Topological structure for sending out of large-scale new energy base through direct current system and control method of topological structure

Abstract

The invention discloses a topological structure for transmission of a large-scale new energy base through a direct current system and a control method thereof, the topological structure can adopt a single-pole topology or a double-pole topology, the single-pole topology is taken as an example, the single-pole topology comprises a transmitting end converter station, a receiving end converter station, a first cable and a second cable, the transmitting end converter station is used for accessing the new energy base, and the receiving end converter station is used for accessing the new energy base; the sending-end converter station comprises a commutation converter and a first voltage source converter which are cascaded, and is further provided with a static synchronous compensator; the receiving end converter station is used for accessing a receiving end power grid; the receiving end converter station comprises a second voltage source converter and a third voltage source converter which are cascaded, and a low-voltage end is further provided with a grounding point; the first cable is used for connecting the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station; and the second cable is used for connecting the low-voltage end of the sending-end converter station and the low-voltage end of the receiving-end converter station. The manufacturing cost of equipment of the whole system can be reduced, and the system reliability is improved.

Description

Technical Field

[0001] This invention belongs to the field of DC power transmission in power systems, and specifically relates to a topology and control method for large-scale new energy bases to transmit power via DC systems. Background Technology

[0002] Economic transmission schemes for large-scale desert solar, wind, and energy storage bases and large-capacity offshore wind power clusters have become increasingly important research areas and constraints. New topologies are urgently needed for long-distance DC transmission from large-scale desert renewable energy bases and large-capacity offshore wind power clusters. Traditional AC grid connection suffers from short transmission distances, the need for reactive power compensation equipment, and high line losses. LCC ultra-high voltage (UHV) transmission cannot solve the problem of lack of grid-connected AC power for isolated renewable energy transmission at the sending end. Flexible DC UHV transmission is limited by high equipment costs and the lack of large-scale use of high-voltage, high-current, and high-capacity IGBTs. Therefore, the demand for DC solutions suitable for large-scale isolated renewable energy transmission with capacities exceeding GW (gigawatts) is growing rapidly. Summary of the Invention

[0003] The purpose of this invention is to provide a topology and control method for large-scale new energy bases to transmit power via a DC system, which can reduce the overall equipment cost and improve system reliability.

[0004] To achieve the above objectives, the solution of the present invention is:

[0005] A topology for transmitting power from a large-scale new energy base via a DC system, employing a unipolar topology; including,

[0006] The sending-end converter station is used to connect to the new energy base; the sending-end converter station includes a cascaded phase converter and a first voltage source converter, the DC low voltage output of the phase converter is connected to the DC high voltage output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches in parallel on the DC side; the phase converter is also equipped with a static synchronous compensator;

[0007] The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second and third voltage source converters are equipped with bypass switches connected in parallel on their DC sides. The low-voltage end of the receiving-end converter station is also equipped with a grounding point.

[0008] A first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station; and,

[0009] The second cable is used to connect the low-voltage end of the sending-end converter station and the low-voltage end of the receiving-end converter station.

[0010] The aforementioned second and third voltage source converters both employ modular multilevel converters, which are composed of full-bridge sub-modules or full-half hybrid modules.

[0011] The control method for the topology used in the transmission of large-scale new energy bases via DC systems, as described above, includes:

[0012] During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked.

[0013] During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold.

[0014] During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

[0015] During the charging phase, the bypassing of the phase-commutation converter and the second voltage source converter includes controlling the closing of the bypass switch of the phase-commutation converter to achieve the DC-side bypass state of the phase-commutation converter; and controlling the closing of the bypass switch of the second voltage source converter to achieve the DC-side bypass state of the second voltage source converter.

[0016] During the charging phase, the first voltage source converter and the third voltage source converter are unlocked, including...

[0017] The first voltage source converter is charged through the DC side, while the second and third voltage source converters are charged through the receiving-end power grid.

[0018] Unlock the third voltage source converter to establish DC voltage, and unlock the first voltage source converter to establish AC bus voltage at the sending end.

[0019] During the grid-connected power output phase, when the grid-connected power output is higher than the power threshold, the first voltage source converter and the commutator are put into operation for power transmission, including unlocking the commutator, unlocking the second voltage source converter, and controlling the bypass switch of the commutator and the bypass switch of the second voltage source converter to be disconnected.

[0020] This also includes,

[0021] When the commutator fails or is under maintenance, the first voltage source converter is put into operation and switched to single valve group operation.

[0022] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the control method for the topology of a large-scale new energy base transmitting power via a DC system as described above.

[0023] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the control method for the topology of a large-scale new energy base transmitting power via a DC system as described above.

[0024] A topology for transmitting power from a large-scale new energy base via a DC system is proposed, employing a bipolar topology. It includes a first pole and a second pole, both having identical structures.

[0025] A sending-end converter station is used for connection to a new energy base; the sending-end converter station includes cascaded phase converters and a first voltage source converter, the low-voltage DC output of the phase converter is connected to the high-voltage DC output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches connected in parallel on their DC sides; the phase converter is also equipped with a static synchronous compensator; and,

[0026] The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second voltage source converter and the third voltage source converter are equipped with bypass switches in parallel on their DC sides.

[0027] It also includes,

[0028] The first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station in the first pole.

[0029] The second cable has its first end connected to the low-voltage end of the first pole's transmitting-end converter station and the high-voltage end of the second pole's transmitting-end converter station, and its second end connected to the low-voltage end of the first pole's receiving-end converter station and the high-voltage end of the second pole's receiving-end converter station. This second end is also equipped with a grounding point.

[0030] The third cable is used to connect the low-voltage end of the second pole's transmitting-end converter station and the low-voltage end of the second pole's receiving-end converter station.

[0031] The aforementioned second and third voltage source converters both employ modular multilevel converters, which are composed of full-bridge sub-modules or full-half hybrid modules.

[0032] The control methods for the first and second poles are the same, including:

[0033] During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked.

[0034] During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold.

[0035] During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

[0036] During the charging phase, the bypassing of the phase-commutation converter and the second voltage source converter includes controlling the closing of the bypass switch of the phase-commutation converter to achieve the DC-side bypass state of the phase-commutation converter; and controlling the closing of the bypass switch of the second voltage source converter to achieve the DC-side bypass state of the second voltage source converter.

[0037] During the charging phase, the first voltage source converter and the third voltage source converter are unlocked, including...

[0038] The first voltage source converter is charged through the DC side, while the second and third voltage source converters are charged through the receiving-end power grid.

[0039] Unlock the third voltage source converter to establish DC voltage, and unlock the first voltage source converter to establish AC bus voltage at the sending end.

[0040] During the grid-connected power output phase, when the grid-connected power output is higher than the power threshold, the first voltage source converter and the commutator are put into operation for power transmission, including unlocking the commutator, unlocking the second voltage source converter, and controlling the bypass switch of the commutator and the bypass switch of the second voltage source converter to be disconnected.

[0041] This also includes,

[0042] When the commutation converter fails or is under maintenance, the first voltage source converter is put into operation and switched to single valve group operation.

[0043] When the first voltage source converter of a certain pole fails or is under maintenance, the first voltage source converter of the opposite pole is responsible for establishing the AC voltage, and the commutation converters of the first and second poles are used to transmit active power.

[0044] This also includes,

[0045] When the reactive power capacity of the sending-end voltage source converter is insufficient to meet the reactive power required for the operation of the sending-end commutator converter, a static synchronous compensator of a certain capacity is installed for reactive power compensation.

[0046] The sending-end voltage source converter and the static synchronous compensator are responsible for filtering out the characteristic harmonics generated by the sending-end commutated converter.

[0047] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the control method for the topology of a large-scale new energy base transmitting power via a DC system as described above.

[0048] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the control method for the topology of a large-scale new energy base transmitting power via a DC system as described above.

[0049] With the above scheme, the new energy side DC converter station in this invention adopts a bipolar four-valve group structure, where each pole is a dual-valve group structure, consisting of a voltage source type MMC converter and a current source type thyristor semi-controlled converter LCC cascaded together. The bipolar can operate in symmetrical or asymmetrical states. Within a single pole, the black-start capability of the voltage source type converter is used to establish the AC voltage of the new energy power station, and then thyristor rectification is used to achieve power transmission. A bypass switch is connected in parallel between the DC terminals of each valve group to enable independent operation of each valve group after a single valve group failure.

[0050] The authentic bipolar structure, combined with the advantages of voltage source converters (black start capability) and thyristor semi-controlled converters (low cost and large capacity), reduces the overall system equipment cost and improves system reliability, making it a better topology solution for large-capacity new energy transmission. Attached Figure Description

[0051] Figure 1 This is a system architecture diagram of the bipolar symmetric topology of this invention;

[0052] Figure 2 This is a system architecture diagram of the unipolar symmetric topology of this invention.

[0053] Figure 3 This is a schematic diagram of the topology of the present invention during charging;

[0054] Figure 4 This is a state diagram of the bipolar operation of the topology structure of this invention. Detailed Implementation

[0055] This invention provides a topology for large-scale new energy bases to transmit power via a DC system, employing a unipolar topology; including,

[0056] The sending-end converter station is used to connect to the new energy base; the sending-end converter station includes a cascaded phase converter and a first voltage source converter, the DC low voltage output of the phase converter is connected to the DC high voltage output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches in parallel on the DC side; the phase converter is also equipped with a static synchronous compensator;

[0057] The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second and third voltage source converters are equipped with bypass switches connected in parallel on their DC sides. The low-voltage end of the receiving-end converter station is also equipped with a grounding point.

[0058] A first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station; and,

[0059] The second cable is used to connect the low-voltage end of the sending-end converter station and the low-voltage end of the receiving-end converter station.

[0060] The control method for this unipolar topology includes,

[0061] During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked.

[0062] During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold.

[0063] During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

[0064] This invention also provides a topology for large-scale new energy bases to transmit power via a DC system, employing a bipolar topology; it includes a first pole and a second pole, the first and second poles having identical structures, including...

[0065] A sending-end converter station is used for connection to a new energy base; the sending-end converter station includes cascaded phase converters and a first voltage source converter, the low-voltage DC output of the phase converter is connected to the high-voltage DC output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches connected in parallel on their DC sides; the phase converter is also equipped with a static synchronous compensator; and,

[0066] The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second voltage source converter and the third voltage source converter are equipped with bypass switches in parallel on their DC sides.

[0067] It also includes,

[0068] The first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station in the first pole.

[0069] The second cable has its first end connected to the low-voltage end of the first pole's transmitting-end converter station and the high-voltage end of the second pole's transmitting-end converter station, and its second end connected to the low-voltage end of the first pole's receiving-end converter station and the high-voltage end of the second pole's receiving-end converter station. This second end is also equipped with a grounding point.

[0070] The third cable is used to connect the low-voltage end of the second pole's transmitting-end converter station and the low-voltage end of the second pole's receiving-end converter station.

[0071] In this bipolar topology, the control methods for the first and second poles are the same, including:

[0072] During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked.

[0073] During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold.

[0074] During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

[0075] The technical solution of the present invention will be described in detail below through specific embodiments.

[0076] This invention provides a topology for transmitting large-scale new energy sources via a DC system, including a sending-end converter station and a receiving-end converter station connected by cables. The converters in the sending-end converter station include cascaded thyristor semi-controlled LCC converters (Line-commutated Converters) and small-capacity fully controlled VSC (Voltage Source Converters). The converters in the receiving-end converter station are composed of cascaded fully controlled VSC converters.

[0077] like Figure 2 The diagram shown is an architecture of the present invention in a unipolar symmetrical configuration. The sending-end converter station consists of cascaded LCC converters and VSC converters. The low-voltage DC output of the LCC converter is connected to the high-voltage DC output of the VSC converter, and each converter has a bypass switch (BPS) connected in parallel on its DC side. The LCC converter is also equipped with a small-capacity STATCOM (Static Synchronous Compensator). The STATCOM and the VSC converter jointly handle the reactive power compensation and characteristic harmonic processing required by the LCC converter. The capacity and inter-terminal DC voltage of the VSC converter can be smaller than those of the LCC converter, by reducing the voltage level of the VSC converter to reduce its capacity requirements.

[0078] The receiving-end converter station is composed of cascaded dual MMC converters, each MMC converter being composed of a full-bridge submodule or a full-half hybrid module; a grounding point is configured at the neutral bus of the converter station, and each converter is equipped with a BPS bypass switch connected in parallel on the DC side.

[0079] The startup sequence of the topology is as follows:

[0080] (1) The LCC converter at the sending end and the MMC converter 1 at the receiving end are in the DC side bypass state (i.e., BPS closed). The VSC converters 1 and 2 at the receiving end are charged through the AC grid at the receiving end, and the VSC converter at the sending end is charged through the DC side.

[0081] (2) Unlock the receiving end converter station 2 to establish DC voltage, and unlock the sending end converter station MMC converter to establish sending end AC bus voltage.

[0082] (3) When the power output of new energy is connected to the grid, it is sent out through the dual-end MMC converter when the power is low. After the output reaches the minimum power limit for LCC unlocking, the LCC converter can be unlocked and put into operation online.

[0083] (4) New energy sources continue to increase their output, and the system uses a dual-valve group for power transmission.

[0084] When the sending-end single LCC converter fails or is under maintenance, it can be switched to single MMC converter operation; when the sending-end single MMC converter fails or is under maintenance, AC voltage can be established by the opposite pole MMC converter, and the pole can be switched to single LCC converter operation.

[0085] Taking an ±800kV / 8000MW bipolar system as an example, a topology for transmitting power from a large-scale new energy base via a DC system is as follows: Figure 1As shown, the sending-end VSC converter and LCC converter carry the same DC current. Taking a 300kV DC voltage for the VSC and a 500kV DC voltage for the LCC as an example, at rated power, the VSC handles 1500MW of active power, and the LCC handles 2500MW of active power. The VSC is designed with a reactive power capacity of 450Mvar, and the STATCOM capacity of 300Mvar can meet the operating requirements of the LCC. The receiving-end VSC converters 1 and 2, as well as the sending-end VSC converter, are all equipped with 55% full-bridge modules and 45% half-bridge modules.

[0086] The system's single-stage boot strategy is as follows; the dual-stage boot strategy is similar and can be combined with... Figure 3 and Figure 4 :

[0087] 1) DC side bypass switches for the LCC converter at the sending end and the VSC converter 1 at the receiving end;

[0088] 2) The receiving end performs charging of VSC converter 2 via AC system and DC side bypass charging of VSC1, while the sending end VSC converter performs module charging via DC side.

[0089] 3) Unlock the receiving-end VSC converter 2 to DC voltage of 300kV, further charge the sending-end VSC converter, and then unlock the sending-end VSC converter. This converter uses a constant AC voltage amplitude and frequency control mode to establish the sending-end AC bus voltage.

[0090] 4) Gradually connect the new energy side to the grid. When the system output is small, the system sends power to the receiving end grid through the sending end VSC converter. Considering that the power of LCC and VSC is in a 5:3 ratio, and the LCC converter has a minimum power limit (0.1pu, 250MW) unlocking condition, when the system output is less than 400MW, the single VSC converter operation mode can be adopted.

[0091] 5) The output of new energy sources is further improved. After the output exceeds 400MW, the LCC converter and the receiving-end VSC converter 1 can be unlocked, and the corresponding bypass switch can be disconnected at the same time. The system can then switch from single valve group to dual valve group operation.

[0092] 6) During steady-state operation, the receiving-end VSC converter adopts constant DC voltage control and additional dual-valve group inter-voltage distribution control. The sending-end VSC converter adopts islanded VF control (islanded constant AC voltage amplitude and constant AC voltage frequency control) to establish AC voltage. The sending-end LCC converter adopts constant self-DC voltage control and additional dual-valve group inter-balance control. After the LCC converter completes the inter-terminal DC voltage control, the inter-terminal DC voltage of the VSC converter is passively stabilized.

[0093] When a single converter fails or is shut down for maintenance, the system switches to single valve group operation.

[0094] Taking the failure or maintenance of the sending-end pole 1 single LCC converter as an example, the sending-end LCC converter and the receiving-end VSC converter 1 simultaneously control the DC current to transfer to the BPS bypass switch, and after the current transfer is completed, the high-end valve groups on both sides can be locked.

[0095] Taking the failure or maintenance of the single VSC converter at the sending pole 1 as an example, the exit logic is the same as that for the LCC converter. After exiting, the AC voltage control transfer is completed by the VSC converter at the sending pole 2. At this time, pole 1 operates as a single valve group, and pole 2 operates as a dual valve group. If both pole VSC converters fail, the system needs to be shut down.

[0096] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.

[0097] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and this embodiment of the invention does not impose specific limitations.

[0098] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0099] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.

[0100] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.

[0101] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0102] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0103] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0104] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0105] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0106] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0107] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A topology for transmitting power from a large-scale new energy base via a DC system, characterized in that: A single-pole topology is adopted; include, The sending-end converter station is used to connect to the new energy base; the sending-end converter station includes a cascaded phase converter and a first voltage source converter, the DC low voltage output of the phase converter is connected to the DC high voltage output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches in parallel on the DC side; the phase converter is also equipped with a static synchronous compensator; The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second and third voltage source converters are equipped with bypass switches connected in parallel on their DC sides. The low-voltage end of the receiving-end converter station is also equipped with a grounding point. The first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station. as well as, The second cable is used to connect the low-voltage end of the sending-end converter station and the low-voltage end of the receiving-end converter station.

2. The topology for large-scale new energy bases transmitting power via DC systems as described in claim 1, characterized in that: Both the second and third voltage source converters are modular multilevel converters, which are composed of full-bridge sub-modules or full-half hybrid modules.

3. The control method for the topology of a large-scale new energy base transmitting power via a DC system as described in claim 1, characterized in that: include, During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked. During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold. During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

4. The control method as described in claim 3, characterized in that: During the charging phase, the bypass commutator and the second voltage source converter are bypassed, including controlling the commutator's bypass switch to close, so that the commutator is in a DC-side bypass state. The bypass switch of the second voltage source converter is closed to put the second voltage source converter into DC side bypass state.

5. The control method as described in claim 3, characterized in that: During the charging phase, the first voltage source converter and the third voltage source converter are unlocked, including, The first voltage source converter is charged through the DC side, while the second and third voltage source converters are charged through the receiving-end power grid. Unlock the third voltage source converter to establish DC voltage, and unlock the first voltage source converter to establish AC bus voltage at the sending end.

6. The control method as described in claim 3, characterized in that: During the grid-connected power output phase, when the grid-connected power output is higher than the power threshold, the first voltage source converter and the commutator are put into operation for power transmission, including unlocking the commutator, unlocking the second voltage source converter, and controlling the bypass switch of the commutator and the bypass switch of the second voltage source converter to be opened.

7. The control method as described in claim 3, characterized in that: It also includes, When the commutator fails or is under maintenance, the first voltage source converter is put into operation and switched to single valve group operation.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the control method for the topology of a large-scale new energy base transmitted via a DC system as described in any one of claims 3 to 7.

9. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the control method for the topology of the large-scale new energy base transmitted via DC system as described in any one of claims 3 to 7.

10. A topology for transmitting power from a large-scale new energy base via a DC system, characterized in that: A bipolar topology is adopted; Including the first and second poles, the first and second poles have the same structure, including, The sending-end converter station is used to connect to the new energy base; the sending-end converter station includes a cascaded phase converter and a first voltage source converter, the DC low voltage output of the phase converter is connected to the DC high voltage output of the first voltage source converter, and both the phase converter and the first voltage source converter are equipped with bypass switches in parallel on the DC side; the phase converter is also equipped with a static synchronous compensator; as well as, The receiving-end converter station is used to connect to the receiving-end power grid. The receiving-end converter station includes a second voltage source converter and a third voltage source converter connected in cascade. The DC low-voltage output of the second voltage source converter is connected to the DC high-voltage output of the third voltage source converter, and both the second voltage source converter and the third voltage source converter are equipped with bypass switches in parallel on their DC sides. It also includes, The first cable is used to connect the high-voltage end of the sending-end converter station and the high-voltage end of the receiving-end converter station in the first pole. The second cable has a first end connected to the low-voltage end of the first pole mid-sending converter station and the high-voltage end of the second pole mid-sending converter station, and a second end connected to the low-voltage end of the first pole mid-receiving converter station and the high-voltage end of the second pole mid-receiving converter station. The second end is also equipped with a grounding point. as well as The third cable is used to connect the low-voltage end of the second pole's transmitting-end converter station and the low-voltage end of the second pole's receiving-end converter station.

11. The topology for large-scale new energy bases transmitting power via DC systems as described in claim 10, characterized in that: Both the second and third voltage source converters are modular multilevel converters, which are composed of full-bridge sub-modules or full-half hybrid modules.

12. The control method for the topology of a large-scale new energy base transmitting power via a DC system as described in claim 10, characterized in that: The control methods for the first and second poles are the same, including: During the charging phase, the bypass commutation converter and the second voltage source converter are used, while the first voltage source converter and the third voltage source converter are unlocked. During the grid-connected power output phase, the first voltage source converter is put into operation for power transmission when the grid-connected power output is lower than the power threshold, and the first voltage source converter and the commutator are put into operation for power transmission when the grid-connected power output is higher than the power threshold. During steady-state operation, the second and third voltage source converters adopt constant DC voltage control with additional voltage distribution control between the two valve groups, the first voltage source converter adopts islanded VF control to establish AC voltage, and the commutated converter adopts constant DC voltage control with additional balance control between the two valve groups.

13. The control method as described in claim 12, characterized in that: During the charging phase, the bypass commutator and the second voltage source converter are bypassed, including controlling the commutator's bypass switch to close, so that the commutator is in a DC-side bypass state. The bypass switch of the second voltage source converter is closed to put the second voltage source converter into DC side bypass state.

14. The control method as described in claim 12, characterized in that: During the charging phase, the first voltage source converter and the third voltage source converter are unlocked, including, The first voltage source converter is charged through the DC side, while the second and third voltage source converters are charged through the receiving-end power grid. Unlock the third voltage source converter to establish DC voltage, and unlock the first voltage source converter to establish AC bus voltage at the sending end.

15. The control method as described in claim 12, characterized in that: During the grid-connected power output phase, when the grid-connected power output is higher than the power threshold, the first voltage source converter and the commutator are put into operation for power transmission, including unlocking the commutator, unlocking the second voltage source converter, and controlling the bypass switch of the commutator and the bypass switch of the second voltage source converter to be opened.

16. The control method as described in claim 12, characterized in that: It also includes, When the commutation converter fails or is under maintenance, the first voltage source converter is put into operation and switched to single valve group operation. When the first voltage source converter of a certain pole fails or is under maintenance, the first voltage source converter of the opposite pole is responsible for establishing the AC voltage, and the commutation converters of the first and second poles are used to transmit active power.

17. The control method as described in claim 12, characterized in that: It also includes, When the reactive power capacity of the sending-end voltage source converter is insufficient to meet the reactive power required for the operation of the sending-end commutator converter, a static synchronous compensator of a certain capacity is installed for reactive power compensation. The sending-end voltage source converter and the static synchronous compensator are responsible for filtering out the characteristic harmonics generated by the sending-end commutated converter.

18. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the control method for the topology of a large-scale new energy base transmitted via a DC system as described in any one of claims 12 to 17.

19. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the control method for the topology of the large-scale new energy base transmitted via DC system as described in any one of claims 12 to 17.

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