Research On Analysis Method About Voltage Stability Of Micro-grid Basis On Small Disturbance

In view of the severe situation of fossil energy shortage and environmental pollution problem caused by traditional thermal power generation,micro-grid have been widely use as an important approach to consume the renewable energy sources.And people pay more and more attention to the research about micro-grid.However,the nondeterminacy of generation of renewable energy sources,the instability of power electronic switching devices,and the random changing of load,all of this will result in disadvantageous to reliable and stable operation of micro-grid,thus the problem of voltage fluctuation and stable are obvious.So,this thesis researching the analysis method of small signal voltage stability of photovoltaic micro grid have theoretical value and practical significance.Combining with the typical physical framework of photovoltaic micro grid,in this thesis the writer analyze the reason of voltage instability of photovoltaic micro grid in depth.The mathematic models of photovoltaic power generation system,supercapacitor accumulation system,storage battery accumulation system,load and induction motor have been established.And by gathering all above mathematic models,so form the whole system mathematic models of photovoltaic micro grid.Contrasting with the grid,in view of the simple structure,small-scale and the agminated parameter of micro-grid,simplizing the micro-grid's model,so the thesis come up with a analysis model used to describe voltage stability of micro-grid.This thesis utilizes the eigenvalue method to analyze the voltage stability of micro-grid.In order to get the stable operation parameter,this thesis classifies the node of distributed generation according to different control method of converter,combining with mathematic model in stable situation of converter,utilizing alternating current and direct current iteration method to count the load flow of micro-grid.By linearizing the mathematic model of system in the stable operation,getting analysis model of voltage stability when micro-grid happen small disturbance.Then the thesis analyzes and contrasts two ways of forming the state matrix in detail.Based on this,the thesis utilizes QR arithmetic to count the eigenvalue of state matrix.And then judge the voltage stability when micro-grid happen small disturbance according to the distribution of eigenvalue.Introducing example simulation,this thesis utilizes eigenvalue analysis method to analyze the ability of keeping voltage stable when micro-grid happen small disturbance.And then analyzing the effect of parameter of induction motor and droop control coefficient to the stability of micro-grid,so this thesis verify the accuracy and effectivity that using eigenvalue to analyze the stability of micro-grid.