Research On Composite Load Modeling Considering Distributed Generation

The digital simulation of power systems works as a fundamental basis for decision making during operating analysis and planning design of power systems.Correctness of the simulation results directly relates to the safety and stability of power systems.However,as composite loads are normally random,scattered,time-varying and nonlinear,the load modeling faces at lot of difficulties as a result.This paper firstly states development and current status of the load modeling.Considering that proper load models and modeling methods are bases for research work,this paper then concludes in detail relevant model structures and modeling methods,introduces the parameter identification theory,and explains influences of load models on power systems.As connection of distributed power generation systems into power distribution networks will make load characteristics even more complicated,the wide access of distributed power generation in power grids will inevitably cause huge influences on characteristics of composite loads.This paper analyses the influences of distributed power generation on power grids,based on definition and classification of the distributed power generation,and establishes a simulation system of a distribution network with wind power generation and SOFC power generation,based on Matlab/Simulink.This paper studies the composite load modeling methods and relevant model structures of distribution networks with wind power generation,based on the simulation system established here.Also,this paper introduces in detail the mathematic models of distribution network composite loads,as well as those of wind turbine generator systems,and through inductive analysis of both kinds of models,it proposes that wind turbine generator systems with constant speed,frequency and fixed pitch should be equivalent to asynchronous generators,based on which a generalized composite load model applicable to conditions with all wind power output ratios is advanced.Power system simulation is conducted towards distribution networks with wind power generation,by using the measurement-based method and the intelligent optimization algorithm,to get load characteristic data.Effectiveness of the model is verified through modeling under conditions of three wind turbine outputs.In order to research composite load models of distribution networks with SOFC power generation,this paper conducts an in-depth study regarding operation mechanisms and control modes of distributed SOFC power generation systems,and establishes a simulation system with fuel cells.By analyzing transient characteristics of power generation system,it sets up an equivalent model of fuel cell,and proposes that the SOFC power generation can be considered as a power source with reactive power of zero,based on which a generalized composite load model for multiple distributed power generation systems is established.Effectiveness of the model is verified through relevant power system simulation.