Research On Distributed Generation Equivalent Modeling And Reactive Voltage Zoning Control

In recent years,with the increasingly serious problems of global energy shortage,environmental pollution and climate deterioration,accelerating the development and utilization of renewable energy has become the consensus of the international community,and vigorously developing renewable energy has become an important energy strategy in China.However,a large number of distributed generators have brought problems such as over-voltage and power fluctuation to the traditional power grid.In order to provide a theoretical basis for the grid-connected of distributed generators,it is necessary to study the characteristics of distributed generators.Moreover,the scale of the system is getting larger and larger.It is difficult and costly to deal with voltage over-limit coordination with reactive power equipment of the whole system.Therefore,it is necessary to study the solution of voltage over-limit in sub-region.This paper mainly studies the steady-state power flow model and steady-state equivalence method of direct-drive wind power generation system,small hydroelectric power generation system and micro-gas turbine system,the dynamic equivalence model and two-step clustering equivalence method of direct-drive wind farm,small hydroelectric power cluster and micro-gas turbine cluster,as well as the electromagnetic transient equivalence model and hierarchical clustering method of corresponding distributed generators.The method of reactive power and voltage partition and the scheme of dealing with voltage overshoot in the sub-region are discussed,and the above models and schemes are theoretically analyzed and simulated.Firstly,the steady-state characteristics of each distributed generation are analyzed.According to their characteristics and control modes,which are equivalent to PQ nodes or PV nodes respectively,the steady-state equivalence method of distributed generation cluster is proposed.The proposed steady-state model and equivalent method are verified by power flow calculation.Secondly,the dynamic equivalent modeling methods of direct-drive wind farm,small hydropower cluster and micro-gas turbine cluster are proposed.In order to solve the problem that the initial clustering centers of K-means clustering are not easy to select,a two-step clustering method is proposed to cluster distributed generators,and a dynamic equivalence method of distributed generators cluster is proposed.The dynamic equivalence modeling method of distributed generators cluster is verified and compared by simulation.Then,the electromagnetic transient equivalent modeling methods of direct-driven wind farm,small hydropower cluster and micro-gas turbine cluster are proposed.Similarly,the method of clustering equivalence before modeling is adopted,that is,first extracting the electromagnetic transient characteristics of each distributed power supply,then clustering the distributed power supply by hierarchical clustering analysis.The electromagnetic transient equivalence method of the distributed power supply cluster is proposed,and the proposed electromagnetic transient equivalence modeling method is verified by simulation and comparative analysis.Finally,a solution of voltage overrun in partition processing is proposed.Firstly,the method of forming electrical distance matrix including PV nodes and balanced nodes is proposed.The initial partition results are obtained by clustering only once,and then the partition results are optimized and adjusted according to the principle that each partition contains reactive power sources.Then the optimal capacitor configuration scheme and reactive power regulation scheme when the system voltage exceeds the limit are proposed.The effectiveness of this method is verified by an IEEE 30-node example system.