| Actively developing renewable energy represented by wind energy has far-reaching significance for alleviating the world’s energy crisis,improving the energy system structure,and protecting the ecology.Among them,offshore wind energy has the advantages of abundant resources,no land occupation,and the ability to be equipped with high-power wind turbines,and has gradually become a development trend and research hotspot.However,the complex marine environment brings challenges to the safe and efficient utilization of offshore wind turbines.On the one hand,the load-carrying characteristics of offshore wind turbines on different supporting platforms are different in different marine environments,which makes the response,parameters and goals of different types of wind turbines different during control,making it difficult to design a universal control scheme.On the other hand,the complex marine environment and multi-degree-of-freedom support platform greatly increase the operating conditions and extreme scenarios of offshore wind turbines,increasing the dimension and difficulty of unit control.Hence,it has important theoretical significance and engineering application value to analyze the main problems and requirements faced by different types of offshore turbines in complex environments,and to design and optimize controller in a targeted manner.This paper proposes an optimized control scheme for offshore wind turbines in complex marine environments.The corresponding control strategy is proposed and verified from two aspects:coordinated optimization control in the face of complex environmental loads and fault-tolerant control in case of unit failure.The main work of the paper includes the following points:1.Based on the environmental characteristics of offshore wind turbines,an environmental load model including wind,ice and waves is established.According to the similarities and differences between fixed and floating turbines in terms of structural characteristics and load-carrying characteristics,a model of offshore wind turbines in complex environments is established,including a common model,a fixed-bottom specific model,and a floating specific model.In order to evaluate the main fatigue damage of offshore wind turbines in a complex environment,the fatigue load model of the turbine is introduced.2.Based on the mathematical model of offshore wind turbines in complex environments,the characteristics of two types of offshore wind turbines are analyzed,including the closed-loop steady-state characteristics and open-loop dynamic characteristics of bottom-fixed wind turbines under wind-ice joint loads and floating wind turbines under wind-wave joint loads.Based on statistical methods,the operating characteristics and load characteristics of wind turbines are analyzed,and the quantitative changes in the performance of fixed wind turbines under different wind and ice scenarios and floating wind turbines under different wind and wave scenarios are obtained.3.For fixed wind turbines that are greatly affected by ice loads,the traditional control scheme is improved,the parameters of GSPI are optimized by using the parallel PSO algorithm,and the optimal parameters are fitted by SVR,and the ice load suppression control with optimal gain scheduling is constructed to effectively improve the dynamic performance of the system.A low-order control model of fixed wind turbines considering ice loads is introduced,and a power load optimization control strategy based on switching multi-model predictive controllers is proposed.This strategy redefines the operating conditions of fixed wind turbines under ice loads,and compared with the traditional strategy,this strategy can be optimized in real time according to the current operating status of the wind turbine and the wind and ice scenarios.4.A control-oriented physical model is proposed for floating wind turbines that are greatly affected by wind and wave loads.The model considers the flexible connection between the tower and the platform,the structure and load-carrying characteristics of the floating platform,and the coupling characteristics of the platform and the mooring system,and introduces the gap metric theory to analyze the nonlinearity of the system to reduce the order of the model.Compared with the high-order model,it is verified that the model can accurately predict the response of the unit under different wind and wave conditions.In order to meet the power and structural stability requirements of floating wind turbines,a power structure cooperative control strategy based on optimal gain scheduling multi-model predictive control is proposed.This strategy redefines the operating conditions of floating wind turbines under wave loads,and can perform wind and wave scenarios recognition and selection of semi-free operating point set.Compared with the improved traditional control method,it is proved that this strategy can reduce the fluctuation of power and reduce the fatigue load of the tower-platform structure.5.The complex marine environment will increase the operating frequency of actuators,thereby increasing the rate of fault.Aiming at the actuator failure problems encountered by both fixed bottom and floating turbine,a fault-tolerant control based on adaptive switching sliding mode control strategy is proposed..The strategy includes the design of full-order observer,adaptive law and constrained switching law.Through the dynamic identification of the tower-platform structure,a general control model of offshore wind turbines with actuator faults is established and applied in In this fault tolerance strategy.The model can accurately predict the power and structural dynamics of the wind turbine under different scenarios,and the average dwell time technique is applied to ensure the stability of the control system when the model is switched.In the scenario of three types of faults,the proposed fault-tolerant control strategy can enable the offshore wind turbine to quickly respond to actuator faults,give actuator compensation commands,and improve the dynamic performance of the wind turbine. |
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