Energy control method and energy control system of stacking machine

Abstract

The invention provides an energy control method of a stacker, which comprises the following steps: S10, monitoring the motion state of the stacker in real time, and judging whether one of charging and discharging conditions is met or not; if the judgment result in the step S10 is no, entering the step S20: controlling the stacker to obtain power from the power grid; if the judgment result in the step S10 is yes, entering the step S30: judging whether the stacking machine generates braking energy or not; if the judgment result in the step S30 is yes, the step S40 is executed, braking energy is calculated, and the super-capacitor unit is controlled to be charged in real time according to the braking energy so as to absorb the braking energy; if the judgment result in the step S30 is no, the step S50 is executed, the power obtained by the stacking machine from the power grid is limited to be the power grid limited power, the load gap energy of the stacking machine is calculated, and the super capacitor unit is controlled to discharge in real time according to the load gap energy so that the stacking machine can reach the load power. The energy control method can save energy and prevent impact on the power grid. The invention also provides an energy control system for realizing the method.

Description

Technical Field

[0001] This invention relates to the field of stacker crane technology, and in particular to an energy control method and energy control system for a stacker crane. Background Technology

[0002] Stacker cranes are the most important lifting and transport equipment in automated warehouses. They utilize frequency converters to achieve three movements: walking, lifting, and forking, ensuring flexible movement within the warehouse, accurate access to storage locations at different heights, and smooth forking of goods. During vertical descent and horizontal deceleration, stacker cranes generate braking energy. One current method for handling this braking energy is to convert it into heat dissipation using resistors, but this method results in significant energy waste. Another method is to use a bidirectional frequency converter to feed the braking energy back to the power grid. However, this method not only has higher hardware costs, but each feedback of braking energy also has a significant impact on the power grid, easily inducing harmonics. Summary of the Invention

[0003] The purpose of this invention is to provide an energy control method for a stacker crane that can save energy during operation and will not impact the power grid.

[0004] Another object of the present invention is to provide an energy control system for a stacker crane that can save energy during stacker crane operation and will not impact the power grid.

[0005] This invention provides an energy control method for a stacker crane, comprising:

[0006] S10: Real-time monitoring of the stacker crane's motion status to determine whether one of the charging / discharging conditions is met. The charging / discharging conditions include: the stacker crane's load power demand being greater than a preset grid power limit, and the stacker crane generating braking energy, which is the energy generated during the stacker crane's vertical descent or horizontal deceleration.

[0007] If the result of S10 is negative, proceed to S20: control the stacker crane to obtain power from the power grid;

[0008] If the result of S10 is yes, then proceed to S30: determine whether the stacker crane generates braking energy;

[0009] If the judgment result of S30 is yes, then proceed to S40: calculate the braking energy, and control the supercapacitor unit to charge in real time to absorb the braking energy based on the braking energy.

[0010] If the judgment result of S30 is negative, then proceed to S50: limit the power obtained by the stacker crane from the grid to the grid-limited power, calculate the load gap energy of the stacker crane, and control the supercapacitor unit to discharge in real time according to the load gap energy so that the stacker crane reaches the load power.

[0011] The energy control method for a stacker crane provided by this invention limits the power obtained by the stacker crane from the power grid to a grid-limited power level. When the stacker crane generates electrical energy, it charges a supercapacitor unit. When the stacker crane's load exceeds the grid-limited power level, the supercapacitor unit discharges to compensate for the load shortfall. Furthermore, during the charging and discharging process of the supercapacitor unit, the amount of electrical energy that the supercapacitor unit needs to store or release is calculated in real time, precisely controlling the charging and discharging of the supercapacitor unit to meet the stacker crane's needs. This energy control method saves energy for the stacker crane's operation, limits the power obtained by the stacker crane from the power grid, and avoids impacting the power grid.

[0012] In one illustrative embodiment of the energy control method for a stacker crane, S40 includes:

[0013] S41: Calculate braking energy based on the stacker crane's real-time kinetic energy and action commands;

[0014] S42: Monitors the real-time voltage value of the supercapacitor unit;

[0015] S43: Calculate the target charging voltage based on the braking energy and real-time voltage value; and

[0016] S44: Input the target charging voltage value into the first proportional-integral controller. The first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller, which controls the charging of the supercapacitor unit.

[0017] In another illustrative embodiment of the energy control method for a stacker crane, S50 includes:

[0018] S51: Limit the power that the stacker crane draws from the grid to the grid-limited power;

[0019] S52: Calculate the load gap energy of the stacker crane;

[0020] S53: Monitors the real-time voltage value of the supercapacitor unit;

[0021] S54: Calculate the target discharge voltage based on the load gap energy and real-time voltage value; and

[0022] S55: Input the target discharge voltage value into the first proportional-integral controller. The first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller, which controls the discharge of the supercapacitor unit.

[0023] In another illustrative embodiment of the energy control method for a stacker crane, S51 includes:

[0024] S511: Monitor the actual power absorbed by the stacker crane's rectifier unit from the power grid;

[0025] S512: Calculate the power difference between the actual power and the grid-limited power; and

[0026] S513: Input the differential power into the second proportional-integral controller. The second proportional-integral controller outputs a limiting current signal to the rectifier unit, which limits the power that the stacker crane obtains from the power grid.

[0027] In another illustrative embodiment of the energy control method for the stacker crane, in S513, the positive current limit of the current signal is 0, and the negative current limit is the maximum current of the rectifier unit. This prevents the supercapacitor unit from feeding power back to the grid and suppresses harmonics.

[0028] In another illustrative embodiment of the energy control method for a stacker crane, in steps S44 and S55, the first proportional-integral controller utilizes a voltage-current dual-loop control of a bidirectional DC-DC controller. This achieves precise energy control.

[0029] In another illustrative embodiment of the energy control method for a stacker crane, in steps S43 and S54, the target charging voltage and target discharging voltage are calculated using the following formulas:

[0030]

[0031] Where U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit.

[0032] In another illustrative embodiment of the energy control method for a stacker crane, the energy control method further includes:

[0033] Charge the supercapacitor unit before using the stacker crane; and

[0034] Discharge the supercapacitor unit before stacker crane maintenance.

[0035] By using the above steps, the supercapacitor unit is ensured to have electrical energy when the stacker crane is in use, and the supercapacitor unit is discharged during maintenance to improve safety.

[0036] The present invention also provides an energy control system for a stacker crane, comprising a DC bus, a rectifier unit, a bidirectional DC-DC controller, and a control unit. The DC bus is used to connect the stacker crane's frequency converter. The rectifier unit is used to connect the power grid and the DC bus to provide electrical energy. The bidirectional DC-DC controller is connected to the DC bus. The supercapacitor unit is connected to the bidirectional DC-DC controller and is capable of charging or discharging under the control of the bidirectional DC-DC controller. The control unit is configured to monitor the stacker crane's motion status in real time and determine whether one of the charging / discharging conditions is met. These conditions include the stacker crane's load power demand exceeding a preset grid power limit and the stacker crane generating braking energy, which is the energy generated during the stacker crane's vertical descent or horizontal deceleration. If the determination result is negative, the stacker crane is controlled to obtain power from the grid. If the determination result is positive, it is determined whether the stacker crane generates braking energy. If the determination result is positive, the braking energy is calculated, and the bidirectional DC-DC controller is controlled in real time to charge the supercapacitor unit to absorb the braking energy. If the determination result is negative, the power obtained by the stacker crane from the grid is limited to the grid power limit, the stacker crane's load deficit energy is calculated, and the bidirectional DC-DC controller is controlled in real time to discharge the supercapacitor unit so that the stacker crane reaches its load power.

[0037] In one illustrative embodiment of the energy control system of the stacker crane, the control unit includes a first proportional-integral controller. The control unit is configured to calculate braking energy based on the real-time kinetic energy and action commands of the stacker crane, monitor the real-time voltage value of the supercapacitor unit, calculate the charging target voltage value based on the braking energy and the real-time voltage value, input the charging target voltage value into the first proportional-integral controller, and output a PWM modulation signal to a bidirectional DC-DC controller to control the charging of the supercapacitor unit through the bidirectional DC-DC controller.

[0038] In another illustrative embodiment of the energy control system for the stacker crane, the control unit is configured to limit the power obtained by the stacker crane from the power grid to the grid-limited power, calculate the load gap energy of the stacker crane, monitor the real-time voltage value of the supercapacitor unit, calculate the discharge target voltage value based on the load gap energy and the real-time voltage value, input the discharge target voltage value to the first proportional-integral controller, the first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller, and controls the discharge of the supercapacitor unit through the bidirectional DC-DC controller.

[0039] In another illustrative embodiment of the energy control system of the stacker crane, the control unit includes a second proportional-integral controller. The control unit is configured to monitor the actual power absorbed by the rectifier unit of the stacker crane from the power grid, calculate the power difference between the actual power and the power limit imposed by the power grid, input the power difference into the second proportional-integral controller, and the second proportional-integral controller outputs a limiting current signal to the rectifier unit to limit the power obtained by the stacker crane from the power grid.

[0040] In another illustrative embodiment of the energy control system for the stacker crane, the positive current limit of the limiting current signal is 0, and the negative current limit is the maximum current of the rectifier unit.

[0041] In another illustrative embodiment of the energy control system for the stacker crane, the first proportional-integral controller utilizes a voltage-current dual-loop control bidirectional DC-DC controller.

[0042] In another illustrative embodiment of the stacker crane's energy control system, the control unit calculates the target charging voltage and target discharging voltage using the following formulas:

[0043]

[0044] Where U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit.

[0045] In another illustrative embodiment of the stacker crane's energy control system, the energy control system further includes a resistor unit connected to the DC bus, and the control unit is configured to control a bidirectional DC-DC controller, causing the resistor unit to consume the electrical energy stored in the supercapacitor unit. This allows the supercapacitor unit to be discharged when the stacker crane is not in operation. Attached Figure Description

[0046] The following figures are for illustrative purposes only and do not limit the scope of the invention.

[0047] Figure 1 This is a schematic flowchart illustrating one implementation of an energy control method for a stacker crane.

[0048] Figure 2 This is a power-time curve for the stacker crane.

[0049] Figure 3 This is a schematic diagram illustrating the implementation of the energy control method for a stacker crane.

[0050] Figure 4 This is a partial flowchart illustrating the energy control method for a stacker crane.

[0051] Figure 5 This is a partial flowchart illustrating the energy control method for a stacker crane.

[0052] Figure 6 This is a partial flowchart illustrating the energy control method for a stacker crane.

[0053] Label Explanation

[0054] 10 DC bus

[0055] 20 rectifier units

[0056] 30 bidirectional DC-DC controller

[0057] 40 supercapacitor units

[0058] 50 Control Unit

[0059] 60 resistor units

[0060] 70 frequency converter Detailed Implementation

[0061] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0062] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0063] In this document, "first" and "second" do not indicate their importance or order, but are only used to distinguish them to facilitate the description of the document.

[0064] To keep the drawings simple, each drawing only schematically shows the parts related to the present invention, and they do not represent the actual structure of the product.

[0065] Figure 1 This is a schematic flowchart illustrating one embodiment of an energy control method for a stacker crane. (Refer to...) Figure 1 The energy control methods include the following S10 to S50:

[0066] S10: Real-time monitoring of the stacker crane's motion status to determine whether one of the charging / discharging conditions is met. The charging / discharging conditions include: the stacker crane's load power demand is greater than a preset grid power limit, and the stacker crane generates braking energy, which is the energy generated when the stacker crane performs a vertical descent or horizontal deceleration action.

[0067] In this illustrative embodiment, the stacker crane's motion status is monitored via its frequency converter. The frequency converter records the stacker crane's real-time kinetic energy information and action command information. By processing this information, it can be determined whether the stacker crane has performed vertical descent and horizontal deceleration actions, and the load power of the stacker crane can be calculated to determine whether the charging and discharging conditions are met. However, this is not the only possible implementation. In other illustrative embodiments, the stacker crane's motion status can also be monitored by installing sensors.

[0068] If the judgment result of S10 is negative, then proceed to S20: control the stacker crane to obtain power from the power grid.

[0069] If the result of S10 is yes, then proceed to S30: determine whether the stacker crane generates braking energy. The purpose of S30 is to determine whether the stacker crane needs to be charged or discharged.

[0070] If the judgment result of S30 is yes, then proceed to S40: calculate the braking energy, and control the supercapacitor unit to charge in real time to absorb the braking energy based on the braking energy.

[0071] If the judgment result of S30 is negative, then proceed to S50: limit the power obtained by the stacker crane from the grid to the grid-limited power, calculate the load gap energy of the stacker crane, and control the supercapacitor unit to discharge in real time according to the load gap energy so that the stacker crane reaches the load power.

[0072] Figure 2 This is a power-time curve for the stacker crane. (Refer to...) Figure 2 S1 represents the curve of the stacker crane's load power changing over time, S2 represents the curve of the power the stacker crane draws from the grid changing over time, and S3 represents the curve of the supercapacitor unit's charging and discharging power changing over time. The energy control method limits the power the stacker crane draws from the grid to a grid-limited power. When the stacker crane generates electricity, it charges the supercapacitor unit. When the stacker crane's load exceeds the grid-limited power, the supercapacitor unit discharges to compensate for the load shortfall. Furthermore, during the charging and discharging process of the supercapacitor unit, the amount of electrical energy that the supercapacitor unit needs to store or release is calculated in real time, precisely controlling the charging and discharging of the supercapacitor unit to meet the stacker crane's needs. This energy control method saves energy for the stacker crane's operation and limits the power it draws from the grid, avoiding any impact on the grid.

[0073] Figure 3 This is a schematic diagram illustrating the implementation of the energy control method for a stacker crane. Figure 4 This is a partial flowchart illustrating the energy control method for a stacker crane. (Refer to...) Figure 3 and Figure 4 In the illustrative embodiment, S40 includes the following S41 to S44:

[0074] S41: Calculate braking energy based on the stacker crane's real-time kinetic energy and action commands.

[0075] S42: Monitor the real-time voltage value of the supercapacitor unit. This is achieved by the controller 50 reading information from the bidirectional DC-DC controller 30, which controls the charging or discharging of the supercapacitor unit 40.

[0076] S43: Calculate the target charging voltage value based on the braking energy and real-time voltage value.

[0077] S44: Input the target charging voltage value into the first proportional-integral controller. The first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller, which controls the charging of the supercapacitor unit.

[0078] In the illustrative embodiment, steps S41 to S44 are implemented by a controller 50, which includes a first proportional-integral controller 51. The controller 50 can read the real-time kinetic energy information and action command information of the stacker crane from the frequency converter 70, read the real-time voltage value of the supercapacitor unit 40 from the bidirectional DC-DC controller 30, and perform corresponding calculations based on the above information. During the discharge process of the supercapacitor unit 40, the first proportional-integral controller 51 uses a voltage-current dual-loop control of the bidirectional DC-DC controller 30 to achieve precise energy control.

[0079] Figure 5 This is a partial flowchart illustrating the energy control method for a stacker crane. (Refer to...) Figure 3 and Figure 5 In the illustrative embodiment, S50 includes the following S51 to S55:

[0080] S51: Limit the power that the stacker crane draws from the grid to the grid-limited power. Figure 6 This is a partial flowchart illustrating the energy control method for a stacker crane. (Refer to...) Figure 3 and Figure 6 In the illustrative embodiment, S51 includes the following S511 to S513:

[0081] S511: Monitors the actual power absorbed by the stacker crane's rectifier unit from the power grid.

[0082] S512: Calculate the power difference between the actual power and the grid-limited power.

[0083] S513: The differential power is input to the second proportional-integral controller, which outputs a current limiting signal to the rectifier unit. The rectifier unit then limits the power the stacker crane can draw from the grid. In an illustrative embodiment, the positive current limit of the current limiting signal is 0, and the negative current limit is the maximum current of the rectifier unit. This prevents the supercapacitor unit from feeding power back to the grid and suppresses harmonics.

[0084] S52: Calculate the load gap energy of the stacker crane.

[0085] S53: Monitors the real-time voltage value of the supercapacitor unit.

[0086] S54: Calculate the discharge target voltage value based on the load gap energy and the real-time voltage value.

[0087] S55: Input the target discharge voltage value into the first proportional-integral controller. The first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller, which controls the discharge of the supercapacitor unit.

[0088] In the illustrative embodiment, steps S51 to S55 are implemented by controller 50. Controller 50 can read the actual power from rectifier unit 20, read the real-time voltage value of supercapacitor unit 40 from bidirectional DC-DC controller 30, and perform corresponding calculations based on the above information. During the discharge process of supercapacitor unit 40, the first proportional-integral controller 51 uses a voltage-current dual-loop control of bidirectional DC-DC controller 30 to achieve precise energy control. Controller 50 also includes a second proportional-integral controller 52. When rectifier unit 20 absorbs power from the grid, the second proportional-integral controller 52 controls rectifier unit 20 to limit the power obtained by the stacker crane from the grid.

[0089] In the illustrative embodiment, in S43 and S54, the target charging voltage and target discharging voltage are calculated using the following formulas:

[0090]

[0091] Where U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit.

[0092] In an illustrative embodiment, the energy control method further includes:

[0093] Charge the supercapacitor unit before using the stacker crane. Ensure the supercapacitor unit has electrical energy when the stacker crane is in use.

[0094] Discharge the supercapacitor unit before stacker crane maintenance. Discharge the supercapacitor unit during maintenance to improve safety.

[0095] The present invention also provides an energy control system for a stacker crane. (See reference...) Figure 3 The energy control system includes a DC bus 10, a rectifier unit 20, a bidirectional DC-DC controller 30, and a control unit 50.

[0096] DC bus 10 is used to connect the stacker crane's frequency converter. Rectifier unit 20 is used to connect the power grid and DC bus 10 to provide electrical energy. Bidirectional DC-DC controller 30 is connected to DC bus 10. Supercapacitor unit 40 includes several supercapacitors, which are connected to bidirectional DC-DC controller 30 and can be charged or discharged under the control of bidirectional DC-DC controller 30.

[0097] The control unit 50 is configured to monitor the movement status of the stacker crane in real time and determine whether one of the charging and discharging conditions is met. The charging and discharging conditions include: the load power demand of the stacker crane is greater than a preset grid power limit, and the stacker crane generates braking energy. The braking energy is the energy generated when the stacker crane performs a vertical descent or horizontal deceleration. If the determination result is negative, the stacker crane is controlled to obtain power from the grid. If the determination result is positive, it is determined whether the stacker crane generates braking energy. If the determination result is positive, the braking energy is calculated, and the bidirectional DC-DC controller 30 is controlled in real time to charge the supercapacitor unit 40 to absorb the braking energy. If the determination result is negative, the power obtained by the stacker crane from the grid is limited to the grid power limit, the load gap energy of the stacker crane is calculated, and the bidirectional DC-DC controller 30 is controlled in real time to discharge the supercapacitor unit 40 so that the stacker crane reaches the load power.

[0098] In the illustrative embodiment, refer to Figure 3 The control unit 50 includes a first proportional-integral controller 51. The control unit 50 is configured to calculate braking energy based on the real-time kinetic energy and action commands of the stacker crane, monitor the real-time voltage value of the supercapacitor unit 40, calculate the charging target voltage value based on the braking energy and the real-time voltage value, input the charging target voltage value into the first proportional-integral controller 51, and output a PWM modulation signal to the bidirectional DC-DC controller 30 to control the charging of the supercapacitor unit 40 through the bidirectional DC-DC controller 30.

[0099] In the illustrative embodiment, refer to Figure 3The control unit 50 is configured to limit the power obtained by the stacker crane from the power grid to the power grid limit, calculate the load gap energy of the stacker crane, monitor the real-time voltage value of the supercapacitor unit 40, calculate the discharge target voltage value based on the load gap energy and the real-time voltage value, and input the discharge target voltage value into the first proportional-integral controller 51. The first proportional-integral controller 51 outputs a PWM modulation signal to the bidirectional DC-DC controller 30, and controls the supercapacitor unit 40 to discharge through the bidirectional DC-DC controller 30.

[0100] In an illustrative embodiment, the first proportional-integral controller 51 utilizes a voltage-current dual-loop control to regulate the bidirectional DC-DC controller 30. This enables precise energy control.

[0101] In an illustrative embodiment, the control unit 50 calculates the target charging voltage and target discharging voltage using the following formulas:

[0102]

[0103] Where U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit.

[0104] In the illustrative embodiment, refer to Figure 3 The control unit 50 includes a second proportional-integral controller 52. The control unit 50 is configured to monitor the actual power absorbed by the stacker crane's rectifier unit from the grid, calculate the power difference between the actual power and the grid-limited power, and input this power difference into the second proportional-integral controller 52. The second proportional-integral controller 52 outputs a limiting current signal to the rectifier unit, thereby limiting the power obtained by the stacker crane from the grid. Specifically, the positive current limit of the limiting current signal is 0, and the negative current limit is the maximum current of the rectifier unit 20. This prevents the supercapacitor unit from feeding power back to the grid and suppresses harmonics.

[0105] In the illustrative embodiment, refer to Figure 3 The energy control system also includes a resistor unit 60 connected to the DC bus 10. The control unit 50 is configured to control the bidirectional DC-DC controller 30, causing the resistor unit 60 to consume the electrical energy stored in the supercapacitor unit 40. This allows the supercapacitor unit to be discharged when the stacker crane is not in operation.

[0106] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0107] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. An energy control method for a stacker crane, characterized in that, include: S10: Monitor the stacker crane's movement status in real time and determine whether one of the charging / discharging conditions is met. The charging / discharging conditions include: the stacker crane's load power demand exceeding a preset grid power limit, and... The stacker crane generates braking energy, which is the energy generated when the stacker crane performs a vertical descent or horizontal deceleration action. If the result of S10 is negative, proceed to S20: control the stacker crane to obtain power from the power grid; If the judgment result of S10 is yes, then proceed to S30: determine whether the stacker crane generates the braking energy; If the judgment result of S30 is yes, then proceed to S40: calculate the braking energy, and control the supercapacitor unit to charge in real time to absorb the braking energy based on the braking energy; If the judgment result of S30 is negative, then proceed to S50: limit the power obtained by the stacker crane from the power grid to the power grid limit, calculate the load gap energy of the stacker crane, and control the supercapacitor unit to discharge in real time according to the load gap energy so that the stacker crane reaches the load power.

2. The energy control method for a stacker crane as described in claim 1, characterized in that, S40 includes: S41: Calculate the braking energy based on the stacker crane's real-time kinetic energy and action commands; S42: Monitor the real-time voltage value of the supercapacitor unit; S43: Calculate the target charging voltage value based on the braking energy and the real-time voltage value; and S44: Input the target charging voltage value into the first proportional-integral controller, and the first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller to control the charging of the supercapacitor unit.

3. The energy control method for a stacker crane as described in claim 2, characterized in that, The S50 includes: S51: Limit the power obtained by the stacker crane from the power grid to the power grid limit; S52: Calculate the load gap energy of the stacker crane; S53: Monitor the real-time voltage value of the supercapacitor unit; S54: Calculate the discharge target voltage value based on the load gap energy and the real-time voltage value; and S55: The target discharge voltage value is input to the first proportional-integral controller, and the first proportional-integral controller outputs a PWM modulation signal to the bidirectional DC-DC controller to control the discharge of the supercapacitor unit.

4. The energy control method for a stacker crane as described in claim 3, characterized in that, S51 includes: S511: Monitor the actual power absorbed by the stacker crane's rectifier unit from the power grid; S512: Calculate the power difference between the actual power and the grid-limited power; and S513: The differential power is input to the second proportional-integral controller, and the second proportional-integral controller outputs a limiting current signal to the rectifier unit to limit the power obtained by the stacker crane from the power grid.

5. The energy control method for a stacker crane as described in claim 4, characterized in that, In S513, the positive current limit of the current limiting signal is 0, and the negative current limit is the maximum current of the rectifier unit.

6. The energy control method for a stacker crane as described in claim 3, characterized in that, In S44 and S55, the first proportional-integral controller uses a voltage-current dual-loop control to control the bidirectional DC-DC controller.

7. The energy control method for a stacker crane as described in claim 3, characterized in that, In S43 and S54, the target charging voltage and the target discharging voltage are calculated using the following formulas: Where U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit.

8. The energy control method for a stacker crane as described in claim 1, characterized in that, The energy control method further includes: charging the supercapacitor unit before using the stacker crane; and Discharge the supercapacitor unit before the stacker crane is overhauled.

9. The energy control system of a stacker crane, characterized in that, include: A DC bus (10) is used to connect the frequency converter of the stacker crane; A rectifier unit (20) is used to connect the power grid and the DC bus (10) to provide electrical energy; A bidirectional DC-DC controller (30) is connected to the DC bus (10); as well as A supercapacitor unit (40) is connected to the bidirectional DC-DC controller (30) and is capable of charging or discharging under the control of the bidirectional DC-DC controller (30); A control unit (50) is configured to monitor the movement state of the stacker crane in real time and determine whether one of the charging and discharging conditions is met, the charging and discharging conditions including the stacker crane's load power demand being greater than a preset grid limit power and the stacker crane generating braking energy, the braking energy being the energy generated when the stacker crane makes a vertical descent or horizontal deceleration action. If the determination result is negative, the stacker crane is controlled to obtain power from the grid. If the determination result is positive, it is determined whether the stacker crane generates the braking energy. If the determination result is positive, the braking energy is calculated, and the bidirectional DC-DC controller (30) is controlled in real time according to the braking energy to charge the supercapacitor unit (40) to absorb the braking energy. If the determination result is negative, the power obtained by the stacker crane from the grid is limited to the grid limit power, the load gap energy of the stacker crane is calculated, and the bidirectional DC-DC controller (30) is controlled in real time according to the load gap energy to discharge the supercapacitor unit (40) so that the stacker crane reaches the load power.

10. The energy control system of the stacker crane as described in claim 9, characterized in that, The control unit (50) includes a first proportional-integral controller (51). The control unit (50) is configured to calculate the braking energy based on the real-time kinetic energy and action commands of the stacker crane, monitor the real-time voltage value of the supercapacitor unit (40), calculate the charging target voltage value based on the braking energy and the real-time voltage value, and input the charging target voltage value into the first proportional-integral controller (51). The first proportional-integral controller (51) outputs a PWM modulation signal to the bidirectional DC-DC controller (30) to control the charging of the supercapacitor unit (40) through the bidirectional DC-DC controller (30).

11. The energy control system of the stacker crane as described in claim 10, characterized in that, The control unit (50) is configured to limit the power obtained by the stacker from the power grid to the power grid limit, calculate the load gap energy of the stacker, monitor the real-time voltage value of the supercapacitor unit (40), calculate the discharge target voltage value based on the load gap energy and the real-time voltage value, input the discharge target voltage value into the first proportional-integral controller (51), the first proportional-integral controller (51) outputs a PWM modulation signal to the bidirectional DC-DC controller (30), and controls the supercapacitor unit (40) to discharge through the bidirectional DC-DC controller (30).

12. The energy control system of the stacker crane as described in claim 11, characterized in that, The control unit (50) includes a second proportional-integral controller (52). The control unit (50) is configured to monitor the actual power absorbed by the rectifier unit of the stacker crane from the power grid, calculate the difference power between the actual power and the power grid limit, and input the difference power into the second proportional-integral controller (52). The second proportional-integral controller (52) outputs a limit current signal to the rectifier unit, thereby limiting the power obtained by the stacker crane from the power grid through the rectifier unit (20).

13. The energy control system of the stacker crane as described in claim 12, characterized in that, The positive current limit of the current limiting signal is 0, and the negative current limit is the maximum current of the rectifier unit (20).

14. The energy control system of the stacker crane as described in claim 11, characterized in that, The first proportional-integral controller (51) uses a voltage-current dual-loop control to control the bidirectional DC-DC controller (30).

15. The energy control system of the stacker crane as described in claim 11, characterized in that, The control unit (50) calculates the target charging voltage and the target discharging voltage using the following formulas: Wherein, U2 is the target charging voltage or target discharging voltage, Q is the braking energy or load gap energy, C is the capacitance, and U1 is the real-time voltage of the supercapacitor unit (40).

16. The energy control system of the stacker crane as described in claim 9, characterized in that, The energy control system further includes a resistor unit (60) connected to the DC bus (10), and the control unit (50) is configured to control the bidirectional DC-DC controller (30) so that the resistor unit (60) consumes the electrical energy stored in the supercapacitor unit (40).

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