Unplanned power failure control circuit and control method based on variable frequency driving device

Abstract

The invention discloses an unplanned power failure control circuit and control method based on a variable frequency driving device, two connecting ends of a voltage transformer are respectively connected with two phase lines in a three-phase bus, and two signal output ends of the voltage transformer are respectively connected with two pins of a controller; one normally-open auxiliary contact of the first circuit breaker is connected with one on-off control pin of the controller, and a coil of the third contactor and a coil of the fourth contactor are connected in parallel and are connected in series between the other normally-open auxiliary contact of the first circuit breaker and the other on-off control pin of the controller. The control method comprises the following steps: judging whether a voltage signal acquired by the voltage transformer is greater than a first preset voltage value or not, and if so, controlling the normally open dry node of the relay to be disconnected. According to the control method, the capacitor and the surge protector can be cut off from the current circuit when the bus is over-voltage, so that circuit devices are prevented from being burnt due to over-voltage during unplanned power failure after open-loop control debugging.

Description

Technical Field

[0001] The present invention relates to the technical field of control circuits, and in particular to an unplanned power failure control circuit and a control method based on a variable frequency drive device. Background Art

[0002] Before the variable frequency drive equipment leaves the factory, it needs to be debugged for factory parameters. When debugging the variable frequency drive equipment, the mains power of the drive equipment is often drawn from the 3P miniature circuit breaker outlet of the distribution box and is not effectively grounded. The distribution box belongs to the terminal extremely weak power supply system. At the same time, the no-load current required by the variable frequency drive equipment often exceeds the rated current of the extremely weak power grid, that is, the no-load current of the variable frequency drive equipment during open-loop debugging exceeds the rated current of the miniature circuit breaker in the distribution box, causing the terminal extremely weak power supply system to overload and trip, resulting in unplanned power outages.

[0003] The variable frequency drive device contains an LCL filter, which is itself a second-order system, so it will cause resonance, causing the voltage gain at the corresponding resonant frequency to be amplified, thereby causing overvoltage and affecting the stability of the system.

[0004] During the debugging process, the extremely weak power grid overload at the end caused an unplanned power outage of the variable frequency drive equipment, accompanied by overvoltage in the bus system. At the same time, the bus overvoltage flows into the grounding protection system through the surge protector (SPD), so that the overvoltage enters the secondary system from the control transformer, causing the capacitors of multi-function instruments, indicator lights, switching power supplies and other devices in the secondary system to burn out, affecting the stability of the system. Therefore, the control circuit for debugging the variable frequency drive equipment in the prior art has the problem of poor stability. Summary of the invention

[0005] The embodiment of the present invention provides an unplanned power outage control circuit and control method based on a variable frequency drive device, aiming to solve the problem of poor stability of the control circuit for debugging the variable frequency drive device in the prior art.

[0006] In the first aspect, an embodiment of the present invention discloses an unplanned power outage control method based on a variable frequency drive device, which is applied to a controller, wherein the controller is communicatively connected to a voltage transformer provided in an unplanned power outage control circuit based on a variable frequency drive device, wherein a first circuit breaker is arranged in series in a three-phase bus of the control circuit, two connection ends of the voltage transformer are respectively connected to two phase lines in the three-phase bus, and two signal output ends of the voltage transformer are respectively connected to two pins of the controller; a second circuit breaker, a third contactor and a surge protector are connected in series between the three-phase bus and a grounding terminal, a normally open auxiliary contact of the first circuit breaker is connected to an on-off control pin of the controller, a coil of the third contactor and a coil of the fourth contactor are connected in parallel and connected in series between another normally open auxiliary contact of the first circuit breaker and another on-off control pin of the controller, and two of the on-off control pins are connected to a normally open dry node of a relay, and the control method includes:

[0007] Acquire a voltage signal collected by the voltage transformer and determine whether the voltage signal is greater than a first preset voltage value;

[0008] If the voltage signal is greater than a first preset voltage value, the normally open dry node is controlled to be disconnected and the normally open auxiliary contact of the first circuit breaker is disconnected to disconnect the main contacts of the third contactor and the main contacts of the fourth contactor, and the capacitor and surge protector are cut off from the current circuit to avoid overvoltage burning of circuit components during unplanned power outages after open-loop control debugging.

[0009] In a second aspect, an embodiment of the present invention further discloses an unplanned power outage control circuit based on a variable frequency drive device, wherein the electrical control circuit applies the unplanned power outage control method based on a variable frequency drive device as described in the first aspect above, and the control circuit includes the controller, the first circuit breaker, the voltage transformer, the second circuit breaker, the third contactor, the surge protector, the fourth contactor, the first contactor and the second contactor; one end of the three-phase bus is connected to the first circuit breaker, and the other end is connected to the rectifier module;

[0010] One end of the fourth contactor is connected to the three-phase busbar, and the other end is connected to the capacitor;

[0011] The first contactor is arranged in series in the three-phase bus, and the first contactor is arranged in series between the first circuit breaker and the rectifier module; the second contactor is arranged in parallel at both ends of the first contactor; and a resistor is arranged in series on each of the three connecting lines connecting the second contactor to the three-phase bus.

[0012] The embodiment of the present application discloses an unplanned power outage control circuit and control method based on a variable frequency drive device, wherein two connection ends of a voltage transformer are respectively connected to two phase lines in a three-phase bus, and two signal output ends of the voltage transformer are respectively connected to two pins of a controller; a normally open auxiliary contact of a first circuit breaker is connected to an on-off control pin of the controller, and the coil of a third contactor is connected in parallel with the coil of a fourth contactor and connected in series between another normally open auxiliary contact of the first circuit breaker and another on-off control pin of the controller, and the two on-off control pins are connected to the normally open dry node of a relay, and the control method includes: judging whether the voltage signal collected by the voltage transformer is greater than a first preset voltage value, and if so, controlling the normally open dry node of the relay to be disconnected. The above control method can cut off the capacitor and surge protector from the current circuit when the bus is over-voltage to avoid over-voltage burning of circuit components during unplanned power outages after open-loop control debugging, thereby improving the stability of the control circuit applied to the variable frequency drive device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0014] Figure 1 A method flow chart of a control method provided by an embodiment of the present invention;

[0015] Figure 2 A partial circuit structure diagram of a control circuit provided by an embodiment of the present invention;

[0016] Figure 3 Another partial circuit structure diagram of the control circuit provided by the embodiment of the present invention;

[0017] Figure 4 A circuit structure diagram of an undervoltage tripping circuit corresponding to a first circuit breaker provided in an embodiment of the present invention.

[0018] Figure symbols: QF, distribution box circuit breaker; QF1, first circuit breaker; QF2, second circuit breaker; KM1, first contactor; KM2, second contactor; KM3, third contactor; KM4, fourth contactor; FU1, fuse; TV, voltage transformer; SPD, surge protector; C, capacitor; R, resistor; L1, first inductor; L2, second inductor; S1, rectifier module; PCU, controller; T1, isolation transformer. DETAILED DESCRIPTION

[0019] 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 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.

[0020] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0021] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0022] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0023] The embodiment of the present invention discloses an unplanned power outage control method based on a variable frequency drive device, which is applied to a controller PCU. The controller PCU is connected to a voltage transformer TV provided in an unplanned power outage control circuit based on a variable frequency drive device for communication. The specific circuit connection structure is as follows: Figure 2 and Figure 3 As shown, the first circuit breaker QF1 is arranged in series in the three-phase bus of the control circuit, the two connection ends of the voltage transformer TV are respectively connected to the two phase lines in the three-phase bus, and the two signal output ends of the voltage transformer TV are respectively connected to the two pins of the controller PCU; the second circuit breaker QF2, the third contactor KM3 and the surge protector SPD are connected in series between the three-phase bus and the grounding terminal, a normally open auxiliary contact of the first circuit breaker QF1 is connected to an on-off control pin of the controller PCU, the coil of the third contactor KM3 and the coil of the fourth contactor KM4 are connected in parallel and connected in series between another normally open auxiliary contact of the first circuit breaker QF1 and another on-off control pin of the controller PCU, and the two on-off control pins are connected to the normally open dry node of the relay.

[0024] The control method disclosed in the present application is a control method for preventing overvoltage caused by unplanned power outages from burning out circuit components such as indicator lights in the system. The method is universal. Specifically: (1) The method controls the fourth contactor KM4 at the front end of the capacitor C during the disconnection of resonance to reduce the LCL resonant overvoltage; (2) The method controls the third contactor KM3 at the front end of the SPD to disconnect to prevent the inductive overvoltage in the LCL from entering the grounding protection system through the SPD. The overall control structure is simple and clear.

[0025] like Figure 1 As shown, the control method includes steps S110 to S120.

[0026] S110, obtaining a voltage signal collected by the voltage transformer and determining whether the voltage signal is greater than a first preset voltage value.

[0027] The controller PCU may acquire a voltage signal of the busbar through the voltage transformer TV, and the controller PCU determines whether the voltage signal is greater than a first preset voltage value. For example, the first preset voltage value may be set to 890V.

[0028] In a more specific embodiment, further, before the control of disconnecting the normally open dry node and disconnecting the normally open auxiliary contact of the first circuit breaker, it also includes: judging whether the voltage signal is greater than the second preset voltage value; if the voltage signal is not greater than the second preset voltage value, executing the step of controlling the normally open dry node to disconnect and disconnecting the normally open auxiliary contact of the first circuit breaker; if the voltage signal is greater than the second preset voltage value, controlling the normally open dry node of the relay to be normally closed and the normally open auxiliary contact of the first circuit breaker to be normally closed, so that the coil of the third contactor and the coil of the fourth contactor are energized, avoiding the removal of the surge protector from the current circuit when the overvoltage is caused by lightning. Among them, the second preset voltage value is 3000V, the first preset voltage value is 890V, and the detection accuracy of the voltage transformer is 0.2S.

[0029] S120. If the voltage signal is greater than a first preset voltage value, the normally open dry node is controlled to be disconnected, and the normally open auxiliary contact of the first circuit breaker is disconnected to disconnect the main contacts of the third contactor and the main contacts of the fourth contactor, and the capacitor and surge protector are cut off from the current circuit to avoid overvoltage burning of circuit components during unplanned power outages after open-loop control debugging.

[0030] In order to prevent the circuit-breaking resonant overvoltage and inductive overvoltage from entering the grounding system through the surge protector SPD, if the voltage signal is greater than the first preset voltage value, the controller PCU controls the normally open dry node of the relay to be disconnected and controls the normally open auxiliary contact of the first circuit breaker to be disconnected. When the bus overvoltage causes the normally open dry node of the relay to be disconnected and an unplanned power outage occurs (unplanned power outage includes the disconnection of the first circuit breaker QF1 or the power outage of the extremely weak front-end power grid), the main contacts of the third contactor KM3 and the fourth contactor KM4 are disconnected, thereby cutting off the capacitor C and the surge protector SPD from the three-phase bus of the variable frequency drive equipment (the capacitor C and the surge protector SPD are electrically disconnected from the three-phase bus), thereby avoiding overvoltage burning of multi-function meters, indicator lights and other circuit components during open-loop debugging.

[0031] If the voltage signal is not greater than the first preset voltage value, there is no need to control the normally open dry node of the relay to be disconnected (in this case, the normally open dry node of the relay is controlled to remain normally closed).

[0032] The embodiment of the present invention further discloses an unplanned power outage control circuit based on a variable frequency drive device, wherein the electric control circuit applies the unplanned power outage control method based on a variable frequency drive device as described in the above embodiment, such as Figure 2 and Figure 3 As shown, the control circuit includes the controller PCU, the first circuit breaker QF1, the voltage transformer TV, the second circuit breaker QF2, the third contactor KM3, the surge protector SPD, the fourth contactor KM4, the first contactor KM1 and the second contactor KM2; one end of the three-phase bus is connected to the first circuit breaker QF1, and the other end is connected to the rectifier module S1; one end of the fourth contactor KM4 is connected to the three-phase bus, and the other end is connected to the capacitor C; the first contactor KM1 is arranged in series in the three-phase bus, and the first contactor KM1 is arranged in series between the first circuit breaker QF1 and the rectifier module S1; the second contactor KM2 is arranged in parallel at both ends of the first contactor KM1; a resistor R is arranged in series on the three connecting lines connecting the second contactor KM2 to the three-phase bus. Specifically, the threshold voltage of the surge protector SPD is 900V. Three capacitors are connected in the capacitor C through a triangle, and three connecting lines are led out from the connection points between the three capacitors and are respectively connected to the three connection ends of the fourth contactor.

[0033] The primary system circuit diagram of the variable frequency drive equipment is as follows: Figure 2 As shown, when the terminal extremely weak power supply system trips due to overload, the first inductor L1 and the second inductor L2 generate a back electromotive force, and the back electromotive force E satisfies the following formula (1):

[0034]

[0035] Wherein, L1 is the inductance value of the first inductor, L2 is the inductance value of the second inductor, dI represents the change of bus current, and dt is the power-on time increment.

[0036] The breaking time of the circuit breaker in the distribution box under the extremely weak power grid at the end is very short, and the circuit can be broken within tens of microseconds. As a result, the inductive load generates a strong induced overvoltage, which can exceed 3 times the power supply voltage. At the same time, during the open-loop commissioning of the variable frequency drive equipment, the breaking of the circuit breaker in the distribution box under the extremely weak power grid at the end will cause the LCL filter to resonate, and its circuit-breaking resonant frequency is shown in formula (2):

[0037]

[0038] Wherein, L2 is the inductance value of the second inductor, and C1 is the capacitance value of the capacitor.

[0039] The bus overvoltage caused by formula (1) and formula (2) exists in the AC bus system. When the overvoltage (voltage exceeding 1200V) exceeds the surge protector SPD threshold voltage (for example, the surge protector SPD threshold voltage is 908.7V), the surge protector SPD is turned on.

[0040] In a more specific embodiment, a fuse FU1 is connected in series between the two connection ends of the voltage transformer TV and the connected phase line. To improve the reliability of the circuit operation, two fuses FU1 can be connected to the two ends of the voltage transformer TV respectively. The specific circuit structure is as follows: Figure 2 shown.

[0041] In a more specific embodiment, the connection point between the voltage transformer TV and the three-phase bus is located between the connection point between the second circuit breaker QF2 and the three-phase bus and the connection point between the fourth contactor KM4 and the three-phase bus. Specifically, the three-phase bus is also provided with a first inductor L1 and a second inductor L2 in series; the first inductor L1 is provided in series between the connection point between the voltage transformer TV and the three-phase bus and the connection point between the fourth contactor KM4 and the three-phase bus; the second inductor L2 is provided in series between the connection point between the fourth contactor KM4 and the three-phase bus and the connection point between the first contactor KM1 and the three-phase bus.

[0042] In a more specific embodiment, Figure 4As shown, the control circuit also includes an isolation transformer T1, and the connection point between the primary side of the isolation transformer T1 and the two busbars in the three-phase busbar is located at the incoming line end of the first circuit breaker QF1; the secondary side of the isolation transformer T1 is connected to the two poles of the undervoltage release in the first circuit breaker QF1. Among them, an on-off control pin of the controller PCU is connected to a normally open auxiliary contact and a normally open dry node of the first circuit breaker QF1, and another normally open auxiliary contact of the first circuit breaker QF1 is connected to one end of the coil of the fourth contactor KM4; the other end of the coil of the fourth contactor KM4 is connected to one end of the coil of the third contactor KM3, and the connection point is connected to another normally open dry node, and the other end of the coil of the third contactor KM3 is connected to another on-off control pin of the controller PCU. 220V AC is connected between the two normally open dry nodes, and the two normally open dry nodes can be connected from the isolation transformer T1 to access the power supply, and the two normally open dry nodes can also be connected to an external power supply.

[0043] The power supply of the undervoltage release in the first circuit breaker QF1 is taken from the incoming line end of the first circuit breaker QF1. When the distribution box circuit breaker QF in the terminal extremely weak power grid is powered off, the first circuit breaker QF1 is tripped due to undervoltage, causing the normally open auxiliary contact of the first circuit breaker QF1 to be disconnected.

[0044] An on-off control pin of the controller PCU is connected to a normally open auxiliary contact and a normally open dry node of a relay of the first circuit breaker QF1, and another normally open auxiliary contact of the first circuit breaker QF1 is connected to one end of the coil of the fourth contactor KM4; the other end of the coil of the fourth contactor KM4 is connected to one end of the coil of the third contactor KM3, and the connection point is connected to another normally open dry node of a relay, and the other end of the coil of the third contactor KM3 is connected to another on-off control pin of the controller PCU; that is, the normally open dry node of the relay connected to the on-off control pin of the controller PCU is connected in series to the coils of the third contactor KM3 and the fourth contactor KM4, and at the same time, the two normally open auxiliary contacts of the first circuit breaker QF1 are also connected in series to the coils of the third contactor KM3 and the fourth contactor KM4.

[0045] The present invention discloses an unplanned power outage control circuit and control method based on a variable frequency drive device, wherein two connection ends of a voltage transformer TV are respectively connected to two phase lines in a three-phase bus, and two signal output ends of the voltage transformer TV are respectively connected to two pins of a controller PCU; a normally open auxiliary contact of a first circuit breaker QF1 is connected to an on-off control pin of the controller PCU, a coil of a third contactor KM3 and a coil of a fourth contactor KM4 are connected in parallel and in series between another normally open auxiliary contact of the first circuit breaker QF1 and another on-off control pin of the controller PCU, and two on-off control pins are connected to a normally open dry node of a relay, and the control method comprises: judging whether the voltage signal collected by the voltage transformer TV is greater than a first preset voltage value, and if so, controlling the normally open dry node of the relay to be disconnected. The above control method can cut off the capacitor C and the surge protector SPD from the current circuit when the bus is over-voltage to avoid over-voltage burning of circuit components during open-loop debugging after an unplanned power outage, thereby improving the stability of the control circuit applied to the variable frequency drive device.

[0046] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for controlling an unplanned power outage based on a variable frequency drive device, applied to a controller, wherein the controller is communicatively connected with a voltage transformer provided in an unplanned power outage control circuit based on the variable frequency drive device, characterized in that: The first circuit breaker is arranged in series in the three-phase bus of the control circuit, the two connection ends of the voltage transformer are respectively connected to the two phase lines in the three-phase bus, and the two signal output ends of the voltage transformer are respectively connected to the two pins of the controller; the second circuit breaker, the third contactor and the surge protector are connected in series between the three-phase bus and the grounding terminal, a normally open auxiliary contact of the first circuit breaker is connected to an on-off control pin of the controller, the coil of the third contactor and the coil of the fourth contactor are connected in parallel and connected in series between another normally open auxiliary contact of the first circuit breaker and another on-off control pin of the controller, and the two on-off control pins are connected to the normally open dry nodes of the relay, and the control method includes: Acquire a voltage signal collected by the voltage transformer and determine whether the voltage signal is greater than a first preset voltage value; If the voltage signal is greater than a first preset voltage value, the normally open dry node is controlled to be disconnected and the normally open auxiliary contact of the first circuit breaker is disconnected to disconnect the main contacts of the third contactor and the main contacts of the fourth contactor, and the capacitor and surge protector are cut off from the current circuit to avoid overvoltage burning of circuit components during unplanned power outages after open-loop control debugging.

2. The unplanned power outage control method based on the variable frequency drive device according to claim 1 is characterized in that: Before the normally open dry node of the control is disconnected and the normally open auxiliary contact of the first circuit breaker is disconnected, the method further includes: Determining whether the voltage signal is greater than a second preset voltage value; If the voltage signal is not greater than a second preset voltage value, executing the step of controlling the normally open dry node to be disconnected and the normally open auxiliary contact of the first circuit breaker to be disconnected; If the voltage signal is greater than the second preset voltage value, the normally open dry node of the relay is controlled to be normally closed and the normally open auxiliary contact of the first circuit breaker is controlled to be normally closed, so that the coil of the third contactor and the coil of the fourth contactor are energized, thereby avoiding the surge protector from being cut off from the current circuit when a lightning overvoltage occurs.

3. The unplanned power outage control method based on the variable frequency drive device according to claim 2 is characterized in that: The second preset voltage value is 3000V, and the first preset voltage value is 890V.

4. An unplanned power outage control circuit based on a variable frequency drive device, characterized in that: The electric control circuit applies the unplanned power outage control method based on the variable frequency drive device as described in any one of claims 1 to 3, and the control circuit includes the controller, the first circuit breaker, the voltage transformer, the second circuit breaker, the third contactor, the surge protector, the fourth contactor, the first contactor and the second contactor; one end of the three-phase bus is connected to the first circuit breaker, and the other end is connected to the rectifier module; One end of the fourth contactor is connected to the three-phase bus, and the other end is connected to the capacitor; The first contactor is arranged in series in the three-phase bus, and the first contactor is arranged in series between the first circuit breaker and the rectifier module; the second contactor is arranged in parallel at both ends of the first contactor; and a resistor is arranged in series on each of the three connecting lines connecting the second contactor to the three-phase bus.

5. The unplanned power outage control circuit based on the variable frequency drive device according to claim 4, characterized in that: A fuse is arranged in series between the two connection ends of the voltage transformer and the connected phase line.

6. The unplanned power outage control circuit based on the variable frequency drive device according to claim 4 or 5, characterized in that: The connection point between the voltage transformer and the three-phase bus is located between the connection point between the second circuit breaker and the three-phase bus and the connection point between the fourth contactor and the three-phase bus.

7. The unplanned power outage control circuit based on the variable frequency drive device according to claim 4 or 5, characterized in that: The three-phase busbar is also provided with a first inductor and a second inductor in series; The first inductor is arranged in series between the connection point between the voltage transformer and the three-phase bus and the connection point between the fourth contactor and the three-phase bus; The second inductor is arranged in series between a connection point between the fourth contactor and the three-phase bus and a connection point between the first contactor and the three-phase bus.

8. The unplanned power outage control circuit based on the variable frequency drive device according to claim 6, characterized in that: The control circuit further includes an isolation transformer, wherein the connection point between the primary side of the isolation transformer and two of the three-phase busbars is located at the incoming line end of the first circuit breaker; The secondary side of the isolation transformer is connected to the two poles of the undervoltage release in the first circuit breaker.

9. The unplanned power outage control circuit based on the variable frequency drive device according to claim 4 or 5, characterized in that: An on-off control pin of the controller is connected to a normally open dry node and a normally open auxiliary contact of the first circuit breaker, and another normally open auxiliary contact of the first circuit breaker is connected to one end of the coil of the fourth contactor; the other end of the coil of the fourth contactor is connected to one end of the coil of the third contactor, and the connection point is connected to another normally open dry node, and the other end of the coil of the third contactor is connected to another on-off control pin of the controller.

10. The unplanned power outage control circuit based on the variable frequency drive device according to claim 4 or 5, characterized in that: The threshold voltage of the surge protector is 908.7V.

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