Alternating current and direct current topology scheme design method suitable for offshore wind power output grid-connected scene

Abstract

The invention relates to an AC / DC topology scheme design method suitable for an offshore wind power transmission grid-connected scene, and the method comprises the steps: generating all possible topology schemes according to the demands of an offshore wind power transmission project; then, by taking the three typical offshore wind power delivery topology schemes as a reference, dividing the topology schemes into three technical routes, setting corresponding discrimination conditions, and eliminating the topology schemes lacking technical feasibility by using the discrimination conditions; for the topology scheme with technical feasibility, designing components in the topology according to the technical route to which the topology scheme belongs, and forming a plurality of rough technical schemes; respectively carrying out a longitudinal economical efficiency optimization process on each rough technical scheme to form a plurality of optimization schemes; and finally, transverse economical efficiency optimization is carried out on each optimization scheme, and the total cost of all optimization schemes is compared. According to the method, the technical characteristics, applicability and economy of various topology schemes are comprehensively considered, and the design process of the offshore wind power sending scheme can be standardized.

Description

Technical Field

[0001] The present invention relates to an AC / DC topology design method suitable for offshore wind power transmission and grid connection scenarios, and to the technical field of power system transmission and distribution. Background Art

[0002] With the gradual depletion of fossil energy and increasing environmental pressure, China and other countries in the world have begun to adjust their energy structure and develop large-scale clean energy. As an important part of my country's current new energy development and construction plan, a large number of offshore wind farm projects have been started or put into operation, and a larger number of larger offshore wind farm projects are under planning. With the continuous development of offshore wind energy resources, the planned capacity of offshore wind power is expanding, and the construction demand for offshore wind power transmission and grid-connected projects is expanding accordingly. In addition, the various actual scenarios faced by the project are becoming more diverse and complex. The single offshore wind power transmission topology can no longer meet the needs of existing projects.

[0003] In the actual large-scale offshore wind power transmission project planning process, there are many technical indicators to consider, the engineering conditions and construction environment involved are complex, and the planning and construction of the transmission network topology of the project often need to be comprehensively designed in combination with multiple factors such as technical characteristics, economy and actual engineering conditions. However, in the current actual offshore wind power transmission project design, due to the limitations of design technology, time and energy, the technical applicability and economy of various topological solutions are often not comprehensively considered, so that the final topological solution is not the optimal solution. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a topology scheme design method which comprehensively considers the technical characteristics, applicability and economy of various topology schemes.

[0005] In order to achieve the above object, the technical solution proposed in the present invention is: a method for designing an AC / DC topology solution suitable for offshore wind power transmission and grid connection scenarios, comprising the following steps:

[0006] Step 1: Generate all possible topology solutions according to the requirements of offshore wind power transmission projects;

[0007] Step 2: Based on three typical offshore wind power transmission topology solutions, all topology solutions are divided into three technical routes. Based on the technical characteristics of the three typical topology solutions, corresponding discrimination conditions are set. The topology solutions that lack technical feasibility are eliminated using the discrimination conditions to form a topology solution with technical feasibility.

[0008] Step 3: For the topological solutions that are technically feasible, design the components in the topology according to the corresponding technical routes to form several rough technical solutions that are all technically feasible;

[0009] Step 4: Carry out a longitudinal economic optimization process for each rough technical solution, adjust the design indicators related to economic efficiency, so as to achieve the optimal economic efficiency within the framework of this solution, and form several optimal solutions;

[0010] Step 5: Perform horizontal economic optimization for each preferred option, compare the total cost of all preferred options, and determine several optimal alternative options from the remaining options as needed.

[0011] The further design of the above technical solution is as follows: in the step 2, three typical offshore wind power transmission topology solutions are HVDC technical route, LFAC technical route and HVAC technical route.

[0012] In step 2, the criteria for determining the HVDC technical route is whether the conditions for the construction of the converter station are met. If not, it lacks technical feasibility. The criteria for determining the LFAC technical route is whether there are low-frequency fans and whether there are conditions for the construction of the frequency conversion station. If either is not met, it lacks technical feasibility. The criteria for determining the HVAC technical route is whether there is asynchronous interconnection and whether there are conditions for reactive power compensation. If there is asynchronous interconnection or there are no conditions for reactive power compensation, it lacks technical feasibility.

[0013] In step 3, the HVDC technology route designs the converter and main connection mode in the topology. The LFAC technology route designs the inverter solution in the topology. The HVAC technology route designs the reactive power compensation configuration in the topology.

[0014] In step 4, the vertical economic optimization process is as follows: adjust and select design indicators including voltage level, transmission frequency and system equipment; calculate the total cost of the solution; determine whether the total cost is the lowest cost within the solution framework, if so, the optimization ends, otherwise continue to adjust and select the design indicators.

[0015] In the first step, all possible topological solutions are initially screened based on the transmission capacity and transmission distance of the offshore wind power transmission project.

[0016] The beneficial effects of the present invention are:

[0017] The design method provided by the present invention covers the entire process from design to optimization of AC and DC topologies in offshore wind power transmission and grid-connected projects, and provides a relatively standardized and scientific process for the design and optimization of offshore wind power AC and DC transmission topologies, which effectively saves engineering design time, improves the design efficiency and rationality of the project, and helps to provide design references for a series of offshore wind power transmission projects with more complex application scenarios in the future.

[0018] The method of the present invention is based on an economic evaluation model. By introducing two longitudinal and lateral economic optimizations in the process, it is ensured that the optimized topology scheme is not only technically feasible but also economically optimal, which is conducive to further improving the economic benefits of offshore wind power transmission and grid-connected projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall process of the design method of the present invention;

[0020] Figure 2 It is a schematic flow diagram of the longitudinal economic optimization method of the present invention;

[0021] Figure 3 It is a schematic diagram of an offshore wind power transmission and grid-connected engineering system using an HVDC solution provided by an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram of an offshore wind power transmission and grid-connected engineering system using a LFAC solution provided by an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of an offshore wind power transmission and grid-connected engineering system using an HVAC solution provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Embodiment 1

[0026] like Figure 1 As shown, it is a schematic diagram of the overall process of an AC / DC topology design method applicable to offshore wind power transmission and grid connection scenarios provided in this embodiment, which includes the following steps:

[0027] Step 1: Generate all possible topological solutions according to the needs of offshore wind power transmission projects. Before entering the formal solution design and optimization process, the topological solutions can be initially screened based on the estimated transmission capacity, transmission distance and other requirements of the project according to the results of the previous project investigation, so as to reduce the number of solutions to be designed and optimized in the subsequent process, simplify the process steps and design time.

[0028] Step 2: Taking three typical offshore wind power transmission topology solutions as the main benchmark, all topology solutions are divided into three technical routes. Based on their respective basic technical characteristics, by setting corresponding discrimination conditions, each type of topology solution is judged to be suitable for the topology design of the current transmission project, and the solutions that lack technical feasibility are excluded to form a topology solution with technical feasibility. The three typical offshore wind power transmission topology solutions are HVDC technical route, LFAC technical route and HVAC technical route.

[0029] Step 3: After selecting a technical route that is technically feasible, design the components in the topology according to the technical route, thereby initially forming several rough technical solutions that are all technically feasible.

[0030] Step 4: Carry out a vertical economic optimization process for each rough technical solution, adjust the design indicators related to economy, so as to achieve the optimal economy within the framework of this solution and form several optimal solutions.

[0031] Step 5: Perform horizontal economic optimization on each preferred solution, compare the total cost of all preferred solutions, obtain the most economically optimal solution, and determine several optimal alternative solutions from the remaining solutions as needed.

[0032] The method of this embodiment is based on multiple engineering application scenarios, comprehensively considering the technical characteristics, applicability and economy of various topological solutions, and is helpful to standardize the design process of offshore wind power transmission solutions.

[0033] Embodiment 2

[0034] This embodiment is further designed based on the first embodiment. Figure 1 As shown in the figure: In step 2, the criteria for determining the HVDC technical route is whether the conditions for the construction of the converter station are met. If not, it lacks technical feasibility. The criteria for determining the LFAC technical route is whether there are low-frequency fans and whether there are conditions for the construction of the frequency conversion station. If either is not met, it lacks technical feasibility. The criteria for determining the HVAC technical route is whether there is asynchronous interconnection and whether there are conditions for reactive power compensation. If there is asynchronous interconnection or there are no conditions for reactive power compensation, it lacks technical feasibility.

[0035] In step 3, the HVDC technology route designs the converter and main wiring method in the topology. The converter solution can include multiple sub-converters, including but not limited to modular multilevel converters (MMC), thyristor phase-controlled converters (LCC), diode rectifier units (DRU) and their combinations.

[0036] The LFAC technology route designs the inverter solution in the topology. The HVAC technology route designs the capacity and assembly location of the reactive power compensation configuration in the topology.

[0037] Embodiment 3

[0038] This embodiment is further designed based on the first embodiment. Figure 2 As shown: a schematic flow chart of the longitudinal economic optimization method of this embodiment, comprising the following steps:

[0039] (1) Select the voltage level used by the system in the solution. The DC voltage of the system needs to be selected in the HVDC solution, and the AC voltage of the system needs to be selected in the HVAC solution and LFAC solution. The selection of system voltage will affect the operating loss and equipment selection in the system solution, further affecting the overall economic efficiency of the solution.

[0040] (2) Select the transmission frequency of the system in the solution. The transmission frequency in the HVDC solution is fixed at 0 Hz, and in the HVAC solution it is fixed at 50 Hz, so this step is not necessary. In the LFAC solution, the transmission frequency generally has two options: 50 / 3 Hz or 20 Hz. The transmission frequency will affect the transmission loss and the selection of equipment such as submarine cables and transformers, which will have a significant impact on the economic efficiency of the solution.

[0041] (3) Select the equipment used in the system in the solution. The scope of equipment includes but is not limited to transformers, submarine cables, compensation devices, and corresponding substations, offshore platforms and other supporting facilities. The selection of equipment must meet the engineering standards, some indicators must have a certain margin, and cost considerations must also be taken into account.

[0042] (4) Calculate the total cost of the scheme. The cost includes but is not limited to construction investment cost, operation and maintenance cost, loss cost and final scrapping cost. Within the scope of the scheme framework, the cost can be further reduced by continuously changing the above detailed design, and finally forming the optimal scheme with the best economic efficiency in the scheme framework.

[0043] (5) Determine whether the total cost is the lowest cost within the solution framework. If so, the optimization process ends. Otherwise, continue to return to step (1) to adjust and select the design indicators.

[0044] Application Examples

[0045] Figure 3This is a schematic diagram of the system topology of an offshore wind power transmission and grid-connected solution using the HVDC technology provided by an embodiment of the present invention. In this topology, the electric energy of the offshore wind farm is first collected using a 66kV submarine cable, and after being boosted by the offshore booster station, the electric energy is converted from AC to DC through the offshore converter station, and then transmitted to the onshore converter station via a ±500kV DC submarine cable. The electric energy is converted from DC to AC at the onshore converter station and then input into the onshore power grid. As mentioned above, the project in this example has the conditions for the construction of converter stations both at sea and on land. Therefore, in accordance with Figure 1 The process shown can determine the applicability of the HVDC technology route, and design the converter and main wiring scheme, etc., to complete the general design of the scheme; according to Figure 2 The process shown can determine the most economical system voltage and equipment model and complete the detailed design of the solution.

[0046] Figure 4 This is a schematic diagram of the system topology of an offshore wind power transmission and grid-connected solution using the LFAC technology provided by an embodiment of the present invention. In this topology, the electric energy of each low-frequency wind turbine in the offshore wind farm is first collected by a 66kV low-frequency AC submarine cable, boosted to 220kV by an offshore booster station, and then sent out by a 220kV low-frequency AC submarine cable. After being sent to the onshore BTB frequency conversion station, the low-frequency AC is converted into industrial frequency AC, and finally input into the onshore power grid. As mentioned above, the wind farms in this example are all low-frequency wind turbines and have the conditions for building a frequency conversion station. Therefore, in accordance with Figure 1 The process shown can determine the applicability of the LFAC technology route, design the inverter, and complete the general design of the solution; Figure 2 The process shown can determine the most economical system voltage, transmission frequency and equipment model, and complete the detailed design of the solution.

[0047] Figure 5 This is a schematic diagram of the system topology of an offshore wind power transmission and grid-connected solution using the HVAC technology provided by an embodiment of the present invention. In this topology, the electric energy of the offshore wind farm is first collected using a 35kV submarine cable, then boosted to 220kV via an offshore substation, and then transmitted to a land transformer station via a 220kV AC submarine cable, and then connected to the land power grid. As mentioned above, the project in this example has no asynchronous interconnection requirements, and there are conditions for configuring a reactive power compensation device at the end of the submarine cable. Therefore, in accordance with Figure 1 The process shown can determine the applicability of the HVAC technology route, design the reactive power compensation configuration plan, and complete the general design of the plan; according to Figure 2 The process shown can determine the most economical system voltage and equipment model and complete the detailed design of the solution.

[0048] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0049] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0050] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0051] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A method for designing an AC / DC topology scheme suitable for offshore wind power transmission and grid connection scenarios, characterized in that: The steps include: Step 1: Generate all possible topology solutions according to the requirements of offshore wind power transmission projects; Step 2: Based on three typical offshore wind power transmission topology solutions, all topology solutions are divided into three technical routes. Based on the technical characteristics of the three typical topology solutions, corresponding discrimination conditions are set. The topology solutions that lack technical feasibility are eliminated using the discrimination conditions to form a topology solution with technical feasibility. Step 3: For the topological solutions that are technically feasible, design the components in the topology according to the corresponding technical routes to form several rough technical solutions that are all technically feasible; Step 4: Carry out a longitudinal economic optimization process for each rough technical solution, adjust the design indicators related to economic efficiency, so as to achieve the optimal economic efficiency within the framework of this solution, and form several optimal solutions; Step 5: Perform horizontal economic optimization for each preferred option, compare the total cost of all preferred options, and determine several optimal alternative options from the remaining options as needed.

2. The AC / DC topology design method for offshore wind power transmission and grid connection according to claim 1 is characterized by: In the step 2, three typical offshore wind power transmission topology solutions are HVDC technology route, LFAC technology route and HVAC technology route.

3. The AC / DC topology design method for offshore wind power transmission and grid connection scenario according to claim 2 is characterized by: In step 2, the criterion for determining the HVDC technical route is whether the conditions for converter station construction are met. If not, it lacks technical feasibility.

4. The AC / DC topology design method for offshore wind power transmission and grid connection scenario according to claim 3 is characterized by: In step 2, the LFAC technical route is determined by whether there are low-frequency fans and whether there are conditions for building a frequency conversion station. If either is not the case, the technical feasibility is lacking.

5. The AC / DC topology design method for offshore wind power transmission and grid connection scenario according to claim 4 is characterized by: In the step 2, the judgment conditions of the HVAC technical route are whether there is asynchronous interconnection and whether there are reactive power compensation conditions. If there is asynchronous interconnection or there are no reactive power compensation conditions, it lacks technical feasibility.

6. The AC / DC topology design method for offshore wind power transmission and grid connection according to claim 5 is characterized by: In step three, the HVDC technology route designs the converter and main connection method in the topology.

7. The AC / DC topology design method for offshore wind power transmission and grid connection according to claim 6, characterized in that: In step three, the LFAC technical route designs the inverter solution in the topology.

8. The AC / DC topology design method for offshore wind power transmission and grid connection scenario according to claim 7 is characterized by: In step three, the HVAC technical route designs the reactive power compensation configuration in the topology.

9. The AC / DC topology design method for offshore wind power transmission and grid connection scenario according to claim 8, characterized in that: In step 4, the longitudinal economic optimization process is: Adjust and select design parameters including voltage level, transmission frequency and system equipment; Calculate the total cost of the program; Determine whether the total cost is the lowest within the solution framework. If so, the optimization ends; otherwise, continue to adjust and select the design indicators.

10. The method for designing an AC / DC topology scheme suitable for offshore wind power transmission and grid connection according to any one of claims 1 to 9, characterized in that: In the step 1, all possible topology solutions are initially screened based on the transmission capacity and transmission distance of the offshore wind power transmission project.

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