Abnormal detection method for bridge arm switching number in flexible DC converter valve control system

Abstract

The present invention discloses a method for detecting abnormal switching numbers of bridge arms in a flexible DC converter valve control system. The method comprises: obtaining the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the double frequency circulating current component of each bridge arm included in the first bridge arm group; using the main controller to determine the sum of the switching numbers of the first bridge arm group as the first switching number, and using the backup controller to determine the sum of the switching numbers of the first bridge arm group as the second switching number; respectively judging whether the first switching number and the second switching number exceed a predetermined first calibration range; when at least one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality occurs in the main controller and / or the backup controller. The present invention solves the technical problem that the flexible DC converter valve control system cannot determine whether an abnormality occurs in the valve control system itself when determining the actual switching number of the bridge arm.

Description

Technical Field

[0001] The present invention relates to the field of power equipment maintenance, and in particular to a method for detecting abnormal switching number of bridge arms in a flexible direct current (HVDC) converter valve control system. Background Art

[0002] In related technologies, after receiving the bridge arm reference wave from the pole control system, the DC converter valve control system directly calculates the actual number of bridge arms switched according to a conversion formula and uses this actual number of bridge arms to directly control bridge arm switching. However, if the converted number of a bridge arm is incorrect due to a memory error in the valve control host or the bridge arm control chassis board during the conversion process, this can cause disorder in the converter valve bridge arm switching control, resulting in bridge arm overcurrent and triggering DC system lockout and tripping.

[0003] To address the above-mentioned problems, no effective solutions have been proposed so far. Summary of the Invention

[0004] An embodiment of the present invention provides a method for detecting abnormal switching number of bridge arms in a flexible DC converter valve control system, so as to at least solve the technical problem that the flexible DC converter valve control system cannot determine whether the valve control system itself has abnormality when determining the actual switching number of bridge arms.

[0005] According to one aspect of an embodiment of the present invention, a method for detecting abnormal switching numbers of bridge arms in a valve control system of a flexible DC converter valve is provided, comprising: obtaining a rated DC voltage of the converter valve, a switching reference value of the converter valve, a reference wave of each bridge arm included in a first bridge arm group, and a double frequency circulating current component of each bridge arm included in the first bridge arm group, wherein the bridge arms included in the first bridge arm group are an upper bridge arm and a lower bridge arm with the same phase; determining, using a primary controller, as a first switching number, and determining, using a backup controller, as a second switching number, the sum of the switching numbers of the first bridge arm group based on the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the double frequency circulating current component of each bridge arm included in the first bridge arm group; respectively determining whether the first switching number and the second switching number exceed a predetermined first calibration range; and determining that an abnormality has occurred in the primary controller and / or the backup controller if at least one of the first switching number and the second switching number exceeds the first calibration range.

[0006] Optionally, when at least one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality occurs in the main controller and / or the standby controller, includes: when only one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality occurs in the controller corresponding to the switching number that exceeds the first calibration range; judging whether the abnormal controller is being used for control; and when the abnormal controller is being used for control, requesting to switch the controller for control.

[0007] Optionally, it also includes: when the first switching number and the second switching number both exceed the first verification range, obtaining the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, wherein the bridge arms included in the second bridge arm group are upper bridge arms and lower bridge arms of the same phase, the bridge arms included in the third bridge arm group are upper bridge arms and lower bridge arms of the same phase, and the bridge arms included in the second bridge arm group, the bridge arms included in the first bridge arm group, and the bridge arms included in the third bridge arm group are of different phases; according to the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, the first switching number or the second switching number is corrected; and the corrected switching number is used to control the switching of the bridge arms included in the first bridge arm group.

[0008] Optionally, the first switching number or the second switching number is corrected according to the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, including: determining the difference between the switching number of the upper bridge arm included in the second bridge arm group and the switching number of the lower bridge arm included in the second bridge arm group according to the switching number of each bridge arm included in the second bridge arm group; determining the difference between the switching number of the upper bridge arm included in the third bridge arm group and the switching number of the lower bridge arm included in the third bridge arm group according to the switching number of each bridge arm included in the third bridge arm group; determining the number of AC components of the second bridge arm group according to the difference between the switching number of the upper bridge arm included in the second bridge arm group and the switching number of the lower bridge arm; determining the number of AC components of the third bridge arm group according to the difference between the switching number of the upper bridge arm included in the third bridge arm group and the switching number of the lower bridge arm; determining the number of AC components of the first bridge arm group according to the AC component number of the second bridge arm group and the AC component number of the third bridge arm group; correcting the first switching number or the second switching number according to the AC component number of the first bridge arm group.

[0009] Optionally, the first switching number or the second switching number is corrected according to the number of AC components of the first bridge arm group, including: determining the switching number corresponding to the upper bridge arm included in the first bridge arm group and the switching number corresponding to the lower bridge arm included in the first bridge arm group in the first switching number or the second switching number; judging whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; if the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal, correcting the switching number corresponding to the upper bridge arm included in the first bridge arm group according to the number of AC components of the first bridge arm group, the rated DC voltage of the converter valve and the switching reference value of the converter valve; or judging whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal; if the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal, correcting the switching number corresponding to the lower bridge arm included in the first bridge arm group according to the number of AC components of the first bridge arm group, the rated DC voltage of the converter valve and the switching reference value of the converter valve.

[0010] Optionally, judging whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal includes: determining the second calibration range according to the number of AC components of the first bridge arm group, the predetermined limit value of the double-frequency circulating current component, the rated DC voltage of the converter valve and the switching reference value of the converter valve; when the switching number corresponding to the upper bridge arm included in the first bridge arm group exceeds the second calibration range, determining that the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; judging whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal includes: when the switching number corresponding to the upper bridge arm included in the first bridge arm group is within the second calibration range, determining that the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal.

[0011] Optionally, the first calibration range is determined by the following steps: simulating the bridge arm switching system to determine the limit value of the double frequency circulating current component in the bridge arm switching system; determining the first calibration range based on the limit value of the double frequency circulating current component, the rated DC voltage of the converter valve and the converter valve switching reference value.

[0012] In an embodiment of the present invention, by obtaining the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the double frequency circulating current component of each bridge arm included in the first bridge arm group, wherein the bridge arms included in the first bridge arm group are the upper bridge arm and the lower bridge arm of the same phase; according to the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the double frequency circulating current component of each bridge arm included in the first bridge arm group, the main controller is used to determine the sum of the switching numbers of the first bridge arm group as the first switching number, and the backup controller is used to determine the sum of the switching numbers of the first bridge arm group as the first switching number. and is the second switching number; whether the first switching number and the second switching number exceed a predetermined first verification range is determined respectively; when at least one of the first switching number and the second switching number exceeds the first verification range, it is determined that an abnormality occurs in the main controller and / or the standby controller, thereby achieving the purpose of performing abnormality detection on the bridge arm switching number calculated by the DC converter valve control system, thereby realizing the technical effect of identifying data abnormalities when determining the actual switching number of the bridge arm, and further solving the technical problem that the flexible DC converter valve control system cannot determine whether an abnormality occurs in the valve control system itself when determining the actual switching number of the bridge arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0014] Figure 1 4 is a flow chart of a method for detecting abnormality in the number of bridge arm switching provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0016] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0017] According to an embodiment of the present invention, an embodiment of a method for detecting an abnormal switching number of bridge arm submodules of a flexible DC converter valve is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0018] Figure 1 FIG. 1 is a flow chart of a method for detecting abnormality in the number of bridge arm switching operations according to an embodiment of the present invention. Figure 1 As shown, the method includes the following steps:

[0019] Step S202: Obtain the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the doubled frequency circulating current component of each bridge arm included in the first bridge arm group, wherein the bridge arms included in the first bridge arm group are the upper bridge arm and the lower bridge arm with the same phase.

[0020] A flexible DC converter valve control system typically has three phases, each of which consists of an upper arm and a lower arm. In other words, the entire flexible DC converter valve control system typically includes six arms, enabling DC voltage and current control. In this step, the number of arms switched on and off for a particular phase can be verified, allowing the relevant parameters of only the upper arm of a particular phase to be obtained.

[0021] In step S204, based on the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the doubled frequency circulating current component of each bridge arm included in the first bridge arm group, the main controller is used to determine that the sum of the switching numbers of the first bridge arm group is a first switching number, and the backup controller is used to determine that the sum of the switching numbers of the first bridge arm group is a second switching number.

[0022] In related technologies, during the arm switching control process, the valve control system of the flexible DC converter valve receives the reference wave of each bridge arm sent by the pole control system. The valve control system host or the bridge arm controller superimposes the doubled frequency circulating current component on the reference wave. The actual switching number of the six bridge arms is calculated according to the following formula to obtain the actual switching number of each bridge arm:

[0023]

[0024] Where U dc is the rated DC voltage of the converter valve, N t is the switching reference value of the converter valve, & represents ap (upper bridge arm of phase a), an (lower bridge arm of phase a), bp (upper bridge arm of phase b), bn (lower bridge arm of phase b), cp (upper bridge arm of phase c), cn (lower bridge arm of phase c), U ref& is the reference wave of bridge arm &, U 2ref& is the double frequency circulating current component of bridge arm &. The double frequency circulating current components of the same-phase bridge arms are the same, that is, the double frequency circulating current components of each phase are the same.

[0025] In this step, the main controller and the backup controller in the valve control system will be used simultaneously to perform the above calculations to obtain the actual switching number of each bridge arm, and then the actual switching number of the upper bridge arm and the actual switching number of the lower bridge arm of a phase circuit are added together to obtain the sum of the switching numbers of the phase circuit, wherein the calculation result of the main controller can be the first switching number, and the calculation result of the backup controller can be the second switching number.

[0026] Step S206: determining whether the first switching number and the second switching number exceed a predetermined first checking range.

[0027] Since the valve control system in the related art does not perform self-checking operations after calculating the results, problems in the calculation program of the main controller and / or the backup controller cannot be discovered in time. If the wrong calculation results are used for switching, it will cause bridge arm overcurrent, triggering the DC system to lock and trip.

[0028] In this step, the first switching number calculated by the main controller can be verified, and the second switching number calculated by the standby controller can also be verified to determine whether the first switching number and the second switching number exceed the predetermined first verification range, thereby realizing self-checking of the calculation results of the valve control system.

[0029] Step S208 : When at least one of the first switching number and the second switching number exceeds a first calibration range, it is determined that an abnormality occurs in the active controller and / or the standby controller.

[0030] In this step, if both the first switching number and the second switching number are within the first calibration range, it can be determined that both the active controller and the backup controller are functioning properly, and switching control can be performed according to the calculation result of the controller currently controlling the valve control system. If at least one of the first switching number and the second switching number exceeds the first calibration range, at least one of the active controller and / or the backup controller has experienced an abnormality.

[0031] Through the above steps, the purpose of detecting anomalies in the number of bridge arm switching calculated by the DC converter valve control system can be achieved, thereby realizing the technical effect of identifying data anomalies when determining the actual number of bridge arm switching, and further solving the technical problem that the flexible DC converter valve control system cannot determine whether the valve control system itself has an abnormality when determining the actual number of bridge arm switching.

[0032] As an optional embodiment, when at least one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality has occurred in the main controller and / or the standby controller includes: when only one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality has occurred in the controller corresponding to the switching number that exceeds the first calibration range; judging whether the abnormal controller is being used for control; and when the abnormal controller is being used for control, requesting to switch the controller for control.

[0033] Optionally, when calibrating the first switching number, if the first switching number exceeds the first calibration range, it means that the main controller has an abnormality. Similarly, if the second switching number exceeds the second calibration range, it means that the backup controller has an abnormality. If it is determined based on the first switching number and the second switching number that only one of the two controllers has an abnormality, it can be determined whether the current system is being controlled by the abnormal controller. If not, only the abnormal controller can be marked. If so, a request can be made to switch from the abnormal controller to a normal controller and mark the abnormal controller. For example, if the current valve control system is using the main controller and it is detected that the first switching number exceeds the first calibration range and the second switching number does not exceed the first calibration range, the main controller can be marked as abnormal and a request can be made to switch to the backup controller; if it is detected that the second switching number exceeds the first calibration range and the first switching number does not exceed the first calibration range, the main controller can continue to be used and only the backup controller can be marked as abnormal.

[0034] As an optional embodiment, the first calibration range is determined by the following steps: simulating the bridge arm switching system to determine the limit value of the double frequency circulating current component in the bridge arm switching system; determining the first calibration range based on the limit value of the double frequency circulating current component, the rated DC voltage of the converter valve and the converter valve switching reference value.

[0035] Optionally, the bridge arm switching system and the associated flexible DC project can be simulated. Based on the relevant engineering parameters of the flexible DC project, a simulation model of the flexible DC project can be established in the simulation system, including components such as the DC power supply, inverter, and filter. The power supply voltage, inverter parameters, and filter parameters can then be set based on the specific design parameters of the flexible DC project. It is important to note that the inverter's PWM modulation method is set to double-frequency modulation. After the simulation model is established, it can be run to obtain the output waveform of the flexible DC project. The output waveform can then be analyzed to find the maximum value of the double-frequency circulating current component, which is the limit value of the double-frequency circulating current component in the bridge arm switching system.

[0036] After the limit value of the double frequency circulating current component in the bridge arm switching system is determined by simulation, the first calibration range can be taken as Among them, U 2refmax It is the limit value (maximum value) of the double frequency circulating current component.

[0037] As an optional embodiment, it also includes: when the first switching number and the second switching number both exceed the first verification range, obtaining the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, wherein the bridge arms included in the second bridge arm group are upper bridge arms and lower bridge arms of the same phase, the bridge arms included in the third bridge arm group are upper bridge arms and lower bridge arms of the same phase, and the bridge arms included in the second bridge arm group, the bridge arms included in the first bridge arm group, and the bridge arms included in the third bridge arm group are of different phases; according to the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, the first switching number or the second switching number is corrected; and the corrected switching number is used to control the switching of the bridge arms included in the first bridge arm group.

[0038] Optionally, if both the first switching number and the second switching number exceed the first calibration range, it can be considered that both the primary and backup controllers have experienced an anomaly, and both the primary and backup controllers can be marked. However, in this case where neither the primary nor the backup controller is trustworthy, there are no normally available switching numbers to guide the actual switching operation. Therefore, the first or second switching number can be corrected, and the corrected switching number can be used to control the switching of the bridge arm. In actual operation, for convenience, the controller currently in use by the bridge arm switching system can be kept unchanged, the switching number obtained by the current controller can be corrected, and the corrected switching number can be used to control the actual switching operation.

[0039] As mentioned above, the bridge arm switching system usually includes three-phase circuits. If the bridge arm switching number of a phase circuit to which the first bridge arm group belongs is calculated incorrectly, the normal bridge arm switching numbers of the other two-phase circuits can be used to correct the abnormal bridge arm switching number. The switching numbers of the respective bridge arms included in the second bridge arm group and the switching numbers of the respective bridge arms included in the third bridge arm group are the normal bridge arm switching numbers of the other two-phase circuits.

[0040] As an optional embodiment, the first switching number or the second switching number is corrected according to the switching numbers of the bridge arms included in the second bridge arm group and the switching numbers of the bridge arms included in the third bridge arm group, including: determining the difference between the switching numbers of the upper bridge arm and the switching numbers of the lower bridge arm included in the second bridge arm group according to the switching numbers of the bridge arms included in the second bridge arm group; determining the difference between the switching numbers of the upper bridge arm and the switching numbers of the lower bridge arm included in the third bridge arm group according to the switching numbers of the bridge arms included in the third bridge arm group; determining the number of AC components of the second bridge arm group according to the difference between the switching numbers of the upper bridge arm and the switching numbers of the lower bridge arm included in the second bridge arm group; determining the number of AC components of the third bridge arm group according to the difference between the switching numbers of the upper bridge arm and the switching numbers of the lower bridge arm included in the third bridge arm group; determining the number of AC components of the first bridge arm group according to the AC component numbers of the second bridge arm group and the AC component numbers of the third bridge arm group; and correcting the first switching number or the second switching number according to the AC component number of the first bridge arm group.

[0041] Alternatively, the normal switching numbers of the bridge arms belonging to the other two-phase circuits can be obtained first, that is, the switching numbers of the bridge arms included in the second bridge arm group and the switching numbers of the bridge arms included in the third bridge arm group. In other words, the sum of the switching numbers of the upper bridge arms and the switching numbers of the lower bridge arms of the second bridge arm group and the third bridge arm group is within the first verification range. Since the difference N between the switching numbers of the upper bridge arm and the switching numbers of the lower bridge arm in each phase circuit is K* The AC component number U of the reference wave of the phase circuit refac* There is a relationship as shown in the following formula:

[0042] N K* =n num*p -n num*n =2U refac* ×N t ;

[0043] In the formula, it is assumed that the three-phase circuits are phase a, phase b, and phase c, * can represent a, b, and c, the subscript p represents the upper bridge arm, and n represents the lower bridge arm. The above formula shows that in a certain phase circuit, the switching number n of the upper bridge arm is num*p Subtract the number of switching on and off of the lower bridge arm of the phase circuit n num*n The difference N between the switching number of the upper bridge arm and the switching number of the lower bridge arm is obtained. K*, which is equal to the AC component number U of the reference wave of the phase circuit of the phase circuit refac* Double the switching reference value N of the converter valve t .

[0044] That is to say, the difference between the switching number of the upper bridge arm and the switching number of the lower bridge arm included in the second bridge arm group can be determined first, and then the above formula can be used to calculate the number of AC components of a phase circuit corresponding to the second bridge arm group. Similarly, the number of AC components of the third bridge arm group can also be determined in the same way.

[0045] Since the number of AC components in the three-phase circuit (phase a, phase b, and phase c) is U refac* Satisfy the following formulas respectively:

[0046] U refaca =U refacM cos(wt)+U refac3M cos(3wt);

[0047] U refacb =U refacM cos(wt+120°)+U refac3M cos(3wt);

[0048] U refacc =U refacM cos(wt+240°)+U refac3M cos(3wt);

[0049] Where w is the angular frequency of the three-phase circuit, t is the time, and the number of AC components U is refac* The fundamental amplitude is U refacM , the third harmonic amplitude is U refac3M , and because the three-phase phase difference is 120°, for some flexible DC projects without third harmonic injection, the third harmonic amplitude U refac3M = 0, for some flexible DC projects with injected third harmonic, the third harmonic amplitude U refac3M =kU refacM , k is a fixed known number.

[0050] According to the above three and the number of AC components U in the three-phase circuit refac* The relevant formula can be used to calculate the AC component number of the other phase circuit when the AC component number of two phase circuits in a three-phase circuit is known. Therefore, the AC component number of the first bridge arm group can be determined by the AC component number of the second bridge arm group and the AC component number of the third bridge arm group, and then the first switching number or the second switching number can be corrected according to the AC component number of the first bridge arm group.

[0051] As an optional embodiment, the first switching number or the second switching number is corrected according to the number of AC components of the first bridge arm group, including: determining the switching number corresponding to the upper bridge arm included in the first bridge arm group and the switching number corresponding to the lower bridge arm included in the first bridge arm group in the first switching number or the second switching number; judging whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; if the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal, correcting the switching number corresponding to the upper bridge arm included in the first bridge arm group according to the number of AC components of the first bridge arm group, the rated DC voltage of the converter valve and the switching reference value of the converter valve; or judging whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal; if the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal, correcting the switching number corresponding to the lower bridge arm included in the first bridge arm group according to the number of AC components of the first bridge arm group, the rated DC voltage of the converter valve and the switching reference value of the converter valve.

[0052] Optionally, when correcting the first switching number or the second switching number, since the first switching number and the second switching number both include the switching number of the upper bridge arm and the switching number of the lower bridge arm, in this case it can be determined whether the problem specifically occurs with the switching number of the upper bridge arm or the switching number of the lower bridge arm, and then different formulas are used to correct the switching number of the upper bridge arm or the switching number of the lower bridge arm.

[0053] If the switching number of the upper bridge arm is abnormal, the expected switching number N of the upper bridge arm can be determined according to the following formula: S第一p and the expected switching number N of the upper bridge arm S第一p As the corrected upper arm switching number:

[0054]

[0055] Where, the AC component of the first bridge arm group is U refac第一 .

[0056] If the switching number of the lower bridge arm is abnormal, the expected switching number N of the lower bridge arm can be determined according to the following formula: S第一n and the expected switching number N of the lower bridge arm S第一n As the corrected lower arm switching number:

[0057]

[0058] Where, the AC component of the first bridge arm group is U refac第一 .

[0059] As an optional embodiment, judging whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal includes: determining the second calibration range according to the number of AC components of the first bridge arm group, the predetermined limit value of the double-frequency circulating current component, the rated DC voltage of the converter valve and the switching reference value of the converter valve; when the switching number corresponding to the upper bridge arm included in the first bridge arm group exceeds the second calibration range, determining that the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; judging whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal includes: when the switching number corresponding to the upper bridge arm included in the first bridge arm group is within the second calibration range, determining that the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal.

[0060] Optionally, a second verification range may be predetermined, and by determining whether the switching count corresponding to the upper bridge arm included in the first bridge arm group exceeds the second verification range, it is determined whether the problem occurs with the switching count of the upper bridge arm or the switching count of the lower bridge arm. Specifically, when the switching count corresponding to the upper bridge arm included in the first bridge arm group exceeds the second verification range, the problem occurs with the switching count of the upper bridge arm; when the switching count corresponding to the upper bridge arm included in the first bridge arm group is within the second verification range, the problem occurs with the switching count of the lower bridge arm.

[0061] The second calibration range can be U refac第一 is the number of AC components of the first bridge arm group, U 2refmax It is the limit value (maximum value) of the double frequency circulating current component.

[0062] As a specific embodiment, the solution provided by the present invention may include the following steps when implemented:

[0063] Step 1: The valve control system receives the reference wave U of each bridge arm sent by the pole control system ref& Then, the double frequency circulating current component U of each bridge arm is superimposed in the valve control system host or bridge arm controller. 2ref& , get the actual switching number n of each bridge arm num& .

[0064] Step 2: At the valve control host or bridge arm controller or core board, add the input numbers of the upper and lower bridge arms of the same phase to get N J* , for N J* Perform calibration and take the calibration range as where N t is the switching reference value of the converter valve, U 2refmax is the limit value (maximum value) of the double frequency circulating current component obtained through simulation, U dc is the rated DC voltage of the converter valve.

[0065] Step 3: Case 1: If the valve control main controller and the backup controller calculate N J*If all are within the calibration range, the valve control system determines that the number of bridge arm switching is normal.

[0066] Case 2: If the N calculated by the valve control main controller and the backup controller is J* If one of them is within the calibration range, the other controller determines that the number of bridge arm switching is abnormal, sets the controller to be unavailable, and requests the controller to switch.

[0067] Case 3: If the active controller and the standby controller calculate N J* If none of them are within the calibration range, the original controller will be kept running, a serious alarm of the valve control system will be set, and a prompt will be given that the number of switching on and off of the bridge arm of this phase is abnormal, and steps 4, 5 and 6 will be continued.

[0068] Step 4: Assume that the bridge arm group with abnormality is the first bridge arm group, and the other two bridge arms that passed the verification are the second bridge arm group and the third bridge arm group. Calculate the difference N between the switching number of the upper bridge arm and the switching number of the lower bridge arm in the switching number of the second bridge arm group and the third bridge arm group. K第二 and N K第三 , and calculate the AC component number U of the two phases based on this refac第二 and U refac第三 .

[0069] Step 5: Calculate the AC quantity U of the switching number of the first bridge arm group that has not passed the verification refac第一 .

[0070] Step 6: The switching number n of the upper bridge arm in the switching number of the first bridge arm group that has not passed the verification num第一p Check, if If the switching number of the lower bridge arm is within the range, it means that the switching number of the lower bridge arm is abnormal. The switching number of the lower bridge arm adopts the expected value N S第一n Control, where If the switching number of the upper bridge arm is not If the switching number of the upper bridge arm is within the range, it means that the switching number of the upper bridge arm is abnormal, and the switching number of the upper bridge arm adopts the expected value N S第一p Control, where

[0071] It should be noted that for the aforementioned method embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, because according to the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0072] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0073] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for detecting abnormal switching number of bridge arms in a flexible DC converter valve control system, characterized in that: include: Acquire a rated DC voltage of the converter valve, a switching reference value of the converter valve, a reference wave of each bridge arm included in the first bridge arm group, and a doubled frequency circulating current component of each bridge arm included in the first bridge arm group, wherein the bridge arms included in the first bridge arm group are an upper bridge arm and a lower bridge arm with the same phase; Based on the rated DC voltage of the converter valve, the switching reference value of the converter valve, the reference wave of each bridge arm included in the first bridge arm group, and the doubled frequency circulating current component of each bridge arm included in the first bridge arm group, a main controller is used to determine that the sum of the switching numbers of the first bridge arm group is a first switching number, and a backup controller is used to determine that the sum of the switching numbers of the first bridge arm group is a second switching number; respectively determining whether the first switching number and the second switching number exceed a predetermined first calibration range; When at least one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality occurs in the active controller and / or the standby controller; The first calibration range is determined by the following steps: simulating the bridge arm switching system to determine the limit value of the double frequency circulating current component in the bridge arm switching system; and determining the first calibration range based on the limit value of the double frequency circulating current component, the rated DC voltage of the converter valve, and the converter valve switching reference value.

2. The method according to claim 1, characterized in that When at least one of the first switching number and the second switching number exceeds the first verification range, determining that an abnormality occurs in the active controller or the standby controller includes: When only one of the first switching number and the second switching number exceeds the first calibration range, determining that an abnormality occurs in the controller corresponding to the switching number exceeding the first calibration range; Determine whether the abnormal controller is being used for control; When the controller having the abnormality is being used for control, a request is made to switch the controller for control.

3. The method according to claim 1, characterized in that Also includes: When both the first switching number and the second switching number exceed the first verification range, obtaining the switching number of each bridge arm included in the second bridge arm group and the switching number of each bridge arm included in the third bridge arm group, wherein the bridge arms included in the second bridge arm group are upper bridge arms and lower bridge arms of the same phase, the bridge arms included in the third bridge arm group are upper bridge arms and lower bridge arms of the same phase, and the bridge arms included in the second bridge arm group, the bridge arms included in the first bridge arm group, and the bridge arms included in the third bridge arm group are of different phases; Correcting the first switching number or the second switching number according to the switching numbers of the bridge arms included in the second bridge arm group and the switching numbers of the bridge arms included in the third bridge arm group; The bridge arms included in the first bridge arm group are controlled to be switched using the corrected switching number.

4. The method according to claim 3, characterized in that The correcting the first switching number or the second switching number according to the switching numbers of the bridge arms included in the second bridge arm group and the switching numbers of the bridge arms included in the third bridge arm group includes: Determining a difference between the switching number of the upper bridge arm and the switching number of the lower bridge arm included in the second bridge arm group according to the switching number of each bridge arm included in the second bridge arm group; Determining the difference between the switching number of the upper bridge arm and the switching number of the lower bridge arm included in the third bridge arm group according to the switching number of each bridge arm included in the third bridge arm group; determining the number of AC components of the second bridge arm group according to a difference between the number of switching on and off of the upper bridge arm and the number of switching on and off of the lower bridge arm included in the second bridge arm group; Determining the number of AC components of the third bridge arm group according to a difference between the number of switching on and off of the upper bridge arm and the number of switching on and off of the lower bridge arm included in the third bridge arm group; Determining the number of AC components of the first bridge arm group according to the number of AC components of the second bridge arm group and the number of AC components of the third bridge arm group; The first switching number or the second switching number is corrected according to the number of AC components of the first bridge arm group.

5. The method according to claim 4, characterized in that The correcting the first switching number or the second switching number according to the number of AC components of the first bridge arm group includes: Determine, from the first switching number or the second switching number, the switching number corresponding to the upper bridge arm included in the first bridge arm group and the switching number corresponding to the lower bridge arm included in the first bridge arm group; Determining whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; When the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal, the switching number corresponding to the upper bridge arm included in the first bridge arm group is corrected according to the number of AC components of the first bridge arm group, the rated DC voltage of the converter valve, and the switching reference value of the converter valve; or, Determining whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal; When the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal, the switching number corresponding to the lower bridge arm included in the first bridge arm group is corrected according to the AC component number of the first bridge arm group, the rated DC voltage of the converter valve and the switching reference value of the converter valve.

6. The method according to claim 5, characterized in that The determining whether the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal includes: determining a second calibration range based on the number of AC components of the first bridge arm group, a predetermined limit value of the doubled frequency circulating current component, the rated DC voltage of the converter valve, and the switching reference value of the converter valve; if the switching number corresponding to the upper bridge arm included in the first bridge arm group exceeds the second calibration range, determining that the switching number corresponding to the upper bridge arm included in the first bridge arm group is abnormal; The determining whether the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal includes: when the switching number corresponding to the upper bridge arm included in the first bridge arm group is within the second verification range, determining that the switching number corresponding to the lower bridge arm included in the first bridge arm group is abnormal.

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