An openfast-wecsim-based wind-wave integrated coupling calculation method

Abstract

This application discloses a wind-wave integrated coupled calculation method based on OpenFAST-WECSim, belonging to the field of marine energy utilization. Addressing the problem in existing technologies where "software generally cannot implement prismatic joint constraints or uses fenders instead, resulting in significant disputes in simulation results," this application implements coupled calculation between the wind turbine design software OpenFAST and the hydrodynamic calculation software WEC-sim, realizing relative heave constraints between the platform and its appendages, including: 1) WEC-Sim calculates the platform displacement x at the previous moment... WEC (t i‑1 ), speed v WEC (t i‑1 acceleration a) WEC (t i‑1 1) The acceleration of the platform in the previous moment is transmitted to OpenFAST; 2) OpenFAST converts the platform's acceleration in the previous moment into the platform's hydrodynamic and anchor load F in the previous moment. hydro (t i‑1 )+F moor (t i‑1 ) = Ma WEC (t i‑1 )-F aero (t i‑1 )-Mg;3) OpenFAST is based on the platform displacement x at the previous moment WEC (t i‑1 ), speed v WEC (t i‑1 ) and platform hydrodynamic load F hydro (t i‑1 Proceed through time to obtain the platform displacement x at the current moment. FAST (t i ) and velocity v FAST (t i 4) OpenFAST is based on the platform displacement x at the current moment. FAST (t i ) and velocity v FAST (t i Calculate the aerodynamic load F at the current moment. aero (t i ), and transmit it to WEC-sim; 5) WEC-Sim receives the current aerodynamic load F. aero (t i And perform coupled calculations.

Description

Technical Field

[0001] This invention relates to an integrated wind-wave coupled calculation method based on OpenFAST-WECSim, which belongs to the field of marine energy utilization. Background Technology

[0002] Currently, mainstream wind-wave integrated analysis software includes OpenFAST, an open-source computing software developed by the National Renewable Energy Laboratory (NREL), Bladed developed by Det Norske Veritas (DNV), and HAWC2 developed by the Technical University of Denmark (DTU).

[0003] In addition, some marine structure calculation software (such as AQWA from Ansys, Sesam from DNV, and OrcaFlex from Orcina) also have wind-wave coupling calculation capabilities, but their aerodynamic load calculation accuracy is slightly inferior to the aforementioned models. To address this, researchers have proposed software interaction and coupling strategies, including OpenFAST+OrcaFlex developed by NREL, Bladed+Sesam developed by DNV, and F2A (FAST+AQWA) developed by Yang Yang of the University of Ningbo (NBU). Such coupling software can fully leverage the advantages of OpenFAST / Bladed's accurate aerodynamic load calculation and OrcaFlex / Sesam / AQWA's accurate hydrodynamic and mooring load calculation, representing a common approach for solving multiphysics-multibody coupling problems.

[0004] The coupling calculation between software is mainly achieved through data exchange. The multiphysics-multibody coupling problem is mainly based on the bidirectional coupling achieved by the data interaction between various computing modules, which can be summarized into the following three ways: (1) It has a coupling module and multiple passive receiving modules, among which the hydrodynamic module is a passive receiving module that can obtain the motion state of the attached bodies. This strategy is represented by OpenFAST (see OpenFAST). Figure 1): The wind turbine motion state is transmitted from ElastDyn (multibody dynamics module) to AeroDyn (aerodynamic module) to calculate aerodynamic loads. The platform motion state is first transmitted from ElastDyn to SubDyn (constraint module), and then to HydroDyn (hydraulic module) and MoorDyn (mooring module) to calculate hydrodynamic loads and mooring loads respectively. Conversely, AeroDyn, HydroDyn, and MoorDyn transmit the load results back to ElastDyn for overall dynamic coupling calculation; (2) It has one coupling module and multiple passive receiving modules, of which the hydrodynamic module is a passive receiving module, but it cannot obtain the motion state of the attached body. This strategy is represented by OpenFAST-OrcaFlex: ElastDyn transmits the platform displacement and velocity to OrcaFlex. OrcaFlex calculates the hydrodynamic and mooring loads based on the platform motion and transmits them back to ElastDyn to achieve calculation coupling. OrcaFlex is only a passive receiving module and cannot know the motion state of the attached floating body. This coupling strategy is not suitable for calculating the FOWT-PAWEC model; (3) It has multiple coupling modules and multiple passive receiving modules, among which the hydrodynamic module is a coupling module and can obtain the motion state of the attached floating body. This strategy is represented by F2A (see Figure 2 AQWA only transmits platform displacement, velocity, and acceleration to FAST-ElastDyn. At the FAST end, platform motion is transmitted from ElastDyn to AeroDyn for calculating aerodynamic loads. Aerodynamic loads are then transmitted sequentially from AeroDyn to ElastDyn and AQWA, achieving a closed-loop calculation. In this strategy, both AQWA and ElastDyn are coupled modules. The motion coupling between the platform and its attached floating bodies is implemented in AQWA, ultimately reducing to platform motion and transmitting it to ElastDyn.

[0005] Motion constraints between the platform and its attached floats are a challenge for integrated design software. Articulated constraints are relatively mature, with software such as OpenFAST-SubDyn, Sesam-Simo, OrcaFlex, and AQWA commonly employing the FEM method to achieve the swing arm attachment between the attached floats and the generator set. However, for relative heave constraints (which can be simplified to a prismatic joint with only translational degrees of freedom), these software programs generally cannot implement prismatic joint constraints or use fenders instead, leading to significant controversy in simulation results. Summary of the Invention

[0006] To address the problem in existing technologies that "software generally cannot implement prismatic joint constraints or uses fenders instead, resulting in significant disputes over simulation results," this application proposes a wind-wave integrated coupling calculation method based on OpenFAST-WECSim. Based on OpenFAST and WEC-Sim, a wind-wave coupled numerical model is independently developed. The hydrodynamic calculation module HydroDyn and the constraint calculation module SubDyn in OpenFAST are replaced with WEC-Sim to achieve relative heave constraints between the platform and its appendages.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a wind-wave integrated coupled calculation method based on OpenFAST-WECSim, comprising the following steps:

[0008] 1) WEC-Sim will adjust the platform displacement x from the previous moment. WEC (t i-1 ), speed v WEC (t i-1 acceleration a) WEC (t i-1 ) is passed to OpenFAST;

[0009] 2) OpenFAST converts the platform acceleration of the previous moment into the unit load of the previous moment;

[0010] 3) OpenFAST uses the platform displacement x from the previous moment as a reference. WEC (t i-1 ), speed v WEC (t i-1 The platform displacement and velocity at the current moment are obtained by advancing the time of the platform load and the platform load.

[0011] 4) OpenFAST calculates the aerodynamic loads based on the platform displacement and velocity at the current moment and transmits them to WEC-Sim;

[0012] 5) WEC-Sim receives aerodynamic loads and performs coupled calculations.

[0013] The optimized wind-wave integrated coupled calculation method based on OpenFAST-WECSim described above revolves around the dynamic equations of a floating wind turbine, which are expressed as Ma = F. hydro +F aero +F moor ;

[0014] Where M is the platform mass, a is the platform acceleration, and F is the platform acceleration. hydro For hydrodynamic loads, F aer o represents aerodynamic load, Fmoor For anchorage load.

[0015] In the optimized wind-wave integrated coupling calculation method based on OpenFAST-WECSim, in step 2), the loads transmitted to the platform reference point in OpenFAST exclude aerodynamic loads and platform loads.

[0016] The optimized wind-wave integrated coupled calculation method based on OpenFAST-WECSim, as described above, uses WEC-Sim to calculate the hydrodynamic and mooring loads F. hydro (t i-1 )+F moor (t i-1 ),

[0017] Take Ma WEC (t i-1 )-F aero (t i-1 The Mg form is transferred to OpenFAST-ElastDyn.

[0018] The optimized wind-wave integrated coupled calculation method based on OpenFAST-WECSim described above, in step 3),

[0019] OpenFAST is based on the platform displacement x from the previous moment. WEC (t i-1 ), speed v WEC (t i-1 ) and platform load Ma WEC (t i-1 )-F aero (t i-1 )-Mg, obtaining the platform displacement x at the current moment within the framework of Kane's dynamic equations. FAST (t i ) and velocity v FAST (t i );

[0020] The Kane dynamic equations have input terms such as time t, displacement x, velocity v, and load F, and the output term is the acceleration a at the current moment.

[0021] In the optimized wind-wave integrated coupled calculation method based on OpenFAST-WECSim described above, in step 3), the platform load F hydro (t i )+F moor (t i The platform displacement and velocity are updated using a quadratic interpolation method, and the time progression is performed using the fourth-order Runge-Kutta algorithm.

[0022] The optimized wind-wave integrated coupled calculation method based on OpenFAST-WECSim described above, in step 4), calculates the platform displacement x at the current moment. WEC (t i ) and velocity v WEC (t i After that, OpenFAST-AeroDyn calculates the aerodynamic load F at the current moment. aero (t), and in ElastDyn, all loads on the upper part of the tower base are integrated to the tower base.

[0023] The optimized wind-wave integrated coupling calculation method based on OpenFAST-WECSim described above, in step 5), transfers the wind turbine load at the tower base to the platform's center of gravity and transmits it to WEC-Sim. Specifically,

[0024] Based on WEC-Sim, the fourth-order Runge-Kutta algorithm is used to advance the platform displacement and velocity over time. A quadratic interpolation function is added to WEC-Sim to obtain the extrapolated wind turbine load of the sub-time step.

[0025] WEC-Sim incorporates the current time-step aerodynamic load into the dynamic equations to achieve coupled calculations.

[0026] The beneficial effect of this application is that the coupling between OpenFAST and WEC-Sim is not achieved by directly specifying / overwriting the calculation results of one software to the state of the other software, but by performing bidirectional coupled calculation;

[0027] The coupling software relies on Simulink-Simscape and has richer constraint forms;

[0028] Compared to OpenFAST / OpenFAST-OrcaFlex / F2A, the developed software allows for easier implementation of real-time control strategies for the floating body. Attached Figure Description

[0029] Figure 1 Diagram of OpenFAST coupling strategy;

[0030] Figure 2 This is a diagram of the F2A coupling strategy;

[0031] Figure 3 The interaction logic diagram of the OpenFAST-WECSim module;

[0032] Figure 4 This is a quadratic extrapolation function of the aerodynamic load at the platform's center of gravity in WEC-Sim;

[0033] Figure 5The logic diagram of the OpenFAST-WECSim coupled algorithm is shown. Detailed Implementation

[0034] The technical features of the present invention will be further illustrated below with reference to specific embodiments.

[0035] This invention provides a wind-wave integrated coupled calculation method based on OpenFAST-WECSim. It independently develops a wind-wave coupled numerical model based on OpenFAST and WEC-Sim, replacing the hydrodynamic calculation module HydroDyn and the constraint calculation module SubDyn in OpenFAST with WEC-Sim to achieve relative heave constraints between the platform and its appendages. Figure 3 As shown. The basic interaction logic of the coupling software is as follows: WEC-Sim transmits the platform motion state to ElastDyn, and ElastDyn transmits the aerodynamic load back to WEC-Sim to achieve coupled calculation.

[0036] The coupling between OpenFAST and WEC-Sim revolves around the dynamic equations of a floating wind turbine:

[0037] Ma = F hydro +F aero +F moor

[0038] Where M is the platform mass, a is the platform acceleration, and F is the platform acceleration. hydro For hydrodynamic loads, F aero For aerodynamic loads, F moor For anchorage load.

[0039] OpenFAST and WEC-Sim employ the following four coupling strategies:

[0040] Strategy 1: OpenFAST transmits the current platform displacement and velocity to WEC-Sim, and WEC-Sim transmits the current time-step hydrodynamic load to OpenFAST.

[0041] Strategy 2: WEC-Sim transfers the previous platform displacement, velocity, and hydrodynamic loads to OpenFAST. OpenFAST then extrapolates and predicts, and transfers the current tower foundation load to WEC-Sim.

[0042] Strategy 3: WEC-Sim transmits the current platform displacement, velocity, and acceleration to OpenFAST, and OpenFAST transmits the current tower base load to WEC-Sim.

[0043] Strategy 4: WEC-Sim transfers the current platform displacement and velocity, along with previous hydrodynamic loads, to OpenFAST for extrapolation and prediction. OpenFAST, in turn, transfers the current time-step tower base load to WEC-Sim.

[0044] The wind-wave integrated coupled calculation method based on OpenFAST-WECSim in this application adopts the second coupling method, but the other three methods also have the possibility of implementation.

[0045] The wind-wave integrated coupling calculation method based on OpenFAST-WECSim proposed in this application has the following specific coupling steps:

[0046] 1) WEC-Sim will adjust the platform displacement x from the previous moment. WEC (t i-1 ), speed v WEC (t i-1 acceleration a) WEC (t i-1 ) is passed to OpenFAST;

[0047] 2) In OpenFAST, according to the dynamic equations, the platform acceleration of the previous moment is converted into the unit load of the previous moment.

[0048] F aero (t i-1 )+F hydro (t i-1 )+F moor (t i-1 ) = Ma WEC (t i-1 ).

[0049] Among them, the aerodynamic load F aero (t i-1 This has already been taken into account in OpenFAST. Loads transmitted to the platform reference point in OpenFAST should exclude aerodynamic loads.

[0050] F hydro (t i-1 )+F moor (t i-1 ) = Ma WEC (t i-1 )-F aero (t i-1 ).

[0051] In addition, the wind turbine, platform, and anchor chain loads are included in the aerodynamic, hydrodynamic, and mooring loads, respectively. However, since the platform load is considered again in OpenFAST-ElastDyn, it needs to be further excluded.

[0052] v = adt.

[0053] Finally, the hydrodynamic and mooring loads F calculated by WEC-Sim were... hydro (t i-1 )+F moor (t i-1 ) with Ma WEC (t i-1 )-F aero (t i-1 The )-Mg form is transferred to OpenFAST-ElastDyn;

[0054] 3) OpenFAST uses the platform displacement x from the previous moment as a reference. WEC (t i-1 ), speed v WEC (t i-1 ) and platform load Ma WEC (t i-1 )-F aero (t i-1 -Mg, within the framework of the Kane dynamics equations (the Kane dynamics equations in ElastDyn have input terms such as time t, displacement x, velocity v, and load F, and the output term is the current acceleration a), obtain the platform displacement x at the current moment. FAST (t i ) and velocity v FAST (t i Among them, the platform load F hydro (t i )+F moor (t i The platform displacement and velocity are updated through quadratic interpolation, and time advance is performed using the fourth-order Runge-Kutta algorithm (this step is combined with the OpenFAST algorithm for advancement, which is the key to the coupling strategy).

[0055] 4) Calculate the platform displacement x at the current moment. WEC (t i ) and velocity v WEC (t i After that, OpenFAST-AeroDyn calculates the aerodynamic load F at the current moment. aero (t), and in ElastDyn, all loads on the upper part of the tower base are integrated to the tower base.

[0056] 5) Transfer the wind turbine load at the tower base to the platform's center of gravity and then transmit it to WEC-Sim. Since WEC-Sim also uses the fourth-order Runge-Kutta algorithm for time-propagation of platform displacement and velocity, a quadratic extrapolation function needs to be added in WEC-Sim (see...). Figure 4 This is used to obtain the extrapolated fan load for the sub-time step. Finally, WEC-Sim incorporates the aerodynamic load of the current time step into the dynamic equations to achieve coupled calculation.

[0057] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A wind-wave integrated coupled calculation method based on OpenFAST-WECSim, characterized in that: Includes the following steps: 1) WEC-Sim will adjust the platform displacement from the previous moment. ,speed acceleration Passed to OpenFAST; 2) OpenFAST converts the platform acceleration of the previous moment into the platform's hydrodynamic and anchor loads of the previous moment. ; 3) OpenFAST is based on the platform displacement at the previous moment. ,speed Platform hydrodynamics and anchorage loads To advance the timeline and obtain the platform's displacement at the current moment. and speed ; 4) OpenFAST calculates aerodynamic loads based on the platform displacement and velocity at the current moment. And pass it to WEC-Sim; 5) WEC-Sim receives the current aerodynamic load. And perform coupled calculations; The coupling between OpenFAST and WEC-Sim revolves around the dynamic equations of a floating wind turbine, which are expressed as follows: ; in, For platform quality, For gravitational acceleration, The platform acceleration calculated by WEC-Sim in the previous moment, The previous moment was a hydrodynamic load, For the previous moment's aerodynamic load, The anchorage load at the previous moment; Platform hydrodynamic and mooring loads calculated by WEC-Sim ,by The format is passed to OpenFAST-ElastDyn; In step 3), OpenFAST based on the platform displacement at the previous moment ,speed Platform hydrodynamic and anchorage loads The platform displacement at the current moment is obtained within the framework of Kane's dynamic equations. and speed ; Kane's dynamic equations have time Displacement ,speed Load The input term is the acceleration at the current moment, and the output term is the acceleration at the current moment. ; In step 3), the platform hydrodynamic and anchorage loads The platform displacement and velocity are updated using a quadratic interpolation method, and the time progression is performed using a fourth-order Runge-Kutta algorithm. In step 5), the wind turbine load at the tower base is transferred to the platform's center of gravity and then transmitted to WEC-Sim, specifically as follows: Based on WEC-Sim, the fourth-order Runge-Kutta algorithm is used to advance the platform displacement and velocity over time. A quadratic interpolation function is added to WEC-Sim to obtain the extrapolated wind turbine load of the sub-time step. WEC-Sim incorporates the current time-step aerodynamic load into the dynamic equations to achieve coupled calculations.

2. The wind-wave integrated coupled calculation method based on OpenFAST-WECSim according to claim 1, characterized in that: In step 2), the loads transmitted to the platform reference point in OpenFAST exclude aerodynamic loads and platform weight.

3. The wind-wave integrated coupled calculation method based on OpenFAST-WECSim according to claim 1, characterized in that: In step 4), the platform displacement at the current moment is calculated. and speed Then, OpenFAST-AeroDyn calculates the aerodynamic load at the current moment. In ElastDyn, all loads on the upper part of the tower base are integrated to the tower base.

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