Multi-station and direct-current power transmission system combined voltage control method and related device

Abstract

The invention discloses a multi-station and direct-current power transmission system combined voltage control method and a related device, voltage control is performed based on whether the alternating-current voltage of each station exceeds a transient voltage regulation range, and when the alternating-current voltage exceeds the transient voltage regulation range, according to the magnitude of the alternating-current voltage of each station, the voltage of each station is controlled. The new energy stations, the direct-current unit and the variable-speed pumped storage unit emit reactive current based on a high alternating-current voltage ride-through curve or emit reactive current based on a low alternating-current voltage ride-through curve, and when the transient voltage regulation range is not exceeded, voltage control is carried out based on whether communication between the direct-current and alternating-current voltage control system and the stations is normal or not. The problems that in an existing power generation control system integrating wind power, photovoltaic, energy storage and pumped storage power stations, joint coordination voltage control between each station and a direct-current power transmission system is not considered, and great inconvenience is brought to operation and maintenance of a wind and light storage flexible direct-current looped network joint power generation system; and the system operation is difficult to meet the ever-increasing refinement requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular, to a method and related device for jointly controlling the voltage of multiple power stations and a DC transmission system. Background Art

[0002] The variable speed technology implementation methods of variable speed pumped storage units are divided into two types: stepped speed regulation and continuous speed regulation. Stepped speed regulation includes pole-changing speed regulation and double-rotor double-stator speed regulation. Continuous speed regulation includes stator-side variable frequency speed regulation and variable frequency AC excitation speed regulation. The motor part of the variable frequency AC excitation speed regulation adopts a doubly-fed motor, and the AC excitation frequency conversion is realized through a back-to-back power electronic converter.

[0003] The overall structure of a doubly-fed variable speed pumped storage unit is as Figure 1 shown. The pump-turbine serves as a prime mover or load to provide or consume power. The stator of the doubly-fed motor is the same as that of a traditional salient-pole synchronous motor, and the rotor has a symmetrically distributed three-phase winding, which is connected to the power grid through a converter and a transformer to exchange power with the power grid. The amplitude, frequency, and phase of the voltage or current output by the converter are controlled by an AC excitation regulator.

[0004] New energy represented by photovoltaic and wind power has become an important direction for energy development due to its pollution-free and renewable characteristics and no greenhouse gas emissions. With the emergence of large-scale wind power and photovoltaic power generation bases, the proportion of new energy at the DC sending end is continuously expanding and will become the main power source. In the power generation control systems integrating wind power, photovoltaic power, energy storage, and pumped storage power stations, the joint coordinated voltage control between each power station and the DC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC loop network joint power generation system, and it is also difficult for the system operation to meet the increasing refined requirements. Summary of the Invention

[0005] The present invention provides a method and related device for jointly controlling the voltage of multiple power stations and a DC transmission system, which are used to solve the technical problem that in the existing power generation control systems integrating wind power, photovoltaic power, energy storage, and pumped storage power stations, the joint coordinated voltage control between each power station and the DC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC loop network joint power generation system, and it is also difficult for the system operation to meet the increasing refined requirements.

[0006] In view of this, the first aspect of the present invention provides a method for jointly controlling the voltage of multiple power stations and a DC transmission system, including the following steps:

[0007] S1. Real-time monitor whether the AC voltage at each measurement point exceeds the normal operation range. If so, execute step S2;

[0008] S2. Determine whether the AC voltages of all substations exceed the transient voltage regulation range. If so, execute step S3; if not, jump to step S5;

[0009] S3. Determine whether the AC voltage of each substation itself is a low voltage. If so, execute step S4; if not, jump to step S9;

[0010] S4. Based on the new energy substation, DC unit, and variable-speed pumped storage unit, send the first reactive current according to the built-in low AC voltage ride-through curve;

[0011] S5. Determine whether the communication between the DC-AC voltage control system and each substation is normal. If so, execute step S6; if not, jump to step S8;

[0012] S6. Based on each substation and the DC-AC voltage control system, collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation, or the AC voltage in the load, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute step S7;

[0013] S7. Control the reactive power and voltage of each substation according to the optimal target values of the reactive power and voltage of each substation, and determine whether the AC voltage of each measuring point exceeds the normal operation range. If so, give a system alarm; if not, the joint voltage control of multiple substations and the DC transmission system ends;

[0014] S8. Based on the new energy substation, DC unit, and variable-speed pumped storage unit, send reactive power according to the built-in AC voltage and reactive power curve. After a preset time, determine whether the AC voltage of each measuring point is adjusted to the normal operation range. If not, give a system alarm; if so, the joint voltage control of multiple substations and the DC transmission system ends;

[0015] S9. Based on the new energy substation, DC unit, and variable-speed pumped storage unit, send the second reactive current according to the built-in high AC voltage ride-through curve.

[0016] Optionally, the joint voltage control method of multiple substations and the DC transmission system is applied to the 500 kV grid, and the normal operation range is 515 kV - 540 kV.

[0017] Optionally, the transient voltage regulation range is 472 kV - 577 kV.

[0018] Optionally, the preset time is 0.1 s.

[0019] In the second aspect of the present invention, a joint voltage control device for multiple substations and a DC transmission system is provided, including the following modules:

[0020] A voltage monitoring module, which is used to monitor in real time whether the AC voltage at each measuring point exceeds the normal operation range. If so, the first judgment module is executed;

[0021] A first judgment module, which is used to judge whether the AC voltage of each substation exceeds the transient voltage regulation range. If so, the second judgment module is executed. If not, it jumps to the third judgment module;

[0022] A second judgment module, which is used to judge whether the AC voltage of each substation itself is a low voltage. If so, the first control module is executed. If not, it jumps to the fourth control module;

[0023] A first control module, which is used to generate a first reactive current based on new energy power stations, DC units, and variable-speed pumped storage units according to the built-in low AC voltage ride-through curve;

[0024] A third judgment module, which is used to judge whether the communication between the DC-AC voltage control system and each substation is normal. If so, the optimization module is executed. If not, it jumps to the third control module;

[0025] An optimization module, which is used to collect the adjustable reactive power capacity of each substation, the AC voltage in the vicinity of each substation, or the AC voltage in the load based on each substation and the DC-AC voltage control system, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute the second control module;

[0026] A second control module, which is used to control the reactive power and voltage of each substation according to the optimal target values of the reactive power and voltage of each substation, and judge whether the AC voltage at each measuring point exceeds the normal operation range. If so, system alarm is performed. If not, the joint voltage control of multiple substations and the DC transmission system ends;

[0027] A third control module, which is used to generate reactive power based on new energy power stations, DC units, and variable-speed pumped storage units according to the built-in AC voltage and reactive power curve. After a preset time, it judges whether the AC voltage at each measuring point is adjusted to the normal operation range. If not, system alarm is performed. If so, the joint voltage control of multiple substations and the DC transmission system ends;

[0028] A fourth control module, which is used to generate a second reactive current based on new energy power stations, DC units, and variable-speed pumped storage units according to the built-in high AC voltage ride-through curve.

[0029] Optionally, the joint voltage control method of multiple substations and the DC transmission system is applied to the 500 kV grid, and the normal operation range is 515 kV - 540 kV.

[0030] Optionally, the transient voltage regulation range is 472 kV - 577 kV.

[0031] Optionally, the preset time is 0.1 s.

[0032] A third aspect of the present invention provides a combined voltage control device for multiple substations and a DC power transmission system, the device comprising a processor and a memory:

[0033] The memory is used to store program codes and transmit the program codes to the processor;

[0034] The processor is used to execute any one of the combined voltage control methods for multiple substations and a DC power transmission system in the first aspect according to the instructions in the program codes.

[0035] A fourth aspect of the present invention provides a computer-readable storage medium, which is used to store program codes, and the program codes are used to execute any one of the combined voltage control methods for multiple substations and a DC power transmission system in the first aspect.

[0036] It can be seen from the above technical solutions that the combined voltage control method for multiple substations and a DC power transmission system provided by the present invention has the following advantages:

[0037] For the combined voltage control method for multiple substations and a DC power transmission system provided by the present invention, when the AC voltages at each measurement point exceed the normal operation range, voltage control is respectively performed based on whether the AC voltages of each substation exceed the transient voltage regulation range. When the transient voltage regulation range is exceeded, according to the high and low of the AC voltages of each substation itself, the new energy substation, the DC unit and the variable-speed pumped storage unit send reactive current based on the high AC voltage crossing curve or send reactive current based on the low AC voltage crossing curve. When the transient voltage regulation range is not exceeded, voltage control is respectively performed based on whether the communication between the DC-AC voltage control system and each substation is normal. When the communication is abnormal, the new energy substation, the DC unit and the variable-speed pumped storage unit send reactive power based on the AC voltage and reactive power curve for voltage control. When the communication is normal, reactive power and voltage optimization are performed on each substation based on the reactive power-voltage optimization algorithm, solving the technical problem that in the existing power generation control system integrating wind power, photovoltaic power, energy storage and pumped storage power stations, the combined and coordinated voltage control between each substation and the DC power transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC ring network combined power generation system, and it is difficult for the system operation to meet the increasing refined requirements. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is a schematic diagram of the overall structure of a variable-speed pumped-storage unit;

[0040] Figure 2 It is a schematic flowchart of a joint voltage control method for multiple substations and a DC power transmission system provided in an embodiment of the present invention;

[0041] Figure 3 It is a topological schematic diagram of multiple substations and measurement points provided in an embodiment of the present invention;

[0042] Figure 4 It is a schematic diagram of the structure of a joint voltage control device for multiple substations and a DC power transmission system provided in an embodiment of the present invention;

[0043] Figure 5 It is a schematic diagram of the structure of a joint voltage control device for multiple substations and a DC power transmission system provided in an embodiment of the present invention. Detailed implementation manners

[0044] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] For the convenience of understanding, please refer to Figure 2 , an embodiment of a joint voltage control method for multiple substations and a DC power transmission system provided by the present invention includes:

[0046] Step S1: Real-time monitor whether the AC voltage at each measurement point exceeds the normal operating range. If so, execute Step S2.

[0047] It should be noted that the DC power transmission project mainly consists of converter stations (rectifier stations and inverter stations), DC lines, power filters on the AC side and DC side, reactive power compensation devices, converter transformers, DC reactors, as well as protection and control devices, etc. The alternating current generated by the power plant is converted into direct current by the rectifier and transmitted to the receiving end, and then the direct current is converted into alternating current by the inverter and sent to the receiving-end AC power grid. The multiple substations in the embodiments of the present invention include variable-speed pumped-storage power stations and intensive new energy bases (including energy storage, wind turbines, and photovoltaics). In one embodiment, the joint voltage control method for multiple substations and a DC power transmission system is applied to a 500 kV grid, and its normal operating range is 515 kV - 540 kV.

[0048] Step S2: Determine whether the AC voltages of all substations exceed the transient voltage regulation range. If so, execute Step S3; if not, jump to Step S5.

[0049] It should be noted that if no measurement points exceeding the normal operation range are detected, continuous monitoring is carried out. When the AC voltage of a measurement point exceeds the normal operation range, determine whether the AC voltages of all substations exceed the transient voltage regulation range. Taking the 500 kV grid as an example, the transient voltage regulation range is 472 kV - 577 kV. When the AC voltages of all substations exceed the transient voltage regulation range, execute Step S3; otherwise, jump to Step S5.

[0050] Step S3: Determine whether the AC voltage of each substation itself is a low voltage. If so, execute Step S4; if not, jump to Step S9.

[0051] It should be noted that the situation where the AC voltage of each substation itself is lower than the normal operation range is regarded as a low voltage, and the situation where the AC voltage of each substation itself is higher than the normal operation range is regarded as a high voltage.

[0052] Step S4: Based on the new energy substation, DC unit, and variable-speed pumped storage unit, issue the first reactive current according to the built-in low AC voltage ride-through curve.

[0053] It should be noted that when the AC voltage of each substation itself is a low voltage, the new energy substation, DC unit, and variable-speed pumped storage unit issue the first reactive current according to the built-in low AC voltage ride-through curve (i.e., the AC voltage - reactive current reference value curve under low AC voltage).

[0054] Step S5: Determine whether the communication between the DC-AC voltage control system and each substation is normal. If so, execute Step S6; if not, jump to Step S8.

[0055] It should be noted that when the AC voltages of all substations do not all exceed the transient voltage regulation range, determine whether the communication between the DC-AC voltage control system and each substation is normal. If the communication is normal, execute Step S6; otherwise, execute Step S8.

[0056] Step S6: Based on each substation and the DC-AC voltage control system, collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation, or the AC voltage in the load, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute Step S7.

[0057] It should be noted that when the AC voltages of all substations do not all exceed the transient voltage regulation range and the communication between the DC-AC voltage control system and each substation is normal, each substation and the DC-AC voltage control system collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation, or the AC voltage in the load, such as Figure 3As shown, the normal voltage is 525 kV, the AC voltage of Substation 1 is 525 kV, the AC voltage of Measuring Point 1 is 510 kV, the AC voltage of Substation 2 is 520 kV, the AC voltage of Measuring Point 2 is 510 kV, the AC voltage of Substation 3 is 520 kV, the reactive power capacity of Substation 1 is 400 Mvar, the reactive power capacity of Substation 2 is 200 Mvar, and the reactive power capacity of Substation 3 is 100 Mvar. The optimal target values of reactive power and voltage for each substation are determined according to the remaining adjustable reactive power capacity of each substation and the AC voltage deviation of each measuring point. Using a reactive power-voltage optimization algorithm, such as the optimal power flow algorithm, the optimal target values of reactive power and voltage for each substation are calculated.

[0058] Step S7: Control the reactive power and voltage of each substation according to the optimal target values of reactive power and voltage of each substation, and determine whether the AC voltage of each measuring point exceeds the normal operating range. If so, a system alarm is issued. If not, the joint voltage control of multiple substations and the DC transmission system ends.

[0059] It should be noted that after calculating the optimal target values of reactive power and voltage of each substation in Step S6, the reactive power and voltage of each substation are controlled according to the optimal target values of reactive power and voltage of each substation, and then it is determined whether the AC voltage of each measuring point exceeds the normal operating range. If there are still measuring points with AC voltage exceeding the normal operating range, a system alarm is issued. If there are no measuring points with AC voltage exceeding the normal operating range, the joint voltage control of multiple substations and the DC transmission system ends.

[0060] Step S8: Based on the new energy substation, DC unit, and variable-speed pumped-storage unit, reactive power is generated according to the built-in AC voltage and reactive power curve. After a preset time, it is determined whether the AC voltage of each measuring point is adjusted to the normal operating range. If not, a system alarm is issued. If so, the joint voltage control of multiple substations and the DC transmission system ends.

[0061] It should be noted that when the AC voltages of each substation do not all exceed the transient voltage regulation range and the communication between the DC-AC voltage control system and each substation is abnormal, the new energy substation, DC unit, and variable-speed pumped-storage unit generate reactive power according to the built-in AC voltage and reactive power curve to maintain the steady-state AC voltage. Then, after a preset time, it is determined whether the AC voltage of each measuring point is adjusted to the normal operating range. If not, a system alarm is issued. If so, the joint voltage control of multiple substations and the DC transmission system ends. In the embodiment of the present invention, the preset time is 0.1 s.

[0062] Step S9: Based on the new energy substation, DC unit, and variable-speed pumped-storage unit, a second reactive current is generated according to the built-in high AC voltage crossing curve.

[0063] It should be noted that when the AC voltage of each station is high voltage, the new energy station, DC unit, and variable-speed pumped storage unit generate the second reactive current according to the built-in high AC voltage crossing curve (i.e., the AC voltage-reactive current reference value curve under high AC voltage).

[0064] The joint voltage control method for multiple stations and DC transmission system provided by the present invention performs voltage control respectively based on whether the AC voltage at each measurement point exceeds the normal operation range. When it exceeds the transient voltage regulation range, according to the level of the AC voltage of each station itself, the new energy station, DC unit, and variable-speed pumped storage unit generate reactive current based on the high AC voltage crossing curve or generate reactive current based on the low AC voltage crossing curve. When it does not exceed the transient voltage regulation range, voltage control is performed respectively based on whether the communication between the DC-AC voltage control system and each station is normal. When the communication is abnormal, the new energy station, DC unit, and variable-speed pumped storage unit generate reactive power based on the AC voltage and reactive power curve for voltage control. When the communication is normal, reactive power and voltage optimization are performed on each station based on the reactive power-voltage optimization algorithm, solving the technical problem that in the existing power generation control systems integrating wind power, photovoltaic power, energy storage, and pumped storage power stations, the joint coordinated voltage control between each station and the DC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC loop network joint power generation system, and it is difficult for the system operation to meet the increasing refined requirements.

[0065] For easy understanding, please refer to Figure 4 , an embodiment of a joint voltage control device for multiple stations and DC transmission system provided in the present invention includes the following modules:

[0066] The voltage monitoring module is used to monitor in real time whether the AC voltage at each measurement point exceeds the normal operation range. If so, the first judgment module is executed;

[0067] The first judgment module is used to judge whether the AC voltage of each station exceeds the transient voltage regulation range. If so, the second judgment module is executed. If not, it jumps to the third judgment module;

[0068] The second judgment module is used to judge whether the AC voltage of each station itself is low voltage. If so, the first control module is executed. If not, it jumps to the fourth control module;

[0069] The first control module is used to generate the first reactive current based on the new energy station, DC unit, and variable-speed pumped storage unit according to the built-in low AC voltage crossing curve;

[0070] The third judgment module is used to judge whether the communication between the DC-AC voltage control system and each station is normal. If so, the optimization module is executed. If not, it jumps to the third control module;

[0071] An optimization module, which is configured to collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation, or the AC voltage of the load based on each substation and the DC-AC voltage control system, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute the second control module;

[0072] A second control module, which is configured to control the reactive power and voltage of each substation according to the optimal target values of the reactive power and voltage of each substation, determine whether the AC voltage of each measurement point exceeds the normal operation range. If so, a system alarm is issued. If not, the joint voltage control of multiple substations and the DC transmission system ends;

[0073] A third control module, which is configured to generate reactive power based on new energy substations, DC units, and variable-speed pumped storage units according to the built-in AC voltage and reactive power curve. After a preset time, it determines whether the AC voltage of each measurement point is adjusted to the normal operation range. If not, a system alarm is issued. If so, the joint voltage control of multiple substations and the DC transmission system ends;

[0074] A fourth control module, which is configured to generate a second reactive current based on new energy substations, DC units, and variable-speed pumped storage units according to the built-in high AC voltage crossing curve.

[0075] In one embodiment, the joint voltage control method of multiple substations and the DC transmission system is applied to a 500 kV grid, and the normal operation range is 515 kV - 540 kV.

[0076] In one embodiment, the transient voltage regulation range is 472 kV - 577 kV.

[0077] In one embodiment, the preset time is 0.1 s.

[0078] For ease of understanding, please refer to Figure 5 , and an embodiment of a joint voltage control device for multiple substations and the DC transmission system is also provided in the present invention. The device includes a processor and a memory:

[0079] The memory is used to store program codes and transmit the program codes to the processor;

[0080] The processor is configured to execute any one of the implementation manners in the foregoing embodiments of the joint voltage control method for multiple substations and the DC transmission system according to the instructions in the program codes.

[0081] An embodiment of a computer-readable storage medium is also provided in the present invention. The computer-readable storage medium is used to store program codes, and the program codes are used to execute any one of the implementation manners in the foregoing embodiments of the joint voltage control method for multiple substations and the DC transmission system.

[0082] An embodiment of a computer program product including instructions is also provided in the present invention. When it runs on a computer, it causes the computer to execute any one of the implementation manners in the foregoing embodiments of the combined voltage control method for multiple substations and HVDC transmission systems.

[0083] The combined voltage control device, equipment, computer-readable storage medium and computer program product including instructions provided in the present invention are all used to execute the combined voltage control method for multiple substations and HVDC transmission systems provided in the present invention. The principle and the achieved technical effects are the same as those of the combined voltage control method for multiple substations and HVDC transmission systems provided in the present invention, and will not be elaborated herein.

[0084] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described systems, devices and units can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0085] The terms "first", "second", "third", "fourth", etc. in the specification of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0086] It should be understood that in the present invention, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B may be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one (piece)" or similar expressions thereof refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, at least one (piece) of a, b or c may mean: a, b, c, "a and b", "a and c", "b and c", or "a, b and c", where a, b, c may be single or multiple.

[0087] In several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections between each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0088] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0089] In addition, each functional unit in various embodiments of the present invention can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0090] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. And the aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks, or optical discs, etc., which can store program codes.

[0091] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A combined voltage control method for multiple substations and a DC power transmission system, characterized in that It includes the following steps: S1. Real-time monitor whether the AC voltage at each measuring point exceeds the normal operation range. If so, execute step S2; S2. Judge whether the AC voltage of each substation exceeds the transient voltage regulation range. If so, execute step S3; if not, jump to step S5; S3. Judge whether the AC voltage of each substation itself is a low voltage. If so, execute step S4; if not, jump to step S9; S4. Based on the new energy substation, DC unit and variable-speed pumped storage unit, send the first reactive current according to the built-in low AC voltage ride-through curve; S5. Judge whether the communication between the DC-AC voltage control system and each substation is normal. If so, execute step S6; if not, jump to step S8; S6. Based on each substation and the DC-AC voltage control system, collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation or the AC voltage in the load, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute step S7; S7. Control the reactive power and voltage of each substation according to the optimal target values of the reactive power and voltage of each substation. Judge whether the AC voltage at each measuring point exceeds the normal operation range. If so, give a system alarm; if not, the joint voltage control of multiple substations and the DC transmission system ends; S8. Based on the new energy substation, DC unit and variable-speed pumped storage unit, send reactive power according to the built-in AC voltage and reactive power curve. After a preset time, judge whether the AC voltage at each measuring point is adjusted to the normal operation range. If not, give a system alarm; if so, the joint voltage control of multiple substations and the DC transmission system ends; S9. Based on the new energy substation, DC unit and variable-speed pumped storage unit, send the second reactive current according to the built-in high AC voltage ride-through curve.

2. The combined voltage control method for multiple substations and HVDC transmission system according to claim 1, characterized in that, The joint voltage control method of multiple substations and the DC transmission system is applied to the 500 kV grid, and the normal operation range is 515 kV - 540 kV.

3. The multi-station and HVDC system combined voltage control method according to claim 2, characterized in that The transient voltage regulation range is 472 kV - 577 kV.

4. The combined voltage control method for multi-station and HVDC transmission system according to claim 1, characterized in that The preset time is 0.1 s.

5. A combined voltage control device for multiple substations and a DC power transmission system, characterized in that, It includes the following modules: Voltage monitoring module, which is used to real-time monitor whether the AC voltage at each measuring point exceeds the normal operation range. If so, execute the first judgment module; First judgment module, which is used to judge whether the AC voltage of each substation exceeds the transient voltage regulation range. If so, execute the second judgment module; if not, jump to the third judgment module; Second judgment module, which is used to judge whether the AC voltage of each substation itself is a low voltage. If so, execute the first control module; if not, jump to the fourth control module; First control module, which is used to based on the new energy substation, DC unit and variable-speed pumped storage unit, send the first reactive current according to the built-in low AC voltage ride-through curve; Third judgment module, which is used to judge whether the communication between the DC-AC voltage control system and each substation is normal. If so, execute the optimization module; if not, jump to the third control module; Optimization module, which is used to collect the adjustable reactive power capacity of each substation, the AC voltage in the near area of each substation or the AC voltage of the load based on each substation and the DC-AC voltage control system, calculate the optimal target values of the reactive power and voltage of each substation based on the reactive power-voltage optimization algorithm, and execute the second control module; Second control module, which is used to control the reactive power and voltage of each substation according to the optimal target values of the reactive power and voltage of each substation, judge whether the AC voltage of each measuring point exceeds the normal operation range. If so, a system alarm is issued. If not, the joint voltage control of multiple substations and the DC transmission system ends; Third control module, which is used to generate reactive power based on new energy substations, DC units and variable-speed pumped storage units according to the built-in AC voltage and reactive power curve. After a preset time, judge whether the AC voltage of each measuring point is adjusted to the normal operation range. If not, a system alarm is issued. If so, the joint voltage control of multiple substations and the DC transmission system ends; Fourth control module, which is used to generate a second reactive current based on new energy substations, DC units and variable-speed pumped storage units according to the built-in high AC voltage crossing curve.

6. The combined voltage control device for multiple substations and HVDC transmission system according to claim 5, characterized in that, The joint voltage control method of multiple substations and the DC transmission system is applied to the 500 kV grid, and the normal operation range is 515 kV - 540 kV.

7. The combined voltage control device for multiple substations and HVDC system according to claim 6, characterized in that The transient voltage regulation range is 472 kV - 577 kV.

8. The combined voltage control device for multiple substations and HVDC transmission system according to claim 5, wherein The preset time is 0.1 s.

9. A combined voltage control device for multiple substations and a DC power transmission system, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the joint voltage control method of multiple substations and the DC transmission system according to the instructions in the program code as described in any one of claims 1-4.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code, and the program code is used to execute the joint voltage control method of multiple substations and the DC transmission system according to any one of claims 1-4.

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