基于小信号模型的风电场同调等值理论

Coherency-Based Dynamic Equivalent Theory of Wind Farm Based on Small-Signal Model

同调等值是风电场动态等值的常用方法,该方法认为型号相同且运行状态相似的风电机组可对外表现出一致的动态特性、且其构成风电机群的整体动态输出特性可通过1台风电机组反映。基于小信号模型,探讨了上述等值方法的理论依据及成立条件。为此,首先建立了风电机群全阶线性化状态空间模型。然后,借鉴模式分析中模式分解的思路,推导了风电机群动态系统的等效解耦;基于所得结果,类比模式分析中模态、可控性及可观性的定义,探讨了风电机群内各风电机组可对外表现出一致的动态特性、且风电机群整体动态输出特性可通过一台机组反映的原因和成立条件。最后,通过仿真算例,验证了所提方法和结论的有效性。所提方法和结论可为风电场同调等值提供一定的理论依据,对于同调等值中风电场分群方法的研究具有一定的指导和借鉴意义。

Coherency-based dynamic equivalence is a commonly used method to establish the equivalent model of a wind farm,in which it is considered that a group of wind turbine generators(WTGs)of the same type and similar operating states could exhibit coherent dynamic performances to the external power system and its total dynamic output characteristics can be reflected via a single WTG.In this paper,theoretical basis and tenable conditions for this dynamic equivalent method is mainly studied based on small-signal model.Therefore,full-order linearized state-space model of a group of WTGs(GW)is established at first.Secondly,drawing on modal decomposition in modal analysis,the equivalent decomposition of a GW dynamic system is derived.Based on the results of the derivation,in analogy with mode shape,controllability and observability,reasons and tenable conditions which WTGs in a GW could exhibit coherent dynamics to the external AC grid and the complete dynamic performance of the GW can be reflected by a single WTGs are discussed.Finally,the proposed methods and conclusions are validated through study cases.The methods and conclusions provide theoretical basis for coherency-based dynamic equivalent of wind farm(CDEWF)and are of certain significance to be guidance or reference in researches on WTGs clustering in CDEWF.