A method and device for automatically switching frequency conversion when a primary fan frequency converter fails

Abstract

The present invention provides a method and device for automatic frequency conversion switching of a primary fan inverter when it fails. The method utilizes DCS logic control and designs multiple logic controls to obtain a fault signal of the primary fan inverter and send a serious fault alarm signal of the inverter; receives the fault signal of the primary fan inverter, starts the DCS control logic, and controls the inverter outlet to trip the 6KV side main switch; receives the 6KV side switch position feedback signal, performs frequency conversion and automatic switching of the working frequency, and simultaneously tracks the pressure and temperature in the furnace in real time and performs real-time detection on them.

Description

Technical Field

[0001] The present disclosure relates to the technical field of frequency conversion switching, and in particular to a method and device for automatic frequency conversion switching of a fan inverter due to a fault. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] The frequency converter uses frequency conversion technology and microelectronics technology to control the power control device of the AC motor by changing the working power frequency of the motor. It is mainly composed of rectification (AC to DC), filtering, inversion (DC to AC), braking unit, drive unit, detection unit and microprocessor unit.

[0004] The inverter adjusts the voltage and frequency of the output power supply by the opening and closing of the internal IGBT, and provides the required power supply voltage according to the actual needs of the motor, thereby achieving the purpose of energy saving and speed regulation.

[0005] Industrial frequency refers to the rated frequency of electrical equipment in the power system, which is generally 50 Hz. Frequency conversion means reducing the frequency of the AC power supply. Since the square of the frequency is proportional to the output power, the use of frequency conversion technology can effectively reduce the power used by electrical equipment, thereby achieving the purpose of energy saving and consumption reduction.

[0006] In thermal power plants, some important loads, such as primary fans and other important auxiliary equipment, have large capacity and high power consumption, and are in continuous operation, low load and variable load for a long time. Reducing the frequency can reduce energy consumption, and the resulting economic benefits are very considerable. Therefore, the site often adopts the method of installing frequency converters to reduce motor energy consumption, reduce plant power consumption, automatically control furnace pressure, stabilize the power supply, etc. Since these important auxiliary equipment are often high-voltage electrical equipment above 6kV, and domestic high-voltage frequency conversion technology is limited, various faults of frequency converters often occur during operation. For example, under normal circumstances, the primary fan is variable frequency operation. Once the frequency converter fails and trips, the unit immediately sheds 50% of the load, and at the same time Enter RB state and rescue the unit. However, since the primary fan is an important auxiliary machine, it involves a large number of systems and devices that require rapid adjustment, and the probability of successful rescue is less than 10%. The unplanned shutdown of the unit caused by the inverter failure has a single assessment economic indicator of more than one million yuan. The consequence of the primary fan shutdown caused by the inverter failure is very serious. When a major failure occurs in the frequency conversion device, the primary fan needs to be switched from the variable frequency state to the industrial frequency operation state. Generally, during the switching of the variable frequency state, the amplitude of the air volume change during the switching of the existing technology is relatively large, which affects the combustion stability of the boiler, thereby causing excessive changes in the furnace pressure and air volume, resulting in an unstoppable accident, affecting the safety and stability of power production. Summary of the invention

[0007] In order to solve the above problems, the present invention proposes a method and device for automatic frequency switching when a primary fan inverter fails. The present invention provides a variety of variable switching logics to ensure that automatic switching is only performed when the inverter fails, which serves as a backup protection for serious inverter failures and prevents the unit from directly shutting down the boiler when the inverter fails, causing shutdown.

[0008] According to some embodiments, the present disclosure adopts the following technical solutions:

[0009] A method for automatic frequency conversion switching of a primary fan inverter fault, comprising the following steps:

[0010] Collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and send out the inverter serious fault alarm signal;

[0011] Receive the fault signal of the primary fan inverter, start the DCS control logic, and control the inverter outlet to trip the 6KV side main switch;

[0012] Receive the switch position feedback signal on the 6KV side and automatically switch to the power frequency by frequency conversion;

[0013] During the switching process, the furnace operating status is tracked in real time to obtain normal signals of pressure and temperature inside the furnace. Otherwise, the RB logic state is immediately entered to rescue the unit.

[0014] Furthermore, during switching, the DCS control opens the high-voltage main switch on the 6kV side, then opens the first contactor of the input contactor on the inverter side and the second contactor of the output contactor on the inverter side, sets a time period, first closes the third contactor of the industrial frequency input contactor, and then closes the main switch on the 6kV side to complete the electrical switching.

[0015] According to other embodiments, the present disclosure also adopts the following technical solutions:

[0016] A primary fan inverter fault automatic frequency switching device, comprising:

[0017] Frequency converter, a power control device used to control AC motors, mainly consists of rectification, filtering, inversion, braking unit, drive unit, detection unit and microprocessing unit;

[0018] The sensor is used to collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and issue a serious fault alarm signal of the inverter;

[0019] The DCS control system is used to receive the fault signal of the primary fan inverter, start the DCS control logic, control the inverter outlet to trip the 6KV side main switch, and receive the 6KV side switch position feedback signal to perform frequency conversion and automatic switching of the power frequency;

[0020] Contactor, used for switch closing in frequency conversion and power frequency switching logic control.

[0021] It also includes a circuit breaker and a motor. The circuit breaker realizes arc extinguishing during the frequency conversion to power frequency switching process, and the motor realizes the operation of the entire power system.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The design of the variable switching logic of the primary fan inverter is carried out through logical control in various situations. When the inverter device fails, the variable switching logic is realized, which prevents the occurrence of MFT boiler fire extinguishing accidents of the unit, maintains the stable operation of the power system, and reduces the impact caused by non-stop accidents.

[0024] DCS control effectively observes the switching process, tracks furnace air temperature, air pressure, combustion conditions and other indicators in real time, effectively realizes the on-off control of high-voltage equipment switches, and monitors the operating conditions of the unit. At the same time, after the frequency conversion is switched to the working frequency, when the primary fan output suddenly increases, it avoids furnace explosion and affects the safe operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure.

[0026] Figure 1 is a schematic diagram of a DCS control system disclosed in the present invention;

[0027] Figure 2 is a block diagram of the electrical switching logic of the present disclosure;

[0028] Figure 3 It is a schematic diagram of the logic of automatic switching to the working frequency when the primary fan inverter fails in the present disclosure;

[0029] Figure 4 It is the RB logic diagram of the frequency conversion switching power frequency failure startup disclosed in the present invention;

[0030] Figure 5 This is a logic diagram of the primary fan outlet valve action after the primary fan frequency conversion is switched to the working frequency;

[0031] Figure 6 It is a schematic diagram of the switch control logic of the 6KV side of the primary fan disclosed in the present invention; DETAILED DESCRIPTION

[0032] The present disclosure is further described below in conjunction with the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present disclosure belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Example 1

[0036] In thermal power plants, some important loads, such as primary fans and other important auxiliary equipment, have large capacity and high power consumption, and are in continuous operation, low load and variable load for a long time. Reducing the frequency can reduce energy consumption, and the resulting economic benefits are very considerable. Therefore, the site often uses the method of installing a frequency converter to reduce motor energy consumption, achieve the purpose of reducing plant power consumption, automatically controlling furnace pressure, and stabilizing the power consumption rate.

[0037] Since these important auxiliary machines are often high-voltage electrical equipment above 6kV, and domestic high-voltage frequency conversion technology is limited, various faults often occur in frequency converters during operation.

[0038] Take the inverter of the primary fan in our factory as an example. Under normal circumstances, the primary fan is operated with variable frequency. Once the inverter trips due to a fault, the unit will immediately shed 50% of the load and enter the RB state to rescue the unit. However, since the primary fan is an important auxiliary machine, it involves a large number of systems and devices that require rapid adjustment, and the probability of successful rescue is less than 10%. Due to the unplanned shutdown of the unit caused by the inverter failure, the economic indicators of our factory for a single assessment are as high as more than one million yuan. Therefore, it is particularly important to prevent the shutdown of the primary fan caused by the inverter failure.

[0039] The present disclosure provides a method for automatic frequency conversion switching of a primary fan inverter failure, which performs the following steps:

[0040] Collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and send out the inverter serious fault alarm signal;

[0041] Receive the fault signal of the primary fan inverter, start the DCS control logic, and control the inverter outlet to trip the 6KV side main switch;

[0042] Receive the switch position feedback signal on the 6KV side and automatically switch to the power frequency by frequency conversion;

[0043] During the switching process, the furnace operating status is tracked in real time to obtain normal signals of pressure and temperature inside the furnace. Otherwise, the RB logic state is immediately entered to rescue the unit.

[0044] In the specific implementation, how to make the primary fan switch from the variable frequency state to the working frequency state as disturbance-free as possible when the frequency conversion device fails? We believe that a variable switching device can be added to the frequency converter bypass system, and at the same time, a set of automatic air volume adjustment logic during the variable switching process can be designed in the DCS system, so that during the switching process, the furnace pressure can be changed with the least disturbance possible to complete the primary fan motor switching process.

[0045] During the operation of a fan, when the inverter fails, how to switch the inverter from the variable frequency state to the working frequency state can be considered in several stages or situations:

[0046] When to switch, the conditions for switching, how to achieve switching, how to ensure reliable switching, what special situations need to be avoided, what to do after switching fails, and how to adjust the unit after switching. Consider the above issues, design logical control for various problems, and take effective methods to overcome the difficulties in the above problems.

[0047] (1) When to perform automatic switching

[0048] Since there are risks in switching from frequency conversion to industrial frequency, which may damage the motor and affect the normal operation of the unit, the logic of switching from frequency conversion to industrial frequency should ensure that automatic switching is performed only when the frequency converter fails, as a backup protection for serious frequency converter failures, to prevent the unit from directly shutting down the boiler when the frequency converter fails, causing shutdown.

[0049] (2) How to implement switching

[0050] Collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and issue a serious fault alarm signal of the inverter;

[0051] Receive the fault signal of the primary fan inverter, start the DCS control logic, and control the inverter outlet to trip the 6KV side main switch;

[0052] Receive the switch position feedback signal on the 6KV side and automatically switch to the power frequency by frequency conversion;

[0053] During the switching process, the furnace operating status is tracked in real time to obtain normal signals of pressure and temperature inside the furnace. Otherwise, the RB logic state is immediately entered to rescue the unit.

[0054] Because there are two ways to consider, one is the PLC control of the inverter itself, and the other is the DCS control. Since the PLC control cannot effectively observe the switching process, it is impossible to track the furnace air temperature, air pressure, combustion status and other indicators in real time. In addition, the PLC's control of the opening and closing of the high-voltage equipment switch is not reliable, and the unit's operating conditions cannot be detected, so the automatic switching success rate of the inverter is not high.

[0055] 2. The present invention adopts a DCS control method to design a method for automatically switching the power frequency with frequency conversion. During the switching process, the DCS control opens the high-voltage main switch on the 6kV side, then opens the first contactor of the input contactor on the inverter side and the second contactor of the output contactor on the inverter side, sets a time period, first closes the third contactor of the power frequency input contactor, and then closes the main switch on the 6kV side to complete the electrical switching.

[0056] Specifically, Figure 1 In the process, when the inverter has a serious fault or stops operating, the DCS controls the 6kV side high-voltage main switch to be tripped first, and then the inverter side input contactor KM1 and the inverter side output contactor KM2 to be tripped. After a short delay, the power frequency input contactor KM3 is closed first, and finally the 6kV side main switch is closed to complete the electrical switching. During this period, the DCS device tracks the furnace operation status. Once the furnace is over-pressured or deflagrated, it immediately enters the RB state to rescue the unit.

[0057] Specific analysis of the time delay of closing the 6KV side switch: after the inverter trips due to a fault, the DCS control receives the 6KV side switch position feedback signal with an inherent delay of 200ms, the time to judge and export the tripped contactor is 1s, the time to receive the closed position feedback signal of the power frequency side contactor is 200ms, the setting calculation shows that the demagnetization time of the motor is 2-3s, and a 1s delay is added to close the 6KV side switch. The switching time of the automatic frequency conversion to power frequency logic should be controlled within 5s.

[0058] (3) How to ensure reliable switching

[0059] Set up various logics and control to achieve safe switching.

[0060] During the switching process, the 6KV side switch must be protected. If the 6KV side switch is not tripped due to inverter failure, automatic switching will cause a secondary impact on the 6KV side switch power system. A NOT gate for the 6KV side switch protection action is added to the switching start logic, that is, the frequency conversion switching to industrial frequency logic is not started when the 6KV side switch protection is actuated.

[0061] When the unit is shut down, the inverter maintenance test process causes the frequency conversion to power frequency logic control, and the MFT boiler fire extinguishing protection reset signal is added to the switching start logic. When the reset signal is detected, it is ensured that the frequency conversion to power frequency control logic is not started in the shutdown state.

[0062] When the inverter is started, if a fault trip occurs before the inverter is started, the inverter position cannot be determined and the inverter cannot be put into operation. In this case, a manual start-up button for switching the inverter to the industrial frequency is added to the switching start logic to ensure that the inverter is started normally before manual start-up.

[0063] If a situation occurs that causes the frequency conversion and power frequency switching logic to be executed cyclically, and the 6KV side switch is opened and closed multiple times, the frequency conversion and power frequency switching execution will be automatically exited after the frequency conversion and power frequency switching start logic starts, ensuring that the automatic switching logic is only executed once.

[0064] The switching process was refined and the equipment and processes involved in the switching were analyzed:

[0065] 1. Action of contactors and circuit breakers: Because it involves fault switching above 6kV voltage level, it is necessary to consider the arc extinguishing ability of contactors and circuit breakers. Obviously, the arc extinguishing ability of contactors is far inferior to that of high-voltage circuit breakers, so the entire switching needs to use high-voltage circuit breakers to extinguish arcs. When the inverter fails, the inverter will trip the 6kV side main switch at the same time as issuing a serious fault alarm signal. At this time, the design should ensure that the electrical switching process is carried out after receiving the switch position signal, otherwise the primary and secondary equipment will burn out and fail due to arc extinguishing overvoltage and high current. Similarly, since the power frequency contactor has no arc extinguishing ability, it is necessary to ensure that the power frequency contactor KM3 is closed before closing the 6kV side main switch during the closing process to ensure that the 6kV side main switch is used for arc extinguishing.

[0066] 2. Motor protection: When the three-phase motor is operating normally, the main magnetic field rotating at the synchronous speed induces a symmetrical three-phase electromotive force in the three-phase winding of the stator. If the power is disconnected, the main magnetic field disappears, but the rotor core that was once magnetized by the main magnetic field still has residual magnetism. At the same time, due to inertia, the rotor still rotates at a high speed, and the induced electromotive force generated in the stator coil does not disappear in a very short time, but only decays. This requires that during the switching process, while ensuring the pressure in the furnace, the residual magnetism should be reduced as long as possible, so as not to generate a large voltage difference △U when the power frequency voltage is put into use, which will cause an impact on the motor itself and damage the motor. However, a long time means that the primary wind pressure on one side will be greatly reduced. If the time is too long, the unit boiler fire extinguishing logic will be triggered, causing the unit to stop operating, which is equivalent to expanding the accident.

[0067] We conducted an experimental analysis on this situation. After the inverter tripped due to a fault, the DCS system received the 6kV side switch position feedback signal with an inherent delay of about 200ms. The time for the logic judgment and output to trip the contactor was about 1s, and the time for receiving the closing feedback signal of the power frequency side contactor was about 200ms. The setting calculation showed that the demagnetization time of the motor was 2-3s. Therefore, on this basis, it is more reasonable to add a 1s delay to close the 6kV side switch.

[0068] 3. Protection of the primary air pressure of the unit: We have consulted a large amount of information and used the start-stop opportunities to test the unit. In order to stabilize the combustion and prevent the primary air pressure from dropping too much and causing the unit to shut down, after calculation, the automatic variable cut-off logic switching time should be controlled within 5s.

[0069] (4) Special circumstances that need to be avoided

[0070] In addition to the normal switching process above, we have also considered various special cases and designed relevant logic to avoid these problems.

[0071] 1. The 6kV side switch tripped not because of a frequency converter fault, but because of a cable, motor or switch fault. If automatic switching is performed at this time, it will cause an impact on the 6kV side switch and even the plant power system. To avoid this, we added a NOT gate for the 6kV side switch protection action in the switching start logic, that is, when the 6kV side switch protection action is actuated, switching will not be performed to ensure that there is no secondary impact on the plant power system.

[0072] 2. In order to prevent the variable switching logic from being switched incorrectly during the inverter maintenance test when the unit is shut down, we add the MFT boiler fire protection reset signal to the switching start logic, that is, to ensure that the variable switching logic is not started in the shutdown state.

[0073] 3. When the inverter is started, if the inverter trips due to a fault before starting, directly switching the power frequency at this time is not conducive to quickly finding the inverter position and putting the inverter into operation. Therefore, we add a manual input button for the inverter in the switching start logic, and the operator manually switches it on and off to ensure that the inverter is manually put into operation after normal startup to ensure the safe operation of the unit.

[0074] 4. In order to prevent the transformer switching logic from being executed cyclically due to special circumstances, causing the 6kV side switch to be opened and closed multiple times and damaging the primary equipment, we automatically exit the transformer switching execution button after the transformer switching start logic begins to ensure that the automatic switching condition is only performed once.

[0075] (5) What to do if the switch fails

[0076] The entire switching process involves various operating circuits of multiple switches, and there is a certain possibility of switching failure. If the unit RB logic is not started after the switch fails, the primary wind pressure will be further reduced, eventually causing the unit to shut down.

[0077] To avoid this situation, we have optimized the RB logic after the failure of the primary wind turbine transformer shedding logic. When the primary wind turbine switches to the power frequency state and the high-voltage switch on the 6kV side trips, the RB function of the unit is triggered with a delay; or after the transformer shedding logic is executed, if the switch on the 6kV side cannot be closed within 5s, the unit automatically enters the RB logic for rescue.

[0078] (6) How to adjust the unit after the variable shear logic is switched

[0079] After the inverter cuts to the working frequency, the primary fan output suddenly increases after the frequency reaches the rated value under the working frequency state, which will cause the wind pressure in the furnace to suddenly increase, causing wind pressure fluctuations. At the same time, it will also suddenly increase the amount of fuel entering the furnace and intensify the combustion, which will cause the unit's superheater to overheat and overpressure, and even increase the fuel delivered to the furnace due to the increase in wind pressure, destroying the configuration of the air-coal ratio, causing incomplete combustion and threatening the safety of the unit.

[0080] Therefore, during the switching process of variable shear logic, the coordination of inverter switching and damper adjustment must also be considered. As well as the difference in the action characteristics of the inverter and the damper, the inverter is not as fast as the damper in adjustment speed, which can easily cause the inverter to trip due to overcurrent during rapid action, thus threatening the safety of the unit. In order to avoid this situation, we worked with thermal engineering professionals to perform a logical design on the action of the primary fan blade damper during the switching process. Based on the wind pressure, air volume, temperature, and combustion conditions in the furnace, the exit door is controlled to ensure stable combustion inside the furnace.

[0081] Example 2

[0082] The present disclosure provides a primary fan inverter fault automatic frequency conversion switching device, comprising:

[0083] Frequency converter, a power control device used to control AC motors, mainly consists of rectification, filtering, inversion, braking unit, drive unit, detection unit and microprocessing unit;

[0084] The sensor is used to collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and issue a serious fault alarm signal of the inverter;

[0085] The DCG control system is used to receive the fault signal of the primary fan inverter, start the DCS control logic, control the inverter outlet to trip the 6KV side main switch, and receive the 6KV side switch position feedback signal to perform frequency conversion and automatic switching of the power frequency;

[0086] Contactor, used for switch closing in frequency conversion and power frequency switching logic control.

[0087] It also includes a circuit breaker and a motor, wherein the circuit breaker realizes arc extinguishing during the frequency conversion to power frequency switching process, and the motor realizes the operation of the entire power system. The above-mentioned various devices are connected to each other for communication and signal transmission.

[0088] Specifically, perform the following steps:

[0089] Collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and send out the inverter serious fault alarm signal;

[0090] Receive the fault signal of the primary fan inverter, start the DCS control logic, and control the inverter outlet to trip the 6KV side main switch;

[0091] Receive the switch position feedback signal on the 6KV side and automatically switch to the power frequency by frequency conversion;

[0092] During the switching process, the furnace operating status is tracked in real time to obtain normal signals of pressure and temperature inside the furnace. Otherwise, the RB logic state is immediately entered to rescue the unit.

[0093] During switching, the DCS controls the high-voltage main switch on the 6kV side to open, and then opens the first contactor of the input contactor on the inverter side and the second contactor of the output contactor on the inverter side. The time period is set, the third contactor of the power frequency input contactor is closed first, and then the main switch on the 6kV side is closed to complete the electrical switching.

[0094] Specific analysis of the time delay of closing the 6KV side switch: after the inverter trips due to a fault, the DCS control receives the 6KV side switch position feedback signal with an inherent delay of 200ms, the time to judge and export the tripped contactor is 1s, the time to receive the closed position feedback signal of the power frequency side contactor is 200ms, the setting calculation shows that the demagnetization time of the motor is 2-3s, and a 1s delay is added to close the 6KV side switch. The switching time of the automatic frequency conversion to power frequency logic should be controlled within 5s.

[0095] During the switching process, the 6KV side switch must be protected. If the 6KV side switch is not tripped due to inverter failure, automatic switching will cause a secondary impact on the 6KV side switch power system. A NOT gate for the 6KV side switch protection action is added to the switching start logic, that is, the frequency conversion switching to industrial frequency logic is not started when the 6KV side switch protection is actuated.

[0096] When the unit is shut down, the inverter maintenance test process causes the frequency conversion to power frequency logic control, and the MFT boiler fire extinguishing protection reset signal is added to the switching start logic. When the reset signal is detected, it is ensured that the frequency conversion to power frequency control logic is not started in the shutdown state.

[0097] When the inverter is started, if a fault trip occurs before the inverter is started, the inverter position cannot be determined and the inverter cannot be put into operation. In this case, a manual start-up button for switching the inverter to the industrial frequency is added to the switching start logic to ensure that the inverter is started normally before manual start-up.

[0098] If a situation occurs that causes the frequency conversion and power frequency switching logic to be executed cyclically, and the 6KV side switch is opened and closed multiple times, the frequency conversion and power frequency switching execution will be automatically exited after the frequency conversion and power frequency switching start logic starts, ensuring that the automatic switching logic is only executed once.

[0099] When the specific parts are logically controlled: when the frequency conversion input switches K1 and K2 are in the closed position, the 6kv switch is closed, and the primary fan motor is variable frequency operation. When K1 and K2 are in the open position, after the K3 contactor is closed, the 6kv switch is closed, and the primary fan motor is operated at the industrial frequency.

[0100] The primary fan variable switching logic is as follows: when a serious fault occurs in the primary fan inverter that requires the inverter to trip, and the inverter trips and opens the 6kv switch (6kv switch position), and the unit air volume does not reach the MFT setting (MFT reset signal) to start the boiler fire extinguishing, and the variable switching function button is enabled (automatic switching is enabled), and the primary fan motor operates normally and the 6kv protection device does not operate (the primary fan has no protection action signal), when all the above conditions are met, the DCS issues a command to trip the primary fan inverter input switches KM1 and KM2. To ensure the orderly tripping of the switches and prevent reverse power supply caused by the simultaneous opening and closing of the switches, after the KM1 and KM2 tripping commands are issued, there is a delay of 2 seconds, and the DCS issues a KM3 closing command to close the primary fan power frequency output switch KM3. When all the above logics are executed and the KM3 switch is closed (the primary fan inverter power frequency output switch KM3 is closed), the DCS sends a command to close the primary fan 6KV switch, closes the 6kV switch, and the primary fan motor switches to power frequency operation.

[0101] The DCS configuration logic of automatic power cut-off of primary fan fault is: when a fan inverter has a serious fault that requires the inverter to trip (primary fan inverter serious fault), and the inverter trips, that is, the 6kv switch is open (primary fan inverter stops), and the unit air volume does not reach the MFT setting value for starting boiler fire extinguishing (MFT does not act), and the variable power cut function button is put into operation (variable power cut is put into operation), and the air volume in the wind and smoke system meets the operating requirements, the primary fan thermal protection is not acted (primary wind protection is not acted), and the primary fan The motor is normal, and the 6kv protection device does not work (the primary fan trips in reverse). When all the above conditions are met, the DCS issues a command to trip the primary fan inverter input switch KM1 and KM2 (divided into primary fan inverter input switches KM1 and KM2). To ensure the orderly tripping of the switches and prevent reverse power supply caused by the simultaneous opening and closing of the switches, after the KM1 and KM2 tripping commands are issued, there is a delay of 2 seconds, and the DCS issues a KM3 closing command to close the primary fan power frequency output switch KM3, and simultaneously starts the primary fan variable switching condition. When all the above logics are executed and the KM3 switch is closed (the primary fan inverter power frequency output switch KM3 is closed, and the KM3 switch position is two out of three), the DCS issues a command to close the primary fan 6KV switch, closes the 6kV switch, and the primary fan motor switches to power frequency operation.

[0102] After the KM3 closing time is over (KM3 position signals 1, 2, 3, three out of two with a 3-second delay), and the 6KV switch opening position (three out of two with a complete stop of the primary fan), that is, the 6kv switch closing failure, or the 6kv switch closing failure (three out of two with a complete stop of the primary fan) after a 5-second delay, the unit RB condition is started.

[0103] To ensure the safe operation of the unit, the primary fan inverter logic can only be executed once. Therefore, according to field tests, it takes up to 10 seconds for the above logic to be executed. Once the variable cut logic is started, after a delay of 10s+5s, the variable cut execution logic block is automatically cut off (variable cut automatic cut).

[0104] The process of starting RB when the transformer fails to cut is as follows: when the power frequency output switch KM3 of the primary fan inverter is closed, after a 2s delay (to ensure the reliable closing time of KM3), and the 6kv switch is open (i.e. 6kv closing fails), the unit RB logic is started. Or if the 6kV switch trips or fails to close due to other reasons (the primary fan 6kV switch is open), the delay is 5s, and the unit RB is started.

[0105] When the variable frequency drive logic is executed successfully, the primary fan 6kV switch is closed again, and the primary fan motor runs at full speed, for stable combustion in the furnace, the DCS cuts off the inverter control logic and switches to the primary wind damper automatic / manual control logic.

[0106] Taking the variable cutting of the primary fan A as an example, after an 8s delay, the SFT damper designated position adjustment logic block is started. Z in the SFT logic block is set to 1, and the X1 damper position 80% instruction is forced to be output. To the X2 pin of the next SFT logic block. The 103 / 61 point is the variable cutting failure triggering the RB logic block, which is 0 at this time, so the SFT logic block continues to output the 80% opening instruction to the ES / MA logic block OV override forced opening pin, so after the variable cutting is completed, the primary fan damper position is forced to output 80% opening. In the ES / MA logic block, the priority of the OV pin is higher than the automatic control priority of the X pin.

[0107] Therefore, after the variable cutting is completed, the damper position of the primary fan is forced to open to 80%. When the furnace is stably burning, the operator can switch the damper automatically to manual control mode. At this time, the OV instruction priority in the ES / MA logic block is cut off, and the damper automatic control priority (5-0) of the X pin is input by ES / MA. According to the current primary air pressure and the primary air pressure setting value set by the operator, the RATL logic block is entered for differential adjustment, and the calculation result enters the DEW correction logic block. After the difference (power frequency) correction is performed with the primary air pressure deviation under the power frequency state, it enters the Z1 pin in the QORS operation logic block. According to the PID algorithm, the QOR8 logic block converts the primary air pressure difference into the damper opening amount. The damper opening adjustment amount is input into the TOM pin in the ES / MA logic block, and finally the primary air damper instruction is output by ES / MA. Thereby achieving the purpose of stable combustion in the furnace and manual adjustment of air volume.

[0108] For the start and stop control logic of the 6kV side switch, DCS uses the DEVICE module for control. When the transformer shear logic is activated, the 6kV switch override command is issued (transformer shear override 6kV switch), and the primary fan has no protection tripping or fault signal, the device module executes Emd1 to output a forced closing command, i.e. out1, and outputs a 6kV switch closing command. When the primary fan smoke temperature, damper opening, and auxiliary machine operating conditions meet the primary fan start permission conditions, the D1p pin is set to 1, and the closing permission signal is issued in the operation interface, allowing the primary fan 6kv switch to start. When the primary fan inverter stops the input signal, after a 10-second free stop delay, the D2P in the device module, i.e. the closing permission command is issued, and the opening permission is issued in the operation interface, allowing the primary fan 6kv switch to stop.

[0109] The running signal of the primary fan is fed back to FB1 (start feedback signal) and set to 1, and the device feeds back the running status of the primary fan. The stop signal of the primary fan is fed back to FB2 (stop feedback signal) and set to 1, and the device feeds back the stop status of the primary fan. The remote local status of the primary fan is inverted and input into the device module LOC management. When the input result is 1, the primary fan control mode is judged to be remote, allowing the DCS to send start and stop commands to the 6kV switch of the primary fan. The LPWR pin in the device module reflects the minor or major fault status of the primary fan inverter. Once the inverter is in a fault state, the device module blocks the output of the primary fan start / start command. Similarly, the protection action signal of the primary fan is connected to the fault pin of the device module. That is, the 6kv protection device is activated and the start command of the device module is locked. The trip protection of one side of the fan, that is, the thermal protection is introduced into the totp pin of the device module, the thermal protection is activated, and the DEVICE module is locked, that is, the start command of the primary fan is locked.

[0110] Those skilled in the art will appreciate that the embodiments of the present disclosure may be provided as methods, systems, or computer program products. Therefore, the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present disclosure may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0111] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0112] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0113] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0114] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

[0115] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A method for automatically switching the frequency of a primary fan inverter when it fails, characterized in that the steps include: Collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and send out the inverter serious fault alarm signal; Receive the fault signal of the primary fan inverter, start the DCS control logic, and control the inverter outlet to trip the 6KV side main switch; Receive the switch position feedback signal on the 6KV side and automatically switch to the power frequency by frequency conversion; During the switching process, the furnace operation status is tracked in real time to obtain the normal pressure and temperature signals inside the furnace. Otherwise, the RB logic state is immediately entered to rescue the unit. During the switching process, the 6KV side switch must be protected. If the 6KV side switch is not tripped due to inverter failure, automatic switching will cause a secondary impact on the 6KV side switch power system. A NOT gate for the 6KV side switch protection action is added to the switching start logic, that is, the frequency conversion switching to industrial frequency logic is not started when the 6KV side switch protection is actuated.

2. A method for automatic frequency conversion switching of a primary fan inverter fault as claimed in claim 1, characterized in that: During switching, the DCS controls the high-voltage main switch on the 6kV side to open, and then opens the first contactor of the input contactor on the inverter side and the second contactor of the output contactor on the inverter side. The time period is set, the third contactor of the power frequency input contactor is closed first, and then the main switch on the 6kV side is closed to complete the electrical switching.

3. A method for automatic frequency conversion switching of a primary fan inverter fault as described in claim 2, characterized in that: Specific time analysis of delayed closing of the 6KV side switch: After the inverter trips due to a fault, the DCS control receives the 6KV side switch position feedback signal with an inherent delay of 200ms. The time to determine and output the tripped contactor is 1s. The time to receive the closed position feedback signal of the power frequency side contactor is 200ms. The demagnetization time of the motor is calculated to be 2-3s, plus a 1s delay to close the 6KV side switch.

4. A method for automatic frequency conversion switching of a primary fan inverter fault as claimed in claim 1, characterized in that: The switching time of automatic frequency conversion to industrial frequency logic should be controlled within 5s.

5. A method for automatic frequency conversion switching of a primary fan inverter fault as claimed in claim 1, characterized in that: When the unit is shut down, the inverter maintenance test process causes the frequency conversion to power frequency logic control, and the MFT boiler fire extinguishing protection reset signal is added to the switching start logic. When the reset signal is detected, it is ensured that the frequency conversion to power frequency control logic is not started in the shutdown state.

6. A method for automatic frequency conversion switching of a primary fan inverter fault as claimed in claim 1, characterized in that: When the inverter is started, if a fault trip occurs before the inverter is started, the inverter position cannot be determined and the inverter cannot be put into operation. In this case, a manual start-up button for switching the inverter to the industrial frequency is added to the switching start logic to ensure that the inverter is started normally before manual start-up.

7. A method for automatic frequency conversion switching of a primary fan inverter fault as claimed in claim 1, characterized in that: If a situation occurs that causes the frequency conversion and power frequency switching logic to be executed cyclically, and the 6KV side switch is opened and closed multiple times, the frequency conversion and power frequency switching execution will be automatically exited after the frequency conversion and power frequency switching start logic starts, ensuring that the automatic switching logic is only executed once.

8. A primary fan inverter fault frequency conversion automatic switching device based on a primary fan inverter fault frequency conversion automatic switching method as described in any one of claims 1 to 7, characterized in that: include: Frequency converter, a power control device used to control AC motors, mainly consists of rectification, filtering, inversion, braking unit, drive unit, detection unit and microprocessing unit; The sensor is used to collect the operating status of the primary fan inverter in real time, obtain the fault signal of the primary fan inverter and issue a serious fault alarm signal of the inverter; The DCG control system is used to receive the fault signal of the primary fan inverter, start the DCS control logic, control the inverter outlet to trip the 6KV side main switch, and receive the 6KV side switch position feedback signal to perform frequency conversion and automatic switching of the power frequency; Contactor, used for switch closing in frequency conversion and power frequency switching logic control.

9. A primary fan inverter fault automatic frequency switching device as claimed in claim 8, characterized in that: It also includes a circuit breaker and a motor. The circuit breaker realizes arc extinguishing during the frequency conversion to power frequency switching process, and the motor realizes the operation of the entire power system.

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