A method for detecting abnormalities in a DC voltage divider

Abstract

The present invention discloses a method for detecting abnormalities in a DC voltage divider, including: obtaining a line current-line resistance relationship table between two adjacent stations; calculating the measured values of the monopole voltage differences of the two adjacent stations respectively; calculating the calculated values of the monopole voltage differences of the two adjacent stations respectively; determining whether the calculated values of the monopole voltage differences of the two adjacent stations are both equal to their respective measured values of the monopole voltage differences; if they are equal, the DC voltage dividers of the two adjacent stations are both normal; if they are not equal, continue to determine whether the difference between the measured values of the monopole voltage differences of the two adjacent stations is equal to the line voltage drop; if they are not equal, the DC voltage divider of the station where the calculated value of the monopole voltage difference is not equal to the measured value of the monopole voltage difference is abnormal; if they are equal, the DC voltage dividers of the two adjacent stations are both normal. This solution can identify whether the DC voltage divider is abnormal, eliminate the drawback that it is difficult to identify whether the DC voltage divider is abnormal at a single station, does not add a new hardware structure and has strong adaptability, effectively avoids the expansion of the measurement deviation of the DC voltage divider, and ensures the safe and stable operation of the DC system.

Description

Technical Field

[0001] The present invention relates to the field of high - voltage direct - current power transmission, and particularly to a method for detecting abnormalities of a DC voltage divider. Background Art

[0002] In current high - voltage direct - current power transmission projects, the connection method of two or more converter stations is often adopted to achieve multi - point power supply and multi - point power reception. A single converter station consists of two poles, and one valve group or two valve groups in series or even multiple valve groups in series form a pole. Its basic control unit is the valve - group control system. The DC voltage controller of the valve - group control system issues commands according to the voltage difference values real - time feedback by the measuring device, and finally reaches the set voltage target value. The voltage difference value is calculated from the difference between the voltage measurement values at the high - voltage DC bus and the neutral line in the converter station. Since there is a grounding point at the neutral bus and the voltage value is close to zero, only by comparing the measurement value at the neutral bus with zero voltage, it is possible to determine whether the DC voltage divider at the neutral bus is abnormal. However, there is no fixed standard value for the voltage at the high - voltage DC bus, and its normal operating range is relatively wide. Therefore, it is difficult to determine whether the DC voltage divider here is abnormal. If the DC voltage divider at the high - voltage DC bus is abnormal, the incorrect voltage difference value obtained by the valve - group control system will directly lead to an incorrect actual voltage value, which may cause the DC system to enter an overload state, increasing the operation risk of the equipment. Seriously, it may lead to unplanned power outages such as tripping, affecting the safe and stable operation of the DC power transmission project.

[0003] For one pole of a single converter station, in the power transmission loop where the entire valve group is in series, at least three DC current measuring devices are installed, and the measured current values are the same current value. Compared with the DC voltage divider, there are more measured values available for determining the abnormality of the measuring device. Just by finding the quantity that is different from the other two among the three DC current measurement values, it is possible to determine the abnormal DC current measuring device. However, at the high - voltage DC bus of each converter station, in most cases, only one DC voltage divider is configured to measure the voltage value, and there are no redundant voltage measurement values to determine the abnormal DC voltage divider. There are also DC voltage calculated values available as judgment conditions, but only through these two quantities, namely the DC voltage calculated value and the high - voltage DC bus measurement value, it is difficult to select the correct voltage value, and thus it is impossible to determine whether the DC voltage divider is abnormal. Summary of the Invention

[0004] In order to determine whether the DC voltage divider is abnormal, the present invention proposes a method for detecting abnormalities of a DC voltage divider, which realizes the determination of the abnormal state of the DC voltage divider by comparing the differences among the calculated DC voltage difference value, the measured DC voltage difference value, and the measured DC voltage difference value between adjacent stations.

[0005] To achieve the above - mentioned purpose, the technical solution of the present invention is:

[0006] A method for detecting abnormalities in a DC voltage divider, comprising:

[0007] Obtain a line current-line resistance relationship table between two adjacent stations;

[0008] Obtain the current monopole high-voltage DC bus voltage, neutral bus voltage of each of the two adjacent stations, and the line current measurement value between the two adjacent stations, and calculate the monopole voltage difference measurement value of each of the two adjacent stations based on this;

[0009] Calculate the calculated value of the monopole voltage difference between the monopole high-voltage DC bus and the neutral bus of each of the two adjacent stations according to the current operating condition;

[0010] Judge whether the calculated values of the monopole voltage differences of the two adjacent stations are both equal to their respective monopole voltage difference measurement values;

[0011] If they are equal, the DC voltage dividers of the two adjacent stations are both normal; if they are not equal, according to the current line current measurement value, query the line current-line resistance relationship table to obtain the corresponding line resistance, calculate the product of the line current measurement value and the line resistance to obtain the line voltage drop, and judge whether the difference between the monopole voltage difference measurement values of the two adjacent stations is equal to the line voltage drop;

[0012] If the difference between the monopole voltage difference measurement values of the two adjacent stations is not equal to the line voltage drop, the DC voltage divider of the station where the calculated value of the monopole voltage difference is not equal to the monopole voltage difference measurement value is abnormal;

[0013] If the difference between the monopole voltage difference measurement values of the two adjacent stations is equal to the line voltage drop, the DC voltage dividers of the two adjacent stations are both normal.

[0014] Preferably, the obtaining of the line current-line resistance relationship table between two adjacent stations includes:

[0015] Set the line current target value between the local station and the adjacent station as the initial minimum value;

[0016] Collect the monopole high-voltage DC bus voltage measurement value, neutral bus voltage measurement value of each of the local station and the adjacent station, and the line current measurement value between the two stations, and calculate the line resistance value at this time and store it in the line current-line resistance relationship table;

[0017] Increase the line current target value between the local station and the adjacent station by a preset current step value in sequence until the rated line current, and calculate the corresponding line resistance value each time the preset current step value is increased and store it in the line current-line resistance relationship table.

[0018] Preferably, the calculation method of the monopole voltage difference measurement value of each of the two adjacent stations is: subtract the neutral bus voltage measurement value from the monopole high-voltage DC bus voltage measurement value of each of the two adjacent stations.

[0019] Preferably, the calculating value of the unipolar voltage difference between the unipolar high-voltage DC busbar and the neutral busbar of each of the two adjacent stations according to the current operating conditions comprises: first calculating the DC voltage of each unipolar converter of the station, and then calculating the sum of the DC voltages of all converters put into operation to obtain the unipolar voltage difference of the station;

[0020] When the station is a conventional sending end, the DC voltage calculation method of each converter is:

[0021]

[0022] Among them, the DC voltage, ideal no-load voltage, trigger angle, commutation reactance, and line current measurement values ​​of the kth converter are U dk , U di0Rk , α k , X tRk ,I L ; 1≤k≤F; F is the total number of single-pole converters;

[0023] When the station is a conventional DC receiving terminal, the DC voltage calculation method of each converter is:

[0024]

[0025] Among them, the DC voltage, ideal no-load voltage, turn-off angle, commutation reactance, and line current measurement values ​​of the kth converter are U dk , U di0Ik , γ k , X tIk ,I L ; 1≤k≤F; F is the total number of single-pole converters;

[0026] When the station is a flexible DC sending or receiving end, the DC voltage calculation method of each converter is:

[0027] U dk =N k *U cavgk

[0028] Among them, the DC voltage of the kth converter, the average voltage of the bridge arm sub-module and the number of sub-modules put into operation in a single bridge arm are U dk , U cavgk and N k ; 1≤k≤F; F is the total number of monopole converters.

[0029] The beneficial effects of the present invention are:

[0030] 1. By calculating the relationship table of line current - line resistance between adjacent stations in advance, the line voltage difference can be accurately calculated at different line currents, and then whether the DC voltage divider is abnormal can be judged, eliminating the drawback that it is difficult to judge whether the DC voltage divider is abnormal at a single station.

[0031] 2. Judging the abnormality of the DC voltage divider according to the currently available voltage information does not add new hardware structure and is more applicable in the engineering field.

[0032] 3. It is applicable to conventional DC, flexible DC and hybrid DC projects, and is also applicable to both two - terminal and multi - terminal DC projects, with strong adaptability.

[0033] 4. It can give an early warning to prompt the operator before the measurement deviation of the DC voltage divider expands, and do a good job in planned maintenance work, effectively avoiding the fault outage event caused by excessive DC voltage deviation, and ensuring the safe and stable operation of the DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flowchart of a method for detecting abnormalities of a DC voltage divider provided by an embodiment of the present invention.

[0035] Figure 2 is a flowchart of a method for obtaining a relationship table of line current - line resistance between two adjacent stations provided by an embodiment of the present invention.

[0036] Figure 3 is a diagram of a three - terminal hybrid DC system provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0038] A method for detecting abnormalities of a DC voltage divider provided by an embodiment of the present invention, as Figure 1 shown, includes the following steps:

[0039] S100: Obtain the relationship table of line current - line resistance between two adjacent stations.

[0040] S200: Obtain the measured values of the monopole high - voltage DC bus voltage, neutral bus voltage of each of the two adjacent stations, and the line current between the two adjacent stations, and calculate the measured values of the monopole voltage difference of each of the two adjacent stations accordingly.

[0041] Among them, the calculation method of the measured value of the monopole voltage difference of each of the two adjacent stations is: the measured value of the monopole high - voltage DC bus voltage of each of the two adjacent stations minus the measured value of the neutral bus voltage.

[0042] S300: Calculate the calculated value of the monopole voltage difference between the monopole high-voltage DC bus and the neutral bus of each of the adjacent two stations according to the current operating condition.

[0043] S400: Determine whether the calculated values of the monopole voltage differences of the adjacent two stations are both equal to their respective measured values of the monopole voltage differences.

[0044] S500: If they are equal, the DC voltage dividers of the adjacent two stations are both normal; if not, according to the measured value of the line current at present, obtain the corresponding line resistance by querying the line current-line resistance relationship table, calculate the product of the measured value of the line current and the line resistance to get the line voltage drop, and determine whether the difference between the measured values of the monopole voltage differences of the adjacent two stations is equal to the line voltage drop.

[0045] S600: If the difference between the measured values of the monopole voltage differences of the adjacent two stations is not equal to the line voltage drop, the DC voltage divider of the station where the calculated value of the monopole voltage difference is not equal to the measured value of the monopole voltage difference is abnormal; if the difference between the measured values of the monopole voltage differences of the adjacent two stations is equal to the line voltage drop, the DC voltage dividers of the adjacent two stations are both normal.

[0046] As Figure 2 shown is a method for obtaining the line current-line resistance relationship table between two adjacent stations provided by an embodiment of the present invention, including the following steps:

[0047] S101: Set the line current target value between the local station and the adjacent station to the initial minimum value.

[0048] S102: Collect the measured values of the monopole high-voltage DC bus voltage and the neutral bus voltage of each of the local station and the adjacent station, as well as the measured value of the line current between the two stations, and calculate the line resistance value at this time and store it in the line current-line resistance relationship table.

[0049] S103: Sequentially increase the line current target value between the local station and the adjacent station by a preset current step value until the rated line current, and calculate the corresponding line resistance value when increasing the preset current step value each time and store it in the line current-line resistance relationship table.

[0050] In a preferred embodiment, calculating the calculated value of the monopole voltage difference between the monopole high-voltage DC bus and the neutral bus of each of the adjacent two stations according to the current operating condition includes: first calculating the DC voltage of each converter of the monopole of this station, and then calculating the sum of the DC voltages of all the converters in operation to obtain the monopole voltage difference of this station;

[0051] When this station is a conventional sending end, the calculation method of the DC voltage of each converter is:

[0052]

[0053] Among them, the DC voltage, ideal no-load voltage, trigger angle, commutation reactance, and line current measurement values of the k-th converter are U dk , U di0Rk , α k , X tRk , I L ; 1 ≤ k ≤ F; F is the total number of converters in a monopole;

[0054] When the station is a receiving end of a conventional HVDC, the calculation method of the DC voltage of each converter is as follows:

[0055]

[0056] Among them, the DC voltage, ideal no-load voltage, extinction angle, commutation reactance, and line current measurement values of the k-th converter are U dk , U di0Ik , γ k , X tIk , I L ; 1 ≤ k ≤ F; F is the total number of converters in a monopole;

[0057] When the station is a sending or receiving end of a flexible HVDC, the calculation method of the DC voltage of each converter is as follows:

[0058] U dk = N k * U cavgk

[0059] Among them, the DC voltage of the k-th converter, the average voltage of the sub-modules inserted in the bridge arm, and the number of sub-modules inserted in a single bridge arm are U dk , U cavgk and N k ; 1 ≤ k ≤ F; F is the total number of converters in a monopole.

[0060] Another DC voltage divider abnormality detection method provided by the embodiments of the present invention includes the following steps:

[0061] Step 1: Set the line current target value between station S m and adjacent station S m+1 to I Lmref and it is the initial minimum value. After the line current stabilizes, go to Step 2.

[0062] Among them, the number of conventional HVDC sending ends is M, the number of conventional HVDC receiving ends is Y, the number of flexible HVDC sending ends is K, the number of flexible HVDC receiving ends is H, the number of single-station single-pole converters is F, M, Y, K, and H are all natural numbers, F is a positive integer, and there is at least one sending end and one receiving end, that is, M + K ≥ 1, Y + H ≥ 1; m is a positive integer and m ≤ M + K + Y + H - 1.

[0063] Step 2: When the measuring device is normal, collect station Sm Unipolar high-voltage DC bus voltage UDL m , neutral bus voltage UDN m ; station S m+1 Unipolar high-voltage DC bus voltage UDL m+1 , neutral bus voltage UDN m+1 ; S m and S m+1 The current I in the line between Lm .

[0064] Step 3: Calculate the line resistance value and store it in the line current-line resistance relationship table R Lm [I Lm .

[0065]

[0066] Step 4: Update the current line current target value to I Lmref +ΔI Lm ; if I Lmref +ΔI Lm ≤I LmN , after the line current stabilizes, go to Step 2; otherwise, go to Step 5;

[0067] where ΔI Lm is the increment of the line current target value, and I LmN is the rated value of the line current.

[0068] Step 5: When the DC system is operating normally, collect the unipolar high-voltage DC bus voltage UDL m of station S m , neutral bus voltage UDN m ; the unipolar high-voltage DC bus voltage UDL m+1 of the adjacent station S m+1 , neutral bus voltage UDN m+1 ; the current I m in the line between S m+1 and S Lm .

[0069] Step 6: Calculate the DC voltages of the unipolar converters of S m and S m+1 according to the current operating conditions.

[0070] When this station is a conventional sending end, the calculation method of the DC voltage of each converter is:

[0071]

[0072] where the ideal no-load voltage, trigger angle, and commutation reactance of the kth converter at the conventional DC sending end are U di0Rk , αk , X tRk ; 1 ≤ k ≤ F;

[0073] When the station is a conventional DC receiving end, the calculation method of the DC voltage of each converter is as follows:

[0074]

[0075] Among them, the ideal no-load voltage, extinction angle, and commutation reactance of the kth converter at the conventional DC receiving end are U di0Ik , γ k , X tIk ; 1 ≤ k ≤ F;

[0076] When the station is a flexible DC sending end or receiving end, the calculation method of the DC voltage of each converter is as follows:

[0077] U dmk = N k * U cavgk

[0078] Among them, the average voltage of the sub-modules inserted in the bridge arm of the kth converter at the flexible DC sending end or receiving end and the number of sub-modules inserted in a single bridge arm are U cavgk and N k ; 1 ≤ k ≤ F.

[0079] Step 7: Calculate S m and S m+1 respectively, which are the sums of the DC voltages of all the converters in operation, to obtain the single-pole voltage differences UD m and UD m+1 between the single-pole high-voltage DC bus and the neutral bus of S m and UD m+1 ;

[0080] UD m = OPN m1 * U dm1 + OPN m2 * U dm2 + … + OPN mk * U dmk ;

[0081] UD m+1 = OPN (m+1)1 * U d(m+1)1 + OPN (m+1)2 * U d(m+1)2 + … + OPN (m+1)k * U d(m+1)k ;

[0082] Among them, OPN mk is the operating state of the kth converter of station S m , and when it is in operation, OPNmk = 1, exit OPN during runtime mk = 0; 1 ≤ k ≤ F.

[0083] Step 8, compare the calculated value and the measured value of the monopole voltage difference; if UD m = UDL m - UDN m and UD m+1 = UDL m+1 - UDN m+1 , then the DC voltage dividers of station S m and station S m+1 are both normal; if the calculated value and the measured value of at least one station are not equal, then according to the current line current measurement value, obtain the corresponding line resistance by querying the line current - line resistance relationship table, calculate the product of the line current measurement value and the line resistance to get the line voltage drop, and determine whether the difference between the monopole voltage difference measurement values of adjacent two stations is equal to the line voltage drop;

[0084] If UD m ≠ UDL m - UDN m and UD m+1 = UDL m+1 - UDN m+1 , |I Lm R Lm [I Lm | ≠ |(UDL m - UDN m ) - (UDL m+1 - UDN m+1 )|, then the DC voltage divider of station S m is abnormal, and the DC voltage divider of station S m+1 is normal;

[0085] If UD m = UDL m - UDN m and UD m+1 ≠ UDL m+1 - UDN m+1 , |I Lm R Lm [I Lm | ≠ |(UDL m - UDN m ) - (UDL m+1 - UDN m+1 )|, then the DC voltage divider of station S m is normal, and the DC voltage divider of station S m+1 is abnormal;

[0086] If UD m ≠ UDL m - UDNm and UD m+1 = UDL m+1 - UDN m+1 , |I Lm R Lm [I Lm | = |(UDL m - UDN m ) - (UDL m+1 - UDN m+1 ), then the station S m and the station S m+1 DC voltage dividers are normal, and the calculated value UD of the station S m is abnormal; m

[0087] If UD m = UDL m - UDN m and UD m+1 ≠ UDL m+1 - UDN m+1 , |I Lm R Lm [I Lm | = |(UDL m - UDN m ) - (UDL m+1 - UDN m+1 ), then the station S m and the station S m+1 DC voltage dividers are normal, and the calculated value UD of the station S m+1 is abnormal. m+1

[0088] As Figure 3 shown, a three-terminal hybrid DC system provided by an embodiment of the present invention, wherein the number of conventional DC sending ends is 1, the number of conventional DC receiving ends is 0, the number of flexible DC sending ends is 0, the number of flexible DC receiving ends is 2, the number of single-station single-pole converters is 2, and the three stations are the conventional DC sending end station S1, the flexible DC receiving end station S2, and the flexible DC receiving end station S3; taking m = 1 and the abnormal detection of the DC voltage dividers of the station S1 and the adjacent station S2 as an example.

[0089] Taking Figure 3 the system as an example, the abnormal detection method of the DC voltage divider is specifically described, including the following steps:

[0090] Step 11. Set the target value of the line current between the station S1 and the adjacent station S2 to I L1ref and it is the initial minimum value. After the line current is stable, go to step 12.

[0091] ​​Step 12: When the measuring device is normal, collect the monopole high-voltage DC bus voltage UDL1 and neutral bus voltage UDN1 of collection station S1; the monopole high-voltage DC bus voltage UDL2 and neutral bus voltage UDN2 of station S2; and the current I of the line between S1 and S2 L1 . Step 13: Calculate the line resistance value and store it in the line current-line resistance relation table R L1 [I L1 :

[0092]

[0093] Step 14: Update the current line current target value to I L1ref +ΔI L1 ; If I L1ref +ΔI L1 ≤I L1N , after the line current stabilizes, go to Step 12; otherwise, go to Step 15;

[0094] where, ΔI L1 is the increment of the line current target value, and I L1N is the rated value of the line current.

[0095] Step 15: When the DC system is operating normally, collect the monopole high-voltage DC bus voltage UDL1 and neutral bus voltage UDN1 of collection station S1; the monopole high-voltage DC bus voltage UDL2 and neutral bus voltage UDN2 of adjacent station S2; and the current I of the line between S1 and S2 L1 .

[0096] Step 16: Calculate the DC voltages of each converter of the monopole of S1 and S2 according to the current operating conditions. S1 is the sending end of the conventional DC, and the calculation method is:

[0097]

[0098]

[0099] where, the ideal no-load voltage, trigger angle, and commutation reactance of the first converter at the sending end of the conventional DC are U di0R1 , α1, X tR1 ; the ideal no-load voltage, trigger angle, and commutation reactance of the second converter at the sending end of the conventional DC are U di0R2 , α2, X tR2 ;

[0100] S2 is the receiving end of the flexible DC, and the calculation method is:

[0101] U d21 =N1*U cavg1

[0102] Ud22 = N2 * U cavg2

[0103] Wherein, the average voltage of the switched sub-modules of the first converter arm at the flexible DC receiving end and the number of switched sub-modules of a single arm are U cavg1 and N1 respectively; the average voltage of the switched sub-modules of the second converter arm at the flexible DC receiving end and the number of switched sub-modules of a single arm are U cavg2 and N2 respectively.

[0104] Step 17: Obtain the calculated values UD1 and UD2 of the monopole voltage differences of station S1 and station S2;

[0105] UD1 = OPN 11 * U d11 + OPN 12 * U d12 ;

[0106] UD2 = OPN 21 * U d21 + OPN 22 * U d22 ;

[0107] Assume that the number of operating converters for single-pole operation of a single station is 2, then OPN 11 = OPN 12 = OPN 21 = OPN 22 = 1;

[0108]

[0109] UD2 = N1 * U cavg1 + N2 * U cavg2

[0110] Step 18: Compare the calculated values and measured values of the monopole voltage differences. If UD1 = UDL1 - UDN1 and UD2 = UDL2 - UDN2, then the DC voltage dividers of station S1 and station S2 are both normal; otherwise, go to Step 19.

[0111] Step 19: According to the measured value of the current of the current line, obtain the corresponding line resistance by querying the line current - line resistance relationship table, calculate the product of the measured value of the line current and the line resistance to obtain the line voltage drop, and determine whether the difference between the measured values of the monopole voltage differences of two adjacent stations is equal to the line voltage drop;

[0112] If UD1 ≠ UDL1 - UDN1 and UD2 = UDL2 - UDN2, |I L1 R L1 [I L1If |I]|≠|(UDL1 - UDN1)-(UDL2 - UDN2)|, then the DC voltage divider of station S1 is abnormal and the DC voltage divider of station S2 is normal;

[0113] If UD1 = UDL1 - UDN1 and UD2 ≠ UDL2 - UDN2, |I L1 R L1 [I L1 |≠|(UDL1 - UDN1)-(UDL2 - UDN2)|, then the DC voltage divider of station S1 is normal and the DC voltage divider of station S2 is abnormal;

[0114] If UD1 ≠ UDL1 - UDN1 and UD2 = UDL2 - UDN2, |I L1 R L1 [I L1 |=|(UDL1 - UDN1)-(UDL2 - UDN2)|, then the DC voltage dividers of both station S1 and station S2 are normal, and the calculated value UD1 of station S1 is abnormal;

[0115] If UD1 = UDL1 - UDN1 and UD2 ≠ UDL2 - UDN2, |I L1 R L1 [I L1 |=|(UDL1 - UDN1)-(UDL2 - UDN2)|, then the DC voltage dividers of both station S1 and station S2 are normal, and the calculated value UD2 of station S2 is abnormal.

[0116] The above detailed description is for a specific embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention shall be included in the patent scope of this case.

Claims

1. A method for detecting abnormalities in a DC voltage divider, characterized in that, Including: Obtain the line current-line resistance relationship table between two adjacent stations; Obtain the current monopole high-voltage DC bus voltage, neutral bus voltage of each of the two adjacent stations, and the line current measurement value between the two adjacent stations, and calculate the monopole voltage difference measurement value of each of the two adjacent stations based on this; Calculate the monopole voltage difference calculation value between the monopole high-voltage DC bus and the neutral bus of each of the two adjacent stations according to the current operating condition; Judge whether the monopole voltage difference calculation values of the two adjacent stations are both equal to their respective monopole voltage difference measurement values; If they are equal, the DC voltage dividers of the two adjacent stations are both normal; If they are not equal, according to the current line current measurement value, obtain the corresponding line resistance by querying the line current-line resistance relationship table, calculate the product of the line current measurement value and the line resistance to get the line voltage drop, and judge whether the difference between the monopole voltage difference measurement values of the two adjacent stations is equal to the line voltage drop; If the difference between the monopole voltage difference measurement values of the two adjacent stations and the line voltage drop are not equal, the DC voltage divider of the station where the monopole voltage difference calculation value is not equal to the monopole voltage difference measurement value is abnormal; If the difference between the monopole voltage difference measurement values of the two adjacent stations and the line voltage drop are equal, the DC voltage dividers of the two adjacent stations are both normal; The calculating the monopole voltage difference calculation value between the monopole high-voltage DC bus and the neutral bus of each of the two adjacent stations according to the current operating condition includes: first calculating the DC voltage of each converter in the monopole of the station, and then calculating the sum of the DC voltages of all the converters in operation to obtain the monopole voltage difference of the station; When the station is a conventional sending end, the calculation method of the DC voltage of each converter is: Among them, the measured values of the DC voltage, ideal no-load voltage, firing angle, commutation reactance, and line current of the k-th converter are U dk , U di0Rk , α k , X tRk , I L ; 1 ≤ k ≤ F; F is the total number of converters in a monopole; When the station is a conventional DC receiving end, the calculation method of the DC voltage of each converter is: Among them, the measured values of the DC voltage, ideal no-load voltage, extinction angle, commutation reactance, and line current of the k-th converter are U dk , U di0Ik , γ k , X tIk , I L ; 1 ≤ k ≤ F; F is the total number of converters in a monopole; When the station is a flexible DC sending end or receiving end, the calculation method of the DC voltage of each converter is: U dk = N k * U cavgk Among them, the DC voltage of the k-th converter, the average voltage of the switching sub-modules in the bridge arm, and the number of switching sub-modules in a single bridge arm are U dk , U cavgk , and N k ; 1 ≤ k ≤ F; F is the total number of converters in a single pole.

2. The abnormal detection method of a DC voltage divider according to claim 1, wherein The obtaining the line current-line resistance relationship table between two adjacent stations includes: Set the line current target value between the local station and the adjacent station as the initial minimum value; Collect the monopole high-voltage DC bus voltage measurement value, neutral bus voltage measurement value of each of the local station and the adjacent station, and the line current measurement value between the two stations, and calculate the line resistance value at this time and store it in the line current-line resistance relationship table; Successively increase the line current target value between the local station and the adjacent station by a preset current step value until the rated line current, and calculate the corresponding line resistance value when increasing the preset current step value each time and store it in the line current-line resistance relationship table.

3. The abnormal detection method of a DC divider according to claim 1, wherein The calculation method of the monopole voltage difference measurement value of each of the two adjacent stations is: subtract the neutral bus voltage measurement value from the monopole high-voltage DC bus voltage measurement value of each of the two adjacent stations.

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