Model Analysis And Transient Simulation Of DC Distributed Generation And Storage System

In the simulation of distributed generation system and micro-grid which contains numerous DG sources, power electronic devices and corresponding controllers, the most detailed and accurate models are not always necessary depending on the research objectives and scenarioes. Appropriate model simplification under reasonable assumptions could enhance the simulation speed while maintaining the accuracy, which has been widely applied in the modeling of DG sources and power electronic devices.This paper presents the model analysis and transient simulation of DC distributed generation and storage system, as well as the application of object-oriented design patterns in transient simulation of DG systems, with detail as followings:1)The paper addresses the modeling of DC distributed generation and storage system, including DC distributed sources and power electronic devices. The typical topologies and control strategies are also presented in this part.2)Taking solid oxide fuel cell (SOFC) as an example, the detailed dynamic model of SOFC and two simplified models which ignoring the change of gas partial pressure have been discussed in this paper. Three models have been applied in the simulation cases of SOFC based distributed generation system under different operation and fault conditions. Comparing the simulation results of the three models, the appropriate application range of these models is analized in the paper.3)An automatic piecewise linear fitting based model simplification method of complex nonlinear static characteristics of fuel cell is proposed in this paper. This method can automatically provide the piecewise linear fitting simplified model which fulfilling the scheduled error requirement and change the number of linear subsection by adjusting the error limitation, thus improve the simulation speed when ensuring the system simulation precision. It is also suitable for other distributed sources with nonlinear static characteristics. The validity of this method is proved by comparison and analysis of the detailed model and the simplified model.4)Taking the controllable inverter as an example, the detailed model, switch function model and average value model of power electronic devices are discussed. The three models are applied in the simulation cases of DC generation system under fault conditions. Comparing the simulation results of the three models, the appropriate application range of these models is presented in the paper.5)The paper describes the application of object-oriented design patterns in transient simulation of DG systems which is involved with actory method pattern, adapter pattern, strategy pattern and singleton pattern .6)Based on the proper distributed source models and typical control strategies, transient simulation of LV micro-grid with multiple DGs is accomplished to validate the effectiveness of the TSDG. The results of TSDG are compared with that obtained from Matlab/SimPowerSystems.