An evaluation method for voltage interaction between sending and receiving ends of embedded DC system

Abstract

The present invention discloses an evaluation method for the interactive influence of voltages at the sending and receiving ends of an embedded direct current system, and belongs to the technical field of power generation, transformation or distribution. The method firstly calculates the interactive influence of the voltages of the sending and receiving end converter buses coupled by the alternating current grid based on the modified power flow equation matrix; then, calculates the trigger angle change on the rectifier side caused by the voltage drop of the converter bus at the receiving end, calculates the reactive power shortage of the converter station at the sending end caused by the trigger angle change, and calculates the voltage drop of the converter bus at the sending end caused by the self-regulation of the direct current system according to the reactive power shortage of the converter station at the sending end; finally, comprehensively considers the influence of the coupling of the alternating current grid and the regulation of the direct current system, calculates the influence of the voltage drop of the converter bus at the receiving end of the embedded direct current system on the converter bus voltage at the sending end, and achieves the purpose of accurately evaluating the influence between the converter stations at the sending and receiving ends of the embedded direct current system.

Description

Technical Field

[0001] The invention relates to power system safety and stability analysis and control technology, and in particular discloses an evaluation method for voltage interaction between commutation buses at the sending and receiving ends of an embedded direct current system, belonging to the technical field of power generation, transformation or distribution. Background Art

[0002] With the rapid development of social economy, the demand for electric energy in load center areas is increasing day by day, which puts forward higher requirements on the power grid's transmission capacity and new energy absorption capacity in its key sections and regions. DC transmission technology has fast and flexible power regulation, large transmission capacity in a limited space, and small footprint, which is an effective technical means to meet the above requirements. Therefore, Jiangsu Power Grid took the lead in proposing to build an embedded DC system within the provincial AC power grid. Different from the long-distance and large-capacity DC transmission system built by the traditional regional power grid interconnection method, the converter stations at both ends of the embedded DC system are built within the same provincial AC power grid, thereby greatly improving the power grid transmission capacity and the flexibility of power grid control within the limited transmission corridor space. The traditional regional interconnected DC system is shown in Figure 1(a), and the embedded DC system is shown in Figure 1(b).

[0003] Evaluating the voltage interaction between converter stations in a DC system is of great significance for understanding the voltage stability of the power system and can guide the planning, operation and control of the power system. Current research on voltage interaction mostly focuses on the voltage interaction between converter stations at the receiving end of different DC systems when the receiving end converter stations are located in the same AC power grid. The interaction impact factor is solved based on the impedance network or Jacobian matrix. In essence, it evaluates the interaction effect caused by the coupling of the AC power grid at the receiving end of the converter station. A few studies have converted the impact between different DC sending-end converter stations for multiple DC co-transmitting and co-receiving systems, and then evaluated the voltage interaction of converter stations at the receiving end of different DC systems. In essence, it calculates the coupling effect of the sending-end AC power grid and the receiving-end AC power grid separately, and then performs a weighted summation.

[0004] However, for embedded DC systems, the converter stations at the sending and receiving ends of the same DC system are located in the same provincial AC power grid. The interaction between the sending and receiving ends includes both the coupling effect of the AC power grid and the voltage regulation characteristics of the DC system itself. Therefore, when evaluating the interaction between the sending and receiving voltages, both the AC power grid and the DC system must be considered comprehensively. However, the current evaluation methods and indicators essentially reflect the coupling effect of converter stations of different DC systems through the AC power grid, and cannot accurately measure the interaction between converter stations at the sending and receiving ends of embedded DC systems. Therefore, they cannot be directly used to evaluate the degree of interaction between the sending and receiving voltages of embedded DC systems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the voltage interaction between the sending and receiving ends of an embedded DC system in order to address the shortcomings of the above-mentioned background technology and solve the technical problem that current research cannot accurately evaluate the degree of voltage interaction between the sending and receiving ends of an embedded DC system.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned invention object:

[0007] A method for evaluating the voltage interaction between sending and receiving ends of an embedded DC system comprises the following steps:

[0008] Step 1: Calculate the interaction between the voltage of the commutation busbars at the sending and receiving ends of the embedded DC system coupled with the AC grid according to the modified power flow equation matrix;

[0009] Step 2, calculating the voltage drop of the commutation busbar at the sending end of the embedded DC system caused by the DC system's own regulation;

[0010] Step three, comprehensively consider the influence of AC grid coupling and DC system self-regulation on the commutation bus voltage at the sending end of the embedded DC system, and calculate the final change of the commutation bus voltage at the sending end of the embedded DC system.

[0011] As a further optimization scheme for the evaluation method of the voltage interaction between the sending and receiving ends of an embedded DC system, in step one, the method for obtaining the modified power flow equation matrix is ​​as follows: considering the influence of the reactive power fed into the commutation bus nodes at the sending and receiving ends of the embedded DC system on the commutation bus nodes at the sending and receiving ends, the elements representing the commutation bus nodes at the sending and receiving ends of the embedded DC system in the sub-matrix J related to the AC system power flow equation and the node reactive power are modified.

[0012] As a further optimization scheme for evaluating the voltage interaction between the sending and receiving ends of an embedded DC system, the specific method for correcting the elements representing the commutation bus nodes at the sending and receiving ends of the embedded DC system in the sub-matrix J related to the AC system power flow equation and the node reactive power is as follows: the element J in the ith row and ith column of the sub-matrix J is recorded as ii The rth row and rth column element J of the submatrix J is the element representing the receiving end commutation bus node i of the embedded DC system. rr The element J' in the ith row and ith column of the modified submatrix J is the element representing the commutation bus node r at the sending end of the embedded DC system. ii And the r-th row and r-th column element J' of the modified submatrix J rr for Among them, Q di represents the reactive power fed into the receiving-end commutation bus node i of the embedded DC system, Q dr represents the reactive power fed into the commutation bus node r at the sending end of the embedded DC system, V i and V rThey respectively represent the voltage of the commutation bus node i at the receiving end of the embedded DC system and the voltage of the commutation bus node r at the sending end of the embedded DC system.

[0013] As a further optimization scheme for evaluating the interactive impact of voltages at the sending and receiving ends of an embedded DC system, the expression for calculating the interactive impact of the voltages at the sending and receiving ends of the embedded DC system coupled via the AC grid in step 1 is: Where, ΔV r_ac represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to AC grid coupling, represents the i-th row and r-th column element of the inverse matrix of the modified submatrix J, represents the rth row and rth column element of the inverse matrix of the modified submatrix J, ΔV i It represents the voltage amplitude change of the receiving-end commutation bus node i of the embedded DC system.

[0014] As a further optimization scheme for the evaluation method of the voltage interaction between the sending and receiving ends of an embedded DC system, the specific method for calculating the voltage drop of the commutation busbar at the sending end of the embedded DC system caused by the DC system's own regulation in step 2 is:

[0015] Calculate the trigger angle change on the rectifier side caused by the voltage drop of the commutation busbar at the receiving end of the embedded DC system. Among them, α′ represents the changed trigger angle of the rectifier side of the embedded DC system, α represents the trigger angle of the rectifier side of the embedded DC system, and γ represents the shutdown angle of the inverter side of the embedded DC system;

[0016] Calculate the reactive power shortage of the embedded DC system sending-end converter station caused by the change of the rectifier side trigger angle. Among them, Q demand represents the reactive power shortage at the commutation busbar of the embedded DC system, Q' dr represents the reactive power of the commutation bus node r at the sending end of the embedded DC system after the change, N r represents the number of rectifier bridges at the commutation bus node r at the sending end of the embedded DC system, T r represents the transformer ratio at the commutation bus node r of the embedded DC system, X c represents the commutation reactance, B represents the susceptance of the reactive compensation device;

[0017] Calculate the voltage drop of the sending-end converter bus caused by the reactive power shortage of the embedded DC system sending-end converter station. Where, ΔV r_dc represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the DC system regulation, X eqrepresents the impedance of the equivalent generator in the sending-end area grid, E g represents the terminal voltage of the equivalent generator in the sending-end regional power grid, and δ represents the phase difference between the terminal voltage of the equivalent generator in the sending-end regional power grid and the commutation bus voltage at the sending end of the embedded DC system.

[0018] As a further optimization scheme for the evaluation method of the voltage interaction between the sending and receiving ends of an embedded DC system, the method for calculating the final change in the voltage of the commutation bus at the sending end of the embedded DC system in step three is: taking the maximum value of the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the coupling of the AC grid and the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the regulation of the DC system.

[0019] As a further optimization scheme for the evaluation method of the voltage interaction between the sending and receiving ends of an embedded DC system, the AC system power flow equation is: Among them, ΔP, ΔQ, Δθ, and ΔV represent the node active power change matrix, reactive power change matrix, voltage phase angle change matrix, and voltage amplitude change matrix, respectively. K and J are sub-matrices related to node active power and reactive power, respectively. h and o represent the number of nodes and PQ nodes respectively, m and n represent the node numbers, i and j represent the PQ node numbers, and K mn and J mn Represent the mth row and nth column elements of submatrix K and submatrix J, respectively. m and V n They represent the voltages of nodes m and n, respectively, and b mn Represents the imaginary part of the element in the mth row and nth column of the node impedance matrix.

[0020] As a further optimization scheme for the evaluation method of the voltage interaction between the sending and receiving ends of an embedded DC system, the reactive power Q fed into the receiving end commutation bus node i of the embedded DC system is di for Among them, N i represents the number of inverter bridges at the receiving end commutation bus node i of the embedded DC system, T i is the transformation ratio of the converter transformer at the receiving-end commutation bus node i of the embedded DC system, and β represents the triggering lead angle of the inverter side of the embedded DC system.

[0021] An electronic device includes a memory and a processor. The memory stores a computer program that runs on the processor. When the processor runs the computer program, the steps of the above-mentioned evaluation method are executed.

[0022] A computer-readable storage medium stores a computer program, which executes the steps of the above-mentioned evaluation method when the computer program is run.

[0023] The present invention adopts the above technical scheme and has the following beneficial effects: the present invention aims at the influence between the sending and receiving end converter stations of the same DC system in the provincial AC power grid, and at the same time corrects the sending and receiving end converter bus nodes in the power flow equation to obtain a more accurate influence degree of the sending and receiving end converter bus voltages coupled by the AC power grid, and takes into account the regulation characteristics of the DC system itself to calculate the sending end converter bus voltage drop, so as to accurately evaluate the influence between the sending and receiving end converter stations, and finally comprehensively considers the influence of the AC power grid coupling and the DC system regulation to determine the final transformation amount of the sending end converter bus voltage, filling the gap in the current research on the evaluation of the interactive influence of the sending and receiving end voltages of the embedded DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1(a) is a schematic diagram of the structure of a traditional regional interconnected DC system in an actual power grid, and FIG1(b) is a schematic diagram of the structure of an embedded DC system in an actual power grid.

[0025] Figure 2 The present invention provides a flow chart of a method for evaluating the voltage interaction between the commutation buses at the sending and receiving ends of an embedded DC system.

[0026] Figure 3 This is a simulation model diagram of a power system including an embedded DC system built in PSCAD / EMTDC in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0028] like Figure 2 As shown, the evaluation method for the interactive influence of the commutation bus voltages at the sending and receiving ends of the embedded DC system proposed in the present invention includes three major steps; the first step is to calculate the interactive influence of the commutation bus voltages at the sending and receiving ends coupled by the AC power grid based on the modified power flow equation matrix, which is specifically implemented through steps 1 to 2; the second step is to calculate the voltage drop of the commutation bus at the sending end caused by the self-regulation of the DC system according to the reactive power shortage of the sending-end converter station, which is implemented through steps 3 to 5; the third step is to comprehensively consider the influence of the coupling of the AC power grid and the regulation of the DC system, and calculate the influence of the voltage drop of the commutation bus at the receiving end of the embedded DC system on the voltage of the commutation bus at the sending end, which is implemented through step 6.

[0029] Step 1: Construct the modified power flow equation matrix

[0030] The power flow equation of the AC system is established as shown in formula (1):

[0031]

[0032] Where: ΔP, ΔQ, Δθ, and ΔV represent the node active power change matrix, reactive power change matrix, voltage phase angle change matrix, and voltage amplitude change matrix, respectively.

[0033] Among them, the sub-matrices K and J can be obtained by formula (2):

[0034]

[0035] Where: V represents the node voltage, b is the imaginary part of the node impedance matrix, h and o represent the number of nodes and the number of PQ nodes respectively, m and n represent the node numbers, i and j represent the PQ node numbers, V m and V n They represent the voltages of nodes m and n, respectively, and b mn represents the imaginary part of the element in the mth row and nth column of the node impedance matrix, K mn and J mn They represent the m-th row and n-th column elements of submatrix K and submatrix J respectively.

[0036] Since there is an embedded DC system in the AC power grid, the above sub-matrix must be corrected considering the power of the embedded DC system. Since reactive power is independent of voltage phase, only the elements representing the commutation bus nodes at the sending and receiving ends of the embedded DC system in the sub-matrix J need to be corrected:

[0037]

[0038] Where: Q di represents the reactive power fed into the receiving-end commutation bus node i of the embedded DC system, Q dr represents the reactive power fed into the commutation bus node r at the sending end of the embedded DC system, V i and V r They represent the voltage of the commutation bus node i at the receiving end of the embedded DC system and the commutation bus node r at the sending end of the embedded DC system, respectively. ii represents the i-th row and i-th column element of submatrix J, J' ii represents the i-th row and i-th column element of the modified submatrix J, J rr represents the r-th row and r-th column element of submatrix J, J' rr represents the r-th row and r-th column element of the modified submatrix J.

[0039] For the embedded DC system receiving end commutation bus node i, Q di for:

[0040]

[0041] Where: N irepresents the number of inverter bridges at the receiving end commutation bus node i of the embedded DC system, T i is the conversion transformer ratio at the receiving end of the embedded DC system at the commutation bus node i, X c represents the commutation reactance, γ and β represent the inverter-side turn-off angle and trigger advance angle of the embedded DC system, respectively.

[0042] For the embedded DC system sending end commutation bus node r, then Q dr for:

[0043]

[0044] Where: α represents the trigger angle of the rectifier side of the embedded DC system, T r is the ratio of the converter transformer at the commutation bus node r of the embedded DC system, N r It represents the number of rectifier bridges at the commutation bus node r at the sending end of the embedded DC system.

[0045] Step 2: Calculate the interaction between the voltages of the commutation busbars at the sending and receiving ends coupled via the AC grid.

[0046] According to the modified power flow equation matrix, the influence of the voltage change of the receiving-end commutation bus node i of the embedded DC system on the voltage of the sending-end commutation bus node r is calculated through the AC grid coupling:

[0047]

[0048] Where: (J′) -1 represents the inverse matrix of the modified submatrix J, represents the i-th row and r-th column element of the inverse matrix of the modified submatrix J, represents the rth row and rth column element of the inverse matrix of the modified submatrix J, ΔV i It represents the voltage amplitude change of the receiving-end commutation bus node i of the embedded DC system, ΔV r_ac It represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the AC grid coupling.

[0049] Step 3: Calculate the trigger angle change on the rectifier side caused by the voltage drop of the receiving-end commutation busbar

[0050] When the commutation bus voltage at the receiving end of the embedded DC system drops, considering that the DC system has a tendency to maintain a constant current and the receiving end adopts a fixed turn-off angle control strategy, the following equation holds true:

[0051] U dr0 cosα-U di0 cosγ=U dr0 cosα′-(U di0 -ΔUi )cosγ (7)

[0052] Where: U dr0 and U di0 They represent the ideal no-load DC voltage at the sending and receiving ends of the embedded DC system, ΔU i It represents the change of DC voltage at the receiving end of the embedded DC system, and α′ represents the trigger angle of the rectifier side of the embedded DC system after the change.

[0053] The ideal no-load DC voltage and the commutation bus voltage have the following relationship:

[0054]

[0055] Therefore, formula (7) can be written as:

[0056] V r cosα-V i cosγ=V r cosα′-(V i -ΔV i )cosγ (9)

[0057] Therefore, the change of the trigger angle on the rectifier side caused by the change of the commutation bus voltage at the receiving end of the embedded DC system can be calculated:

[0058]

[0059] Step 4: Calculate the reactive power shortage of the sending-end converter station caused by the change in the trigger angle on the rectifier side

[0060] When the trigger angle of the rectifier side of the embedded DC system changes, the reactive power of the commutation bus at the sending end changes to Q' dr , as the trigger angle on the rectifier side increases, the reactive power increases.

[0061]

[0062] At this time, since the commutation bus voltage at the sending end has not changed in time, the reactive power that the reactive compensation device can provide is still:

[0063]

[0064] Where: Q device It represents the reactive power provided by the reactive power compensation device, and B represents the susceptance of the reactive power compensation device.

[0065] The reactive power shortage caused by the change of the trigger angle on the rectifier side at the commutation bus of the embedded DC system is further calculated:

[0066]

[0067] Where: Q demand Indicates the reactive power shortage at the commutation bus at the sending end of the embedded DC system.

[0068] Step 5: Calculate the voltage drop of the sending-end commutation bus caused by reactive power shortage

[0069] For the embedded DC system sending-end commutation bus, the sending-end regional power grid is equivalent to a large generator, and the reactive power provided to the sending-end commutation bus is calculated by the following formula:

[0070]

[0071] Where: Q g represents the reactive power provided by the power grid in the sending area, X eq represents the impedance of the equivalent generator in the sending-end area grid, E g represents the terminal voltage of the equivalent generator in the sending-end regional power grid, and δ represents the phase difference between the terminal voltage of the equivalent generator in the sending-end regional power grid and the commutation bus voltage at the sending end of the embedded DC system.

[0072] Q described by formula (14) g -V r The intersection of the curve and the reactive power load curve parallel to the horizontal axis determines the voltage of the commutation busbar at the sending end of the embedded DC system under this reactive power balance. When there is a reactive power shortage causing the reactive power load curve to shift upward, the horizontal coordinate corresponding to the new intersection of the two curves will decrease, that is, V r Will decrease.

[0073] Therefore, when there is a reactive power shortage Q demand , the voltage change of the commutation busbar at the sending end of the embedded DC system can be approximately calculated by the following formula:

[0074]

[0075] Where: ΔV rdc It represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the DC system regulation.

[0076] Step 6: Calculate the final change in the sending-end commutation bus voltage

[0077] Taking into account the influence of AC grid coupling and DC system regulation, the influence of the receiving-end commutation bus voltage drop of the embedded DC system on the sending-end commutation bus voltage is obtained:

[0078] When the voltage of the commutation bus at the receiving end of the embedded DC system drops, the voltage change of the commutation bus at the sending end should be the maximum value of the AC grid coupling effect and the DC system regulation effect. Therefore, the final voltage change is:

[0079] ΔV r =max(ΔV r_ac ,ΔV r_dc ) (16)

[0080] Where: ΔV r It represents the final change of the commutation bus voltage at the sending end of the embedded DC system, and max represents a larger value.

[0081] An example is given below to verify the effectiveness of the method proposed in the present invention.

[0082] Built in PSCAD / EMTDC Figure 3 The power system with embedded DC shown in the figure is simulated with electromagnetic transient. Figure 3 In the figure, the two generators on the left and right are the equivalent generators of the power grid in the sending end area and the equivalent generators of the power grid in the receiving end area respectively. The thyristor loop on the top represents the embedded DC system, and the impedance on the bottom represents the AC grid tie line.

[0083] An inductive reactive load is added to the receiving-end commutation bus of the embedded DC system, causing its voltage to drop by 0.01 pu. The voltage change of the commutation bus at the sending end of the embedded DC system calculated by the method of the present invention is 0.0055. The simulation results show that the actual voltage change of the commutation bus at the sending end of the embedded DC system is 0.0061, and the relative error of the calculation result of the method of the present invention is only 9.8%. It can be seen from the above simulation data that the calculation method proposed by the present invention can accurately evaluate the interactive influence of the commutation bus voltage at the sending and receiving ends of the embedded DC system.

[0084] This embodiment further provides an electronic device, including a memory and a processor, wherein the memory stores a computer program that runs on the processor, and the processor executes the steps of the above-mentioned evaluation method when running the computer program.

[0085] This embodiment also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run, the steps of the above-mentioned evaluation method are executed.

Claims

1. A method for evaluating the voltage interaction between the sending and receiving ends of an embedded DC system, characterized in that: The steps include: Step 1: According to the modified power flow equation matrix, the interaction effect of the commutation bus voltages at the sending and receiving ends of the embedded DC system coupled with the AC grid is calculated. The method for obtaining the modified power flow equation matrix is ​​as follows: considering the influence of the reactive power fed into the commutation bus node at the sending and receiving ends of the embedded DC system on the commutation bus node at the sending and receiving ends, the elements representing the commutation bus node at the sending and receiving ends of the embedded DC system in the sub-matrix J related to the AC system power flow equation and the node reactive power are modified. The specific method for modifying the elements representing the commutation bus node at the sending and receiving ends of the embedded DC system in the sub-matrix J related to the AC system power flow equation and the node reactive power is as follows: record the element J in the i-th row and i-th column of the sub-matrix J ii The rth row and rth column element J of the submatrix J is the element representing the receiving end commutation bus node i of the embedded DC system. rr The element J' in the ith row and ith column of the modified submatrix J is the element representing the commutation bus node r at the sending end of the embedded DC system. ii And the r-th row and r-th column element J' of the modified submatrix J rr for Among them, Q di represents the reactive power fed into the receiving-end commutation bus node i of the embedded DC system, Q dr represents the reactive power fed into the commutation bus node r at the sending end of the embedded DC system, V i and V r They represent the voltage of the commutation bus node i at the receiving end of the embedded DC system and the voltage of the commutation bus node r at the sending end of the embedded DC system, respectively. The expression for calculating the interaction between the voltage of the commutation busbars at the sending and receiving ends of the embedded DC system coupled with the AC grid is: Where, ΔV r_ac represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to AC grid coupling, represents the i-th row and r-th column element of the inverse matrix of the modified submatrix J, represents the rth row and rth column element of the inverse matrix of the modified submatrix J, ΔV i It represents the voltage amplitude change of the receiving-end commutation bus node i of the embedded DC system; Step 2: Calculate the voltage drop of the commutation busbar at the sending end of the embedded DC system caused by the DC system's own regulation. The specific method is: Calculate the trigger angle change on the rectifier side caused by the voltage drop of the commutation busbar at the receiving end of the embedded DC system. Among them, α′ represents the changed trigger angle of the rectifier side of the embedded DC system, α represents the trigger angle of the rectifier side of the embedded DC system, and γ represents the shutdown angle of the inverter side of the embedded DC system. Calculate the reactive power shortage of the embedded DC system sending-end converter station caused by the change of the rectifier side trigger angle, Q demand =Q' dr -BV r 2 , where Q demand represents the reactive power shortage at the commutation busbar of the embedded DC system, Q' dr represents the reactive power of the commutation bus node r at the sending end of the embedded DC system after the change, N r represents the number of rectifier bridges at the commutation bus node r at the sending end of the embedded DC system, T r represents the transformer ratio at the commutation bus node r of the embedded DC system, X c represents the commutation reactance, B represents the susceptance of the reactive compensation device, Calculate the voltage drop of the sending-end converter bus caused by the reactive power shortage of the embedded DC system sending-end converter station. Where, ΔV r_dc represents the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to the DC system regulation, X eq represents the impedance of the equivalent generator in the sending-end area grid, E g represents the terminal voltage of the equivalent generator in the sending-end regional power grid, δ represents the phase difference between the terminal voltage of the equivalent generator in the sending-end regional power grid and the commutation bus voltage at the sending end of the embedded DC system; Step three, comprehensively considering the influence of AC grid coupling and DC system self-regulation on the commutation bus voltage at the sending end of the embedded DC system, calculate the final change of the commutation bus voltage at the sending end of the embedded DC system. The method for calculating the final change of the commutation bus voltage at the sending end of the embedded DC system is: take the maximum value of the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to AC grid coupling and the voltage amplitude change of the commutation bus node r at the sending end of the embedded DC system due to DC system regulation.

2. According to claim 1, a method for evaluating the voltage interaction between the sending and receiving ends of an embedded DC system is characterized in that: The AC system power flow equation is: Among them, ΔP, ΔQ, Δθ, and ΔV represent the node active power change matrix, reactive power change matrix, voltage phase angle change matrix, and voltage amplitude change matrix, respectively. K and J are sub-matrices related to node active power and reactive power, respectively. h and o represent the number of nodes and PQ nodes respectively, m and n represent the node numbers, i and j represent the PQ node numbers, and K mn and J mn Represent the mth row and nth column elements of submatrix K and submatrix J, respectively. m and V n They represent the voltages of nodes m and n, respectively, and b mn Represents the imaginary part of the element in the mth row and nth column of the node impedance matrix.

3. According to claim 1, a method for evaluating the voltage interaction between the sending and receiving ends of an embedded DC system is characterized in that: The embedded DC system receives the reactive power Q fed into the commutation bus node i at the receiving end. di for Among them, N i represents the number of inverter bridges at the receiving end commutation bus node i of the embedded DC system, T i is the transformation ratio of the converter transformer at the receiving-end commutation bus node i of the embedded DC system, and β represents the triggering lead angle of the inverter side of the embedded DC system.

4. An electronic device comprising a memory and a processor, wherein the memory stores a computer program to be executed by the processor, and the processor executes the steps of the evaluation method according to claim 1 when executing the computer program.

5. A computer-readable storage medium having a computer program stored thereon, wherein the computer program executes the steps of the evaluation method according to claim 1 when executed.

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