| As a clean and pollution-free renewable energy,wind energy has been paid more attention today for the energy shortage.The development trend of the wind turbine is from the land to the sea.Compared with the onshore wind turbine,the offshore wind turbines suffer more environment loads,such as wind load,the wave and current loads.There are two main problems with offshore wind turbines,one is the cost and the other is safety and reliability.Thus the design target for offshore wind turbines is to ensure the stability of the wind turbines,at the same time,minimize the cost burden as much as possible.Therefore,reducing the fatigue and extreme loads of the critical components is the key to design offshore wind turbine,which is not only related to the stability of offshore wind turbine,but also have a great impact on the maintenance costs and the life times of the turbines.In order to reduce the load of the offshore wind turbines,the vibration problem of wind power system is studied in this paper.The research is based on an offshore permanent magnet synchronous generator and the passive based control theory.The vibration problems consist of the torsional vibration of the drivetrain,the tower vibration and the tower vibration under combined action of wind and waves.The main contents of this paper are as follows:Firstly,the control method of drivetrain torsional vibration based on PCH model is studied.The method is based on the passive control theory,and a PCH model which can reflect the physical structure characteristics of the system is established.Based on this PCH model,the controller with simple structure is designed,which not only suppresses the torsional vibration,but also improve the output power quality.Secondly,the suppression of tower vibration is studied.The tower vibration includes the fore-aft tower vibration and the side-side tower vibration.Based on the basis tower vibration model,the PCH model which reflects the physical structure characteristics of the tower is established.By using the energy function point and through the energy compensation of the system,a simple and easy passive controller is designed,the simulation results verify the effectiveness of the controller.Finally,the problem of tower vibration under the combination of wind and wave is studied.Based on the combination of the Active Disturbance Rejection Control(ADRC)and the passive control theory,a passive based controller with linear expansion state observer(LESO)for tower vibration is designed,and the proof method of estimated ability for a third order linear expansion state observer is proposed,the theoretical analysis and the simulation results prove the validity of the proposed control strategy. |
