Multi-terminal DC power grid system and operation control method thereof

Abstract

The invention discloses a multi-terminal direct-current power grid system and an operation control method thereof. According to the system, a starting resistor is arranged between an alternating-current power grid and a converter station; the method comprises the following steps: when starting control is carried out on each converter station, firstly putting a starting resistor and keeping the converter station locked when a direct-current power grid is connected to an alternating-current power grid, and cutting off the starting resistor before the converter station is unlocked after a direct-current voltage is established in the converter station and a voltage fluctuation condition is met; the voltage and power oscillation of the system is suppressed by using the power consumption capability in the starting resistor input process, and the converter station in the system is gradually unlocked after the starting resistor is cut off, so that the smooth access of the direct-current power grid is realized, and extra loss is not generated during the steady-state operation of the direct-current power grid.

Description

Technical Field

[0001] The present invention relates to a direct current transmission system control technology, and in particular to a multi-terminal direct current power grid system and an operation control method thereof. Background Art

[0002] Multi-Terminal HVDC (MTDC) is a high-voltage DC grid structure that connects multiple converter stations together. It is usually used to enhance the interconnection, stability and power transmission efficiency between power systems in different regions. Different from traditional two-terminal DC transmission (i.e. transmission between a pair of converter stations), multi-terminal DC grid can achieve flexible interconnection between multiple converter stations and support more complex power dispatching and load management.

[0003] Since multiple converter stations need to be controlled when a multi-terminal DC grid is put into use, a reasonable startup strategy should not only ensure the stable access and exit of the grid, but also prevent stability problems caused by power oscillations. The converter stations in the multi-terminal DC grid are often disturbed by complex power fluctuations during the startup process. Existing methods such as step-by-step startup and step-down startup usually find it difficult to strike a balance between fast response and stability. Especially when multiple converter stations are started in parallel, it is difficult to ensure accurate coordination between the stations. In addition, most of the current control strategies rely on static set values ​​and simple feedback control. When dealing with system oscillations during the startup process, most of them adopt passive suppression methods, lack adaptive adjustment capabilities, and cannot cope with complex and dynamic grid environments. Summary of the invention

[0004] Based on this, the present invention proposes a multi-terminal DC power grid system and an operation control method thereof, so that when the DC power grid is connected to the AC power grid through a converter station, vibration of the system voltage and power can be avoided and smooth access to the DC power grid can be achieved.

[0005] In a first aspect, the present invention provides a multi-terminal DC power grid system, comprising a plurality of converter stations, wherein the converter stations are used to integrate the DC power grid into the AC power grid, and a starting resistor is provided between the converter stations and the AC power grid.

[0006] Further, the multi-terminal DC power grid system comprises a first starting area and a second starting area;

[0007] The first starting area includes a master converter station and a slave converter station, and the master converter station and the slave converter station are connected in a parallel-parallel manner;

[0008] The DC side of the converter station in the second starting area is connected to the first starting area through a DC converter.

[0009] Furthermore, the master converter station and the slave converter stations in the first starting area are connected in series in a ring shape through a transmission line, and the master converter station is also connected to one of the slave converter stations through the transmission line.

[0010] Furthermore, the DC side of the converter station in the second starting area is connected to one of the slave converter stations in the first starting area through a DC converter.

[0011] In a second aspect, the present invention provides a multi-terminal DC power grid system operation control method, comprising:

[0012] When the DC grid is connected to the AC grid, a starting resistor is inserted between the converter station and the AC grid;

[0013] The DC voltage of the converter station is measured in real time. When the DC voltage of the converter station meets the voltage fluctuation condition, the starting resistor is cut off and the converter station is controlled to be unlocked.

[0014] Furthermore, the DC voltage of the converter station is measured in real time, the starting resistor is cut off when the DC voltage of the converter station meets the voltage fluctuation condition, and the converter station is controlled to be unlocked, including:

[0015] Real-time measurement of the DC bus voltage of the main converter station;

[0016] When the DC bus voltage of the main converter station meets the first voltage fluctuation condition, the starting resistor between the main converter station and the AC power grid is removed, and the main converter station is controlled to be unlocked to establish the DC voltage of the first starting area;

[0017] When the DC voltage in the first starting area meets the second voltage fluctuation condition, the slave converter station and the converter station in the second starting area are controlled to be unlocked.

[0018] Further, when the DC voltage of the first starting area meets the second voltage fluctuation condition, controlling the converter station of the second starting area to unlock includes:

[0019] When the DC voltage in the first starting area meets the second voltage fluctuation condition, the part of the DC converter close to the first starting area is controlled to start, and the converter station in the second starting area is not unlocked;

[0020] After the DC converter establishes the internal AC voltage, the DC converter controls the part close to the second starting area to start, so as to establish the DC voltage of the second starting area;

[0021] When the DC voltage in the second starting area meets the third voltage fluctuation condition, the converter station in the second starting area is controlled to be unlocked.

[0022] Further, after the DC converter establishes the internal AC voltage, the DC converter is controlled to start a portion close to the second start-up area, and establishing the DC voltage in the second start-up area includes:

[0023] Internal AC voltage of the real-time strategy DC converter;

[0024] When the internal AC voltage meets the fourth voltage fluctuation condition, the portion of the DC converter close to the second starting area is controlled to start, so as to establish the DC voltage in the second starting area.

[0025] Furthermore, the main converter station is controlled by a dual closed-loop control strategy of a DC voltage control outer loop and a current control inner loop.

[0026] Furthermore, the slave converter station and the converter station in the second starting area are controlled by adopting a double closed-loop control strategy of a power control outer loop and a current control inner loop.

[0027] In a third aspect, the present invention provides a multi-terminal DC power grid system operation control device, comprising:

[0028] A starting resistance input control module is used to input a starting resistance between the converter station and the AC grid when the DC grid is connected to the AC grid;

[0029] The converter station start-up control module is used to measure the DC voltage of the converter station in real time. When the DC voltage of the converter station meets the voltage fluctuation condition, the start-up resistor is cut off and the converter station is started.

[0030] In a fourth aspect, the present invention provides a multi-terminal DC power grid system operation control system, comprising a memory storing computer executable instructions and a processor, wherein when the computer executable instructions are executed by the processor, the device executes each step of the multi-terminal DC power grid system operation control method provided in the second aspect.

[0031] In a fifth aspect, the present invention provides a readable storage medium storing a computer executable program, which, when executed, can implement the various steps of the multi-terminal DC power grid system operation control method provided in the second aspect.

[0032] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0033] The present invention provides a multi-terminal DC power grid system and an operation control method thereof. In terms of topological structure, a starting resistor is arranged between an AC power grid and a converter station. When each converter station is started up and controlled, the starting resistor is firstly put into operation and the converter station is kept locked when the DC power grid is connected to the AC power grid. After the DC voltage is established at the converter station and the voltage fluctuation condition is met, the starting resistor is cut off before the converter station is unlocked. The power consumption capacity of the starting resistor during the putting-in process is used to suppress the voltage and power oscillation of the system. After the starting resistor is cut off, the converter stations in the system are gradually unlocked, so as to realize smooth access to the DC power grid and generate no additional loss when the DC power grid is in steady-state operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 It is a connection diagram of setting a starting resistor in a multi-terminal DC power grid system provided by an embodiment of the present invention;

[0036] Figure 2 It is a network topology diagram of a multi-terminal DC power grid system provided by an embodiment of the present invention;

[0037] Figure 3 This is a flowchart of a multi-terminal DC power grid system operation control method provided by an embodiment of the present invention;

[0038] Figure 4 It is a structural diagram of a multi-terminal DC power grid system operation control device provided by an embodiment of the present invention;

[0039] Figure 5 It is an architecture diagram of a multi-terminal DC power grid system operation control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention takes into account the voltage and power oscillations that occur during the startup process of a multi-terminal DC power grid system. Since the AC power grid is already in steady-state operation before the DC power grid is connected to the AC power grid, the DC power grid will inevitably generate voltage and power oscillations due to the sudden inflow of power when the DC power grid is connected to the DC power grid by closing the circuit breaker. Referring to the oscillation smoothing strategy commonly used in AC / DC systems, the present invention sets a starting resistor between the converter station and the AC power grid, so that the starting resistor is put into operation when the DC power grid is connected to the AC power grid, and the starting resistor is cut off before the converter station is unlocked. The power consumption capacity of the starting resistor during the time period of input is utilized to suppress voltage and power oscillations, thereby achieving smooth access to the DC power grid.

[0042] Specific reference Figure 1An embodiment of the present invention provides a connection diagram of setting a starting resistor in a multi-terminal DC power grid system. An AC circuit breaker and a transformer are connected in series between the AC power grid system and the converter station (VSC). In this embodiment, a starting resistor is connected in series between the AC circuit breaker and the converter station. When the DC power grid needs to be connected to the AC system through the converter station, the starting resistor is put into operation. After the DC voltage of the converter station is established, the starting resistor is removed and the converter station is unlocked.

[0043] The starting resistor is put into use within a short period of time before the converter station is unlocked. The starting resistor can absorb instantaneous power at the initial stage of connection, so as to slow down the initial current and voltage rise rate of the converter station and avoid excessive power fluctuations in the system. At the same time, the starting resistor shares part of the voltage, thereby suppressing voltage mutations and reducing the voltage difference at the moment of connection. The introduction of the starting resistor reduces the current impact on the DC and AC sides, reduces the impact and loss on the converter station equipment, absorbs part of the power, and avoids the impact of mutations when the DC grid is directly connected to the system stability, which is conducive to the stable operation of the system.

[0044] In a further example, the resistance value of the starting resistor can be selected based on the load characteristics of the multi-terminal DC transmission system and the capacity of the converter station. The connection time of the resistor needs to be controlled within a reasonable range. The removal of the starting resistor and the unlocking of the converter station need to be strictly synchronized to ensure that the converter station is quickly connected to operation after the starting resistor is removed to avoid additional oscillations.

[0045] In a further embodiment, the multi-terminal DC power grid system may include a first starting area and a second starting area, wherein the first starting area adopts a master-slave control strategy, including a master converter station and a slave converter station, the master converter station and the slave converter station are connected in a parallel-parallel manner, and the DC side of the converter station in the second starting area is connected to the first starting area through a DC converter.

[0046] The hybrid topology of a multi-terminal DC transmission system usually uses transmission lines to connect the converter stations in the system into a closed loop. When a converter station fails, other converter stations use their own overload capacity to keep the system running, which has higher flexibility.

[0047] In some embodiments, the master converter station and the slave converter station in the first starting area are connected in series in a ring shape through a transmission line, and the master converter station is also connected to one of the slave converter stations through a transmission line, and the DC side of the converter station in the second starting area is connected to one of the slave converter stations in the first starting area through a DC converter.

[0048] For example, Figure 2 A multi-terminal DC power grid system provided by an embodiment of the present invention is illustrated, wherein the first starting area includes a four-terminal DC power transmission system, and the second starting area includes a converter station and a DC-DC converter.

[0049] The four-terminal DC transmission system in the first starting area includes four converter stations, namely VSC1~VSC4, among which VSC1 is the main converter station, VSC2~VSC4 are slave converter stations, and the four converter stations adopt a ring network hybrid topology structure, among which the four converter stations VSC1~VSC4 are connected in a ring shape through transmission lines 13, 23, 24, and 14, and the converter station VSC1 is also connected to the converter station VSC2 through the transmission line 12.

[0050] The second starting area includes a converter station VSC5 and a DC-DC converter. The converter station VSC5 is connected to the converter station VSC4 of the first starting area through the DC-DC converter, that is, the first starting area is connected to the DCC1 side of the DC-DC converter, and the converter station VSC5 is connected to the DCC2 side of the DC-DC converter through the transmission line 45.

[0051] exist Figure 2 In the illustrated multi-terminal DC power grid system, the first starting area is a four-terminal meshed DC transmission system with a voltage level of 400 kV, the second starting area is a DC transmission line 45 with a voltage level of ±400 kV, the converter stations VSC1~VSC4 are unipolar converter stations, and the converter station VSC5 is a bipolar converter station.

[0052] See also Figure 3 Based on the multi-terminal DC power grid systems provided in the above embodiments, an embodiment of the present invention provides a multi-terminal DC power grid system operation control method, comprising the following steps:

[0053] Step S310: When the DC grid is connected to the AC grid, a starting resistor is connected between the converter station and the AC grid.

[0054] Specifically, after the AC circuit breaker is closed, the starting resistor is put into operation before the converter station is unlocked. It is usually connected to the converter station through a series resistor. After the starting resistor is put into operation, the resistor will temporarily share part of the current and voltage impact of the converter station port, and gradually establish the initial voltage level on the DC side. After the starting resistor is connected, its resistance characteristics are used to consume the power during the DC grid access process, reduce the power fluctuation caused by the initial voltage mutation, and reduce the current fluctuation amplitude. By controlling the duration of the starting resistor, the degree of power consumption can be adjusted. The typical startup time is generally short (hundreds of milliseconds to several seconds) to ensure that the main oscillations are suppressed before unlocking.

[0055] Step S320: Measure the DC voltage of the converter station in real time. When the DC voltage of the converter station meets the voltage fluctuation condition, cut off the starting resistor and control the converter station to unlock.

[0056] Specifically, before the converter station is unlocked, the starting resistor is cut off. When the resistor is cut off, the voltage and current are already within a reasonable range, and the fluctuation amplitude has been reduced. The DC grid can be stably connected to the AC system. After the starting resistor is cut off, the converter station enters a normal working state and resumes normal power transmission. No additional power consumption measures are required.

[0057] In a further embodiment, for a system adopting a master-slave control strategy, the master converter station is used to control the DC voltage to be constant, so the master converter station is usually unlocked before the slave converter station, and other converter stations are unlocked after a stable DC voltage is established.

[0058] Specifically, for the multi-terminal direct current power transmission system with two starting areas provided in the above embodiment, step S320 may include the following steps:

[0059] Step S321. Measure the DC bus voltage of the main converter station in real time.

[0060] Specifically, in the first starting area, the main converter station adopts a dual closed-loop control strategy of a DC voltage control outer loop and a current control inner loop for control, and the slave converter station and the converter station in the second starting area adopt a dual closed-loop control strategy of a power control outer loop and a current control inner loop for control. The prerequisite for the power control type converter station in the first starting area to track the respective power command values ​​is that the DC voltage in the first starting area is stable. Figure 2 Taking the illustrated system as an example, the voltage-controlled converter station VSC1 in the first starting area should be started before other converter stations, and other converter stations should be started after a stable DC voltage is established.

[0061] In order to prevent the commissioning of each power-controlled converter station from causing system oscillation, the power increase rate of the power-controlled converter station is limited so that it does not exceed the set rate to ensure that the process of the DC power grid entering a steady state does not cause oscillation due to a sudden change in the power command value.

[0062] Step S322: When the DC bus voltage of the main converter station meets the first voltage fluctuation condition, the starting resistor between the main converter station and the AC power grid is removed, and the main converter station is controlled to be unlocked to establish the DC voltage of the first starting area.

[0063] Specifically, in order to ensure that the voltage fluctuation of the main converter station is within the controllable range during the access process, a voltage fluctuation threshold or threshold value is usually set, that is, the first voltage fluctuation condition. Only when the DC bus voltage of the main converter station meets this condition (that is, the fluctuation amplitude is lower than the set value), can the starting resistor be considered to be cut off, ensuring that the voltage is basically stable before the starting resistor is cut off, and will not cause excessive disturbance to the system. When the DC bus voltage fluctuation meets the first voltage fluctuation condition, the starting resistor between the main converter station and the AC power grid is cut off to avoid power consumption on the resistor, so that the main converter station can enter normal operation.

[0064] The unlocking operation means that the main converter station is fully connected to the DC grid, starts normal operation, and assumes its rated power transmission task. Before unlocking, it is ensured that the DC bus voltage has met the voltage target of the first starting area so that the converter station will not cause voltage shock or power transient after connection. After the resistor is removed, the connection between the DC bus voltage and the AC grid becomes direct. This step requires that the voltage and power of the converter station have stabilized to avoid additional oscillations. After the main converter station is unlocked, the initial DC voltage (i.e., the voltage of the first starting area) is set through its control system. This voltage is set as the target voltage at the initial stage of connection, so that the DC bus of the power grid can gradually transition to the rated voltage. At the same time, the voltage fluctuation is closely monitored and appropriately adjusted to avoid voltage overshoot or oscillation caused by unstable factors.

[0065] In some embodiments, the first voltage fluctuation condition can be set as the DC bus voltage of the main converter station fluctuating less than 5% compared to the first voltage reference value to meet the system master-slave control bus voltage stability.

[0066] Step S323: When the DC voltage in the first starting area meets the second voltage fluctuation condition, the slave converter station and the converter station in the second starting area are controlled to be unlocked.

[0067] In this step, for the slave converter station and the converter station in the second starting area, after the main converter station in the first starting area is unlocked, it is necessary to first establish the DC voltage in the first starting area, and continue to monitor the fluctuation of the DC bus voltage of the main converter station in real time. Usually, the second voltage fluctuation condition at this time refers to a more stringent voltage fluctuation threshold, which has lower voltage fluctuation requirements than the first voltage fluctuation condition, ensuring that the voltage has stabilized within a smaller fluctuation range.

[0068] After confirming that the second voltage fluctuation condition is met, the control is unlocked from the converter station to synchronize it with the DC grid. The unlocking of the second start-up area will bring new power inflow or outflow. Therefore, the output power of the converter station needs to be gradually increased or decreased during unlocking to avoid large voltage and power fluctuations in the system.

[0069] In some embodiments, the second voltage fluctuation condition can be set as the DC bus voltage of the main converter station fluctuating by less than 5% compared to the second voltage reference value to meet the system master-slave control bus voltage stability.

[0070] For the second starting area, since the converter station is connected to the first starting area through a DC converter, the basis for the operation of the DC converter is that one of the two connected DC systems has established a stable DC voltage. The converter establishes an internal AC voltage based on the DC voltage on this side, and then establishes a DC voltage on the other DC side based on the AC voltage, thereby realizing the voltage conversion function.

[0071] In a further embodiment, unlocking the converter station in the second starting area includes the following steps:

[0072] Step S324: When the DC voltage in the first starting area meets the second voltage fluctuation condition, the part of the DC converter close to the first starting area is controlled to start, and the converter station in the second starting area is not unlocked.

[0073] Step S325: After the DC converter establishes the internal AC voltage, the portion of the DC converter close to the second start-up area is controlled to start, so as to establish the DC voltage of the second start-up area.

[0074] Step S326: When the DC voltage in the second starting area meets the third voltage fluctuation condition, the converter station in the second starting area is controlled to be unlocked.

[0075] by Figure 2 Taking the illustrated system as an example, the DC-DC converter in the second start-up area includes two parts, DCC1 and DCC2, wherein DCC1 is connected to the first start-up area, and DCC2 is connected to the converter station VSC5. The DCC1 connected to the first start-up area is responsible for establishing the internal AC voltage of the DC / DC converter, and DCC2 is responsible for establishing the DC voltage of the second area. The power output of the converter station VSC5 in the second start-up area should be based on the stable DC voltage of the second start-up area, and its power rise rate should also be limited.

[0076] Similarly, the third voltage fluctuation condition can be set to a fluctuation of less than 5% compared to the third voltage reference value to ensure the bus voltage stability in the second starting area. The internal control voltage of the DC-DC converter should also meet the fluctuation condition. The converter station in the second starting area can be unlocked after the internal AC voltage of the converter is stable.

[0077] Below Figure 2 Taking the illustrated system as an example, the operation control method of the multi-terminal DC power grid system provided by the embodiment of the present invention is further introduced.

[0078] Each converter station in the first starting area adopts a master-slave control strategy, with VSC1 as the master converter station, controlling the DC voltage of the four-terminal system to be constant, VSC2~VSC4 as slave converter stations, controlling their respective power outputs, and the converter station VSC5 in the second starting area controls the transmission power of line 45, and the DC-DC converter controls the DC voltage of line 45 to be ±400kV.

[0079] Each converter station adopts a dual closed-loop control method, among which VSC1 adopts a dual closed-loop control strategy consisting of a DC voltage control outer loop and a current control inner loop, and the remaining converter stations VSC2~VSC5 adopt a dual closed-loop control strategy consisting of a power control outer loop and a current control inner loop.

[0080] In the modeling process of this embodiment, synchronous rotating coordinate transformation (dq transformation) and sinusoidal pulse width modulation (SPWM) of a voltage source converter are used.

[0081] The voltage and power command values ​​of each converter station are shown in Table 1. In Table 1, the 400kV station is a symmetrical unipolar VSC, and the ±400kV station is a bipolar VSC; the power sign is positive when flowing into the DC grid and negative when flowing out of the DC grid.

[0082] Table 1

[0083]

[0084] Line 45 transmits 1200MW of active power to the first start-up area through a DC-DC converter. When the five-terminal DC transmission system is in steady-state operation, VSC2, VSC3, and VSC5 work in rectifier mode, and VSC1 and VSC4 work in inverter mode; VSC1 controls the voltage of the four-terminal DC transmission system in the first start-up area to be constant. As a balancing node in the system, if the five-terminal DC transmission system has power imbalance, VSC1 will change its power output to balance the power of the grid.

[0085] The startup control of each converter and DC converter in the system is as follows:

[0086] When the DC grid is connected to the AC grid, the starting resistors of each converter station are put into operation at the moment. When the DC grid rectifier voltage fluctuates by less than 5% compared with the reference value, the starting resistors are removed.

[0087] After the starting resistor is removed, the converter station VSC1 is unlocked, and the DC voltage of the first starting area is established. When the DC voltage of the first starting area fluctuates by less than 5% compared with the reference value, the converter stations VSC2~VSC4 and the DC-DC converter are unlocked.

[0088] DCC1 in the DC-DC converter starts before DCC2. After DCC1 establishes a stable internal AC voltage of the converter, DCC2 is started and a DC voltage of the second start-up region is established. Specifically, DCC2 is started when the internal AC voltage of the converter fluctuates less than 5% compared to its reference value.

[0089] The converter station VSC5 is unlocked after the DC-DC converter has established a stable DC voltage in the second starting area. Specifically, the converter station VSC5 is unlocked when the DC voltage in the second starting area fluctuates by less than 5% compared with its reference value.

[0090] The above embodiments provide an operation control method for a multi-terminal DC power grid system. In terms of topology, a starting resistor is arranged between the AC power grid and the converter station. When starting control is performed on each converter station, the starting resistor is first put into operation and the converter station is kept locked when the DC power grid is connected to the AC power grid. After the DC voltage is established at the converter station and the voltage fluctuation condition is met, the starting resistor is cut off before the converter station is unlocked. The power consumption capacity of the starting resistor during the process of putting the starting resistor into operation is used to suppress the voltage and power oscillation of the system. After the starting resistor is cut off, the converter stations in the system are gradually unlocked to achieve smooth access to the DC power grid, and no additional loss is generated when the DC power grid is in steady state operation.

[0091] The above method disclosed can be implemented by using various forms of equipment, so the present invention also discloses a multi-terminal DC power grid system operation control device corresponding to the above method, and a specific embodiment is given below for detailed description.

[0092] like Figure 4 As shown, an embodiment of the present invention provides a multi-terminal DC power grid system operation control device, comprising:

[0093] A starting resistance input control module 402 is used to input a starting resistance between the converter station and the AC grid when the DC grid is merged into the AC grid;

[0094] The converter station start-up control module 404 is used to measure the DC voltage of the converter station in real time, cut off the start-up resistor when the DC voltage of the converter station meets the voltage fluctuation condition, and start the converter station.

[0095] The implementation principle and technical effects of the device provided in the embodiments of the present application are the same as those of the aforementioned method embodiments. For the sake of brief description, for matters not mentioned in the device embodiment, reference may be made to the corresponding contents in the aforementioned method embodiments.

[0096] The methods and related devices mentioned in the above embodiments are described with reference to the method flow charts and / or structural diagrams provided in the embodiments of the present application. Specifically, each process and / or block in the method flow charts and / or structural diagrams, as well as the combination of processes and / or blocks in the flow charts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the process. Figure 1 A process or multiple processes and / or structures Figure 1These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 Schematic diagram of one or more processes and / or structures Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A flow or multiple flows and / or structures illustrate the steps of the functions specified in one block or multiple blocks.

[0097] The following embodiments are described by taking the method applied to a computer device as an example. It can be understood that the computer device can be any device with computing and processing functions, and can be but not limited to a server or a personal laptop computer, etc. In one embodiment, the computer device can be an application server, and the application server can be a server for running an application to be tested.

[0098] See also Figure 5 , which shows a hardware structure block diagram of a multi-terminal DC power grid system operation control system, which control system is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic devices can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present application described and / or required herein.

[0099] like Figure 5 As shown, the control system includes: at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4;

[0100] In the embodiment of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 communicate with each other through the communication bus 4;

[0101] The processor 1 may be a central processing unit CPU, or an application-specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention, etc.;

[0102] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), etc., such as at least one disk memory;

[0103] The memory stores a program, and the processor can call the program stored in the memory, wherein the program is used to implement each processing flow of the aforementioned multi-terminal DC power grid system operation control solution.

[0104] An embodiment of the present invention further provides a readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the computer program implements each processing flow of the multi-terminal DC power grid system operation control scheme provided in the above embodiment and / or any possible implementation method in combination with the embodiment.

[0105] The above-mentioned embodiments have described the present invention in particular detail with respect to possible scenarios, and those skilled in the art will recognize that the present invention can be practiced through other embodiments. The specific naming of components, the capitalization of terms, attributes, data structures, or any other programming or structural aspects are not mandatory or important, and the mechanisms or features of the present invention may have different names, forms, or procedures. The system may be implemented by a combination of hardware and software (as described), entirely by hardware elements, or entirely by software elements. The specific division of functions between the various system components described herein is exemplary only and not mandatory; on the contrary, the functions performed by a single system component may be performed by multiple components, or the functions performed by multiple components may be performed by a single component.

[0106] Those skilled in the art should understand that the various steps of the above disclosed method can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, optionally, they can be implemented with program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0107] These computing device executable programs (also referred to as programs, software, software applications, or code) include machine instructions for programmable processors, and these computing programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, device, and / or device (e.g., disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0108] Certain aspects of the present invention include process steps and instructions described herein in the form of algorithms. It should be noted that the process steps and instructions of the present invention can be implemented in software, firmware and / or hardware, and when implemented by software, it can be downloaded, stored on different platforms used by various operating systems and operated from the platforms.

[0109] Those skilled in the art will understand that the structures shown in the accompanying drawings are merely block diagrams of partial structures related to the scheme of the present application, and do not constitute a limitation on the terminal device to which the scheme of the present application is applied. The specific terminal device may include more or fewer components than shown in the figures, or combine certain components, or have a different arrangement of components.

[0110] Some embodiments may be described using "coupled" and "connected" and their derivatives. It should be understood that these terms are not intended to be synonymous with each other. For example, some embodiments may be described using the word "connected" to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the word "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "coupled" may also mean that two or more elements are not in direct contact with each other, but still cooperate or interact with each other. The embodiments are not limited to this context.

[0111] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "possible design" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0112] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0113] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-terminal DC power grid system, comprising a plurality of converter stations, the converter stations being used to merge the DC power grid into the AC power grid, characterized in that: A starting resistor is connected in series between the converter station and the AC power grid.

2. The system according to claim 1, characterized in that The system includes a first startup area and a second startup area; The first starting area includes a master converter station and a slave converter station, and the master converter station and the slave converter station are connected in a parallel-parallel manner; The DC side of the converter station in the second starting area is connected to the first starting area through a DC converter.

3. The system according to claim 2, characterized in that The DC side of the converter station in the second starting area is connected to one of the slave converter stations in the first starting area through a DC converter.

4. A multi-terminal DC power grid system operation control method, characterized in that: Used to control the startup of the multi-terminal DC power grid system according to any one of claims 1 to 3, comprising: When the DC grid is connected to the AC grid, a starting resistor is inserted between the converter station and the AC grid; The DC voltage of the converter station is measured in real time. When the DC voltage of the converter station meets the voltage fluctuation condition, the starting resistor is cut off and the converter station is controlled to be unlocked.

5. The method according to claim 1, characterized in that The real-time measurement of the DC voltage of the converter station, the cutting off of the starting resistor when the DC voltage of the converter station meets the voltage fluctuation condition, and the control of the converter station unlocking include: Real-time measurement of the DC bus voltage of the main converter station; When the DC bus voltage of the main converter station meets the first voltage fluctuation condition, the starting resistor between the main converter station and the AC power grid is removed, and the main converter station is controlled to be unlocked to establish the DC voltage of the first starting area; When the DC voltage in the first starting area meets the second voltage fluctuation condition, the slave converter station and the converter station in the second starting area are controlled to be unlocked.

6. The method according to claim 5, characterized in that When the DC voltage of the first starting area meets the second voltage fluctuation condition, controlling the converter station of the second starting area to unlock includes: When the DC voltage in the first starting area meets the second voltage fluctuation condition, the part of the DC converter close to the first starting area is controlled to start, and the converter station in the second starting area is not unlocked; After the DC converter establishes the internal AC voltage, the DC converter controls the part close to the second starting area to start, so as to establish the DC voltage of the second starting area; When the DC voltage in the second starting area meets the third voltage fluctuation condition, the converter station in the second starting area is controlled to be unlocked.

7. The method according to claim 6, characterized in that After the DC converter establishes the internal AC voltage, the DC converter controls the part close to the second start-up area to start, and establishing the DC voltage in the second start-up area includes: Internal AC voltage of the real-time strategy DC converter; When the internal AC voltage meets the fourth voltage fluctuation condition, the portion of the DC converter close to the second starting area is controlled to start, so as to establish the DC voltage in the second starting area.

8. A multi-terminal DC power grid system operation control device, characterized in that: include: A starting resistance input control module is used to input a starting resistance between the converter station and the AC grid when the DC grid is connected to the AC grid; The converter station start-up control module is used to measure the DC voltage of the converter station in real time. When the DC voltage of the converter station meets the voltage fluctuation condition, the start-up resistor is cut off and the converter station is started.

9. A multi-terminal DC power grid system operation control system, characterized in that: The device comprises a memory storing computer executable instructions and a processor, and when the computer executable instructions are executed by the processor, the device executes the multi-terminal DC power grid system operation control method as described in any one of claims 4 to 7.

10. A readable storage medium, characterized in that: A computer executable program is stored, and when the program is executed, the multi-terminal DC power grid system operation control method as described in any one of claims 4 to 7 can be implemented.

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