Multi-terminal hvdc project main circuit parameter calculation method and system

Abstract

The application relates to a multi-terminal mixed connection extra-high voltage direct current engineering main loop parameter calculation method and system, which comprises the following steps: on the basis of a network equation of traditional port direct current voltage and direct current, a multi-terminal direct current system network matrix related to valve group port voltage and direct current of each mixed connection converter station in different operation conditions is obtained through matrix transformation; an N-order matrix normalization method is adopted, the multi-terminal direct current system network matrix is solved according to different control modes and in combination with a Newton-Raphson method, direct current parameters under the multi-control mode are obtained; based on the direct current parameters, the position of a converter transformer tap is solved by given triggering and turn-off angles, and converter parameters are calculated. The main loop parameter calculation speed is relatively fast, and the calculation result is high in accuracy.

Description

Technical Field

[0001] This invention relates to the field of DC transmission system technology, and in particular to a method and system for calculating the main circuit parameters of a multi-terminal hybrid ultra-high voltage DC project. Background Technology

[0002] Compared with traditional two-terminal DC projects, cascaded multi-terminal high-voltage DC transmission can transmit power more flexibly and economically. For example, it can transmit power from multiple power bases through DC transmission technology, or connect to power sources or loads through intermediate branches, or supply power from a power base to multiple load areas. This method can achieve reasonable and optimized allocation of power resources.

[0003] There has been some research on the calculation methods for the main circuit parameters of multi-terminal parallel UHVDC transmission lines. Multi-terminal parallel connection refers to the connection method of multiple converter stations with the same voltage level connected in parallel. However, there is relatively little research on the parameters of multi-terminal main circuits with hybrid structures where multiple terminals are simultaneously connected in series and parallel. Because converter stations are connected in both parallel and series configurations, there is both DC voltage coupling and DC current coupling between stations, making the calculation methods more complex. The calculation of main circuit parameters is fundamental in the design of DC transmission projects. The results of the main circuit parameters serve as input for the design of AC / DC filters in DC transmission projects, and the accuracy and speed of the calculation are crucial. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a method and system for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project, which has a fast calculation speed and high accuracy.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project, comprising: based on the traditional network equations of port DC voltage and DC current, obtaining the multi-terminal DC system network matrix related to the valve group port voltage and DC current of each hybrid converter station under different operating conditions through matrix transformation; using the N-order matrix normalization method, solving the multi-terminal DC system network matrix according to different control modes and combined with the Newton-Raphson method to obtain the DC parameters under multiple control modes; based on the DC parameters, determining the converter transformer tap position by giving the trigger and turn-off angles, and calculating the converter parameters.

[0006] Furthermore, the converter parameters are calculated, including:

[0007] Under rated conditions, the converter tap position is determined by giving the firing angle and the turn-off angle;

[0008] For other power levels, adjust the converter tap positions so that the parameters of each converter meet the first constraint condition, and calculate the corresponding converter power parameters; wherein, each parameter includes firing angle and turn-off angle, tap limit and DC voltage limit.

[0009] Furthermore, the converter tap position is determined by giving the firing angle and the turn-off angle, including:

[0010] Given the firing angle and the turn-off angle, determine whether P and Q satisfy the set second constraint condition. If they do, calculate the ideal no-load DC voltage U of the converter based on the DC parameters of the multi-terminal DC system and the control mode of the DC system. di0 The range of the taps is determined; if the range is not met, the DC parameters must be recalculated.

[0011] Furthermore, the second constraint is: P cmin ≤P≤P cmax and Q acmin ≤Q≤Q acmax ;

[0012] If P and Q do not exceed the limits, then the first constraint condition is satisfied.

[0013] Furthermore, adjust the position of the converter taps, including:

[0014] Adjust the tap changers to meet the first constraint condition without changing the control mode and command value of each converter.

[0015] If the tap changer reaches the adjustment limit specified by the first constraint condition, the control mode or command value of some converter stations will be changed. If the first constraint condition is not met, the DC parameters will be recalculated.

[0016] Furthermore, the first constraint is:

[0017] Triggering and shut-off angles of the converter station: α min ≤α≤α max γ min ≤γ≤γ max ;

[0018] Tape limit: n Tcmin ≤n T ≤n Tmax ;

[0019] DC voltage limit: U dmin ≤U d ≤U dmax .

[0020] Furthermore, if the first constraint condition is not met, the DC parameters are recalculated, including:

[0021] After calculating the DC parameters, the original ideal no-load voltage U di0Ri Based on this, the new trigger angle α and turn-off angle γ are determined;

[0022] When the trigger angle α < α min At that time, if the ideal no-load DC voltage U of the converter di0 Since the minimum limit value has not yet been reached, let α = α directly. min Calculate the ideal no-load DC voltage U of the converter. di0 If the ideal no-load DC voltage U of the converter di0 When the limit value is reached, α = α min Then, return to the DC parameter section for calculation and recalculate the parameters of each converter.

[0023] A multi-terminal hybrid UHVDC main circuit parameter calculation system includes: a DC network matrix acquisition module, which, based on the traditional network equations of port DC voltage and DC current, obtains the multi-terminal DC system network matrix related to the valve group port voltage and DC current of each hybrid converter station under different operating conditions through matrix transformation; a DC parameter calculation module, which uses an N-order matrix normalization method to solve the multi-terminal DC system network matrix according to different control modes and combined with the Newton-Raphson method to obtain the DC parameters under multiple control modes; and a converter parameter calculation module, which, based on the DC parameters, determines the position of the converter transformer tap changer by giving the trigger and turn-off angles and calculates the converter parameters.

[0024] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0025] A computing device includes: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0026] The present invention has the following advantages due to the adoption of the above technical solutions: The present invention adopts the method of N-order matrix normalization, and solves the DC network matrix by combining the Newton-Raphson method according to different control modes, and solves the DC parameters under multiple control modes, which greatly reduces the number of iterations and improves the calculation speed. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project provided by an embodiment of the present invention;

[0028] Figure 2This is an n-terminal DC transmission system provided in the embodiments of the present invention;

[0029] Figure 3 This is a 2n-terminal hybrid DC transmission system provided in an embodiment of the present invention;

[0030] Figure 4 This is the steady-state parameter calculation process for an n-terminal DC transmission system provided in this embodiment of the invention;

[0031] Figure 5 This is a schematic diagram of a three-terminal DC power transmission project structure provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] In one embodiment of the present invention, a method for calculating the main circuit parameters of a multi-terminal hybrid ultra-high voltage direct current (UHVDC) project is provided, for use in cascaded converter stations of cascaded multi-terminal UHVDC transmission, and for cascaded multi-terminal UHVDC transmission systems constructed using cascaded converter stations. In this embodiment, as shown... Figure 1 As shown, the method includes the following steps:

[0035] 1) Based on the traditional network equations for DC voltage and DC current at the ports, the multi-terminal DC system network matrix related to the valve group port voltage and DC current of each hybrid converter station under different operating conditions is obtained by matrix transformation.

[0036] 2) Using the N-order matrix normalization method, the network matrix of the multi-terminal DC system is solved according to different control modes and combined with the Newton-Raphson method to obtain the DC parameters under multiple control modes;

[0037] 3) Based on the DC parameters, the position of the converter transformer tap is determined by giving the trigger and turn-off angles, and the converter parameters are calculated.

[0038] In practice, this invention employs an N-order matrix normalization method, forming separate matrices for the independent and dependent variables according to different control methods. It then combines the Newton-Raphson method to solve the DC network matrix, thereby solving for DC parameters under multiple control methods. This significantly reduces the number of iterations and improves the calculation speed.

[0039] In step 1) above, the network equation construction is specifically as follows:

[0040] We define the positive direction of current flow as from the AC subsystem to the DC subsystem. Thus, the rectifier current is positive, the inverter current is negative, and both the rectifier and inverter voltages are positive. This allows us to obtain the DC transmission system network equations expressed in terms of current:

[0041] I d =G d V d (1)

[0042] In the formula, I d V d These are the current vector and voltage vector of the DC transmission system, respectively; G d It is the nodal admittance matrix of a DC power transmission system.

[0043] Considering the control characteristics of the DC transmission system, by substituting the control equations of the converter, the power flow equations of the DC transmission system can be obtained.

[0044] (1) The DC system adopts a constant current control method:

[0045]

[0046] (2) The DC system adopts a constant voltage control method:

[0047]

[0048] (3) The DC system adopts a constant power control method.

[0049]

[0050] Where CV represents constant current control, G ij U represents the admittance matrix. di Indicates DC voltage. This represents direct current, with the superscript 'con' indicating a constant, and I... di This indicates that the DC voltage contains variables. This represents DC voltage; the superscript "con" indicates a constant; P con This indicates DC power, and the superscript "con" indicates a constant.

[0051] In this embodiment, the establishment of the multi-terminal DC system network matrix is ​​specifically as follows:

[0052] DC transmission operation modes mainly include bipolar, monopolar, and metallic loop modes. Since the metallic loop mode is only equivalent to R on a DC line... di Series resistor R m Therefore, the analysis will only focus on the bipolar operation mode.

[0053] like Figure 2 As shown, taking an n-terminal DC transmission system as an example, its admittance matrix is ​​derived using the nodal voltage method. Where U dnH U dnL They are respectively Figure 2 The outlet voltage vectors of each converter valve group at the positive and negative terminals; I dnH I dnL They are respectively Figure 2 The outlet current vectors of the positive and negative converter valve groups; U dn U dn 'R' represents the voltage of each positive and negative converter valve group; dn R is the DC resistance on a DC line. m R is the DC resistance of the metal circuit. en R en 'These are the resistances at the positive and negative neutral points, respectively, U en This is the neutral point voltage.

[0054] The network equation is:

[0055]

[0056] Supplementary equation:

[0057]

[0058] The DC network matrix is ​​as follows:

[0059]

[0060] make

[0061] AU dn =I dn

[0062]

[0063] Right now:

[0064]

[0065]

[0066]

[0067] Continue to simplify:

[0068]

[0069] Let matrix

[0070]

[0071] C = {1 - AB} -1 A (11)

[0072] The network matrix shown in equation (10) is applicable to multi-terminal DC transmission systems under operating conditions. When the DC operating conditions change, the resistance values ​​in matrices A and B will change. 1) Under monopolar operation, the resistance value in matrix B is R en / / R en 'Change to R en ;2) In unipolar metal operation mode, the resistance value in array A is changed by R di Change to R di +R m However, this network only contains parallel connections. When the network also contains series structures, the admittance matrix cannot contain all the information, so the network matrix is ​​further expanded.

[0073] like Figure 3 As shown, when a set of converter valves is connected in series between 1 and 2, both converter valves receive the same current. Since the two sets of converter valves connected in series have a total of three variables: series current I... d1 and voltage node U d1 Series valve group voltage U d12 The two converter valves connected in series are controlled by constant voltage, constant current, or constant power. Since both sets cannot be controlled by constant current, the possible control combinations are: constant current and constant voltage; constant current and constant power; constant voltage and constant power; constant power and constant power. Regardless of the method, there is only one actual variable. The matrix in this case is a mixed matrix.

[0074]

[0075] in

[0076]

[0077] Further separation of the matrix yields general equations (13) and (14) for the hybrid structure. Where I d1H and I d1L These correspond to the currents flowing through the series-connected valve group at the positive and negative terminals, respectively. When there is no series-connected valve group in the network, then I... d1H and I d1L All are 0, and the range of n starts from 1.

[0078]

[0079]

[0080] In summary, both fully parallel DC transmission systems and hybrid DC transmission systems can be represented by equation (12). Expanding equation (12) yields equations (13) and (14). Equation (13) corresponds to the matrix equation of an n-terminal fully parallel DC transmission system, while the combined equations (13) and (14) correspond to the matrix equation of an n-terminal hybrid DC transmission system.

[0081] In step 2) above, the solution for the multi-terminal DC system network matrix is ​​as follows:

[0082] Considering the control equations (2), (3), and (4), the different control methods in matrix C are classified and divided into blocks, and the simplified equations are shown in equation (15):

[0083]

[0084] 2.1) If one of the two converter valves connected in series is controlled by constant current, then equation (13) only adds a constant term to equation (10), and the voltage and current values ​​of each converter valve can be solved directly using the Newton-Raphson method. Finally, the DC voltage of the other converter valve (constant current + constant power, same as above) is calculated according to equation (14).

[0085] 2.2) with Figure 3 For example, when both are constant voltages, then:

[0086]

[0087]

[0088] Substituting equation (19) into equation (18), we obtain equation (20).

[0089]

[0090] Equation (20) is equivalent to adding a constant term to equation (10). Similarly, according to the control method, the matrix is ​​simplified to equation (15), and then the DC voltage and current of each converter valve group are obtained using the Newton-Raphson method. Finally, based on the obtained DC voltage and current, they are substituted into equation (16) to obtain the DC voltage and current of the series valve group.

[0091] 2.3) If one or both of the two converter valves connected in series are controlled by constant power, the equations will be nonlinear equations. In this case, two Newton-Raphson iteration methods are required.

[0092] Constant voltage and constant power control are used respectively.

[0093]

[0094] Because of P d12 / U d12 =I d ,therefore:

[0095]

[0096]

[0097]

[0098] Based on the given DC voltage U dn Equation (20) uses Newton-Raphson's method to obtain I. d1H Then equation (20) uses the known DC current I d1H Given initial values, the DC voltage and DC current are obtained through iterative calculation.

[0099] Constant power control is used in all cases.

[0100]

[0101]

[0102] Based on the given DC voltage U dn Equation (21) uses Newton-Raphson's method to obtain I. d1H Then, equation (22) uses the known DC current I d1H Given initial values, the DC voltage and DC current are obtained through iterative calculation.

[0103] In summary, for multi-terminal hybrid circuits, the network matrix can be listed according to the network structure, and the DC voltage and DC current can be solved using the Newton-Raphson method based on the control method.

[0104] In step 3) above, the formulas for calculating the converter parameters are as follows:

[0105] 1) Calculate the rated ideal no-load DC voltage U of the converter station. di0N :

[0106] For rectifier station i (i = 1, 2, ...):

[0107]

[0108] For inverter station i (i = 1, 2, ...):

[0109]

[0110] In the above formula, n is the number of 12-pulse valve groups, U di0NRi U is the rated ideal control voltage on the rectifier side of the i-th converter station.dNRi U is the rated DC voltage of the i-th converter station. T For the forward conduction voltage drop of the converter station, α Ni Let d be the firing angle of the i-th converter station. xNRi Let d be the converter transformer reactance of the i-th converter station. rNRi Let U be the converter transformer resistance of the i-th converter station. di0NIi γ is the rated ideal control voltage on the inverter side of the i-th converter station. Ni Let be the rated shut-off angle of the i-th converter station.

[0111] 2) In actual engineering projects, given the firing angle / turn-off angle, the ideal no-load DC voltage U of the converter station is calculated. di0 :

[0112] For rectifier station i (i = 1, 2, ...):

[0113] U di0Ri =[U dRi / (2n)+U T +U di0NRi I dRi ·(d xRi +d rRi ) / I dNRi ] / cosα (25)

[0114] For inverter station i (i = 1, 2):

[0115] U di0Ii =[U dIi / (2n)-U T +U di0NIi I dIi ·(d xIi -d rIi ) / I dNIi ] / cosγ (26)

[0116] 3) Calculate the commutation angle μ:

[0117] For rectifier station i (i = 1, 2, ...):

[0118]

[0119] For inverter station i (i = 1, 2, ...):

[0120]

[0121] 4) Calculate the reactive power compensation Q, AC side active power P, and converter station capacity:

[0122] For rectifier station i (i = 1, 2, ...):

[0123]

[0124] For inverter station i (i = 1, 2, ...):

[0125]

[0126] For rectifier station i (i = 1, 2, ...):

[0127]

[0128] For inverter station i (i = 1, 2, ...):

[0129]

[0130] 5) Based on the calculated ideal no-load DC voltage U dio The range, and determine the converter station tap position n T :

[0131]

[0132] Where, n T U represents the tap position, Δη represents the tap adjustment step size, and U represents the tap position. ac For AC side voltage, U acN This is the rated voltage on the AC side.

[0133] The steady-state operating range of multi-terminal DC transmission systems is often limited by factors such as the range of changes in the firing angle and turn-off angle, and the range of changes in the tap changers of converter transformers. These constraints together constitute the operating range of the multi-terminal system. Adjusting some operating parameters is necessary to prevent the multi-terminal system from exceeding its operating boundaries. Therefore, in calculating the operating parameters of multi-terminal DC transmission systems, it is necessary to consider the boundary limitations imposed by the operating constraints on the calculation process. Often, it is necessary to determine whether the calculation results are within the limits during the calculation process; if they exceed the limits, intermediate results need to be modified and recalculated. Compared to two-terminal DC transmission systems, the increased number of terminals leads to more constraints that need to be considered during calculation. Therefore, in practical engineering, first and second constraints need to be provided to limit the range of parameters.

[0134] In this embodiment, as Figure 4 As shown, calculating the converter parameters includes the following steps:

[0135] 3.1) Under rated conditions, determine the converter tap position by giving the firing angle and the turn-off angle;

[0136] 3.2) For other power levels, adjust the converter tap positions so that the parameters of each converter meet the first constraint condition, and calculate the corresponding converter power parameters; wherein, each parameter includes firing angle and shut-off angle, tap limit and DC voltage limit.

[0137] In step 3.1) above, the converter tap position is determined by giving the firing angle and the turn-off angle, specifically as follows:

[0138] Given the firing angle and the turn-off angle, determine whether P and Q satisfy the set second constraint condition. If they do, calculate the ideal no-load DC voltage U of the converter based on the DC parameters of the multi-terminal DC system and the control mode of the DC system. di0 The range of the taps is determined; if the range is not met, the DC parameters must be recalculated.

[0139] In this embodiment, the second constraint is: If P and Q do not exceed the limits, then the first constraint condition is satisfied. cmin To minimize the active power delivered by the converter, Q is the maximum active power delivered by the converter. acmin To minimize reactive power consumption at the converter station This represents the maximum reactive power consumption of the converter station.

[0140] In this embodiment, if the conditions are not met, and the DC parameters need to be recalculated, the solution result discards the control commands of some stations. For constant DC power stations and constant DC current stations, it is allowed to discard their original current values; while for constant voltage stations, when the limits are exceeded, it is allowed to discard the original constant voltage.

[0141] In step 3.2) above, adjusting the converter tap position includes the following steps:

[0142] 3.2.1) Adjust the tap changers to meet the first constraint condition without changing the control mode and command value of each converter;

[0143] 3.2.2) If the tap changer reaches the adjustment limit specified by the first constraint condition, the control mode or command value of some converter stations shall be changed. If the first constraint condition is not met, the DC parameters shall be recalculated.

[0144] Taking the rectifier station as an example, equations (25), (27), and (29) need to be solved simultaneously. Since these are all nonlinear equations, the control method of the DC system needs to be considered.

[0145] Constant voltage control: The unknown quantity at this time is U dRi μ, α / γ, keep U di0Ri I dRi The voltage reference value U remains unchanged; it can be obtained by solving the equations simultaneously. dRiThen, return to the DC parameter calculation section to recalculate the DC parameters for each converter station.

[0146] Constant current control: The unknown quantity is I. dRi μ, α / γ, keep U di0Ri U dRi The current reference value I remains unchanged; it can be obtained by solving the equations simultaneously. dRi Then, return to the DC parameter calculation section to recalculate the DC parameters for each converter station.

[0147] Constant power control: This method uses the same processing method as constant current control, letting U... di0Ri U dRi The current reference value I remains unchanged; it can be obtained by solving the equations simultaneously. dRi Then the new P dR equal to U dR with I dR Multiply. Return to the DC parameter calculation section to recalculate the DC parameters for each converter station.

[0148] In this embodiment, the first constraint is:

[0149] Triggering and shut-off angles of the converter station: α min ≤α≤α max γ min ≤γ≤γ max ;

[0150] Tape limit: n Tcmin ≤n T ≤n Tmax ;

[0151] DC voltage limit: U dmin ≤U d ≤U dmax .

[0152] In step 3.2.2) above, if the first constraint condition is not met, the DC parameters are recalculated, including the following steps:

[0153] 3.2.2.1) After calculating the DC parameters, in the original U di0Ri Based on the no-load DC voltage of the i-th converter station, the new firing angle α and the turn-off angle γ are obtained; then the converter parameters of other converter stations are calculated according to formulas (27)-(32).

[0154] 3.2.2.2) When the triggering angle α < α min At that time, if the ideal no-load DC voltage U of the converter di0 Since the minimum limit value has not yet been reached, let α = α directly. min Calculate the ideal no-load DC voltage U of the converter. di0 If the ideal no-load DC voltage U of the converterdi0 When the limit value is reached, α = α min Then, return to the DC parameter section for calculation and recalculate the parameters of each converter.

[0155] When calculating the converter parameters for each converter station at other power levels, the firing angle α and the turn-off angle γ are given again to calculate U. di0Ri Then determine n T When the conditions exceed the limit, first let U di0Ri Keeping the parameters unchanged, recalculate the DC parameter calculation section using the constraints, correct the DC parameters, and recalculate the firing angle α / turn-off angle γ. If α < α min In the case of [the situation], the calculation shall be performed according to the calculation process in step 3.2.2.2).

[0156] Example: Taking a domestic ±800kV project as an example, a three-terminal DC transmission project is constructed, including two rectifier stations, where station 1 and station 2 are cascaded and station 1 and station 3 are parallel. One inverter station is also included. Figure 5 As shown. The rectifier stations are connected in series. The system rated voltage is 800kV, the single-pole transmission power is 4000MW, the rated firing angle and rated shutdown angle are 15°, 15°, and 19.5° respectively, the firing angle range is [12.5°, 17.5°], the shutdown angle range is [17.5°, 19.5°], the minimum firing angle is 5°, and the minimum shutdown angle is 12°. This paper will calculate the main circuit parameters of each station under different control modes. The DC resistance between station 1 and station 2 is 0.5 ohms, and the DC resistance between station 1 and station 3 is 7Ω.

[0157] Let converter stations 1 and 2 be controlled by constant current and converter station 3 be controlled by constant voltage. Then, calculate the main circuit parameters of each converter station under the bipolar full-voltage operation mode when the power of each converter station increases synchronously from 0.1 pu to 1.0 pu. The results of DC power, DC voltage, DC current, no-load DC voltage, firing angle / shutdown angle, commutation angle, active power consumed by the converter, reactive power consumed by the converter, and converter transformer tap position of each converter station are shown in Tables 1 to 3 below.

[0158] Table 1 Operating characteristics of the DC system at converter station 1

[0159] <![CDATA[P d ]]> <![CDATA[U d ]]> <![CDATA[I d ]]> <![CDATA[U di0 ]]> angle u nT(i) 400 400 0.50 223.55 24.91 2.69 3.1 800 400 1.00 224.08 23.69 5.39 3.1 1200 400 1.50 224.08 22.07 8.14 3.1 1600 400 2.00 224.08 20.34 10.96 3.1 2000 400 2.50 224.08 18.45 13.89 3.1 2400 400 3.00 224.08 16.35 16.97 3.1 2800 400 3.50 224.08 13.95 20.29 3.1 3200 400 4.00 226.81 14.15 21.96 2.1 3600 400 4.50 229.61 14.41 23.47 1.1 4000 400 5.00 232.77 15.00 24.66 0 4400 400 5.58 232.77 14.93 26.63 0 4800 400 6.17 232.77 14.86 28.59 0

[0160] Table 2 Operating Characteristics of DC System at Converter Station 2

[0161] <![CDATA[P d ]]> <![CDATA[U d ]]> <![CDATA[I d ]]> <![CDATA[U di0 ]]> angle u nT(i) 400 400 0.50 223.55 24.91 2.69 3.1 800 400 1.00 224.08 23.69 5.39 3.1 1200 400 1.50 224.08 22.07 8.14 3.1 1600 400 2.00 224.08 20.34 10.96 3.1 2000 400 2.50 224.08 18.45 13.89 3.1 2400 400 3.00 224.08 16.35 16.97 3.1 2800 400 3.50 224.08 13.95 20.29 3.1 3200 400 4.00 226.81 14.15 21.96 2.1 3600 400 4.50 229.61 14.41 23.47 1.1 4000 400 5.00 232.77 15.00 24.66 0 4400 400 5.58 232.77 14.93 26.63 0 4800 400 6.17 232.77 14.86 28.59 0

[0162] Table 3. Operating characteristics of the DC system at converter station 3

[0163] <![CDATA[P d ]]> <![CDATA[U d ]]> <![CDATA[I d ]]> <![CDATA[U di0 ]]> angle u nT(i) 800 796.45 0.50 212.97 19.5 3.13 3.8 1600 792.90 1.00 214.08 19.5 5.86 3.3 2400 789.35 1.50 215.20 19.5 8.32 2.9 3200 785.79 2.00 216.32 19.5 10.57 2.5 4000 782.24 2.50 217.43 19.5 12.66 2.1 4800 778.69 3.00 218.55 19.5 14.61 1.6 5600 775.14 3.50 219.67 19.5 16.45 1.2 6400 771.59 4.00 220.78 19.5 18.20 0.8 7200 768.04 4.50 221.90 19.5 19.86 0.4 8000 764.49 5.00 223.02 19.5 21.45 0.0 8800 749.34 5.58 221.37 19.5 23.44 0.6 9600 733.73 6.17 219.69 19.5 25.44 1.2

[0164] In one embodiment of the present invention, a multi-terminal hybrid UHVDC project main circuit parameter calculation system is provided, comprising:

[0165] The DC network matrix acquisition module, based on the traditional network equations of port DC voltage and DC current, obtains the multi-terminal DC system network matrix related to valve group port voltage and DC current of each hybrid converter station under different operating conditions through matrix transformation.

[0166] The DC parameter calculation module uses an N-order matrix normalization method to solve the network matrix of the multi-terminal DC system according to different control modes and combined with the Newton-Raphson method, so as to obtain the DC parameters under multiple control modes.

[0167] The converter parameter calculation module, based on DC parameters, determines the position of the converter transformer tap by giving the trigger and turn-off angles, and then calculates the converter parameters.

[0168] In the above embodiments, calculating the converter parameters includes:

[0169] Under rated conditions, the converter tap position is determined by giving the firing angle and the turn-off angle;

[0170] For other power levels, adjust the converter tap positions so that the parameters of each converter meet the first constraint condition, and calculate the corresponding converter power parameters; wherein, each parameter includes firing angle and turn-off angle, tap limit and DC voltage limit.

[0171] In the above embodiments, determining the converter tap position by giving the firing angle and the turn-off angle includes:

[0172] Given the firing angle and the turn-off angle, determine whether P and Q satisfy the set second constraint condition. If they do, calculate the ideal no-load DC voltage U of the converter based on the DC parameters of the multi-terminal DC system and the control mode of the DC system. di0 The range of the taps is determined; if the range is not met, the DC parameters must be recalculated.

[0173] In the above embodiments, the second constraint condition is: P cmin ≤P≤P cmax and Q acmin ≤Q≤Q acmax ;

[0174] If P and Q do not exceed the limits, then the first constraint condition is satisfied.

[0175] In the above embodiments, adjusting the position of the converter tap includes:

[0176] Adjust the tap changers to meet the first constraint condition without changing the control mode and command value of each converter.

[0177] If the tap changer reaches the adjustment limit specified by the first constraint condition, the control mode or command value of some converter stations will be changed. If the first constraint condition is not met, the DC parameters will be recalculated.

[0178] In the above embodiments, the first constraint is:

[0179] Triggering and shut-off angles of the converter station: α min ≤α≤α max γ min ≤γ≤γ max ;

[0180] Tape limit: n Tcmin ≤n T ≤n Tmax ;

[0181] DC voltage limit: U dmin ≤U d ≤U dmax .

[0182] In the above embodiments, if the first constraint condition is not met, the DC parameters are recalculated, including:

[0183] After calculating the DC parameters, in the original U di0Ri Based on this, the new trigger angle α and turn-off angle γ are determined;

[0184] When the trigger angle α < α min At that time, if the ideal no-load DC voltage U of the converter di0 Since the minimum limit value has not yet been reached, let α = α directly. min Calculate the ideal no-load DC voltage U of the converter. di0 If the ideal no-load DC voltage U of the converter di0 When the limit value is reached, α = α min Then, return to the DC parameter section for calculation and recalculate the parameters of each converter.

[0185] The system provided in this embodiment is used to execute the above-described method embodiments. For specific processes and details, please refer to the above embodiments, which will not be repeated here.

[0186] In one embodiment of the present invention, a computing device is provided, which can be a terminal and may include: a processor, a communication interface, memory, a display screen, and an input device. The processor, communication interface, and memory communicate with each other via a communication bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs, which, when executed by the processor, implement the methods described in the above embodiments. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals. Wireless communication can be achieved through Wi-Fi, a management network, NFC (Near Field Communication), or other technologies. The display screen can be a liquid crystal display or an e-ink display. The input device can be a touch layer covering the display screen, or buttons, a trackball, or a touchpad mounted on the casing of the computing device, or an external keyboard, touchpad, or mouse. The processor can call logical instructions stored in the memory.

[0187] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0188] In one embodiment of the present invention, a computer program product is provided, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, and when the program instructions are executed by a computer, the computer is able to perform the methods provided in the above-described method embodiments.

[0189] In one embodiment of the present invention, a non-transitory computer-readable storage medium is provided, which stores server instructions that cause a computer to perform the methods provided in the above embodiments.

[0190] The computer-readable storage medium provided in the above embodiments has a similar implementation principle and technical effect to the above method embodiments, and will not be described again here.

[0191] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0192] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0193] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0194] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the main circuit parameters of a multi-terminal hybrid ultra-high voltage direct current (UHVDC) project, characterized in that, include: Based on the traditional network equations for port DC voltage and DC current, a multi-terminal DC system network matrix relating valve group port voltage and DC current for each hybrid converter station under different operating conditions is obtained through matrix transformation. The network matrix of the multi-terminal DC system is solved by using the N-order matrix normalization method and combining the Newton-Raphson method according to different control modes, so as to obtain the DC parameters under multiple control modes. Based on DC parameters, the position of the converter transformer tap is determined by giving the trigger and turn-off angles, and the converter parameters are calculated. The network matrix for a multi-terminal DC system is established as follows: In an n-terminal DC transmission system, the admittance matrix is ​​derived using the nodal voltage method. The network matrix applicable to the operating conditions of a multi-terminal DC transmission system is then obtained. The matrix is ​​separated to obtain the general equations (13) and (14) for the hybrid structure. （13） （14） in, U dn , U dn The voltage of each positive and negative converter valve group; R en , R en These are the resistances at the positive and negative neutral points, respectively. I d1H and I d1L These correspond to the currents flowing through the series-connected valve group at the positive and negative terminals, respectively. If there is no series-connected valve group in the network, then... I d1H and I d1L All are 0, and the range of n starts from 1; I dnH , I dnL These are the outlet current vectors of each converter valve group, representing the positive and negative terminals, respectively. U d12 This refers to the voltage of the series valve group; Where A = ; Solving for the network matrix of a multi-terminal DC system includes: listing the network matrix based on the network structure, and solving for the DC voltage and DC current using the Newton-Raphson method based on the control method. Calculate converter parameters, including: Under rated conditions, the converter tap position is determined by giving the firing angle and the turn-off angle; For other power levels, adjust the converter tap positions so that the parameters of each converter meet the first constraint condition, and calculate the corresponding converter power parameters; wherein, each parameter includes firing angle and turn-off angle, tap limit and DC voltage limit.

2. The method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in claim 1, characterized in that, Determine the converter tap position by giving the firing angle and the shutdown angle, including: Given the trigger angle and the shutdown angle, determine P , Q If the second constraint condition is met, then the ideal no-load DC voltage of the converter is calculated based on the DC parameters of the multi-terminal DC system and the control method of the DC system. U di0 The range of the taps is determined; if the range is not met, the DC parameters must be recalculated.

3. The method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in claim 2, characterized in that, The second constraint is: and ; like P , Q If the limit is not exceeded, then the first constraint condition is satisfied; To minimize the active power delivered by the converter, To maximize the active power delivered by the converter, To minimize reactive power consumption at the converter station This represents the maximum reactive power consumption of the converter station.

4. The method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in claim 1, characterized in that, Adjusting the position of the converter taps includes: Adjust the tap changers to meet the first constraint condition without changing the control mode and command value of each converter. If the tap changer reaches the adjustment limit specified by the first constraint condition, the control mode or command value of some converter stations will be changed. If the first constraint condition is not met, the DC parameters will be recalculated.

5. The method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in claim 4, characterized in that, The first constraint is: Triggering and shutdown angles of the converter station: , ; Tape limitations: ; DC voltage limit: .

6. The method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in claim 4, characterized in that, If the first constraint condition is not met, the DC parameters are recalculated, including: After calculating the DC parameters, at the original ideal no-load voltage U di0Ri Based on this, determine the new trigger angle. and shut-off angle ; When trigger angle At that time, if the ideal no-load DC voltage of the converter U di0 The minimum limit value has not yet been reached, so let's directly set... Calculate the ideal no-load DC voltage of the converter. U di0 If the ideal no-load DC voltage of the converter U di0 Reaching the limit, at this point Then, return to the DC parameter section for calculation and recalculate the parameters of each converter.

7. A system for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project, used to implement the method for calculating the main circuit parameters of a multi-terminal hybrid UHVDC project as described in any one of claims 1 to 6, characterized in that, include: The DC network matrix acquisition module, based on the traditional network equations of port DC voltage and DC current, obtains the multi-terminal DC system network matrix related to valve group port voltage and DC current of each hybrid converter station under different operating conditions through matrix transformation. The DC parameter calculation module uses an N-order matrix normalization method to solve the network matrix of the multi-terminal DC system according to different control modes and combined with the Newton-Raphson method, so as to obtain the DC parameters under multiple control modes. The converter parameter calculation module, based on DC parameters, determines the position of the converter transformer tap by giving the trigger and turn-off angles, and then calculates the converter parameters.

8. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods described in claims 1 to 6.

9. A computing device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods described in claims 1 to 6.

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