Research On Reactive Power And Voltage Control Strategy Of Distributed Wind Power Generation

With the increasing of wind power penetration and the restriction of power grid transmission capacity,large-scale wind farm is faced with a serious wind abandoning phenomenon.Distributed wind power is on small-scale and can be absorbed into distribution network directly,without long-distance transmission.Because the structure of distribution network is relatively weak,the active power variation of wind power system will have a significant impact on the voltage of distribution network.However,the supporting facilities are deficient in distribution network.Therefore,it is necessary to develop reactive power adjustment ability of distributed wind power generation.In this paper,the problem is researched from three aspects: theoretical analysis,control strategy design and simulation verification.Firstly,a detailed mathematical model is established to analyze the generation principle and control strategy for doubly-fed wind power generation.Based on it,the reactive power limit and reactive power control strategy of doubly-fed wind power generation are further analyzed.Considering the effect of distributed wind power on the voltage of distribution network,the relationship between distributed wind power fluctuation and distribution network voltage is researched,as well as calculation method of voltage.Secondly,this paper improves the hierarchical control strategy and applies it in distribution wind power system.The node with the most serious voltage deviation is chosen as control point to calculate the reactive power reference.And the distribution of reactive power reference is divided into three layers which is consist with distribution among different nodes,different generators accessing to same node,grid-side converter and generator stator of doubly-fed wind power generation.Sensitivity is used in distribution among different nodes and react ive power capacity is used in distribution among generators accessing to same node.Considering the coordinated control strategy between other equipment and distributed wind power generation,this paper establishes a detailed mathematical model of the OLTC and analyzed the control principle of it.What's more,the coordinated control strategy is adopted to realize the corporation between wind generation and OLTC.Finally,a simulation model is set up in PSCAD.Simulation results show that the improved strategy is more suitable for distributed wind power system,making full use of the reactive power output capability of the multiple wind power generation and improving the distribution network voltage more effectively.The coordinated control between wind turbine and OLTC avoids the blindness of voltage regulation and enhances the power grid's resistance to voltage fluctuation.The control strategy proposed in this paper has a great significance to the research of reactive power control of distributed wind power generation system and can be optimized in practice.