Energy-saving method for crane

Abstract

The invention discloses an energy-saving method for a crane. The energy-saving method comprises the following steps: acquiring a voltage working range of a direct-current bus of a crane frequency converter and setting a voltage threshold value; constructing an energy-saving recovery system of the crane; setting an operation mode of the energy-saving recovery system of the crane; setting control logic of automatic opening and closing of the switch unit in the working mode; and the energy-saving recovery system of the crane is operated for charging and discharging. By utilizing the characteristics that the high-power nickel-metal hydride battery has the service life of over million times of shallow charging and shallow discharging and has no explosion and fire risk, the high-power nickel-metal hydride battery recovery device is directly hung on a direct-current bus of a frequency converter, so that transformation conversion is avoided, efficient recovery of regenerated electric energy of the crane and system simplification are realized, and the cost is reduced. The one-time purchase cost of direct-current conversion and battery management equipment is reduced, and the energy-saving efficiency of the crane is improved.

Description

Technical Field

[0001] The invention relates to the technical field of traction devices, and in particular to a crane energy-saving method. Background Art

[0002] In special equipment such as port cranes, ship unloaders, etc., when they are under heavy load or in braking condition, the motor will be in power generation state, resulting in reverse power supply. This is because when the equipment is under heavy load or braking, the motor needs to consume a lot of energy to drive the load or decelerate, so the magnetic field and current inside the motor will be reversed, resulting in power generation state.

[0003] According to data, during the heavy-load and no-load descent of a crane, the traction machine will be dragged in the reverse direction to generate electricity, converting the potential energy or kinetic energy during the descent into regenerative electrical energy. The electrical system of a traditional crane cannot effectively recover this energy, but instead consumes excess energy through braking resistors, resulting in energy losses of up to 30%. To solve these losses, existing technologies generally use energy storage units such as high-power nickel-hydrogen batteries or supercapacitors to recover and reuse regenerative electrical energy after DC-DC conversion.

[0004] Chinese patent document CN117748684A discloses a "high-power battery-based energy recovery system for a port ship unloader". It includes a ship unloader lifting inverter: used to power the port ship unloader lifting motor; a bidirectional DC-DC conversion module: used to detect the voltage of the DC bus of the ship unloader lifting inverter, and adjust the power supply voltage of the ship unloader lifting inverter according to a preset control process; a control detection unit: used to detect the power generation state of the port ship unloader lifting motor and send a control signal to the bidirectional DC-DC conversion module, and control the bidirectional DC-DC conversion module to convert the electric energy absorbed on the DC bus of the ship unloader lifting inverter; a battery pack: used to store the electric energy converted by the bidirectional DC-DC conversion module. The above technical solution uses a DC-DC conversion module, which has energy consumption losses and is complex to control, making it difficult to achieve efficient recovery of crane regenerated electric energy. Summary of the invention

[0005] The present invention mainly solves the technical problem that the original technical solution uses a DC-DC conversion module, has energy loss, and has complex control, making it difficult to achieve efficient recovery of crane regenerated electric energy. A crane energy-saving method is provided. The system includes a high-power nickel-hydrogen battery recovery device and a braking unit. The high-power nickel-hydrogen battery recovery device and the braking unit are connected in parallel to the inverter DC bus. By directly hanging the high-power nickel-hydrogen battery recovery device on the inverter DC bus, voltage conversion is avoided, and efficient recovery of crane regenerated electric energy and system simplification are achieved.

[0006] The above technical problem of the present invention is mainly solved by the following technical solution: The present invention comprises the following steps: S1 collects the voltage operating range of the DC bus of the crane inverter and sets the voltage threshold; S2 builds a crane energy-saving recycling system; S3 sets the operation mode of the crane energy-saving recovery system; S4 sets the control logic of automatic opening and closing of the switch unit in the working mode; S5 operates the crane energy-saving recovery system and performs charging and discharging.

[0007] Taking advantage of the fact that high-power nickel-hydrogen batteries have a service life of millions of shallow charges and discharges and no risk of explosion or fire, a high-power nickel-hydrogen battery recovery device is directly mounted on the inverter DC bus to reduce the one-time purchase cost of DC conversion and battery management equipment, thereby improving the energy-saving efficiency of the crane.

[0008] As a preferred embodiment, the step S1 specifically includes collecting the working range of the DC bus voltage of the inverter of the crane under various working conditions, and determining the upper limit U of the DC bus voltage max1 and the lower limit U min1 .

[0009] Preferably, the energy-saving recovery system for the crane comprises a high-power nickel-hydrogen battery recovery device, a brake unit and a frequency converter which are connected in sequence, and the frequency converter is connected in series between the traction machine and the mains.

[0010] Preferably, the high-power nickel-metal hydride battery recovery device comprises a circuit breaker, a fuse and a nickel-metal hydride battery module connected in sequence, the switch control unit is connected to the brake unit in sequence through the pre-charging circuit and the switch control unit, and the switch control unit comprises a high-voltage control switch and a low-voltage control switch. The switch control unit comprises at least 2 or more power switches. One of them is a low-voltage control switch, which is mainly used for control and protection when the battery is at low voltage; the other is a high-voltage control switch, which is mainly used for control and protection when the battery is at high voltage.

[0011] Preferably, the voltage of the nickel-hydrogen battery module matches the bus voltage, and the lower limit voltage U min2 Inverter bus voltage U min1 The upper limit voltage U max2 The bus voltage U max1 Between 0.8 and 1.2.

[0012] Preferably, the operation mode of the crane energy-saving recovery system in step S3 includes a maintenance mode and a working mode. In the maintenance mode, the high-voltage switch and the low-voltage switch are fixedly closed for device access maintenance; in the working mode, the high-voltage switch and the low-voltage switch are automatically opened and closed according to the detected voltage threshold.

[0013] Preferably, the switch unit in step S4 includes a high voltage switch, and the closing logic is: when the voltage across the nickel-metal hydride battery module is detected to be ≥U max3 , the high-voltage switch is disconnected, otherwise the high-voltage switch is closed; the high-voltage control switch disconnects the voltage U max3 Set the voltage lower than the brake unit’s opening voltage U max4 and is associated with the SOC upper limit state of the NiMH battery module.

[0014] As a preference, the U max3 The SOC state association strategy of the NiMH battery module is: find the charging voltage value U corresponding to the upper limit SOC of the NiMH battery module charge-SOCx , at this time U max3 , U charge-SOCx Satisfy the relationship: U max3 ≈U charge-SOCx , the upper limit SOC range of the NiMH battery is set to 60%-80%.

[0015] Preferably, the switch unit in step S4 includes a low-voltage switch, and the closing logic is: when the voltage across the nickel-metal hydride battery module is detected to be ≤U min3 , the low-voltage switch is disconnected, otherwise the low-voltage switch is closed; the low-voltage switch disconnects the voltage U min3 The setting is greater than the inverter bus voltage U min1 and is associated with the SOC lower limit state of the NiMH battery module.

[0016] As a preference, the U min3 The SOC state association strategy of the NiMH battery module is: find the discharge voltage value U corresponding to the lower limit SOC of the NiMH battery discharge-SOCx , at this time U min3 , U charge-SOCx Satisfy the relationship: U min3 ≈U discharge-SOCx , the lower limit SOC range of the NiMH battery is set to 20%-40%. The benefit of this setting is to prevent the high-power NiMH battery pack from over-discharging due to low voltage, which will affect the battery life.

[0017] The beneficial effects of the present invention are as follows: utilizing the characteristics of high-power nickel-hydrogen batteries, which have a service life of millions of shallow charges and discharges and no risk of explosion or fire, and directly hanging a high-power nickel-hydrogen battery recovery device on the DC bus of the inverter, thereby avoiding voltage conversion, achieving efficient recovery of crane regenerative electric energy and system simplification, reducing the one-time purchase cost of DC conversion and battery management equipment, and improving the energy-saving efficiency of the crane. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the present invention.

[0019] Figure 2 This is a connection structure diagram of an energy-saving system of the present invention.

[0020] In the figure, 1 is a high-power nickel-metal hydride battery recovery device, 11 is a circuit breaker, 12 is a fuse, 13 is a nickel-metal hydride battery module, 14 is a pre-charging circuit, 15 is a switch control unit, 151 is a high-voltage switch, 152 is a low-voltage switch, 2 is a brake unit, 21 is a brake switch, 22 is a brake resistor, 3 is a frequency converter, 31 is a rectifier module, 32 is an inverter module, and 4 is a traction machine. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions of the present application are further described in detail below through embodiments and in combination with the accompanying drawings. It should be understood that the specific implementation method described here is only an optimal embodiment of the present application, which is only used to explain the present application and does not limit the protection scope of the present application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] During the heavy-load and no-load descent of the crane, the traction machine will be dragged in the reverse direction to generate electricity, converting the potential energy or kinetic energy during the descent into regenerative electrical energy. The electrical system of traditional cranes cannot effectively recover this energy, but consumes excess electrical energy through braking resistors, resulting in energy losses of up to 30%.

[0023] Wasted energy is not only undesirable because it increases the amount of energy required by the system without performing any actual movement of the crane components, but it also has the disadvantage that the wasted energy is dissipated as heat, which increases the temperature of the hydraulic fluid in the system. The temperature increase reduces the quality of the hydraulic fluid and therefore affects the service frequency of the system. Therefore, by reducing the wasted energy, the impact of these associated problems will also be reduced.

[0024] To solve these losses, existing technologies generally use high-power nickel-metal hydride batteries or supercapacitors and other energy storage units to recycle and reuse the regenerated electric energy after DC-DC conversion. However, the DC-DC conversion module itself has energy loss and is complex to control.

[0025] Therefore, the present invention proposes a crane energy recovery system based on a high-power nickel-hydrogen battery, aiming to improve the energy recovery efficiency and solve the problems in the prior art. The system includes a high-power nickel-hydrogen battery recovery device and a braking unit. The high-power nickel-hydrogen battery recovery device includes a circuit breaker, a fuse, a pre-charging circuit, a switch control unit, and a high-power nickel-hydrogen energy storage battery module, and the components are connected in series in sequence. The high-power nickel-hydrogen battery recovery device and the braking unit are connected in parallel to the DC bus of the inverter. By directly connecting the high-power nickel-hydrogen battery recovery device to the DC bus of the machine inverter, voltage conversion is avoided, and efficient recovery of crane regenerated electric energy and system simplification are achieved.

[0026] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the operations (or steps) as sequential processes, many of the operations (or steps) therein can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the drawings; the process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0027] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0028] Embodiment: A crane energy saving method of this embodiment, such as Figure 1 Shown, including The following steps are involved: S1 collects the voltage operating range of the crane inverter DC bus and sets the voltage threshold. Collects the operating range of the crane inverter DC bus voltage under various working conditions and determines the DC bus voltage upper limit U max1 and the lower limit U min1 .

[0029] S2 constructs a crane energy-saving recovery system. The crane energy-saving recovery system includes a high-power nickel-hydrogen battery recovery device 1, a brake unit 2 and a frequency converter 3 connected in sequence, and the frequency converter 3 is connected in series between the traction machine 4 and the mains. The high-power nickel-hydrogen battery recovery device 1 includes a circuit breaker 11, a fuse 12 and a nickel-hydrogen battery module 13 connected in sequence, and the switch control unit 13 is connected to the brake unit 2 through a pre-charging circuit 14 and a switch control unit 15 in sequence. The switch control unit 15 includes a high-voltage control switch 151 and a low-voltage control switch. The switch control unit includes at least 2 or more power switches. One of them is a low-voltage control switch, which is mainly used for control and protection when the battery is at low voltage; the other is a high-voltage control switch, which is mainly used for control and protection when the battery is at high voltage.

[0030] The voltage of the nickel-hydrogen battery module 13 matches the bus voltage, and the lower limit voltage U min2 Inverter bus voltage U min1 The upper limit voltage U max2 The bus voltage U max1 Between 0.8 and 1.2.

[0031] S3 sets the operation mode of the crane energy-saving recovery system. The operation modes of the crane energy-saving recovery system include maintenance mode and working mode. In maintenance mode, the high-voltage switch and the low-voltage switch are fixedly closed for device access maintenance; in working mode, the high-voltage switch and the low-voltage switch are automatically opened and closed according to the detected voltage threshold.

[0032] S4 sets the control logic for automatic opening and closing of the switch unit in working mode.

[0033] The switch control unit includes at least two or more power switches. One is a low-voltage control switch, which is mainly used for control and protection when the battery is at low voltage; the other is a high-voltage control switch, which is mainly used for control and protection when the battery is at high voltage. The switch unit includes a high-voltage switch, and the closing logic is: when the voltage across the nickel-metal hydride battery module 13 is detected to be ≥U max3 , the high-voltage switch is disconnected, otherwise the high-voltage switch is closed; the high-voltage control switch 151 disconnects the voltage U max3 Set to be less than the opening voltage U of the brake unit 2 max4 , and is associated with the SOC upper limit state of the nickel-hydrogen battery module 13. max3 The SOC state association strategy of the nickel-hydrogen battery module 13 is: find the charging voltage value U corresponding to the upper limit SOC of the nickel-hydrogen battery module 13 charge-SOCx , at this time U max3 , U charge-SOCx Satisfy the relationship: U max3 ≈U charge-SOCx , the upper limit SOC range of the NiMH battery is set to 60%-80%.

[0034] Step S4: The switch unit includes a low voltage switch, and the closing logic is: when the voltage across the nickel-metal hydride battery module 13 is detected to be ≤U min3 , the low-voltage switch is disconnected, otherwise the low-voltage switch is closed; the low-voltage switch disconnects the voltage U min3 The setting is greater than the inverter bus voltage U min1 , and is associated with the SOC lower limit state of the nickel-hydrogen battery module 13. min3 The SOC state association strategy of the NiMH battery module is: find the discharge voltage value U corresponding to the lower limit SOC of the NiMH battery discharge-SOCx , at this time U min3 , U charge-SOCx Satisfy the relationship: U min3≈U discharge-SOCx , the lower limit SOC range of the NiMH battery is set to 20%-40%. The benefit of this setting is to prevent the high-power NiMH battery pack from over-discharging due to low voltage, which will affect the battery life.

[0035] S5 runs the crane energy-saving recovery system and performs charging and discharging. Taking advantage of the high-power nickel-hydrogen battery's service life of millions of shallow charges and discharges and no risk of explosion or fire, the high-power nickel-hydrogen battery recovery device is directly connected to the inverter DC bus to reduce the one-time purchase cost of DC conversion and battery management equipment, thereby improving the energy-saving efficiency of the crane.

[0036] Embodiment 1 Embodiment 1 of the present application provides a Figure 2 The crane energy-saving system shown in the figure is directly connected to the crane system and significantly reduces the overall energy consumption of the crane through energy recovery and utilization. The system is specifically composed of a high-power nickel-hydrogen battery recovery device 1, a brake unit 2, and a frequency converter 3.

[0037] Among them, the high-power nickel-metal hydride battery recovery device 1, as the core component of the system, is mainly responsible for recovering braking energy during the operation of the crane and reusing it, thereby reducing the crane's electricity consumption. In order to ensure that the device can work normally and efficiently, it is recommended that its power be configured to 0.4 to 0.6 times the rated power of the inverter. For example, in medium and large crane systems with an inverter power of 200 to 400kW, a high-power nickel-metal hydride battery pack with a power of 100 to 200kW can be configured. In small crane systems (inverter power of 20 to 200kW), a high-power nickel-metal hydride battery pack with a power of 10 to 100kW can be configured to ensure that the energy recovery device still has sufficient energy recovery capacity and operational stability under high load and frequent use; The high-power nickel-metal hydride battery recovery device 1 and the brake unit 2 are connected in parallel to the high-voltage bus of the frequency converter 3. Under normal circumstances, the regenerated electric energy of the frequency converter 3 mainly flows into the high-power nickel-metal hydride battery recovery device 1 to achieve effective energy storage and reuse. When the high-power nickel-metal hydride battery recovery device 1 is overcharged or fails, the electric energy can safely flow into the brake unit 2 to protect the safety and stability of the system; The high-power nickel-hydrogen battery recycling device 1 includes multiple key components, including a circuit breaker 11, a fuse 12, a high-power nickel-hydrogen battery pack 13, a pre-charging circuit 14, and a switch control unit 15, etc. These components are connected in series to form a complete circuit. In order to ensure the safety and reliability of the system, the selection of key components is crucial. For example, the circuit breaker 11 is mainly used for overcurrent protection and access maintenance to ensure that the circuit is cut off in time when the current is abnormal, thereby preventing equipment damage.

[0038] The fuse 12 and the circuit breaker 11 together constitute an overcurrent protection mechanism of the system; The nickel-hydrogen battery pack adopts cylindrical nickel-hydrogen battery cells of the model 90940, which are connected in series and parallel in different numbers to form a high-power nickel-hydrogen battery pack 13 with matching system voltage and power; The switch control unit 15 is composed of a high voltage switch 151 and a low voltage switch 152 connected in series, and is responsible for real-time monitoring of the voltages on both sides of the circuit and controlling the on and off of the circuit to ensure the safety and stability of the system.

[0039] Wherein, the switch control unit 15 can automatically connect or disconnect the circuit according to the monitored voltage change to prevent possible electrical failure; The pre-charging circuit 14 is composed of two pre-charging relays and a pre-charging resistor, which ensures that when the high-power nickel-hydrogen battery module is connected to the inverter system, safe power supply can be achieved to avoid current shock generated when the system is powered on.

[0040] The crane energy-saving system solution in this embodiment ensures that an efficient, safe and reliable operating environment is provided while achieving energy recovery and reuse.

[0041] Embodiment 2 Based on the first embodiment, the second embodiment of the present application provides the following Figure 1 The crane energy saving system shown is connected to the inverter working and control process: S1. Collect the working range of the DC bus voltage of inverter 3 under various working conditions of the crane and determine the upper limit voltage U of the DC bus. max1 And the lower limit voltage U min1 ; When a crane is moving upward with a heavy load, the crane needs to lift the heavy object quickly, and the bus voltage of the DC bus may drop to 520-530V, which is close to the lower limit U min1 =500V. Usually when a crane is heavily loaded and moving downward, the motor reverses to generate regenerative power, causing the bus voltage of the DC bus to rise to 680-690V, close to the upper limit U max1 =700V.

[0042] S2. Based on the principle that the voltage of the high-power nickel-hydrogen battery pack 13 matches the DC bus voltage of the inverter 3, the number of battery modules connected in series and parallel is reasonable; When the working range of the DC bus voltage of the inverter 3 is 500-700V, the high-power nickel-hydrogen battery pack 13 can be formed by connecting 480 single cells in series, and the working voltage range of the battery pack is 480V-720V, and the nominal voltage is 576V. min2 =480V, is U min10.96 times of the battery pack working upper limit voltage U max2 =720V, is U max1 When the working range of the DC bus voltage of the inverter 3 is 300-500V, the high-power nickel-hydrogen battery pack 13 can be composed of 320 single cells connected in series, and the working voltage range of the battery pack is 320V-480V, and the nominal voltage is 384V. Among them, the working lower limit voltage U min2 =320V, is U min1 1.07 times, the upper limit voltage of the battery pack is U max2 =480V, is U max1 When the working range of the DC bus voltage of the inverter 3 is 200-400V, the high-power nickel-hydrogen battery pack 13 can be composed of 240 single cells in series, and the working voltage range of the battery pack is 240V-360V, and the nominal voltage is 384V. Among them, the working lower limit voltage U min2 =240V, is U min1 1.2 times of the battery pack working upper limit voltage U max2 =360V, is U max1 1.1 times of.

[0043] S3, sequentially connect the circuit breaker 11, the fuse 12, the switch control unit 15, the pre-charging circuit 14, and the nickel-hydrogen battery pack 13 in series to form a high-power nickel-hydrogen battery energy recovery device 1, and then connect the brake unit 2 and the high-power nickel-hydrogen battery energy recovery device 1 in parallel to the bus voltage of the inverter 3; The switch control unit 15 is composed of two power switches, one of which is a low-voltage switch 152, which is mainly used for control and protection when the battery is at low voltage; the other switch is a high-voltage switch 151, which is mainly used for control and protection when the battery is at high voltage.

[0044] In different working conditions, for example, in normal working state, when the voltage across the battery is 576V, the high-voltage switch 151 and the low-voltage switch 152 are closed, allowing the battery to charge and discharge to participate in potential energy recovery; if the battery pack voltage is lower than the set threshold of 550V, the low-voltage switch 152 will automatically disconnect, cutting off the nickel-hydrogen battery recovery device to prevent the battery from over-discharging. At this time, the inverter is powered by the mains power supply, and the low-voltage switch 152 will not close until the voltage recovers to above 550V; if the battery pack voltage is higher than the set protection threshold of 670V, the high-voltage switch 151 will be disconnected to prevent overcharging, and the regenerated electric energy of the inverter will flow to the standby brake unit. In addition, if the current in the circuit is greater than the selected fuse 12 is blown or the maximum current of the circuit breaker 11, the high-power nickel-hydrogen battery energy recovery device 1 will trip to ensure the safe operation of the system.

[0045] S4. The maintenance mode is set in the switch control unit 15, so that the high-voltage switch 151 and the low-voltage switch 152 are in a closed state, and then the circuit breaker 11 and the relay of the pre-charging circuit 14 are closed in sequence to connect the high-power nickel-hydrogen battery energy recovery device directly to the inverter bus circuit.

[0046] The switch control unit 15 has two mode switches, a maintenance mode and a working mode.

[0047] Among them, in the maintenance mode, the high-voltage switch 151 and the low-voltage switch 152 are in a long-closed state, which is mainly used for device access maintenance.

[0048] Among them, the pre-charging circuit will adjust the access operation according to the comparison between the battery voltage and the bus voltage: when the bus voltage is significantly different from the battery voltage during access, the relay in the pre-charging circuit will gradually close, and the resistor in the pre-charging circuit will play a buffering role, gradually balancing the voltage and avoiding current shock; when it is detected that the battery voltage is close to the inverter bus voltage, part of the pre-charging process can be skipped and the main circuit can be directly connected; when the system detects that the battery pack voltage is too low or exceeds the safety range, such as below 500V or above 700V, the system will automatically terminate the access operation and send an alarm signal to avoid damage to the equipment. Through the dynamic adjustment of the above different situations, the system can effectively control the access process of the energy recovery device to ensure safe access under various voltage conditions.

[0049] S5. The switch control unit 15 switches to the working mode, sets the control logic of the high-voltage switch 151 and the low-voltage switch 152, and controls the high-power nickel-hydrogen battery energy recovery device to charge and discharge.

[0050] The control logic automatically performs opening and closing operations based on the detected voltage across the switch and a set threshold value, thereby ensuring that the battery pack operates within a reasonable voltage range.

[0051] The control logic of the high voltage switch 151 is set as follows: When the voltage U across the high voltage switch 高压开关 Greater than or equal to 670VU max3 =670V, the high voltage switch 151 is disconnected to prevent the battery from overcharging. max3 It is determined based on the relationship between the SOC state and voltage of the nickel-hydrogen battery pack. When the SOC of the battery pack is 70%, the corresponding charging voltage is 670V, ensuring that the battery is not overcharged. At the same time, it is also lower than the opening voltage U of the brake switch 21. max4 , to prevent the battery pack voltage from being too high and damaging the system. That is: High voltage switch 151 disconnection condition: U 高压开关 ≥U max3 =670V; Closing condition of high voltage switch 151: U高压开关 <U max3 =670V; The control logic of the low voltage switch 152 is opposite to that of the high voltage switch 151 and is set as follows: When the low voltage switch 152 detects the voltage U 低压开关 Less than 550VU min3 =550V, the low voltage switch 152 is disconnected to prevent the battery pack from over-discharging. min3 Based on the SOC state of the nickel-hydrogen battery pack, when the battery SOC is 30%, the battery discharge voltage is 550V, which can avoid deep discharge of the battery and ensure the battery life. At the same time, it is greater than the minimum voltage U of the inverter bus. min1 , ensuring stable operation of the system.

[0052] Right now: Disconnection condition of high voltage switch 152: U 低压开关 ≤U min3 =550V; Closing condition of high voltage switch 152: U 高压开关＞ U min3 =550V; Through the control of the above-mentioned switch control unit strategy, the voltage at both ends of the battery pack and the voltage at both ends of the inverter can be stabilized between 550V-670V, that is, the nickel-hydrogen battery pack is controlled to perform shallow charge and discharge at 30% SOC-70% SOC, thereby improving the service life of the battery pack.

[0053] Through the embodiments of the present invention, it can be seen that the energy-saving system is directly connected to the DC bus, which reduces conversion losses; secondly, the nickel-hydrogen battery used has a service life of millions of shallow charges and discharges, has no risk of explosion or fire, and is suitable for high-frequency and long-term applications. The overall energy-saving efficiency of the system is improved by more than 3% compared with the traditional DC-DC conversion solution.

[0054] This invention is suitable for energy recovery scenarios in cranes and similar equipment, and can effectively reduce energy waste and improve economic benefits.

[0055] The specific embodiments described herein are merely examples of the spirit of the present invention. The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present application. It should be noted that a technician in the technical field to which the present application belongs may make various modifications or supplements to the described specific embodiments or replace them in a similar manner, but will not deviate from the spirit of the present application or exceed the scope defined in the attached claims. For a person of ordinary skill in the art, multiple variations and improvements may also be made without departing from the concept of the present application. Therefore, the scope of protection of this patent shall be subject to the attached claims.

Claims

1. A crane energy saving method, characterized in that: The following steps are involved: S1 collects the voltage operating range of the crane inverter DC bus and sets the voltage threshold; S2 builds a crane energy-saving recycling system; S3 sets the operation mode of the crane energy-saving recovery system; S4 sets the control logic of automatic opening and closing of the switch unit in the working mode; S5 operates the crane energy-saving recovery system and performs charging and discharging.

2. A crane energy saving method according to claim 1, characterized in that: The step S1 specifically includes collecting the working range of the DC bus voltage of the inverter under various working conditions of the crane, and determining the upper limit U of the DC bus voltage. max1 and the lower limit U min1 .

3. A crane energy saving method according to claim 1, characterized in that: The energy-saving recovery system for a crane comprises a high-power nickel-hydrogen battery recovery device (1), a brake unit (2) and a frequency converter (3) which are connected in sequence, and the frequency converter (3) is connected in series between a traction machine (4) and a mains power supply.

4. A crane energy saving method according to claim 3, characterized in that: The high-power nickel-metal hydride battery recovery device (1) comprises a circuit breaker (11), a fuse (12) and a nickel-metal hydride battery module (13) which are connected in sequence; the switch control unit (13) is connected to the brake unit (2) in sequence through a pre-charging circuit (14) and a switch control unit (15); the switch control unit (15) comprises a high-voltage control switch (151) and a low-voltage control switch (152).

5. A crane energy saving method according to claim 4, characterized in that: The voltage of the nickel-hydrogen battery module (13) matches the bus voltage, and the lower limit voltage U min2 Inverter bus voltage U min1 The upper limit voltage U max2 The bus voltage U max1 Between 0.8 and 1.

2.

6. A crane energy saving method according to claim 4 or 5, characterized in that: The operation modes of the crane energy-saving recovery system in step S3 include a maintenance mode and a working mode. In the maintenance mode, the high-voltage switch and the low-voltage switch are fixedly closed for device access maintenance; in the working mode, the high-voltage switch and the low-voltage switch are automatically opened and closed according to the detected voltage threshold.

7. A crane energy saving method according to claim 4 or 5, characterized in that: The switch unit in step S4 includes a high-voltage switch, and the closing logic is: when it is detected that the voltage across the nickel-hydrogen battery module (13) is ≥U max3 , the high-voltage switch is disconnected, otherwise the high-voltage switch is closed; the high-voltage control switch (151) disconnects the voltage U max3 Set to be less than the opening voltage U of the brake unit (2) max4 and is associated with the SOC upper limit state of the nickel-hydrogen battery module (13).

8. A crane energy saving method according to claim 6, characterized in that: The U max3 The SOC state association strategy of the nickel-hydrogen battery module (13) is: find the charging voltage value U corresponding to the upper limit SOC of the nickel-hydrogen battery module (13) charge-SOCx , at this time U max3 , U charge-SOCx Satisfy the relationship: U max3 ≈U charge-SOCx , the upper limit SOC range of the NiMH battery is set to 60%-80%.

9. A crane energy saving method according to claim 4 or 5, characterized in that: The switch unit in step S4 includes a low-voltage switch, and the closing logic is: when it is detected that the voltage across the nickel-hydrogen battery module (13) is ≤U min3 , the low-voltage switch is disconnected, otherwise the low-voltage switch is closed; the low-voltage switch disconnects the voltage U min3 The setting is greater than the inverter bus voltage U min1 and is associated with the SOC lower limit state of the nickel-hydrogen battery module (13).

10. A crane energy saving method according to claim 9, characterized in that: The U min3 The SOC state association strategy of the NiMH battery module is: find the discharge voltage value U corresponding to the lower limit SOC of the NiMH battery discharge-SOCx , at this time U min3 , U charge-SOCx Satisfy the relationship: U min3 ≈U discharge-SOCx , the lower limit SOC range of the nickel-hydrogen battery is set to 20%-40%.

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