Stable control power distribution method and device for two-end modified three-end parallel DC line

Abstract

The application relates to a safe and stable control power distribution method and device of a two-end modified three-end parallel DC line. In the safe and stable control power distribution process of the two-end modified three-end parallel DC line, the power sending and receiving mode of the three-end converter station is determined according to the power sending capacity of the newly-added sending-end converter station and the power consumption capacity of the original two-end converter station, and the power coordination control principle and the power distribution implementation method of the power promotion and reduction function actions of each station in the power sending and receiving mode of 'one-end power sending and two-end power receiving' and 'two-end power sending and one-end power receiving' are respectively designed, so that the power distribution of the two receiving ends in the 'one-end power sending and two-end power receiving' mode can preferentially meet the power receiving of the original two-end converter station inverter station, and the power distribution of the two sending ends in the 'two-end power sending and one-end power receiving' mode can preferentially meet the power sending of the newly-built station, and the efficiency and accuracy of the power distribution of the parallel three-end DC project are improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to direct current transmission, and in particular to a method and device for stably controlling power distribution of a two-terminal to three-terminal parallel direct current line. Background Art

[0002] As the local power consumption capacity of sending-end converter stations increases or demand from receiving-end converter stations grows, when the power output of the sending-end converter station in a two-terminal DC project cannot meet the power input of the receiving-end converter station, cost considerations lead to the development of a parallel three-terminal DC project by adding a new converter station to the existing two-terminal DC project. This approach typically involves a rectifier station with high power output potential. The power output station of the original two-terminal converter station must function as both a rectifier station and an inverter station, enabling both power output and power input. The power input station of the original two-terminal converter station remains an inverter station. This requires the parallel three-terminal DC project to implement two three-terminal operation modes: "one-to-two" and "two-to-one."

[0003] Power boost and power reduction are the two main functions of safety and stability control. The question of how to achieve power allocation between the two receiving terminals in a "one-to-two" approach, prioritizing the power input of the original converter and inverter stations, and the power allocation between the two sending terminals in a "two-to-one" approach, prioritizing the power output of the newly built stations, is still under research in China. Summary of the Invention

[0004] Based on the above situation of the prior art, the purpose of the present invention is to provide a method and device for stable control of power distribution of a two-terminal to three-terminal parallel DC line, which are respectively designed for the "one-to-two" operation mode and the "two-to-one" operation mode, and the three-station power coordination control principle and power distribution implementation method when the power boost and reduction functions of each station are activated, so as to achieve the power distribution of the two receiving ends in the "one-to-two" mode to give priority to meeting the power intake of the original two-terminal converter stations and inverter stations, and the power distribution of the two sending ends in the "two-to-one" mode to give priority to meeting the power output function of the newly built station.

[0005] To achieve the above object, according to one aspect of the present invention, a method for stably controlling power distribution in a two-terminal to three-terminal parallel DC line is provided, comprising the steps of:

[0006] Calculate the bipolar power capacity and bipolar power at terminals A, B, and C in a three-terminal DC line;

[0007] The power transmission and reception mode of the three-terminal converter station is determined based on the power transmission capacity of the newly added sending-end converter station A and the power absorption capacity of the original two-end converter stations B and C;

[0008] Based on the power transmission and reception mode:

[0009] Calculate the power capacity of converter stations B and C or A and B for participating in safety and stability control;

[0010] The power changes of the three-terminal converter stations A, B, and C are calculated based on the activation status of each terminal of the three-terminal converter station and the power capacity participating in the stability control.

[0011] Furthermore, the calculation of the bipolar power capacity and bipolar power of each terminal in the three-terminal DC line includes:

[0012] P SA_CAP =Ud SAP1_ACT *I SAP1_LMT +Ud SAP2_ACT *I SAP2_LMT

[0013] P SB_CAP =Ud SAP1_ACT *I SBP1_LMT +Ud SAP2_ACT *I SBP2_LMT

[0014] P SC_CAP =Ud SAP1_ACT *I SCP1_LMT +Ud SAP2_ACT *I SCP2_LMT

[0015] P SA_DCP =Ud SAP1_ACT *I SAP1_REF +Ud SAP2_ACT *I SAP2_REF

[0016] P SB_DCP =Ud SAP1_ACT *I SBP1_REF +Ud SAP2_ACT *I SBP2_REF

[0017] P SC_DCP =Ud SAP1_ACT *I SCP1_REF +Ud SAP2_ACT *I SCP2_REF

[0018] Among them, P SA_CAP 、P SB_CAP 、P SC_CAP are the bipolar power capacities of the three-terminal converter stations A, B, and C, respectively, P SA_DCP 、P SB_DCP 、P CA_DCP are the bipolar powers of the three-terminal converter stations A, B, and C, respectively, and Ud SAP1_ACT 、Ud SAP2_ACTare the actual values ​​of DC voltage at the two poles of converter station A, I SAP1_LMT , I SAP2_LMT , I SBP1_LMT 、、I SBP2_LMT , I SCP1_LMT , I SCP2_LMT are the current limit values ​​of the three-terminal converter station A, B, and C, respectively. SAP1_REF , I SAP2_REF , I SBP1_REF 、、I SBP2_REF , I SCP1_REF , I SCP2_REF They are the current reference values ​​of the two poles A, B and C of the three-terminal converter station respectively.

[0019] Furthermore, based on the power delivery capacity of the newly added sending-end converter station and the power absorption capacity of the original two-end converter stations, the power transmission and reception mode of the three-end converter station is determined, including:

[0020] If the power transmission capacity of the newly added sending-end converter station is greater than the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be one-end transmission and two-end reception.

[0021] If the power transmission capacity of the newly added sending-end converter station is less than or equal to the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be power transmission at both ends and power reception at one end.

[0022] Furthermore, in a mode where power is transmitted at one end and received at both ends, the power capacity of converter stations B and C used to participate in safety and stability control is calculated by the following formula:

[0023] P' SB_CAP =P SA_CAP -P SC_DCP

[0024] P' SC_CAP =P SA_CAP -P SB_DCP

[0025] Among them, P' SB_CAP and P' SC_CAP They are the power capacities of converter stations B and C used for participating in stability control.

[0026] Furthermore, in the mode of power transmission at one end and power reception at both ends, if the power boost of converter station A at the transmission end is activated and the power boost amount received by converter station A is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0027] △P SA =△PSA_RU

[0028] △P SB =MAX{0,△P SA_RU –(P' SC_CAP –P SC_DCP )}

[0029] △P SC =MIN{△P SA_RU ,P' SC_CAP –P SC_DCP}

[0030] If the power boost of the receiving end converter station B is activated, and the power boost amount of converter station B to be boosted is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0031] △P SA =△P SB_RU

[0032] △P SB =△P SB_RU

[0033] △P SC =0

[0034] If the power boost at the receiving converter station C is activated, and the power boost received by the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0035] △P SA =△P SC_RU

[0036] △P SB =0

[0037] △P SC =△P SC_RU

[0038] Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

[0039] Furthermore, in the mode of power transmission at one end and power reception at both ends, if the power reduction function of the converter station A at the transmission end is activated and the power reduction amount received by the converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △PSC Calculated by the following formula:

[0040] △P SA =△P SA_RB

[0041] △P SB =MIN{△P SA_RB , P SB_DCP –0.05*N DBLK_NUM}

[0042] △P SC =MAX{0,△P SA_RB –(P SB_DCP –0.05*N DBLK_NUM )}

[0043] If the power reduction at the receiving-end converter station B is activated, and the power reduction amount received by the converter station B is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0044] △P SA =△P SB_RB

[0045] △P SB =△P SB_RB

[0046] △P SC =0

[0047] If the power reduction function of the receiving converter station C is activated, and the power reduction amount received by the converter station C is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0048] △P SA =△P SC_RB

[0049] △P SB =0

[0050] △P SC =△P SC_RB

[0051] Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

[0052] Furthermore, in a mode where both ends transmit power and one end receives power, the power capacity of converter stations A and B used to participate in safety and stability control is calculated by the following formula:

[0053] P' SA_CAP =P SC_CAP -P SB_DCP

[0054] P' SB_CAP =P SC_CAP -P SA_DCP

[0055] Furthermore, in the mode of power transmission at both ends and power reception at one end, if the power boost of converter station A at the transmission end is activated and the power boost amount received by converter station A is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0056] △P SA =△P SA_RU

[0057] △P SB =0

[0058] △P SC =△P SA_RU

[0059] If the power boost at the transmission-end converter station B is activated, and the power boost received by converter station B is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0060] △P SA =0

[0061] △P SB =△P SB_RU

[0062] △P SC =△P SB_RU

[0063] If the power boost at the receiving converter station C is activated, and the power boost received by the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0064] △P SA=MIN{△P SC_RU ,P' SA_CAP –P SA_DCP}

[0065] △P SB =MAX{0,△P SC_RU –(P' SA_CAP –P SA_DCP )}

[0066] △P SC =△P SC_RU

[0067] Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

[0068] Furthermore, in the mode of power transmission at both ends and power reception at one end, if the power reduction function of the converter station A at the transmission end is activated and the power reduction amount received by the converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0069] △P SA =△P SA_RB

[0070] △P SB =0

[0071] △P SC =△P SA_RB

[0072] If the power reduction function of the converter station B at the transmission end is activated, and the power reduction amount received by the converter station B is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0073] △P SA =0

[0074] △P SB =△P SB_RU

[0075] △P SC =△P SB_RU

[0076] If the power reduction function of the receiving converter station C is activated, and the power reduction amount received by the converter station C is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SBand △P SC Calculated by the following formula:

[0077] △P SA =MAX{0,△P SC_RB –(P SB_DCP –0.05*N DBLK_NUM )}

[0078] △P SB =MIN{△P SC_RB ,P SB_DCP –0.05*N DBLK_NUM}

[0079] △P SC =△P SC_RU

[0080] Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

[0081] According to another aspect of the present invention, a stable control power distribution device for a two-terminal to three-terminal parallel DC line is provided, comprising a power calculation module, a power transmission and reception mode determination module, and a power distribution module; wherein,

[0082] The power calculation module calculates the bipolar power capacity and bipolar power of each terminal in the three-terminal DC line;

[0083] The power transmission and reception mode determination module determines the power transmission and reception mode of the three-terminal converter station based on the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-terminal converter stations;

[0084] The power distribution module calculates the power capacity of converter stations B and C or A and B for participating in safety and stability control under different power transmission and reception modes; and calculates the power change of the three-terminal converter stations A, B, and C based on the activation status of each end of the three-terminal converter station and the power capacity participating in safety and stability control.

[0085] In summary, the present invention provides a method and device for stable power distribution control of a two-terminal to three-terminal parallel DC line. In the process of stable power distribution control of the two-terminal to three-terminal parallel DC line, the power transmission and reception mode of the three-terminal converter station is determined according to the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-terminal converter station. In addition, the power coordination control principle and power distribution implementation method of the three stations are designed respectively for the power transmission and reception modes of "one-end transmission and two-terminal reception" and "two-terminal transmission and one-terminal reception". When the power boosting and reduction functions of each station are activated, the power distribution of the three stations and the power distribution implementation method are implemented, thereby realizing the power distribution of the two receiving ends in the "one-end transmission and two-terminal reception" mode to give priority to meeting the power intake of the original two-terminal converter station inverter station, and the power distribution of the two sending ends in the "two-terminal transmission and one-terminal reception" mode to give priority to meeting the power transmission function of the newly built station, thereby improving the efficiency and accuracy of power distribution of the parallel three-terminal DC project. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a bipolar topology diagram of a two-terminal to three-terminal DC transmission system;

[0087] Figure 2 This is a flow chart of a method for controlling the stable power distribution of a two-terminal to three-terminal parallel DC line;

[0088] Figure 3 This is a block diagram of a stable control power distribution device for a two-terminal to three-terminal parallel DC line. DETAILED DESCRIPTION

[0089] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0090] The technical solution of the present invention is described in detail below with reference to the accompanying drawings. According to one embodiment of the present invention, a method for controlling power distribution in a stable manner in which a two-terminal to three-terminal parallel DC line is converted is provided. Figure 1The bipolar topology diagram of the two-terminal to three-terminal DC transmission system is shown. In the two-terminal to three-terminal parallel DC line, the newly built converter station is named Station A, the original two-terminal DC sending-end converter station is named Station B, and the original two-terminal DC receiving-end converter station is named Station C. In the method of changing the two ends into short parallel tributary lines, the newly built station is generally a rectifier station with great power transmission potential; the power sending station of the original two-terminal converter station must meet the requirements of being able to serve as both a rectifier station and an inverter station, so that it can realize both power transmission and power reception; the power receiving station of the original two-terminal converter station is still an inverter station. When the power sending station of the original two-terminal converter station serves as a rectifier station, the working mode is the "two-terminal power transmission and one-terminal power reception" mode; when the power sending station of the original two-terminal converter station serves as an inverter station, the working mode is the "one-terminal power transmission and two-terminal power reception" mode. According to this embodiment of the present invention, two control principles for the power coordination of the three stations with the stability function action under two working modes are provided:

[0091] 1. "One-end power transmission and two-end power reception" model

[0092] (1) The stabilization control function of the only sending-end converter station A is activated

[0093] When adjusting power downwards, reduce the power of station B first, and then reduce the power of station C if it is insufficient. When adjusting power upwards, increase the power of station C first, and then increase the power of station B if it is insufficient.

[0094] (2) The stabilization control function of a receiving converter station B or C is activated

[0095] Station A cooperates with the receiving converter station B (C) with the stabilization control function activated to adjust the power synchronously, while the power of the other receiving converter station C (B) remains unchanged.

[0096] 2. "Power transmission at both ends and power reception at one end" mode

[0097] (1) The stability control function of the only receiving converter station C is activated

[0098] When adjusting the power upward by power increase, the power of station A is increased first, and the power of station B is increased if the power is insufficient. When adjusting the power downward by power decrease, the power of station B is decreased first, and the power of station A is decreased if the power is insufficient.

[0099] (2) A sending end stabilization function is activated

[0100] Station C cooperates with the sending-end converter station A (B) with the stabilization control function activated to adjust the power synchronously, while the power of the other sending-end converter station B (A) remains unchanged.

[0101] The specific process of this embodiment is described below. The flow chart of this method is as follows: Figure 2 As shown, the steps include:

[0102] The bipolar power capacity and bipolar power at each end of a three-terminal DC line are calculated using the following formula:

[0103] P SA_CAP =Ud SAP1_ACT *I SAP1_LMT +Ud SAP2_ACT *I SAP2_LMT

[0104] P SB_CAP =Ud SAP1_ACT *I SBP1_LMT +Ud SAP2_ACT *I SBP2_LMT

[0105] P SC_CAP =Ud SAP1_ACT *I SC_LMT +Ud SAP2_ACT *I SCP2_LMT

[0106] P SA_DCP =Ud SAP1_ACT *I SAP1_REF +Ud SAP2_ACT *I SAP2_REF

[0107] P SB_DCP =Ud SAP1_ACT *I SBP1_REF +Ud SAP2_ACT *I SBP2_REF

[0108] P SC_DCP =Ud SAP1_ACT *I SCP1_REF +Ud SAP2_ACT *I SCP2_REF

[0109] Among them, P SA_CAP 、P SB_CAP 、P SC_CAP are the bipolar power capacities of the three-terminal converter stations A, B, and C, respectively, P SA_DCP 、P SB_DCP 、P CA_DCP are the bipolar powers of the three-terminal converter stations A, B, and C, respectively, and Ud SAP1_ACT 、Ud SAP2_ACT are the actual values ​​of DC voltage at pole 1 and pole 2 of station A, I SAP1_LMT , I SAP2_LMT , I SBP1_LMT 、、I SBP2_LMT , I SCP1_LMT , I SCP2_LMT are the current limit values ​​of pole 1 and pole 2 of the three-terminal converter stations A, B, and C, respectively. SAP1_REF , I SAP2_REF , ISBP1_REF 、、I SBP2_REF , I SCP1_REF , I SCP2_REF They are the current reference values ​​of pole 1 and pole 2 of the three-terminal converter stations A, B, and C respectively.

[0110] The power transmission and reception mode of the three-terminal converter station is determined based on the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-terminal converter stations:

[0111] If the power transmission capacity of the newly added sending-end converter station is greater than the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be one-end transmission and two-end reception.

[0112] If the power transmission capacity of the newly added sending-end converter station is less than or equal to the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be power transmission at both ends and power reception at one end.

[0113] Based on different power transmission and reception modes, the power capacities of converter stations B and C or A and B for participating in safety and stability control are calculated respectively. In addition, the power changes of converter stations A, B, and C are calculated based on the activation status of each terminal of the three-terminal converter station and the power capacities participating in safety and stability control. The specific calculation process is as follows:

[0114] 1. "One-end power transmission and two-end power reception" model

[0115] Calculate the power capacity of converter stations B and C for participating in safety and stability control, including the following calculation:

[0116] P' SB_CAP =P SA_CAP -P SC_DCP

[0117] P' SC_CAP =P SA_CAP -P SB_DCP

[0118] Among them, P' SB_CAP and P' SC_CAP They are the power capacities of converter stations B and C used for participating in stability control.

[0119] If the power boost of converter station A at the transmission end is activated, and the power boost amount received by converter station A from the station stabilization device is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0120] △P SA =△P SA_RU

[0121] △PSB =MAX{0,△P SA_RU –(P' SC_CAP –P SC_DCP )}

[0122] △P SC =MIN{△P SA_RU ,P' SC_CAP –P SC_DCP}

[0123] If the power boost of the receiving converter station B is activated, and the power boost amount received by the converter station B from the station stabilization device is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0124] △P SA =△P SB_RU

[0125] △P SB =△P SB_RU

[0126] △P SC =0

[0127] If the power boost of the receiving converter station C is activated, and the power boost amount received by the stabilization device of the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0128] △P SA =△P SC_RU

[0129] △P SB =0

[0130] △P SC =△P SC_RU

[0131] Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

[0132] If the power reduction of the converter station A at the transmission end is activated, and the power reduction amount received by the stabilization device of the converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0133] △P SA =△P SA_RB

[0134] △P SB =MIN{△P SA_RB , P SB_DCP –0.05*N DBLK_NUM}

[0135] △P SC =MAX{0,△P SA_RB –(P SB_DCP –0.05*N DBLK_NUM )}

[0136] If the power reduction of the receiving converter station B is activated, and the power reduction amount received by the converter station B from the station stabilization device is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0137] △P SA =△P SB_RB

[0138] △P SB =△P SB_RB

[0139] △P SC =0

[0140] If the power reduction of the receiving converter station C is activated, and the power reduction amount received by the converter station C from the station stabilization device is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0141] △P SA =△P SC_RB

[0142] △P SB =0

[0143] △P SC =△P SC_RB

[0144] Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

[0145] 2. "Power transmission at both ends and power reception at one end" mode

[0146] Calculate the power capacity of converter stations A and B for participating in safety and stability control, including the following calculation:

[0147] P' SA_CAP =P SC_CAP -P SB_DCP

[0148] P' SB_CAP =P SC_CAP -P SA_DCP

[0149] If the power boost of converter station A at the transmission end is activated, and the power boost amount received by converter station A from the station stabilization device is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0150] △P SA =△P SA_RU

[0151] △P SB =0

[0152] △P SC =△P SA_RU

[0153] If the power boost of converter station B at the transmission end is activated, and the power boost amount received by converter station B from the stabilization device of the station is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0154] △P SA =0

[0155] △P SB =△P SB_RU

[0156] △P SC =△P SB_RU

[0157] If the power boost of the receiving converter station C is activated, and the power boost amount received by the stabilization device of the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0158] △P SA =MIN{△P SC_RU ,P'SA_CAP –P SA_DCP}

[0159] △P SB =MAX{0,△P SC_RU –(P' SA_CAP –P SA_DCP )}

[0160] △P SC =△P SC_RU

[0161] Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

[0162] If the power reduction of the converter station A at the transmission end is activated, and the power reduction amount received by the stabilization device of the converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0163] △P SA =△P SA_RB

[0164] △P SB =0

[0165] △P SC =△P SA_RB

[0166] If the power reduction of the converter station B at the transmission end is activated, and the power reduction amount received by the converter station B from the station stabilization device is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0167] △P SA =0

[0168] △P SB =△P SB_RU

[0169] △P SC =△P SB_RU

[0170] If the power reduction of the receiving converter station C is activated, and the power reduction amount received by the converter station C from the station stabilization device is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula:

[0171] △P SA =MAX{0,△P SC_RB –(P SB_DCP –0.05*N DBLK_NUM )}

[0172] △P SB =MIN{△P SC_RB ,P SB_DCP –0.05*N DBLK_NUM}

[0173] △P SC =△P SC_RU

[0174] Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

[0175] According to another embodiment of the present invention, a stable control power distribution device for a two-terminal to three-terminal parallel DC line is provided. The block diagram of the device is as follows: Figure 3 As shown, it includes a power calculation module, a power transmission and reception mode determination module, and a power distribution module.

[0176] Power calculation module, calculates the bipolar power capacity and bipolar power of each end in the three-terminal DC line;

[0177] The power transmission and reception mode determination module determines the power transmission and reception mode of the three-terminal converter station based on the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-end converter stations;

[0178] The power distribution module calculates the power capacity of converter stations B and C or A and B for participating in stability control under different power transmission and reception modes; and calculates the power change of the three-terminal converter stations A, B, and C based on the activation status of each end of the three-terminal converter station and the power capacity participating in stability control.

[0179] The functional implementation process and steps of each module in the device are the same as those of the method provided in the first embodiment of the present invention, and will not be repeated here.

[0180] In summary, the present invention relates to a method and device for stable power distribution control of a two-terminal to three-terminal parallel DC line. In the process of stable power distribution control of the two-terminal to three-terminal parallel DC line, the power transmission and reception mode of the three-terminal converter station is determined according to the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-terminal converter station. In addition, the power coordination control principle of the three stations and the power distribution implementation method are designed respectively for the power transmission and reception modes of "one-end transmission and two-terminal reception" and "two-terminal transmission and one-terminal reception". When the power boosting and reducing functions of each station are activated, the power distribution of the three stations and the power distribution implementation method are implemented. In this way, the power distribution of the two receiving ends in the "one-end transmission and two-terminal reception" mode prioritizes the power intake of the original two-terminal converter station inverter station, and the power distribution of the two sending ends in the "two-terminal transmission and one-terminal reception" mode prioritizes the power transmission of the newly built station, thereby improving the efficiency and accuracy of power distribution of the parallel three-terminal DC project.

[0181] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for stable power distribution control of a two-terminal to three-terminal parallel DC line, characterized in that: Including steps: Calculate the bipolar power capacity and bipolar power at terminals A, B, and C in a three-terminal DC line; Determine the power transmission and reception mode of the three-terminal converter station based on the power transmission capacity of the newly added sending-end converter station A and the power absorption capacity of the existing two-end converter stations B and C; the power transmission and reception mode includes a one-end power transmission and two-end power reception mode and a two-end power transmission and one-end power reception mode; In the one-end power transmission and two-end power reception mode, there are two situations: the first one: the stabilization control function of the only sending-end converter station A is activated. When the power is reduced, the power of converter station B is reduced first, and the power of converter station C is reduced for the insufficient part; when the power is increased, the power of converter station C is increased first, and the power of converter station B is increased for the insufficient part; the second one: the stabilization control function of a certain receiving-end converter station B or C is activated, and converter station A cooperates with the receiving-end converter station B or C with the activated stabilization control function to adjust the power synchronously, and the power of the other receiving-end converter station C or B remains unchanged; The two-end power transmission and one-end power receiving mode includes two situations: the first is that the stabilization control function of the only receiving-end converter station C is activated. When the power is increased and adjusted upward, the power of converter station A is increased first, and the power of converter station B is increased if the power is insufficient; when the power is reduced and adjusted downward, the power of converter station B is reduced first, and the power of converter station A is reduced if the power is insufficient; the second is that the stabilization control function of one sending-end is activated, and converter station C cooperates with the sending-end converter station A or station B with the activated stabilization control function to adjust the power synchronously, while the other sending-end converter station B or station A remains unchanged; Based on the power transmission and reception mode: Calculate the power capacity of converter stations B and C or A and B for participating in safety and stability control; The power changes of the three-terminal converter stations A, B, and C are calculated based on the activation status of each terminal of the three-terminal converter station and the power capacity participating in the stability control.

2. The method according to claim 1, characterized in that The calculating of the bipolar power capacity and bipolar power of each terminal in the three-terminal DC line includes: P SA_CAP =Out SAP1_ACT *IN SAP1_LMT +Out SAP2_ACT *IN SAP2_LMT P SB_CAP =Out SAP1_ACT *IN SBP1_LMT +Out SAP2_ACT *IN SBP2_LMT P SC_CAP =Out SAP1_ACT *IN SCP1_LMT +Out SAP2_ACT *IN SCP2_LMT P SA_DCP =Out SAP1_ACT *IN SAP1_REF +Out SAP2_ACT *IN SAP2_REF P SB_DCP =Out SAP1_ACT *IN SBP1_REF +Out SAP2_ACT *IN SBP2_REF P SC_DCP =Out SAP1_ACT *IN SCP1_REF +Out SAP2_ACT *IN SCP2_REF Among them, P SA_CAP 、P SB_CAP 、P SC_CAP are the bipolar power capacities of the three-terminal converter stations A, B, and C, respectively, P SA_DCP 、P SB_DCP 、P CA_DCP are the bipolar powers of the three-terminal converter stations A, B, and C, respectively, and Ud SAP1_ACT 、Ud SAP2_ACT are the actual values ​​of DC voltage at the two poles of converter station A, I SAP1_LMT , I SAP2_LMT , I SBP1_LMT , I SBP2_LMT , I SCP1_LMT , I SCP2_LMT are the current limit values ​​of the three-terminal converter station A, B, and C, respectively. SAP1_REF , I SAP2_REF , I SBP1_REF , I SBP2_REF , I SCP1_REF , I SCP2_REF They are the current reference values ​​of the two poles A, B and C of the three-terminal converter station respectively.

3. The method according to claim 2, characterized in that The power transmission and reception mode of the three-terminal converter station is determined based on the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-terminal converter stations, including: If the power transmission capacity of the newly added sending-end converter station is greater than the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be one-end transmission and two-end reception. If the power transmission capacity of the newly added sending-end converter station is less than or equal to the power absorption capacity of the original two-end converter station, the power transmission and reception mode of the three-end converter station will be power transmission at both ends and power reception at one end.

4. The method according to claim 3, characterized in that In the mode of power transmission at one end and power reception at both ends, the power capacity of converter stations B and C used for participating in safety and stability control is calculated by the following formula: P' SB_CAP =P SA_CAP -P SC_DCP P' SC_CAP =P SA_CAP -P SB_DCP Among them, P' SB_CAP and P' SC_CAP They are the power capacities of converter stations B and C used for participating in stability control.

5. The method according to claim 4, characterized in that In the mode of power transmission at one end and power reception at both ends, if the power boost of converter station A at the transmission end is activated and the power boost amount received by converter station A is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SA_RU △P SB =MAX{0,△P SA_RU –(P' SC_CAP –P SC_DCP )} △P SC =MIN{△P SA_RU 'P' SC_CAP –P SC_DCP } If the power boost of the receiving end converter station B is activated, and the power boost amount of converter station B to be boosted is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SB_RU △P SB =△P SB_RU △P SC ＝0 If the power boost at the receiving converter station C is activated, and the power boost received by the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SC_RU △P SB ＝0 △P SC =△P SC_RU Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

6. The method according to claim 4, characterized in that In the mode of power transmission at one end and power reception at both ends, if the power reduction of converter station A at the transmission end is activated and the power reduction amount received by converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SA_RB △P SB =MIN{△P SA_RB ,P SB_DCP –0.05*N DBLK_NUM } △P SC =MAX{0,△P SA_RB –(P SB_DCP –0.05*N DBLK_NUM )} If the power reduction at the receiving-end converter station B is activated, and the power reduction amount received by the converter station B is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SB_RB △P SB =△P SB_RB △P SC ＝0 If the power reduction function of the receiving converter station C is activated, and the power reduction amount received by the converter station C is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SC_RB △P SB ＝0 △P SC =△P SC_RB Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

7. The method according to claim 3, characterized in that In the mode of power transmission at both ends and power reception at one end, the power capacity of converter stations A and B used for participating in safety and stability control is calculated by the following formula: P' SA_CAP =P SC_CAP -P SB_DCP P' SB_CAP =P SC_CAP -P SA_DCP 。 8. The method according to claim 6, characterized in that In the mode of power transmission at both ends and power reception at one end, if the power boost of converter station A at the transmission end is activated and the power boost received by converter station A is △P SA_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SA_RU △P SB ＝0 △P SC =△P SA_RU If the power boost at the transmission-end converter station B is activated, and the power boost received by converter station B is △P SB_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA ＝0 △P SB =△P SB_RU △P SC =△P SB_RU If the power boost at the receiving converter station C is activated, and the power boost received by the converter station C is △P SC_RU , then the power increase change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =MIN{△P SC_RU 'P' SA_CAP –P SA_DCP } △P SB =MAX{0,△P SC_RU –(P' SA_CAP –P SA_DCP )} △P SC =△P SC_RU Among them, MAX{} is the maximum value function, and MIN{} is the minimum value function.

9. The method according to claim 6, characterized in that In the mode of power transmission at both ends and power reception at one end, if the power reduction at the converter station A at the transmission end is activated and the power reduction amount received by the converter station A is △P SA_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =△P SA_RB △P SB ＝0 △P SC =△P SA_RB If the power reduction function of the converter station B at the transmission end is activated, and the power reduction amount received by the converter station B is △P SB_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA ＝0 △P SB =△P SB_RU △P SC =△P SB_RU If the power reduction function of the receiving converter station C is activated, and the power reduction amount received by the converter station C is △P SC_RB , then the power reduction change △P of converter stations A, B, and C is SA , △P SB and △P SC Calculated by the following formula: △P SA =MAX{0,△P SC_RB –(P SB_DCP –0.05*N DBLK_NUM )} △P SB =MIN{△P SC_RB ,P SB_DCP –0.05*N DBLK_NUM } △P SC =△P SC_RU Among them, MAX{} is the maximum value function, MIN{} is the minimum value function, N DBLK_NUM The number of converter stations unlocked for this station.

10. A stable control power distribution device for a two-terminal to three-terminal parallel DC line, characterized in that: It includes a power calculation module, a power transmission and reception mode determination module, and a power distribution module; wherein, The power calculation module calculates the bipolar power capacity and bipolar power of each terminal in the three-terminal DC line; The power transmission and reception mode determination module determines the power transmission and reception mode of the three-terminal converter station based on the power transmission capacity of the newly added sending-end converter station and the power absorption capacity of the original two-end converter station; the power transmission and reception mode includes a one-end power transmission and two-end power reception mode and a two-end power transmission and one-end power reception mode; In the one-end power transmission and two-end power reception mode, there are two situations: the first one: the stabilization control function of the only sending-end converter station A is activated. When the power is reduced, the power of converter station B is reduced first, and the power of converter station C is reduced for the insufficient part; when the power is increased, the power of converter station C is increased first, and the power of converter station B is increased for the insufficient part; the second one: the stabilization control function of a certain receiving-end converter station B or C is activated, and converter station A cooperates with the receiving-end converter station B or C with the activated stabilization control function to adjust the power synchronously, and the power of the other receiving-end converter station C or B remains unchanged; The two-end power transmission and one-end power receiving mode includes two situations: the first one: the stabilization control function of the only receiving-end converter station C is activated. When the power is increased and adjusted upward, the power of converter station A is increased first, and the power of converter station B is increased if the power is insufficient; when the power is reduced and adjusted downward, the power of converter station B is reduced first, and the power of converter station A is reduced if the power is insufficient; the second one: the stabilization control function of one sending-end is activated, and converter station C cooperates with the sending-end converter station A or station B with the activated stabilization control function to adjust the power synchronously, and the power of the other sending-end converter station B or station A remains unchanged; The power distribution module calculates the power capacity of converter stations B and C or A and B for participating in safety and stability control under different power transmission and reception modes; and calculates the power change of the three-terminal converter stations A, B, and C based on the activation status of each end of the three-terminal converter station and the power capacity participating in safety and stability control.

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