Power conversion method, device and equipment of four-terminal new energy direct current power transmission system

Abstract

The invention discloses a power conversion method, device and equipment for a four-terminal new energy direct current power transmission system, and the method comprises the steps: selecting a corresponding locking mode according to different stations where a fault is located under the working condition that bipolar operation of four converter stations of the four-terminal new energy direct current power transmission system occurs if a certain converter station is subjected to single-valve, single-pole or single-station fault locking; and selecting a corresponding power conversion path according to the control mode before locking. According to the four-end new energy direct current transmission system, inter-valve-group conversion and / or inter-electrode conversion and / or inter-station conversion of power can be achieved, the stability of the four-end new energy direct current transmission system is improved, meanwhile, the proportion of clean energy output by a new energy station is guaranteed to the maximum extent, and high engineering availability is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of direct current transmission, and specifically relates to a power transfer method, device and equipment for a four-terminal new energy direct current transmission system. Background Art

[0002] When new energy power generation units replace traditional generator sets or synchronous generators, the mechanical inertia and short-circuit capacity of the system will decrease, which means that new energy units provide almost no short-circuit current and their voltage stability capability is relatively weakened. Especially when new energy is connected through the AC grid or conventional UHV DC lines, due to the limited anti-disturbance and support capabilities of power electronic equipment, as the proportion of such equipment in the power system increases, the low inertia characteristics of the system become more significant, resulting in reduced overall stability and insufficient dynamic reactive power compensation capabilities. In the case of DC transmission lockout, the excess capacitive reactive power generated by the filter and new energy devices may cause the bus voltage of the converter station to increase instantaneously, that is, transient overvoltage phenomenon, which usually requires the additional deployment of a large number of phase regulators to deal with. These problems constitute key obstacles to the development of the new energy industry.

[0003] In order to effectively connect the new energy production bases in the west and north of my country, the hydropower hubs in the southwest, and the high-load power consumption centers in the east and central regions, and further optimize the energy distribution across the country, it is necessary to promote the development of cutting-edge transmission technologies and network architectures such as UHV DC transmission, flexible DC transmission, and DC grids. In particular, building a new energy transmission system with large-scale wind and solar power bases as the core, supplemented by surrounding thermal power generation and hydropower generation facilities as stable support, and with UHV flexible DC transmission systems as the transmission backbone is regarded as one of the ideal strategies to solve the problem of large-scale grid connection and long-distance transmission of new energy. This system can not only make full use of the natural advantages of wind and solar complementarity, but also use the flexibility and stability of traditional energy to achieve efficient and safe energy transmission through advanced UHV flexible DC technology, thereby meeting the growing demand for clean energy in the eastern and central regions and promoting the green transformation and sustainable development of the national energy structure.

[0004] The characteristics of renewable energy power generation are unstable output, significant randomness and volatility. If it is directly connected to the power grid, it may cause a great impact on the power grid, especially the stability problem under transient operating conditions. Therefore, an effective solution is to adopt an isolated operation mode to access the renewable energy unit, that is, to operate independently in the local power grid first, and then connect to the grid in time, so as to reduce the immediate impact on the main power grid. In addition, in order to enhance the reliability of the renewable energy base, traditional power sources such as hydropower or thermal power with corresponding capacity are usually equipped near the base. After these stable power sources are connected to the AC power grid, they can significantly increase the short-circuit current level, thereby enhancing the overall strength of the power grid. The increase in the strength of the power grid can not only improve the transmission capacity, but also help improve the stability of the power grid and ensure the safe operation of the power system. In the design of the DC transmission system, considering the high efficiency and economy of DC transmission, multiple landing points are often set up at the receiving end to distribute power more evenly, improve the utilization rate of DC transmission lines, and better meet the power needs of different regions. This multi-point access method plays an important role in balancing the load of the power grid and optimizing resource allocation.

[0005] The parallel four-terminal flexible DC transmission system is a network layout widely used in the multi-terminal flexible DC transmission architecture. When a single valve group, single pole or single converter station in the system encounters a lockout fault, how to effectively transfer power, the so-called "power transfer", becomes a crucial technical issue. This process aims to ensure that the power output of the new energy station is maintained as much as possible without affecting the normal operation of the non-faulty stations. At present, how to achieve the optimal power transfer strategy while ensuring system stability and efficiency is still in the in-depth research stage. Summary of the invention

[0006] The purpose of the present invention is to provide a power transfer method, device and equipment for a four-terminal new energy direct current transmission system, aiming to improve the stability of the four-terminal new energy direct current transmission system, while maximizing the proportion of clean energy output from the new energy station.

[0007] In order to achieve the above object, the solution of the present invention is:

[0008] A power transfer method for a four-terminal new energy direct current transmission system, the four-terminal new energy direct current transmission system comprising four converter stations, the four converter stations comprising two rectifier stations and two inverter stations, the converter station connected to new energy in the two rectifier stations being called the first converter station, and the converter station connected to non-new energy being called the second converter station; the two inverter stations being called the third converter station and the fourth converter station respectively; under the condition that the four converter stations of the four-terminal new energy direct current transmission system are bipolarly operated, if a converter station is locked due to a single valve, single pole or single station fault, a corresponding locking mode is selected according to the different stations where the fault is located, and a corresponding power transfer path is selected according to the control mode before locking;

[0009] Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode;

[0010] Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

[0011] Among them, the blocking mode is selected according to the different stations where the fault is located, and the power transfer path is selected for the first control mode according to the control mode before blocking, including:

[0012] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the lost power is not transferred; the second pole power of the four converter stations remains unchanged;

[0013] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the first pole of the second converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the power of the second poles of the four converter stations remains unchanged;

[0014] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged;

[0015] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power limit is reached; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the power of the second poles of the four converter stations remains unchanged;

[0016] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit is reached; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations will remain unchanged.

[0017] Among them, the blocking mode is selected according to the different stations where the fault is located, and the power transfer path is selected for the second control mode according to the control mode before blocking, including:

[0018] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the sum of the power lost at the first and second converter stations is transferred to another valve group at the first pole of the first converter station until its power upper limit, and the remaining power is transferred to another valve group at the first pole of the second converter station until its power upper limit; the power lost at the third converter station is transferred to another valve group at the first pole of the third converter station until its power upper limit; the power lost at the fourth converter station is transferred to another valve group at the first pole of the fourth converter station until its power upper limit; the power of the second poles of the four converter stations remains unchanged;

[0019] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to the single-pole current control mode, and the lost power is transferred to the first pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the second pole power of the four converter stations remains unchanged;

[0020] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged;

[0021] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit is reached; the sum of the power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the power of the second poles of the four converter stations remains unchanged;

[0022] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked and switched to the single pole current control mode; the lost power will be transferred to the first pole of the third converter station until its power upper limit is reached; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the second pole power of the four converter stations will remain unchanged.

[0023] Among them, the blocking mode is selected according to the different stations where the fault is located, and the power transfer path is selected for the third control mode according to the control mode before blocking, including:

[0024] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the total power lost by the first and second converter stations is first transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the second converter station until its power upper limit; the power lost by the third converter station is transferred to the second pole of the third converter station until its power upper limit; the power lost by the fourth converter station is transferred to the second pole of the fourth converter station until its power upper limit;

[0025] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0026] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0027] If a single valve or single pole failure occurs at the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0028] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit, and the remaining power will be transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power will be further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations will be proportionally increased to the same level as the total power of the second poles of the first and second converter stations.

[0029] Among them, the blocking mode is selected according to the different stations where the fault is located, and the power transfer path is selected for the fourth control mode according to the control mode before blocking, including:

[0030] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the total power lost by the first and second converter stations is first transferred to another valve group at the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and further the remaining power is transferred to the second converter station until its power upper limit; the power lost by the third converter station is equally transferred to another valve group and the second pole of the first pole of the third converter station until its power upper limit; the power lost by the fourth converter station is equally transferred to another valve group and the second pole of the first pole of the fourth converter station until its power upper limit;

[0031] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to the single-pole current control mode; the lost power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the first pole of the second converter station until its power upper limit, and further the remaining power is transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0032] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0033] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0034] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit, the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power is further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations.

[0035] Among them, it also includes:

[0036] When a bipolar fault occurs in the first converter station, the bipolar of the first converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the second converter station until its power upper limit is reached; the sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the second converter station;

[0037] When a bipolar fault occurs in the second converter station, the bipolar of the second converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the first converter station until its power upper limit is reached; the sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the first converter station;

[0038] When a bipolar fault occurs in the third converter station, the bipolar of the third converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the fourth converter station until its power upper limit is reached; the sum of the bipolar powers of the first and second converter stations is proportionally reduced to the same power level as the bipolar power of the fourth converter station;

[0039] When a bipolar fault occurs in the fourth converter station, the bipolar of the fourth converter station is locked and switched to the unipolar current control mode. The power lost in each pole is transferred to the corresponding pole of the third converter station until its power upper limit is reached; the total power of the bipolar of the first and second converter stations is proportionally reduced to the same power level as the bipolar of the third converter station.

[0040] A power transfer device for a four-terminal new energy direct current power transmission system, the four-terminal new energy direct current power transmission system comprises four converter stations, the four converter stations comprise two rectifier stations and two inverter stations, of the two rectifier stations, the converter station connected to the new energy is called the first converter station, and the converter station connected to the non-new energy is called the second converter station; the two inverter stations are respectively called the third converter station and the fourth converter station; including,

[0041] A fault lockout judgment module is configured to judge whether a single-valve, single-pole or single-station fault lockout occurs in a converter station under the condition that the bipolar of the four converter stations of the four-terminal new energy direct current transmission system are all in operation; and

[0042] The power transfer control module is configured to select a corresponding blocking mode according to different stations where the fault is located, and select a corresponding power transfer path according to the control mode before blocking;

[0043] Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode;

[0044] Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

[0045] The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the first control mode according to the control mode before blocking, including:

[0046] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the lost power is not transferred; the second pole power of the four converter stations remains unchanged;

[0047] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the first pole of the second converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the power of the second poles of the four converter stations remains unchanged;

[0048] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged;

[0049] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power limit is reached; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the power of the second poles of the four converter stations remains unchanged;

[0050] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit is reached; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations will remain unchanged.

[0051] The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the second control mode according to the control mode before blocking, including:

[0052] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the sum of the power lost at the first and second converter stations is transferred to another valve group at the first pole of the first converter station until its power upper limit, and the remaining power is transferred to another valve group at the first pole of the second converter station until its power upper limit; the power lost at the third converter station is transferred to another valve group at the first pole of the third converter station until its power upper limit; the power lost at the fourth converter station is transferred to another valve group at the first pole of the fourth converter station until its power upper limit; the power of the second poles of the four converter stations remains unchanged;

[0053] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to the single-pole current control mode, and the lost power is transferred to the first pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the second pole power of the four converter stations remains unchanged;

[0054] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged;

[0055] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit is reached; the sum of the power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the power of the second poles of the four converter stations remains unchanged;

[0056] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked and switched to the single pole current control mode; the lost power will be transferred to the first pole of the third converter station until its power upper limit is reached; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the second pole power of the four converter stations will remain unchanged.

[0057] The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the third control mode according to the control mode before blocking, including:

[0058] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the total power lost by the first and second converter stations is first transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the second converter station until its power upper limit; the power lost by the third converter station is transferred to the second pole of the third converter station until its power upper limit; the power lost by the fourth converter station is transferred to the second pole of the fourth converter station until its power upper limit;

[0059] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0060] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0061] If a single valve or single pole failure occurs at the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0062] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit, and the remaining power will be transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power will be further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations will be proportionally increased to the same level as the total power of the second poles of the first and second converter stations.

[0063] The power transfer control module selects a locking mode according to different stations where the fault is located, and selects a power transfer path for the fourth control mode according to the control mode before locking, including:

[0064] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the total power lost by the first and second converter stations is first transferred to another valve group at the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and further the remaining power is transferred to the second converter station until its power upper limit; the power lost by the third converter station is equally transferred to another valve group and the second pole of the first pole of the third converter station until its power upper limit; the power lost by the fourth converter station is equally transferred to another valve group and the second pole of the first pole of the fourth converter station until its power upper limit;

[0065] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to the single-pole current control mode; the lost power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the first pole of the second converter station until its power upper limit, and further the remaining power is transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0066] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0067] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0068] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit, the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power is further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations.

[0069] Wherein, the power transfer control module also includes:

[0070] When a bipolar fault occurs in the first converter station, the bipolar of the first converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the second converter station until its power upper limit is reached; the sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the second converter station;

[0071] When a bipolar fault occurs in the second converter station, the bipolar of the second converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the first converter station until its power upper limit is reached; the sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the first converter station;

[0072] When a bipolar fault occurs in the third converter station, the bipolar of the third converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the fourth converter station until its power upper limit is reached; the sum of the bipolar powers of the first and second converter stations is proportionally reduced to the same power level as the bipolar power of the fourth converter station;

[0073] When a bipolar fault occurs in the fourth converter station, the bipolar of the fourth converter station is locked and switched to the unipolar current control mode. The power lost in each pole is transferred to the corresponding pole of the third converter station until its power upper limit is reached; the total power of the bipolar of the first and second converter stations is proportionally reduced to the same power level as the bipolar of the third converter station.

[0074] A power transfer device for a four-terminal new energy direct current transmission system comprises a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the power transfer method for the four-terminal new energy direct current transmission system as described above are implemented.

[0075] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the steps of the power transfer method of the four-terminal new energy direct current transmission system as described above are implemented.

[0076] After adopting the above scheme, compared with the prior art, under the working condition that all the bipolars of the four converter stations are operating, when a single valve, single pole or single station fault occurs in a converter station and is locked, the present invention selects the corresponding locking mode according to the different stations where the fault is located, and selects the corresponding power transfer path according to the control mode before locking, so as to realize the power transfer between valve groups and / or between poles and / or between stations, thereby improving the stability of the four-terminal new energy DC transmission system, and at the same time maximizing the proportion of clean energy output of the new energy station, and having high engineering availability. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 It is a schematic diagram of a topological structure of a four-terminal new energy direct current transmission system provided by an embodiment of the present invention;

[0078] Figure 2 This is a schematic diagram of the topological structure of a typical UHV single-station bipolar four-valve group provided in an embodiment of the present invention;

[0079] Figure 3 It is a schematic flow chart of a power transfer method for a four-terminal new energy direct current transmission system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0080] The present invention provides a power transfer method for a four-terminal new energy direct current power transmission system, wherein the four-terminal new energy direct current power transmission system comprises four converter stations, wherein the four converter stations comprise two rectifier stations and two inverter stations, wherein the converter station connected to the new energy is called the first converter station, and the converter station connected to the non-new energy is called the second converter station; the two inverter stations are respectively called the third converter station and the fourth converter station; under the condition that the four converter stations of the four-terminal new energy direct current power transmission system are bipolarly operated, if a converter station is locked due to a single valve, single pole or single station fault, a corresponding locking mode is selected according to the different stations where the fault is located, and a corresponding power transfer path is selected according to the control mode before locking;

[0081] Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode;

[0082] Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

[0083] As a preferred embodiment of the present invention, the four-terminal new energy direct current transmission system comprises four converter stations, such as Figure 1 As shown, they are converter station 1, converter station 2, converter station 3 and converter station 4 respectively; Figure 2 As shown, a single station is composed of two poles, pole 1 and pole 2, connected in series. Pole 1 is connected to the DC transmission system through the pole 1 DC line, and pole 2 is connected to the DC transmission system through the pole 2 DC line. The midpoint of the bipolar is grounded through the converter station grounding point. Each pole is composed of a high-end converter valve group and a low-end converter valve group in series. The four converter valve groups of a single station are all connected to the same power grid or power supply. Under the condition that the bipolars of the four converter stations are all operating, if a converter station is locked due to a single valve, single pole or single station fault, the power transfer method selects a corresponding locking mode according to the different stations where the fault is located, and further selects a corresponding power transfer path according to the control mode before locking, so as to realize power transfer between valve groups and / or between poles and / or between stations, as shown in FIG. Figure 3 shown.

[0084] Furthermore, the four converter stations include two rectifier stations and two inverter stations. The two rectifier stations are converter station 1 and converter station 2, and the two stations are connected in parallel through DC line 1; the two inverter stations are converter station 3 and converter station 4, and the two stations are connected in parallel through DC line 3; the two rectifier stations and the two inverter stations are connected through DC line 2. Among the two rectifier stations, the converter station to which the new energy is connected is called the first converter station, such as Figure 1The converter station 1 in the figure is connected to the new energy base; the converter station that is not connected to the new energy base is called the second converter station, such as Figure 1 The converter station 1 in the diagram is connected to the AC power source composed of the thermal power and hydropower plant and the grid 1 in parallel; the other two inverter stations are called the third converter station and the fourth converter station, such as Figure 1 The converter station 3 in the example is connected to the grid 2, and the converter station 4 is connected to the grid 3. The pole where the fault is locked is called the first pole, and the pole where the fault is not locked is called the second pole.

[0085] Furthermore, the control modes include four types: in a first control mode, the first pole and the second pole are both unipolar current control modes; in a second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; in a third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; in a fourth control mode, the first pole and the second pole are both bipolar power control modes.

[0086] Furthermore, if the first control mode is used before locking, the locking method and the power transfer path are specifically as follows;

[0087] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station will be locked, and the corresponding valve groups of the other three converter stations will be locked; the lost power will not be transferred; the second pole power of the four converter stations will remain unchanged;

[0088] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is directly blocked; the lost power is transferred to the first pole of the second converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the power of the second poles of the four converter stations remains unchanged;

[0089] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is directly locked; the lost power is transferred to the first pole of the first converter station until its power limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged;

[0090] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station will be directly locked; the lost power will be transferred to the first pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the fourth converter station, and the power of the second converter station will be reduced first until its power lower limit, and the power of the first converter station will be further reduced for the insufficient part; the power of the second poles of the four converter stations will remain unchanged;

[0091] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be directly locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station, and the power of the second converter station will be reduced first until its power lower limit, and the power of the first converter station will be further reduced to make up for the shortfall; the power of the second poles of the four converter stations remains unchanged.

[0092] Furthermore, if the second control mode is used before locking, the locking method and the power transfer path are specifically as follows;

[0093] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the other three converter stations are locked; the total power lost by the first and second converter stations is preferentially transferred to another valve group at the first pole of the first converter station until its power upper limit, and the remaining power is transferred to another valve group at the first pole of the second converter station until its power upper limit; the power lost by the third converter station is transferred to another valve group at the first pole of the third converter station until its power upper limit; the power lost by the fourth converter station is transferred to another valve group at the first pole of the fourth converter station until its power upper limit; the power of the second poles of the four converter stations remains unchanged;

[0094] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is directly locked and switched to the single-pole current control mode, and the lost power is transferred to the first pole of the second converter station until its power upper limit is reached; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station; the second pole power of the four converter stations remains unchanged;

[0095] If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is directly locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the second pole power of the four converter stations remains unchanged;

[0096] If a single valve or single pole fault occurs in the first pole of the third converter station, the first pole of the third converter station is directly locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit; the sum of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station, and the power of the second converter station is preferentially reduced until its power lower limit, and the power of the first converter station is further reduced for the insufficient part; the second pole power of the four converter stations remains unchanged;

[0097] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be directly locked and switched to the single pole current control mode; the lost power will be transferred to the first pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station, and the power of the second converter station will be reduced first until its power lower limit, and the power of the first converter station will be further reduced by the insufficient part; the power of the second poles of the four converter stations remains unchanged.

[0098] Furthermore, if the third control mode is used before locking, the locking method and the power transfer path are specifically as follows;

[0099] If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the other three converter stations are locked; the total power lost by the first and second converter stations is preferentially transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the second converter station until its power upper limit; the power lost by the third converter station is transferred to the second pole of the third converter station until its power upper limit; the power lost by the fourth converter station is transferred to the second pole of the fourth converter station until its power upper limit;

[0100] If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is directly locked; the lost power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0101] If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is directly locked; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0102] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is directly locked; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station, and the power of the second converter station is preferentially reduced to its power lower limit, and the power of the first converter station is further reduced for the insufficient part; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations, and the power of the first converter station is preferentially increased to its power upper limit, and the power of the second converter station is further increased for the insufficient part;

[0103] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station will be directly locked; the lost power will be transferred to the first pole of the third converter station until its power upper limit, and the remaining power will be transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power will be further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations will be proportionally reduced to the same power level as the first pole of the third converter station, and the power of the second converter station will be reduced first until its power lower limit, and the power of the first converter station will be further reduced for the insufficient part; the total power of the second poles of the third and fourth converter stations will be proportionally increased to the same level as the total power of the second poles of the first and second converter stations, and the power of the first converter station will be increased first until its power upper limit, and the power of the second converter station will be further increased for the insufficient part.

[0104] Furthermore, if the fourth control mode is used before locking, the locking mode and the power transfer path are specifically as follows;

[0105] If a single valve failure occurs in the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the other three converter stations are locked; the total power lost by the first and second converter stations is preferentially transferred to another valve group of the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second converter station until its power upper limit; the power lost by the third converter station is equally transferred to another valve group and the second pole of the first pole of the third converter station until its power upper limit; the power lost by the fourth converter station is equally transferred to another valve group and the second pole of the first pole of the fourth converter station until its power upper limit;

[0106] If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is directly locked and switched to the single-pole current control mode; the lost power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0107] If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is directly locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; the total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations;

[0108] If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is directly locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and the remaining power is further transferred to the second pole of the fourth converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station, and the power of the second converter station is preferentially reduced to its power lower limit, and the power of the first converter station is further reduced for the insufficient part; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations, and the power of the first converter station is preferentially increased to its power upper limit, and the power of the second converter station is further increased for the insufficient part;

[0109] If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is directly locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit, and the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and the remaining power is further transferred to the second pole of the third converter station until its power upper limit; the total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station, and the power of the second converter station is preferentially reduced to its power lower limit, and the power of the first converter station is further reduced for the insufficient part; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the total power of the second poles of the first and second converter stations, and the power of the first converter station is preferentially increased to its power upper limit, and the power of the second converter station is further increased for the insufficient part.

[0110] Further,

[0111] When a bipolar fault occurs in the first converter station, the bipolar of the first converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the second converter station until its power limit is reached. The sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the second converter station;

[0112] When a bipolar fault occurs in the second converter station, the bipolar of the second converter station is locked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the first converter station until its power limit is reached. The sum of the bipolar powers of the third and fourth converter stations is proportionally reduced to the same power level as the bipolar power of the first converter station;

[0113] When a bipolar fault occurs in the third converter station, the bipolar of the third converter station is locked and switched to the unipolar current control mode. The power lost in each pole is transferred to the corresponding pole of the fourth converter station until its power upper limit. The sum of the bipolar powers of the first and second converter stations is proportionally reduced to the same power level as the bipolar power of the fourth converter station. The power of the second converter station is preferentially reduced until its power lower limit. The shortfall is then used to reduce the power of the first converter station.

[0114] When a bipolar fault occurs in the fourth converter station, the bipolar of the fourth converter station is locked and switched to the unipolar current control mode. The power loss of each pole is transferred to the corresponding pole of the third converter station until its power upper limit. The sum of the bipolar powers of the first and second converter stations is proportionally reduced to the same power level as the bipolar power of the third converter station. The power of the second converter station is reduced first until its power lower limit, and the shortfall is further reduced by the power of the first converter station.

[0115] The embodiment of the present invention further provides a power transfer device of a four-terminal new energy direct current transmission system, wherein the four-terminal new energy direct current transmission system comprises four converter stations, wherein the four converter stations comprise two rectifier stations and two inverter stations, wherein the converter station connected to the new energy is called the first converter station, and the converter station connected to the non-new energy is called the second converter station; the two inverter stations are respectively called the third converter station and the fourth converter station; and the power transfer device comprises:

[0116] A fault lockout judgment module is configured to judge whether a single-valve, single-pole or single-station fault lockout occurs in a converter station under the condition that the bipolar of the four converter stations of the four-terminal new energy direct current transmission system are all in operation; and

[0117] The power transfer control module is configured to select a corresponding blocking mode according to different stations where the fault is located, and select a corresponding power transfer path according to the control mode before blocking;

[0118] Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode;

[0119] Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

[0120] An embodiment of the present invention also provides another power transfer device for a four-terminal new energy direct current transmission system, comprising a processor and a memory configured to store a computer program that can run on the processor; wherein, when the processor is configured to run the computer program, the method steps in the aforementioned embodiment are executed.

[0121] In practical applications, the processor includes a field programmable gate array (FPGA), and the processor may be a central processing unit (CPU) or a digital signal processor (DSP). It is understandable that for different devices, the electronic device used to implement the function of the processor may be other, and the embodiment of the present invention does not specifically limit it.

[0122] The above-mentioned memory can be a volatile memory (volatile memory), such as a random access memory (RAM); or a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory, a hard disk (HDD) or a solid-state drive (SSD); or a combination of the above-mentioned types of memory, and provide instructions and data to the processor.

[0123] In an exemplary embodiment, an embodiment of the present invention further provides a computer-readable storage medium for storing a computer program.

[0124] Optionally, the computer-readable storage medium can be applied to any one of the methods in the embodiments of the present invention, and the computer program enables the computer to execute the corresponding processes implemented by the processor in each method in the embodiments of the present invention. For the sake of brevity, they are not described here.

[0125] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0126] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0127] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0128] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0129] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0130] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0131] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A power transfer method for a four-terminal new energy direct current transmission system, wherein the four-terminal new energy direct current transmission system comprises four converter stations, wherein the four converter stations comprise two rectifier stations and two inverter stations, wherein the converter station connected to the new energy is called the first converter station, and the converter station connected to the non-new energy is called the second converter station; the two inverter stations are respectively called the third converter station and the fourth converter station; wherein: Under the condition that the bipolar of the four converter stations of the four-terminal new energy direct current transmission system are all in operation, if a converter station is locked due to a single valve, single pole or single station fault, a corresponding locking mode is selected according to the different stations where the fault is located, and a corresponding power transfer path is selected according to the control mode before locking; Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode; Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

2. The power transfer method of the four-terminal new energy direct current transmission system according to claim 1, characterized in that: Select the blocking mode according to the different stations where the fault is located, and select the power transfer path for the first control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the lost power is not transferred; the second pole power of the four converter stations remains unchanged; If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the first pole of the second converter station until its power upper limit; The sum of the first pole power of the third and fourth converter stations is proportionally reduced to the same power level as the first pole power of the second converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power limit is reached; The total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power limit is reached; The sum of the first pole power of the first and second converter stations is proportionally reduced to the same power level as the first pole power of the fourth converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked; the lost power is transferred to the first pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations remains unchanged.

3. The power transfer method of the four-terminal new energy direct current transmission system according to claim 1, characterized in that: Select the blocking mode according to the different stations where the fault is located, and select the power transfer path for the second control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power lost by the first and second converter stations is transferred to another valve group at the first pole of the first converter station until its power limit, and the remaining power is transferred to another valve group at the first pole of the second converter station until its power limit; the power lost by the third converter station is transferred to another valve group at the first pole of the third converter station until its power limit; the power lost by the fourth converter station is transferred to another valve group at the first pole of the fourth converter station until its power limit; the power of the second poles of the four converter stations remains unchanged; If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to a single-pole current control mode, and the lost power is transferred to the first pole of the second converter station until its power upper limit is reached; The sum of the first pole power of the third and fourth converter stations is proportionally reduced to the same power level as the first pole power of the second converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit is reached; The total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit; The sum of the first pole power of the first and second converter stations is proportionally reduced to the same power level as the first pole power of the fourth converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations remains unchanged.

4. The power transfer method of the four-terminal new energy direct current transmission system according to claim 1, characterized in that: Select the blocking mode according to the different stations where the fault is located, and select the power transfer path for the third control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power lost in the first and second converter stations is first transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the second converter station until its power upper limit; The power lost in the third converter station is transferred to the second pole of the third converter station until its power limit; The power lost in the fourth converter station is transferred to the second pole of the fourth converter station until its power limit is reached; If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power upper limit, the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and further the remaining power is transferred to the second pole of the fourth converter station until its power upper limit; The total power of the first pole of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second pole of the third and fourth converter stations is proportionally increased to the same level as the total power of the second pole of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked; the lost power is transferred to the first pole of the third converter station until its power upper limit, and the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and further the remaining power is transferred to the second pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as that of the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as that of the second poles of the first and second converter stations.

5. The power transfer method of the four-terminal new energy direct current transmission system according to claim 1, characterized in that: Select a blocking mode according to the different stations where the fault is located, and select a power transfer path for the fourth control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power losses of the first and second converter stations is first transferred to another valve group of the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second converter station until its power upper limit; the power lost at the third converter station is equally transferred to another valve group and the second pole of the first pole of the third converter station until its power upper limit; the power lost at the fourth converter station is equally transferred to another valve group and the second pole of the first pole of the fourth converter station until its power upper limit; If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked and switched to a single-pole current control mode; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit, the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and further the remaining power is transferred to the second pole of the fourth converter station until its power upper limit; The total power of the first pole of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second pole of the third and fourth converter stations is proportionally increased to the same level as the total power of the second pole of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit, and the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and further the remaining power is transferred to the second pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as that of the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as that of the second poles of the first and second converter stations.

6. The power transfer method of the four-terminal new energy direct current transmission system according to claim 1, characterized in that: Also includes, When a bipolar fault occurs in the first converter station, the bipolar of the first converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the second converter station until its power upper limit is reached; The sum of the powers of the third and fourth converter station bipolar poles is proportionally reduced to the same power level as the second converter station bipolar pole; When a bipolar fault occurs in the second converter station, the bipolar of the second converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the first converter station until its power upper limit is reached; The sum of the powers of the third and fourth converter station bipolars is proportionally reduced to the same power level as the first converter station bipolar; When a bipolar fault occurs in the third converter station, the bipolar of the third converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the fourth converter station until its power upper limit is reached; The sum of the powers of the first and second converter station bipolar poles is proportionally reduced to the same power level as the fourth converter station bipolar pole; When a bipolar fault occurs in the fourth converter station, the bipolar of the fourth converter station is blocked and switched to a unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the third converter station until its power upper limit is reached; The total power of the first and second converter station bipolars is proportionally reduced to the same power level as the third converter station bipolar.

7. A power transfer device for a four-terminal new energy direct current power transmission system, the four-terminal new energy direct current power transmission system comprising four converter stations, the four converter stations comprising two rectifier stations and two inverter stations, the converter station for new energy access in the two rectifier stations being called the first converter station, and the converter station for non-new energy access being called the second converter station; the two inverter stations being called the third converter station and the fourth converter station, respectively; characterized in that: include, A fault lockout judgment module is configured to judge whether a single-valve, single-pole or single-station fault lockout occurs in a converter station under the condition that the bipolar of the four converter stations of the four-terminal new energy direct current transmission system are all in operation; and The power transfer control module is configured to select a corresponding blocking mode according to different stations where the fault is located, and select a corresponding power transfer path according to the control mode before blocking; Among them, the control modes include four types: the first control mode, the first pole and the second pole are both unipolar current control mode; the second control mode, the first pole is a bipolar power control mode, and the second pole is a unipolar current control mode; the third control mode, the first pole is a unipolar current control mode, and the second pole is a bipolar power control mode; the fourth control mode, the first pole and the second pole are both bipolar power control mode; Among them, the pole where fault locking occurs is called the first pole, and the pole where fault locking does not occur is called the second pole.

8. The power transfer device of the four-terminal new energy direct current transmission system according to claim 7, characterized in that: The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the first control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; the lost power is not transferred; the second pole power of the four converter stations remains unchanged; If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the first pole of the second converter station until its power upper limit; The sum of the first pole power of the third and fourth converter stations is proportionally reduced to the same power level as the first pole power of the second converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power limit is reached; The total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power limit is reached; The sum of the first pole power of the first and second converter stations is proportionally reduced to the same power level as the first pole power of the fourth converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked; the lost power is transferred to the first pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations remains unchanged.

9. The power transfer device of the four-terminal new energy direct current transmission system according to claim 7, characterized in that: The power transfer control module selects a blocking mode according to the different stations where the fault is located, and selects a power transfer path for the second control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power lost by the first and second converter stations is transferred to another valve group at the first pole of the first converter station until its power limit, and the remaining power is transferred to another valve group at the first pole of the second converter station until its power limit; the power lost by the third converter station is transferred to another valve group at the first pole of the third converter station until its power limit; the power lost by the fourth converter station is transferred to another valve group at the first pole of the fourth converter station until its power limit; the power of the second poles of the four converter stations remains unchanged; If a single-pole fault occurs in the first pole of the first converter station, the first pole of the first converter station is locked and switched to a single-pole current control mode, and the lost power is transferred to the first pole of the second converter station until its power upper limit is reached; The sum of the first pole power of the third and fourth converter stations is proportionally reduced to the same power level as the first pole power of the second converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit is reached; The total power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the first converter station; the power of the second poles of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit; The sum of the first pole power of the first and second converter stations is proportionally reduced to the same power level as the first pole power of the fourth converter station; the second pole power of the four converter stations remains unchanged; If a single valve or single pole fault occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as the first pole of the third converter station; the power of the second poles of the four converter stations remains unchanged.

10. The power transfer device of the four-terminal new energy direct current transmission system according to claim 7, characterized in that: The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the third control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power lost in the first and second converter stations is first transferred to the second pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the second converter station until its power upper limit; The power lost in the third converter station is transferred to the second pole of the third converter station until its power limit; The power lost in the fourth converter station is transferred to the second pole of the fourth converter station until its power limit is reached; If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the second converter station, the first pole of the second converter station is locked; the lost power is transferred to the first pole of the first converter station until its power upper limit, the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the third converter station, the first pole of the third converter station is locked; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and further the remaining power is transferred to the second pole of the fourth converter station until its power upper limit; The total power of the first pole of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second pole of the third and fourth converter stations is proportionally increased to the same level as the total power of the second pole of the first and second converter stations; If a single valve or single pole failure occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked; the lost power is transferred to the first pole of the third converter station until its power upper limit, and the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and further the remaining power is transferred to the second pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as that of the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as that of the second poles of the first and second converter stations.

11. The power transfer device of the four-terminal new energy direct current transmission system according to claim 7, characterized in that: The power transfer control module selects a blocking mode according to different stations where the fault is located, and selects a power transfer path for the fourth control mode according to the control mode before blocking, including: If a single valve failure occurs at the first pole of the first converter station, the single valve of the first converter station is locked, and the corresponding valve groups of the second, third and fourth converter stations are locked; The sum of the power losses of the first and second converter stations is first transferred to another valve group of the first pole of the first converter station until its power upper limit, and the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second converter station until its power upper limit; the power lost at the third converter station is equally transferred to another valve group and the second pole of the first pole of the third converter station until its power upper limit; the power lost at the fourth converter station is equally transferred to another valve group and the second pole of the first pole of the fourth converter station until its power upper limit; If a single-pole fault occurs at the first pole of the first converter station, the first pole of the first converter station is locked and switched to a single-pole current control mode; the lost power is transferred to the second pole of the first converter station until its power upper limit, the remaining power is transferred to the first pole of the second converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the second converter station, the first pole of the second converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the first converter station until its power upper limit, the remaining power is transferred to the second pole of the first converter station until its power upper limit, and the remaining power is further transferred to the second pole of the second converter station until its power upper limit; The sum of the power of the first poles of the third and fourth converter stations is proportionally reduced to the same power level as the first pole of the second converter station, and the sum of the power of the second poles of the third and fourth converter stations is proportionally increased to the same level as the sum of the power of the second poles of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the third converter station, the first pole of the third converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the fourth converter station until its power upper limit, and the remaining power is transferred to the second pole of the third converter station until its power upper limit, and further the remaining power is transferred to the second pole of the fourth converter station until its power upper limit; The total power of the first pole of the first and second converter stations is proportionally reduced to the same power level as the first pole of the fourth converter station; the total power of the second pole of the third and fourth converter stations is proportionally increased to the same level as the total power of the second pole of the first and second converter stations; If a single valve or single pole fault occurs in the first pole of the fourth converter station, the first pole of the fourth converter station is locked and switched to the single pole current control mode; the lost power is transferred to the first pole of the third converter station until its power upper limit, and the remaining power is transferred to the second pole of the fourth converter station until its power upper limit, and further the remaining power is transferred to the second pole of the third converter station until its power upper limit; The total power of the first poles of the first and second converter stations is proportionally reduced to the same power level as that of the first pole of the third converter station; the total power of the second poles of the third and fourth converter stations is proportionally increased to the same level as that of the second poles of the first and second converter stations.

12. The power transfer device of the four-terminal new energy direct current transmission system according to claim 7, characterized in that: Also includes, When a bipolar fault occurs in the first converter station, the bipolar of the first converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the second converter station until its power upper limit is reached; The sum of the powers of the third and fourth converter station bipolar poles is proportionally reduced to the same power level as the second converter station bipolar pole; When a bipolar fault occurs in the second converter station, the bipolar of the second converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the first converter station until its power upper limit is reached; The sum of the powers of the third and fourth converter station bipolars is proportionally reduced to the same power level as the first converter station bipolar; When a bipolar fault occurs in the third converter station, the bipolar of the third converter station is blocked and switched to the unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the fourth converter station until its power upper limit is reached; The sum of the powers of the first and second converter station bipolar poles is proportionally reduced to the same power level as the fourth converter station bipolar pole; When a bipolar fault occurs in the fourth converter station, the bipolar of the fourth converter station is blocked and switched to a unipolar current control mode, and the power loss of each pole is transferred to the corresponding pole of the third converter station until its power upper limit is reached; The total power of the first and second converter station bipolars is proportionally reduced to the same power level as the third converter station bipolar.

13. A power transfer device for a four-terminal new energy direct current transmission system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, the steps of the power transfer method of the four-terminal new energy direct current transmission system as described in any one of claims 1 to 6 are implemented.

14. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, the steps of the power transfer method of the four-terminal new energy direct current transmission system as described in any one of claims 1 to 6 are implemented.

Images