Offshore platform design method and system for flexible DC transmission

Abstract

The present invention discloses a method and system for designing an offshore platform for flexible direct current transmission. The method first calculates the PQ operation range of the offshore and onshore converter stations respectively based on the designed initial value of the valve side voltage of the connecting transformer of the offshore and onshore converter stations, and continuously adjusts the valve side voltage value of the offshore and onshore converter stations until the PQ operation range of the offshore and onshore converter stations meets the preset requirements, and then designs the insulation matching parameters based on the connecting transformer valve side voltage and PQ operation range that meet the requirements, and finally calculates the volume and weight of the offshore platform according to the insulation parameters. The present invention can ensure that the offshore platform can maintain sufficient stability and anti-interference ability under various operating conditions of offshore wind power flexible direct current transmission, and can reasonably design the volume and weight of the offshore platform, thereby reducing the construction and maintenance costs of the offshore platform.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current power transmission, and in particular to a method and system for designing an offshore platform for flexible direct current power transmission. Background Art

[0002] As a clean and renewable energy source, offshore wind power has developed rapidly in recent years. Since offshore wind farms are usually far away from land, flexible DC transmission has become the mainstream solution for offshore wind power DC transmission. As an important part of offshore wind farms, offshore platforms (a truss structure with a horizontal surface above the sea) provide important infrastructure for flexible DC transmission systems.

[0003] There are many power devices on offshore platforms, and the devices are heavy and expensive. Therefore, the volume and weight of offshore platforms are the decisive factors for the economic efficiency of offshore wind power transmission projects. The volume and weight of offshore platforms are closely related to the design of flexible DC transmission systems, power equipment parameters, and insulation matching parameters, and the various factors are closely coupled with each other. However, the design process of flexible DC transmission systems requires a comprehensive iteration of factors such as primary equipment parameters, system parameters, transient response characteristics, and secondary system solutions. The factors involved are wide, and the iterative process requires a large amount of calculation. Moreover, for offshore wind power flexible DC transmission systems, on the basis of the above factors, it is also necessary to consider the lightweight of offshore platforms and the economic efficiency of the project, which further increases the difficulty of system design optimization. Therefore, it is particularly important to clarify the interactive effects between various parameters or design schemes, sort out the design process, and minimize the repeated iterations between various parameters while ensuring the reliability of offshore wind power transmission projects. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an offshore platform design method and system for flexible direct current transmission, which can effectively improve the safety and economy of the offshore platform through reasonable insulation matching parameter design, and is more conducive to the development of offshore wind power flexible direct current transmission projects.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides an offshore platform design method for flexible direct current power transmission, comprising:

[0006] Design the initial value of the valve-side voltage of the connecting transformer at the offshore converter station and the initial value of the valve-side voltage of the connecting transformer at the onshore converter station;

[0007] Based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station, the PQ operation range of the offshore converter station is calculated;

[0008] Based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station, the PQ operation range of the onshore converter station under different tap positions is calculated;

[0009] Adjusting the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement;

[0010] Design insulation coordination parameters based on the valve-side voltage value of the connecting transformer of the offshore converter station that meets the first preset requirement and the PQ operation range of the offshore converter station, and the valve-side voltage value of the connecting transformer of the onshore converter station that meets the second preset requirement and the PQ operation range of the onshore converter station;

[0011] The volume and weight of the offshore platform are calculated according to the insulation coordination parameters.

[0012] As an improvement of the above solution, the design of the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station includes:

[0013] Design the initial value of the valve-side voltage of the connecting transformers of the offshore converter station and the onshore converter station based on the DC voltage and modulation ratio range;

[0014] The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

[0015] As an improvement of the above solution, the calculation of the PQ operation range of the offshore converter station based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station includes:

[0016] Based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the first initial condition, the PQ operation range of the offshore converter station is calculated;

[0017] The PQ operation range of the offshore converter station includes the reactive power demand range of the offshore converter station system.

[0018] Optionally, the first initial condition includes a modulation ratio variation range, an active power transmission capacity of the offshore flexible direct current transmission system, and a capacity of a connecting transformer.

[0019] Optionally, when the PQ operation range of the offshore converter station cannot meet the first preset requirement, a tap is set for the connecting transformer of the offshore converter station.

[0020] Optionally, when the volume and weight of the offshore platform cannot meet the third preset requirement, the modulation ratio transformation range is adjusted and the insulation matching parameters are redesigned until the volume and weight of the offshore platform meet the third preset requirement.

[0021] Optionally, an initial value of the valve-side voltage of the connection transformer of the offshore converter station is the same as an initial value of the valve-side voltage of the connection transformer of the onshore converter station.

[0022] Optionally, the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station are both:

[0023] ;

[0024] Among them, the is the rated modulation ratio, is a DC voltage.

[0025] In order to solve the above technical problems, an embodiment of the present invention further provides an offshore platform design system for flexible direct current transmission, comprising:

[0026] The voltage initial value design module is used to design the initial value of the valve side voltage of the connecting transformer of the offshore converter station and the initial value of the valve side voltage of the connecting transformer of the onshore converter station;

[0027] A first operation interval calculation module, used to calculate the PQ operation interval of the offshore converter station based on the initial value of the valve side voltage of the connecting transformer of the offshore converter station;

[0028] The second operation interval calculation module is used to calculate the PQ operation interval of the onshore converter station under different tap positions based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station;

[0029] An operation range adjustment module, used to adjust the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively, until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement;

[0030] An insulation coordination parameter design module, used to design insulation coordination parameters based on a connection transformer valve side voltage value of an offshore converter station that meets a first preset requirement and a PQ operation range of the offshore converter station, and a connection transformer valve side voltage value of an onshore converter station that meets a second preset requirement and a PQ operation range of the onshore converter station;

[0031] The offshore platform design module is used to calculate the volume and weight of the offshore platform according to the insulation coordination parameters.

[0032] As an improvement of the above solution, the voltage initial value design module is specifically used for:

[0033] Based on the DC voltage and modulation ratio range, design the initial value of the valve-side voltage of the connecting transformer at the offshore converter station and the initial value of the valve-side voltage of the connecting transformer at the onshore converter station;

[0034] The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

[0035] Compared with the prior art, the embodiment of the present invention provides a method and system for designing an offshore platform for flexible direct current transmission. The method first calculates the PQ operating range of the offshore and onshore converter stations respectively based on the designed initial value of the valve-side voltage of the connecting transformer of the offshore and onshore converter stations, and continuously adjusts the valve-side voltage value of the offshore and onshore converter stations until the PQ operating range of the offshore and onshore converter stations meets the preset requirements, and then designs the insulation matching parameters based on the connecting transformer valve-side voltage and PQ operating range that meet the requirements, and finally calculates the volume and weight of the offshore platform according to the insulation parameters. The embodiment of the present invention optimizes the connecting transformer valve-side voltage and PQ operating range, and finally determines the insulation parameters and calculates the volume and weight of the platform, thereby realizing the design of a flexible direct current transmission offshore platform. By optimizing the valve-side voltage and PQ operating range of the connecting transformers between offshore and onshore converter stations, it is possible to ensure that the offshore platform can maintain sufficient stability and anti-interference capability under various operating conditions of offshore wind power flexible DC transmission. By reasonably designing insulation parameters, the volume and weight of the offshore platform can be reasonably designed, thereby reducing construction and maintenance costs and improving economic benefits, which is of great significance for promoting offshore wind power flexible DC transmission projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution of the present invention, the drawings used in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a flow chart of a method for designing an offshore platform for flexible direct current power transmission provided by an embodiment of the present invention;

[0038] Figure 2 is another flow chart of a method for designing an offshore platform for flexible direct current power transmission provided by an embodiment of the present invention;

[0039] Figure 3 It is a structural block diagram of an offshore platform design system for flexible direct current transmission provided by an embodiment of the present invention. DETAILED DESCRIPTION

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

[0041] It should be noted that a typical offshore wind power flexible DC system includes two converter stations, namely the offshore converter station and the onshore converter station. Generally speaking, the offshore station adopts voltage / frequency control, and the onshore station adopts constant DC voltage / reactive power-AC voltage control.

[0042] It should be noted that the PQ operating range, usually referred to as the "active-reactive operating range" or "power-reactive operating range", characterizes the output capacity of the converter in terms of active power (P) and reactive power (Q), and is one of the key contents of the design of the flexible DC system for offshore wind power. The calculation of the PQ operating range usually needs to consider the constraints of the converter transformer capacity, the steady-state range constraints of the modulation ratio, the current limit of the DC cable, the thermal stability current constraints of the bridge arm, the steady-state operating range of the AC bus voltage, and the steady-state operating range of the DC port voltage.

[0043] See also Figure 1 , Figure 1 1 is a flow chart of a method for designing an offshore platform for flexible direct current power transmission provided by an embodiment of the present invention. The method for designing an offshore platform for flexible direct current power transmission comprises steps S1 to S6:

[0044] S1. Design the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station;

[0045] Specifically, the design of the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station includes:

[0046] Design the initial value of the valve-side voltage of the connecting transformers of the offshore converter station and the onshore converter station based on the DC voltage and modulation ratio range;

[0047] The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

[0048] It should be noted that in the DC transmission system, the initial value of the valve-side voltage of the transformer connected to the converter station is an important parameter that affects the operation of the system. Generally speaking, the DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system. The modulation ratio in engineering usually ranges from 0.75 to 0.95, and the rated modulation ratio M is usually 0.85; when the converter adopts third harmonic injection, the modulation ratio usually ranges from 0.85 to 1.05, and the rated modulation ratio M is usually 0.95.

[0049] In an optional embodiment, the initial value of the valve-side voltage of the connection transformer of the offshore converter station is the same as the initial value of the valve-side voltage of the connection transformer of the onshore converter station.

[0050] Furthermore, the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station are both:

[0051] ;

[0052] Among them, the is the rated modulation ratio, is a DC voltage.

[0053] It should be noted that, although the valve-side voltages of the connecting transformers of the offshore and onshore converter stations are decoupled from each other, in order to maintain the consistency of the two converter stations in actual projects, the valve-side voltages of the connecting transformers of the two converter stations are usually the same.

[0054] S2. Calculate the PQ operation range of the offshore converter station based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station;

[0055] Specifically, the calculating of the PQ operation range of the offshore converter station based on the initial value of the valve-side voltage of the connection transformer of the offshore converter station includes:

[0056] Based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the first initial condition, the PQ operation range of the offshore converter station is calculated;

[0057] The PQ operation range of the offshore converter station includes the reactive power demand range of the offshore converter station system.

[0058] Preferably, the first initial condition includes the modulation ratio variation range, the active power transmission capacity of the offshore flexible direct current transmission system and the capacity of the connecting transformer.

[0059] It should be noted that the connecting transformer of the offshore converter station is usually not equipped with taps. Therefore, based on the initial value of the connecting transformer valve-side voltage and other initial conditions, the PQ operating range of the offshore converter station can be calculated. The PQ operating range must include the reactive power demand range of the offshore system. For offshore wind farms, the reactive power demand should be considered on the basis of satisfying reactive power zeroing. Other initial conditions include the modulation ratio variation range, the active power transmission capacity of the DC system, the connecting transformer capacity, etc.

[0060] S3. Based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station, calculate the PQ operation range of the onshore converter station under different tap positions;

[0061] Exemplarily, based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station and the reactive power demand of the onshore converter station system, the tap position of the onshore converter station is designed, and then based on the initial value of the valve-side voltage of the connecting transformer and other initial conditions, the PQ operating range under different tap positions is calculated in turn.

[0062] S4. Adjust the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement;

[0063] In an optional implementation, when the PQ operation range of the offshore converter station cannot meet the first preset requirement, a tap is set for the connection transformer of the offshore converter station.

[0064] It should be noted that the PQ operating range of the offshore converter station may not be able to meet the first preset requirement. For example, due to the large voltage fluctuation of the offshore power grid, the output power and reactive power of the offshore converter station cannot meet the preset requirements. The tap position can be adjusted to change the transformation ratio of the connecting transformer and adjust the valve side voltage of the offshore converter station so that the PQ operating range meets the requirements.

[0065] Exemplarily, if the PQ operation ranges of the offshore converter station system and the onshore converter station system cannot meet the requirements at the same time, the valve-side voltages of the respective connecting transformers are adjusted respectively, and steps S2 to S3 are repeated until the reactive power of the offshore and onshore converter station systems meets the requirements. If the PQ operation range obtained based on the above steps cannot always meet the reactive power requirements of the offshore and onshore AC systems, when the PQ operation range cannot meet the reactive power requirements of the corresponding systems, the rated modulation ratio and the valve-side voltage of the connecting transformer need to be adjusted, and the above steps are repeated again until the reactive power requirements of the offshore and onshore AC systems can be met at the same time.

[0066] S5. Design insulation coordination parameters based on the valve-side voltage value of the connecting transformer of the offshore converter station that meets the first preset requirement and the PQ operation range of the offshore converter station, and the valve-side voltage value of the connecting transformer of the onshore converter station that meets the second preset requirement and the PQ operation range of the onshore converter station;

[0067] Exemplarily, the insulation coordination parameter design of equipment and systems is carried out based on the valve-side voltage value of the connecting transformer of the offshore converter station and the onshore converter station that meets preset requirements, the PQ operating range of the offshore converter station, the PQ operating range of the onshore converter station and other system parameters.

[0068] It should be noted that insulation coordination refers to the principles, methods and regulations used to determine the insulation level of transmission lines and electrical equipment in power systems. The purpose of studying insulation coordination is to comprehensively consider the possible applied voltages that electrical facilities may be subjected to, the effectiveness of overvoltage protection devices, and the tolerance characteristics of the insulation materials and insulation structures of the equipment to various applied voltages, and to determine the insulation level of transmission lines and electrical equipment considering economic rationality.

[0069] Therefore, the insulation coordination parameter design also needs to analyze the system and equipment overvoltage conditions under fault conditions, and design the lightning arrester configuration plan and equipment insulation parameters based on the analysis results.

[0070] S6. Calculate the volume and weight of the offshore platform according to the insulation matching parameters.

[0071] Optionally, when the volume and weight of the offshore platform cannot meet the third preset requirement, the modulation ratio transformation range is adjusted and the insulation matching parameters are redesigned until the volume and weight of the offshore platform meet the third preset requirement.

[0072] Exemplarily, the weight, volume and cost of the offshore platform are calculated according to the design scheme of the insulation coordination parameters, and the engineering design and construction requirements are verified. Generally, the higher the system insulation level, the larger the volume and weight of the offshore platform. When the volume and weight of the offshore platform do not meet the requirements, adjust the modulation ratio variation range, and repeat the above steps S1 to S6 until the requirements are met. If the volume and weight of the offshore platform still cannot meet the engineering design and construction requirements, lower the upper limit of the modulation ratio, and repeat the above steps S1 to S6 to carry out the design of the insulation coordination parameters of the system.

[0073] In summary, the embodiment of the present invention first calculates the PQ operating range of the offshore and onshore converter stations based on the designed initial value of the valve side voltage of the connecting transformer of the offshore and onshore converter stations, and continuously adjusts the valve side voltage value of the offshore and onshore converter stations until the PQ operating range of the offshore and onshore converter stations meets the preset requirements, and then designs the insulation matching parameters based on the connecting transformer valve side voltage and PQ operating range that meet the requirements, and finally calculates the volume and weight of the offshore platform according to the insulation parameters. The embodiment of the present invention optimizes the valve side voltage of the connecting transformer and the PQ operating range, and finally determines the insulation parameters and calculates the volume and weight of the platform, thereby realizing the design of the flexible direct current transmission offshore platform. By optimizing the valve side voltage and PQ operating range of the connecting transformer of the offshore and onshore converter stations, it can ensure that the offshore platform can maintain sufficient stability and anti-interference ability under various operating conditions of the flexible direct current transmission of offshore wind power; by reasonably designing the insulation parameters, the volume and weight of the offshore platform can be reasonably designed, thereby reducing the construction and maintenance costs and improving the economic benefits, which is of great significance for promoting the flexible direct current transmission project of offshore wind power.

[0074] In order to enable those skilled in the art to more clearly understand an offshore platform design method for flexible direct current transmission provided in an embodiment of the present invention, an offshore wind power flexible direct current transmission project with a voltage level of ±320kV and a transmission power of 940MW is used as an example for explanation below.

[0075] See also Figure 2 , Figure 2FIG. 1 is another flow chart of a method for designing an offshore platform for flexible direct current transmission provided by an embodiment of the present invention. Figure 2 As shown, firstly, based on the DC voltage, modulation ratio variation range, and reactive power requirements of the offshore and onshore converter station systems, the initial values ​​of the valve-side voltages of the connecting transformers of the offshore converter station and the onshore converter station are calculated respectively, and finally the initial value of the valve-side voltages of the connecting transformers of the offshore converter station and the onshore converter station is obtained as 333.13 kV.

[0076] Secondly, based on the initial value of the valve-side voltage of the offshore converter station connection transformer, the PQ operation range of the offshore converter station is calculated to determine whether the reactive power demand of the offshore converter station system is met. If not, the valve-side voltage value of the offshore converter station connection transformer is adjusted. In specific implementation, according to the input conditions of the AC system, the reactive power demand of the offshore converter station system to be met is -35MVar~﹢100MVar.

[0077] Based on the valve-side voltage of the land converter station connection transformer and the reactive power demand of the land converter station system, the PQ operation range of the land converter station is calculated and the tap position of the land converter station is designed. The reactive power demand of the land converter station system to be met is -310MVar~+310MVar. After calculation, the reactive power demand of the land converter station system can be met when the design tap position is -4~+2. If the reactive power support capacity of the flexible DC system is weak, it can be further optimized by adjusting the valve-side voltage of the converter station connection transformer until the actual demand is met.

[0078] The valve-side voltage of the connecting transformer is continuously adjusted until the reactive power requirements of the offshore converter station system and the onshore converter station system are met at the same time. In specific implementation, when the valve-side voltage of the connecting transformer is 325kV, the system response characteristics are better, and the reactive power requirements of the system can be met when the tap position is -3~+3.

[0079] Finally, the insulation coordination parameters are designed based on the various parameters obtained after meeting the requirements, and the volume and weight of the offshore platform are calculated based on the designed insulation coordination parameters. According to the calculation results, if the engineering design requirements of the offshore platform cannot be met (such as the high insulation level requirements of the offshore platform and the heavy weight of the offshore platform), the upper limit of the modulation ratio will be reduced (such as from 0.95 to 0.92), and the design steps will be repeated until the design requirements are met. Finally, in an embodiment of the present invention, when the valve side voltage of the connecting transformer is 325kV and the tap position of the onshore AC station is -4~+4, the reactive power requirements of the sea and land converter station systems can be met at the same time.

[0080] In summary, the basic process of an offshore platform design method for flexible direct current transmission provided by an embodiment of the present invention has been explained, which clarifies the interaction between the valve-side voltage of the connecting transformer, the tap position, the PQ operating range of the DC system, insulation coordination, modulation ratio, etc., reduces the design iteration process of the offshore wind power flexible direct current system, and realizes the joint optimization design of the offshore wind power flexible direct current operating range and insulation coordination, thereby obtaining an offshore platform that meets the actual application needs.

[0081] On the basis of the above-mentioned method items, the present invention provides corresponding embodiments of the system items.

[0082] See also Figure 3 , Figure 3 The structure diagram of an offshore platform design system for flexible direct current power transmission provided by an embodiment of the present invention is as follows. The offshore platform design system for flexible direct current power transmission includes:

[0083] The voltage initial value design module 21 is used to design the initial value of the valve side voltage of the connecting transformer of the offshore converter station and the initial value of the valve side voltage of the connecting transformer of the onshore converter station;

[0084] A first operation interval calculation module 22, configured to calculate a PQ operation interval of the offshore converter station based on an initial value of a valve-side voltage of a connection transformer of the offshore converter station;

[0085] A second operation interval calculation module 23 is used to calculate the PQ operation interval of the onshore converter station under different tap positions based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station;

[0086] An operation range adjustment module 24, used to adjust the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively, until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement;

[0087] The insulation coordination parameter design module 25 is used to design the insulation coordination parameters based on the valve-side voltage value of the connecting transformer of the offshore converter station that meets the first preset requirement and the PQ operation range of the offshore converter station, and the valve-side voltage value of the connecting transformer of the onshore converter station that meets the second preset requirement and the PQ operation range of the onshore converter station;

[0088] The offshore platform design module 26 is used to calculate the volume and weight of the offshore platform according to the insulation coordination parameters.

[0089] In an optional embodiment, the voltage initial value design module 21 is specifically used to:

[0090] Based on the DC voltage and modulation ratio range, design the initial value of the valve-side voltage of the connecting transformer at the offshore converter station and the initial value of the valve-side voltage of the connecting transformer at the onshore converter station;

[0091] The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

[0092] In an optional embodiment, the operation interval adjustment module 24 is further used to:

[0093] When the PQ operation range of the offshore converter station cannot meet the first preset requirement, a tap is set for the connecting transformer of the offshore converter station.

[0094] In an optional embodiment, the offshore platform design module 26 is further used to:

[0095] When the volume and weight of the offshore platform cannot meet the third preset requirement, the modulation ratio transformation range is adjusted and the insulation matching parameters are redesigned until the volume and weight of the offshore platform meet the third preset requirement.

[0096] It should be noted that the offshore platform design system for flexible direct current power transmission provided in an embodiment of the present invention is used to execute all the process steps of the offshore platform design method for flexible direct current power transmission in the above embodiment, and the working principles and beneficial effects of the two correspond one to one, so they will not be repeated here.

[0097] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for designing an offshore platform for flexible direct current transmission, characterized in that: include: Design the initial value of the valve-side voltage of the connecting transformer at the offshore converter station and the initial value of the valve-side voltage of the connecting transformer at the onshore converter station; Based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station, the PQ operation range of the offshore converter station is calculated; Based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station, the PQ operation range of the onshore converter station under different tap positions is calculated; Adjusting the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement; Design insulation coordination parameters based on the valve-side voltage value of the connecting transformer of the offshore converter station that meets the first preset requirement and the PQ operation range of the offshore converter station, and the valve-side voltage value of the connecting transformer of the onshore converter station that meets the second preset requirement and the PQ operation range of the onshore converter station; The volume and weight of the offshore platform are calculated according to the insulation coordination parameters.

2. The offshore platform design method for flexible direct current power transmission according to claim 1, characterized in that: The design of the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station includes: Design the initial value of the valve-side voltage of the connecting transformers of the offshore converter station and the onshore converter station based on the DC voltage and modulation ratio range; The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

3. The offshore platform design method for flexible direct current power transmission according to claim 1, characterized in that: The calculating of the PQ operation range of the offshore converter station based on the initial value of the valve-side voltage of the connection transformer of the offshore converter station includes: Based on the initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the first initial condition, the PQ operation range of the offshore converter station is calculated; The PQ operation range of the offshore converter station includes the reactive power demand range of the offshore converter station system.

4. The offshore platform design method for flexible direct current power transmission according to claim 3, characterized in that: The first initial condition includes the modulation ratio variation range, the active power transmission capacity of the offshore flexible direct current transmission system and the capacity of the connecting transformer.

5. The offshore platform design method for flexible direct current power transmission according to claim 4, characterized in that: When the PQ operation range of the offshore converter station cannot meet the first preset requirement, a tap is set for the connecting transformer of the offshore converter station.

6. The offshore platform design method for flexible direct current power transmission according to claim 2, characterized in that: When the volume and weight of the offshore platform cannot meet the third preset requirement, the modulation ratio transformation range is adjusted and the insulation matching parameters are redesigned until the volume and weight of the offshore platform meet the third preset requirement.

7. The offshore platform design method for flexible direct current power transmission according to claim 2, characterized in that: The initial value of the valve-side voltage of the connecting transformer of the offshore converter station is the same as the initial value of the valve-side voltage of the connecting transformer of the onshore converter station.

8. The offshore platform design method for flexible direct current power transmission according to claim 7, characterized in that: The initial value of the valve-side voltage of the connecting transformer of the offshore converter station and the initial value of the valve-side voltage of the connecting transformer of the onshore converter station are both: ； Among them, the is the rated modulation ratio, is a DC voltage.

9. An offshore platform design system for flexible direct current transmission, characterized in that: include: The voltage initial value design module is used to design the initial value of the valve side voltage of the connecting transformer of the offshore converter station and the initial value of the valve side voltage of the connecting transformer of the onshore converter station; A first operation interval calculation module, used to calculate the PQ operation interval of the offshore converter station based on the initial value of the valve side voltage of the connecting transformer of the offshore converter station; The second operation interval calculation module is used to calculate the PQ operation interval of the onshore converter station under different tap positions based on the initial value of the valve-side voltage of the connecting transformer of the onshore converter station; An operation range adjustment module, used to adjust the valve-side voltage values ​​of the connecting transformers of the offshore converter station and the onshore converter station respectively, until the PQ operation range of the offshore converter station meets the first preset requirement and the PQ operation range of the onshore converter station meets the second preset requirement; An insulation coordination parameter design module, used to design insulation coordination parameters based on a connection transformer valve side voltage value of an offshore converter station that meets a first preset requirement and a PQ operation range of the offshore converter station, and a connection transformer valve side voltage value of an onshore converter station that meets a second preset requirement and a PQ operation range of the onshore converter station; The offshore platform design module is used to calculate the volume and weight of the offshore platform according to the insulation coordination parameters.

10. The offshore platform design system for flexible direct current transmission according to claim 9, characterized in that: The voltage initial value design module is specifically used for: Based on the DC voltage and modulation ratio range, design the initial value of the valve-side voltage of the connecting transformer at the offshore converter station and the initial value of the valve-side voltage of the connecting transformer at the onshore converter station; The DC voltage is determined by the topology, transmission capacity and device transmission capacity of the corresponding converter station system.

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