Dynamic Modeling Of Photovoltaic Grid-connected System

With the problem of energy crisis have become increasingly prominent and thefurther development of photovoltaic (PV) technology, photovoltaic grid-connectedsystem have been widely used to generate electricity in the world. Because of thedifference between convention power and photovoltaic power generation, the dynamiccharacteristics research of photovoltaic grid-connected system has been to be thecommon important topics in photovoltaic industry and power filed. It has the significantresearch values to establish the dynamic models of photovoltaic grid-connected system,which is the primary critical process. The main contents of this thesis are as following:①This paper has constructed two-stage type three-phase photovoltaicgrid-connected system small signal model, which is based on we could verify itsvalidity by eigenvalues method of the system. What’s more, it have calculated thesensitivity of the system control parameters and analyzed their impact on the systemsmall signal stability. And it gives influence on all eigenvalues of the system along withvarious parameters alteration, it could improve the small-disturbance stability of thesystem through reasonable selection system control parameters.②Due to the average state space model could not be used in case of a largedisturbance modeling which must be based on the "quasi-steady" hypothetical basis, thispaper introduce dynamic phase method to construction and analysis of photovoltaicgrid-connected system. According to the basic principle of dynamic phase method, ithas established the two-stage type dynamic phase model of photovoltaic grid-connectedsystem in balance state under three-phase stationary coordinate and two-phase rotatingcoordinate respective. Dynamic phase model of preceding stage Boost part、backwardstage inverter and control part have been included in it. Finally, through simulation toverify the correctness of the dynamic phasor model and draw a conclusion that dynamicphasor model has high simulation accuracy、fast simulation speed.③Dynamic phase method has been employed in three-phase photovoltaic invertermodel construction under asymmetrical situation and combined symmetricalcomponents method in order to build the dynamic phase model of three-phasephotovoltaic inverter under asymmetrical condition. The result of simulation andexperimentation show that the model has the capability of analyzing the PV invertertransient response characteristics under asymmetric operation situation, and significantly reduces the time required for the simulation.