Active discharge redundancy method for crane

Abstract

The invention discloses an active discharge redundancy method for a crane, belongs to the technical field of active discharge of cranes, and aims to solve the problems of low discharge speed, incomplete discharge, single discharge means and incapability of discharging voltage of a fault branch and a bus capacitor of a high-voltage system when a fault occurs in the prior art. According to the method, a certain branch driver is reserved as a system branch for discharging of a system bus, and when other branches fail and cannot discharge, a system branch Km is adopted for discharging. When a system branch discharges, in order to reduce the discharge capacity of a driver of the system branch, low-voltage DCDC and PTC are adopted to discharge a bus capacitor in advance, and after the voltage is reduced to the voltage within the working range, the driver is adopted to perform active discharge, so that the active discharge time of the driver is shortened, and heating of the driver of the branch electric cylinder is reduced. When the whole vehicle breaks down seriously, the bleeder resistor is used for releasing bus voltage, and it is guaranteed that discharging is achieved in the fault state.

Description

Technical Field

[0001] The invention belongs to the technical field of active discharge of cranes, and in particular relates to an active discharge redundancy method for cranes. Background Art

[0002] Traditional cranes mostly use hydraulic power sources, using hydraulic cylinders and other mechanisms to extend and retract horizontal or vertical outriggers, preparing the crane for lifting operations. Hydraulic motors and cylinders are used to perform heavy lifting tasks such as boom slewing, luffing, lifting, and retracting, ensuring precise and stable delivery of the hoisted object. With the advancement of electrification in crane operations, electric cylinders, which use mechanical mechanisms to convert the motor's rotational motion into linear motion, are now being used for applications such as outriggers, luffing, and steering. Reducer mechanisms can be used to apply the motor's rotational motion to crane slewing and lifting operations, as well as driving hydraulic pumps. This is achieving electrification of crane operations.

[0003] The lifting system driven by an electric cylinder is mainly composed of an electric cylinder, a driver, a power battery, and high-voltage accessories. In a lifting system driven by an electric cylinder, multiple electric cylinders are used to realize functions such as boom length adjustment, boom extension and retraction, horizontal / vertical leg extension and retraction, and vehicle steering. These functions are controlled by multiple drivers, and the DC bus of each driver is connected in parallel with a thin-film energy storage capacitor. The power battery provides energy for the entire system, and its high-voltage level is usually around 600V, which is much higher than the safe voltage of 36V that the human body can withstand. When the system enters the power-off process or enters a safe state due to a fault, the power battery needs to be disconnected from each driver and high-voltage component. After the relay is disconnected, the capacitor on the high-voltage bus at the DC input end of the driver will store a certain amount of electricity. To prevent personal injury, the electricity needs to be released in a timely manner.

[0004] After the drive is powered off, system energy can be discharged through either passive or active discharge. Passive discharge utilizes the motor drive's own losses and friction in the motor's transmission mechanism to dissipate energy. However, this method suffers from slow discharge speeds. If the bus voltage cannot be quickly reduced to a safe value in the event of an accident, the potential risk of electric shock could cause secondary injuries to passengers and rescuers. Active discharge typically involves discharge through the motor windings or by using a discharge resistor between the busbars, controlled by a power switching device. Active discharge is generally required to last no longer than 3 seconds.

[0005] After the system enters the discharge process or emergency state, the driver's relay is disconnected. If one or some drivers fail to discharge actively, the bus voltage cannot be discharged quickly, and a certain voltage on the bus will exist, posing a safety risk.

[0006] Regarding active discharge technology, those skilled in the art have done a lot of work, but the work is mainly limited to how to achieve active discharge, specifically: Chinese patent publication number CN119217983B discloses an active discharge control method, electronic device, and readable storage medium. Upon detecting an abnormal active discharge state in a vehicle's motor windings, a redundant active discharge indication is generated. Based on the redundant active discharge indication, the vehicle's motor is controlled to perform active discharge via a pulse-width modulation (PWM) signal. This solution requires the addition of another control method to the controller when an abnormal active discharge occurs in a single controller, resulting in complex control. If a complete controller failure occurs, active discharge may be impossible or incomplete.

[0007] Chinese patent publication number CN118413155A discloses a plug-in operating system, device, and active discharge method. A motor controller uses an internal phase loss detection module to determine the phase loss state of the busbar's three-phase power to determine the busbar's disconnected state. If the busbar is determined to be disconnected, the busbar capacitor is controlled to actively discharge. Specifically, in a plug-in operating system that draws power directly from the front-end power grid via a circuit breaker, the motor controller can use the phase loss detection module to determine the disconnected state of the busbar's three-phase power to control the active discharge of the busbar capacitor within the motor controller. This enables plug-in cranes that use circuit breakers for high-voltage switching to achieve active discharge, eliminates the need for the vehicle controller to issue active discharge commands, simplifies the active discharge process, and improves its efficiency. It also avoids the problem of difficulty determining the voltage threshold when determining the disconnected state of the front-end power grid through voltage detection, making it impossible to accurately determine whether the busbar is disconnected. This technical solution primarily addresses the source of the active discharge command and simplifies the active discharge process. However, if the active discharge fails after a fault, there is a safety hazard.

[0008] Chinese patent publication number CN112977069B discloses a pre-charging and discharging system for hydrogen-powered vehicles and its charging and high-voltage reduction methods. The invention's high-voltage auxiliary power supply, first pre-charging circuit, and motor controller are connected in series to form a closed circuit. The fuel-electric boost FCDC is connected in parallel across the high-voltage auxiliary power supply, and the step-down DCL is connected in parallel across the motor controller. The second pre-charging circuit, fuel-electric air compressor controller, and high-voltage components are connected in series to form a branch circuit, which is connected in parallel across the high-voltage auxiliary power supply. The heater PTC is connected in parallel across the high-voltage auxiliary power supply. The fuel-electric PTC is connected in parallel across the high-voltage auxiliary power supply. In the present invention, if the fuel-electric air compressor controller and high-voltage components do not have active discharge functions, the vehicle's heater PTC or fuel-electric PTC performs discharge, shortening the discharge time of the support capacitor and allowing the vehicle's drive motor to first reduce high-voltage power without waiting for the fuel cell system's purge process. Furthermore, pre-charging is performed separately. In this solution, only the PTC is used to shorten the discharge time of the support capacitor, resulting in a single discharge method.

[0009] See also Figure 1 In the prior art, the power battery is connected to the high-voltage power distribution system through the relay Kbat. The high-voltage power distribution system is connected to the driver of the electric cylinder through relays K1 to Kn, and is connected to the high-voltage accessory-low-voltage DCDC through relay Kf1. The high-voltage accessory-low-voltage DCDC is hereinafter referred to as DCDC. The high-voltage accessory-air-conditioning PTC is connected through relay Kf2. The high-voltage accessory-air-conditioning PTC is hereinafter referred to as PTC. When the high-voltage power-off instruction is received, the various electric components are shut down first, and the relays K1 to Kn and Kf1 and Kf1 connected to the electric cylinder driver are disconnected to ensure that the power battery has no current output, and the relay Kbat is disconnected. After disconnecting the relays K1 to Kn and Kf1 and Kf1, the electric cylinder driver enters the active discharge process to discharge the bus capacitor voltage. This active discharge method has the following technical problems: 1) During power-off, K1 to Kn are closed, and the driver of each branch discharges the bus capacitor voltage of the branch. If the active discharge failure of the driver of this branch or the driver itself fails, the branch cannot discharge, and there is a high-voltage safety risk in this branch.

[0010] 2) No redundant discharge device is installed for the entire high-voltage system. If a serious fault occurs in the system, all drivers cannot discharge and the voltage of the high-voltage system bus capacitor cannot be discharged. Summary of the Invention

[0011] The purpose of the present invention is to propose an active discharge redundancy method for cranes to solve the problems of slow discharge speed, incomplete discharge, single discharge means and inability to discharge the voltage of the faulty branch and the high-voltage system bus capacitor when a fault occurs in the prior art.

[0012] To achieve the above-mentioned purpose, the present invention provides an active discharge redundancy method for cranes as follows: Step 1: After the high-voltage power distribution system receives the vehicle power-off command, the electric cylinder and high-voltage accessories shut down; Step 2: Disconnect the relay Kbat connecting the power battery and the high-voltage power distribution system; Step 3: Determine whether the vehicle's drive system has a serious fault. If so, enable the bleeder resistor to discharge the bus capacitor; if not, proceed to step 4. Step 4: Determine whether both the DCDC and PTC are faulty. If not, cycle to enable the DCDC and PTC and proceed to step 5. If so, proceed to step 6. Step 5: Determine whether the bus voltage is less than the set voltage. If not, continue to cycle to enable DCDC and PTC. If so, cancel DCDC and PTC and execute step 6. Step 6: Select a branch circuit with no faults in the electric cylinder driver as the system branch circuit, close the system branch relay Km and proceed to step 8; at the same time, disconnect the electric cylinder driver relays K1-Kn in other branches except the system branch circuit and proceed to step 7; Step 7: Determine whether the active discharge of the electric cylinder drivers of other branches except the system branch is faulty. The drivers of the branches without faults actively discharge. The relays corresponding to the branches with faults are closed, and step 8 is executed. Step 8: Active discharge of system branches.

[0013] The serious fault described in step 3 means that all branch electric cylinder drivers cannot work.

[0014] During the process of discharging the bus capacitor by enabling the discharge resistor as described in step 3, when the bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

[0015] The set voltage in step 5 is 300V.

[0016] The system branches described in step 6 will cyclically use different branch electric cylinder drivers as system branches each time the power is turned off.

[0017] In step seven, during the active discharge process of the branch drivers without faults, when the voltage of each bus of the branch drivers without faults is lower than the safety voltage, the discharge of each driver bus is completed.

[0018] In step eight, during the active discharge process of the system branch, when the system branch bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

[0019] The safety voltage is 60V.

[0020] The beneficial effects of the present invention are as follows: an active discharge redundancy method for cranes of the present invention reserves a branch driver as a system branch for system bus discharge. This system branch cyclically uses a different branch each time the power is turned off, stores branch information, and when the remaining branches are faulty and cannot be discharged, the system branch Km is used for discharge. When the system branch discharges, in order to reduce the discharge amount of the system branch driver, DCDC and PTC are used to pre-discharge the bus capacitor, and after the voltage is reduced to the working range voltage, the driver is used for active discharge, which reduces the time for active discharge of the driver and reduces the heating of the branch electric cylinder driver. When the whole vehicle has a serious fault, a discharge resistor is used to release the bus voltage, ensuring that discharge can still be achieved in the fault state. The active discharge redundancy device and system of the present invention, by controlling the high-voltage relay of the high-voltage distribution system, changes the circuit of the high-voltage system, and realizes the rapid discharge of the bus voltage by using different active discharge methods under different states of the whole vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the active discharge redundancy device in the prior art; Figure 2 This is a schematic diagram of the corresponding active discharge redundancy device of the present invention; Figure 3 This is a flow chart of an active discharge redundancy method for a crane according to the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0023] See also Figure 2 Compared to existing technologies, the present invention's device for an active discharge redundancy method for cranes incorporates a bleeder resistor, connected to the high-voltage power distribution system via a relay Kz. Each electric cylinder driver and high-voltage accessories are connected to the high-voltage power distribution system via a high-voltage relay, enabling a variety of high-voltage system connection configurations and flexible high-voltage circuit configuration.

[0024] See also Figure 3 The present invention provides a crane active discharge redundancy method as follows: Step 1: After the high-voltage power distribution system receives the vehicle power-off command, the electric cylinder and high-voltage accessories shut down; Step 2: Disconnect the relay Kbat connecting the power battery and the high-voltage power distribution system; Step 3: Determine whether the vehicle's drive system has a serious fault. If so, enable the bleeder resistor to discharge the bus capacitor; if not, proceed to step 4. Step 4: Determine whether both the DCDC and PTC are faulty. If not, cycle to enable the DCDC and PTC and proceed to step 5. If so, proceed to step 6. Step 5: Determine whether the bus voltage is less than 300V. If not, continue to cycle to enable DCDC and PTC. If so, disable DCDC and PTC and execute step 6. Step 6: Select a branch circuit with no faults in the electric cylinder driver as the system branch circuit, close the system branch relay Km and proceed to step 8; at the same time, disconnect the electric cylinder driver relays K1-Kn in other branches except the system branch circuit and proceed to step 7; Step 7: Determine whether the active discharge of the electric cylinder drivers of other branches except the system branch is faulty. The drivers of the branches without faults actively discharge. The relays corresponding to the branches with faults are closed, and step 8 is executed. Step 8: Active discharge of system branches.

[0025] The serious fault described in step 3 means that all branch electric cylinder drivers cannot work.

[0026] During the process of discharging the bus capacitor by enabling the discharge resistor as described in step 3, when the bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

[0027] The system branches described in step 6 will cyclically use different branch electric cylinder drivers as system branches each time the power is turned off.

[0028] In step seven, during the active discharge process of the branch drivers without faults, when the voltage of each bus of the branch drivers without faults is lower than the safety voltage, the discharge of each driver bus is completed.

[0029] In step eight, during the active discharge process of the system branch, when the system branch bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

[0030] The relay of the present invention can also be replaced by a power switch. The present invention can be applied to other high-voltage systems of engineering machinery.

[0031] The present invention reserves a branch driver of K1-Kn as the system branch Km to discharge the system bus voltage. Each time the system branch is powered off, a different branch is cyclically used as Km, and the information of each branch Km used is stored in the controller.

[0032] If a fault occurs in any of the remaining branches and discharge is impossible, the relay corresponding to the faulty branch closes and discharge is performed using the system branch Km. During system branch discharge, if the DCDC and PTC circuits are functioning properly, to minimize discharge in the system and branch drivers, the DCDC and PTC circuits are used to pre-discharge the bus capacitors, reducing the voltage to the minimum within the operating range. Active discharge is then performed using the system branch. In the event of a serious vehicle fault, a bleeder resistor is used to release the bus voltage.

Claims

1. An active discharge redundancy method for a crane, characterized in that: Specifically: Step 1: After the high-voltage power distribution system receives the vehicle power-off command, the electric cylinder and high-voltage accessories shut down; Step 2: Disconnect the relay Kbat connecting the power battery and the high-voltage power distribution system; Step 3: Determine whether the vehicle's drive system has a serious fault. If so, enable the bleeder resistor to discharge the bus capacitor; if not, proceed to step 4. Step 4: Determine whether both the DCDC and PTC are faulty. If not, cycle to enable the DCDC and PTC and proceed to step 5. If so, proceed to step 6. Step 5: Determine whether the bus voltage is less than the set voltage. If not, continue to cycle to enable DCDC and PTC. If so, cancel DCDC and PTC and execute step 6. Step 6: Select a branch circuit with no faults in the electric cylinder driver as the system branch circuit, close the system branch relay Km and proceed to step 8; at the same time, disconnect the electric cylinder driver relays K1-Kn in other branches except the system branch circuit and proceed to step 7; Step 7: Determine whether the active discharge of the electric cylinder drivers of other branches except the system branch is faulty. The drivers of the branches without faults actively discharge. The relays corresponding to the branches with faults are closed, and step 8 is executed. Step 8: Active discharge of system branches.

2. The active discharge redundancy method for a crane according to claim 1, characterized in that: The serious fault described in step 3 means that all branch electric cylinder drivers cannot work.

3. The active discharge redundancy method for a crane according to claim 1, characterized in that: During the process of discharging the bus capacitor by enabling the discharge resistor as described in step 3, when the bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

4. The active discharge redundancy method for a crane according to claim 1, characterized in that: The set voltage in step 5 is 300V.

5. The active discharge redundancy method for a crane according to claim 1, characterized in that: The system branches described in step 6 will cyclically use different branch electric cylinder drivers as system branches each time the power is turned off.

6. The active discharge redundancy method for a crane according to claim 1, characterized in that: In step seven, during the active discharge process of the branch drivers without faults, when the voltage of each bus of the branch drivers without faults is lower than the safety voltage, the discharge of each driver bus is completed.

7. The active discharge redundancy method for a crane according to claim 1, characterized in that: In step eight, during the active discharge process of the system branch, when the system branch bus voltage is discharged to be lower than the safety voltage, the system bus voltage discharge is completed.

8. The active discharge redundancy method for a crane according to claim 3, 6 or 7, characterized in that: The safety voltage is 60V.

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