| The power system simulation is the main decision basis for power systemanalysis and planning. Accuracy of calculations is directly related to security andstabilit y of power system. Because the power system load has the characteristics ofrandomicit y, distributivit y and mult iformit y, the load modeling of the actual powersystem is very difficult. The current composite load modeling used in simulation isnot mature yet, particularly, the traditional load modeling will be changed withdistributed generation source(DGS) connected to the distribution network. Largenumbers of DGS have changed the traditional load composition and topology ofdistribution network, and bring a series of new theoretical methods and technicalproblems demanding prompt solution to power system analysis and operation control,one of them is the composite load modeling of distribution network consideringdistributed generation. Photovoltaic cell (PV) and fuel cell (FC) power generationhave many advantages, so the capacity of DC distributed power supply is increasing,and it has important theoretical and practical significance to study the modeling of PVand FC generation system.Firstly, the economy and environmental protection of the traditional power anddistributed generation are compared, the influence brought by distributed generationsources on power system is analyzed; this paper describes the principle of FCgenerating system, the mathemat ical model of each module and control strategy indetail, and then builds a complete FC power generation system based onMatlab/Simulink and analyzes its operating characteristics through the simulat ion.The analysis results of the steady and dynamic operating characteristics of FC showthat FC can be considered as a generalized dynamic load with negative powerconsumption. The second order differential equation of state description equivalentmodel was presented. The validity, generalization of this equivalent description modeland stabilit y of the parameters were testified by comparison of simulation modelingwith different disturbance levels.In order to study the composite load modelling of distribution network with PV,this paper describes the mathemat ical models of PV, and dual-loop control strategy fitfor photovoltaic cells is adopted to build a photovoltaic power generation system inMatlab/Simulink. As a typical DC distributed power, PV is influenced by environmental factors, there is a lot of power output at sunny day but there is littleeven no power output at night, so it is connected to power grid through the MPPT,DC/DC and DC/AC conversion control, besides, the battery module is also used torestrain the output fluctuations of PV power generation system. The constant powerstatic load model can be used to describe the characteristics of PV by the preliminaryanalysis of the steady state and dynamic operating characteristics of PV powergeneration system. Finally, the description of the equivalent model is verified. |
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