip connected in parallel to the fan's power cord. The DC fan only starts working when the resistor strip begins absorbing braking energy, thus achieving heat dissipation. The disadvantage of this type of DC motor is the need for regular maintenance of the carbon brushes, but the material cost is lower. The AC fan, on the other hand, draws power from a separate three-phase AC power source. The main difference between this motor and the DC fan is that the fan is powered independently, allowing for independent control. It doesn't need to wait for the resistor strip to turn on; the AC fan can operate continuously, resulting in better heat dissipation than the DC fan.

[0056] In one related technology, a unique method of mounting and fixing the resistor element is adopted, which makes the braking resistor simple in overall structure, easy to disassemble and assemble, reliable in operation, and low in manufacturing cost.

[0057] In another related technology, the service life of the braking resistor device is improved and the maintenance cost of the braking resistor device is reduced by strengthening its structure; the side plate structure of the resistor frame is optimized, reducing the load on the side plate connecting plate and the side plate weld; a spring is set at the bottom of the resistor frame to support the resistor frame and buffer the amplitude of the resistor frame, thereby improving the stability of the resistor frame.

[0058] In another related technology, a brake resistor fan is used to cool the cooling water in the heat exchanger so that the cooling water can be recycled to cool various equipment on the electric mining car, thereby simplifying the cooling system on the electric mining car and reducing costs.

[0059] Another related technology involves a braking resistor device equipped with a fan for heat dissipation of the resistor. Airflow enters the fan through the inlet mesh, flows through the resistor cabinet, and exits through the outlet mesh. The air duct structure is simple, and the airflow distance is short, effectively cooling the resistor. Furthermore, the airflow enters the fan after passing through the inlet mesh before entering the resistor cabinet, preventing dust and other debris in the air from directly entering the resistor cabinet and causing damage, thus improving the service life of the resistor cabinet. The covers are detachable and mounted on the bracket, which protects the fan and resistor cabinet on the bracket and facilitates inspection of the fan, resistor cabinet, and other components due to the detachable covers.

[0060] As can be seen from the above, the current braking resistor does not have a control function, and its operation is limited by the converter.

[0061] The applicant's research found that adding control functionality to the resistor itself can broaden the application range of braking resistors, making them unrestricted by whether the converter has a control resistor configuration. The braking resistor can be directly added to the DC bus to enhance the vehicle's electric braking function. For example, in the use of pure electric mining trucks, braking energy recovery relies on charging the battery. At this time, the braking energy is relatively large, generally twice the battery's discharge energy, thus placing a significant strain on the battery's recharge capability. When the battery's SOC (State of Charge) is high, or when the battery is faulty, the recovered braking energy may be insufficient. Simultaneously, relying solely on mechanical hydraulic braking at this time can lead to overheating and damage to the brakes, posing a significant challenge to vehicle safety. In such cases, adding a braking resistor with control functionality directly to the DC bus can greatly improve the braking performance of the pure electric mining truck, ensuring vehicle operation and resolving the problem of insufficient electric braking capacity.

[0062] To address the aforementioned technical problem of limited application of braking resistors, this invention proposes a braking resistor and control method for electric wheel dump trucks. The implementation details of the electric wheel dump truck braking resistor method in this embodiment are described below. The following implementation details are provided for ease of understanding and are not essential for implementing this solution.

[0063] Example 1:

[0064] One embodiment of this application relates to a braking resistor 10 for an electric wheel dump truck, such as... Figure 3 As shown, it includes a resistor strip 101 and a cooling fan for dissipating heat from the resistor strip 101, and also includes a chopper module 102; the first end of the chopper module 102 is connected to the resistor strip 101, and the second end of the chopper module 102 is connected to the first DC bus of the electric wheel dump truck. Figure 3 The positive terminal of bus 1) is connected to the first DC bus, and the resistor band 101 is connected to the negative terminal of the first DC bus. The chopper module 102 is turned on when the braking energy is fed back to the first DC bus and the DC bus voltage rises to the first target value U0, so that the DC bus voltage is loaded onto the resistor band 101 to absorb the braking energy. The chopper module 102 is turned off when the DC bus voltage drops to the second target value U1 during the process of the resistor band 101 absorbing the braking energy.

[0065] In practical implementation, the aforementioned braking resistor can be installed inside a braking resistor box, forming a braking resistor box with control function for the electric wheel dump truck. There can be multiple resistor strips, and the connection between multiple resistor strips can be in series or parallel. The resistance value of the resistor strips is selected according to the braking power, braking voltage, or current requirements. According to Ohm's law P = U² / R, the maximum braking power of the braking resistor can be calculated. It should be understood that the maximum braking power is not the braking power for prolonged operation.

[0066] The aforementioned braking resistor employs a method of performing electric braking by switching on and off based on a chopper module, and directly connects the braking resistor to the DC bus, thus giving the braking resistor itself a control function. Therefore, its application is not limited by whether the converter of the electric wheel dump truck has a control function. At the same time, it can effectively solve the problem of large braking energy and limited energy recovery (especially for pure electric mining trucks), where relying solely on hydraulic brake friction pads results in large wear and insufficient reliability. This effectively increases the braking capacity of the braking resistor and significantly improves its reliability.

[0067] In some embodiments, the chopper module 102 includes:

[0068] IGBT switching transistor 102a;

[0069] The pulse board 102b is connected to the IGBT switching transistor 102a;

[0070] The control board 103c is connected to the pulse board 102b and is used to generate a first control signal when the braking energy is fed back to the first DC bus and the DC bus voltage rises to the first target value U0, and to generate a second control signal when the DC bus voltage drops to the second target value U1 during the process of absorbing braking energy in the resistor band 101. The first control signal and the second control signal are transmitted to the IGBT switch 102a through the pulse board 102b to control the IGBT switch 102a to turn on and off respectively.

[0071] In practical implementation, the pulse board is mainly used to control the on and off of the IGBT switching transistors, while the control board is mainly used to implement control functions with the host computer and can communicate with external devices (host computer). The control board 103c only needs to be connected to bus 1. The model of the IGBT switching transistor can be selected according to the bus voltage of bus 1.

[0072] The chopper module provided in this embodiment controls the chopper to be turned on and off by using a first target value and a second target value. When the braking energy is fed back to the DC bus, causing the DC bus voltage to rise to the first target value, the chopper circuit is turned on. At this time, the DC bus voltage is directly applied to the resistor band to absorb the braking energy. As the braking energy is absorbed, the DC bus voltage will drop to the second target value, thereby cutting off the chopper circuit. The control signal of the control board is transmitted to the IGBT switching transistor via the pulse board. By implementing the above voltage control method, the braking capacity and reliability of the braking resistor can be improved, avoiding the problem of insufficient reliability due to large wear of hydraulic brake friction pads.

[0073] In some embodiments, the chopper module includes:

[0074] IGBT switching transistor 102a;

[0075] The pulse board 102b is connected to the IGBT switching transistor 102a;

[0076] The control board 102c is connected to the pulse board 102b and is used to generate a third control signal to control the duty cycle of the IGBT switch 102a during the process of the resistor band 101 absorbing braking energy. The third control signal is transmitted to the IGBT switch 102a through the pulse board 102b to dynamically adjust the working current of the resistor band 101 so that the working current reaches the target current value.

[0077] The chopper module provided in the embodiments of this application dynamically adjusts the working current of the resistor band to achieve the target current value. The control signal of the control board is transmitted to the IGBT switching transistor via the pulse board. By implementing the above-mentioned current control method, the braking capability and reliability of the braking resistor can be improved, avoiding the problem of insufficient reliability due to large wear of hydraulic brake friction pads. This achieves precise current control during the process of the resistor band absorbing braking energy.

[0078] In some embodiments, the chopper module includes:

[0079] IGBT switching transistor 102a;

[0080] The pulse board 102b is connected to the IGBT switching transistor 102a;

[0081] Control board 103c, connected to pulse board 102b, is used to generate a first control signal when the braking energy is fed back to the first DC bus, causing the DC bus voltage to rise to a first target value U0, and to generate a second control signal when the DC bus voltage drops to a second target value U1 during the process of the resistor band 101 absorbing braking energy. The first and second control signals are transmitted to IGBT switch 102a through pulse board 102b to control the IGBT switch 102a to turn on and off, respectively. Control board 103c is also used to generate a third control signal to control the duty cycle of IGBT switch 102a during the process of the resistor band 101 absorbing braking energy. The third control signal is transmitted to IGBT switch 102a through pulse board 102b to dynamically adjust the operating current of resistor band 101 so that the operating current reaches the target current value.

[0082] Based on the chopper module provided in this embodiment, the chopper is turned on and off by using a first target value and a second target value. When the braking energy is fed back to the DC bus, causing the DC bus voltage to rise to the first target value, the chopper circuit is turned on. At this time, the DC bus voltage is directly applied to the resistor strip to absorb the braking energy. As the braking energy is absorbed, the DC bus voltage will drop to the second target value, thereby cutting off the chopper circuit. This achieves dynamic voltage adjustment during the operation of the resistor strip and dynamically adjusts the operating current of the resistor strip to reach the target current value. The control signal from the control board is transmitted to the IGBT switch via the pulse board. By implementing the above voltage control and current control methods, the braking capacity and reliability of the braking resistor can be improved, avoiding the problem of insufficient reliability due to high wear of hydraulic brake friction pads. This achieves precise control of voltage and current during the process of the resistor strip absorbing braking energy.

[0083] In some embodiments, the cooling fan includes a DC fan 103a or an AC fan 103b.

[0084] When the cooling fan includes a DC fan 103a, the power supply line of the DC fan 103a is connected in parallel to the resistor strip 101.

[0085] In the case where the cooling fan includes an AC fan 103b, the power cord of the AC fan 103b is connected to the inverter 104, and the inverter 104 is connected to the first DC bus (e.g., Figure 3 (as shown in the right figure) or the second DC bus of the electric wheel dump truck ( Figure 4Bus 2), the first DC bus is, for example, the DC bus of the inverter, and the second DC bus is, for example, the bus of other intermediate DC voltage links of the electric wheel dump truck. The inverter 104 obtains voltage from the DC bus and processes it into AC power, which is then transmitted to the AC fan 103b for power supply, forming an inverter circuit. The AC fan is, for example, a three-phase AC fan, which is powered separately and not directly connected in parallel to the resistor for power supply. In this way, an inverter is set up to convert DC power into AC power by taking the voltage from the DC bus. When the braking energy is fed back to the first DC bus and the DC bus voltage rises to the first target value U0, the operating frequency of the AC fan 103b increases to the rated point. When the DC bus voltage drops to the second target value U1, the operating frequency of the AC fan 103b drops to idle speed.

[0086] Since the power supply line of the AC fan is connected to the DC bus via the inverter, the inverter is powered by converting DC power to AC power by taking the DC bus voltage. This independent power supply method does not depend on the conduction of the resistor band. When the DC bus voltage drops to the second target value and the chopper circuit is cut off, the operating frequency of the AC fan can be reduced to idle speed and continue to work, thus improving the heat dissipation performance of the braking resistor.

[0087] In practical implementation, DC fans operate by using a parallel resistor voltage divider to obtain the rated operating voltage. This method is simple in operation, structure, and control, and the cost of individual resistors is relatively low. However, the DC motor requires regular maintenance and carbon brush replacement. Furthermore, worn carbon brushes can accumulate inside the motor, potentially causing poor insulation and short circuits. AC fans are essentially maintenance-free and can be independently controlled by variable frequency drive (VFD). They can also operate when the IGBT switch is off. However, their structure is more complex than DC fans, requiring an inverter, and their procurement cost is higher than that of the braking resistor used in DC fans. In practical applications, different types of cooling fans can be selected based on specific requirements.

[0088] When the voltage of the first DC bus is relatively high, the voltage through the inverter cannot provide the rated operating voltage for the cooling fan. A DC-DC module needs to be added to step down the voltage to achieve this function. Bus 1 and Bus 2 can be connected in parallel, or another bus can be used.

[0089] In some embodiments, the inverter 104 may be a DC / AC inverter, and a step-down circuit 105 may be provided on the first DC bus or the second DC bus connected to the inverter 104. The step-down circuit 105 may be a DC / DC step-down circuit. By providing the step-down circuit, the DC bus voltage that does not meet the rated operating voltage of the AC fan can be processed into the voltage for supplying power to the AC fan.

[0090] In specific implementations, such as Figure 4 As shown, a voltage sensor and a current sensor are also installed on the DC bus connected to the step-down circuit 105. The voltage sensor is used to detect the DC bus voltage on the DC bus connected to the step-down circuit 105, and the current sensor is used to detect the current on the DC bus connected to the step-down circuit 105. If the DC bus voltage detected by the voltage sensor does not meet the rated operating voltage of the AC fan, the step-down circuit 105 processes it into a voltage that can supply power to the AC fan, and transmits it to the AC fan 103b via the inverter 104.

[0091] Because AC fans use inverters, they can be controlled independently. When the sensor detects that the bus voltage has risen to a level requiring chopper braking, the fan's operating frequency will be increased to the rated point. When chopper braking is not needed, the fan's operating frequency can be reduced to idle speed. This operating mode can greatly improve the heat dissipation capacity of the resistor. Compared to DC fans, which do not operate when the chopper module is not working because they are not powered, resulting in residual heat accumulation and inability to dissipate heat in time, AC fans operate at idle speed, meaning the resistor box is still dissipating heat. Therefore, AC fan resistors are more reliable than DC fan resistors.

[0092] In some embodiments, the braking resistor of the electric wheel dump truck further includes at least one of a voltage sensor 106 and a current sensor 107. The voltage sensor 106 is disposed between the positive and negative terminals of the first DC bus and is used to detect the DC bus voltage; the current sensor 107 is disposed between the second terminal of the chopper module and the positive terminal of the first DC bus and is used to detect the operating current of the resistor band 101. By providing the voltage and current sensors, the DC bus voltage and the operating current of the resistor band can be monitored, enabling effective control of the voltage and current.

[0093] In the specific implementation, a voltage sensor 106 and a current sensor 107 are installed inside the braking resistor box. The voltage sensor 106 is used to detect the voltage of the DC bus, and the current sensor 107 is used to detect the current when the braking resistor is working.

[0094] In some embodiments, an electric wheel dump truck is also provided, including the aforementioned electric wheel dump truck braking resistor. Since the aforementioned braking resistor employs a chopper module-based switching on and off method for electric braking, the braking resistor itself possesses control functionality, thus its application is not limited by whether the electric wheel dump truck's converter has control functionality. Simultaneously, directly connecting the braking resistor to the DC bus effectively solves the problem of high braking energy and limited energy recovery (especially for pure electric mining trucks), where relying solely on hydraulic brake friction pads results in high wear and insufficient reliability. By combining the braking resistor's inherent control functionality with its direct connection to the DC bus, the braking capacity of the braking resistor can be effectively increased, its reliability significantly improved, and its application is not limited by whether the electric wheel dump truck's converter has control functionality, thus significantly improving the electric braking performance of the electric wheel dump truck.

[0095] Example 2:

[0096] Another embodiment of this application relates to a voltage control method for a braking resistor of an electric wheel dump truck. The braking resistor of the electric wheel dump truck can be the same as the one described in the foregoing embodiments. This voltage control method can be applied to electronic devices with communication, computing, and data storage capabilities, such as the control board in the above embodiments. The specific process of this method can be as follows: Figure 5 As shown, it includes:

[0097] Step 201: Obtain the DC bus voltage on the first DC bus connected to the braking resistor.

[0098] Step 202: Calculate the difference Ue between the first target value and the DC bus voltage;

[0099] Step 203: Based on the difference Ue and the first preset threshold Uh1 and the second preset threshold Uh2, the following voltage control is performed:

[0100] When Ue=0, the chopper module is turned on, the braking resistor starts working, and the cooling fan starts dissipating heat.

[0101] During the operation of the braking resistor, if Ue > 0 and |Ue| < Uh2, the chopper module is in the on state; if Ue > 0 and |Ue| ≥ Uh2, the chopper module is in the off state, and when |Ue| = Uh2, the DC bus voltage drops to the second target value U1; if Ue < 0 and 0 < |Ue| < Uh1, the chopper module is in the on state and generates overcurrent or overvoltage alarm information; if Ue < 0 and Uh1 < |Ue|, the chopper module is off and generates a stop alarm information.

[0102] The voltage control method for the braking resistor of the electric wheel dump truck provided in the embodiments of this application controls the voltage by using the difference between the first target value and the DC bus voltage, and the difference range determined by the first preset threshold and the second preset threshold. Different alarm information is generated under different conditions that exceed the difference range, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system fails.

[0103] In one example, the voltage control mode of the chopper circuit can adopt the Bang-Bang chopper control method (hysteresis control). The first target value U0 for starting chopper is set. That is, when the braking energy is fed back to the DC bus, causing the voltage detected by the voltage sensor to rise to a certain voltage U0 value, the chopper module is turned on, the chopper circuit is turned on, and the voltage is directly applied to the resistor strip. The resistor strip absorbs the braking energy. When the DC bus voltage drops to a first target value U1 for turning off chopper, the chopper module is turned off and the chopper circuit is disconnected, where U1 < U0.

[0104] Continuing with the previous example, the steps for the voltage control mode described above are as follows:

[0105] (1) Determine the set value (U0): the first target value that the system is expected to achieve.

[0106] (2) Obtain system output (Us): Measure or estimate the current output voltage value of the system.

[0107] (3) Calculate the difference (Ue): Calculate the difference between the set value and the system output, i.e., Ue = U0 - Us.

[0108] (4) Set preset threshold (Uh): Select an appropriate first preset threshold Uh1 and a second preset threshold Uh2 to define the difference range within which the controller remains unchanged.

[0109] (5) Determine whether the difference exceeds the threshold: compare the magnitude of the difference with the threshold.

[0110] ①When Ue=0, the IGBT switch is turned on, the braking resistor box starts working, and enters the turn-on mode;

[0111] When entering the turn-on mode, Ue > 0 and |Ue| < Uh2, the IGBT switch remains on, and it operates normally in chopper mode;

[0112] When entering the turn-on mode, Ue > 0 and |Ue| ≥ Uh2, the IGBT switch is turned off normally without any processing;

[0113] ②When Ue < 0 and |Ue| < Uh1, the IGBT switch is turned on and an alarm is triggered indicating possible overcurrent or overvoltage.

[0114] ③When Ue < 0 and Uh1 < |Ue|, the IGBT switch turns off the protection resistor and sends an alarm message on the CAN bus, directly alerting the driver to stop the vehicle as soon as possible.

[0115] (6) Continuously monitor the system output until the difference exceeds the threshold again, and repeat step (5).

[0116] Figure 6 The diagram illustrates the voltage control principle of this embodiment, showing the performance of the DC bus voltage during the braking energy absorption process and the strategy at different voltage ranges. At time t0, when the DC bus voltage reaches the set threshold (Us = U0, Ue = 0), the IGBT switch is turned on, the resistor band is loaded with voltage to absorb braking energy, and the resistor band begins to heat up. Simultaneously, the DC fan connected in parallel with the resistor starts working by obtaining voltage through voltage division to dissipate heat from the resistor box. At time t1, the DC bus voltage drops to Us = U1. During this period, |Ue| < Uh2, and the IGBT switch remains on until the threshold |Ue| = Uh2, at which point the IGBT switch turns off. The continuous accumulation of braking energy causes the DC bus voltage to rise continuously. At time t2, it reaches the IGBT switch's turn-on point (Us = U0), and the DC bus voltage returns to the state between t0 and t1. Three scenarios may occur: ① The braking energy is insufficient to cause the DC bus voltage to rise, and it will continue to decrease until the IGBT switch turns off. ① The DC bus voltage will still repeat the normal chopping waveform as t0-t2, so that the intermediate DC voltage is maintained between U0 and U1; ② Abnormal working mode: When Us>U0, but |Ue|<Uh1, an alarm will be triggered for a period of time. However, at this time, the braking energy margin of the resistor should be able to maintain the normal operation of the resistor. If the voltage increases further and |Ue|>Uh1, exceeding the resistance band's own bearing capacity, a serious fault should be reported immediately, which may cause personal injury and equipment damage.

[0117] The voltage is controlled by the difference between the first target value and the DC bus voltage, and the difference range determined by the first preset threshold and the second preset threshold. Different alarm messages are generated under different conditions that exceed the difference range, so that the braking resistor of the electric wheel dump truck has fault diagnosis and self-protection functions. When the system fails, it can promptly alarm, indicating possible overcurrent or overvoltage, and informing the driver to stop for maintenance. This effectively solves the problem that the current braking resistor does not have self-fault detection and self-diagnosis functions.

[0118] Example 3:

[0119] Another embodiment of this application relates to a current control method for the braking resistor of an electric wheel dump truck, which can be applied to electronic devices with communication, computing, and data storage capabilities, such as the control board in the above embodiment. The specific process can be as follows: Figure 7 As shown, it includes:

[0120] Step 301: With the chopper module in the ON state, obtain the DC bus voltage and the operating current of the braking resistor strip on the first DC bus connected to it.

[0121] Step 302: Calculate the current value based on the DC bus voltage and the design resistance value of the braking resistor band;

[0122] Step 303: Determine whether the braking resistor band has a fault based on the error between the calculated current value and the operating current: if the error is the set value, the braking resistor band has no fault; if the error is greater than the set value, the braking resistor band has a short circuit fault; if the error is less than the set value, the braking resistor band has an open circuit fault.

[0123] The current control method for the braking resistor of the electric wheel dump truck provided in this embodiment, during the process of dynamically adjusting the working current of the braking resistor band to reach the target current value, diagnoses whether the braking resistor band has a short circuit or open circuit fault based on the error between the current calculation value of the braking resistor band and the working current of the braking resistor band, and generates corresponding alarm information, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system malfunctions.

[0124] In practical implementation, current control primarily considers the impact of current on the device, thus requiring precise current control. This is achieved by using a PWM wave to control the duty cycle of the IGBT switch and consequently, the output current. Figure 8 It can be seen that during the operation of the braking resistor (IGBT switch is on), a voltage is applied to the resistor band. When the IGBT switch is off, there is no voltage on the resistor band, and therefore no current flows. Figure 9 It can be seen that by controlling the ratio of the IGBT switching time to the total operating cycle using PWM pulses, i.e., the duty cycle D = (t1-t0) / (t2-t0), the magnitude of the effective current can be controlled. The effective current value can be obtained by integrating the current to obtain the equivalent current within one switching cycle. The integral object can be obtained by collecting values ​​from a current sensor, or, if no current sensor is set, the collected value ic can be derived using Ohm's law for a resistive load: ic = U / R. The calculated value is = ic + Δi, where Δi is a set value. This error is caused by the resistance of the resistor increasing with temperature during the absorption of braking energy. The effective value of the output current is compared with the target current value it, and the duty cycle is adjusted accordingly to dynamically regulate the output current value towards the target current value it.

[0125] Example 4:

[0126] Another embodiment of this application relates to a control method for the braking resistor of an electric wheel dump truck, which can be applied to electronic devices with communication, computing, and data storage capabilities, such as the control board in the above embodiment. The method in this embodiment includes: the voltage control method and the current control method of the braking resistor of the electric wheel dump truck in the foregoing embodiment. The voltage control method and the current control method of the braking resistor of the electric wheel dump truck are detailed in the foregoing embodiment and will not be repeated here.

[0127] By using voltage and current control in the above methods, precise control of voltage and current can be achieved during the process of the resistor absorbing braking energy, thereby improving the braking capacity and reliability of the braking resistor and avoiding the problem of insufficient reliability due to large wear of hydraulic brake friction pads.

[0128] Example 5:

[0129] Another embodiment of this application relates to a voltage control device for the braking resistor of an electric wheel dump truck. The implementation details of the voltage control device for the braking resistor of this embodiment are described below. The following details are provided for ease of understanding and are not essential for implementing this solution. A schematic diagram of the voltage control device for the braking resistor of this embodiment can be seen as follows: Figure 10 As shown, it includes a voltage acquisition module 401, a difference calculation module 402, and a voltage control module 403.

[0130] Voltage acquisition module 401 is used to acquire the DC bus voltage of the first DC bus connected to the braking resistor.

[0131] The difference calculation module 402 is used to calculate the difference Ue between the first target value and the DC bus voltage;

[0132] The voltage control module 403 is used to perform the following voltage control based on the difference Ue and the first preset threshold Uh1 and the second preset threshold Uh2:

[0133] When Ue=0, the chopper module is turned on, the braking resistor starts working, and the cooling fan starts dissipating heat.

[0134] During the operation of the braking resistor, if Ue > 0 and |Ue| < Uh2, the chopper module is in the on state; if Ue > 0 and |Ue| ≥ Uh2, the chopper module is in the off state, and when |Ue| = Uh2, the DC bus voltage drops to the second target value U1; if Ue < 0 and 0 < |Ue| < Uh1, the chopper module is in the on state and generates overcurrent or overvoltage alarm information; if Ue < 0 and Uh1 < |Ue|, the chopper module is off and generates a stop alarm information.

[0135] The voltage control device for the braking resistor of the electric wheel dump truck provided in this embodiment controls the voltage by the difference between the first target value and the DC bus voltage, and the difference range determined by the first preset threshold and the second preset threshold. Different alarm information is generated under different conditions that exceed the difference range, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system fails.

[0136] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed in this application; however, this does not mean that other units are absent in this embodiment.

[0137] Example 6:

[0138] Another embodiment of this application relates to a current control device for the braking resistor of an electric wheel dump truck. The implementation details of the current control device for the braking resistor of this embodiment are described below. The following details are provided for ease of understanding and are not essential for implementing this solution. A schematic diagram of the current control device for the braking resistor of this embodiment can be seen as follows: Figure 11 As shown, it includes a current acquisition module 501, an error calculation module 502, and a current control module 503.

[0139] The current acquisition module 501 is used to acquire the DC bus voltage and the operating current of the braking resistor band on the first DC bus connected to the chopper module when the chopper module is turned on.

[0140] The error calculation module 502 is used to calculate the current value based on the DC bus voltage and the resistance design value of the braking resistor band.

[0141] The current control module 503 is used to determine whether the braking resistor band has a fault based on the error between the calculated current value and the operating current: if the error is the set value, the braking resistor band has no fault; if the error is greater than the set value, the braking resistor band has a short circuit fault; if the error is less than the set value, the braking resistor band has an open circuit fault.

[0142] The current control method for the braking resistor of the electric wheel dump truck provided in this embodiment, during the process of dynamically adjusting the working current of the braking resistor band to reach the target current value, diagnoses whether the braking resistor band has a short circuit or open circuit fault based on the error between the current calculation value of the braking resistor band and the working current of the braking resistor band, and generates corresponding alarm information, so that the braking resistor of the electric wheel dump truck has a self-protection function and can alarm in time when the system malfunctions.

[0143] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed in this application; however, this does not mean that other units are absent in this embodiment.

[0144] Example 7:

[0145] Another embodiment of this application relates to a control device for the braking resistor of an electric wheel dump truck, including the voltage control device and the current control device for the braking resistor of the electric wheel dump truck as described in the foregoing embodiments. Details of the voltage control device and the current control device for the braking resistor of the electric wheel dump truck are provided in the foregoing embodiments and will not be repeated here.

[0146] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed in this application; however, this does not mean that other units are absent in this embodiment.

[0147] Example 8:

[0148] Another embodiment of this application relates to an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the methods described in the above embodiments.

[0149] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0150] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0151] Example 9:

[0152] Another embodiment of this application relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the methods described in the above embodiments.

[0153] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0154] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A braking resistor for an electric wheel dump truck, comprising a resistor strip and a cooling fan for dissipating heat from the resistor strip, characterized in that, It also includes a chopper module; the first end of the chopper module is connected to a resistor strip, the second end of the chopper module is connected to the positive terminal of the first DC bus of the electric wheel dump truck, the resistor strip is connected to the negative terminal of the first DC bus, the chopper module is turned on when the braking energy is fed back to the first DC bus and the DC bus voltage rises to a first target value, so that the DC bus voltage is loaded onto the resistor strip to absorb the braking energy, and the chopper module is turned off when the DC bus voltage drops to a second target value during the process of the resistor strip absorbing the braking energy.

2. The braking resistor for an electric wheel dump truck according to claim 1, characterized in that, The chopper module includes: IGBT switching transistor; The pulse board is connected to the IGBT switching transistor; A control board, connected to the pulse board, is used to generate a first control signal when the braking energy is fed back to the first DC bus and the DC bus voltage rises to a first target value, and to generate a second control signal when the DC bus voltage drops to a second target value during the process of the resistor absorbing braking energy. The first control signal and the second control signal are transmitted to the IGBT switch through the pulse board to control the IGBT switch to turn on and off respectively.

3. The braking resistor for an electric wheel dump truck according to claim 1, characterized in that, The chopper module includes: IGBT switching transistor; The pulse board is connected to the IGBT switching transistor; A control board, connected to the pulse board, is used to generate a third control signal to control the duty cycle of the IGBT switch during the process of the resistor band absorbing braking energy. The third control signal is transmitted to the IGBT switch through the pulse board to dynamically adjust the operating current of the resistor band so that the operating current reaches the target current value.

4. The braking resistor for an electric wheel dump truck according to claim 1, characterized in that, The cooling fan includes a DC fan or an AC fan; In the case where the cooling fan includes a DC fan, the power supply line of the DC fan is connected in parallel to the resistor strip; When the cooling fan includes an AC fan, the power line of the AC fan is connected to an inverter, and the inverter is connected to the first DC bus or the second DC bus of the electric wheel dump truck; when the braking energy is fed back to the first DC bus and the DC bus voltage rises to the first target value, the operating frequency of the AC fan is increased to the rated point; when the DC bus voltage drops to the second target value, the operating frequency of the AC fan drops to idle speed.

5. The braking resistor for an electric wheel dump truck according to claim 4, characterized in that, A step-down circuit is also provided on the first DC bus or the second DC bus connected to the inverter.

6. The braking resistor for an electric wheel dump truck according to claim 1, characterized in that, It also includes at least one of a voltage sensor and a current sensor; A voltage sensor is disposed between the positive and negative terminals of the first DC bus to detect the DC bus voltage. A current sensor is positioned between the second terminal of the chopper module and the positive terminal of the first DC bus to detect the operating current of the resistor band.

7. A voltage control method for the braking resistor of an electric wheel dump truck according to any one of claims 1 to 6, characterized in that, include: Obtain the DC bus voltage on the first DC bus connected to the resistor band; Calculate the difference Ue between the first target value and the DC bus voltage; Based on the difference Ue and the first preset threshold Uh1 and the second preset threshold Uh2, the following voltage control is performed: When Ue=0, the chopper module is turned on, the resistor band starts working, and the cooling fan starts dissipating heat. During the operation of the resistance band, if Ue > 0 and |Ue| < Uh2, the chopper module is in the ON state; if Ue > 0 and |Ue| ≥ Uh2, the chopper module is in the OFF state, and when |Ue| = Uh2, the DC bus voltage drops to the second target value; if Ue < 0 and 0 < |Ue| < Uh1, the chopper module is in the ON state and generates overcurrent or overvoltage alarm information; if Ue < 0 and Uh1 < |Ue|, the chopper module is OFF and generates shutdown alarm information.

8. A current control method for the braking resistor of an electric wheel dump truck according to any one of claims 1 to 6, characterized in that, include: With the chopper module in the ON state, the DC bus voltage and the operating current of the resistor strip on the first DC bus connected to the resistor strip are obtained. Based on the DC bus voltage and the resistance design value of the resistance band, calculate the current value; Based on the error between the calculated current value and the operating current, it is determined whether the resistor band has a fault: if the error is the set value, the resistor band has no fault; if the error is greater than the set value, the resistor band has a short circuit fault; if the error is less than the set value, the resistor band has an open circuit fault.

9. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method as described in claim 7 or 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of claim 7 or 8.

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