Multi-terminal direct-current power grid system and black-start control method thereof

Abstract

The invention discloses a multi-terminal direct-current power grid system and a black-start control method thereof, and the system is connected with a first grid-side converter station and a second grid-side converter station through a direct-current converter. The first grid-side converter station is charged through an alternating-current power grid connected with the first grid-side converter station so as to provide power required by black start, and after the first grid-side converter station is unlocked, alternating-current voltage in the direct-current converter is established through closed-loop control, so that the second grid-side converter station is controlled to be unlocked. According to the black-start control method provided by the invention, the support voltage can be stably provided under the condition of power loss of the whole network through coordinated control of the converter stations in the system; the voltage is gradually transmitted to the second grid-side converter station by starting and unlocking the first grid-side converter station, and the method adapts to a complex multi-terminal direct-current power grid structure.

Description

Technical Field

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

[0002] Multi-Terminal HVDC (MTDC) is a high-voltage direct current (HVDC) grid structure that connects multiple converter stations. It is typically used to enhance the interconnection, stability, and energy transmission efficiency between power systems in different regions.

[0003] A black start is the process of gradually restoring normal power to the system after a complete power outage, utilizing self-starting units within the system or external power sources. This process, which does not rely on other network resources, involves starting self-starting generators, which in turn drive non-self-starting units, ultimately restoring the entire system. This is crucial for minimizing losses caused by power outages.

[0004] The application of black start technology in multi-terminal DC grids is relatively complex. In a multi-terminal DC grid, it is necessary to coordinate the restart process of multiple converter stations, control systems, and related equipment. Currently, the startup of converter stations often relies on energy storage devices, but energy storage capacity is limited and cannot support the black start requirements of large-scale, multi-terminal systems. In particular, in long-distance, multi-node DC systems, larger-capacity energy storage devices are required to maintain system stability. In addition, multi-terminal DC grids involve the synchronous startup and control coordination of multiple converter stations. In the event of a power outage, the system stability is poor and is prone to problems such as voltage oscillation and power imbalance. Communication and coordination between converter stations may be affected by unstable voltage during the startup process, resulting in delayed or unstable control system response. Currently, there is still a lack of black start control strategies that can be stably applied to multi-terminal DC grids. Summary of the Invention

[0005] Based on this, the present invention proposes a multi-terminal DC power grid system and its black start control method. The DC converter is used to flexibly adjust the system voltage flow. The AC grid provides the power required for the black start of the multi-terminal DC power grid, and each converter station in the system is gradually unlocked to complete the black start of the multi-terminal DC power grid.

[0006] In a first aspect, the present invention provides a multi-terminal DC power grid system, comprising a first grid-side converter station, a second grid-side converter station, and a DC converter connecting the first grid-side converter station and the second grid-side converter station;

[0007] The first grid-side converter station is connected to an AC grid that provides power required for black start, and the second grid-side converter station is connected to a grid-connected load.

[0008] Furthermore, the DC converter is a multi-port DC converter, the first grid-side converter station includes a first converter station and a second converter station, and the second grid-side converter station includes a third converter station and a fourth converter station;

[0009] The first converter station, the second converter station, the third converter station and the fourth converter station are connected to different ports of the DC converter through transmission lines;

[0010] The first converter station is used to establish the internal AC bus voltage of the DC converter, the second converter station is used to adjust the DC power flow of the DC converter, and the third and fourth converter stations are used to control the AC voltage of the grid connection point of the grid-connected load.

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

[0012] controlling the AC power grid to charge the first grid-side converter station;

[0013] Acquiring a first charging state of the first grid-side converter station, and controlling the first grid-side converter station to unlock according to the first charging state;

[0014] Establishing an internal AC voltage of the DC converter through the first grid-side converter station;

[0015] The second grid-side converter station is unlocked according to the internal AC voltage control, completing the grid connection of the grid-connected load and the multi-terminal DC grid system.

[0016] Furthermore, obtaining a first charging state of the first grid-side converter station and controlling the first grid-side converter station to unlock according to the first charging state includes:

[0017] Obtaining the DC side voltage of the first grid-side converter station;

[0018] When the DC side voltage of the first grid-side converter station reaches a first voltage value, the first grid-side converter station is controlled to be unlocked.

[0019] Furthermore, establishing the internal AC voltage of the DC converter through the first grid-side converter station includes:

[0020] Obtaining the DC side voltage of the first grid-side converter station;

[0021] When the DC side voltage of the first grid-side converter station reaches a second voltage value, the internal closed-loop controller of the DC converter is started to establish the internal AC voltage of the DC converter.

[0022] Furthermore, the first grid-side converter station includes a first converter station and a second converter station, and establishing the internal AC voltage of the DC converter through the first grid-side converter station includes:

[0023] Obtaining the DC side voltage of the first converter station;

[0024] When the DC side voltage of the first converter station reaches a second voltage value, the internal closed-loop controller of the DC converter is started to establish the internal AC voltage of the DC converter.

[0025] Furthermore, the first grid-side converter station includes a first converter station and a second converter station, the DC converter is a multi-port DC converter, the first converter station and the second converter station are respectively connected to a first port and a second port of the DC converter, and controlling the second grid-side converter station to unlock according to the internal AC voltage includes:

[0026] After the DC converter establishes an internal AC voltage, an internal closed-loop controller controlling the second port in the DC converter is started, so that the second converter station regulates the DC power flow between the first port and the second port, and controls the DC converter to provide a DC voltage to the second grid-side converter station;

[0027] When the DC voltage of the second grid-side converter station reaches a third voltage value, the second grid-side converter station is controlled to be unlocked.

[0028] Furthermore, the second grid-side converter station includes a third converter station and a fourth converter station, and controlling the unlocking of the second grid-side converter station according to the internal AC voltage includes:

[0029] controlling the DC converter to provide DC voltage to the third converter station and the fourth converter station;

[0030] When the DC voltages of the third converter station and the fourth converter station reach a third voltage value, the third converter station and the fourth converter station are controlled to be unlocked.

[0031] In a third aspect, the present invention provides a multi-terminal DC power grid system black start control device, comprising:

[0032] A charging control module, configured to control the AC power grid to charge the first grid-side converter station;

[0033] a first unlocking module, configured to obtain a first charging state of the first grid-side converter station and control the unlocking of the first grid-side converter station according to the first charging state;

[0034] an AC voltage establishing module, configured to establish an internal AC voltage of the DC converter via the first grid-side converter station;

[0035] The second unlocking module is used to control the unlocking of the second grid-side converter station according to the internal AC voltage to complete the grid connection of the grid-connected load and the multi-terminal DC power grid system.

[0036] In a fourth aspect, the present invention provides a multi-terminal DC power grid system black start 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 black start control method provided in the second aspect.

[0037] 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 black start control method provided in the second aspect.

[0038] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0039] The present invention provides a multi-terminal DC power grid system and a black start control method thereof. The system connects a first grid-side converter station and a second grid-side converter station via a DC converter. When black start control is performed on the system, the first grid-side converter station is charged via the AC power grid connected to the first grid-side converter station to provide the power required for the black start. After the first grid-side converter station is unlocked, an AC voltage is established inside the DC converter through closed-loop control, thereby controlling the unlocking of the second grid-side converter station, completing the grid connection of the grid-connected load connected to the second grid-side converter station with the system, and realizing the black start of the system. Through coordinated control of each converter station in the system, a stable support voltage can be provided in the event of a power outage in the entire grid. Further utilizing the isolation function and interconnected feeding characteristics of the multi-port DC converter, the voltage is gradually transmitted to other converter stations in the system by starting and unlocking the first grid-side converter station, so as to establish the DC voltage of the system and adapt to complex multi-terminal DC power grid structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0041] Figure 1 This is a schematic diagram of the structure of a multi-terminal DC power grid system provided by an embodiment of the present invention;

[0042] Figure 2 This is a topology diagram of a four-terminal DC / DC converter provided by an embodiment of the present invention;

[0043] Figure 3 is a schematic structural diagram of another multi-terminal DC power grid system provided by an embodiment of the present invention;

[0044] Figure 4 This is a flowchart of a black start control method for a multi-terminal DC power grid system provided by an embodiment of the present invention;

[0045] Figure 5 The embodiment of the present invention provides Figure 3 Black start simulation results of multi-terminal DC grid system:

[0046] Figure 6 This is a structural diagram of a black start control device for a multi-terminal DC power grid system provided by an embodiment of the present invention;

[0047] Figure 7 This is an architecture diagram of a black start control system for a multi-terminal DC power grid system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0049] A multi-terminal converter (MTC) is a power electronic device that supports multiple DC or AC ports and enables energy exchange between multiple DC or AC grids. It is widely used in multi-terminal DC grids (MTDC) and distributed energy systems. It offers flexibility and efficiency, supporting multi-directional power transmission. By interconnecting multiple DC transmission ports, MTCs are used in scenarios such as renewable energy grid integration and urban power supply. In multi-terminal systems, the voltage level of each port must be controlled to meet the requirements of devices at different voltage levels while ensuring stable power transmission.

[0050] The present invention takes into account the deficiencies of the black start control strategy of the multi-terminal DC grid system, utilizes the DC converter to flexibly adjust the system voltage flow, and uses the AC grid to provide the power required for the black start of the multi-terminal DC grid. It gradually unlocks each converter station in the system to complete the black start of the multi-terminal DC grid.

[0051] See Figure 1 An embodiment of the present invention provides a multi-terminal DC power grid system 100, including a first grid-side converter station 102, a second grid-side converter station 104, and a DC converter 106 connecting the first grid-side converter station 102 and the second grid-side converter station 104.

[0052] Specifically, the first grid-side converter station 102 is connected to the AC grid 200, which provides the power required for the black start. Its main function is to convert AC power into DC power, providing initial DC voltage support for the entire system. During the black start, the stability and controllability of the output power of the first grid-side converter station 102 are crucial. It is responsible for starting and stabilizing the voltage of the entire DC system. The second grid-side converter station 104 is connected to the grid-connected load 300 and is responsible for converting DC power into AC power and injecting it into the grid. During the black start process, the role of the second grid-side converter station is to provide stable AC power to the connected load and feed power back to the system when needed. The DC converter 106 is responsible for achieving power transmission between different voltage levels and plays a role in regulation and optimization in the system. It generally steps up or down the voltage according to voltage requirements, completes the interconnection and power feed on both sides of the converter, and thus achieves black start control of the system.

[0053] In a further embodiment, the DC converter 106 can adopt a multi-terminal DC converter, which usually includes several ports and a common AC bus. Each port corresponds to a converter station. For ports with AC transformation requirements, AC transformers and AC circuit breakers can also be set at the ports.

[0054] In a further embodiment, the AC sides of multiple ports of the multi-terminal DC converter need to be connected to the internal common bus, and the stability of the AC voltage of the bus is particularly important. Therefore, one port can be designated as a voltage port to maintain the stability of the internal AC bus voltage, and the other ports are used to implement specific control strategies, such as controlling DC power or voltage.

[0055] The multi-terminal DC converter can flexibly adjust the voltage flow of the system, and other ports can continue to operate when one end is shut down.

[0056] In some embodiments, the multi-terminal DC converter can be connected to DC grids of different voltage levels.

[0057] In some embodiments, in order to improve the reliability of the multi-port DC converter, in addition to the voltage port, a port can be designated as a voltage backup port so that it also has the ability to maintain a constant AC bus voltage. When the voltage port cannot continue to maintain the bus voltage due to a fault, the backup voltage port replaces the voltage port to enable the entire system to maintain normal operation.

[0058] In a further embodiment, based on a multi-port DC converter, the first grid-side converter station of the embodiment of the present invention may include a first converter station and a second converter station, the second grid-side converter station includes a third converter station and a fourth converter station, and the first converter station, the second converter station, the third converter station and the fourth converter station are connected to different ports of the multi-port DC converter through transmission lines.

[0059] The first converter station is used to establish the internal AC bus voltage of the DC converter. The port connected to the first converter station is the voltage port. The second converter station is used to adjust the DC current of the DC converter. The third and fourth converter stations are used to control the AC voltage of the grid-connected point of the grid-connected load.

[0060] For example, Figure 2 The present invention illustrates a multi-port DC converter provided by an embodiment of the present invention. Specifically, a four-port DC / DC converter is used as an example, including ports 1 to 4. Ports 3 and 4 are both equipped with transformers and AC circuit breakers (CB3 and CB4) between the transformer module and the busbar to match the DC voltage connected to the port and the converter station with the common AC bus voltage.

[0061] Taking port 1 as an example, the converter part inside it consists of 6 submodules (SM) forming a bridge arm. Each submodule includes a transistor and a diode connected in parallel. That is, the converter part inside the port consists of transistors S1_1~S6_1 and 6 diodes. A capacitor C is connected in parallel at the end of the converter close to the DC side. 1dc The structures of port 2 to port 4 are similar to those of port 1 and will not be described here.

[0062] based on Figure 2 Schematic diagram of a four-port DC / DC converter. Figure 3 The diagram illustrates a multi-terminal DC power grid system provided by an embodiment of the present invention, including a four-port DC / DC converter and four converter stations VSC1 to VSC4. The converter stations VSC1 to VSC4 are respectively connected to ports Port1 to Port4 of the four-port DC / DC converter through transmission lines.

[0063] Converter stations VSC1 and VSC2 are used to connect two 690kV AC grids, with a DC voltage level of ±400kV. Converter stations VSC3 and VSC4 are used to connect two geographically different wind farms WF1 and WF2 to the multi-terminal DC grid, with DC voltage levels of ±300V and ±150V, respectively. Figure 3 The DC HUB (shown in the figure) serves as a central hub to connect four converter stations with different voltage levels.

[0064] To provide a stable DC voltage for Port 1, converter station VSC1 controls the DC voltage of transmission line DC cable 1. VSC2 controls the DC voltage of transmission line DC cable 2, and regulates the DC power flow through Port 1 and Port 2 via Port 2. Converter stations VSC3 and VSC4 control the AC voltage at the wind farm's grid connection point. The DC hub controls the DC voltage of the connected DC transmission lines through Ports 3 and 4, providing a stable DC voltage for converter stations VSC3 and VSC4.

[0065] Based on the above control strategy, the DC grid can absorb the maximum wind power generated by the wind farm. At the same time, the system can flexibly allocate the power transmitted to converter stations VSC1 and VSC2. Converter station VSC1 and its connected port Port1 can be used as the power balancing point of the entire system.

[0066] See Figure 4 Based on the multi-terminal DC power grid systems provided in the above embodiments, an embodiment of the present invention provides a black start control method for a multi-terminal DC power grid system, comprising the following steps:

[0067] Step S410: Control the AC power grid to charge the first grid-side converter station.

[0068] In this step, when the multi-terminal DC grid loses power, the AC grid connected to the first grid-side converter station first charges the DC capacitors in the first grid-side converter station and its transmission lines. Because the DC converter also includes a converter, the AC grid simultaneously charges the DC capacitors within the DC converter when charging the first grid-side converter station.

[0069] Specifically, during a black start, the AC grid typically provides initial voltage support to the DC grid through the first grid-side converter station, gradually restoring the DC system's power supply capacity. The first grid-side converter station gradually increases the DC bus voltage, monitoring the voltage rise rate through a control system to ensure that the voltage rises within a safe range. The first grid-side converter station gradually increases the conduction angle or pulse width to adjust the DC bus voltage's rise rate, ensuring that it smoothly reaches the target voltage.

[0070] In a further embodiment, to avoid voltage fluctuations or power oscillations, the control system of the converter station generally adopts a closed-loop control method to dynamically adjust the output of the converter according to the feedback signal of the DC bus voltage.

[0071] In a further embodiment, to avoid excessive inrush current during initial charging, a starting resistor can be installed between the AC grid and the converter station. This resistor limits the initial charging current, thereby preventing system instability caused by excessive transient current. The starting resistor is installed during the initial charging phase and removed after the DC bus voltage at the converter station reaches a certain value.

[0072] Step S420: Obtain a first charging state of the first grid-side converter station, and control the first grid-side converter station to be unlocked according to the first charging state.

[0073] Specifically, step S420 includes the following steps:

[0074] Step S421. Obtaining the DC side voltage of the first grid-side converter station;

[0075] Step S422: When the DC side voltage of the first grid-side converter station reaches a first voltage value, the first grid-side converter station is controlled to be unlocked.

[0076] In this step, when the DC-side voltage at the first grid-side converter station reaches a first voltage value, the internal closed-loop controller is triggered to activate, controlling the unlocking of the first grid-side converter station and controlling its DC voltage to continue rising to the rated value. After unlocking, the converter station gradually increases its power output, begins to establish a normal current and voltage relationship with the DC bus, and continues to provide power support to ensure the smooth unlocking of other converter stations and the full startup of the system. During this stage, the converter station's control system typically implements closed-loop control to ensure stable DC-side voltage.

[0077] Step S430: Establishing the internal AC voltage of the DC converter through the first grid-side converter station.

[0078] In this step, the first grid-side converter station is configured to generate the required internal AC voltage. When the DC voltage of the transmission line connected to the first grid-side converter station reaches the rated value, the controller of the port connected to the DC converter is activated to begin building the AC voltage within the converter. Specifically, pulse width modulation (PWM) technology can be used to generate the AC voltage by controlling the switching state of the converter. The PWM signal adjusts the converter output to form the required AC voltage waveform.

[0079] In a further embodiment, step S430 includes the following steps:

[0080] Step S431. Obtaining the DC side voltage of the first grid-side converter station;

[0081] Step S432: When the DC side voltage of the first grid-side converter station reaches a second voltage value, the internal closed-loop controller of the DC converter is started to establish the internal AC voltage of the DC converter.

[0082] Specifically, for a multi-port DC converter, the first converter station and the second converter station of the first grid-side converter station are respectively connected to the first port and the second port of the DC converter, and the DC voltage is provided by the first converter station. When the DC side voltage of the first converter station reaches the rated value, the internal closed-loop controller of the DC converter is started to establish the internal common AC bus voltage of the DC converter.

[0083] Step S440: Control the second grid-side converter station to unlock according to the internal AC voltage, and complete the grid-connected load and the multi-terminal DC grid system.

[0084] In this step, after the converter establishes the internal AC voltage, it continues to provide DC voltage to the second grid-side converter station. When the DC side voltage of the second grid-side converter station reaches the third voltage value, the second grid-side converter station is controlled to be unlocked, allowing the second grid-side converter station to enter the working state.

[0085] In a further embodiment, the first grid-side converter station includes a first converter station and a second converter station, the DC converter is a multi-port DC converter, the first converter station and the second converter station are respectively connected to a first port and a second port of the DC converter, and step S440 includes the following steps:

[0086] Step S441. After the DC converter establishes an internal AC voltage, the internal closed-loop controller of the second port of the DC converter is activated, so that the second converter station regulates the DC power flow between the first port and the second port, and controls the DC converter to provide a DC voltage to the second grid-side converter station.

[0087] Step S442: When the DC voltage of the second grid-side converter station reaches a third voltage value, the second grid-side converter station is controlled to be unlocked.

[0088] Specifically, after the DC converter's internal AC voltage stabilizes, the control system activates the second port's internal closed-loop controller. This controller monitors the DC current and voltage between the first and second ports in real time and adjusts them based on the target voltage. The closed-loop controller receives the DC current and voltage information between the first and second ports, compares them with set values, and calculates the required control signal. Based on this feedback, the controller adjusts the DC converter's switching state, controlling the magnitude and direction of the DC power flow to meet load demand. During this adjustment process, the second port's closed-loop controller ensures a stable DC voltage is provided to the second grid-side converter station.

[0089] In a further embodiment, the second grid-side converter station includes a third converter station and a fourth converter station, and the third converter station and the fourth converter station need to be unlocked only when the DC voltages of the third converter station and the fourth converter station reach a rated value.

[0090] After the second grid-side converter station is unlocked, it begins to build up AC voltage, preparing for load grid connection and gradually delivering active power. As the load connected power increases, the power transmitted to the AC grid side also increases, eventually completing the load connection to the multi-terminal DC grid.

[0091] Below Figure 2 and 3 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.

[0092] The AC grid connected to converter stations VSC1 and VSC2 first charges the DC capacitors of converter stations VSC1 and VSC2 and transmission lines DCcable1 and DC cable2. When the DC voltage at the output of converter stations VSC1 and VSC2 reaches 0.8 pu, their internal closed-loop controllers activate, bringing the DC side voltage of converter stations VSC1 and VSC2 to the rated value and controlling the unlocking of converter stations VSC1 and VSC2. The DC voltage of transmission line DC cable1 continues to be monitored. When it reaches its rated value, the internal closed-loop controller of port 1 of the four-port DC / DC converter activates, beginning to establish the common AC bus voltage within the four-port DC / DC converter.

[0093] After the internal AC bus voltage of the four-port DC / DC converter is established, the internal controller of control port Port2 starts to regulate the DC power flow between ports Port1 and Port2. The converter continues to provide DC voltage to converter stations VSC3 and VSC4. When the DC side voltage of converter stations VSC3 and VSC4 reaches the rated value, the control stations VSC3 and VSC4 are unlocked, and the converter stations begin to establish internal DC voltage. When the DC voltage of converter stations VSC3 and VSC4 stabilizes at their respective reference values, the AC voltage is triggered, and wind farms WF1 and WF2 are connected to the grid.

[0094] Figure 5 (a) and Figure 5 (b) indicates the Figure 3 The simulation results of the black start control of the multi-terminal DC grid are shown in the figure. vsc1 and V vsc2 Represents the DC side voltage of converter stations VSC1 and VSC2, V sport1 Indicates the AC side voltage (effective value) of port Port1, P port2 Indicates the DC power flowing through port Port2, V port3 and V port4 Represents the DC voltage of Port3 and Port4 respectively, V svsc3 and V svsc4 Respectively represent the AC voltage (effective value) of converter stations VSC3 and VSC4.

[0095] like Figure 5 As shown in (a), the system establishes a DC voltage for converter stations VSC1 and VSC2 through the charging action of the AC grid from 0s to 0.3s. From 0.4s to 0.6s, converter station VSC1 establishes a common AC bus voltage within the four-terminal DC / DC converter through port Port1. At 0.8s, power control begins through port Port2.

[0096] like Figure 5 As shown in (b), at 1.2 seconds, DC voltage is established at ports Port3 and Port4. Between 1.2 and 1.8 seconds, converter stations VSC3 and VSC4 start up and establish AC voltage, preparing for wind farm connection. However, before converter stations VSC3 and VSC4 establish AC voltage, wind farms WF1 and WF2 are not connected to the grid and, therefore, do not output active power. As wind farm power increases, the power transmitted to the AC grid also increases.

[0097] The above-mentioned embodiments provide a multi-terminal DC power grid system and a black start control method thereof. The system connects a first grid-side converter station and a second grid-side converter station via a DC converter. When performing black start control on the system, the first grid-side converter station is charged via the AC power grid connected to the first grid-side converter station to provide the power required for the black start. After the first grid-side converter station is unlocked, an AC voltage is established within the DC converter through closed-loop control, thereby controlling the unlocking of the second grid-side converter station, completing the grid connection of the grid-connected load connected to the second grid-side converter station with the system, and achieving a black start of the system. Through coordinated control of each converter station in the system, a stable support voltage can be provided in the event of a complete grid power outage. Further utilizing the isolation function and interconnected feeding characteristics of the multi-port DC converter, the voltage is gradually transmitted to other converter stations in the system by starting and unlocking the first grid-side converter station to establish the DC voltage of the system, thereby adapting to complex multi-terminal DC power grid structures.

[0098] The above embodiments provide a method that can be implemented in various forms of devices. Therefore, the present invention also discloses a multi-terminal DC grid system operation control device corresponding to the above method. Specific embodiments are given below for detailed description.

[0099] like Figure 6 As shown, one embodiment of the present invention provides a black start control device for a multi-terminal DC power grid system, comprising:

[0100] A charging control module 602 is configured to control the AC power grid to charge the first grid-side converter station;

[0101] A first unlocking module 604 is configured to obtain a first charging state of the first grid-side converter station and control the unlocking of the first grid-side converter station according to the first charging state;

[0102] an AC voltage establishing module 606, configured to establish an internal AC voltage of the DC converter via the first grid-side converter station;

[0103] The second unlocking module 608 is configured to control the unlocking of the second grid-side converter station according to the internal AC voltage, thereby completing the grid connection of the grid-connected load to the multi-terminal DC power grid system.

[0104] The device provided in the embodiment of the present application has the same implementation principle and technical effects as those in the aforementioned method embodiment. For the sake of brief description, for matters not mentioned in the device embodiment, reference can be made to the corresponding content in the aforementioned method embodiment.

[0105] 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 steps in the process. Figure 1 Schematic diagram of one or more processes and / or structures Figure 1 These 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 the instruction device, which implements the function 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, thereby providing instructions for implementing the process in the process. Figure 1 The flow or flows and / or structures illustrate the steps of the functions specified in one block or multiple blocks.

[0106] The following embodiments illustrate this method using a computer device as an example. It is understood that the computer device may be any device with computing and processing capabilities, including, but not limited to, a server or a personal laptop. In one embodiment, the computer device may be an application server, which may be a server for running the application under test.

[0107] See Figure 7 , which shows a hardware block diagram of a multi-terminal DC grid system black start control system. The control system is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, 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 assistants, cellular phones, smartphones, 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 claimed herein.

[0108] like Figure 7 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;

[0109] 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;

[0110] The processor 1 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention;

[0111] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory;

[0112] The memory stores a program, and the processor can call the program stored in the memory, wherein the program is used to implement various processing flows of the aforementioned black start control solution for the multi-terminal DC power grid system.

[0113] 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 the various processing flows of the multi-terminal DC power grid system black start control solution provided in the above embodiment and / or any possible implementation method in combination with the embodiment.

[0114] The above embodiments have described the invention in particular detail with respect to possible scenarios, and those skilled in the art will recognize that the invention can be practiced through other embodiments. The specific naming of components, 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 invention may have different names, forms, or procedures. The system may be implemented through a combination of hardware and software (as described), entirely through hardware elements, or entirely through software elements. The specific division of functions between the various system components described herein is exemplary only and not mandatory; rather, 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.

[0115] Those skilled in the art will appreciate that the various steps of the method disclosed above can be implemented by a general-purpose computing device. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Alternatively, they can be implemented using program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. Thus, the embodiments disclosed herein are not limited to any specific combination of hardware and software.

[0116] The programs executable by these computing devices (also referred to as programs, software, software applications, or code) include machine instructions for programmable processors and 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, apparatus, and / or device (e.g., a magnetic disk, an optical disk, a memory, a 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.

[0117] Certain aspects of the present invention include the 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 in software, they can be downloaded, stored on different platforms used by various operating systems, and operated from the platforms.

[0118] 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 figure, or combine certain components, or have a different arrangement of components.

[0119] Some embodiments may be described using the terms "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 in this context.

[0120] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "possible design" 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 different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0121] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0122] 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 can still be modified, or some of the technical features thereof can 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, characterized in that: It includes a first grid-side converter station, a second grid-side converter station, and a DC converter connecting the first grid-side converter station and the second grid-side converter station; The first grid-side converter station is connected to an AC grid that provides power required for a black start, and the second grid-side converter station is connected to a grid-connected load.

2. The system according to claim 1, characterized in that The DC converter is a multi-port DC converter, the first grid-side converter station includes a first converter station and a second converter station, and the second grid-side converter station includes a third converter station and a fourth converter station; The first converter station, the second converter station, the third converter station and the fourth converter station are connected to different ports of the DC converter through transmission lines; The first converter station is used to establish the internal AC bus voltage of the DC converter, the second converter station is used to adjust the DC power flow of the DC converter, and the third converter station and the fourth converter station are used to control the AC voltage of the grid-connected point of the grid-connected load.

3. A black start control method for a multi-terminal DC power grid system, characterized in that: Used to control the black start of the multi-terminal DC power grid system according to any one of claims 1 to 2, comprising: Controlling the AC power grid to charge the first grid-side converter station; Acquire a first charging state of the first grid-side converter station, and control the first grid-side converter station to be unlocked according to the first charging state; Establishing an internal AC voltage of the DC converter through the first grid-side converter station; The second grid-side converter station is unlocked according to the internal AC voltage to complete the grid connection of the grid-connected load to the multi-terminal DC power grid system.

4. The method according to claim 3, characterized in that The acquiring the first charging state of the first grid-side converter station and controlling the unlocking of the first grid-side converter station according to the first charging state includes: Obtaining a DC side voltage of a first grid-side converter station; When the DC side voltage of the first grid-side converter station reaches a first voltage value, the first grid-side converter station is controlled to be unlocked.

5. The method according to claim 3, characterized in that: The establishing of the internal AC voltage of the DC converter by the first grid-side converter station comprises: Obtaining a DC side voltage of a first grid-side converter station; When the DC side voltage of the first grid-side converter station reaches a second voltage value, an internal closed-loop controller of the DC converter is started to establish an internal AC voltage of the DC converter.

6. The method according to claim 3, characterized in that The first grid-side converter station includes a first converter station and a second converter station, and establishing the internal AC voltage of the DC converter through the first grid-side converter station includes: Acquiring a DC side voltage of the first converter station; When the DC side voltage of the first converter station reaches a second voltage value, an internal closed-loop controller of the DC converter is controlled to start, so as to establish an internal AC voltage of the DC converter.

7. The method according to claim 3, characterized in that The first grid-side converter station includes a first converter station and a second converter station, the DC converter is a multi-port DC converter, the first converter station and the second converter station are respectively connected to a first port and a second port of the DC converter, and controlling the second grid-side converter station to unlock according to the internal AC voltage includes: After the DC converter establishes the internal AC voltage, the internal closed-loop controller of the second port in the DC converter is started, so that the second converter station regulates the DC power flow between the first port and the second port, and controls the DC converter to provide a DC voltage for the second grid-side converter station; When the DC voltage of the second grid-side converter station reaches a third voltage value, the second grid-side converter station is controlled to be unlocked.

8. A black start control device for a multi-terminal DC power grid system, characterized in that: include: A charging control module, used for controlling the AC power grid to charge the first grid-side converter station; A first unlocking module, used for acquiring a first charging state of a first grid-side converter station, and controlling the first grid-side converter station to be unlocked according to the first charging state; An AC voltage establishing module, used to establish an internal AC voltage of the DC converter through the first grid-side converter station; The second unlocking module is used to control the unlocking of the second grid-side converter station according to the internal AC voltage to complete the grid connection of the grid-connected load and the multi-terminal DC power grid system.

9. A black start control system for a multi-terminal DC power grid 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 black start control method for a multi-terminal DC power grid system as claimed in any one of claims 3 to 7.

10. A readable storage medium, characterized in that: A computer executable program is stored, and when the program is executed, the black start control method for a multi-terminal DC power grid system as described in any one of claims 3 to 7 can be implemented.

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