Research On Modeling And Simulation Of Grid-connected Converters In Renewable Energy Generation

Renewable energy connection to large-scale AC-DC hybrid power grid is one of latest topic in power system research.Converter model plays a basic role in the research of grid connection of renewable energy power generation,and is important to large-scale AC-DC hybrid power grid simulation.In order to realize the simulation of converters in largescale renewable system,so far a variety of models for converter simulation have been established to adapt to different applications.However,the existing models can not be fully applied to the efficient electromagnetic transient simulation of electric power system wherein large-scale renewable energy is connected to the grid.In this paper,the piecewise technique is applied to the generalized state space averaging(GSSA)model and the piecewise generalized state space averaging(P-GSSA)model of converters is derived.The P-GSSA model is based on classic averaging modeling method represented by the state space averaging method and the GSSA method.Several factors are considered in this paper such as the error estimation,the difficulty in model construction,the complexity of establishing high-order models,etc.The advantages and disadvantages of classic averaging models of converter are compared in this paper.The P-GSSA model is obtained from the time scale of modeling and simulation,and the realization ways and the physical significance of P-GSSA model are discussed in detail.The correctness of the P-GSSA model is verified through simulation under steady state conditions,unbalanced conditions and fault conditions.The model error and accuracy of the P-GSSA model are analyzed,which directly targets the state variables and the complex mathematical calculation and analysis can be avoided.The influence on the converter error analysis are discussed about factors such as the model segmentation,Fourier expansion order of state space variables and model operating conditions.The simulation results show that the model established in this paper accurately reflects the electromagnetic transient characteristics of the converter,which ensures the accuracy of the model and improves the simulation efficiency,and is suitable for the electromagnetic transient simulation of large-scale converters.Finally,the nonlinear dynamics cognition are carried out for the phenomena appearing in the converter model simulation.