Uninterrupted operation frequency conversion device and control method

Abstract

The invention relates to the technical field of frequency conversion control, and particularly discloses an uninterrupted operation frequency conversion device and a control method. Comprising an input power supply 1, an input power supply 2, a first change-over switch K1, a second change-over switch K2, a 1 # rectifier, a 2 # rectifier, a 1 # inverter, a 2 # inverter, a third change-over switch K3, a fourth change-over switch K4, a control system power supply single board, an input voltage detection and switch control single board, a 2 # rectifier, a 2 # inversion signal acquisition and processing single board, and a 1 # rectifier and 1 # inversion signal acquisition and processing single board. The frequency conversion device supports input connection of two paths of alternating current power supplies and is respectively connected to two sections of buses, when one path of power supply fails, the frequency conversion device can be quickly switched to a standby power supply, and when one group of rectifiers or inverters in the frequency conversion device fails, the frequency conversion device can be quickly switched to the other group of rectifiers or inverters in the frequency conversion device. And continuous operation of the equipment is ensured through rapid switching.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency conversion control, and more specifically, to an uninterrupted operation frequency conversion device and a control method. Background Art

[0002] In many industrial scenarios, motors need to run continuously under load and are usually critical to the process. If these devices stop unexpectedly, it may cause production process interruption, equipment damage, and even threaten personnel safety. Therefore, these scenarios place strict requirements on the stability and continuous operation of frequency conversion control equipment, especially when power supply or equipment failure occurs, it is necessary to maintain uninterrupted and stable operation as much as possible.

[0003] The existing technology uses a "one in use and one in standby" inverter solution, that is, two sets of inverter devices are configured through two bus sections, one of which is used for work and the other is used as a standby. When a fault occurs, the standby device is put into operation. In manual mode, the input of the standby inverter usually requires manual switching by the operator, which takes 5 to 10 minutes and easily causes a long downtime. In automatic mode, the equipment can automatically switch within 1 to 2 seconds. This solution meets most on-site applications, but for high-load occasions, such as mining equipment and metallurgical production, if the power supply cannot be restored in time after the equipment fails, the equipment may be difficult to restart due to heavy load shutdown, resulting in serious losses. The "one in use and one in standby" solution is difficult to meet the continuous power supply needs of these scenarios. In high-risk industries such as chemical and energy, once the equipment is shut down, it may not only cause production interruptions, but also cause environmental pollution and worker safety threats. Summary of the invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides an uninterrupted operation frequency conversion device and control method, which is designed with a rectifier and inverter with dual power supply input and redundant backup, combined with a mechanical switching switch with a switching speed of less than 5ms, to achieve millisecond-level switching of key equipment in the event of a fault, thereby ensuring continuous power supply. Once the control system detects a fault, it immediately isolates the faulty module and switches the load to the backup module to ensure that the equipment runs without stopping, thereby solving the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A non-stop frequency conversion device supports input connection of two AC power supplies, which are respectively connected to two bus sections. When one power supply fails, the frequency conversion device can quickly switch to the backup power supply to ensure the continuous operation of the motor. The frequency conversion device is configured with redundant dual power supplies, and independent switching switch controls, independent rectifiers and inverters are set for online maintenance and replacement of various components. The closing time of the first switching switch K1, the second switching switch K2, the third switching switch K3 and the fourth switching switch K4 of the frequency conversion device is controlled within 5ms.

[0007] As a further solution of the present invention, the left end of the first switching switch K1 is connected to the input power supply 1, the input power supply 1 is the first input AC power supply, which is connected to a bus section 1, the left end of the second switching switch K2 is connected to the input power supply 2, the input power supply 2 is the second input AC power supply, which is connected to a bus section 2, the left end of the output power supply is respectively connected to the third switching switch K3 and the fourth switching switch K4, and the right end of the output power supply is connected to the load motor.

[0008] As a further solution of the present invention, the right end of the first switching switch K1 is connected to the 1# rectifier, and the right end of the second switching switch K2 is connected to the 2# rectifier. The 1# rectifier and the 2# rectifier convert the AC power of the input power supply into DC power. The right end of the 1# rectifier is connected to the 1# inverter, and the right end of the 2# rectifier is connected to the 2# inverter. The 1# inverter and the 2# inverter invert the rectified DC power into AC power and output it to the output power supply.

[0009] As a further solution of the present invention, the frequency conversion device includes a control system power supply board, input voltage detection and switch control, 2# rectifier 2# inverter signal collection and processing board, 1# rectifier 1# inverter signal collection and processing board, output switch control board and control system.

[0010] As a further solution of the present invention, the control system is respectively connected to the control system power supply board, the input voltage detection and switch control, the 2# rectifier 2# inverter signal collection and processing board, the 1# rectifier 1# inverter signal collection and processing board and the output switch control board.

[0011] As a further solution of the present invention, the control system power supply board takes two phases of the first input AC power supply and the second input AC power supply, which ensures that the control system works normally when one power supply is abnormal. The input voltage detection and switch control board detects the voltage signals of the first input AC power supply and the second input AC power supply, transmits them to the control system, and receives the control instructions of the control system for the first switching switch K1 and the second switching switch K2, completes the switching action of the first switching switch K1 and the second switching switch K2, and the 2# rectifier 2# inverter signal acquisition and processing board and the 1# rectifier 1# inverter signal acquisition and processing board respectively complete the power supply corresponding to the 1# rectifier, the 2# rectifier, the 1# inverter and the 2# inverter. The control system is responsible for the signal collection of the voltage, current, temperature and fault feedback signal light of the 2# rectifier 2# inverter signal collection and processing board and the 1# rectifier 1# inverter signal collection and processing board receiving the signal of the control part for processing, and completing the execution of commands such as IGBT inverter drive, fan control, power-on buffer, etc. The control system is responsible for the fault detection and signal processing of the 1# rectifier, the 2# rectifier, the 1# inverter and the 2# inverter, and generates a synchronous SPWM signal according to the fault situation to ensure that the load motor maintains the same frequency and phase during fault switching. The output switch control board receives the instructions of the control system for the third switching switch K3 and the fourth switching switch K4, and completes the switching action execution of the third switching switch K3 and the fourth switching switch K4.

[0012] As a further solution of the present invention, the first input AC power supply and the second input AC power supply are equipped with a voltage device, which can monitor the voltage conditions of the two power supplies in real time. Once an abnormality in the main power supply is detected, it will quickly switch to the backup power supply to ensure uninterrupted power supply.

[0013] As a further solution of the present invention, the first switching switch K1 and the second switching switch K2 have a mechanical ATSE structure, which achieves the switching speed of the STS static switch. The switching speed can be within 5ms, and the input power can be quickly switched.

[0014] As a further solution of the present invention, the 1# rectifier and the 2# rectifier use diode rectification, and contain a power-on buffer part inside, which functions to convert AC power into DC power.

[0015] As a further solution of the present invention, electrolytic capacitors are integrated inside the 1# inverter and the 2# inverter to invert the rectified direct current into alternating current.

[0016] As a further solution of the present invention, the control chip of the control system is a DSP, which completes the calculation and processing of all collected signals and controls the operation of the uninterrupted frequency conversion device.

[0017] As a further solution of the present invention, a control method for an uninterrupted frequency conversion device after a power supply line is lost includes the following specific steps:

[0018] Step S1, when the control system detects that the power supply of the bus section 1 is abnormal, it immediately issues an instruction to close the fourth switch K4, and the inverter #2 is ready to be put into operation, and the closing time of the fourth switch K4 is controlled within 5ms;

[0019] Step S2, after the fourth switch K4 is closed, the control system sends an SPWM control signal synchronized with the 1# inverter to the 2# inverter to keep the frequency and phase of the output power consistent, so as to achieve a smooth transition of the load motor;

[0020] Step S3, the control system detects whether the 2# inverter outputs current normally. When confirming that the 2# inverter has current output, it issues an instruction to disconnect the third switch K3, so that the 1# inverter stops running, and the load motor is driven by the 2# inverter.

[0021] Step S4, the control system continues to monitor the power recovery of the bus section 1. When the power of the bus section 1 returns to normal, the control system will automatically switch back to the 1# inverter. The specific operation process is that when the power of the bus section 1 returns to normal, the load motor will be switched from the 2# inverter back to the 1# inverter to ensure uninterrupted power supply.

[0022] As a further solution of the present invention, a control method for an uninterruptedly running frequency conversion device in the event of a failure of a group of rectifiers and their control circuits comprises the following specific steps:

[0023] Step Z1, when the control system detects that the No. 1 rectifier or its control circuit fails, it immediately issues an instruction to disconnect the first switch K1 to prevent the failure from spreading to other circuits;

[0024] Step Z2, the control system synchronously issues an instruction to close the fourth switch K4, and switches the load motor to the 2# inverter within 5 ms;

[0025] Step Z3, when the fourth switch K4 is closed, the control system sends a synchronous SPWM control signal to the 2# inverter to keep the frequency and phase of the output current consistent with the 1# inverter, so as to ensure that the load motor maintains a smooth transition during the switching process;

[0026] Step Z4, the control system monitors the current output of the 2# inverter, and after confirming that the output of the 2# inverter is normal, issues an instruction to disconnect the third switch K3, so that the 1# inverter stops running, and the load motor is taken over by the 2# inverter;

[0027] Step Z5, after the fault switching is completed, the 1# rectifier and its control loop are completely out of service and can be maintained and replaced. The control system continues to monitor the operation of the first input AC power source, the second input AC power source and the 2# inverter to ensure the normal operation of the system.

[0028] As a further solution of the present invention, a control method for an uninterruptedly operating frequency conversion device in the event of a failure of a group of inverters and their control circuits comprises the following specific steps:

[0029] Step Y1, when the control system detects that the 1# inverter or its control circuit fails, it immediately issues a command to disconnect the first switch K1 and the third switch K3 at the same time to cut off the power connection of the 1# inverter to prevent the failure from affecting other circuits;

[0030] Step Y2, the control system calculates frequency and phase compensation values ​​according to the deceleration characteristics and fault current of the load motor to ensure that the frequency and phase output by the 2# inverter are consistent with those of the 1# inverter when taking over;

[0031] Step Y3, after calculating the compensation value, the control system blocks the output of the 2# inverter and closes the fourth switch K4 for 5 ms to prepare to switch the load of the load motor to the 2# inverter;

[0032] Step Y4, after the 5ms timing is completed, the control system issues a command, and the 2# inverter starts to output current with the compensated frequency and phase, and takes over the drive control of the load motor;

[0033] Step Y5, the fault switching is completed, and the control system continues to monitor the operating status of the 2# inverter and monitors the recovery of the 1# inverter fault so that after the 1# inverter is repaired, the load motor operation is restored to the 1# inverter.

[0034] The technical effects and advantages of the uninterrupted operation frequency conversion device and control method of the present invention: The present invention improves the fault tolerance and continuous power supply capability of the system through the design of dual power input, redundant backup rectifier and inverter modules, combined with the application of mechanical high-speed switching switches. The control system can monitor the status of each module in real time and switch to the backup module within milliseconds, ensuring that in the event of a power failure or equipment failure, the load can be smoothly and seamlessly transferred to the backup power supply or device, avoiding equipment shutdown caused by short shutdowns, heavy load startup difficulties and other problems. The modular and automated design of the device allows each component to be repaired and replaced online, effectively improving the flexibility of maintenance and the reliability of the system. At the same time, the present invention overcomes the shortcomings of the existing "one-in-one-backup" solution in high-load and high-risk application scenarios, ensures the continuous and safe operation of the equipment, helps reduce the risk of production interruptions, and provides key guarantees in industries such as mining, metallurgy, and chemical industry that have extremely high requirements for equipment stability and continuity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a structural schematic diagram of an uninterrupted operation frequency conversion device.

[0036] Figure 2 The present invention is a flow chart of a control method of a non-stop frequency conversion device after one power supply line is lost.

[0037] Figure 3 The present invention is a flow chart of a control method of a non-interruptible frequency conversion device after one power supply path is lost in a machineless main mode.

[0038] Figure 4 The present invention is a flowchart of a control method of an uninterruptible operation device in the event of a group of rectifiers and their control circuit failures.

[0039] Figure 5 The present invention is a flow chart of a control method of an uninterrupted operation device in the event of a group of inverters and their control circuit failures. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] See also Figure 1As shown in the structural schematic diagram, an embodiment of the present invention provides an uninterrupted operation frequency conversion device, the frequency conversion device supports the input connection of two AC power supplies, which are respectively connected to two bus sections. When one power supply fails, the frequency conversion device can quickly switch to the backup power supply to ensure the continuous operation of the motor; the frequency conversion device includes an input power supply 1 and an input power supply 2, the input power supply 1 is a first input AC power supply, and the left end of the first input AC power supply is connected to a bus section 1; the input power supply 2 is a second input AC power supply, and the left end of the second input AC power supply is connected to a bus section 2; the right end of the first input AC power supply is connected to K1, and K1 is a first switching switch, and the right end of the second input AC power supply is connected to K2 The first switching switch K1 is connected to the 1# rectifier at the right end, and the second switching switch K2 is connected to the 2# rectifier at the right end; the 1# rectifier and the 2# rectifier convert the AC power of the input power supply into DC power, the right end of the 1# rectifier is connected to the 1# inverter, and the right end of the 2# rectifier is connected to the 2# inverter, and the 1# inverter and the 2# inverter invert the rectified DC power into AC power and output it to the load motor; the right end of the 1# inverter is connected to K3, and K3 is the third switching switch, and the 2# inverter is connected to K4, and K4 is the fourth switching switch, and the third switching switch K3 and the fourth switching switch K 4 are respectively connected to the output power supply, and the output power supply is connected to the load motor; the frequency conversion device includes a control system power supply single board, and the control system power supply single board takes two phases of the first input AC power supply and the second input AC power supply, which ensures that the control system works normally when one power supply is abnormal, and the frequency conversion device includes an input voltage detection and switch control single board, and the input voltage detection and switch control single board detects the voltage signals of the first input AC power supply and the second input AC power supply, transmits them to the control system, and receives the control instructions of the control system for the first input switching switch K1 and the second input switching switch K2, and completes the first input switching switch K1 and the second input The switching action of the input switching switch K2 is executed; the frequency conversion device includes a 2# rectifier, 2# inverter signal acquisition and processing single board and a 1# rectifier, 1# inverter signal acquisition and processing single board, the 2# rectifier 2# inverter signal acquisition and processing single board and the 1# rectifier 1# inverter signal acquisition and processing single board respectively complete the signal acquisition of the voltage, current, temperature and fault feedback signal light corresponding to the 1# rectifier, 2# rectifier, 1# inverter and 2# inverter; at the same time, the 2# rectifier 2# inverter signal acquisition and processing single board and the 1# rectifier 1# inverter signal acquisition and processing single board receive the signal of the control part for processing, and complete the execution of IGBT inverter drive, fan control, power-on buffer and other commands;The frequency conversion device includes a control system, which is responsible for fault detection and signal processing of the 1# rectifier, 2# rectifier, 1# inverter, and 2# inverter, and generates a synchronous SPWM signal according to the fault condition to ensure that the load motor maintains the same frequency and phase during fault switching; the frequency conversion device also includes an output switch control single board, which receives the control system's instructions for the third switch K3 and the fourth switch K4, and completes the switching action execution of the third switch K3 and the fourth switch K4. ;

[0043] In this embodiment, under normal working conditions, the first switching switch K1 and the second switching switch K2 are both closed, the 1# rectifier and the 2# rectifier perform uncontrolled rectification, and the two input switches are closed at the same time to ensure the switching response speed when one of the input switches fails. At the same time, the control system sends a fully synchronized SPWM control signal to the 1# inverter and the 2# inverter at the same time, the third switching switch K3 is closed, and the fourth switching switch K4 is disconnected, and the 1# inverter runs with load. The third switching switch K3 and the fourth switching switch K4 are not closed at the same time, ensuring complete electrical isolation of the two groups of inverters, avoiding the joint damage of the other group when one group of inverters fails.

[0044] Example 2

[0045] See also Figure 2 As shown in the flowchart, an embodiment of the present invention provides a control method for an uninterrupted frequency conversion device after one power supply line is lost, including the following contents:

[0046] After the frequency conversion device detects that the power supply of the first section of bus is abnormal, the control system controls the fourth switch K4 to close. The closing time of the fourth switch K4 is 5ms, which can ensure that the second inverter is put into operation when the first section of bus drops to the undervoltage point. Because the control system sends synchronous SPWM control signals to the first inverter and the second inverter, the two inverter outputs have the same frequency and phase, which can realize the transfer of the load motor control from the first inverter to the second inverter. After the control system detects that the second inverter has current, it determines that the second inverter is successfully switched, and sends a disconnection instruction of the third switch K3, and the load motor is controlled by the second inverter.

[0047] Since the 1# rectifier and the 1# inverter are the hosts by default, the control system will detect the power recovery of the 1# bus in real time. After the 1# bus is restored, the control system will switch to the 1# inverter.

[0048] Correspondingly, the frequency conversion device can set the 2# rectifier and the 2# inverter as the host and non-host modes. The switching control method without the host can refer to Figure 3 After the frequency converter detects that the power supply of the bus section 1 is abnormal, the control system controls the fourth switch K4 to close. The closing time of the fourth switch K4 is 5ms, which can ensure that the 2# inverter is put into operation when the bus section 1 drops to the undervoltage point; because the control system sends synchronous SPWM control signals to the 1# inverter and the 2# inverter, the two inverter outputs have the same frequency and phase, which can realize the transfer of the load motor control from the 1# inverter to the 2# inverter; after the control system detects that the 2# inverter has current, it determines that the 2# inverter is successfully switched, and sends the third switch K3 disconnection instruction, the load motor is controlled by the 2# inverter, and waits for the 2# rectifier and the second circuit where the 2# inverter is located to fail before switching back to the first circuit where the 1# rectifier and the 1# inverter are located.

[0049] In this embodiment, the 5ms closing time satisfies the switching of the inverter. The specific theoretical analysis includes the following: the three-phase full-wave diode rectifier circuit converts the AC voltage into a pulsating DC voltage, and the capacitor connected across the DC bus can reduce the voltage pulsation. When the external voltage cannot be charged, the voltage drop of the capacitor is a typical exponential function:

[0050]

[0051] In the formula, t is time, P n is the output power of the load motor, P n satisfy Where cosφ=0.85,η=0.95,C is the capacitance value, C satisfies C=kI e , where the value of k is generally 40-50μF / A, U0 is the maximum value of the DC charging voltage, when the power supply voltage is AC380V, U0 is DC540V, if the ripple factor of the pulsating voltage of the DC bus is 5%, then DC540V*0.95=513V, therefore, τ satisfies:

[0052]

[0053] From the above formula, we can know that the discharge time constant τ is only related to the capacitance and power supply voltage, and has nothing to do with the inverter power. When the power grid loses power or the voltage drops, the DC bus voltage is higher than the AC side voltage. At this time, the diode is subjected to reverse voltage and does not conduct. The AC side cannot provide energy to the DC side. At this time, the electric field energy stored on the capacitor C The output of energy causes the voltage on the capacitor to drop while maintaining the operation of the load motor. At τ, the voltage drops by about 36% of U0. That is, when the DC voltage u(t) drops to 70% of U0, the frequency converter reports an overvoltage fault, so that the capacitor no longer continues to provide energy to the motor, and the remaining voltage is maintained at 0.7 times U0. From the equation Solve for time t, the formula for time t is:

[0054]

[0055] The relationship between the inverter's capacitance, time constant and allowable discharge time is shown in the following table:

[0056] Capacitor charge unit Time constant τ=495.75k Discharge time t = 177.32k k=40μF / A ms 19.83 7.09 k=50μF / A ms 24.79 8.87

[0057] In the above table, U e =380V / ac, cosφ=0.85, η=0.95, coefficient k is configured as (40-50)μF / A, U0 is the maximum DC voltage value of the capacitor, 540V, considering the 5% ripple factor, U0=540*0.95=513V, U is 70% of U0, it can be seen that the switching time of 5ms meets the requirements of continuous motor control.

[0058] Example 3

[0059] See also Figure 4 As shown in the flowchart, an embodiment of the present invention provides a control method for an uninterruptible operation device in the event of a group of rectifiers and their control circuit failures, including the following contents:

[0060] After the frequency conversion device detects that the 1# rectifier is abnormal, the control system controls the first switch K1 of the 1# bus to be disconnected to prevent the expansion of the fault caused by the 1# rectifier fault. The control system controls the first switch K1 to be disconnected and controls the fourth switch K4 to be closed. The closing action time of the fourth switch K4 is 5ms, which can ensure that the 2# inverter is put into operation before the 1# bus falls to the undervoltage point. Since the control system sends synchronous SPWM control signals to the 1# inverter and the 2# inverter, the two inverter outputs have the same frequency and phase, which can realize the control of the load motor by the The transfer of the 1# inverter to the 2# inverter, after the control system detects that the 2# inverter has current, determines that the 2# inverter is switched successfully, sends the disconnection command of the third switch K3, and the load motor is controlled by the 2# inverter, the fault switching control ends, the 1# rectifier and the 1# inverter are completely withdrawn, and can be repaired and replaced. After the fault of the 1# rectifier is completely eliminated, the control system controls the first switch K1 to close, waits for the second circuit where the 2# rectifier and the 2# inverter are located to fail, and then switches back to the first circuit where the 1# rectifier and the 1# inverter are located. The fault control method of the 1# rectifier sampling and signal processing board is consistent with the rectifier control method and will not be described in detail.

[0061] Example 4

[0062] See also Figure 5As shown in the flowchart, the embodiment of the present invention provides a control method for an uninterrupted operation device in the case of a group of inverters and their control circuit failures, including the following contents: the switching logic when the inverter fails is different from the above two methods, and the inverter device needs to learn the characteristics of the load motor during the initialization power-on process, including the deceleration characteristics within 5ms under various current level loads, which are used for the speed frequency attenuation of the load motor after the load motor is completely powered off during the inverter switching process, and then calculate the frequency compensation value and phase compensation value required for the load motor to lose power under different load conditions. When the 1# inverter fails abnormally, the control system disconnects the first switching switch K1 and the third switching switch K3, and blocks the output of the 2# inverter at the same time. The control system calculates the frequency and phase compensation values ​​according to the deceleration characteristics of the load motor and the fault current, performs SPWM modulation to obtain the power supply U required to be output by the 2# inverter after 5ms, and then closes the fourth switching switch K4 to start timing. When the time reaches 5ms after the fault occurs, the 2# inverter outputs the power supply U to control the load motor to run with load. The fault control method of the inverter sampling and signal processing part in the first circuit where the 1# rectifier and the 1# inverter are located is consistent with the rectifier control method and will not be described in detail.

[0063] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0064] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An uninterrupted operation frequency conversion device supports the input connection of two AC power supplies, which are respectively connected to two bus sections. When one power supply fails, the frequency conversion device can quickly switch to the backup power supply to ensure the continuous operation of the motor, characterized in that: The frequency conversion device is configured with redundant dual power supplies, independent switch control, independent rectifier and inverter for online maintenance and replacement of various components. The closing time of the first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 of the frequency conversion device is controlled within 5ms.

2. The uninterrupted frequency conversion device according to claim 1, characterized in that: The left end of the first switching switch K1 is connected to the input power supply 1, which is the first input AC power supply and is connected to a bus section 1. The left end of the second switching switch K2 is connected to the input power supply 2, which is the second input AC power supply and is connected to a bus section 2. The left ends of the inverter outputs of the two groups of frequency conversion devices are respectively connected to the third switching switch K3 and the fourth switching switch K4, and the right ends of the outputs are connected to the load motor.

3. The uninterrupted frequency conversion device according to claim 2, characterized in that: The right end of the first switching switch K1 is connected to the 1# rectifier, and the right end of the second switching switch K2 is connected to the 2# rectifier. The 1# rectifier and the 2# rectifier convert the AC power of the input power supply into DC power. The right end of the 1# rectifier is connected to the 1# inverter, and the right end of the 2# rectifier is connected to the 2# inverter. The 1# inverter and the 2# inverter invert the rectified DC power into AC power and output it to the output power supply.

4. The uninterrupted frequency conversion device according to claim 3, characterized in that: The frequency conversion device includes a control system power supply board, input voltage detection and switch control, 2# rectifier 2# inverter signal collection and processing board, 1# rectifier 1# inverter signal collection and processing board, output switch control board and control system.

5. The uninterrupted frequency conversion device according to claim 4, characterized in that: The control system is connected to the control system power supply board, the input voltage detection and switch control, the 2# rectifier 2# inverter signal collection and processing board, the 1# rectifier 1# inverter signal collection and processing board and the output switch control board respectively.

6. The uninterrupted operation frequency conversion device according to claim 5, characterized in that: The control system power supply board takes two phases of the first input AC power supply and the second input AC power supply, which ensures that the control system works normally when one power supply is abnormal. The input voltage detection and switch control board detects the voltage signals of the first input AC power supply and the second input AC power supply, transmits them to the control system, and receives the control instructions of the control system for the first switching switch K1 and the second switching switch K2, completes the switching action of the first switching switch K1 and the second switching switch K2, and is responsible for fault detection and signal processing of the 1# rectifier, the 2# rectifier, the 1# inverter, and the 2# inverter, and generates a synchronous SPWM signal according to the fault situation to ensure that the load motor maintains the same frequency and phase during fault switching.

7. The uninterrupted frequency conversion device according to claim 6, characterized in that: The 2# rectifier 2# inverter signal acquisition and processing single board and the 1# rectifier 1# inverter signal acquisition and processing single board respectively complete the signal acquisition of the voltage, current, temperature and fault feedback signal light corresponding to the 1# rectifier, the 2# rectifier, the 1# inverter and the 2# inverter. At the same time, the 2# rectifier 2# inverter signal acquisition and processing single board and the 1# rectifier 1# inverter signal acquisition and processing single board receive the signal of the control part for processing, and complete the execution of IGBT inverter drive, fan control and power-on buffer commands. The 1# rectifier and the 2# rectifier use diode rectification, which contains a power-on buffer part. The output switch control single board receives the control system's instructions for the third switch K3 and the fourth switch K4, and completes the switching action execution of the third switch K3 and the fourth switch K4.

8. A control method for continuously operating a frequency conversion device, characterized in that: A control method for an uninterrupted frequency conversion device according to any one of claims 1 to 7 after a power supply line is lost comprises the following steps: Step S1, when the control system detects that the power supply of the bus section 1 is abnormal, it immediately issues an instruction to close the fourth switch K4, and the inverter #2 is ready to be put into operation, and the closing time of the fourth switch K4 is controlled within 5ms; Step S2, after the fourth switch K4 is closed, the control system sends an SPWM control signal synchronized with the 1# inverter to the 2# inverter to keep the frequency and phase of the output power consistent, so as to achieve a smooth transition of the load motor; Step S3, the control system detects the output current of the 2# inverter, and when confirming that the 2# inverter has current output, issues an instruction to disconnect the third switch K3, so that the 1# inverter stops running, and the load motor is driven by the 2# inverter; Step S4, the control system continues to monitor the power recovery of the bus section 1. When the power of the bus section 1 returns to normal, the control system will automatically switch back to the 1# inverter. The specific operation process is: when the power of the bus section 1 returns to normal, the load motor is switched from the 2# inverter back to the 1# inverter to ensure uninterrupted power supply.

9. A control method for continuously operating a frequency conversion device, characterized in that: A control method for an uninterrupted frequency conversion device according to any one of claims 1 to 7 in the event of a failure of a group of rectifiers and their control circuits comprises the following steps: Step Z1, when the control system detects that the No. 1 rectifier or its control circuit fails, it immediately issues an instruction to disconnect the first switch K1 to prevent the failure from spreading to other circuits; Step Z2, the control system synchronously issues an instruction to close the fourth switch K4, and switches the load motor to the 2# inverter within 5 ms; Step Z3, when the fourth switch K4 is closed, the control system sends a synchronous SPWM control signal to the 2# inverter to keep the frequency and phase of the output current consistent with the 1# inverter, so as to ensure that the load motor maintains a smooth transition during the switching process; Step Z4, the control system monitors the current output of the 2# inverter, and after confirming that the output of the 2# inverter is normal, issues an instruction to disconnect the third switch K3, so that the 1# inverter stops running, and the load motor is taken over by the 2# inverter; Step Z5, after the fault switching is completed, the 1# rectifier and its control loop are completely exited for maintenance and replacement, and the control system continues to monitor the operation of the first input AC power supply, the second input AC power supply and the 2# inverter to ensure the normal operation of the system.

10. A control method for continuously operating a frequency conversion device, characterized in that: A control method for an uninterrupted frequency conversion device according to any one of claims 1 to 7 in the event of a failure of a group of inverters and their control circuits comprises the following steps: Step Y1, when the control system detects that the 1# inverter or its control circuit fails, it immediately issues a command to disconnect the first switch K1 and the third switch K3 at the same time to cut off the power connection of the 1# inverter to prevent the failure from affecting other circuits; Step Y2, the control system calculates frequency and phase compensation values ​​according to the deceleration characteristics and fault current of the load motor to ensure that the frequency and phase output by the 2# inverter are consistent with those of the 1# inverter when taking over; Step Y3, after calculating the compensation value, the control system blocks the output of the 2# inverter and closes the fourth switch K4 for 5 ms to prepare to switch the load of the load motor to the 2# inverter; Step Y4, after the 5ms timing is completed, the control system issues a command, and the 2# inverter starts to output current with the compensated frequency and phase, and takes over the drive control of the load motor; Step Y5, the fault switching is completed, and the control system continues to monitor the operating status of the 2# inverter and monitors the recovery of the 1# inverter fault so that after the 1# inverter is repaired, the load motor operation is restored to the 1# inverter.

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