CN210807129U - Rectifier and low-voltage inverter array power supply system - Google Patents

Abstract

The utility model provides a rectifier and low-voltage inverter array power supply system provides required electric energy for entire system through the form that adopts phase-shifting transformer and shared bus, and this just can simplify the structure of system to adopt the structural style of each rectifier and a plurality of inverter group link, also can simplify entire system's hardware configuration, in the reduction of system manufacturing cost, improve the reliability of system.

Description

Rectifier and low-voltage inverter array power supply system

Technical Field

The utility model relates to a variable frequency power supply technical field especially relates to a rectifier and low-voltage inverter array power supply system.

Background

With the rapid development of scientific technology and industrialization level in China, the industrial energy level in China is always kept about 70%, wherein the power consumption of a motor system accounts for more than 60% of the industrial power consumption in China, and the motor system is obviously higher than a foreign energy consumption structure. How to meet the continuously and rapidly growing energy demand and realize the clean and efficient utilization of energy is a serious challenge currently faced by China. Energy conservation and consumption reduction are strategic ideas of energy development in China; the energy efficiency improvement is a fundamental way for solving the energy and environmental problems in China. The overall energy efficiency of the load system, especially the high-energy-consumption load system, is improved, and the energy-saving and efficiency-increasing system becomes the first choice and the necessary choice for realizing energy saving and efficiency increasing of each industrial enterprise.

At present, the oil field oil extraction in China mainly adopts a mechanical oil extraction method, and a beam pumping unit (abbreviated as a pumping unit) has the highest specific gravity in the mechanical oil extraction method. The pumping unit has irreplaceable function in crude oil extraction and is an important component for forming three-pumping of an oil field. The pumping unit is the most energy-consuming equipment in the oil field, and accounts for about 40% of the total electric load of the oil field. The pumping unit has the disadvantages of great change of load parameters, low load rate, low working efficiency and great energy consumption, and causes great waste of electric energy.

Along with the exploitation of oil field oil, the oil storage capacity of different oil field oil wells changes greatly, the liquid level in the wells gradually drops, the fullness of the pump is more and more insufficient, and the phenomenon of empty pumping of the oil pumping unit often occurs when the liquid level is insufficient. In order to solve the difficult problems of low yield well and insufficient liquid filling of an oil well pump in the oil field, the oil field mostly adopts the speed regulation control of a low-voltage (380V) frequency converter, as shown in figure 1, is used for improving the pump efficiency, reducing the mechanical impact of frequent starting and stopping of the oil pumping unit due to insufficient night volume, and has certain functions of saving energy and prolonging the service life of the oil pumping unit and accessories thereof.

The structure of the low-voltage frequency converter in the frequency-conversion speed-regulation energy-saving system of the pumping unit adopted in the prior art is shown in fig. 2, a rectification loop of the low-voltage frequency converter is six-pulse wave uncontrolled rectification, and the current contains higher harmonic current. It can cause the distortion of electric network voltage waveform when flowing through the electric network, influence electric current and load connected with it in parallel, for example: the torque of the alternating current asynchronous motor is reduced, the temperature rise is increased, the protection relay malfunctions, and the error of the measuring instrument is increased. In order to reduce the influence of the frequency converters on the power grid, a three-phase reactor is required to be added at the power supply input end of each frequency converter for inhibiting the influence of higher harmonic current on the power grid. The addition of the reactor not only increases the system input cost, introduces a fault point to reduce the system reliability, but also increases the system loss and reduces the system efficiency.

When the pumping unit works, the pumping unit does reciprocating motion up and down with fixed period to continuously pump the underground crude oil to the ground. In one stroke, the motor is periodically switched between two operation states of electric driving and electric power generation along with the rising and falling of the oil rod. In the rising process of the oil rod, the motor is in an electric state and absorbs electric energy from a power grid; in the process of descending the oil rod, the motor is in a power generation state, and potential energy needs to be converted and consumed. Aiming at the working characteristics of the oil pumping unit, a brake circuit is added in the speed regulating system (see figure 2 for details). The energy consumption that is used for generating electricity when falling the beam-pumping unit, avoid the converter direct current return circuit excessive pressure to cause the fault shutdown. By adopting resistance energy consumption braking, the system investment cost is increased, fault points are introduced, the system reliability is reduced, the sucker rod is lowered, and electric energy generated by the oil pumping unit in a power generation state is wasted.

In order to reduce energy consumption, the speed regulation and energy saving reconstruction of the oil pumping unit is very important. The oil field pumping unit has the characteristics of small power, large quantity, intermittent motor in the electric and power generation states, high control performance requirement and the like, and is particularly necessary for simplifying the power supply configuration of a system and comprehensively improving the energy utilization efficiency by combining the functional characteristics of the oil field pumping unit.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a rectifier and low-voltage inverter array power supply system has simple structure, low in production cost's characteristics.

In order to achieve the above object, the utility model provides a following scheme:

a rectifier, comprising: a plurality of groups of rectifier modules and phase-shifting transformers sharing a direct current bus;

and secondary windings of the phase-shifting transformer are respectively connected with a plurality of groups of the rectifying modules, the phase-shifting transformer is used for adjusting the voltage input into the rectifying modules, and the rectifying modules are used for forming pulse wave current.

Optionally, the rectifier module includes: a filter circuit and a rectifier circuit;

the filter circuit is connected with the rectifying circuit and is used for filtering wave crests of current in the rectifying circuit; the rectifying circuit is used for converting three-phase alternating current into direct current.

Optionally, the rectifier module further includes: inputting a power supply;

the input power supply is connected with the secondary winding of the phase-shifting transformer and is used for inputting the current output by the phase-shifting transformer.

A power supply system of a low-voltage inverter array comprises the rectifier and a plurality of inverter groups;

each rectifier is connected with a plurality of inverter groups; the rectifier is used for converting three-phase alternating current into direct current; the inverter is used for converting direct current into alternating current.

Optionally, the power supply system further includes: controlling the central group;

the control center group is respectively connected with the rectifier and the inverter group; and the control center group is used for adjusting the working state of the inverter group.

Optionally, the control center group includes a plurality of control center modules, and the number of the control center modules is the same as the number of the rectifiers;

the control center module is connected with the rectifiers in a one-to-one correspondence mode.

Optionally, the control center module includes: a main controller and a PLC;

the main controller is connected with the PLC and used for adjusting the running speed of the motor in the inverter group and the space position of the motor; and the PLC is used for adjusting the on and off of a switch between the inverter and the rectifier according to the working states of the inverter and the motor.

Optionally, the inverter group includes: a plurality of inverter modules;

the inversion module comprises a sub-controller;

the sub-controllers are respectively connected with the main controller and the motors in the inverter group; the sub-controller is used for transmitting the detected running speed of the motor and the space position of the motor to the main controller;

and the main controller generates a control instruction according to the detected running speed and the detected space position of the motor, so as to control the running speed and the space position of the motor.

Optionally, the inverter module further includes: a vacuum contactor and an inverter;

the vacuum contactor is connected with the inverter; the vacuum contactor is used for switching on or switching off the working current of the system so as to control the starting or stopping of the motor in the inverter group.

Optionally, the inverter is an IGBT inverter.

According to the utility model provides a concrete embodiment, the utility model discloses a following technological effect: the utility model provides a rectifier and low-voltage inverter array power supply system provides required electric energy for entire system through the form that adopts phase-shifting transformer and shared bus, and this just can simplify the structure of system to adopt the structural style of each rectifier and a plurality of inverter group link, also can simplify entire system's hardware configuration, in the reduction of system manufacturing cost, improve the reliability of system.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive labor.

FIG. 1 is a schematic structural diagram of a variable frequency speed regulation energy-saving system of an oil pumping unit in the prior art;

FIG. 2 is a schematic structural diagram of a low-voltage frequency converter used in a variable-frequency speed-regulating energy-saving system of a pumping unit in the prior art;

fig. 3 is a schematic structural diagram of a phase-shifting transformer according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a rectifier module according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a power supply system of a low-voltage inverter array according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of an inverter group according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a power supply system of a low-voltage inverter array according to an embodiment of the present invention.

Reference numerals:

the system comprises a high-voltage incoming cabinet 1, a rectifier 2, a phase-shifting transformer 2-1, a rectifier module 2-2, an input power supply 2-2-1, a protection circuit 2-2-2, a rectification circuit 2-2-3, a buffer circuit 2-2-4, a filter circuit 2-2-5, a brake circuit 2-2-6, a control center group 4, a main controller 3-1, a PLC3-2, an inverter group 4, a sub-controller 4-1, a vacuum contactor 4-2, an inverter 4-3 and a motor 4-4.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The utility model aims at providing a rectifier and low-voltage inverter array power supply system has simple structure, low in production cost's characteristics.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description.

For easy understanding, the english abbreviation that the whole technical solution of the present invention adopts first needs to be explained:

the explanations of English explanations such as abbreviations, English and key terms are as follows:

IGBT: an Insulated Gate Bipolar Transistor is a composite fully-controlled voltage-driven power semiconductor device consisting of BJTs (Bipolar transistors) and MOS (Insulated Gate field effect transistors), and has the advantages of both high input impedance of the MOSFETs and low conduction voltage drop of GTRs (GTRs);

KM: the vacuum contactor utilizes a vacuum arc-extinguishing chamber to extinguish arc, is used for frequently switching on and switching off normal working current, and is usually used for remotely switching on and switching off a 6kV and 380V alternating current motor which is frequently started and stopped at medium and low voltages;

HMI: HMI is an abbreviation for Human Machine Interface, also called Human-Machine Interface;

PLC: PLC control system, Programmable Logic Controller, electronic device of a kind of digital operation designed for industrial production, it adopts a kind of Programmable memory, used for its internal storage program, carry out Logic operation, sequence control, timing, count and arithmetic operation, etc. to the instruction of the user, and input/output control various types of machinery or production process through the digital or analog type;

PWM: PWM is pulse width modulation, i.e. a pulse shape with a variable duty cycle;

TCP/IP: the TCP/IP protocol (transmission control protocol/internet protocol) is not simply a protocol but a special set of protocols including: TCP, IP, UDP, ARP, etc., which are referred to as sub-protocols. Among the most important, most well known, of these protocols are TCP and IP.

The utility model provides a specific technical scheme as follows:

a rectifier, comprising: a plurality of groups of rectifier modules 2-2 and phase-shifting transformers 2-1 sharing a direct current bus;

and secondary windings of the phase-shifting transformer 2-1 are respectively connected with a plurality of groups of the rectifier modules 2-2, and the phase-shifting transformer 2-1 is used for adjusting the voltage input into the rectifier modules 2-2. The specific structure of the phase-shifting transformer 2-1 is shown in fig. 3.

Fig. 4 is a schematic structural diagram of a rectifier module according to an embodiment of the present invention, as shown in fig. 4, the rectifier module 2-2 includes: a filter circuit 2-2-5 and a rectification circuit 2-2-3;

the filter circuit 2-2-5 is connected with the rectification circuit 2-2-3, and the filter circuit 2-2-5 is used for filtering wave crests of current in the rectification circuit 2-2-3.

Rectifier 2 is the utility model discloses the core part of whole design, it specifically includes 3n group common direct current bus rectifier module 2-2, and every group rectifier module 2-2 all connects in the secondary winding of mobile transformer through vacuum contactor 4-2, and any a set of rectifier module 2-2 takes place to transship, overflows the fault and all can cut off the trouble group through this vacuum contactor 4-2 that the group disposed to guarantee other equipment normal work in the common direct current bus formula low-voltage inverter array.

The utility model discloses in, one set of rectifier 2 can be shared to the beam-pumping unit in the on-the-spot certain limit of oil field (generally refer to the scope that the radius is 500 meters), and a plurality of rectifier module 2-2 in each rectifier 2 mainly including: an input power supply 2-2-1, a protection circuit 2-2-2, a rectification circuit 2-2-3, a buffer circuit 2-2-4, a filter circuit 2-2-5 and a brake circuit 2-2-6.

Wherein, an input power supply 2-2-1 is connected with a secondary winding of the phase-shifting transformer 2-1 so as to provide a proper power supply for the rectifier 2 through the dry type phase-shifting transformer 2-1 with the triangle phase-shifting.

The protection circuit 2-2-2 comprises a contactor and a fuse, and when the common direct current bus rectifier 2, or an inverter 4-3 dragged by the common direct current bus rectifier 2, or a motor 4-4 and the like are overloaded (125%, 1 minute, 180%, 3 seconds), the fault part is cut off by the contactor after time delay is judged by software; when the common direct current bus rectifier 2, or the inverter 4-3 carried by the common direct current bus rectifier, or the motor 4-4, and the like have phase-to-phase and relative short-circuit faults, the fuse can quickly cut off the fault part so as to ensure that other common direct current bus rectifiers 2 and the carried inverters 4-3 can work normally.

The rectifier circuit 2-2-3 adopts a three-phase uncontrolled rectifier bridge to convert three-phase alternating current into direct current and provide power for the rectifier 2;

and the buffer circuit 2-2-4 comprises a contactor and a current limiting resistor to prevent the rectifier bridge from being damaged by power-on impact. In the working process, the contactor is disconnected, the resistor is connected in series into a loop for current limiting, the time is delayed by 10s, the contactor is closed after electrification is finished, and the electrified resistor is in short circuit.

And the filter circuit 2-2-5 comprises an electrolytic capacitor and a voltage-sharing resistor and is used for filtering wave crests in a direct-current loop rectified by a three-phase rectifier bridge in the rectification circuit 2-2-3.

The braking circuit 2-2-6 comprises a resistor and a contactor and is used for generating electric energy by descending power generation when all motors 4-4 carried by the common direct current bus rectifier 2 are not consumed.

The capacity of the whole rectifier 2 can be determined according to the number, power and accounting of the pumping units required to be regulated and controlled on site. Specifically, if the number of the pumping units in the region is enough, the direct-current output bus of the rectifier 2 can supply power for a plurality of inversion loops, so that a bus power supply mode shared by a plurality of inversion loops is formed. The power of the pumping unit in an electric state and a power generation state is basically balanced by coordinately controlling the up-down stroke of the pumping unit carried by the rectifier 2, so that the energy efficiency is improved, and the energy consumption is reduced. If the number of the pumping units in the area is insufficient or the oil storage capacity of the oil field changes, and the number of the operating pumping units is insufficient, the rectifier 2 direct current output bus in the area can be connected with another rectifier 2 direct current output bus nearby to form a plurality of sets of rectifiers 2 common direct current buses for the pumping units in a plurality of areas to work, so that the energy efficiency is improved, and the energy consumption is reduced.

Fig. 5 is a schematic structural diagram of a power supply system of a low-voltage inverter array according to an embodiment of the present invention, and as shown in fig. 5, a power supply system of a low-voltage inverter 4-3 array includes the rectifier 2 and the plurality of inverter groups 4.

Each rectifier 2 is connected with a plurality of inverter groups 4; the rectifier is used for converting three-phase alternating current into direct current. The inverter is used for converting direct current into alternating current.

The power supply system further includes: controlling the central group 3;

the control center group 3 is respectively connected with the rectifier 2 and the inverter group 4; and the control center group 3 is used for adjusting the working state of the inverter group 4.

The control center group 3 is a brain of a common direct current bus type low-voltage frequency converter array, and comprises control center modules with the same number as the rectifiers 2, and the control center modules are connected with the rectifiers 2 in a one-to-one correspondence mode.

Each set of control center module comprises a touch screen, a PLC3-2 and a main controller 3-1.

The PLC3-2 adopts Siemens Smart series PLC3-2, and is used for collecting and controlling the state of a contactor in the whole system to complete system logic control. The PLC3-2 is provided with 18 input/12 output switching values, when the input and output points of the switching values are insufficient, the switching value modules (EMDE08(8 in), EMDR08(8 out) or EMDR16(8 in +8 out)) can be expanded to obtain the on-off state of the direct current input contactor of the inverter group 4 in the jurisdiction and control the on-off state of the contactor according to the protection command of the main controller 3-1.

The touch screen is used as a man-machine interaction window, can display the fault alarm and real-time running state of all the inverter groups 4 driven by the rectifier module 2-2 served by the touch screen in real time, completes the function adjustment of each inverter group 4, and sets parameters, and is a window for the rectifier module 2-2 and all the inverter groups 4 driven by the touch screen to communicate with an operator.

The main controller 3-1 is used as the core of the control center, mainly adopts a high-performance BKD05 controller, and comprises a DSP2812, an FPGA and a digital logic circuit, the main controller 3-1 calculates and generates an operation model rapidly according to the operation speed, the current magnitude and the like of each motor 4-4, and transmits the operation model to the sub-controllers 4-1 of each inverter group 4 through a parallel (FPGA) for execution (the technology on which the controller depends is the conventional technology in the prior art in which the controller controls the operation speed of the motor). The main controller 3-1 calculates and controls the on and off of the IGBT of each inverter 4-3 in real time by the FPGA according to the operation data and the alarm data of each inverter 4-3 transmitted by each sub-controller 4-1, thereby realizing the directional vector control of the speed rotor of each pumping unit; the operation speed and the space position of each motor are adjusted in real time according to the current and the direction of the motor 4-4 carried by each inverter group 4, so that the power energy of the pumping unit driven by the rectifier 2 is fully utilized (as shown in figure 6). The control center is communicated with the 4-3 sub-controllers 4-1 and the control center of each inverter in a real-time and rapid mode in a transmission control protocol (TCP/IP) mode.

The inverter group 4 further includes: a sub-controller 4-1;

the sub-controller 4-1 is respectively connected with the main controller 3-1 and a motor 4-4 in the inverter group 4; the sub-controller 4-1 is used for transmitting the detected running speed of the motor 4-4 and the detected space position of the motor 4-4 to the main controller 3-1 and controlling the running speed and the space position of the motor 4-4 according to a control instruction sent by the main controller 3-1.

The inverter group 4 includes a plurality of inverter modules, and each inverter module includes: a vacuum contactor 4-2, an inverter 4-3, drive hardware and a sub-controller 4-1;

the vacuum contactor 4-2 is connected with the inverter 4-3; the vacuum contactor 4-2 is used for switching on or off the working current of the system so as to control the starting and stopping of the motor 4-4 in the inverter group 4.

The controllable inverter is a power inversion part of the inverter 4-3, and the part consists of a three-phase controllable rectification loop consisting of IGBTs, a switch and a fuse. The switch is used for independently powering up the inverter module, and an obvious breakpoint is formed during a fault. The fuse is used for short-circuit protection of the inverter module and the rear end of the inverter module, and timely cuts off a fault part from a system when the fault occurs, so that the reliability of the system is improved.

The driving hardware completes the driving of each IGBT PWM waveform and the IGBT current driving protection;

in addition, the number of the rectifier modules 1 and the number of the rectifier modules n in fig. 5 are n, and 1 and n of the inverter and the motor are the same.

As shown in fig. 7, the sub-controller 4-1 is composed of a control module, a PWM output, a TCP/IP interface, a current sensor interface, an encoder interface, an operator interface, an I/O interface, etc.; the sub-controller 4-1 receives the coordination control signal from the upper-level centralized control center through a TCP/IP interface, generates PWM and transmits the PWM output to PWM driving hardware;

each motor 4-4 is independently provided with a current sensor and an encoder, a current sensor interface is used for detecting the running current of the motor 4-4 nearby, and an encoder interface is used for detecting the rotating speed of the motor 4-4 nearby and transmitting a signal to a central controller group for coordination control;

the operator interface of the whole power supply system is provided with keys for starting, stopping, resetting, emergency stopping and the like so as to facilitate the side control of the client.

Furthermore, the utility model provides a power supply system still includes high tension switchgear 1. A high-voltage power supply 10kV or 06kV for a user to enter a home supplies power to a phase-shifting transformer 2-1 of a common direct-current bus type low-voltage frequency converter array through a high-voltage switch cabinet 1; the integrated protection configured in the high-voltage switch cabinet 1 is mainly used for detecting the network voltage of a power grid and whether the total load of all driven pumping units is in a normal range or not, and is used for protecting equipment from normal work.

The utility model discloses a secondary side is the power supply of system for the multi-tap dry-type transformer that prolongs limit triangle-shaped phase shift, and each group takes out one set of rectifier of bandeau and forms the energy pond, adopts the sharing direct current generating line to provide the energy for multiunit IGBT dc-to-ac converter. The incoming line power supply of the rectifier does not need to provide an incoming line reactor independently to reduce pollution of harmonic waves to a power grid, a plurality of inversion parts share a common direct current bus and accessories thereof, the number of frequency converter hardware of each oil pumping unit is reduced, hardware configuration is simplified, and one-time cost input is reduced while the reliability of the system is improved. And the control center coordinates the power generation and electric states of all the pumping units driven by the rectifier, so that the inverter group driven by the common direct current bus under the rectifier works in the best matching state, the service life of the resistance braking loop is prolonged, and the energy utilization rate is greatly improved.

Compared with the prior art, the utility model discloses still have following outstanding characteristics:

1. the utility model discloses first through adopt the secondary side to replace traditional power transformer to be applied to low pressure rectifier circuit array for the power supply of taking a percentage dry-type rectifier transformer that more that extend limit triangle-shaped is shifted phase, each group takes out a set of rectifier module of bandeau and forms DC power supply energy pond, and the rectification inlet wire power need not provide the inlet wire reactor again alone in order to reduce the pollution of harmonic to the electric wire netting.

2. The direct current power supply output end of each group of rectification modules can provide energy for a plurality of groups of IGBT inverters at the same time. The multiple inversion modules are connected to the output end of the rectification module and share the common direct current bus and accessories thereof to form a common direct current bus form, so that the number of frequency converter hardware of each oil pumping unit is reduced, the hardware configuration is simplified, the system reliability is improved, and the one-time investment is reduced.

3. The utility model discloses well control part adopts the distributed control mode of control maincenter + sub-controller. The speed, the power generation and the electric state of all the pumping units dragged under a certain rectifier module are conveniently and intensively regulated and controlled by the control center, so that all the inverters carried by the rectifier module work in the optimal matching state, the service life of a resistance braking loop is prolonged, and the energy utilization rate is greatly improved. Meanwhile, the sub-controller can conveniently and rapidly acquire the operation data and the fault alarm information of each inversion module, so that the reliable and safe operation of the fault-free part in the system can be ensured.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The principle and the implementation of the present invention are explained herein by using specific examples, and the above description of the embodiments is only used to help understand the method and the core idea of the present invention; meanwhile, for the general technical personnel in the field, according to the idea of the present invention, there are changes in the concrete implementation and the application scope. In summary, the content of the present specification should not be construed as a limitation of the present invention.

Claims (10)

1. A rectifier, comprising: a plurality of groups of rectifier modules and phase-shifting transformers sharing a direct current bus;

and secondary windings of the phase-shifting transformer are respectively connected with a plurality of groups of the rectifying modules, the phase-shifting transformer is used for adjusting the voltage input into the rectifying modules, and the rectifying modules are used for forming pulse wave current.

2. A rectifier according to claim 1 wherein said rectifier module comprises: a filter circuit and a rectifier circuit;

the filter circuit is connected with the rectifying circuit and is used for filtering wave crests of current in the rectifying circuit; the rectifying circuit is used for converting three-phase alternating current into direct current.

3. A rectifier according to claim 1 wherein said rectifier module further comprises: inputting a power supply;

the input power supply is connected with the secondary winding of the phase-shifting transformer and is used for inputting the current output by the phase-shifting transformer.

4. A power supply system for a low voltage inverter array, characterized in that it comprises a plurality of rectifiers as claimed in any one of claims 1 to 3 and a plurality of inverter groups;

each rectifier is connected with a plurality of inverter groups; the rectifier is used for converting three-phase alternating current into direct current; the inverter is used for converting direct current into alternating current.

5. The system according to claim 4, characterized in that it further comprises: controlling the central group;

the control center group is respectively connected with the rectifier and the inverter group; and the control center group is used for adjusting the working state of the inverter group.

6. The system of claim 5, wherein the control hub group comprises a plurality of control hub modules, and the number of control hub modules is the same as the number of rectifiers;

the control center module is connected with the rectifiers in a one-to-one correspondence mode.

7. The system of claim 6, wherein the control hub module comprises: a main controller and a PLC;

the main controller is connected with the PLC and used for adjusting the running speed of the motor in the inverter group and the space position of the motor; and the PLC is used for adjusting the on and off of a switch between the inverter and the rectifier according to the working states of the inverter and the motor.

8. The system according to claim 7, characterized in that said inverter group comprises: a plurality of inverter modules;

the inversion module comprises a sub-controller;

the sub-controllers are respectively connected with the main controller and the motors in the inverter group; the sub-controller is used for transmitting the detected running speed of the motor and the space position of the motor to the main controller;

and the main controller generates a control instruction according to the detected running speed and the detected space position of the motor, so as to control the running speed and the space position of the motor.

9. The system according to claim 8, wherein said inverter module further comprises: a vacuum contactor and an inverter;

the vacuum contactor is connected with the inverter; the vacuum contactor is used for switching on or switching off the working current of the system so as to control the starting or stopping of the motor in the inverter group.

10. The system of claim 9, wherein the inverters are IGBT inverters.

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