Research On Wind Farm Active Power Increasing Control Strategies Considering Wake Effects And Electrical Loss

Wind power generation is an important way to deal with the enviromental polution and energy crisis.Grouping wind turbines into clusters or wind farms helps to reduce land use,reduce installation and mainteinance cost and make it easier to manage.However,such large scale wind farms or clusters can cause aerodynamic interactions between the turbines,which will decrease the overall captured power and increase the loading on the downwind wind turbines.The aerodynamic interation is caused by wake effects,which is said will cause more than 10% energy loss to a wind farm.Therefore,reducing the wake effects by active wind farm control strategies has become a hot research topic.Apart from the energy loss caused by wake effects,the active power loss casued inside the electrical devices inside a wind farm is also considerable.Such loss is caused by the power flow inside the wind farm,thus it can be reduced by actively controling the power flow,which will in turn increase the output power.By considering the wake effects and electrical loss together,an optimized power dispatch strategy can be developed to reduce the energy loss cause by these two factors and improve the overall output power from the wind farm.This thesis mainly researches optimal power dispatch strategies of wind farms considering wake effects and electrical loss.The main work and innovations include:Firstly,in order to solve the energy loss problem caused by wake effects,an wake combination model that adapts to every wind directions and a wind trubine derating operation control strategy are proposed,based on which an optimal active power dispatch strategy for reducing wake loss based on optimization is proposed.The strategy is modeled by including the wake model and wind turbine model and the optimization models for power dispatch is sovled by particle swarm optimization algorithm,by which the optimal active power refereces are gotten.Comparing with traditional active power dispatch strategy,the proposed strategy can solve the wake loss problem and incrase the captured power by the wind farm.Secondly,in order to deal with the dynamic wind change and wake delay effect,a time-varing wind farm power prediction model is modelled by considering the dynamic wake model with wake delay.Then a nonlinear model predictive control algorithm is adopted to design the nonlinear model predictive controller for increasing wind farm power.This controller uses nonlinear prediction model and uses particle swarm optimization algorithm to optimize the fitness function and solves the control variables.Comparing with traditional stratgegy,the proposed strategy can perdict the wake effects and optimize the control variable before it happens,thus can increase the overall power in the wind farm.Thirdly,in order to deal with the electrical loss caused by energy flow,a wind turbine loss reducing strategy is proposed for the doubly fed generation system,which reduces the electrical loss of the system by optimal reactive power dispatch between generator side converter and grid side converter.Afterwards,a wind farm loss reducing dispatch strategy is proposed based on the wind turbine control strategy.The strategy is modeled by including the loss models of every electrical devices inside the wind farm and the optimization problem is solved by interior-point mothed.Comparing with traditional reactive power dispatch strategy,this strategy can reduce the total loss of the wind farm,cause it considers the losses in the wind turbine and the transmisstion cables.At last,aiming at decreasing the electrical loss and increasing the captured power,an coordinative and optimized active power and reactive power strategy considering the wake effects and electrical loss is proposed to deal with the interaction of active power and reactive power dispatch.This strategy coordinates not only the active power dipatch and reactive power dispatch but also the wake loss and electrical loss,which helps to increase the total output power of the wind farm.In order to validate the proposed control strategy,these strategies are tested in case studies with different operation conditions.The simulation results under different operating conditions show the effectiveness of the proposed strategies in the thesis.