Port electromagnetic crane and regenerative energy recovery and recycling method and application

Abstract

The present invention discloses a port electromagnetic crane and a method and application for recycling and utilizing regenerative energy. This solution cleverly monitors the voltage changes of the common DC bus between the variable frequency motor and the frequency converter to determine in real time whether the variable frequency motor is in the electric state or the power generation state. At the same time, this solution also monitors the state of the energy storage unit and uses the energy storage unit to charge and discharge the auxiliary motor to avoid its negative impact on the system circuit. This solution switches the working state of the energy storage unit to different states through the energy manager based on the motor state information and the energy storage state information of the energy storage unit. This solution can be applied to the working control method of the port electromagnetic crane to realize energy recovery and reuse when the crane's lifting motor is working. At the same time, because the regenerative energy generated by the lifting motor is not fed back to the power grid, it will not cause impact on the power grid and will not cause pollution problems such as harmonics and flicker to the power grid.

Description

Technical Field

[0001] The present invention relates to the fields of energy storage technology and port crane operation control technology, and in particular to a port electromagnetic crane and a regenerative energy recovery and recycling method and application. Background Art

[0002] Cranes are common transfer equipment in ports and docks. They are widely used due to their strong transfer capacity and stable operation. Hoisting motors are common working parts of cranes and undertake important transfer work. Due to the special working characteristics of hoisting motors, the use of variable frequency motors as hoisting motors has become a more widely used technology.

[0003] With the development and widespread application of variable frequency speed regulation technology, AC variable frequency speed regulation is now the predominant speed regulation solution for electrical transmissions in port machinery. When a port crane's hoisting motor assembly is operating during loading and unloading operations, regenerative energy is generated. This regenerative energy is primarily due to two types: inertia generated by frequent braking of the various mechanisms, and potential energy generated by the lowering of cargo within the lifting mechanism. Due to the inertia or potential energy of the hoisting motor associated with the mechanism, the motor's speed exceeds the speed corresponding to the inverter's output frequency. This regenerative energy is fed back to the inverter's DC-side filter capacitor, generating a pump-up voltage. Excessively high pump-up voltage can damage switching components, electrolytic capacitors, and even the motor's insulation, threatening system safety. Therefore, this regenerative energy must be managed. Conventional methods for managing regenerative energy include energy dissipation and energy regeneration. Energy dissipation involves adding a discharge resistor unit to the inverter's DC side. This regenerative energy is dissipated in a power resistor through a specialized energy-dissipating braking circuit, converting the regenerative energy into heat. This is known as resistance braking. To ensure safe system operation, this electrical energy is wasted as heat by the resistors, a solution used in traditional crane frequency conversion system control. Furthermore, energy regeneration is achieved by adding a regenerative device to make the inverter on the grid side of the inverter reversible, allowing the regenerated electrical energy to be recycled locally to the grid, thus compensating for the loss of electrical energy. This energy regeneration method requires resolving the following technical challenges:

[0004] (1) The feedback energy of the hoisting motor during braking is a shock source to the power grid, affecting the operation of the power grid. At the same time, it will produce more harmonics, flicker and other pollution problems. It is necessary to use corresponding filtering devices to control the harmonics;

[0005] (2) For lines with distributed power generation systems, since current flows in both directions between the power grid and the distributed system, the reverse flow of electric energy to the power grid will cause voltage fluctuations in the power grid and increase the short-circuit current of the power grid, posing a safety hazard to the use of electrical components in surrounding equipment;

[0006] (3) For the user unit, the electric energy fed back to the grid can be measured, but there is a possibility that only part of the fed-back electric energy can be reused, that is, the fed-back electric energy cannot be fully utilized by the user unit, and the amount of electric energy reused by a single device is difficult to accurately calculate.

[0007] To sum up, there are certain technical difficulties in recovering and utilizing the regenerative energy of the hoisting motor of the crane using a variable frequency motor. How to recover and recycle the regenerative energy is an important issue for improving the energy efficiency of the crane and protecting the reliability of the system. If the logic of regenerative energy recovery and recycling can be optimized and technical transformation can be carried out, it will have positive practical significance for the optimization of the crane's operation. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to propose a port electromagnetic crane and a method and application for recycling and regenerating energy. This solution is reliable in implementation and flexible in application, and can ensure the stability and safety of the crane's working circuit when recovering and recycling the regenerated energy generated by the crane's hoisting motor (variable frequency motor).

[0009] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0010] A method for recycling and utilizing regenerative energy is disclosed, which is used for recycling and utilizing regenerative energy during operation of a variable frequency motor. The variable frequency motor is electrically connected to a frequency converter, which is connected to a power grid to input electrical energy for driving the variable frequency motor. A common DC bus is provided on the circuit connecting the frequency converter and the variable frequency motor. An energy manager is connected to the common DC bus, and the energy manager is connected to an energy storage unit. The method comprises:

[0011] S01. Collect voltage data of a common DC bus to which the variable frequency motor is connected in real time to generate voltage monitoring data;

[0012] S02. Determine the working state of the variable frequency motor according to the voltage monitoring data and preset conditions, and generate motor state information;

[0013] S03. The energy manager collects parameters of the energy storage unit at a preset time frequency and generates energy storage status information according to preset conditions;

[0014] S04. Based on the motor status information and the energy storage status information of the energy storage unit, the energy manager switches the working state of the energy storage unit to a first state, a second state, or a third state. In the first state, the energy manager controls the energy storage unit to be connected to the public DC bus to introduce the regenerative energy generated by the variable frequency motor for charging. In the second state, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the public DC bus to assist the operation of the variable frequency motor. In the third state, the energy manager controls the energy storage unit to maintain the electrical connection with the public DC bus interrupted.

[0015] As a possible implementation method, further, the frequency converter described in this scheme includes a rectifier, an inverter and a braking unit. The rectifier is connected to the power grid to input electric energy for driving the variable frequency motor. The inverter is electrically connected to the rectifier and the variable frequency motor respectively to supply the electric energy input by the rectifier to the variable frequency motor. The braking unit is connected to the circuit between the rectifier and the inverter. The braking unit is also connected to a braking resistor. The braking resistor is used to feed back the regenerative energy on the common DC bus for consumption when the variable frequency motor is in a power generation state.

[0016] As a possible implementation method, further, the energy storage unit described in this solution includes a capacitor management module and at least one supercapacitor; the energy manager includes a bidirectional DC-DC driver and a PLC module, the PLC module is electrically connected to the bidirectional DC-DC driver, and the working state of the bidirectional DC-DC driver is controlled by the PLC module. The bidirectional DC-DC driver is also electrically connected to at least one supercapacitor, and the capacitor management module is electrically connected to the PLC module and at least one supercapacitor, and is used to obtain parameters of at least one supercapacitor according to a preset time frequency and pass it to the PLC module to generate energy storage status information.

[0017] As a preferred implementation option, preferably, in this solution S01, the voltage monitoring data are all associated with the time point at which they were collected.

[0018] Based on the above, as a better implementation option, preferably, this solution S02 includes:

[0019] S021, collect the voltage monitoring data within the preset time period in time series, and calculate the voltage monitoring data and the preset reference voltage according to the voltage monitoring data. The difference and voltage change rate ;

[0020] S022. Determine the difference at the same time point t and voltage change rate ,when or , and the voltage change rate or When t is reached, the working state of the variable frequency motor at that time point t is defined as the electric state, and the definition time of the working state is recorded at the same time;

[0021] when , and the voltage change rate or voltage change rate When t is reached, the working state of the variable frequency motor at this time point t is defined as the power generation state, and the definition time of the working state is recorded at the same time, where, Set a threshold for the voltage change rate;

[0022] S023. Obtain the working state definition of the variable frequency motor and generate motor state information.

[0023] As a preferred implementation option, preferably, this solution S023 also includes:

[0024] Obtain the working state definition of the variable frequency motor. When it points to the time point t when the variable frequency motor is in the power generation state, obtain the working state definition of the variable frequency motor in the time period T before the time point t according to the preset time window T. When the working state definition of the variable frequency motor in the time period T is all the power generation state, generate the power generation state as the motor state information. When the working state definition includes the electric state, generate the electric state as the motor state information. The working state definition and motor state information corresponding to the variable frequency motor at the time point t are recorded separately and are associated with each other.

[0025] Based on the above, this solution also provides a port electromagnetic crane operation control method, which includes the above-mentioned regenerative energy recovery and recycling method; wherein the variable frequency motor is a hoisting motor of the port electromagnetic crane; the operation control method includes: responding to a start signal of the electromagnetic crane, executing S01 to S04; and further includes one of the following:

[0026] (1) Establish a mathematical model for the energy fluctuation of variable frequency motors, smooth the energy fluctuations through energy storage units, and optimize energy scheduling according to preset strategies;

[0027] (2) According to the energy storage status information of the energy storage unit, the charge and discharge distribution of the energy storage unit is adjusted to balance the load of each sub-unit in the energy storage unit.

[0028] As a preferred implementation option, this solution preferably establishes a mathematical model for energy fluctuations of variable frequency motors, smoothes energy fluctuations through energy storage units, and optimizes energy scheduling according to a preset strategy, including:

[0029] A01. Establish a mathematical model of energy fluctuation. Based on the fact that the regenerative energy of the electromagnetic crane using a variable frequency motor is a time-varying process, it is assumed that the regenerative power is a function of time t and is defined as follows:

[0030] ;

[0031] in, is the electric power regenerated by the hoisting motor, in watts; is the mechanical-electrical conversion efficiency of the motor, It is the power converted from the mechanical energy of the motor;

[0032] Based on mechanical power Hoisting speed of the crane's hoisting motor and load force Related, it is expressed as follows:

[0033] ;

[0034] in, , is the load force, is the weight of the cargo, is the acceleration; is the lifting speed in meters per second;

[0035] By monitoring the mass and descent speed of the load, the electric power regenerated by the lifting motor is calculated in real time ;

[0036] A02. The energy storage unit is used to absorb the regenerative energy fluctuation and release the energy to the system in a timely manner. Assuming that the storage capacity of the energy storage unit is , and its relationship with time is expressed as follows:

[0037] ;

[0038] in, is the energy in the energy storage unit, its unit is joule, It is the power of regenerative electricity, that is, the power regenerated by the lifting motor. is the electrical power consumed by the system;

[0039] According to the storage capacity of the energy storage unit The relationship between the energy storage unit's upper limit and its charging and discharging is managed, including the following:

[0040] when = Energy storage limit of the energy storage unit When , the energy storage unit stops charging;

[0041] when Less than the lower limit of energy storage unit When , the energy storage unit stops discharging and enters the charging standby state;

[0042] By switching between charging and discharging, the energy storage unit smoothes the fluctuation of the regenerative energy generated by the hoisting motor and recovers the energy for timely release.

[0043] A03. In addition to the energy storage unit, the excess regenerative energy is fed back to the grid or used for other energy-consuming devices through the energy feedback system. The power conditioner is used in the circuit to transmit the excess regenerative energy to the grid. It is expressed as follows:

[0044] ;

[0045] in, For feedback power, The power of regenerative energy, The power that the energy storage unit can absorb after charging, is the current load demand of the electromagnetic crane, when When , it means that the regenerative energy generated by the hoisting motor can be fed back to the grid. When , it means that the system needs to obtain energy from the grid;

[0046] A04. Energy management is used to dispatch regenerative energy and loads to dynamically adjust the charging and discharging of energy storage units and grid feedback, including:

[0047] when Greater than When the energy storage unit is connected to the common DC bus, the energy manager controls the energy storage unit to be charged by introducing the regenerative energy generated by the hoisting motor;

[0048] When the energy storage unit is fully loaded, and When the energy manager controls the energy storage unit to maintain the electrical connection with the common DC bus interrupted;

[0049] When the system load requires more energy, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the common DC bus to assist the variable frequency motor in operating.

[0050] As a preferred implementation option, preferably, this solution adjusts the charge and discharge distribution of the energy storage unit according to the energy storage status information of the energy storage unit to balance the load of each sub-unit in the energy storage unit, including:

[0051] B01. When the energy storage unit is composed of multiple supercapacitors, the storage capacity of each supercapacitor is defined as follows:

[0052] The first i Energy storage of supercapacitors The voltage across the capacitor and capacitance value It is expressed as follows:

[0053] ;

[0054] in, It is i The energy stored in a supercapacitor at time t, in joules; It is i The capacitance value of a supercapacitor, in farads; It is i The voltage of a supercapacitor at time t, in volts;

[0055] Assuming that the energy storage unit has N supercapacitors that can be configured, the total system energy storage capacity is It is expressed as follows:

[0056] ;

[0057] B02. Assign charging priority to N supercapacitors. Assume that the charging power of each supercapacitor is Affected by its current voltage and the regenerative energy provided by the system Impact, the charging power is defined as:

[0058] ;

[0059] in, is the charging efficiency, which is between 0-1, is the current regenerative energy input power of the system, is the maximum charging voltage of the supercapacitor; The charging power of each supercapacitor is is the current voltage of the supercapacitor;

[0060] The formula shows that the supercapacitor with lower voltage will get more charging power first because the current voltage of the supercapacitor is Distance maximum voltage The farther away it is, the more energy it is allocated;

[0061] In order to prevent the supercapacitor from overcharging, the charging state of each supercapacitor is controlled by a threshold value, and the maximum acceptable voltage of each supercapacitor is defined. , once the current voltage of the supercapacitor Reached the maximum acceptable voltage , then the supercapacitor stops charging, and its strategy is described as follows:

[0062] when When the charging power is allocated according to the priority level,

[0063] when When the supercapacitor stops charging, the remaining regenerative energy is distributed to other supercapacitors.

[0064] B03. Assign discharge priorities to N supercapacitors. Assume that the output power requirement of the system is , the discharge power of each supercapacitor is , which is defined as follows:

[0065] ;

[0066] in, is the discharge efficiency, is the discharge power of each supercapacitor, is the current voltage of the supercapacitor, is the output power requirement of the system;

[0067] This formula strategy shows that supercapacitors with higher voltages are discharged first to provide more stable output power;

[0068] In order to prevent the supercapacitor from over-discharging, the discharge state of each supercapacitor is controlled by a threshold value and the minimum discharge voltage is set. ;

[0069] when When , the supercapacitor continues to discharge;

[0070] when When , the supercapacitor stops discharging;

[0071] B04. Dynamically adjusting the charging and discharging sequence of the N supercapacitors of the energy storage unit through the energy manager;

[0072] In terms of charging priority adjustment, the voltage of all supercapacitors is calculated in real time, and the charging priority of supercapacitors with lower voltage is increased. At the same time, it is ensured that the voltage of each supercapacitor does not exceed the maximum acceptable voltage. ;

[0073] In terms of discharge priority adjustment, when the system load increases, the supercapacitors with higher voltages are given priority to supply energy. At the same time, the voltage of each supercapacitor is ensured not to be lower than the minimum discharge voltage. ;

[0074] The energy manager distributes energy among the N supercapacitors of the energy storage unit using a dynamic programming algorithm, allowing the system to optimize the charging and discharging sequence at each time step t to minimize energy loss and efficiency degradation. Its objective function is defined as follows:

[0075] ;

[0076] in, is charging efficiency; The charging power of each supercapacitor is is the discharge efficiency, is the discharge power of each supercapacitor.

[0077] As a preferred implementation option, preferably, this solution adjusts the charge and discharge distribution of the energy storage unit to balance the load of each sub-unit in the energy storage unit and further includes: optimizing the distribution of the charging rate of the supercapacitor and optimizing the distribution of the discharge of the supercapacitor;

[0078] The optimization of supercapacitor charging rate distribution includes:

[0079] Introducing the partition coefficient , which is used to adjust the charging rate of each supercapacitor. Its corresponding charging power is defined as follows:

[0080] ;

[0081] In the above formula, To allocate to i The charging power of a supercapacitor, is the total regenerative energy power of the system, For the i The dynamic allocation coefficient of the supercapacitor satisfies ;

[0082] The corresponding distribution coefficient of the supercapacitor according to its voltage state Dynamic adjustment is performed, and the formula is defined as follows:

[0083] ;

[0084] in, It is i The charge distribution coefficient of a supercapacitor at time t is, is the maximum allowable charging voltage of the supercapacitor, is the current voltage of the supercapacitor at time t, It is the combined charging demand of N supercapacitors, which represents the total remaining charge of N supercapacitors in the system;

[0085] Optimizing the distribution of supercapacitor discharge includes:

[0086] Introducing the partition coefficient , which is used to adjust the discharge rate of each supercapacitor. Its corresponding discharge power is defined as follows:

[0087] ;

[0088] In the above formula, To allocate to i The discharge power of a supercapacitor, is the current load demand of the system, For the i The dynamic distribution coefficient of a supercapacitor, that is, the discharge distribution coefficient,

[0089] Its satisfaction ;

[0090] The corresponding distribution coefficient of the supercapacitor according to its voltage state Dynamic adjustment is performed, and the formula is defined as follows:

[0091] ;

[0092] in, It is i The discharge distribution coefficient of a supercapacitor at time t is, is the current voltage of the supercapacitor at time t, is the sum of the voltages of the N supercapacitors, which represents the sum of the voltages of the N supercapacitors in the system;

[0093] The energy manager dynamically adjusts control inputs based on future system predictions to optimize system performance. The control goal is to minimize energy loss and optimize energy utilization during charging and discharging. Its objective function is defined as follows:

[0094] ;

[0095] in, is charging efficiency; The charging power of each supercapacitor is is the discharge efficiency, is the discharge power of each supercapacitor.

[0096] Based on the above, this solution also provides a method for recycling the regenerative energy of a port crane variable frequency motor, which is applied to the above-mentioned regenerative energy recovery and recycling method or the above-mentioned port electromagnetic crane operation control method.

[0097] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: the present solution cleverly monitors the voltage change of the common DC bus between the variable frequency motor and the inverter to judge in real time whether the variable frequency motor is in the electric state or the power generation state. At the same time, the present solution also monitors the state of the energy storage unit and uses the energy storage unit to charge and discharge the auxiliary motor to avoid its negative impact on the system circuit. The present solution switches the working state of the energy storage unit to the first state, the second state or the third state through the energy manager based on the motor state information and the energy storage state information of the energy storage unit. In the first state, the energy manager controls the energy storage unit to be connected to the common DC bus to introduce the regenerative energy generated by the variable frequency motor for charging; in the second ... The manager controls the electric energy stored in the energy storage unit to be supplied to a common DC bus to assist the operation of the variable frequency motor. In the third state, the energy manager controls the energy storage unit to maintain the disconnection of the electrical connection with the common DC bus. This solution can be applied to the operation control method of a port electromagnetic crane to realize energy recovery and reuse when the crane's hoisting motor is in operation. At the same time, because the regenerative energy generated by the hoisting motor is not fed back to the power grid, the regenerative electric energy will not cause an impact on the power grid when it is recovered, and will not cause pollution problems such as harmonics and flicker to the power grid. On the contrary, the stored energy is released during the accelerated start-up process of the port electromagnetic crane's hoisting motor, which can reduce the impact of the motor on the power grid, reduce the effect of the instantaneous drop in the power grid voltage (especially when a high-power motor is operating), and improve the quality of power grid use. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0099] Figure 1 This is a brief implementation flow diagram of the renewable energy recovery and recycling method of this scheme;

[0100] Figure 2 This is a simplified system schematic diagram of the connections between the inverter and the variable frequency motor and other components in the regenerative energy recovery and recycling method of this scheme;

[0101] Figure 3 This is a simplified system circuit schematic diagram of the connections between the inverter, variable frequency motor and other components in the regenerative energy recovery and recycling method of this scheme. DETAILED DESCRIPTION

[0102] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0103] Combine Figure 1 As shown, this solution provides a method for recycling and utilizing regenerative energy, which is used for recycling and utilizing regenerative energy when a variable frequency motor is in operation. The variable frequency motor is electrically connected to a frequency converter, which is connected to a power grid to input electrical energy for driving the variable frequency motor. A common DC bus is provided on the circuit connecting the frequency converter and the variable frequency motor. An energy manager is connected to the common DC bus, and the energy manager is connected to an energy storage unit. The method includes:

[0104] S01. Collect voltage data of a common DC bus to which the variable frequency motor is connected in real time to generate voltage monitoring data;

[0105] S02. Determine the working state of the variable frequency motor according to the voltage monitoring data and preset conditions, and generate motor state information;

[0106] S03. The energy manager collects parameters of the energy storage unit at a preset time frequency and generates energy storage status information according to preset conditions;

[0107] S04. Switching the working state of the energy storage unit to the first state, the second state, or the third state through the energy manager according to the motor state information and the energy storage state information of the energy storage unit;

[0108] In the first state, the energy manager controls the energy storage unit to be connected to the common DC bus to introduce the regenerative energy generated by the variable frequency motor for charging;

[0109] In the second state, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the common DC bus to assist the operation of the variable frequency motor;

[0110] In the third state, the energy manager controls the energy storage unit to maintain an electrical disconnection with the common DC bus.

[0111] Combine Figure 2 、 Figure 3As shown, as a possible implementation of the frequency converter, further, the frequency converter described in this solution includes a rectifier, an inverter and a brake unit, the rectifier is connected to the power grid to input electric energy for driving the variable frequency motor, the inverter is electrically connected to the rectifier and the variable frequency motor respectively, so as to supply the electric energy input by the rectifier to the variable frequency motor, the brake unit is connected to the circuit between the rectifier and the inverter, and the brake unit is further connected to a brake resistor, which is used to feed back the regenerative energy on the common DC bus for consumption when the variable frequency motor is in a power generation state; In the first step, the energy storage unit described in this solution includes a capacitance management module and at least one supercapacitor; the energy manager includes a bidirectional DC-DC driver and a PLC module, the PLC module is electrically connected to the bidirectional DC-DC driver, and the working state of the bidirectional DC-DC driver is controlled by the PLC module. The bidirectional DC-DC driver is also electrically connected to the at least one supercapacitor, and the capacitance management module is electrically connected to the PLC module and the at least one supercapacitor, and is used to obtain parameters of the at least one supercapacitor at a preset time frequency and transmit them to the PLC module to generate energy storage status information.

[0112] In order to improve the time consistency of data monitoring and processing, as a better implementation option, preferably, in this solution S01, the voltage monitoring data are all associated with the time point at which they are collected.

[0113] In this solution, the working state of the variable frequency motor is determined according to the change of the voltage monitoring data. In order to improve the reliability and accuracy of the detection, based on the above, as a preferred implementation option, preferably, this solution S02 includes:

[0114] S021, collect the voltage monitoring data within the preset time period in time series, and calculate the voltage monitoring data and the preset reference voltage according to the voltage monitoring data. The difference and voltage change rate ;

[0115] S022. Determine the difference at the same time point t and voltage change rate ;

[0116] when or , and the voltage change rate or When t is reached, the working state of the variable frequency motor at that time point t is defined as the electric state, and the definition time of the working state is recorded at the same time;

[0117] when , and the voltage change rate or voltage change rate When t is reached, the working state of the variable frequency motor at this time point t is defined as the power generation state, and the definition time of the working state is recorded at the same time, where, Set a threshold for the voltage change rate;

[0118] S023: Obtain the working state definition of the variable frequency motor and generate motor state information, that is, correspond the working state definition of the variable frequency motor to the motor state information.

[0119] Since the time that the variable frequency motor is in the charging state fluctuates, in order to avoid the energy manager sending high-frequency switching when the variable frequency motor is in the charging state for too short a time, the variable frequency motor can be ignored in a timely manner when it is in the generating state for a short time, so as to avoid the energy storage unit frequently switching to the charging state in a short time. As a preferred implementation option, preferably, this solution S023 also includes:

[0120] Obtain the working state definition of the variable frequency motor. When it points to the time point t when the variable frequency motor is in the power generation state, obtain the working state definition of the variable frequency motor in the time period T before the time point t according to the preset time window T;

[0121] When the working state definition of the variable frequency motor in the time period T is all the power generation state, the power generation state is generated as the motor state information;

[0122] When the working state definition includes the electric state, the electric state is generated as the motor state information; wherein the working state definition and the motor state information corresponding to the variable frequency motor at the time point t are recorded separately and are associated with each other.

[0123] Based on the above, the regenerative energy recovery and recycling method of this solution can be applied to a port electromagnetic crane operation control method; wherein the variable frequency motor is a hoisting motor of the port electromagnetic crane; the operation control method includes: responding to a start signal of the electromagnetic crane, executing S01 to S04; and further including one of the following:

[0124] (1) Establish a mathematical model for the energy fluctuation of variable frequency motors, smooth the energy fluctuations through energy storage units, and optimize energy scheduling according to preset strategies;

[0125] (2) According to the energy storage status information of the energy storage unit, the charge and discharge distribution of the energy storage unit is adjusted to balance the load of each sub-unit in the energy storage unit.

[0126] In this solution, when the hoisting motor is generating electricity, the regenerative power it generates is fed back to the common DC bus of the inverter, generating a pump-up voltage. Under the scheduling of the energy manager, the energy storage unit in this solution timely intervenes to convert the generated regenerative power into charging energy for the supercapacitor of the energy storage unit. To ensure the smooth consumption of regenerative energy, this solution establishes a mathematical model for the energy fluctuations of the variable frequency motor, smoothes the energy fluctuations through the energy storage unit, and optimizes energy scheduling according to a preset strategy, including:

[0127] A01. Establish a mathematical model of energy fluctuation. Based on the fact that the regenerative energy of the electromagnetic crane using a variable frequency motor is a time-varying process, it is assumed that the regenerative power is a function of time t and is defined as follows:

[0128] ;

[0129] in, is the electric power regenerated by the hoisting motor, in watts; is the mechanical-electrical conversion efficiency of the motor, It is the power converted from the mechanical energy of the motor;

[0130] Based on mechanical power Hoisting speed of the crane's hoisting motor and load force Related, it is expressed as follows:

[0131] ;

[0132] in, , is the load force, is the weight of the cargo, is the acceleration; is the lifting speed in meters per second;

[0133] By monitoring the mass and descent speed of the load, the electric power regenerated by the lifting motor is calculated in real time ;

[0134] A02. The energy storage unit is used to absorb the regenerative energy fluctuation and release the energy to the system in a timely manner. Assuming that the storage capacity of the energy storage unit is , and its relationship with time is expressed as follows:

[0135] ;

[0136] in, is the energy in the energy storage unit, its unit is joule, It is the power of regenerative electricity, that is, the power regenerated by the lifting motor. is the electrical power consumed by the system;

[0137] According to the storage capacity of the energy storage unit The relationship between the energy storage unit's upper limit and its charging and discharging is managed, including the following:

[0138] when = Energy storage limit of the energy storage unit When , the energy storage unit stops charging;

[0139] when Less than the lower limit of energy storage unit When , the energy storage unit stops discharging and enters the charging standby state;

[0140] By switching between charging and discharging, the energy storage unit smoothes the fluctuation of the regenerative energy generated by the hoisting motor and recovers the energy for timely release.

[0141] A03. In addition to the energy storage unit, the excess regenerative energy is fed back to the grid or used for other energy-consuming devices through the energy feedback system. The power conditioner is used in the circuit to transmit the excess regenerative energy to the grid. It is expressed as follows:

[0142] ;

[0143] in, For feedback power, The power of regenerative energy, The power that the energy storage unit can absorb after charging, is the current load demand of the electromagnetic crane, when When , it means that the regenerative energy generated by the hoisting motor can be fed back to the grid. When , it means that the system needs to obtain energy from the grid;

[0144] A04. Energy management is used to dispatch regenerative energy and loads to dynamically adjust the charging and discharging of energy storage units and grid feedback, including:

[0145] when Greater than When the energy storage unit is connected to the common DC bus, the energy manager controls the energy storage unit to be charged by introducing the regenerative energy generated by the hoisting motor;

[0146] When the energy storage unit is fully loaded, and When the energy manager controls the energy storage unit to maintain the electrical connection with the common DC bus interrupted;

[0147] When the system load requires more energy, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the common DC bus to assist the variable frequency motor in operating.

[0148] In addition, in order to efficiently and reliably balance the load of each supercapacitor in the energy storage unit, as a preferred implementation option, preferably, this solution adjusts the charge and discharge distribution of the energy storage unit according to the energy storage status information of the energy storage unit to balance the load of each sub-unit in the energy storage unit, including:

[0149] B01. When the energy storage unit is composed of multiple supercapacitors, the storage capacity of each supercapacitor is defined as follows:

[0150] The first i Energy storage of supercapacitors The voltage across the capacitor and capacitance value It is expressed as follows:

[0151] ;

[0152] in, It is i The energy stored in a supercapacitor at time t, in joules; It is i The capacitance value of a supercapacitor, in farads; It is i The voltage of a supercapacitor at time t, in volts;

[0153] Assuming that the energy storage unit has N supercapacitors that can be configured, the total system energy storage capacity is It is expressed as follows:

[0154] ;

[0155] B02. Assign charging priority to N supercapacitors. Assume that the charging power of each supercapacitor is Affected by its current voltage and the regenerative energy provided by the system Impact, the charging power is defined as:

[0156] ;

[0157] in, is the charging efficiency, which is between 0-1, is the current regenerative energy input power of the system, is the maximum charging voltage of the supercapacitor; The charging power of each supercapacitor is is the current voltage of the supercapacitor;

[0158] The formula shows that the supercapacitor with lower voltage will get more charging power first because the current voltage of the supercapacitor is Distance maximum voltage The farther away it is, the more energy it is allocated;

[0159] In order to prevent the supercapacitor from overcharging, the charging state of each supercapacitor is controlled by a threshold value, and the maximum acceptable voltage of each supercapacitor is defined. , once the current voltage of the supercapacitor Reached the maximum acceptable voltage , then the supercapacitor stops charging, and its strategy is described as follows:

[0160] when When the charging power is allocated according to the priority level,

[0161] when When the supercapacitor stops charging, the remaining regenerative energy is distributed to other supercapacitors.

[0162] B03. Assign discharge priorities to N supercapacitors. Assume that the output power requirement of the system is , the discharge power of each supercapacitor is , which is defined as follows:

[0163] ;

[0164] in, is the discharge efficiency, is the discharge power of each supercapacitor, is the current voltage of the supercapacitor, is the output power requirement of the system;

[0165] This formula strategy shows that supercapacitors with higher voltages are discharged first to provide more stable output power;

[0166] In order to prevent the supercapacitor from over-discharging, the discharge state of each supercapacitor is controlled by a threshold value and the minimum discharge voltage is set. ;

[0167] when When , the supercapacitor continues to discharge;

[0168] when When , the supercapacitor stops discharging;

[0169] B04. Dynamically adjusting the charging and discharging sequence of the N supercapacitors of the energy storage unit through the energy manager;

[0170] In terms of charging priority adjustment, the voltage of all supercapacitors is calculated in real time, and the charging priority of supercapacitors with lower voltage is increased. At the same time, it is ensured that the voltage of each supercapacitor does not exceed the maximum acceptable voltage. ;

[0171] In terms of discharge priority adjustment, when the system load increases, the supercapacitors with higher voltages are given priority to supply energy. At the same time, the voltage of each supercapacitor is ensured not to be lower than the minimum discharge voltage. ;

[0172] The energy manager distributes energy among the N supercapacitors of the energy storage unit using a dynamic programming algorithm, allowing the system to optimize the charging and discharging sequence at each time step t to minimize energy loss and efficiency degradation. Its objective function is defined as follows:

[0173] ;

[0174] in, is charging efficiency; The charging power of each supercapacitor is is the discharge efficiency, is the discharge power of each supercapacitor.

[0175] In terms of charging and discharging, in order to be able to conveniently and timely correct the charging and discharging parameters of the supercapacitor so that the supercapacitor can better perform its performance during operation, as a better implementation option, preferably, this solution adjusts the charging and discharging distribution of the energy storage unit to balance the load of each sub-unit in the energy storage unit and also includes: optimizing the distribution of the supercapacitor charging rate and optimizing the distribution of the supercapacitor discharging;

[0176] The optimization of supercapacitor charging rate distribution includes:

[0177] Introducing the partition coefficient , which is used to adjust the charging rate of each supercapacitor. Its corresponding charging power is defined as follows:

[0178] ;

[0179] In the above formula, To allocate to i The charging power of a supercapacitor, is the total regenerative energy power of the system, For the i The dynamic allocation coefficient of the supercapacitor satisfies ;

[0180] The corresponding distribution coefficient of the supercapacitor according to its voltage state Dynamic adjustment is performed, and the formula is defined as follows:

[0181] ;

[0182] in, It is i The charge distribution coefficient of a supercapacitor at time t is, is the maximum allowable charging voltage of the supercapacitor, is the current voltage of the supercapacitor at time t, It is the combined charging demand of N supercapacitors, which represents the total remaining charge of N supercapacitors in the system;

[0183] Optimizing the distribution of supercapacitor discharge includes:

[0184] Introducing the partition coefficient , which is used to adjust the discharge rate of each supercapacitor. Its corresponding discharge power is defined as follows:

[0185] ;

[0186] In the above formula, To allocate to i The discharge power of a supercapacitor, is the current load demand of the system, For the i The dynamic distribution coefficient of a supercapacitor, that is, the discharge distribution coefficient, satisfies ;

[0187] The corresponding distribution coefficient of the supercapacitor according to its voltage state Dynamic adjustment is performed, and the formula is defined as follows:

[0188] ;

[0189] in, It is i The discharge distribution coefficient of a supercapacitor at time t is, is the current voltage of the supercapacitor at time t, is the sum of the voltages of the N supercapacitors, which represents the sum of the voltages of the N supercapacitors in the system;

[0190] The energy manager dynamically adjusts control inputs based on future system predictions to optimize system performance. The control goal is to minimize energy loss and optimize energy utilization during charging and discharging. Its objective function is defined as follows:

[0191] ;

[0192] in, is charging efficiency; The charging power of each supercapacitor is is the discharge efficiency, is the discharge power of each supercapacitor.

[0193] Based on the above, this solution also provides a method for recycling the regenerative energy of a port crane variable frequency motor, which is applied to the above-mentioned regenerative energy recovery and recycling method or the above-mentioned port electromagnetic crane operation control method.

[0194] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for controlling the operation of a port electromagnetic crane. The hoisting motor of the port electromagnetic crane is a variable frequency motor, which is electrically connected to a frequency converter that is connected to the power grid to input electrical energy for driving the variable frequency motor. A common DC bus is provided in the circuit connecting the frequency converter and the variable frequency motor. An energy manager is connected to the common DC bus, and the energy manager is connected to an energy storage unit. The method is characterized by: The control method includes executing the following steps in response to a start signal of the electromagnetic crane: S01. Collect voltage data of a common DC bus to which the variable frequency motor is connected in real time to generate voltage monitoring data; S02. Determine the working state of the variable frequency motor according to the voltage monitoring data and preset conditions, and generate motor state information; S03. The energy manager collects parameters of the energy storage unit at a preset time frequency and generates energy storage status information according to preset conditions; S04. Based on the motor status information and the energy storage status information of the energy storage unit, the energy manager switches the working state of the energy storage unit to the following state: In the first state, the energy manager controls the energy storage unit to be connected to the public DC bus to introduce the regenerative energy generated by the variable frequency motor for charging; In the second state, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the common DC bus to assist the operation of the variable frequency motor; In the third state, the energy manager controls the energy storage unit to maintain an electrical disconnection with the common DC bus; The working control method further includes smoothing energy fluctuations through the energy storage unit, and adjusting the charge and discharge distribution of the energy storage unit according to the energy storage state information of the energy storage unit to balance the load of each sub-unit in the energy storage unit; Among them, smoothing energy fluctuations includes: A01. Establish a mathematical model of energy fluctuation. Based on the fact that the regenerative energy of the electromagnetic crane using a variable frequency motor is a time-varying process, it is assumed that the regenerative power P regen (t) is a function of time t and is defined as follows: Among them, P regen (t) is the electric power regenerated by the hoisting motor; η m is the mechanical-electrical conversion efficiency of the motor, P mech (t) is the power converted from the motor’s mechanical energy; Based on mechanical power P mech (t) and the lifting speed v(t) of the crane's lifting motor and the load force F load (t) is related and can be expressed as follows: P mech (t)=F load (t)×v(t); Among them, F load (t) = m × g, where m is the weight of the cargo, g is the acceleration; v(t) is the lifting speed; By monitoring the mass and descent speed of the load, the electric power P regenerated by the lifting motor is calculated in real time. regen (t); A02. The energy storage unit is used to absorb the regenerative energy fluctuation and release the energy to the system in a timely manner. Assuming that the storage capacity of the energy storage unit is E stored (t), and its relationship with time is expressed as follows: Among them, E stored (t) is the energy in the energy storage unit, P regen (t) is the power of regenerative electricity, P load (t) is the electrical power consumed by the system; According to the energy storage unit, the storage capacity is E stored (t) Manage the charging and discharging of energy in relation to the upper limit of energy storage, including the following: When E stored (t) = upper limit of energy storage E of the energy storage unit max When , the energy storage unit stops charging; When E stored (t) is less than the lower limit E of the energy storage unit min When , the energy storage unit stops discharging and enters the charging standby state; Through the above-mentioned charge and discharge switching, the energy storage unit smoothes the regenerative energy fluctuations generated by the lifting motor and recovers energy for timely release.

2. The port electromagnetic crane operation control method according to claim 1, characterized in that: The frequency converter includes a rectifier, an inverter and a braking unit. The rectifier is connected to the power grid to input electric energy for driving the variable frequency motor. The inverter is electrically connected to the rectifier and the variable frequency motor respectively to supply the electric energy input by the rectifier to the variable frequency motor. The braking unit is connected to the circuit between the rectifier and the inverter. The braking unit is also connected to a braking resistor. The braking resistor is used to feed back the regenerative energy on the common DC bus for consumption when the variable frequency motor is in a power generation state.

3. The port electromagnetic crane operation control method according to claim 1, characterized in that: The energy storage unit includes a capacitance management module and at least one supercapacitor; the energy manager includes a bidirectional DC-DC driver and a PLC module. The PLC module is electrically connected to the bidirectional DC-DC driver, and the working state of the bidirectional DC-DC driver is controlled by the PLC module. The bidirectional DC-DC driver is also electrically connected to the at least one supercapacitor. The capacitance management module is electrically connected to the PLC module and the at least one supercapacitor, and is used to obtain parameters of the at least one supercapacitor at a preset time frequency and transmit them to the PLC module to generate energy storage status information.

4. The port electromagnetic crane operation control method according to any one of claims 1 to 3, characterized in that: In S01, the voltage monitoring data are all associated with the time point at which they were collected; S02 includes: S021, collect the voltage monitoring data within the preset time period in time series, and calculate the difference between each voltage monitoring data and the preset reference voltage V according to the voltage monitoring data. ref The difference △V(t) and the voltage change rate S022. Determine the difference △V(t) and voltage change rate at the same time point t When △V(t)≈0 or △V(t≤0, and the voltage change rate or When t is reached, the working state of the variable frequency motor at that time point t is defined as the electric state, and the definition time of the working state is recorded at the same time; When △V(t)>0, and the voltage change rate or voltage change rate When the working state of the variable frequency motor at the time point t is defined as the power generation state, and the definition time of the working state is recorded at the same time, where x 阈值 Set a threshold for the voltage change rate; S023. Obtain the working state definition of the variable frequency motor and generate motor state information.

5. The port electromagnetic crane operation control method according to claim 4, characterized in that: S023 also includes: Obtain the working state definition of the variable frequency motor. When it points to the time point t when the variable frequency motor is in the power generation state, obtain the working state definition of the variable frequency motor in the time period T before the time point t according to the preset time window T; When the working state definition of the variable frequency motor in the time period T is all the power generation state, the power generation state is generated as the motor state information; When the working state definition includes the electric state, the electric state is generated as the motor state information; wherein the working state definition and the motor state information corresponding to the variable frequency motor at the time point t are recorded separately and are associated with each other.

6. The port electromagnetic crane operation control method according to claim 1, characterized in that: While energy fluctuations are smoothed by energy storage units, energy scheduling optimization is also performed according to preset strategies, which include: A03. In addition to the energy storage unit, the excess regenerative energy is fed back to the grid or used for other energy-consuming devices through the energy feedback system. The power regulator is used in the circuit to transmit the excess regenerative energy to the grid. The feedback power P feed (t) is expressed as follows: P feed (t)=P regen (t)-P stored (t)-P load (t); Among them, P feed (t) is the feedback power, P regen (t) is the power of regenerative energy, P stored (t) is the power that the energy storage unit can absorb after charging, P load (t) is the current load demand of the electromagnetic crane. When P feed When (t)>0, it means that the regenerative energy generated by the hoisting motor is fed back to the grid, P feed When (t)<0, it means that the system needs to obtain energy from the grid; A04. Energy management is used to dispatch regenerative energy and loads to dynamically adjust the charging and discharging of energy storage units and grid feedback, including: When P regen (t) is greater than P load At (t), the energy manager controls the energy storage unit to be connected to the common DC bus to introduce the regenerative energy generated by the hoisting motor for charging; When the energy storage unit is fully loaded, and P feed When (t)>0, the energy manager controls the energy storage unit to maintain the electrical connection with the common DC bus interrupted; When the system load requires more energy, the energy manager controls the electric energy stored in the energy storage unit to be supplied to the common DC bus to assist the variable frequency motor in operating.

7. The port electromagnetic crane operation control method according to claim 1, characterized in that: Based on the energy storage status information of the energy storage unit, the charge and discharge distribution of the energy storage unit is adjusted to balance the load of each sub-unit in the energy storage unit, including: B01. When the energy storage unit is composed of multiple supercapacitors, the storage capacity of each supercapacitor is defined as follows: The energy storage E of the i-th supercapacitor cap,i (t) Voltage V across the capacitor cap,i (t) and capacitance C i It is expressed as follows: Among them, E cap,i (t) is the energy storage capacity of the i-th supercapacitor at time t, in joules; C i is the capacitance value of the i-th supercapacitor, in farads; V cap,i (t) is the voltage of the i-th supercapacitor at time t, in volts; Assume that the energy storage unit is configured with N supercapacitors, and the total system energy storage E total (t) is expressed as follows: B02. Assign charging priority to N supercapacitors. Assume that the charging power of each supercapacitor is P charge,i (t) is affected by its current voltage V cap,i (t) and the regenerative energy P provided by the system regen (t) affects the charging power, and the charging power is defined as: Among them, η charge is the charging efficiency, which is between 0-1, P regen (t) is the current input power of the regenerative energy of the system, V max is the maximum charging voltage of the supercapacitor; P charge,i (t) is the charging power of each supercapacitor, V cap,i (t) is the current voltage of the supercapacitor; The formula shows that the supercapacitor with lower voltage will get more charging power first because the current voltage V cap,i (t) Distance to maximum voltage V max The farther away it is, the more energy it is allocated; In order to prevent the supercapacitor from overcharging, the charging state of each supercapacitor is controlled by a threshold value, and the maximum acceptable voltage V of each supercapacitor is defined. th,i , once the current voltage V cap,i (t) reaches the maximum acceptable voltage V th,i , then the supercapacitor stops charging, and its strategy is described as follows: When V cap,i (t)<V th,i When the charging power is allocated according to the priority level, When V cap,i (t)≥V th,i When the supercapacitor stops charging, the remaining regenerative energy is distributed to other supercapacitors. B03. Assign discharge priority to N supercapacitors. Assume that the output power requirement of the system is P load (t), the discharge power of each supercapacitor is P discharge，i (t), which is defined as follows: Among them, η discharge is the discharge efficiency, P discharge,i (t) is the discharge power of each supercapacitor, V cap,i (t) is the current voltage of the supercapacitor, P load (t) is the output power requirement of the system; This formula strategy shows that supercapacitors with higher voltages are discharged first to provide more stable output power; In order to prevent the supercapacitor from over-discharging, the discharge state of each supercapacitor is controlled by a threshold value, and the minimum discharge voltage V is set. min,i ; When V cap,i (t)>V min,i When , the supercapacitor continues to discharge; When V cap,i (t)≤V min,i When , the supercapacitor stops discharging; B04. Dynamically adjusting the charging and discharging sequence of the N supercapacitors of the energy storage unit through the energy manager; In terms of charging priority adjustment, the voltage of all supercapacitors is calculated in real time, and the charging priority of supercapacitors with lower voltage is increased. At the same time, it is ensured that the voltage of each supercapacitor does not exceed the maximum acceptable voltage V th,i ; In terms of discharge priority adjustment, when the system load increases, the supercapacitors with higher voltage are given priority to supply energy. At the same time, the voltage of each supercapacitor is ensured not to be lower than the minimum discharge voltage V min,i ; The energy manager distributes energy among the N supercapacitors of the energy storage unit using a dynamic programming algorithm, allowing the system to optimize the charging and discharging sequence at each time step t to minimize energy loss and efficiency degradation. Its objective function is defined as follows: Among them, η charge is the charging efficiency; P charge,i (t) is the charging power of each supercapacitor, η discharge is the discharge efficiency, P discharge,i (t) is the discharge power of each supercapacitor.

8. The port electromagnetic crane operation control method according to claim 7, characterized in that: The charging and discharging distribution of the energy storage unit is adjusted to balance the load of each sub-unit in the energy storage unit, and also includes: optimizing the charging rate of the supercapacitor and optimizing the discharging of the supercapacitor; Optimizing the distribution of supercapacitor charging rates includes: Introducing the distribution coefficient k i (t) is used to adjust the charging rate of each supercapacitor, and its corresponding charging power is defined as follows: P charge，i (t)=k i (t)×P regen (t); Among them, P charge，i (t) is the charging power allocated to the i-th supercapacitor, P regen (t) is the total regenerative energy power of the system, k i (t) is the dynamic allocation coefficient of the i-th supercapacitor, which satisfies The distribution coefficient k corresponding to the voltage state of the supercapacitor i (t) is dynamically adjusted, and its formula is defined as follows: Among them, k i (t) is the charge distribution coefficient of the i-th supercapacitor at time t, V max is the maximum allowable charging voltage of the supercapacitor, V cap,i (t) is the current voltage of the supercapacitor at time t, It is the combined charging demand of N supercapacitors, which represents the total remaining charge of N supercapacitors in the system; Optimizing the distribution of supercapacitor discharge includes: Introducing the distribution coefficient k' i (t) is used to adjust the discharge rate of each supercapacitor, and its corresponding discharge power is defined as follows: P discharge，i (t)=k' i (t)×P load (t); Among them, P discharge，i (t) is the discharge power allocated to the i-th supercapacitor, P load (t) is the current load demand of the system, k' i (t) is the dynamic distribution coefficient of the i-th supercapacitor, that is, the discharge distribution coefficient, which satisfies The distribution coefficient k corresponding to the voltage state of the supercapacitor i (t) is dynamically adjusted, and its formula is defined as follows: Among them, k' i (t) is the discharge distribution coefficient of the i-th supercapacitor at time t, V cap,i (t) is the current voltage of the supercapacitor at time t, is the sum of the voltages of the N supercapacitors, which represents the sum of the voltages of the N supercapacitors in the system; The energy manager dynamically adjusts control inputs based on future system predictions to optimize system performance. The control goal is to minimize energy loss and optimize energy utilization during charging and discharging. Its objective function is defined as follows: Among them, η charge is the charging efficiency; P charge,i (t) is the charging power of each supercapacitor, η discharge is the discharge efficiency, P discharge,i (t) is the discharge power of each supercapacitor.

9. A method for recycling regenerative energy of a port crane variable frequency motor, characterized in that: The invention is applied with the port electromagnetic crane operation control method according to any one of claims 1 to 8.

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