Common direct current bus multi-stage inversion parallel speed regulation system of crane

Abstract

The utility model discloses a common direct current bus multi-stage inversion parallel speed regulation system of a crane. The common direct current bus multi-stage inversion parallel speed regulation system comprises a switch, a touch screen, a PLC, a plurality of rectification units, a parallel operation module, a rectification control module and a plurality of inverters. According to the utility model, a plurality of rectification units are used in parallel and are matched with the parallel operation module, so that the problem that the power of a single rectification unit cannot meet the power of complete equipment is solved, the output power is improved, extensive expandability is achieved, and the impact on a power grid is greatly reduced; the system has two control modes of communication control and terminal control, the PLC and each inverter adopt a PN bus communication mechanism through the Ethernet to realize communication control, the on-off state of a relay coil connected with an output module of the PLC is controlled through a manual operator to realize terminal communication, and when system communication fails, the terminal control mode can be switched through parameter setting, so that the system communication failure is avoided. Redundancy of two control modes is achieved, and safe operation of equipment is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of crane control, in particular to a crane common DC bus multi-level inverter parallel speed regulation system. Background Art

[0002] Cranes are special equipment that work in special and complex working conditions. In particular, cranes are often used to transport ladles in the metallurgical industry. However, due to the high temperature of the working environment, the safety, reliability and service life of the crane's electronic control system are highly required. A better speed control system suitable for metallurgical cranes in high temperature environments will effectively ensure the safe operation of the crane.

[0003] At present, there are mainly the following methods for crane motor speed control:

[0004] 1. Series resistance speed regulation: Series resistance speed regulation is a low speed regulation. The switching of the rotor series resistance is completed by the opening and closing of the contactor, thereby adjusting the speed of the motor. Because it is a step-by-step speed regulation, the speed changes suddenly when the resistance is switched, which has a great impact on the reduction box, coupling and wire rope, affecting the service life. The hoisted workpiece also has shaking and impact, which cannot meet the stability requirements of the hoisted workpiece.

[0005] 2. Stator voltage regulation and speed regulation: Stator voltage regulation and speed regulation belongs to high speed regulation, which changes the stator voltage by adjusting the thyristor conduction angle, so as to achieve the purpose of controlling the motor speed. The whole system implements closed-loop control to achieve constant speed regulation, reduce the impact on the reduction box and motor, reduce the current peak, thereby extending the service life of the motor, increase the speed slip loss in the process of speed regulation, make the rotor heat up, and reduce the efficiency;

[0006] 3. Frequency converter speed regulation: This speed regulation method mainly configures frequency converters for each mechanism of the crane, and controls the speed of the motor by changing the output voltage and frequency of the frequency converter. The advantage of this method is the overall low cost, and the disadvantage is that it has an impact on the power grid when the load is started. It is mostly used to drive electric loads with general power.

[0007] 4. In places with a higher safety factor, active rectification solutions are often used. The main principle is: use centralized rectification multi-inverter circuits in parallel on the DC bus, adjust the speed of the transmission devices of each mechanism by changing the voltage and frequency of the inverter, and at the same time, feed back the energy generated during the braking process of each mechanism to the power grid to achieve energy saving. However, the energy fed back to the power grid is relatively low for cranes, and the cost of this solution is relatively high. There is a huge gap between the cost of saved electricity and the purchase cost of the equipment. Utility Model Content

[0008] The technical problem to be solved by the utility model is to overcome the existing defects and provide a crane common DC bus multi-stage inverter parallel speed control system, which solves the problem that the power of a single rectifier unit cannot meet the power of the entire equipment, improves the output power, has wide scalability, and greatly reduces the impact on the power grid; it has two control modes: communication control and terminal control. When the system communication fails, it can switch to the terminal control mode, realizing the redundancy of the two control modes, ensuring the safe operation of the equipment, and can effectively solve the problems in the background technology.

[0009] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a crane common DC bus multi-level inverter parallel speed control system, including a switch, a touch screen, a PLC, a plurality of rectifier units, a parallel module, a rectifier control module and a plurality of inverters;

[0010] The switch and the touch screen are connected to the PLC via PN communication, the PLC is connected to the parallel module via PN communication, the parallel module receives the control signal of the PLC, the rectifier control module is connected to the multiple inverters via optical fiber communication, the rectifier control module synchronously sends the control signal received by the parallel module to the multiple inverters via optical fiber communication, the multiple inverters correspondingly change the output voltage and frequency to realize the speed control of the motor, and at the same time the rectifier control module feeds back the operating parameters of the multiple inverters to the parallel module, and the parallel module transmits the operating parameters of the multiple inverters to the touch screen via the PLC;

[0011] The rectifier unit is used to rectify the AC voltage on the grid side into a DC voltage. Multiple rectifier units are connected in parallel and provide DC voltage to multiple inverters through a DC bus. The inverter converts the DC voltage into AC voltage to rotate the motor. The parallel module is connected to the multiple rectifier units through optical fiber communication, and the parallel module synchronizes and controls the current sharing of the multiple rectifier units. The DC bus is also connected in series with a braking unit and a corresponding braking resistor.

[0012] Preferably, it also includes a hand operator, which is a control signal giving device. The hand operator is connected to the switch via PN communication. The hand operator sends the control command to the PLC via the switch, and the output module of the PLC energizes the corresponding relay.

[0013] Preferably, the output module of the PLC includes relay K13, relay K12, relay K11, relay K10, relay K01 and relay K02.

[0014] Preferably, the rectifier control module is connected in series with the normally open contact of relay K01, and when the normally open contact of relay K01 is closed, the rectifier control module starts; the rectifier control module is connected in series with the normally open contact of relay K02, and when the normally open contact of relay K02 is closed, a feedback signal is input into the rectifier control module, and the rectifier control module outputs a confirmation instruction to the parallel module, and the rectifier unit starts working.

[0015] Preferably, the inverter is also connected to the switch via PN communication, and the inverter is connected in series with the normally open contact of relay K13. When the normally open contact of relay K13 is closed, the inverter operation is allowed; the inverter is connected in series with the normally open contact of relay K12. When the normally open contact of relay K12 is closed, the inverter communication is switched; the inverter is connected in series with the normally open contact of relay K11. When the normally open contact of relay K11 is closed, the inverter controls the motor to reverse; the inverter is connected in series with the normally open contact of relay K10. When the normally open contact of relay K10 is closed, the inverter controls the motor to rotate forward.

[0016] Preferably, a fast fuse is connected in series to the power input terminal of the inverter.

[0017] Compared with the prior art, the beneficial effects of the utility model are as follows: multiple rectifier units are used in parallel and equipped with parallel modules, which solves the problem that the power of a single rectifier unit cannot meet the power of the entire equipment, improves the output power, has wide scalability, and greatly reduces the impact on the power grid; adopts the "basic rectifier + multi-transmission inverter" method, and the system can realize two control modes: communication control and terminal control; the control circuit contains a PLC that uses a PN bus communication mechanism with each inverter through Ethernet, and a terminal control mode is designed at the same time, which realizes terminal communication by controlling the on and off state of the relay coil connected to the output module of the PLC. When the system communication fails, it can be switched to the terminal control mode through parameter settings, realizing the redundancy of the two control modes and ensuring the safe operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a system block diagram of the utility model;

[0019] Figure 2 This is the electrical block diagram of the rectifier of the utility model;

[0020] Figure 3 This is the electrical block diagram of the inverter of the utility model;

[0021] Figure 4 This is a schematic diagram of the handheld operator and PLC control of the utility model.

[0022] In the figure: 1 switch, 2 touch screen, 3 PLC, 4 rectifier unit, 5 parallel module, 6 rectifier control module, 7 inverter, 8 brake unit, 9 brake resistor, 10 DC bus, 11 fast fuse, 12 hand operator. DETAILED DESCRIPTION

[0023] The present invention can be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "front", "back", "left", "right", etc. indicating directions or positional relationships, they only correspond to the drawings of the present application for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction.

[0024] See also Figure 1-4 , the utility model provides the following technical solutions:

[0025] Embodiment 1: A crane common DC bus multi-level inverter parallel speed control system, comprising a switch 1, a touch screen 2, a PLC 3, a plurality of rectifier units 4, a parallel module 5, a rectifier control module 6 and a plurality of inverters 7;

[0026] The switch 1 and the touch screen 2 are connected to the PLC 3 through PN communication, the PLC 3 is connected to the parallel module 5 through PN communication, the parallel module 5 receives the control signal of the PLC 3, the rectifier control module 6 is connected to the multiple inverters 7 through optical fiber communication, the rectifier control module 6 sends the control signal received by the parallel module 5 to the multiple inverters 7 synchronously through optical fiber communication, the multiple inverters 7 change the output voltage and frequency accordingly to realize the speed control of the motor, and at the same time the rectifier control module 6 feeds back the operating parameters of the multiple inverters 7 to the parallel module 5, and the parallel module 5 transmits the operating parameters of the multiple inverters 7 to the touch screen 2 through the PLC 3;

[0027] In the communication control mode, PLC3 communicates data with each inverter 7 through the parallel module 5 and the rectifier control module 6, so as to realize the control of the forward and reverse rotation of the motor by the inverter 7; the communication between PLC3, the parallel module 5, the rectifier control module 6 and the inverter 7 is completed without the need for external relay control;

[0028] The rectifier unit 4 is used to rectify the AC voltage on the grid side into a DC voltage. Multiple rectifier units 4 are connected in parallel and provide DC voltage to multiple inverters 7 through a DC bus 10. The inverter 7 converts the DC voltage into an AC voltage to rotate the motor. The parallel module 5 is connected to the multiple rectifier units 4 through optical fiber communication. The parallel module 5 performs synchronization and current balancing control on the multiple rectifier units 4. The DC bus 10 is also connected in series with a brake unit 8 and a corresponding brake resistor 9.

[0029] It should be noted that in the normal working mode, 380V AC power needs to be provided to the rectifier unit 4. If the power of a single rectifier unit 4 is small, the rectifier unit 4 can be expanded by parallel cascading to increase the output power. The number of rectifier units 4 can be increased according to actual needs, and it has wide scalability. When the output ends of two or more rectifier units 4 are connected in parallel and multiple rectifier units 4 are used in parallel, a parallel module 5 is required to increase the power of the whole machine. The parallel module 5 can also synchronize and balance the current of each rectifier unit 4. In addition, when the whole system is in the working mode, the motor of the crane is in the power generation state during the braking process, which causes the voltage on the DC bus 10 to increase. Considering the braking energy consumption, a braking unit 8 needs to be connected to the DC bus 10 to consume the energy through the braking resistor 9 to ensure the stable operation of the inverter 7. The braking resistor 9 matching the braking unit 8 is selected according to the braking power value.

[0030] Embodiment 2: Different from Embodiment 1, it further comprises a hand operator 12, which is a control signal giving device. The hand operator 12 is connected to the switch 1 via PN communication. The hand operator 12 sends the control instruction to the PLC 3 via the switch 1, and the output module of the PLC 3 energizes the corresponding relay.

[0031] The output module of PLC3 includes relay K13, relay K12, relay K11, relay K10, relay K01 and relay K02; the rectifier control module 6 is connected in series with the normally open contact of relay K01, and when the normally open contact of relay K01 is closed, the rectifier control module 6 starts; the rectifier control module 6 is connected in series with the normally open contact of relay K02, and when the normally open contact of relay K02 is closed, the feedback signal is input into the rectifier control module 6, and the rectifier control module 6 outputs a confirmation instruction to the parallel module 5, and the rectifier unit 4 starts working; the inverter 7 also Connected with switch 1 via PN communication, inverter 7 is connected in series with the normally open contact of relay K13, when the normally open contact of relay K13 is closed, inverter 7 is allowed to run; inverter 7 is connected in series with the normally open contact of relay K12, when the normally open contact of relay K12 is closed, inverter 7 communication is switched; inverter 7 is connected in series with the normally open contact of relay K11, when the normally open contact of relay K11 is closed, inverter 7 controls the motor to reverse; inverter 7 is connected in series with the normally open contact of relay K10, when the normally open contact of relay K10 is closed, inverter 7 controls the motor to rotate forward;

[0032] When the system communication fails, it can be switched to terminal control mode through parameter setting, that is, the control command is sent to PLC3 through the handheld operator 12, and the output module of PLC3 energizes the corresponding relay. For example, the handheld operator 12 controls the relay K12 to be energized. When the normally open contact of the relay K12 is closed, the communication of the inverter 7 is switched, that is, the communication control is switched to the terminal control. The handheld operator 12 can control the inverter 7 to control the forward and reverse rotation of the motor. In addition, the handheld operator 12 can also control the rectifier control module 6 to start the rectifier control module 6, and control the rectifier unit 4 to start through the rectifier control module 6; the redundancy of the two control modes is realized, and the safe operation of the equipment is ensured;

[0033] In addition, a fast fuse 11 is connected in series to the power supply line end of the inverter 7 to prevent the front end from causing damage to the rear end inverter.

[0034] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and it is intended to include all changes that fall within the meaning and scope of equivalent elements in the content of the present invention.

Claims

1. A crane common DC bus multi-level inverter parallel speed control system, characterized by: It comprises a switch (1), a touch screen (2), a PLC (3), a plurality of rectifier units (4), a parallel module (5), a rectifier control module (6) and a plurality of inverters (7); The switch (1) and the touch screen (2) are connected to the PLC (3) via PN communication, the PLC (3) is connected to the parallel module (5) via PN communication, the parallel module (5) receives control signals from the PLC (3), the rectifier control module (6) is connected to the plurality of inverters (7) via optical fiber communication, the rectifier control module (6) synchronously sends the control signals received by the parallel module (5) to the plurality of inverters (7) via optical fiber communication, the plurality of inverters (7) correspondingly change the output voltage and frequency to achieve motor speed control, and at the same time the rectifier control module (6) feeds back the operating parameters of the plurality of inverters (7) to the parallel module (5), and the parallel module (5) transmits the operating parameters of the plurality of inverters (7) to the touch screen (2) via the PLC (3); The rectifier unit (4) is used to rectify the AC voltage on the grid side into a DC voltage. A plurality of rectifier units (4) are connected in parallel and provide a DC voltage to a plurality of inverters (7) via a DC bus (10). The inverter (7) converts the DC voltage into an AC voltage to rotate the motor. The parallel module (5) is connected to the plurality of rectifier units (4) via optical fiber communication. The parallel module (5) performs synchronization and current balancing control on the plurality of rectifier units (4). The DC bus (10) is also connected in series with a brake unit (8) and a corresponding brake resistor (9).

2. The crane common DC bus multi-level inverter parallel speed control system according to claim 1 is characterized by: It also includes a hand operator (12), which is a control signal giving device. The hand operator (12) is connected to the switch (1) via PN communication. The hand operator (12) sends a control instruction to the PLC (3) via the switch (1), and the output module of the PLC (3) energizes the corresponding relay.

3. The crane common DC bus multi-level inverter parallel speed control system according to claim 2 is characterized by: The output module of the PLC (3) comprises a relay K13, a relay K12, a relay K11, a relay K10, a relay K01 and a relay K02.

4. The crane common DC bus multi-level inverter parallel speed control system according to claim 3 is characterized by: The rectifier control module (6) is connected in series with the normally open contact of the relay K01. When the normally open contact of the relay K01 is closed, the rectifier control module (6) is started. The rectifier control module (6) is connected in series with the normally open contact of the relay K02. When the normally open contact of the relay K02 is closed, a feedback signal is input into the rectifier control module (6). The rectifier control module (6) outputs a confirmation instruction to the parallel module (5), and the rectifier unit (4) starts to work.

5. The crane common DC bus multi-level inverter parallel speed control system according to claim 3 is characterized by: The inverter (7) is also connected to the switch (1) via PN communication. The inverter (7) is connected in series with a normally open contact of a relay K13. When the normally open contact of the relay K13 is closed, the inverter (7) is allowed to operate. The inverter (7) is connected in series with a normally open contact of a relay K12. When the normally open contact of the relay K12 is closed, the inverter (7) switches communication. The inverter (7) is connected in series with a normally open contact of a relay K11. When the normally open contact of the relay K11 is closed, the inverter (7) controls the motor to rotate in reverse. The inverter (7) is connected in series with a normally open contact of a relay K10. When the normally open contact of the relay K10 is closed, the inverter (7) controls the motor to rotate in the forward direction.

6. The crane common DC bus multi-level inverter parallel speed control system according to claim 1 is characterized by: A fast fuse (11) is connected in series to the power supply input terminal of the inverter (7).

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