A frequency converter anti-electrical shaking control system and an electric shaking detection method thereof

Abstract

The present invention discloses an inverter anti-electrical sway control system and an electric sway detection method thereof, belonging to the technical field of inverter anti-electrical sway control systems and electric sway detection methods thereof; the technical problem to be solved is: to provide an improvement in the structure of an inverter anti-electrical sway control system; the technical scheme adopted to solve the above technical problem is: comprising an inverter and an anti-electrical sway control device, the anti-electrical sway control device comprising an anti-electrical sway control unit, a charging module, a backup power supply unit, and a voltage stabilizing and filtering module, the output end of the anti-electrical sway control unit is connected in parallel to the inverter DC bus, for realizing the detection of the voltage on the inverter DC bus and switching the power supply mode of the inverter; the input end of the anti-electrical sway control unit is connected to the power output end of the backup power supply unit through a wire, and the power input end of the backup power supply unit is connected to the charging module and the voltage stabilizing and filtering module through a wire; the present invention is applied to inverter power grid electric sway.

Description

Technical Field

[0001] The invention discloses a frequency converter anti-electrical shaking control system and an electric shaking detection method thereof, belonging to the technical field of frequency converter anti-electrical shaking control systems and electric shaking detection methods thereof. Background Art

[0002] The inverter is an electric energy control device that uses the on-off function of power semiconductor devices to convert the industrial frequency power supply into another frequency. In industrial control, low-voltage inverters are often used to control the motor speed to meet the needs of energy saving and control.

[0003] Coal chemical enterprises have many important equipment that require frequency conversion speed regulation. Due to the strong continuity of their production process, the frequency conversion equipment will stop for a short time when the power grid "shakes", and the entire process will be interrupted, causing huge economic losses to the enterprise. At the same time, during the operation of the low-voltage inverter, the power grid may shake or lose power. The short-term undervoltage caused by the power grid shaking will cause the inverter to trip and stop, affecting production.

[0004] When there is power grid shaking, the inverter tripping caused by power shaking is usually solved by canceling the low-voltage protection setting of the inverter and setting it to the undervoltage recovery and restart mode. However, undervoltage recovery and restarting are prone to cause the inverter overcurrent protection to operate, and the restart function has low reliability and is prone to refusal to operate. Therefore, it is necessary to provide a control system with high reliability that can effectively solve the problem of inverter anti-power shaking and a power shaking detection method. Summary of the invention

[0005] In order to overcome the deficiencies in the prior art, the present invention aims to solve the technical problem of providing an improvement in the hardware structure of a frequency converter power swing control system.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: an inverter anti-electrical sway control system, including an inverter, and also including an anti-electrical sway control device, the anti-electrical sway control device includes an anti-electrical sway control unit, a charging module, a backup power supply unit, and a voltage stabilizing filter module, the output end of the anti-electrical sway control unit is connected to the inverter DC bus, for realizing the voltage detection on the inverter DC bus and switching the power supply mode of the inverter;

[0007] The input end of the anti-power sway control unit is connected to the power output end of the backup power supply unit through a wire, and the power input end of the backup power supply unit is connected to the charging module and the voltage stabilizing and filtering module through a wire. The charging module is used to charge the backup power supply unit when there is no power sway, and the voltage stabilizing and filtering module is used to realize harmonic filtering and voltage stabilization processing of the connected alternating current, and input the processed direct current into the anti-power sway control unit.

[0008] The anti-power sway control device also includes a battery inspection instrument and a monitoring alarm module. The battery inspection instrument is arranged on the backup power supply unit and is used to detect the battery operating parameters inside the backup power supply unit;

[0009] The monitoring alarm module is connected to the anti-power sway control unit, the charging module, and the battery inspection instrument through wires, and is used to monitor the operation of each unit module in the anti-power sway control device and to alarm for abnormal situations.

[0010] The anti-power sway control unit includes a current pressure difference control unit and a diode module. The current pressure difference control unit includes a thyristor V1, a pressure difference controller, and a voltage relay YJ1. The anode A of the thyristor V1 is connected to the positive electrode of the backup power supply unit through a wire, the cathode K of the thyristor V1 is connected to the negative electrode of the transformer DC bus through a wire, and the gate level G of the thyristor V1 is connected to the output control end of the pressure difference controller through a wire. The pressure difference controller controls the conduction and cutoff of the gate level G of the thyristor V1 by judging the voltage on the DC bus of the inverter;

[0011] The diode module is used to protect the control unit against power fluctuations.

[0012] The coil of the voltage relay YJ1 is connected in parallel to the power input terminal of the frequency converter 1, and the contacts of the voltage relay YJ1 are connected to the IN+ and IN- terminals of the flow pressure difference control unit through wires.

[0013] The two ends of the thyristor V1 are connected in parallel with the contact KM7.1 of the bypass contactor KM7, one end of the coil KM7.2 of the bypass contactor KM7 is connected to the NC terminal of the current pressure difference control unit, and the other end of the coil KM7.2 of the bypass contactor is connected to the power supply. The bypass contactor KM7 is used to enable the inverter to disconnect the power supply of the backup power supply unit and switch to the mains power supply when the grid voltage returns to normal.

[0014] A display screen is provided on the front of the housing of the anti-power sway control device, and the display screen is connected to the anti-power sway control unit via a wire, and is used to display the time of power failure and power restoration of the inverter and the support time of the backup power supply unit.

[0015] The backup power supply unit is specifically a battery pack, and the battery pack includes a plurality of batteries connected in series.

[0016] The model of the charging module is TH600X10ZZ, and the model of the voltage stabilizing and filtering module is TH600X05ZZ.

[0017] A method for detecting power swing of a frequency converter comprises the following steps:

[0018] Step 1: Turn on the power of the inverter and the anti-power sway control device to make the inverter operate normally, and the charging module charges the backup power supply unit;

[0019] Step 2: When the anti-power-shaking control unit detects that the voltage of the inverter DC bus is lower than the set range, it is determined that power shaking occurs and the process goes to step 3; when the anti-power-shaking control unit detects that the voltage of the inverter DC bus is within the normal range, it is determined that the AC power is normal and the process goes to step 1;

[0020] Step 3: The anti-power sway control unit controls the gate G of the thyristor V1 to be turned on. At this time, the inverter is in a DC support state, that is, the inverter is powered by the backup power supply unit;

[0021] Step 4: When the anti-power sway control unit detects that the voltage of the inverter DC bus is higher than the set range, it is judged that the AC power is restored, and the process goes to step 5; when the anti-power sway control unit detects that the voltage of the inverter DC bus is lower than the set value, it is judged that the AC power is not restored, and the process goes to step 6;

[0022] Step 5: The anti-power swing control device exits operation, completing a power swing protection;

[0023] Step 6: Control the inverter to stop within the set time.

[0024] The setting range of the voltage of the inverter DC bus in step 2 is ≤500V;

[0025] The setting range of the voltage of the inverter DC bus in step 4 is >500V;

[0026] The setting time of the frequency converter in step 6 is 5 minutes to 15 minutes.

[0027] The beneficial effects of the present invention compared with the prior art are as follows: the inverter anti-electrical sway control system provided by the present invention detects the voltage on the DC bus of the inverter by connecting an anti-electrical sway control unit in parallel on the DC bus of the inverter, and judges the electric sway situation by judging the detected voltage. When electric sway occurs, the thyristor is controlled to be turned on, so that the power supply mode of the inverter is switched from the mains to the backup power supply unit, thereby reducing the phenomenon of short-term shutdown of the inverter when electric sway occurs, avoiding an electric sway accident, saving the time for re-starting the entire process, greatly reducing economic losses, and improving the work efficiency of coal chemical enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] Figure 1 It is a structural schematic diagram of the present invention;

[0030] Figure 2It is a schematic diagram of the circuit structure of the electric sway control device of the present invention;

[0031] Figure 3 It is a terminal wiring diagram of the flow pressure difference control unit of the current sway control device of the present invention;

[0032] Figure 4 It is a flow chart of the electric shaking detection method of the present invention;

[0033] Figure 5 Flow chart of the power shaking detection method in an embodiment of the present invention;

[0034] Figure 6 , Figure 7 This is a diagram showing the effect of using the embodiment of the present invention when a power shake occurs;

[0035] Figure 8 This is a display diagram of the electric shaking action information recorded on the display screen of the anti-electrical shaking control device in an embodiment of the present invention.

[0036] In the figure: 1 is the inverter, 2 is the anti-electrical shaking control device, 3 is the anti-electrical shaking control unit, 4 is the charging module, 5 is the backup power supply unit, 6 is the voltage stabilizing and filtering module, 11 is the inverter DC bus, 31 is the current pressure difference control unit, and 32 is the diode module. DETAILED DESCRIPTION

[0037] like Figures 1 to 8 As shown, the present invention provides an inverter anti-electrical sway control system, comprising an inverter 1, and an anti-electrical sway control device 2, wherein the anti-electrical sway control device 2 comprises an anti-electrical sway control unit 3, a charging module 4, a backup power supply unit 5, and a voltage stabilizing filter module 6, wherein the output end of the anti-electrical sway control unit 3 is connected in parallel to the inverter DC bus 11, so as to detect the voltage on the inverter DC bus 11 and switch the power supply mode of the inverter 1;

[0038] The input end of the anti-power sway control unit 3 is connected to the power output end of the backup power supply unit 5 through a wire, and the power input end of the backup power supply unit 5 is connected to the charging module 4 and the voltage stabilizing and filtering module 6 through a wire. The charging module 4 is used to charge the backup power supply unit 5 when there is no power sway, and the voltage stabilizing and filtering module 6 is used to realize harmonic filtering and voltage stabilization processing of the connected alternating current, and input the processed direct current into the anti-power sway control unit 3.

[0039] The anti-power sway control device 2 also includes a battery inspection instrument and a monitoring alarm module. The battery inspection instrument is arranged on the backup power supply unit 5 and is used to detect the battery operating parameters inside the backup power supply unit 5;

[0040] The monitoring alarm module is connected to the anti-power sway control unit 3, the charging module 4, and the battery inspection instrument through wires, and is used to monitor the operation of each unit module in the anti-power sway control device 2 and alarm for abnormal situations.

[0041] The anti-power sway control unit 3 includes a current pressure difference control unit 31 and a diode module 32. The current pressure difference control unit 31 includes a thyristor V1, a pressure difference controller, and a voltage relay YJ1. The anode A of the thyristor V1 is connected to the positive electrode of the backup power supply unit 5 through a wire, the cathode K of the thyristor V1 is connected to the negative electrode of the transformer DC bus 11 through a wire, and the gate level G of the thyristor V1 is connected to the output control end of the pressure difference controller through a wire. The pressure difference controller controls the conduction and cutoff of the gate level G of the thyristor V1 by judging the voltage on the DC bus of the inverter 1;

[0042] The diode module 32 is used to protect the control unit 3 against power fluctuations.

[0043] The coil of the voltage relay YJ1 is connected in parallel to the power input terminal of the frequency converter 1, and the contacts of the voltage relay YJ1 are connected to the IN+ and IN- terminals of the pressure difference control unit 31 through wires.

[0044] The two ends of the thyristor V1 are connected in parallel with the contact KM7.1 of the bypass contactor KM7, one end of the coil KM7.2 of the bypass contactor KM7 is connected to the NC terminal of the pressure difference control unit 31, and the other end of the coil KM7.2 of the bypass contactor is connected to the power supply. The bypass contactor KM7 is used to enable the inverter 1 to disconnect the power supply of the backup power supply unit 5 and switch to the mains power supply when the grid voltage returns to normal.

[0045] A display screen is provided on the front of the housing of the anti-power-sway control device 2 , and the display screen is connected to the anti-power-sway control unit 3 via a wire, and is used to display the power outage and power restoration time of the inverter 1 and the support time of the backup power supply unit 5 .

[0046] The backup power supply unit 5 is specifically a battery pack, and the battery pack includes a plurality of batteries connected in series.

[0047] The model of the charging module 4 is TH600X10ZZ, and the model of the voltage stabilizing and filtering module 6 is TH600X05ZZ.

[0048] A method for detecting power swing of a frequency converter comprises the following steps:

[0049] Step 1: Turn on the power of the inverter 1 and the anti-power sway control device 2 to make the inverter 1 operate normally, and the charging module 4 charges the backup power supply unit 5;

[0050] Step 2: When the anti-power sway control unit 3 detects that the voltage of the inverter DC bus 11 is lower than the set range, it is determined that power sway occurs, and the process goes to step 3; when the anti-power sway control unit 3 detects that the voltage of the inverter DC bus 11 is within the normal range, it is determined that the mains power is normal, and the process goes to step 1;

[0051] Step 3: The anti-power-shaking control unit 3 controls the gate G of the thyristor V1 to be turned on. At this time, the inverter 1 is in a DC support state, that is, the inverter 1 is powered by the backup power supply unit 5;

[0052] Step 4: When the anti-power sway control unit 3 detects that the voltage of the inverter DC bus 11 is higher than the set range, it is judged that the mains power is restored, and the process goes to step 5; when the anti-power sway control unit 3 detects that the voltage of the inverter DC bus 11 is lower than the set value, it is judged that the mains power is not restored, and the process goes to step 6;

[0053] Step 5: The anti-power swing control device 2 exits operation, completing a power swing protection;

[0054] Step 6: Control inverter 1 to stop within the set time.

[0055] The setting range of the voltage of the inverter DC bus 11 in step 2 is ≤500V;

[0056] The setting range of the voltage of the inverter DC bus 11 in step 4 is >500V;

[0057] In step 6, the setting time of the frequency converter 1 is 5 minutes to 15 minutes.

[0058] The inverter anti-electrical shaking control system provided by the present invention can be applied to the inverter of the liquid oxygen pump. The anti-electrical shaking control system and the electric shaking judgment method of the present invention are further described according to the following embodiments.

[0059] In this embodiment, according to the 4 sets of liquid oxygen pumps of the air separation unit, the rated voltage of the motor is 380V, the rated power is 85KW, the rated current is 170A, and the frequency is 82Hz; the total power of the liquid oxygen pump of the air separation unit is 340KW. According to the on-site conditions, an anti-power swing control device 2 with a power of 400KW can meet the requirements, the backup time of the inverter 1 during power swing is set to 5min, and the judgment voltage of the inverter DC bus 11 is set to 500V. If it is lower than 500V, it is judged that power swing occurs, and if it is higher than 500V, it is judged that the mains power is normal.

[0060] The anti-power sway control device 2 mainly consists of a charging module 4, a backup power supply unit 5, i.e., a battery pack, an intelligent control system, an anti-power sway control unit 3 (including thyristors, differential pressure controllers, diode modules, etc.), a battery inspection instrument, and a monitoring and alarm module. Figure 3As shown, during normal operation, QF11 is closed, and the inverter 1 is powered by the low-voltage AC busbar of the factory power supply. The inverter 1 controls the motor speed according to the 4-20mA signal given by the instrument DCS. At this time, the circuit breakers QF1, QF2, QF3, QF4, QF5, QF6, and the battery fuses in the anti-sway control device 2 are all closed, and the battery pack is float-charged through the charging module 4. The anti-sway control unit 3 determines that the inverter 1 is operating normally, and the terminals IN+ and IN- on the current pressure difference control unit 31 sample the AC voltage of the inverter 1 to determine that the voltage is normal and there is no fault signal. The thyristor V1 in the current pressure difference control unit 31 is in the cut-off state, there is no DC output, and the anti-sway control device 2 is in the hot standby state.

[0061] When the chemical plant power grid "shakes", the terminals IN+ and IN- of the flow pressure difference control unit 31 detect that the grid voltage is reduced (the mains voltage is lower than 353V), and the terminals DC+ and DC- of the flow pressure difference control unit 31 detect that the DC bus voltage is ≤500V. At this time, the flow pressure difference control unit 31 controls the thyristor V1 to turn on through terminals A, G, and K, and the conduction time is ≤100μs. The inverter 1 is converted from factory power to DC support system battery pack power supply, and the liquid oxygen pump runs continuously without interruption.

[0062] When the power supply to the chemical plant is restored, the terminals IN+ and IN- of the flow pressure difference control unit 31 detect that the grid voltage has returned to normal. The flow pressure difference control unit 31 controls the contact KM7.1 of the bypass contactor KM7 connected in parallel with the thyristor V1 through the terminals NO and NC to attract. At this time, the flow pressure difference control unit 31 controls the thyristor V1 to close, and then disconnects the terminals NO and NC of the flow pressure difference control unit 31, disconnects the battery power supply, and the inverter 1 switches to the factory power supply. During this process, the liquid oxygen pump remains in continuous operation. The anti-power sway control device 2 switches to the hot standby state. After each action, the anti-power sway control device 2 displays and records the time of power outage, power restoration and support time through the display screen, which is convenient for querying the action record.

[0063] Figure 6 This is a data record of the electric shaking action of the liquid oxygen pump inverter of this embodiment when the 10KV I section ABC three-phase short circuit occurs, the three-phase voltage drops to 800V, and the fault time is 82ms. Figure 7 This is the data record of the electric shaking action of the liquid oxygen pump inverter in this embodiment when the B phase is short-circuited to the ground first and then the ABC three-phase short-circuited in the 110KV II section, and the fault time is 61ms. Figure 6 and Figure 7 The displayed action process data shows that after adding the anti-sway control device 2, the last two "sways" ( Figure 6 , Figure 7 ) Since the anti-power-shake control device 2 operates correctly ( Figure 8), which ensured the continuous and stable operation of the liquid oxygen pump without affecting production, and the effect was good.

[0064] The present invention has great application in coal chemical enterprises. There are many important equipments in coal chemical enterprises that need frequency conversion speed regulation. Due to the strong continuity of its production process, the frequency conversion equipment will be temporarily stopped when the power grid "shakes", and the whole process will be interrupted, which will bring huge economic losses to the enterprise. The setting of the anti-shaking control device 2 just solves this problem. Coal chemical industry is a continuous process. Avoiding a shaking accident can save at least 5 hours of restarting time. The oil output of the plant is 16 tons per hour, calculated at 2,000 yuan per ton, and the urea output is 50 tons per hour, calculated at 1,600 yuan per ton, which can avoid direct economic losses of 560,000 yuan.

[0065] What needs to be explained about the specific structure of the present invention is that the connection relationship between the various component modules adopted in the present invention is definite and feasible. Except for the special instructions in the embodiments, the specific connection relationship can bring about the corresponding technical effects, and solve the technical problems raised by the present invention without relying on the execution of the corresponding software program. Except for the specific instructions, the models and connection methods of the components, modules and specific components appearing in the present invention belong to the existing technologies such as published patents, published journal articles, or common knowledge that can be obtained by technical personnel in this field before the application date, and there is no need to elaborate, so that the technical solution provided in this case is clear, complete and feasible, and the corresponding physical products can be reproduced or obtained according to the technical means.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency converter anti-power sway control system, comprising a frequency converter (1), characterized in that: It also comprises an anti-electrical sway control device (2), the anti-electrical sway control device (2) comprising an anti-electrical sway control unit (3), a charging module (4), a backup power supply unit (5), and a voltage stabilization filter module (6), the output end of the anti-electrical sway control unit (3) being connected in parallel to the inverter DC bus (11) for detecting the voltage on the inverter DC bus (11) and switching the power supply mode of the inverter (1); The input end of the anti-power sway control unit (3) is connected to the power output end of the backup power supply unit (5) through a wire, and the power input end of the backup power supply unit (5) is connected to the charging module (4) and the voltage stabilizing filter module (6) through a wire. The charging module (4) is used to charge the backup power supply unit (5) when there is no power sway, and the voltage stabilizing filter module (6) is used to perform harmonic filtering and voltage stabilization on the connected alternating current, and input the processed direct current into the anti-power sway control unit (3); The anti-sway control unit (3) comprises a current pressure difference control unit (31) and a diode module (32); the current pressure difference control unit (31) comprises a thyristor V1, a pressure difference controller, and a voltage relay YJ1; the anode A of the thyristor V1 is connected to the positive electrode of the backup power supply unit (5) via a wire; the cathode K of the thyristor V1 is connected to the negative electrode of the inverter DC bus (11) via a wire; the gate G of the thyristor V1 is connected to the output control end of the pressure difference controller via a wire; the pressure difference controller controls the conduction and cutoff of the gate G of the thyristor V1 by judging the voltage on the inverter DC bus (11); The diode module (32) is used to protect the control unit (3) against power fluctuations; The two ends of the thyristor V1 are connected in parallel to the contact KM7.1 of the bypass contactor KM7, one end of the coil KM7.2 of the bypass contactor KM7 is connected to the NC terminal of the current pressure difference control unit (31), and the other end of the coil KM7.2 of the bypass contactor is connected to the power supply. The bypass contactor KM7 is used to disconnect the power supply of the backup power supply unit (5) from the frequency converter (1) and switch to the mains power supply when the grid voltage returns to normal.

2. The inverter anti-power sway control system according to claim 1, characterized in that: The anti-power sway control device (2) further comprises a battery inspection instrument and a monitoring alarm module, wherein the battery inspection instrument is arranged on the backup power supply unit (5) and is used to detect the battery operating parameters inside the backup power supply unit (5); The monitoring alarm module is connected to the anti-power sway control unit (3), the charging module (4) and the battery inspection meter through wires, and is used to monitor the operation of each unit module in the anti-power sway control device (2) and to issue an alarm for abnormal situations.

3. The inverter anti-power sway control system according to claim 2, characterized in that: The coil of the voltage relay YJ1 is connected in parallel to the power input terminal of the frequency converter (1), and the contacts of the voltage relay YJ1 are connected to the IN+ and IN- terminals of the flow pressure difference control unit (31) through wires.

4. The inverter anti-power sway control system according to claim 3, characterized in that: A display screen is provided on the front of the housing of the anti-power sway control device (2). The display screen is connected to the anti-power sway control unit (3) via a wire and is used to display the time of power failure and power restoration of the frequency converter (1) and the support time of the backup power supply unit (5).

5. The inverter anti-power sway control system according to claim 4, characterized in that: The backup power supply unit (5) is specifically a battery pack, which comprises a plurality of batteries connected in series.

6. The inverter anti-power sway control system according to claim 5, characterized in that: The model of the charging module (4) is TH600X10ZZ, and the model of the voltage stabilizing and filtering module (6) is TH600X05ZZ.

7. A method for detecting power swing of a frequency converter, using the frequency converter anti-power swing control system according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Turn on the power of the frequency converter (1) and the anti-power sway control device (2), so that the frequency converter (1) operates normally, and the charging module (4) charges the backup power supply unit (5); Step 2: When the anti-power sway control unit (3) detects that the voltage of the inverter DC bus (11) is lower than the set range, it is determined that power sway occurs, and the process goes to step 3; when the anti-power sway control unit (3) detects that the voltage of the inverter DC bus (11) is within the normal range, it is determined that the mains power is normal, and the process goes to step 1; Step 3: The anti-power-sway control unit (3) controls the gate G of the thyristor V1 to be turned on, and at this time the inverter (1) is in a DC support state, that is, the inverter (1) is powered by the backup power supply unit (5); Step 4: When the anti-power sway control unit (3) detects that the voltage of the inverter DC bus (11) is higher than the set range, it is determined that the AC power is restored, and the process goes to step 5; when the anti-power sway control unit (3) detects that the voltage of the inverter DC bus (11) is lower than the set value, it is determined that the AC power is not restored, and the process goes to step 6; Step 5: The anti-power swing control device (2) exits operation, completing a power swing protection; Step 6: Control the inverter (1) to stop within the set time.

8. A method for detecting power swing in a frequency converter according to claim 7, characterized in that: In the step 2, the voltage setting range of the inverter DC bus (11) is ≤500V; In step 4, the voltage setting range of the inverter DC bus (11) is >500V; The setting time of the frequency converter (1) in step 6 is 5 minutes to 15 minutes.

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