Study On The Control Algorithms For Large Scale Wind Turbine

The research objective of this paper is to find a control method which can obtain maximum energy conversion efficiency for a complicated non-linear time-varyingsystem------variable speed wind energy conversion system(WECs). According to theenergy conversion characteristic of WECs, the maximum wind energy conversion efficiency can be obtained if the ratio of rotor speed and wind speed is kept at a constant, namely the rotor speed of wind turbine can be continuously adapted to the wind speed. For achieving the aim, two problems must be resolved. The first problem is how to control rotor speed in order to track stochastic wind speed. The second one is how to realize constant frequency output of generator under variable speed operation. The development of the technique of A.C Excitation for variable speed constant frequency(VSCF) supplies strong technique support for constant frequency output of generator under variable speed operation, which make it is possible that operation manner of large-sized grid-connected WECs changes from constant pitch constant speed to VSCF. But, so far, theory analysis and experimental study about the control technique of rotor speed tracking wind speed haven't been carried out in china.In this paper, basal operation principium and energy conversion characteristic of WECs are discussed in detail. Operation manner and control strategy of variable speed WECs is confirmed in theory, then a basal method for control rotational speed in order to track the wind turbine maximum power operation point are put forward. Research with PI control is implemented. The problem of wind speed measurement is resolved by using torque observer. The mathematic model of rotational speed control system is developed, and transfer function is deduced. Finally, correctness of the theory and validity of the method are validated through simulating and imitating.But theoretical optimal curve is tracked using PID control method has high limitation because of uncertainty of aerodynamic behaviour and complexity of electricity-electron model for a VSCF WECs. For these reasons, intelligentmeans------fuzzy logic control is developed on the basis of the above research.Control problem of tracking maximum power operation point is resolved by fuzzy logic. By similar method generator efficiency under variable speed operation is also improved. Through testing of simulating and imitating, the correctness of WTGS variable speed operation control strategy is further testified, at the same time, superiority of intelligent means is also testified. Those pave the way for developing new type of control system for VSCF WECs.Finally, the fault monitoring of key mechanical components of wind turbine based on observation is discussed, and the observers of the whole wind turbine and its key mechanical components through SVR model identification are established. The variable pitch semi-physical simulation experiments show that through observer the unit can be judged from failure, and failure source can be further comfirmed, so as to improve the control system and the reliability of unit operation.