A shutdown control method for an inverter feedback device

Abstract

The present invention provides a shutdown control method for an inverter feedback device, which relates to the technical field of shutdown control and includes: S1. When the inverter feedback device is undergoing shutdown processing, obtain the DC voltage of the inverter feedback device, and determine whether the DC voltage is lower than the normal startup voltage of the inverter feedback device. If so, execute S2; S2. Obtain the current number of operating inverter units of the inverter feedback device. If the current number of operating units is 1, shut down the entire inverter feedback device. Otherwise, execute S3; S3. Calculate the current change value of the DC voltage of the inverter feedback device and the shutdown processing duration, and determine the current number of operating inverter units based on the DC voltage change value and the shutdown processing duration; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units; S4. Clear the DC voltage change value and the shutdown processing duration, and return to execute S2. The present invention can reduce the impact on the DC traction network when the inverter feedback device shuts down.

Description

Technical Field

[0001] The present invention belongs to the technical field of shutdown control, and particularly relates to a shutdown control method for an inverter feedback device. Background Art

[0002] With the increasing congestion of urban traffic, subways, as a means of transportation to relieve urban traffic congestion and improve people's travel modes, are operating in major cities. The energy feedback devices of traditional subways usually use resistors for absorption, resulting in problems such as energy waste. Among all types of energy feedback devices, the inverter feedback device has better energy-saving effects and is the main research direction for the current development of subways.

[0003] For an inverter feedback device based on a three-level NPC topology structure, when the number of parallel units in the inverter feedback device is relatively large, the shutdown power of the device is large, and the instantaneous shutdown action will cause a certain impact and oscillation on the DC traction network, which is likely to cause equipment damage. Summary of the Invention

[0004] Aiming at the above deficiencies of the prior art, the present invention provides a shutdown control method for an inverter feedback device to solve the above technical problems.

[0005] The present invention provides a shutdown control method for an inverter feedback device, including:

[0006] S1. When the shutdown process of the inverter feedback device is carried out, obtain the DC voltage of the inverter feedback device, and judge whether the DC voltage is lower than the normal startup voltage of the inverter feedback device. If so, execute S2;

[0007] S2. Obtain the current number of operating inverter units of the inverter feedback device. If the current number of operating units is 1, shut down the entire inverter feedback device. Otherwise, execute S3;

[0008] S3. Calculate the DC voltage change value and the shutdown process duration of the current inverter feedback device, determine the current number of operating inverter units according to the DC voltage change value and the shutdown process duration; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units;

[0009] S4. Clear the DC voltage change value and the shutdown process duration, and return to execute S2.

[0010] Furthermore, before S1, it further includes:

[0011] Obtain the total number of inverter units that are normally operating in the inverter feedback device;

[0012] Take the difference between the shutdown voltage and the startup voltage of the inverter feedback device as the hysteresis voltage, and divide the hysteresis voltage by the total number of inputs as the voltage threshold.

[0013] Further, S1 further includes:

[0014] Determine the hysteresis time of the inverter feedback device through the exit time of each inverter unit, and divide the inverse hysteresis time by the total number of inputs as the time threshold.

[0015] Further, S3 includes:

[0016] When the change value of the DC voltage reaches the voltage threshold, subtract 1 from the number of inputs as the first quantity of the inverter unit operation; when the shutdown processing duration reaches the time threshold, subtract 1 from the number of inputs as the second quantity of the inverter unit operation;

[0017] Select the minimum value of the first quantity and the second quantity as the current number of operating inverter units; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operations.

[0018] The beneficial effects of the present invention are as follows: when the DC voltage is lower than the startup voltage of the inverter feedback device, the number of operating inverter units in the inverter feedback device is reduced according to the change of the DC voltage and the shutdown processing duration; it can reduce the impact on the DC traction network when the inverter feedback device shuts down, prevent the problem of large fluctuations in the DC voltage, and at the same time prevent the problem that the DC side voltage is in the hysteresis voltage range for a long time, resulting in the equipment being unable to exit the operation, ensuring the safe and reliable operation of the equipment.

[0019] In addition, the design principle of the present invention is reliable, the structure is simple, and it has a very wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 is a schematic structural diagram of the existing inverter feedback device of the present invention.

[0022] Figure 2 is a schematic flow chart of a control method provided by an embodiment of the present invention.

[0023] Figure 3 is a relationship diagram between the number of operating inverter units and the change of DC voltage in an embodiment of the present invention.

[0024] Figure 4 is a relationship diagram between the number of operating inverter units and the shutdown time in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] As Figure 1 shown is a structural diagram of an inverter feedback device. All the inverter units in this device adopt a three-level NPC topology structure. The inverter units are connected in parallel to improve the overall operating power. There is a minimum operating current for the unit in this device, which is mainly used for three-level voltage equalization control to ensure the stable operation of the device. Therefore, when the device shuts down, it cannot be reduced to zero before shutting down. Usually, it shuts down when it is reduced to this minimum operating current. When the number of parallel units in the inverter feedback device is relatively large, the power is relatively large when the device shuts down, and a sudden shutdown will cause a certain impact on the DC traction network and problems such as voltage fluctuations will occur.

[0027] For the above structure, this embodiment provides a method for controlling the shutdown of an inverter feedback device, which is characterized by including:

[0028] S1. When the inverter feedback device is being shut down, obtain the DC voltage of the inverter feedback device, and determine whether the DC voltage is lower than the normal startup voltage of the inverter feedback device. If so, execute S2;

[0029] S2. Obtain the current number of operating inverter units of the inverter feedback device. If the current number of operating units is 1, shut down the entire inverter feedback device; otherwise, execute S3;

[0030] S3. Calculate the change value of the DC voltage and the shutdown processing duration of the current inverter feedback device, and determine the current number of operating inverter units according to the change value of the DC voltage and the shutdown processing duration; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units;

[0031] S4. Clear the change value of the DC voltage and the shutdown processing duration, and return to execute S2.

[0032] It should be noted that this embodiment is a method that executes in a loop according to S2 - S4. In this embodiment, the first calculation of both the DC voltage change value and the shutdown processing duration is triggered at the moment when the DC voltage is lower than the startup voltage, and then both are recalculated synchronously at the start of each loop. In the shutdown control method of an inverter feedback device according to an embodiment of the present invention, when the inverter feedback device shuts down, the inverter units are withdrawn one by one, and the control of withdrawing units one by one is restricted by voltage conditions and time conditions; the control of withdrawing units one by one being restricted by voltage conditions includes that when the DC voltage of the inverter feedback device drops below the startup voltage, the number of operating units is gradually reduced according to the DC voltage change value. When withdrawing units one by one, the condition restriction is that when the DC voltage of the inverter feedback device drops below the startup voltage, the device starts timing, and for every certain increase in time, the number of operating inverter units is correspondingly reduced. The number of operating units determined by combining the voltage condition restriction and the time condition restriction is compared, and finally the smaller relative value is executed.

[0033] Optionally, as an embodiment of the present invention, before S1, it further includes: obtaining the total number of inverter units that are normally operating in the inverter feedback device; using the difference between the startup voltage and the shutdown voltage of the inverter feedback device as the hysteresis voltage, and dividing the hysteresis voltage by the total number of units as the voltage threshold.

[0034] Optionally, as an embodiment of the present invention, S1 further includes: determining the hysteresis time of the inverter feedback device based on the withdrawal time of each inverter unit, and dividing the inverse hysteresis time by the total number of units as the time threshold.

[0035] Optionally, as an embodiment of the present invention, S3 includes: when the DC voltage change value reaches the voltage threshold, subtracting 1 from the number of inputs as the first number of operating inverter units; when the shutdown processing duration reaches the time threshold, subtracting 1 from the number of inputs as the second number of operating inverter units; selecting the minimum value between the first number and the second number as the current number of operating inverter units; controlling the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units.

[0036] It should be noted that in the embodiments of the present invention, adding the condition restriction of the hysteresis time can effectively prevent the DC voltage from being in the hysteresis voltage range for a long time. Because when the DC voltage is in the hysteresis voltage range for a long time, the device operates in the minimum operating current state for a long time and does not withdraw, and this situation is not allowed to exist. Therefore, by increasing the hysteresis time, when entering the voltage hysteresis and the time reaches a certain value, the units are forced to withdraw one by one.

[0037] For the convenience of understanding the present invention, the shutdown control method of the inverter feedback device provided by the present invention will be further described below by taking an inverter feedback device based on a three - level NPC topology structure as an example.

[0038] Obtain the total number of inverter units n that are put into operation normally in the inverter feedback device, as well as the shutdown voltage U1 and startup voltage U2 of the inverter feedback device. Among them, the shutdown voltage U1 is the voltage when the inverter feedback device is about to shut down. When the entire device reaches the shutdown voltage U1, only one inverter unit should be running in the inverter feedback device; when the DC voltage U d is lower than the startup voltage U2, the device starts to reduce the number of running units, that is, when the voltage is below the startup voltage U2, the number of units put into operation only decreases and does not increase; when the DC voltage reaches above the startup voltage U2, all units are put into operation. Therefore, the startup voltage U2 is the voltage of the device when n - 1 units operate with the minimum current. As Figure 2 shown, the specific control method is as follows.

[0039] S1. When dealing with the shutdown of the inverter feedback device, obtain the DC voltage U d of the inverter feedback device. When the DC voltage U d is higher than the startup voltage U2, all inverter units of the device will be put into operation. As the DC voltage U d increases, the operating power of the units will gradually increase until the DC voltage U d reaches the full-power voltage U3, and the device operates at full power. Determine whether the DC voltage U d is lower than the normal startup voltage U2 of the inverter feedback device. If so, execute S2.

[0040] S2. Obtain the current number of running inverter units in the inverter feedback device. If the current number of running units is 1, shut down the entire inverter feedback device; otherwise, execute S3.

[0041] S3. Calculate the current DC voltage change value and shutdown processing duration of the inverter feedback device, and determine the current number of running inverter units according to the DC voltage change value and shutdown processing duration; control the inverter feedback device to reduce the number of running inverter units according to the current number of running units.

[0042] As Figure 3 , Figure 4 shown, take the difference between the shutdown voltage U1 and the startup voltage U2 of the inverter feedback device as the hysteresis voltage, that is, the hysteresis voltage is △U = U2 - U1. Divide the hysteresis voltage △U into n equal parts, and △U / n is the voltage threshold; divide the hysteresis time △S by the total number of inputs n as the time threshold △S / n. Specifically, starting from the startup voltage U2, for every decrease of △U / n in the DC voltage, determine to withdraw one inverter unit; start timing from when the DC voltage drops to the startup voltage. At this time, one inverter unit has already been withdrawn. For every arrival of △S / n in time, withdraw one inverter unit.

[0043] In one implementation, the sum of the turn-off times of each inverter unit is used as the hysteresis time of the inverter feedback device. That is, if the turn-off time of each inverter unit is defined as t, then the hysteresis time △S is tn. That is, the time threshold can be the turn-off time t of the inverter unit. When the change value of the DC voltage reaches the voltage threshold, the input number n minus 1 is used as the first number n of operating inverter units U When the shutdown processing duration reaches the time threshold, the input number minus 1 is used as the second number n of operating inverter units S .

[0044] Compare the first number n U and the second number n S , and take the smaller value between the two as the current number of operating inverter units; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units

[0045] S4. Clear the change value of the DC voltage and the shutdown processing duration, and return to execute S2

[0046] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims

Claims

1. A shutdown control method for an inverter feedback device, characterized in that Including: S1. When the inverter feedback device is shut down, obtain the DC voltage of the inverter feedback device, and determine whether the DC voltage is lower than the normal starting voltage of the inverter feedback device. If so, execute S2; S2. Obtain the current number of operating inverter units of the inverter feedback device. If the current number of operating units is 1, shut down the entire inverter feedback device; otherwise, execute S3; S3. Calculate the DC voltage change value and the shutdown processing duration of the current inverter feedback device. When the DC voltage change value reaches the voltage threshold, subtract 1 from the number of input units as the first number of operating inverter units; when the shutdown processing duration reaches the time threshold, subtract 1 from the number of input units as the second number of operating inverter units; Select the minimum value of the first number and the second number as the current number of operating inverter units; control the inverter feedback device to reduce the number of operating inverter units according to the current number of operating units; S4. Clear the DC voltage change value and the shutdown processing duration, and return to execute S2.

2. The method according to claim 1, characterized in that, Before S1, it further includes: Obtain the total number of input inverter units operating normally in the inverter feedback device; Take the difference between the starting voltage and the shutdown voltage of the inverter feedback device as the hysteresis voltage, and divide the hysteresis voltage by the total number of input units as the voltage threshold.

3. The method according to claim 2, wherein S1 further includes: Determine the hysteresis time of the inverter feedback device through the shutdown time of each inverter unit, and divide the inverse hysteresis time by the total number of input units as the time threshold.

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