Variable frequency drive system of tower crane and control method for variable frequency drive system of tower crane

Abstract

The application discloses a tower crane variable frequency driving system and a control method thereof, and relates to the field of tower crane control. The tower crane variable frequency driving system comprises a tower crane control system, a frequency converter module, an energy storage system and an energy storage module. The frequency converter module comprises a frequency converter control unit, a driving unit of the main driving system and the energy storage system connected through a direct current bus. The energy storage module comprises a super capacitor and a DC / DC bidirectional direct current converter connected between the direct current bus and the super capacitor. The tower crane control system is configured to control the energy storage module and the energy storage system to store the electric energy of the direct current bus when the voltage rise of the direct current bus caused by the operation of the main driving system exceeds a preset threshold. The tower crane variable frequency driving system is based on the common direct current bus technology, combines the super capacitor and the energy storage system, and stores the regenerative braking energy in the super capacitor and the energy storage system, so that the waste of the regenerative braking energy is avoided, and the influence of thermal pollution is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tower crane control, in particular to a tower crane variable frequency driving system and a control method thereof. BACKGROUND

[0002] A tower crane generally comprises three mechanisms, i.e., a hoisting mechanism, a slewing mechanism and a luffing mechanism, which can be driven by corresponding inverter units in a frequency converter, as shown in FIG. 1. Figure 1 When the motors driven by the inverter units of the mechanisms are in an electric mode (for example, starting, accelerating or steady running, etc.), the electric energy is obtained from the power grid to do work. When the motors are in a descending or braking process (i.e., the motors are in a regenerative power generation state), the DC bus voltage of the frequency converter will rise, and if the rise is sustained, the frequency converter will terminate operation due to overvoltage alarm.

[0003] In the prior art, in order to limit the voltage at the DC bus end of the frequency converter, the regenerative electric energy generated thereby is usually converted into heat energy in the form of an externally connected braking resistor for consumption. However, the prior art not only wastes energy, but also causes thermal pollution to the environment. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a tower crane variable frequency driving system to solve the problem of energy waste and thermal pollution to the environment in the prior art tower crane variable frequency driving process.

[0005] In order to achieve the above purpose, the first aspect of the present application provides a tower crane variable frequency driving system, which comprises a tower crane control system, a frequency converter module, an energy storage system and an energy storage module. The frequency converter module comprises a frequency converter control unit, a rectifier unit connected with an external AC power supply unit, and a main drive system and a drive unit of the energy storage system connected through a DC bus. The rectifier unit is connected to the DC bus for supplying power to the motor connected to the main drive system through the DC bus. The energy storage module comprises a super capacitor and a DC / DC bidirectional DC converter connected between the DC bus and the super capacitor. The tower crane control system is electrically connected to the frequency converter control unit and the DC / DC bidirectional DC converter. The frequency converter control unit is electrically connected to the main drive system and the drive unit of the energy storage system. The tower crane control system is configured to control the energy storage module and the energy storage system to store the electric energy of the DC bus when the voltage of the DC bus caused by the operation of the main drive system rises above a preset threshold U H0 , and to stabilize the voltage of the DC bus between an upper voltage threshold U H and a lower voltage threshold U L .

[0006] In an embodiment of the present invention, the main drive system includes a hoisting inverter unit, a slewing inverter unit and a luffing inverter unit.

[0007] In an embodiment of the present invention, the energy storage system includes a drive unit, a lifting mechanism, and a load of the energy storage system. The lifting mechanism includes a motor and a brake.

[0008] In the embodiment of the present invention, when the main drive system is running, the voltage of the DC bus increases by more than a preset threshold value U H0 When the tower crane control system is configured to: send an electric energy storage instruction to control the energy storage module to store the electric energy of the DC bus, the DC / DC bidirectional DC converter responds to the electric energy storage instruction, and controls the conversion system to charge the supercapacitor from the DC bus; and controls the inverter control unit to send a lifting instruction to control the energy storage system to store the electric energy of the DC bus, the drive unit of the energy storage system is configured to respond to the lifting instruction, and drive the motor of the energy storage system to perform work, so as to convert the electric energy of the DC bus into work and then store it.

[0009] In an embodiment of the present invention, the tower crane control system is further configured to: when the voltage drop of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0010] In the embodiment of the present invention, when the main drive system is running, the voltage drop of the DC bus exceeds the preset threshold value U L0 When the tower crane control system is in operation, the tower crane control system is further configured to: send an electric energy release instruction to control the energy storage module to release electric energy to the DC bus, the DC / DC bidirectional DC converter responds to the electric energy release instruction, and controls the supercapacitor to release electric energy to the DC bus; and control the inverter control unit to send a descending instruction to control the energy storage system to release electric energy to the DC bus, the drive unit of the energy storage system is configured to respond to the descending instruction, drive the motor of the energy storage system to operate, and release the electric energy converted by regenerative braking to the DC bus.

[0011] The second aspect of the present invention provides a control method for a tower crane variable frequency drive system, the control method for a tower crane variable frequency drive system is applied to the tower crane control system of the tower crane variable frequency drive system, and the control method for a tower crane variable frequency drive system comprises: monitoring the state of the motor connected to the main drive system; monitoring the voltage of the DC bus; and when the voltage of the DC bus rises above a preset threshold value U when the main drive system is running. H0 When the energy storage module and the energy storage system are controlled to store the electric energy of the DC bus, and the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0012] In an embodiment of the present invention, controlling the energy storage module and the energy storage system to store the electric energy of the DC bus includes: sending an electric energy storage instruction to control the energy storage module to store the electric energy of the DC bus, the DC / DC bidirectional DC converter responding to the electric energy storage instruction and controlling the conversion system to charge the supercapacitor from the DC bus; and controlling the inverter control unit to send a boost instruction to control the energy storage system to store the electric energy of the DC bus, the drive unit of the energy storage system responding to the boost instruction and driving the motor of the energy storage system to perform work, so as to convert the electric energy of the DC bus into work and then store it.

[0013] In an embodiment of the present invention, it is characterized in that the control method for the tower crane variable frequency drive system further includes: when the voltage drop of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0014] In an embodiment of the present invention, controlling the energy storage module and the energy storage system to release electrical energy to the DC bus further includes: sending an electrical energy release instruction to control the energy storage module to release electrical energy to the DC bus, the DC / DC bidirectional DC converter responding to the electrical energy release instruction and controlling the supercapacitor to release electrical energy to the DC bus; and controlling the inverter control unit to send a decrease instruction to control the energy storage system to release electrical energy to the DC bus, the drive unit of the energy storage system responding to the decrease instruction and driving the motor of the energy storage system to operate, and releasing electrical energy converted by regenerative braking to the DC bus.

[0015] Through the above technical solution, the tower crane variable frequency drive system provided by the embodiments of the present invention includes a tower crane control system, a frequency converter module, an energy storage system, and an energy storage module. The frequency converter module includes a frequency converter control unit, a main drive system, and a drive unit of the energy storage system connected via a DC bus. The energy storage module includes a supercapacitor and a DC / DC bidirectional DC converter connected to the DC bus and the supercapacitor. The tower crane control system is configured to control the energy storage module and the energy storage system to store electrical energy from the DC bus when the voltage of the DC bus rises above a preset threshold due to operation of the main drive system. Based on common DC bus technology, this tower crane variable frequency drive system combines supercapacitors and an energy storage system to store regenerative braking energy in the supercapacitors and energy storage system, thereby avoiding waste of regenerative braking energy and reducing the impact of thermal pollution on the environment. Furthermore, the tower crane variable frequency drive system provided by the embodiments of the present invention can release stored regenerative braking energy for use by the motor connected to the main drive system when the motor needs to consume electrical energy to perform work, thereby conserving and efficiently utilizing regenerative braking energy.

[0016] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present invention, but do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0018] Figure 1 It is a structural diagram of an example tower crane variable frequency drive system of the prior art;

[0019] Figure 2 1 is a schematic structural diagram of a tower crane variable frequency drive system provided by an embodiment of the present invention;

[0020] Figure 3 It is a structural diagram of another example of a tower crane variable frequency drive system in the prior art;

[0021] Figure 4 is a structural diagram of another tower crane variable frequency drive system provided by an embodiment of the present invention; and

[0022] Figure 5 The present invention is a flowchart of a control method for a tower crane variable frequency drive system provided by an embodiment of the present invention.

[0023] Description of Reference Numerals

[0024] 10 Tower crane control system 20 Inverter module 21 Inverter control unit 22 Rectifier unit 23 Drive unit of energy storage system 24 Raise the inverter unit 25 Rotary inverter unit 26 Luffing inverter unit 31 supercapacitors 40 External AC power supply unit DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present invention and are not used to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0027] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0028] Figure 2 This is a schematic diagram of the structure of the tower crane variable frequency drive system provided by the embodiment of the present invention. Figure 2 The tower crane variable frequency drive system may include a tower crane control system 10, a frequency converter module 20, an energy storage system (not shown in the figure), and an energy storage module (not shown in the figure). The frequency converter module 20 may include a frequency converter control unit 21, a rectifier unit 22 connected to an external AC power supply unit 40, and a main drive system (not shown in the figure) and a drive unit 23 of the energy storage system connected via a DC bus. The rectifier unit 22 is connected to the DC bus and is used to power the motor connected to the main drive system via the DC bus. The energy storage module includes a supercapacitor 31 and a DC / DC bidirectional DC converter connected to the DC bus and the supercapacitor 31. The tower crane control system 10 is electrically connected to the frequency converter control unit 21 and the DC / DC bidirectional DC converter, and the frequency converter control unit 21 is electrically connected to the main drive system and the drive unit 23 of the energy storage system.

[0029] The tower crane control system 10 is configured to: when the voltage of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U H0 When the energy storage module and the energy storage system are controlled to store the electric energy of the DC bus, and the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0030] In the inverter module 20 sharing a common DC bus, the motors of the main drive system may be in various states: motoring, generating, and stationary. That is, at the same moment, one motor may be in the motoring state while another is in the generating state. Therefore, the direction of the DC bus voltage fluctuation (rising or falling) is determined by the motoring or generating power of the motors in each state.

[0031] Please refer to Figure 2 In the preferred embodiment of the present invention, the main drive system may include a hoisting inverter unit 24, a slewing inverter unit 25, and a luffing inverter unit 26. The motors connected to the main drive system include a hoisting motor, a slewing motor, a luffing motor, and the like.

[0032] The energy storage system of the embodiment of the present invention may preferably include a drive unit 23 of the energy storage system, a lifting mechanism, and an energy storage system load. Preferably, the lifting mechanism may include a motor and a brake.

[0033] To illustrate by way of example, the drive unit 23 of the energy storage system is, for example, an inverter unit of the energy storage system, and the motor of the energy storage system is preferably a load-lifting motor of the energy storage system. Preferably, since the tower crane includes a counterweight, the counterweight can be used as the load structure of the energy storage system to achieve the reuse of the counterweight. Further preferably, depending on the structure of the tower crane or the environment in which the tower crane is implemented, other auxiliary lifting devices can be used as the energy storage system to achieve electrical energy / potential energy (electrical energy / potential energy) conversion and electrical energy storage.

[0034] Taking a tower crane with variable frequency speed control as an example, when the voltage rise of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U H0When the inverter module 20 is in operation, the electric energy generated will continuously charge the DC filter capacitor of the inverter module 20 through the freewheeling diode of the inverter unit of the inverter module 20. Since the rectifier bridge generally adopts irreversible rectification, it is impossible to feed the excess energy back to the power supply, so that the DC bus voltage of the inverter module 20 is continuously pumped up, which will cause the inverter module 20 to have an overvoltage fault, affecting the normal operation of the tower crane. The embodiment of the present invention is based on the common DC bus technology, and the energy storage module and the energy storage system are connected to the DC bus of the main drive system in the inverter module 20. Among them, the energy storage module may include a DC / DC bidirectional DC converter and a supercapacitor 31, and the energy storage system is, for example, an electric energy / potential energy (electric energy / potential energy) conversion device, which may include a drive unit (i.e., an inverter unit) 23 of the energy storage system, a load lifting mechanism (including a motor), and a load structure (including heavy objects). Therefore, the voltage rise of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U H0 When the tower crane control system controls the energy storage module and the energy storage system to store the electric energy of the DC bus, and makes the voltage of the DC bus stable at the upper voltage threshold U H and the lower voltage threshold U L between.

[0035] The voltage of the DC bus in the inverter (ie, the inverter module 20) must be stable within a certain range to work normally. The upper voltage threshold (also called the overvoltage alarm threshold) is U H , lower voltage threshold (also called undervoltage alarm threshold) U L In the embodiment of the present invention, in order to prevent the DC bus from being over / under-voltage alarmed due to transient changes of the motor connected to the main drive system, which may cause the inverter to shut down, the DC bus can be monitored in real time so that the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L Between: When the main drive system is running and the DC bus voltage rises above U H0 During startup, the energy storage module and the energy storage system store the electrical energy of the DC bus. Since the energy storage system has a startup process, its ability to store (absorb) electricity is gradually established within a certain period of time. Therefore, during the startup phase, the supercapacitors of the energy storage module are controlled to improve the electricity absorption capacity and quickly smooth out the voltage rise of the DC bus.

[0036] Preferably, the voltage rise of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U H0When the tower crane control system 10 is in operation, the tower crane control system 10 can also be configured to: send an electric energy storage instruction to control the energy storage module to store the electric energy of the DC bus, the DC / DC bidirectional DC converter responds to the electric energy storage instruction, and controls the conversion system to charge the supercapacitor 31 from the DC bus; and control the inverter control unit 21 to send a lifting instruction to control the energy storage system to store the electric energy of the DC bus, the drive unit 23 of the energy storage system is configured to respond to the lifting instruction and drive the motor of the energy storage system to perform work, so as to convert the electric energy of the DC bus into work and then store it.

[0037] For example, when the main drive system is running and the DC bus voltage rises to more than U H0 When the motor connected to the main drive system is powered on, the regenerative current generated by the motor is fed to the DC bus, and at the moment of startup, the DC bus voltage will generate a peak impact. The tower crane control system 10 sends an electric energy storage instruction to the DC / DC bidirectional DC converter to charge the supercapacitor 31. At the same time, the tower crane control system 10 sends a lifting instruction (i.e., a lifting signal) to the drive unit 23 of the energy storage system. The drive unit 23 of the energy storage system drives the load lifting mechanism to lift the load structure, continuously consuming the electric energy on the DC bus, avoiding the overvoltage fault of the inverter module 20 caused by the continuous rise in voltage, and can convert the regenerative electric energy into potential energy (potential energy) for storage. Since the supercapacitor 31 has a high power density, it can quickly absorb electric energy, smooth out the feedback electric energy impact at the moment of startup or the initial stage of speed change, and can store electric energy. However, due to the energy density limitation of the supercapacitor 31, after the startup feedback current becomes flat, the regenerative electric energy is mainly absorbed by the energy storage system.

[0038] Preferably, the tower crane control system 10 can also be configured to: when the voltage drop of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0039] For example, the tower crane control system 10 communicates with the inverter module 20 and the DC / DC bidirectional converter in two directions to exchange information in real time. In order to efficiently utilize the regenerative braking energy, in the embodiment of the present invention, when the voltage drop of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U L0 When the power is on, the energy storage module and the energy storage system can be controlled to release electrical energy to the DC bus.

[0040] Preferably, when the main drive system is running, the voltage drop of the DC bus exceeds a preset threshold value UL0 When the tower crane control system 10 is in operation, the tower crane control system 10 can also be configured to: send an electric energy release instruction to control the energy storage module to release electric energy to the DC bus, the DC / DC bidirectional DC converter responds to the electric energy release instruction, and controls the supercapacitor 31 to release electric energy to the DC bus; and control the inverter control unit 21 to send a descending instruction to control the energy storage system to release electric energy to the DC bus, the drive unit 23 of the energy storage system is configured to respond to the descending instruction, drive the motor of the energy storage system to run, and release the electric energy converted by regenerative braking to the DC bus.

[0041] For example, when the main drive system is operating and the inverter module 20 (DC bus) consumes electrical energy, the tower crane control system 10 can send an energy release instruction to the DC / DC bidirectional DC converter to control the supercapacitor 31 to release electrical energy to the DC bus, and control the inverter control unit 21 to send a descending instruction to the drive unit 23 of the energy storage system. The drive unit 23 of the energy storage system responds to the descending instruction and drives the load lifting mechanism to lower the load structure to release electrical energy to the DC bus, thereby pumping up the DC bus voltage. Optionally, the tower crane control system 10 can also first control the DC / DC bidirectional DC converter to release electrical energy from the supercapacitor 31, and then control the inverter control unit 21 to send a descending instruction to the drive unit 23 of the energy storage system to drive the load lifting mechanism to lower the load structure to release stored potential energy, thereby prioritizing the storage capacity of the supercapacitor.

[0042] As mentioned above, the voltage of the DC bus in the inverter (ie, the inverter module 20) must be stable within a certain range to work normally. The upper voltage threshold (also called the overvoltage alarm threshold) U H , lower voltage threshold (also called undervoltage alarm threshold) U L In the embodiment of the present invention, in order to prevent the DC bus from being over / under-voltage alarmed due to transient changes of the motor connected to the main drive system, which may cause the inverter to shut down, the DC bus can be monitored in real time so that the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L Between: When the main drive system is running and the DC bus voltage drops more than U L0 When the energy storage module and the energy storage system are in operation, they need to release the electric energy to the DC bus as quickly as possible (especially giving priority to releasing the electric energy of the supercapacitor in the energy storage module) to reserve sufficient storage capacity as much as possible.

[0043] The tower crane control system 10 can also be configured to monitor the voltage of the DC bus and control the start-stop and operating speed of the drive unit of the energy storage system according to the change of the voltage of the DC bus, so that the bus voltage is stabilized between the upper voltage threshold U H and the lower voltage threshold U L .

[0044] When the main drive system (connected motor) operating state changes abruptly or the external power supply voltage fluctuates sharply, the DC bus voltage may also be disturbed. To avoid overvoltage / undervoltage alarm and stop the frequency converter, the tower crane control system 10 is further configured as follows: during energy storage, when the voltage of the DC bus drops below U L1 (U H0 may be greater than U L0 ), the rate of energy absorption from the frequency converter DC bus by the energy storage module / energy storage system is reduced (for example, the super capacitor charging current can be reduced and the energy storage system motor lifting speed can be reduced); when the DC bus voltage continues to drop below U L2 , the energy storage module and the energy storage system stop absorbing energy from the DC bus; when the DC bus voltage continues to drop below U L3 , the energy storage module and the energy storage system immediately release energy to the DC bus to avoid triggering an undervoltage alarm, until the DC bus voltage rises to U L3 , the energy release is stopped. During the energy release process, when the DC bus voltage rises above U H1 , the rate of energy release from the frequency converter DC bus by the energy storage module / energy storage system is reduced (for example, the super capacitor discharge current to the DC bus can be reduced and the energy storage system motor descending speed can be reduced); when the DC bus voltage continues to rise above U H2 , the energy storage module and the energy storage system stop releasing energy to the DC bus; when the DC bus voltage continues to rise above U H3 , the energy storage module and the energy storage system immediately absorb energy from the DC bus to avoid triggering an overvoltage alarm, until the DC bus voltage falls to U H3 , the energy absorption is stopped.

[0045] Accordingly, the tower crane variable frequency drive system provided in an embodiment of the present invention includes a tower crane control system, a frequency converter module, an energy storage system, and an energy storage module. The frequency converter module includes a frequency converter control unit, a main drive system, and a drive unit for the energy storage system connected via a DC bus. The energy storage module includes a supercapacitor and a DC / DC bidirectional DC converter connected to the DC bus and the supercapacitor. The tower crane control system is configured to control the energy storage module and the energy storage system to store electrical energy from the DC bus when the voltage of the DC bus rises above a preset threshold due to operation of the main drive system. Based on common DC bus technology, this tower crane variable frequency drive system combines supercapacitors and an energy storage system to store regenerative braking energy in the supercapacitors and energy storage system, thereby avoiding waste of regenerative braking energy and reducing the impact of thermal pollution on the environment. Furthermore, the tower crane variable frequency drive system provided in an embodiment of the present invention can release stored regenerative braking energy for use by the motor connected to the main drive system when the motor needs to consume electrical energy to perform work, thereby conserving and efficiently utilizing regenerative braking energy.

[0046] Furthermore, the supercapacitor and electric energy / potential energy (electric energy / potential energy) conversion device configured in the embodiments of the present invention can not only utilize their high power density to smooth the feedback energy impact at the moment of starting and stopping the tower crane variable frequency drive system, but also expand the energy absorption capacity, thereby reducing the power requirements of the drive unit of the energy storage system. In conditions where the tower crane is tall and the heavy object has a long descent distance, the use of the electric energy / potential energy (electric energy / potential energy) conversion device can compensate for the lack of energy density of the supercapacitor.

[0047] Optional, please refer to Figure 3 and Figure 4 The tower crane variable frequency drive system provided by the embodiment of the present invention can also adopt a discrete control drive solution. For example, the supercapacitor and energy storage system can be directly connected to the DC bus of a single mechanism inverter to achieve the above-mentioned energy storage and release process. Figure 4 Similarly, the slewing mechanism variable frequency drive system and the luffing mechanism variable frequency drive system can also refer to the configuration of the lifting mechanism variable frequency drive system.

[0048] Figure 5 This is a flow chart of a control method for a tower crane variable frequency drive system provided by an embodiment of the present invention. The control method for a tower crane variable frequency drive system is applied to the tower crane control system of the tower crane variable frequency drive system. Please refer to Figure 5 , the control method for the tower crane variable frequency drive system may include the following steps:

[0049] Step S110: monitoring the status of the motor connected to the main drive system.

[0050] Step S120: monitor the voltage of the DC bus.

[0051] Step S130: When the voltage of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U H0 When the energy storage module and the energy storage system are controlled to store the electric energy of the DC bus, and the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0052] Preferably, controlling the energy storage module and the energy storage system to store the electric energy of the DC bus may include: sending an electric energy storage instruction to control the energy storage module to store the electric energy of the DC bus, the DC / DC bidirectional DC converter responding to the electric energy storage instruction and controlling the conversion system to charge the supercapacitor from the DC bus; and controlling the inverter control unit to send a boost instruction to control the energy storage system to store the electric energy of the DC bus, the drive unit of the energy storage system responding to the boost instruction and driving the motor of the energy storage system to perform work, so as to convert the electric energy of the DC bus into work and then store it.

[0053] For example, when the operation of the main drive system causes the DC bus voltage to exceed the preset value U H0 During the operation, the tower crane control system controls the energy storage module and the energy storage system to store the electrical energy of the DC bus. Among them, the power storage instruction can be sent to the DC / DC bidirectional DC converter to charge the supercapacitor. At the same time, a lifting instruction is sent to the drive unit of the energy storage system. The drive unit of the energy storage system drives the load lifting mechanism to lift the load structure, continuously consuming the electrical energy on the DC bus to avoid the overvoltage fault of the inverter module caused by the continuous rise in voltage, and can convert the regenerated electrical energy into potential energy (potential energy) for storage. Since the supercapacitor has a high power density, it can quickly absorb electrical energy, smooth out the feedback electrical energy impact at the moment of startup or the initial stage of speed change, and can store electrical energy. However, due to the energy density limitation of the supercapacitor, after the startup feedback current tends to be flat, the regenerated electrical energy is mainly absorbed and stored by the energy storage system.

[0054] Preferably, the control method for tower crane variable frequency drive system may further include: when the voltage drop of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

[0055] Preferably, controlling the energy storage module and the energy storage system to release electric energy to the DC bus may further include: sending an electric energy release instruction to control the energy storage module to release electric energy to the DC bus, the DC / DC bidirectional DC converter responding to the electric energy release instruction and controlling the supercapacitor to release electric energy to the DC bus; and controlling the inverter control unit to send a decrease instruction to control the energy storage system to release electric energy to the DC bus, the drive unit of the energy storage system responding to the decrease instruction and driving the motor of the energy storage system to operate, and releasing the electric energy converted by regenerative braking to the DC bus.

[0056] For example, when the operation of the main drive system causes the DC bus voltage to drop by more than U L0 The embodiment of the present invention can also control the energy storage module and the energy storage system to release electric energy to the DC bus. Among them, an electric energy release instruction can be sent to the DC / DC bidirectional DC converter to control the supercapacitor to release electric energy to the DC bus, and the inverter control unit can be controlled to send a descending instruction to the drive unit of the energy storage system. The drive unit of the energy storage system responds to the descending instruction and drives the load lifting mechanism to lower the load structure to release electric energy to the DC bus and pump up the DC bus voltage. Optionally, the DC / DC bidirectional DC converter can be controlled to release electric energy from the supercapacitor first, and then the inverter control unit can be controlled to send a descending instruction to the drive unit of the energy storage system to drive the load lifting mechanism to lower the load structure to release the stored potential energy to reserve the storage capacity of the supercapacitor as much as possible.

[0057] The voltage of the DC bus in the inverter must be stable within a certain range to work normally. Its upper voltage threshold (also called overvoltage alarm threshold) U H , lower voltage threshold (also called undervoltage alarm threshold) U L In the embodiment of the present invention, in order to prevent the DC bus from being over / under-voltage alarmed due to transient changes of the motor connected to the main drive system, which may cause the inverter to shut down, the DC bus can be monitored in real time so that the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L Between: When the main drive system is running and the DC bus voltage rises above U H0 During the startup phase, the energy storage module and the energy storage system store the electrical energy of the DC bus. Since the energy storage system has a startup process, its ability to store (absorb) electricity gradually builds up over a certain period of time. Therefore, during the startup phase, the supercapacitors of the energy storage module are controlled to increase the electricity absorption capacity and quickly suppress the voltage rise of the DC bus. When the main drive system is running and the voltage of the DC bus drops by more than U L0When the energy storage module and the energy storage system are in operation, they need to release the electric energy to the DC bus as quickly as possible (especially giving priority to releasing the electric energy of the supercapacitor in the energy storage module) to reserve sufficient storage capacity as much as possible.

[0058] Furthermore, when the operating state of the main drive system (the connected motor) suddenly changes or the external power supply voltage fluctuates violently, it may also cause disturbances in the DC bus voltage. To avoid the occurrence of overvoltage / undervoltage alarms that cause the inverter to stop running, the embodiment of the present invention may further include: during the energy storage process, when the DC bus voltage drops by more than U L1 When the DC bus voltage continues to drop by more than U L2 When the DC bus voltage continues to drop and exceeds U L3 When the voltage of the DC bus returns to U, the energy storage module and the energy storage system are immediately turned on to release power to the DC bus to avoid triggering the undervoltage alarm. L3 During the energy release process, when the DC bus voltage rises above U H1 When the DC bus voltage continues to rise and exceeds U H2 When the DC bus voltage continues to rise and exceeds U H3 When the voltage of the DC bus drops to U, the energy storage module and the energy storage system are immediately turned on to absorb power from the DC bus to avoid triggering an overvoltage alarm. H3 Below, stop absorbing electricity.

[0059] Accordingly, the control method for a tower crane variable frequency drive system provided by the embodiments of the present invention, based on the aforementioned tower crane variable frequency drive system, utilizes common DC bus technology and combines supercapacitors and an energy storage system to store regenerative braking energy in the supercapacitors and energy storage system, thereby avoiding the waste of regenerative braking energy and reducing the impact of thermal pollution on the environment. Furthermore, when the motor connected to the main drive system needs to consume electrical energy to perform work, the stored energy can be released for use by the motor connected to the main drive system, thus conserving and efficiently utilizing regenerative braking energy.

[0060] An embodiment of the present invention further provides a tower crane control system, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the computer program to implement the above-mentioned control method for the tower crane variable frequency drive system.

[0061] An embodiment of the present invention further provides a machine-readable storage medium having instructions stored thereon, the instructions enabling a machine to execute the above-mentioned control method for a tower crane variable frequency drive system.

[0062] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0063] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0064] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0065] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1A step that specifies a function in one or more boxes.

[0066] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0067] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0068] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory media such as modulated data signals and carrier waves.

[0069] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0070] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A tower crane variable frequency drive system, characterized in that: The tower crane variable frequency drive system includes a tower crane control system, a frequency converter module, an energy storage system and an energy storage module. The inverter module includes an inverter control unit, a rectifier unit connected to an external AC power supply unit, and a main drive system and a drive unit of the energy storage system connected via a DC bus. The rectifier unit is connected to the DC bus and is used to supply power to the motor connected to the main drive system through the DC bus. The energy storage module includes a supercapacitor and a DC / DC bidirectional DC converter connecting the DC bus and the supercapacitor. The tower crane control system is electrically connected to the inverter control unit and the DC / DC bidirectional DC converter, and the inverter control unit is electrically connected to the main drive system and the drive unit of the energy storage system. The tower crane control system is configured to: when the voltage of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U H0 When the energy storage module and the energy storage system are controlled to store the electric energy of the DC bus, and the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

2. The tower crane variable frequency drive system according to claim 1, characterized in that: The main drive system includes a lifting inverter unit, a slewing inverter unit and a luffing inverter unit.

3. The tower crane variable frequency drive system according to claim 1, characterized in that: The energy storage system includes a drive unit, a lifting mechanism, and a load of the energy storage system. The lifting mechanism includes a motor and a brake.

4. The tower crane variable frequency drive system according to claim 1, characterized in that: When the main drive system is running and the voltage of the DC bus rises beyond the preset threshold value U H0 When the tower crane control system is further configured as follows: Sending an electric energy storage instruction to control the energy storage module to store electric energy of the DC bus, The DC / DC bidirectional direct current converter responds to the electric energy storage instruction and controls the conversion system to charge the supercapacitor from the direct current bus; as well as Controlling the inverter control unit to send a boost instruction to control the energy storage system to store the electrical energy of the DC bus, The drive unit of the energy storage system is configured to respond to the boost instruction and drive the motor of the energy storage system to perform work, so as to store the electric energy of the DC bus after converting the electric energy through the work.

5. The tower crane variable frequency drive system according to claim 1, characterized in that: The tower crane control system is further configured to: when the voltage drop of the DC bus caused by the operation of the main drive system exceeds a preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

6. The tower crane variable frequency drive system according to claim 5, characterized in that: When the voltage drop of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U L0 When the tower crane control system is further configured as follows: Sending an electric energy release instruction to control the energy storage module to release electric energy to the DC bus, The DC / DC bidirectional direct current converter responds to the power release instruction and controls the supercapacitor to release power to the direct current bus; as well as Controlling the inverter control unit to send a descending instruction to control the energy storage system to release electric energy to the DC bus, The drive unit of the energy storage system is configured to respond to the descending instruction, drive the motor of the energy storage system to operate, and release the electric energy converted by regenerative braking to the DC bus.

7. A control method for a tower crane variable frequency drive system, characterized in that: The control method for the tower crane variable frequency drive system is applied to the tower crane control system of the tower crane variable frequency drive system according to any one of claims 1 to 6, and the control method for the tower crane variable frequency drive system includes: Monitor the status of the motor connected to the main drive system; Monitor the DC bus voltage; and When the voltage of the DC bus increases beyond the preset threshold value U H0 When the energy storage module and the energy storage system are controlled to store the electric energy of the DC bus, and the voltage of the DC bus is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

8. The control method for tower crane variable frequency drive system according to claim 7, characterized in that: The controlling the energy storage module and the energy storage system to store the electric energy of the DC bus comprises: Sending an electric energy storage instruction to control the energy storage module to store electric energy of the DC bus, The DC / DC bidirectional direct current converter responds to the electric energy storage instruction and controls the conversion system to charge the supercapacitor from the direct current bus; and Control the inverter control unit to send a boost instruction to control the energy storage system to store the electrical energy of the DC bus, The drive unit of the energy storage system responds to the boost instruction and drives the motor of the energy storage system to perform work, so as to store the electric energy of the DC bus after converting it into work.

9. The control method for tower crane variable frequency drive system according to claim 7, characterized in that: The control method for the tower crane variable frequency drive system also includes: When the voltage drop of the DC bus caused by the operation of the main drive system exceeds the preset threshold value U L0 When the energy storage module and the energy storage system are controlled to release electric energy to the DC bus, the DC bus voltage is stabilized at the upper voltage threshold U H and the lower voltage threshold U L between.

10. The control method for tower crane variable frequency drive system according to claim 9, characterized in that: The controlling the energy storage module and the energy storage system to release electric energy to the DC bus further includes: Sending an electric energy release instruction to control the energy storage module to release electric energy to the DC bus, The DC / DC bidirectional direct current converter responds to the power release instruction and controls the supercapacitor to release power to the direct current bus; and Control the inverter control unit to send a descending instruction to control the energy storage system to release electric energy to the DC bus, The drive unit of the energy storage system responds to the descending instruction, drives the motor of the energy storage system to operate, and releases the electric energy converted by regenerative braking to the DC bus.

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