Research On Wind Turbines In Wind Farm Of Active Power And Reactive Power Coordinated Optimization Dispatching

Because of the depletion of fossil resources worldwide and the environmental protection consciousness enhancement, the new energy power generation technology represented by wind power obtain the fast development in recent years. In 2014, wind power installed capacity and growth rate of wind power in China continues to the top of the world. However, the wind power delivery transmission line construction speed is still far behind the pace of growth of wind power installed capacity, so wind power curtailment will not be solved in the short term and become a common phenomenon. Therefore, we must consider wind power curtailment as long as we study on the effects of wind farm on power system, namely the active power order value from the dispatch center. At present, due to the unique advantages of the double-fed induction generator (DFIG), it becomes the mainstream wind power generator type in our country. The reactive power generated by large scale wind farm consists of DFIG or other type wind power generator is directly related to the voltage stability of point of common coupling (PCC). So, research of the reactive power regulation ability of wind farm has both important theoretical significance and real application value. This paper considers the active power order value from the dispatch center, studys on the input wind speed data processing of wind turbine, the dynamic equivalent model of wind farm, the relationship between the wind farm reactive power limit and active power dispatch plan, the active power and reactive power coordinated optimization dispatch plan. The main research contents and research results are as follows:(1) When wind speed data is abnormal or missing caused by the fault or damage of wind speed recorder, this paper uses linear regression model to calcuate the input wind speed of these wind turbines. The validity of the model is verified by wind speed data of an actual wind farm in Inner Mongolia. In order to get more stable input wind speed of a wind turbine, wavelet multiresolution analysis method is used in dispose the input wind speed sequence, only the low frequency component participate in subsequent modeling process. The validity of this method is verified by a wind farm model established on PSCAD platform. Processing and calculation of the wind speed can make the equivalent model of wind farm and power dispatching model more accurate.(2) This paper makes mathematical model of wind turbine derivation and makes power coefficient (Cp) as a classification index, a multi-machine dynamic equivalence model with DFIG is built, and the run time of this model is less. Classification index is easy to get and the model is more similar to actual operation situation. By establishing wind farm models on PSCAD platform, the results show that the proposed equivalent model can more accurately describe the output of the detailed model compared with the method using a classification index as rotor speed. The establishment of model laids a solid foundation for subsequent research of wind farm power dispatching model.(3) In order to reduce the operation cost and the switching on/off times of wind farm additional reactive power compensation device, make full use of the wind farm itself reactive poweer ability, this paper proposes a new wind turbines active power scheduling solution which makes it possible for the wind farm to generate the maximum reactive power. Based on the DFIG reactive power limit formula, derived theoretically the wind farm maximum reactive power limit of active power dispatching scheduling plan. The specific iterative algorithm is given for solving this plan. The effectiveness of the power allocation plan is verified in a case study. Bases on further study on the mathematical model of DFIG converters, control strategy of DFIG stator and rotor, for DFIG and squirrel-cage induction generator (SCIG) based wind farm, a kind of wind turbines active power dispatch model is proposed which makes it possible for the wind farm to generate the maximum inductive reactive power. By establishing dynamic equivalence wind farm model on PSCAD platform, the power dispatch model of DFIG and SCIG based wind farm is verified.(4) Based on the above of the maximum reactive power limit of DFIG wind farm, this paper proposes a kind of power dispatch optimization model which considers copper loss minimization of all DFIGs and maximization reactive power margin of every DFIG in wind farm. An active power and reactive power allocation optimization model is established. Then, the active power and the reactive power generated by wind farm can satisfy the power grid requirements of both active power and reactive power. By establishing dynamic equivalence DFIG based wind farm model proposed in this paper on PSCAD platform, the wind farm power coordinated optimized dispatching model is verified.